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THE AM BULLETIN BOARD => QSO => Topic started by: steve_qix on December 13, 2009, 02:03:41 PM



Title: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: steve_qix on December 13, 2009, 02:03:41 PM
Hi !

For many years, back in singledom, I had some very LARGE (60 inches x 32 x 24) inch speakers (sub-woofers, really) situated in corners of my living room.   These speakers had excellent low frequency response (down to single digits), and were good and loud.... I had seperate amplifiers, located at the speakers themselves, low level crossovers, etc. etc.etc..everything homebuild.  Audio bliss prevailed.

Ok, fastforward - 2001 - I meet Sherrie.  Sherrie moves in, and unfortunately, she HATES the big (ugly) speakers, and after careful consideration, the speakers and not Sherrie are banished to the basement..... and there have been no audio frequencies below about 50 cycles reproduced in this house since (except through headphones).

So here is today... we have recently moved a bunch of furniture around and - low and behold, there is a perfect corner just WAITING for a nice big sub-woofer..... so long as it passes the muster with Blonde Central (which means it has to look good and not be overly obtrusive.. I think I can actually get something that sounds good.

I know there are some fine sub woofers out there.  I was looking at one made by SVS - claims to be fairly flat down to 10 Hz, with plenty of power.  The only downside of all this is cost.  My big speakers were relatively inexpensive to build.  These subs are BIG bucks.  Oh well  - the cost of providing a chick-friendly environment, I guess  :D

Any ideas? Suggestions? Experiences with good subs?  I'm all ears (as Ross Perot would say!).

Regards,

Steve




Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: DMOD on December 13, 2009, 02:27:26 PM
Hi Steve,

My recommendation is a JBL unit:

http://www.fullcompass.com/product/304273.html

Take your PDM circuit with a LF bandpass-pass filter, and maul it.  :D

Phil - AC0OB


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that i
Post by: nq5t on December 13, 2009, 02:46:33 PM
This is a very well regarded sub in the $700 price range, used by a number of people building "virtual" pipe organs, where solid well defined low end is essential.  Spec'd to 16Hz, but probably a bit less.  Spouse and/or girlfriend friendly size.

http://www.definitivetech.com/Products/products.aspx?path=Subwoofers&productid=SuperCube%20III

Grant/NQ5T


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: Pete, WA2CWA on December 13, 2009, 02:57:36 PM
These guys have a bunch:
http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=620&CFID=13800677&CFTOKEN=49677502

I bought the SUB-120 HT some time ago and have been very happy with it. Doesn't break the bank and meets my woofing needs.

(http://www.parts-express.com/images/item_standard/300-635_s.jpg)


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KC2IFR on December 13, 2009, 03:59:36 PM
Well.......big is better for subs IMHO.......
Trying to reduce the size of sub-woofer is like trying to use a short antenna on 160. U can make it work but it will be a compromise!

Now u folks know why Im single!!!!!!

Bill


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: N3WWL on December 13, 2009, 04:13:43 PM
well said, bill... :D


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WA3VJB on December 13, 2009, 04:22:49 PM
Now u folks know why Im single!!!!!!

Bill

Because big is better ?

OH wait.
I understand.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KC2IFR on December 13, 2009, 04:25:10 PM
Paul............
Great return post.........LOL..........

I deserved that!


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: steve_qix on December 13, 2009, 05:01:48 PM
I'm allowed about 30 inches in height and about the same depth and maybe 24 inches wide.  That seems a "big" size for a sub, but maybe not.  I definitely don't want to compromise the low end response.  If I can't get down to around 10Hz, I probably won't bother  ::)

Hopefully, this can be achieved!!!!  I'm going to check out the products mentioned in the replies so far.  THANKS  ;)

Regards,

Steve


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KC2IFR on December 13, 2009, 05:12:12 PM
Steve,
U are "allowed"......please explain......
Allowed by who???????     


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: flintstone mop on December 13, 2009, 06:50:24 PM
Steve
UNfortunately pretty  is going to mean $$$$..........we had a discussion here recently about Man Caves.
My wife got a kick out of that. Doesn't understand it all, but knows that is my area!!

Fred


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 13, 2009, 06:57:35 PM

Everything you know about subwoofers, Steve, is wrong!!

Check out the high Xmax woofers of today!

Parts Express has a good number of very high quality examples.

The "secret" Qt value is close to 4.0-4.5. With that Qt the "alignment" in the cabinet is "magic".
You want to download a basic (free) "box response" software and investigate the relationship between Qt, Fs and VAS vs. Vb WRT F3.

IF you use a corner, you will get significant LF lift, which is not entirely predictable, but is measurable. Be prepared for that.

These modern subs use high excursion and high power handling with optimized flux fields to get very excellent LF performance.  Expect to use a large high DF amp, in most cases. I would not opt for one of those "plate amps" myself.

