Infinite Baffle and the Audiophile

[FrantzM]

Micro

Indeed it is.Subwoofer placement is critical to eprformance and there is usually one best spot along the front wall. This can be found through trial and error using a box subwoofer. One you move around until you've found through listening and measuring, the best placement ... That is where you cut the opening.. Once yo have cut it , you can't move this opening around .
Some people just make a hole in the middle and EQ to compensate for placement that works rather well because of the huge headroom, thus latitude afforded by the multiplicity of drivers .. It is not ideal, the least you EQ the better the results so.. find a spot, then cut your bunker wall ..Buddget for such trial could be be less than $1K and you may actually like t enough to leave it at that .. for a while .. you're an audiophile after all

 

[Robh3606]

IMHO, in this hobby getting what you call the "engineering" aspect is not enough, something else coming from long experience and knowledge is also needed.

Hello Micro

Well to me that translates to your own subjective opinion. More importantly if the "engineering" is not right subjectively it won't be right as well. We are talking sub-woofers and frankly the most important issue is placement. The room and placement is the biggest factor to what the in-room response is. Using one sub-woofer there is only so much you can do with EQ to smooth things out. One of the reasons multiple subs works better than a single. You could have the "best" sub-woofer in the world and bad placement could make it sound awful.

Rob

 

[amirm]

Frantz, why wouldn't I use a tapped horn sub instead of this approach? They provide copious amount of bass. Their clever impedance matching allows better efficiency. Here are the specs for a random Danley sub: http://www.danleysoundlabs.com/tapped_horn.asp?MODEL=DTS 20

"ModelTS 20
Max. SPL: 128 db
Sensitivity:95db
Magnitude Response: 18 Hz - 100 Hz
Power Rating: 1,000 W
Dimensions: 87.5 x 18 x 20
Weight:220 lbs

Quite heavy and big to be sure but it comes ready to go and if you work with a dealer, they will build you custom sizes of it. We installed a couple of their "cine monster" in a movie theater and it darn near destroyed the building with bass!

 

[mep]

Frantz, why wouldn't I use a tapped horn sub instead of this approach? They provide copious amount of bass. Their clever impedance matching allows better efficiency. Here are the specs for a random Danley sub: http://www.danleysoundlabs.com/tapped_horn.asp?MODEL=DTS 20

"ModelTS 20
Max. SPL: 128 db
Sensitivity:95db
Magnitude Response: 18 Hz - 100 Hz
Power Rating: 1,000 W
Dimensions: 87.5 x 18 x 20
Weight:220 lbs

Quite heavy and big to be sure but it comes ready to go and if you work with a dealer, they will build you custom sizes of it. We installed a couple of their "cine monster" in a movie theater and it darn near destroyed the building with bass!

How much does it cost?

 

[FrantzM]

Frantz, why wouldn't I use a tapped horn sub instead of this approach? They provide copious amount of bass. Their clever impedance matching allows better efficiency. Here are the specs for a random Danley sub: http://www.danleysoundlabs.com/tapped_horn.asp?MODEL=DTS 20

"ModelTS 20
Max. SPL: 128 db
Sensitivity:95db
Magnitude Response: 18 Hz - 100 Hz
Power Rating: 1,000 W
Dimensions: 87.5 x 18 x 20
Weight:220 lbs

Quite heavy and big to be sure but it comes ready to go and if you work with a dealer, they will build you custom sizes of it. We installed a couple of their "cine monster" in a movie theater and it darn near destroyed the building with bass!

I don't know much about the sound quality of tappered horns. Anything by Danley should be taken seriously and not sneered at. The man knows his stuff. He may lack the marketing pizzazz of some High-End designers but he is the kind of person with whom they (High End designers) will likely be very hesitant to discuss bass reproduction with. You name ANY high-End subwoofer designer you want to , he likely will have to bow to Danley when it comes to bass reproduction ... SoByou have my perspective
I know for a fact that a $2000 IB would likely surpass its specs. 4 18 inch Fi Caraudio IB 21, The Behringer Eurotour 4000 watts amp and a cheap behringer DCX-2496 will lkely outperform this one on paper as well... The DTS20 can be moved around though ... albeit with great difficulty

 

[amirm]

How much does it cost?

I don't have the DTS-20 price handy but DTS-10 kit is $1,000.

 

[Ron Party]

Here is the link to fellow member Wardsweb's build of the DTS-10 kit, complete with pictures.

I'm sure Mark Seaton could contribute greatly to the discussion here and I will ping him.

