AV Subs v true infinite baffle for electronic organs? (1 Viewer)

[ChrisBee]

Hi

As a bass fan, always eager to learn more, I've just been reading an interesting website by an electronic organ enthusiast.

He worked through the various options of large bass enclosure (sealed, reflex, horn etc) But actually ended up with a true infinite baffle as the ideal way to play 32 foot stops in a normal home.

He fitted a couple of 12" units into the loft trapdoor driven by a 60 watt amp and he was a happy man! He even claimed that the organist didn't have to be in the same room as the drive units provided the room where he played was large enough to support standing waves at the frequency required. The whole house would resonate to the very low frequencies. I know that feeling!

His frequency response wasn't even that impressive. Falling off at 30Hz but with sufficient output at 16Hz to satisfy his demand for very low distortion on the 'quiet' 32' stops.

I read all this and wondered how our AV-orientated subs would cope with such extended notes at 16Hz. My 16-46 will certainly play such notes at truly house-shaking level. I was never brave enough to go below 14Hz for more than 2 seconds in case the windows left home permanently! :b

But how many more 16-46s would I need to match his true infinite baffle?

Exactly how efficient are infinite baffles compared with our popular AV subs? We should be told! :wink:

Regards
ChrisBee

 

[stephanX]

infiniate baffle will always have a lower Q and therefore "tighter" sound, as theres next to no forces acting against the drivers, theyr playing freeair, and the moter needs only a small amount of strength to push the drivers to the limit. It is will also have a very shallow frequency roloff due to the very low q.

The only bass that comes close to IB in tightness and accuracy is dipole IMO.

im not insulting any other alignments by any other means, they all have their own merits. thats why they exist.

 

[ChrisBee]

Hi stephanx

I'm not arguing, but here is the frequency response of two 12" units (ceiling-mounted) from the website. This looks very like -20dB at 16Hz to me.

http://www.pykett.org.uk/vlf_fig6.gif

Here is the website URL:

http://www.pykett.org.uk/vlf_repro.htm

My own single 16-46 is +10dB at 16Hz in my 30 foot open-plan listening space.

I just find this interesting and am trying to understand the supposed advantages of true infinite baffles over the superb, modern reflex bass reproducers like my own SVS.

I fitted a 10" bass unit into a sealed walk-in closet back in the 60's. I remember the bass was almost non-existant compared with other forms of loading I tried at the time. Including huge reflex boxes and folded concentric horns.

Regards
ChrisBee

 

[Eddie Horton]

Chris, go to the "Cult Of The Infinitely Baffled" message board and look around. I don't have an IB sub and don't claim to know a fraction of what those guys do, but it's my understanding that IB subs aren't primarily for insane SPL's (although they can play quite loud with the right setup). The advantage of IB is the accuracy and tightness they provide.

 

[ChrisBee]

Thanks Eddie

I have looked in over there in the past and often admired the installations shown on the website.

The problem is that the owners' superlatives almost exactly match those applied to other good subwoofers.

Is "accuracy and tightness" so overwhelmingly better that I should seriously consider an infinite baffle over a second 16-46 or PC Ultra for music and movies? The problem is that if I ask over there they are bound to say "yes". It's just like asking about SVS on here. :b

Regards
ChrisBee

 

[Joey Skinner]

You must hear an IB system to understand how clean and distortion free it is. At first you'll feel something is missing, then you realize it is the rumble, boominess and distortion associated with box subs.

The organ guy was using 2 12" speakers with a Fs of 32 and 60w of power and got good results. I'm using 4 15" speakers with a 500w amp that can effortlessly knock things off the wall if I wanted it to but that is not the point. I think the IB sub really shines when playing music. Bass guitar notes and drums sound live, very clean and distinct. And for HT I love to watch people jump out of their seat when an unexpected loud explosion happens.

Check out the "Cult Of The Infinitely Baffled". Hopefully it's guru, ThomasW, will respond here.

 

[Joey Skinner]

Chris, you make a good point. Every one will tell you their system is the best. All I have to compare is my IB system and my previous DIY Sonosub. But the IB blows it away plus I don't have a sub the size of a water heater in my living room.

If there is any way you can audition an IB sub I encourage you to do it. Surely there is some one in Denmark that has one.

 

[ChrisBee]

Thanks for your input.

I have been seriously considering a second 16-46 or even a PCU.

The problem my be getting hold of suitable drive units over here without paying a huge premium in tax and freight for special imports.

I've been reading about true infinite baffles since the 60's. Though it sounds as if things have moved on just a little bit from my 10" experiments. It's certainly very tempting.

Thanks again,

Regards
ChrisBee

 

[Jason Dalton]

Having +10dB @16Hz is simply a byproduct of a low tuning frequency and fortuitous room gain characteristics. The important thing is how much out put you can achieve @16Hz.

In the subsonic region almost all subwoofers are limited by their excursion capability, or more accurately their displacement capability. Its all about how much air the subwoofer can move. Most infinite baffle subwoofers use two, four or eight 15" or 18" woofers. Even the most modest of the inifite baffle units that are using dual 15's have 2 to 3 times excursion capability of any single 12" on the market.

 

[ChrisBee]

Thanks Jason

I'm investigating the likely cost of getting a set of 4 specialist IB 15"s sent over. I'm not likely to find such specialist drivers over here. It's mostly Auto and PA.

But I hesitate to think what the import tax and freight charges might be. :b

Thomas of "The IB Cult" has been very helpful. I might be asking some foolish questions on their forum if all goes well.

Best regards
ChrisBee

 

[Jason Dalton]

Good luck with your search.

 

[Robert_J]

What brands of auto subs do you have available? There are a lot of models that are suitable for IB, you just need to know what to look for in the T/S parameters.