Any commercial sub in a box that advertises "10hz" response is being somewhat optimistic, and it is unlikely that it will do that very loud, if at all. Typically the better ones use some sort of feedback from the cone to flatten the acoustic response.

I don't see any need to run in a corner unless you really need some LF boost, btw.

A 4th order LP active filter is a good idea. Marchand sells boards that you can easily modify to suit your needs and are inexpensive.

Depending on your home construction and WAF the ultimate solution is an Infinite Baffle configuration. That would use the floor, wall or ceiling as the baffle and the open space ("infinite") behind it. The advantage to that is that then the driver goes down all the way to Fs (free air resonance) rather than something higher when enclosed in a box, even a refrigerator sized one.

                               _-_-bear



Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: steve_qix on December 13, 2009, 08:12:07 PM

Depending on your home construction and WAF the ultimate solution is an Infinite Baffle configuration. That would use the floor, wall or ceiling as the baffle and the open space ("infinite") behind it. The advantage to that is that then the driver goes down all the way to Fs (free air resonance) rather than something higher when enclosed in a box, even a refrigerator sized one.

                               _-_-bear


Hi Bear,

Thanks for the info on the subs.  I'll check this stuff !!  As far as an Infinite baffle - I just can't do it - I can't cut a hole in the beautiful (and very expensive) hardwood floors that are in every room of the house  :P   I don't know why.  It doesn't make sense.  But so far, I just can't do it.  Maybe if Frank (GFZ) does it first in his new beach place  8)


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KC2IFR on December 13, 2009, 08:52:15 PM
This could go on for ever......
Keep this in mind.......for sub woofers make the enclosure as big as possible.......no if's and's or butt's.
There is NO free lunch...........


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that i
Post by: W1RKW on December 13, 2009, 09:06:08 PM
Velodyne. Haven't met a SW that can beat it.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: Opcom on December 13, 2009, 09:06:29 PM
Bear, you are saying I could cut holes in the floor of my pier and beam house put the subwoofer speaker there?


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KC2IFR on December 13, 2009, 09:07:55 PM
oh boy.........here we go........ ::)


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that i
Post by: K5UJ on December 13, 2009, 11:21:03 PM
single guy here reporting in from the man cave -- can't you just take ur homebrew woof woof woofers and throw a sheet over 'em?  In't dat okay?    Fasten it with clip leads.

more important question -- what's to hear at 50 hz and below?  sound that low just shakes stuff.  hope you got a house made of steel and concrete.   Boogie down man.

Rob


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: Pete, WA2CWA on December 14, 2009, 12:28:48 AM
I had a 12" downward firing sub-woofer for several years and it worked great. Unfortunately, every time there was a long duration low frequency blast, the pets would run out of the room. I guess they could feel the vibration in the floor as they laid there.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that i
Post by: Blaine N1GTU on December 14, 2009, 06:38:45 AM
steve,
buy yourself a new hi-def TV and build a room/mancave in the basement, set your subwoofers up down there and it can be your own little escape.
when she yells down the stairs for you just crank up the volume "WHAAAT I CAN HEAR YOU"
 ;D

guess i'm with Bill on this one...  ;)


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 14, 2009, 09:59:19 AM
Velodyne is a halfway decent commercial offering - it uses a form of feedback. With the advent of high Xmax and higher power handling speakers the design has improved, but not beause of any intrinsic engineering. I do't like downward firing subs for a variety of reasons.

Bill, yes, up to a point larger is better... ooops gotta go out more later.

Back...

Well another problem with the downward firing method is that the VC is pulled out the gap by gravity, and this gets worse over time, also the cone is high mass (making matters worse).

These days you can get surprisingly good LF performance from relatively small boxes due to the high power handling and extreme Xmax (not Xmas - Xmax = excursion) of today's drivers. So you can EQ a smaller box and get surprisingly good LF extension today, whereas some time back you'd have run out of output at LF.

Another nice idea is the EBS "Extended Bass Shelf" which uses a ported or PR design with the resonance of the port or PR set "too low", but EQ added to flatten the response down to that point - works well.

Steve, you can use a ceiling or wall too for the IB set up...

                        _-_-bear

Rob, 50hz isn't low enough. The low string on a standard electric bass is just above 40 Hz. Some players have electrics that go down to C below E, lower. Going flat to 35Hz is a pretty darn good design point, but there is an octave below that. What's down there? Pipe organs, big drums, Jurrasic Park sound track, Mickey Hart's percussion kit, and all sorts of neat things that make things sound big and heavy...