 

[microstrip]

Here is the link to fellow member Wardsweb's build of the DTS-10 kit, complete with pictures.

I'm sure Mark Seaton could contribute greatly to the discussion here and I will ping him.

Very nice sub. The biggest speakers I have built in the late 70s was a 150 lb transmission line speaker using the oval KEF B139. Much later I considered the Monochord design, using a 12" speaker, but as at time I was living in a condominium, I wisely gave up the idea of having a great bass ...

Curiously, already at that time some people claimed that the best type of sub to complement dipole speakers was the transmission line. The DTS-10 is awakening the DIY person in me. Wood is softer than stone!

 

[mep]

The DTS 10 reminds me of a transmission line, but is it?

 

[JonFo]

The DTS 10 reminds me of a transmission line, but is it?

It is a tapped horn. For more info see this paper from Danley or check out the DIYaudio forum for a bunch of enthusiast designed tapped horns.

 

[JonFo]

...
I know for a fact that a $2000 IB would likely surpass its specs. 4 18 inch Fi Caraudio IB 21, The Behringer Eurotour 4000 watts amp and a cheap behringer DCX-2496 will lkely outperform this one on paper as well...

Frankz, you keep mentioning huge wattage amps for IBs, and I'd like to clarify for everyone edification that IB's are so efficient, one rarely needs more than 400 watts or so to push a driver to full x-max and bottom them out. Actually, the biggest danger in an IB setup is frying ones drivers by overpowering them.
I use a limiter configured in my DBX DRiveRack 4800 to keep the drivers safe from upstream issues (a shorted input, vol turned up too loud, etc.).

For IB, you want an amp that is stable at low impedance and has good 'control' over the drivers and enough headroom for peaks. Class G amps seem to do that well.

 

[FrantzM]

Jonfo

I go for power whenever I can especially when it is plentiful and affordable... Again a matter of headroom. If we were to take the case of 4 Fi I8-inchers. I would guess the sensitivity at 1 watt/1meter to be about 95 dB, Once one adds room gain then it could be even more... I however have come to observe that the more power one has available in the bass (and IMO elsewhere) the better the reproduction everything else being equal ...

 

[mojave]

Franz, thanks for bringing this up. It gives me impetus to finish my IB. Last February I bought the last 8 Acoustic Elegance IB15 drivers (with copper shorting rings). These were handmade by John Janowitz, the owner of AE Speakers. I have two Face Audio F1200TS amps which will provide 4800 watts. I also have two of the Dayton SA1000 amps that JonFo mentioned that I can try. Eight IB15 drivers only need 400 watts at 14 Hz to reach maximum excursion. It is headroom at the higher frequencies that necessitate more power.

I have heard a lot of subwoofers in the past month and a half. In October, I cohosted the Subfest 2011 in Omaha, NE. Mark Seaton was present and two other vendors. I heard the Seaton Submersive (sealed), Danley DTS-10 (tapped horn), and dual JTR Speakers Captivators (18" reflex/ported) among others. I had also built out a pair of front loaded horn speakers with 15" drivers. The front loaded and tapped horn speakers are very efficient, but they are also very large. They also need more EQ to get a flat frequency response. They aren't very practical for most rooms and it is much easier to place multiple sealed or reflex subs.

I had built out 4 pairs of dual opposed 15" sealed subs for the Subfest, but the wiring came loose on one pair and we ran out of time to fix/listen to them. I finally listened to all four subs (8 drivers) two weeks ago using Dayton SA1000 amps. Having this many drivers provides one with huge headroom and clean output. Even at very high SPL's, the drivers were barely moving. It gave me a glimpse of what an IB system can sound like.

 

[microstrip]

What you be your suggestion of woofer type and brand for a 100 cube meter (3700 cube feet) room?

 

[FrantzM]

What you be your suggestion of woofer type and brand for a 100 cube meter (3700 cube feet) room?

I would have suggested a 4-driver IB for such a room. I like the specs of the Fi Car Audio IB 318. Displacement is about 6 liters per drivers. Power Handling is a substantial 500 watts per driver @20 Hz, efficiency is a healthy 89.4 dB/1W/1m. I also like the price ( about $240 /each) and the fact that you can ask the manufacturer to optimize certain parameter for Infinite Baffle mounting. You could vent the back wave in a 2 x 2 x 2 meter room or cavity to be on the safe side although if we were to go by the 10 times the total Vas rule-of-thumb, a 1 x 1 x 1meter would suffice. Calculations shows however that true "infinite" baffle loading (virtually zero Hemholtx radiator loading) requires 25 times the total Vas. With 4 drivers and 2-ch music I doubt you need more than 300 watts on the IB but ... if you can get your hand on a more powerful amp .. Why not ?