-Robert

 

[ChrisBee]

Hi Robert

I really don't know what names are available. But 15" long-throw drivers with suitably low Fs must be quite rare in the auto sub field. They also tend to be made to look pretty which adds to the cost without adding to the performance when hidden away. A search through a few local websites suggested a tiny Xmax on the few 15" drivers available.

The AE IB15s seem ideal and good value in sets of 4. Provided the freight is affordable to Europe. I'm waiting on a US dealer to get back to me on freight charges.

I should add that if anyone has any specific (and affordable) 15" drivers in mind suitable for IB use I'd really like to hear about it.

Regards
ChrisBee

 

[Philip Hamm]

Chris. Once you turn to the dark side forever will it dominate your destiny......

Then again it may be a permanent cure for upgraditis. I don't think I'll ever want to upgrage my subwoofer, ever. Ever. I've had two SVS tubes demoed in my house. They sound great, "louder" than my IB, but not perfectly smooth like my IB. I did bottom out one of my drivers once though. That was kind of unsettling.

I recommend Crown pro amplification. You should be able to find plenty of used ones, they are industry standard. I'm using a Crown DC300A that's vintage 1973.

Best thing about it. No evidence of a sub in the room. What looks like a normal 16" square A/C return vent is really a hole in the wall for an IB sub.

 

[Ryan Schnacke]

"But how many more 16-46s would I need to match his true infinite baffle?
Exactly how efficient are infinite baffles compared with our popular AV subs? We should be told!"

These are 2 very different questions. But they're both simple to answer. Consider the IB sub to be just a really, really large sealed enclosure subwoofer. So large that the Qs of the sub is the Qts of the woofer and the tuning frequency of the sub is the Fs of the woofer. So now you've just got to compare your subwoofer to this large sealed sub.

I generally find that in the lower bass frequencies (near 20Hz) you need about 3X the excursion from a sealed sub to equal the SPL you can get from a vented sub. This is a loose rule of thumb that I've found to work for the types of woofers and enclosures I see being discussed around here most often. So 2 of the Tempest, Dayton DVC, Dayton IB15 or AE IB15 woofers should be about equal to an SVS 16-46PCi.

The sensitivity of the IB is the same as a really big sealed box. The big advantage here is that a really big box needs very little power to get those woofers moving at low frequencies. And using multiple woofers increases your sensitivity very quickly.

"His frequency response wasn't even that impressive. Falling off at 30Hz"
Unless he's got some leaks through the baffle, that's completely a function of the woofer. Again, tuning frequency of the IB sub = Fs of woofer.

"infiniate baffle will always have a lower Q"
Given the same woofer then yes.

"It is will also have a very shallow frequency roloff due to the very low q."
Not necessarily. The Q of an IB is strictly determined by the woofer. Use a Hi-Q woofer and you'll get a Hi-Q response. Model the Dayton IB15's in a huge enclosure and you'll see that they look like any other mid-Q sealed sub. Except that they're tuned really low for a sealed sub.

"The problem is that the owners' superlatives almost exactly match those applied to other good subwoofers."
The difference is that you often hear people saying how much better an IB is than conventional subs. But you never hear anyone saying that a conventional sub is better than an IB.

I'd focus on finding some good 15 inch drivers with decent excursion (15mm+ one-way) and low Fs (hopefully less than 25Hz). You can adjust the system Q and maybe even add some extension with a parametric EQ.

 

[ChrisBee]

Thanks for the further encouragement. I think I'm (almost) convinced now. I just wish my wife was!

I'm still lacking the necessary information to match amp power requirements against room size and number of IB drivers.

Is there a simple rule-of-thumb which will guide me?

I only need 110 dB @ 20Hz from a 4 x 15" IB in a very leaky 30 foot room. :wink:

I don't think I'm asking too much. I have that already from my single SVS 16-46.

Regards
Chris.B

 

[Ryan Schnacke]

Did you miss the 3X displacement rule I mentioned above? It is a loose rule of thumb and as such you will find some examples where its not quite as accurate.

But using this rule you could expect a 4 x 15" IB to give you +6dB in the low freqs (where excursion is the limitation) vs your SVS, given that a pair of the 15" woofers have ~3X the displacement of the SVS PCi woofer and you have sufficient power driving them. The woofers I mentioned above (with one-way Xmax around 16mm) meet this description.

Of course this does not take into account any difference in subwoofer placement. A poorly placed IB vs a well placed SVS is a whole different issue.

 

[frank manrique]

quote:

But how many more 16-46s would I need to match his true infinite baffle?
__________________________________________________ _____

...why...seven more plus two B12-Plus/4s, Chris!...


-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[frank manrique]

quote:

Of course this does not take into account any difference in subwoofer placement. A poorly placed IB vs a well placed SVS is a whole different issue.
__________________________________________________ ______

...and that is my concern exactly...should I decide to eventually do my own monster, no compromise IB subbass system...something I've been wanting to do ever since I saw and read about Tom Nousaine's subwoofer set up...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

 

[ChrisBee]

Hi

Thanks for all the continuing feedback gentlemen. I plan to place my IB exactly where my cylinder sits now. Just inside my right speaker. This position has proved to be optimal for quantity and quality.

Hi Frank

I knew the mention of serious bass would quickly get your attention.

It's not just about quantity its all about quality.

I found a website with an IB using 8 x18" drivers.

He must have been trying to compete with you.....and winning handsomely!

I hope to go with 4 x AE IB15s....for my right IB. :b

Then there is the option of a left IB.

Is that enough teasing Frank? Go on, you know you want to build an IB that's bigger and better than anything that has ever been done before. Though you'll need a new signature (and new neighbours!) :wink:

Regards
ChrisBee