Patrick, yes an IB set up is a speaker in a floor wall or ceiling where the back end is "free air"  - facing outside is best, of course!  ;)    But keep in mind that the suspension of a standard speaker is designed to be vertical not facing down. So some care must be taken in the selection of a driver that faces up or down... the best choice would be something like an Eminence 15" pro woofer with a very LOW Fs, you can then ignore the VAS spec and only look at the Qt, which in a pro driver is low (ok for this application) and shove it in the floor or ceiling (up to an attic, for example - but keep the mouse and dust away with some window screening! That will give you flat response (or whatever the speaker does without EQ all the way down to the resonant frequency (Fs). So if you find a 15" high power pro driver with Fs = 23Hz it will go flat to 23Hz. Magique!





Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WA1GFZ on December 14, 2009, 11:59:29 AM
Crap, I just put flooring down in the corner of the living room so won't be drilling holes any time soon. I do hace a pvc pipe in the wall to run wires to the basement.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 14, 2009, 12:11:32 PM

Frank,

If ur skilled at the art of woodworking, one can cut the nice new floor and make a setup that will be pretty much invisible when not in use to the wife's eye.

Two ways that i see... one is to make what is essentially a "hatch", you can actually use one of those nice stainless or brass hatch pulls that they use on boats, and that hatch will cover the speaker. Of course UNDER the hatch you will need some sort of attractive grating so that no one stands on the speaker... but that seems do-able. The beauty of this idea is that it is covered when not playing, and you open it on those rare occasions that you do play it. In fact the thing doesn't even need to be removed, it is sufficient to merely open it to a 45 degree angle, even facing toward the wall (away) so that it remains "pretty" is fine.

Way two is to make the cover over the speaker, the hatch, still out of the same material as the floor, but make it more or less 50% open, so that it looks like maybe a type of through the floor slotted heat plenum. A router with an appropriate round-over bit to dress the slots would do that trick nicely...

Fitted professionallly it will look seamless.

                           _-_-bear


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KB2WIG on December 14, 2009, 12:38:00 PM
 "  buy yourself a new hi-def TV and build a room/mancave in the basement, set your subwoofers up down there and it can be your own little escape. "

Yeah, but, she'll come down and then get really loud...

Soundproofing is the next best thing?     A new topic....

klc


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on December 14, 2009, 12:58:24 PM
Steve,  Will you take something used?   I get about 5 or 6 Subs through here a year.  I have a few in the other room. I will look at the brands act.. I know I have one Velodyne somewhere.

I have owned about 30 types and I built my own.  My favorite is the paradigm 10 or 12.  From someone that owns or has owned just about every classic speaker there was..  I like the small black paradigm's.   I also have a collection of old JDL, real b and Os and Advents.

Here is a picture of a subwoofer I designed and built.   The material is not plexiglass.  Its a type of material used at the Seaworld aquariums.  Its LF lucite  Its natural resonance is low. 

The subwoofer itself is an Earthquake unit. I chose this 15 inch woofer because of its thiele small properties (http://en.wikipedia.org/wiki/Thiele/Small).  I read though book and manuals for 2 weeks before finging this unit. It had exactly what I was looking for.

The base of this unit is Granite.  We had a Tile/marble house near us.. I rode my bike down and talked to one of the marble Craftsment from italy.  He made it for me at a great price.  The bottom includes a cutout for the coil.

The Standoffs are also lucite also.  Hand cut.  I rented a Studio that had an anechoic chamber.  I did this afterhours and paid very little.  I played pink noise through the sub and then used a real time analyzer to record the output off the sub.  I came prepared with 7 different lengths of standoffs.  I decided on the length in the picture. 

I made several of these one summer.  I kept this one as it was the first and its flawed.  I overtightened some screws and made some hairline cracks. The edges on the box construction are not perfect either.  You have to inject the chemical in each seam with a seringe.  If you dont do this correctly, you might get a run or two.. :)

Did I mention I was 15 years old when I built this?  I did this as a summer project! I have kep this thing all these years.. Its not actualy in use now..  We had a transformer blow up in the hood and the Subwoofer amp never came on again.. The relay just clicks and thumps the speaker over and over.. I will have to fire it back up someday.. It ROCKS the entire house.

CLark



Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: flintstone mop on December 14, 2009, 01:47:25 PM

Depending on your home construction and WAF the ultimate solution is an Infinite Baffle configuration. That would use the floor, wall or ceiling as the baffle and the open space ("infinite") behind it. The advantage to that is that then the driver goes down all the way to Fs (free air resonance) rather than something higher when enclosed in a box, even a refrigerator sized one.

                               _-_-bear


Hi Bear,

Thanks for the info on the subs.  I'll check this stuff !!  As far as an Infinite baffle - I just can't do it - I can't cut a hole in the beautiful (and very expensive) hardwood floors that are in every room of the house  :P   I don't know why.  It doesn't make sense.  But so far, I just can't do it.  Maybe if Frank (GFZ) does it first in his new beach place  8)
CHECK THIS LINK::::::

http://www.othermag.org/brownnoise.php
Steve , do you listen to a lot of pipe organ music where the low end will get down down down??? I think it's FACT that notes under 30hz will loosen those types of muscles.