 

[microstrip]

I would have suggested a 4-driver IB for such a room. I like the specs of the Fi Car Audio IB 318. Displacement is about 6 liters per drivers. Power Handling is a substantial 500 watts per driver @20 Hz, efficiency is a healthy 89.4 dB/1W/1m. I also like the price ( about $240 /each) and the fact that you can ask the manufacturer to optimize certain parameter for Infinite Baffle mounting. You could vent the back wave in a 2 x 2 x 2 meter room or cavity to be on the safe side although if we were to go by the 10 times the total Vas rule-of-thumb, a 1 x 1 x 1meter would suffice. Calculations shows however that true "infinite" baffle loading (virtually zero Hemholtx radiator loading) requires 25 times the total Vas. With 4 drivers and 2-ch music I doubt you need more than 300 watts on the IB but ... if you can get your hand on a more powerful amp .. Why not ?

Frank,

Thanks. I emailed Fi Car but received an email back saying they are late replying to email ... I will also look for alternatives from european companies, overheads due to buying from the USA can be very high.

Is there any acoustical advantage in using a manifold compared to drilling four speaker holes in the wall ?

BTW, Harman subwoofer placement white paper suggest using a minimum of two subwofers, centered and placed at opposite walls. Must one build two IBs ?

 

[audioguy]

My ears were burning this morning, now I know why

I'm not exactly a neighbor but do live in the same state. How do I get invited up to hear your system (sub)?

 

[Mark Seaton]

A decade ago I use Cara-CAD and the RPG room acoustics modeling programs, which for their day, we're quite helpful. But tech has moved beyond that, and for a system of your quality, I'd suggest contacting Amir about doing a fluid-model analysis of your room. that will be helpful in understanding not only where any sub should go, but also what possible results you might expect if you combine the IB + another sub in the room to even out modes.

The brute-force method is to use your existing sub, locate it as ideally as possible with relation to where an IB manifold would go and then measure the response. Then rinse and repeat in alternate locations to confirm.

Before I cut the hole for my IB, I placed a sub at that spot and measured, then listened to it in that location for a month or two to ensure I'd be happy with the results.

Merry Christmas.

Hi JonFo,

This just looks like a lot of fun and not far removed from some ideas I kicked around as a Martin Logan franken-speaker I dreamed of concocting way back when I slaved for a Martin Logan retailer and after had the pleasure of hearing the Statement e2's in Gayle's home and later installing 2 pair. It is nice and encouraging to see such positive impressions even when using "lowly" pro audio gear to handle the crossover duties.

I thought these two images are are useful to show how you implemented your IB:

I am currently helping a friend/customer build a quasi-IB into his riser in a large basement where we're using 8 18" woofers and one of my 4kW amplifiers. Similar to your experience, we've placed subwoofers in the locations the woofers will be mounted, and confirmed these locations are useful at getting bass to the listener.

As to the "sound" of an IB, I have my own particular experiences and done my own investigations to see what really matters, and I do not feel it is any direct relation to the lack of a box behind the woofer, but rather the parameters and behavior which is commonly achieved when you have lots of displacement/capability and a very low Fb (driver + box resonant frequency) sealed box. There are some pitfalls in construction to watch for if someone is careless, but it is a very attractive solution I've heard in a handful of exceptional sounding systems.

Anyone here been around the DIY community long enough to remember a rather impressive DIY system using BG75 ribbons, column/stack of dipole woofers and 8 12" ACI woofers in an attic IB? He was located in the NW Chicago area and I believe his first name was Tom...

The biggest problem I see with IB subwoofers for most audiophiles and the market in general is that it doesn't lend itself to impulsive system additions, and you can't find extensive reviews of the exact setup you would be installing. IMO, the gradual acceptance and improvements in electronic room correction and related devices are what have started to make such options much more viable.

 

[JonFo]

I'm not exactly a neighbor but do live in the same state. How do I get invited up to hear your system (sub)?

Easy, you just got invited. Please see your PM.

Besides the IB sub, you'll get to hear the real franken-monster - my 'large' center channel firmly bolted to the IB in this pic

 

[Ron Party]

Sometimes one needs only one word to encapsulate the totality of one's thoughts. Stated another way, an idea is an emotion with roots. Jonathan: wonderful.