I have to quit typing....my post might get censored.

Fred


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: KD3CN on December 14, 2009, 02:31:56 PM

I like my Velodyne.  Had it for years.  Well built, no problems, sounds great, looks purty...   ;)

Karl


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: steve_qix on December 14, 2009, 11:11:52 PM
I'm looking at all of the specs.  This is one of the subs I have been considering.

It's made by SVS.  There are 3 configuration modes (user configurable) 20hz, 15hz and 10hz (and sealed).  In 10hz mode, the unit is pretty good down to 10hz, but you sacrifice about 3dB of SPL as opposed to 20hz mode.

(http://www.classeradio.com/svs_front.jpg)   (http://www.classeradio.com/svs_front1.jpg)

It's 20w x 27d x 22h and weighs 155 pounds (OUCH!).

This is the PB-13 Ultra.

Also checking others, but this one is definitely on the list.  Front firing, too! Any comments are certainly welcome and appreciated!


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 16, 2009, 03:06:25 PM


The port can only "play" at one frequency...

I'd try to listen to this thing before spending the $$ myself... might be great, dunno.

                  _-_-


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on December 16, 2009, 03:32:34 PM
 It depends on what main speakers you have.   For example, I use Paradigm phantoms for the mains so I need a front firing sub for smooth sound. The phantoms produce very little low end.

Its nice to be able to tune the unit with the ports.  I spent most of my life building boxes with and without ports. A sealed box is always better if you have the amplifier power.  The ports only add at or around the one Freq and that area is boosted.  This discolors the music.  If done well its ok.

When bying your sub,  Decond on a few key factors:

Self powered?
Home theater?
Classic music?
Rock or modern?

Home theater means buying a large powerfull sub thats going to shake the room and wow movie viewers.   Classical means a ported box and Rock or modern means a ported unit with lots of 30 to 40HZ.

One of the coolest in my opinion is the old Carver subs.  Super small.  Really small. Lots of low end and lots of power.  My cousin has one and just loves it for his theater.  Very pleased with the performance.

Ebay item  150397282637






Clark


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: K6JEK on December 16, 2009, 09:19:54 PM
...
I'd try to listen to this thing before spending the $$ myself... might be great, dunno.
                  _-_-
The owner of a high end audio store told me the other day "If it's a good subwoofer, you don't hear it."  That was after I asked if the monster Velodynes were on in addition to the KEF Reference 207/2's.  I didn't notice anything coming out of them.

At least I think they were Velodynes (two of them).  They looked like this:

http://www.velodyne.com/products/product.aspx?ID=3&sid=486d918d

They would not fit the bill at Steve's place nor at mine.

The KEFs.

http://www.kef.com/CA/Loudspeakers/Reference/207

I was listening to this very high end stuff just for fun after I gave up on the more modest speakers in the store.  I really didn't like the affordable stuff they had.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: steve_qix on December 17, 2009, 12:09:13 AM
At least I think they were Velodynes (two of them).  They looked like this:

http://www.velodyne.com/products/product.aspx?ID=3&sid=486d918d


Those Velodynes are real nice ! 


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 17, 2009, 09:51:04 AM


They all look good and the write-ups are all glowing.

Listen, your ears will tell the story.

Notice they claim 2 x 3kw amps (dual VC woofer)?

So, where do you plug this thing in??
What gauge is the line cord?

Also, the improved performance that is now available to almost all of these sub manufacturers is due to greatly improved heat/thermal handling of new designs, which means increased power handling. This coupled with high Xmax designs makes for much higher performance than 20 yrs back...

Fwiw, I would agree that if you don't hear the subs that is best. I'll go one past that, if you don't "hear" the speakers, then you've gotten somewhere.
 ;D

                      _-_-bear




Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: W1RKW on December 17, 2009, 04:30:47 PM
 a nice pair of B&W's would eliminate the need for a SW and produce a nice sound stage to boot.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on December 17, 2009, 04:38:31 PM
If you like B&W  :-[


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 18, 2009, 09:06:58 AM


No way will any B&W get down where QIX wants to go... dinosaur foot thuds...

             _-_-


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: VE3GZB on December 18, 2009, 10:48:09 PM

Any ideas? Suggestions? Experiences with good subs?  I'm all ears (as Ross Perot would say!).

Regards,

Steve


Mount them under the floor?


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: K6JEK on December 19, 2009, 08:06:06 PM
Now you guys have me wanting a sub-woofer.

Is it true that it can be placed almost anywhere like in the back of the room where there is space instead of in the front where there isn't?

The front L/R,  Carver Amazing III's, have  good low frequency response so I'd do a low crossover, assuming I can figure out how to set that.

Anyone try one of the wireless gizmos for feeding the sub?  Getting the wire to where I want the sub isn't going to be any fun.

We mostly listen to classical music but every now and then a dinosaur enters the room.  How will I know it's a dinosaur not just an elephant if I don't have a sub?



Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on December 19, 2009, 08:21:02 PM
The sub is going to perform best when loaded on a wall or better yet, A corner.  I move my subs all around the room until I am happy.  But "most" of the time, I like to have the sub up front in the Corner of the room. The Crossover is going to be set on your preference.  You will have to listen to the the same music over and over and adjust the cut off and sub level.  I dont like hearing a Sub.. I like it to Fill.

C


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 20, 2009, 08:12:10 PM

I'm going to disagree almost completely with the advice in the earlier post(s) on sub placement.

It is true that the LF output will be boosted whenever any speaker (sub or not) is placed at a room boundary - the floor, the wall + floor, or 2 walls + floor, that does not in an of itself provide any benefits beyond the LF boost effect.

Open space is "pi" space. Add a floor and you have pi/2 space, add wall and you have pi/4 and two walls gives pi/8. So reducing the area where energy can radiate produces a type of "boost" over open or anechoic response for frequencies where this has an effect - which is generally speaking more as you go lower in frequency (the room dimensions providing some limits and other effects).

When you move a sub close or to a boundary, or when it fires to the floor it is taking advantage or being effected by this phenomena. A sub that fires from a point at the corner of the walls and floor starts to look a lot like a conical horn, fwiw. Actually, it is.

The biggest problem is that in 99% of all cases, and  that being 100% of anything that is not purely digital in the xover, the xover in the sub causes a delay in time for the start of the energy sent to the sub. Even IF the sub's driver was front firing and in the same vertical plane as the main speakers, and you had stereo subs (one per channel - or one per speaker in the room) the output of the sub would still be delayed WRT the main speakers! This creates a phase offset that makes the SUB's energy appear to be "disembodied" somewhat from the rest of the soundfield (assuming you have a spatial soundfield).

In order to make the sub's energy appear in approximately the proper time WRT the main speakers it would have to be physically (or acoustically) in front of the main speakers... of course most set ups do not permit this.

So, while you can place a sub almost anywhere, and putting it to the rear of the room or in the corner will get you LF boost (which may be needed by some subwoofers), it does present some problems in terms of integration into a system that provides more than flat amplitude response and is intented to also present a reasonably good phase or time response...

Next time - the issue of one vs. two or more subs...

                           _-_-bear



Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: Pete, WA2CWA on December 20, 2009, 11:26:16 PM
Maybe some enterprising person could design a sub-woofer chair or some type of sitting area that incorporates the sub-woofer as an integral part. Combines the "pleasures" of hearing and feeling.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: W3RSW on December 21, 2009, 08:38:15 AM
Bear,

Minor point, but  a whole sphere, "360 volume (360 rotated through 360 for 3D)" is mathematically 2*PI space, where Pi radians = 180 degrees.

Add the floor or split the sphere in two and you have one Pi space.
Your corner is now reduced to Pi/16 space,  ;D

Audiophiles may have modified the definition.  I suppose we could even use true volumetric definitions for a spherical volume.... 4/3 Pi*r^3

For all,
In a bass reflex, or ported closed space you not only have the fundamental freq. that's "tuned", but you have the overtones, diminishing each octave.  That's why double tuned ports or double resonance load line cavities such as in the Bose(tm) can have overlapping and algebraically superimposed blending that sounds well with what looks like a very simple set of holes and /or resonance columns.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 21, 2009, 09:11:06 AM


Ya, mentally challenged lately... sphere is 2pi... geez... have pity on the mentally challenged - we look and sound normal, but we're not...  ??? :-X


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: W3RSW on December 21, 2009, 12:57:33 PM
I h'ain't normal neither. 
Now I wonder if PI rotationally into 3D isn't a 4*PI space?
Oh well...
-probably just a confusion of terms in vector phase space?  ..urk,
 ;D


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: W1RKW on December 21, 2009, 05:03:31 PM
Maybe some enterprising person could design a sub-woofer chair or some type of sitting area that incorporates the sub-woofer as an integral part. Combines the "pleasures" of hearing and feeling.

Actually, they do exist in the home theater realm.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on December 22, 2009, 02:00:43 PM
Sub chairs do exist for home theater.  Not real audio.  Made to wow the Crowd.

In high end stereo (not home theater) you want all speakers up front.  The goal here is to reproduce the recording faithfully.

When you go to a concert, Does the Drummer and bass guitarist sit behind you?  NO. 

I use an audio control real time analyzer.  Most do not.  They are not that serious.  I have owned hundreds of speakers over the years.  We buy and sell audio. 

Experimentation is the key.  Do what you like.  Use what you like and enjoy.  I have $10,000 speakers here. I decided a while back that for me.  A set of vintage (real and not dept store crap) B and Os where clearly the best sounding speaker I ever heard.  So I kept them.  They might be Junk to the next guy. Audio does not have to be expensive.  I have a set of OLD JBL L12s in the other room.  We tested them at a high end audio store as my friend that owned the place never heard a set.  About 20 minutes into the audition he came in and said "get those F'in things out of here!" and got mad.  Garage sale 30 year old JBLs Blew his room full of High end audio away.

If you embark on this hobby... Be warned..  you WILL encounter AUDIO SNOBS.  I have met alot of them over the years.  Go to an audiophile party for a real good laugh.  These guys will sit around drinking cognac, smoking cigars and open virgin vinyl to play for the first time on $20,000 turntables..  Nobody is allowed to speak until the entire record is done. Then you sit around talk about the nuances of the strings in the band.. LOL  Every once in a while the guy would get up and meade a piece of Clay and lay it gently on a table.. And exclaim "i just found that resonace and got it!"

The truth to this thread is that choosing a sub is easy.  This is the least important choice to be made. Almost any decent sub will be just fine.  Its low end and if setup right, You cant hear it directly.

I have 3 or 4 powered subs in the store room.  To prove it, I will send steve one.
Clark


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 22, 2009, 03:11:00 PM

Clark is probably right - but there are just as many snobs in this hobby as in the other, or at least there are enough of them in both?

Ya think that's bad? How about art snobs ??

I prefer to hang with the DIY audio crowd myself. Much more grounded as a group. Sort of like the folks in ham radio who are homebrewers and build their own a lot... Or the folks who restore and modify boatanchors.

Most of the folks in the audio snobbery melieu usually seem to have a whole lot more $$ than actual knowledge, so that leads to a certain sort of insecurity and that leads to a "pack with a pecking order" situation very often. It happens, you know...

The opposite happens too, people with way way too much EE knowledge and zip appreciation of other matters... a good balance is nice.  ;D

                 _-_-bear


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: Pete, WA2CWA on December 22, 2009, 03:36:57 PM
Sub chairs do exist for home theater.  Not real audio.  Made to wow the Crowd.

In high end stereo (not home theater) you want all speakers up front.  The goal here is to reproduce the recording faithfully.

"home theater.  Not real audio.  Made to wow the Crowd."

Yep, that's what I paid the money for. Wow me every time I sit in front of the screen. I listen to my tunes either on an Ipod or from a box as background entertainment as I do other things. I have no time or patience to just sit in front of a box and listen to virgin vinyl, crusty tape, or CD's. Probably why I built so many sound activated light boxes back in the 70's.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 22, 2009, 06:29:39 PM


Pete, "boom and sizzle"?

I want the steak, not just the sizzle myself.

If the sound that is in the room is simply "there" and it is effortless, without electronic artifact and sounding utterly natural as if it were merely appearing as if by magic, that's what I want.

It's non-trivial to get the speakers to disappear, and even more daunting to get it to the point where it is as I just described. Most of the time even those who are striving for this goal don't get all the way there... but when you do... Voila!

                        _-_-


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 24, 2009, 06:02:02 PM


An example of a modern 15" subwoofer driver:

http://www.diyaudio.com/forums/swap-meet/157259-kove-armageddon-15-1050rms.html

while there take a look around - if you'd like to see some spectacularly excellent DIY projects, you'll find them on this site!! Everything from built on a wood board to drop dead sculpture enclosures!! All DIY.

Also discussions of all matters audio, solid state, tubes and speakers of all types. Very little noise on the channel.

                       _-_-bear


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that i
Post by: W1RKW on December 26, 2009, 07:55:37 PM
Don't forget the input end.... Source material and the input device.


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 27, 2009, 09:15:22 PM


Yet another qwazy sub woofer company:

http://www.rythmikaudio.com/products2.html

...submitted for your approval... - Rod Serling



Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on December 27, 2009, 09:18:44 PM


The mother lode:

http://www.diyaudio.com/forums/subwoofers/

of course you'll have to browse back in time to find projects and ideas that correspond to what we've been discussing...

               _-_-bear


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: ke7trp on January 14, 2010, 05:36:31 PM
Steve. I got this in today. If you want it, you can have it real cheap. I have two sets.  I just tested it. Its real heavy and has real solid Low end. Very compact. Plenty of punch.

http://www.anthonygallo.co.uk/pages/products-subwoofers-mps150.php


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: flintstone mop on January 15, 2010, 09:47:34 AM
Very intersting thread and the many flavors of music reproduction.
I may have missed something, though, has Steve ever mentioned his taste in music? I do know that he is lover of the very low end of audio. I don't know if this is just some criteria picked out like a "spec sheet" or if he listens to classical music and wants to feel the lower notes of a pipe organ or would this be for a home theater app and the effects of a dinasour tromping through the forest???? dunno
And this has not been "audiophoolery" coz we are basically looking for a design of a speaker to reproduce a certain effect in the listening environement.

Fred


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: W2WDX on January 15, 2010, 04:57:11 PM
Long Post Warning!!!!!!   Long Post Warning!!!!!!   Long Post Warning!!!!!!   Long Post Warning!!!!!!   Long Post Warning!!!!!!

Hi All,

Have to jump in on this one. I noticed a few of you saying "bigger is better". That's an old notion based on old technology. I will elaborate...

Drivers years ago had many limitations, low power handling, limited excursion due to materials available, poor heat dissipation, low efficiency (electrical), etc. Large boxes with huge mass and diameter drivers where the solution with the available driver choices.

The compromises made were, large diameter (and high mass as a result) moved alot of air ... but very very slowly. High damping factors are required for the amplifiers to control the loads and to overcome momentum of the mass of the drivers. This was difficult to achieve due to amplifier designs and the gauge of speaker wire at a given length; not to mention the associated costs. Older designs were "slow" or "tubby" when examined in the time domain.

Another compromise was large boxes were required, due to the fact that the larger the box the lower the resonance. Older driver designs which had small excursion ratings (Xmax) will self destruct over time if driven below the resonance of the box design; whether it is a closed box or ported. So to achieve low frequency response you needed a large box. Another problem associated with large boxes is in the external cabinet stiffness. External resonance (vibration) of the boxes is radiated and at various phase angles from the cabinet. This causes unpredictable acoustic additions and cancellations within the listening space. Think of it like a longer span on a truss or i-beam. The longer the length the less stiff it is. These factors are difficult to control without massive and extensive internal bracing or extremely stiff cabinet materials (like concrete for example). Additionally internal bracing lowers the internal volume of the box, forcing the box to be even larger.

Another factor is in sound pressure levels and the ability to compensate for Fletcher-Munson curves (equal loudness contours). At lower frequencies human perception (whether aural or tactile) is much lower than at higher frequencies. Below 100Hz most of this perception is tactile in nature (felt rather than heard). Furthermore the lower you go the more tactile it becomes. To overcome this, large diameter drivers were employed to "move more air"; to increase the SPL (sound pressure level) output of the loudspeaker system (this also forced even larger cabinets as a result, BTW). Power and driver efficiency now also become a limiting factor.

Power was limited back in the day. Finding an amplifier over 200w for instance was difficult and expensive. So loudspeakers were made to be acoustically efficient. Porting or even horns were employed to boast efficiency, but efficiency is a compromise that limits other factors, such as speed, frequency response flatness, phase coherency, and a host of other factors. Additionally, even if the power was available, the drivers electrical efficiency (the ability for the motor to covert the electrical energy into kinetic work) was very low.

Another response to this was that users of these systems, in order to get more perceived output, placed their speakers in the corners of the room. Now while this did increase the perceived levels, it would caused sever instability in the frequency response of the system due to phase incoherency. The coupling effects of a loudspeaker to a surface is such that while certain frequencies (particularly low frequency) are boosted while others are cut. The response curve becomes very non-linear the closer you come to a surface with a loudspeaker. This effect is doubled or tripled when we are talking about a corner in an enclosed space. So while the perceived loudness is increased, it is only happening at certain frequencies, and in fact lowered at others. Furthermore, since these issues are related to phase incoherency they are not easily correctable by room equalization in terms of amplitude response manipulation.

Many other compromise solutions have been employed over the years to overcome or side step these limitations in technology. Some worked better than others, but all had shortcomings and side effects. The need was there to improve the basic technology. Over the years drivers and cabinets have improved due to advances in materials. This allowed the important parameters to be improved and better uncompromised performance levels could be  achieved. Some of these are improved magnetic materials & structures, more durable and flexible surround materials, higher power handling techniques (in drivers), stiffer cabinet materials, higher power levels and efficiency in amplifiers, smaller amplifiers at these higher levels, etc.

One early attempt at overcoming the prevailing limitations in the motor structures of drivers was tried, with some success, by ServoDrive in the Contrabass model. It utilized an industrial servo motor to move the cones of two opposing drivers. It was used primarily for live sound application and scientific purposes. (note: Pink Floyd used these for a while in its live shows). Here's some images:

(http://www.soundimage.dk/images/Contrabass_clam.gif)

(http://www.ultimateavmag.com/images/archivesart/704way.servodrive.jpg)

While this system was able to produce significant low frequency information down to 16Hz (-3dB at 22Hz) it was prone to mechanical failure due to the belts and rods used to move the cones. But when it worked ... IT WORKED WELL!!!

Damping factor is an often overlooked issue in low frequency reproduction. Three factors effect this parameter: the amplifiers own rating (output impedance), the various impedance loads of the loudspeaker system (whether it is reactive or more resistive) and the gauge and length of the speaker wire (resistance). Assuming one has an amplifier with a high damping factor ability, locating the loudspeaker any distance from the amplifier would force an increase in wire gauge proportional to the length. It is important to use loudspeaker cables with sufficient gauge (thickness) for the length being used. The resistance introduced by inadequate cables reduces both the output power and the motion control of the loudspeakers. The latter occurs because the damping factor decreases as the cable resistance increases. This is very important because the amplifier’s excellent damping factor can easily be negated by insufficient loudspeaker cables.

Incidentally, larger drivers tend to be more reactive than purely resistive, complicating the damping factor curves at various low frequencies. In most situations, damping factor is high enough so as to not introduce significant distortions. This does become problematic when thin speaker wire is used over long distances to feed a loudspeaker. The resistances added to the system are significant enough to swamp the effects of a low impedance output amplifier. So while damping factor is an issue it is not as critical as other parameter discussed here. I only mention it since the impedance at lower frequencies vary quite significantly in most loudspeaker systems especially near and below cabinet resonance. Additionally, older larger drivers tend to be more reactive in their impedance than resistive.

Ummm ... and take notice: no mention of OFC speaker cable here!!!  ;D

With the advent of small very efficient amplifier designs this whole thing becomes a moot point since one can now place the amplifier inside the loudspeaker. This is a common practice these days.

Also, smaller diameter lower mass drivers with high Xmax (excursion) have been developed. It is not uncommon to find subwoofers with 12" drivers operating well below the cabinet resonance these days. The limiting factors forcing large cabinet sizes have been mostly overcome due to advances in driver design. These include longer excursion, high power handling, more efficient magnet/motor structures, lower mass. With the addition of very high power amplifiers built into the cabinets other limiting factors have been overcome. Additionally, the active electronics inside cabinet can be designed to operate specifically for the subwoofer system. For instance some manufacturers have added analysis systems right into the subwoofers to adjust parameters like phase alignment, room correction, ELF control and limiting design specifically for the subwoofer. One good example of this is some products by JL Audio in its Fathom series. I have some experience with the 12" version (F112) of this sub. Here's an image:

(http://home.jlaudio.com/images/10469.jpg)

This particular system measure 18.5" x 15" x 17.6" and has a measured frequency response of 21-119Hz ±1.5dB with the -3dB point being 19Hz. The internal amplifier can deliver 1200w RMS of power, short term.

It is now possible to build small subwoofers that have extended low frequency ability; as low as 15Hz. And do so with high output and very flat phase and amplitude response. One caveat: This is all based on anechoic conditions ... read on ...

Bear in mind, all of this is modified by the room, which is really the dominant limiting factor. No room in the average home is anechoic in nature. Real world issues take precedence. Room effects on low frequency are almost impossible to overcome or even predict, which is why anechoic measurement is important (as well as the previously mentioned active electronics). The anechoic measurement gives a starting point and a reference of performance, which is used by the active electronics. Internal volume, physical dimensions and and shape of the room effect low frequency performance. Most homes do not have ideal rooms for this type of audio performance. Since there is a point of reference, in the form of an anechoic measurement, the active electronics applied here helps modify the performance of the sub to bring the sound closer to the known anechoic ideal within a real world room.

BTW, in the sound reinforcement world it is not uncommon for most subwoofer systems to be based on small drivers with large excursion, usually 12". This is becoming much more prevalent these days at the top pro level, especially in line array systems. Most subs are self powered and "flown" usually at the top of the Mid/H line array. This is an example of a line array with 12" based subs.

(http://www.qscaudio.com/images/products/WL8/WL3082array_with_sub_top_sm.jpg)

Of course, extreme low frequency information (40-35Hz and lower) are usually avoided in this application due to masking effects in large spaces. This is not the case in home systems where open microphones are not in play, so low frequency extension, as low as possible, is preferred.

All of the above is not audiophoolery. It's basic simple physics ... or not so simple physics as it were.  :)

John
W2WDX


Title: Re: Sub-Woofer Question - AudioPhool Experts (which I am not - an expert, that is).
Post by: WBear2GCR on January 22, 2010, 06:56:52 PM


The Servo drive is not dead - Tom Danley still makes subs...

Here's a driver for Steve:

http://www.diyaudio.com/forums/swap-meet/156894-maelstrom-x-18-subwoofer-drivers-w-warranty.html

                   _-_-bear
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands