Infinite Baffle and the Audiophile

[Phelonious Ponk]

They are usually not in the room … Invisible... So why aren’t they more popular?

They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at?

Tim

[mep]

They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at?

Tim

I don’t think that’s it at all Tim. Many people probably think they could never build something that will sound better than companies who make subs for a living. Plus, there is woodworking involved that some people have no skills at and it would be intimidating. Then throw in the fact that you have to have the type of room that you have access to build in an IB. It’s just much easier to buy a sub.

However, this article has got me thinking. I have the space on the left side wall where I could do this. The main thing that intimidates me is the requirement to have the outboard electronic crossover/bass management system that converts your analog to digital and back again and then setting up the bass management for all of the subs. It would be great to have someone come to your house that has been through it and help you get it set up. I am definitely interested though.

And yes, subs do increase the size of the soundstage. As I have said before, there is space in bass. My new sub should be arriving this Thursday. For the money I paid for it, I could have gone the IB route. I probably still will. Maybe two 15” subs in a manifold.

[Phelonious Ponk]

I don’t think that’s it at all Tim. Many people probably think they could never build something that will sound better than companies who make subs for a living. Plus, there is woodworking involved that some people have no skills at and it would be intimidating. Then throw in the fact that you have to have the type of room that you have access to build in an IB. It’s just much easier to buy a sub.

However, this article has got me thinking. I have the space on the left side wall where I could do this. The main thing that intimidates me is the requirement to have the outboard electronic crossover/bass management system that converts your analog to digital and back again and then setting up the bass management for all of the subs. It would be great to have someone come to your house that has been through it and help you get it set up. I am definitely interested though.

And yes, subs do increase the size of the soundstage. As I have said before, there is space in bass. My new sub should be arriving this Thursday. For the money I paid for it, I could have gone the IB route. I probably still will. Maybe two 15” subs in a manifold.

Of course, Mark, that was meant as a joke. I myself would rather buy a sub than do all that's required to put in an IB system it's quite intimidating.

And of course bass expands sound stage. Everything does.

[Robh3606]

In fact, I could still pursue it if such a modeling program existed. I could vent it into the next room even though it is a finished room.

Anyone know of such a program?

Hello Audioguy

Yes it really quite simple all you need to do is take any box program and model the drivers in a large box. Basically what you want to do is have the drivers in a very large box about 10X the Vas of the driver. You can get freeware box programs that will tell you what the driver response will be without EQ.

You can determine the number of drivers you need and the EQ needed. What you have to watch is the X-Max on the drivers as they will simply run out of excursion depending on what your lowest target frequency is and you should have them high-pass filtered to protect them from over-excursion.

Here's a free-bee box program Win ISD or Win ISD Pro you can use either but with the Pro Version you can look at driver excursion.

http://www.linearteam.dk/default.aspx?pageid=winisd

Rob

[microstrip]

They require a good bit of thought, planning, and labor, and you don't get to buy "the right stuff." And let's face it; this is a consumer hobby.

I mean what's more fun? Going down to the high end store and buying a couple (or more) of Deep Supreme Luxinators (given 5 stars by Audio Intelligence Online), taking them home, plugging them in, then posting on WBF about the palpable expansion of your sound stage, or cutting a hole in your floor, building a reinforced plywood box in your crawl space and hooking it all up to a couple of dirt-cheap pro audio amps and an equalizer that your buds will look down their noses at?

Tim

Tim,

I think you are overlooking the planing project and considering that just adding some bass extension is an easy job. Unhappy we want quality, not only quantity. And first of all we need to know exactly what we are "buying". A good plan must be "certified", and getting this quality stamp is not easy - a golden rule of audio DIY is that the builder should not be the judge or even part of the jury.

I appreciate debates in forums because everything in audio is a compromise, nothing is perfect, and people have different views on it. Until know I have heard only positive things about IB. I would also like to have the views of the opponents and what the defenders have to say about them.

[Robh3606]

And first of all we need to know exactly what we are "buying". A good plan must be "certified", and getting this quality stamp is not easy - a golden rule of audio DIY is that the builder should not be the judge or even part of the jury.

That's rather silly and defeats the purpose. If you are serious about DIY you have plenty of tools at your disposal to verify your end result. That's what measurements are for, they confirm that you got the engineering part correct and they won't lie to you if you are doing them correctly.

When I DIY a pair of speakers I don't worry about getting my design certified. I build the cabinets, take measurements in the cabinets, design the crossovers and then measure the finished system. It works very well.

Rob

[FrantzM]

Hi

The biggest drawback of the IB is its immovability. Once it is there it is there. One must carefully chose where you will put that opening on your front wall or ceiling or floor. It is mistake to think of IB as quantity only. It si quality and of a nature that has to be heard to be believed.
It is not magic. This quality comes from the fact that IB affords multiple drivers. Bass, low bass in particular is about moving air. Lot of it. IB affords the audiophile to move quantity of air that is simply impossible in a commercial design. Example , you want to use 8 18 inch drivers? Deal, Done once you have the overture of your manifold, you can then have 8 drivers in that manifold with each driver working in its most linear region... and of course producing the lowest distortion possible, while being able to track the micro to macro dynamics of the music or other thing you want to listen to ... Meanwhile IB cost little, very little. You throw away the compromise of the box... The drivers are essentially operating in free air. You can eq for the flattest bass you can down to single digits and up to 100 Hz with ease, since you have so much headroom.. Let's take an example. An IB with 4 long excursion Drivers driven by 4000 watts or more (oh Yes you can and it doesn't have to be expensive) in a 30 X 20 X 15 room.. such an IB will be able to deliver 120 dB at 20 Hz without much EQ... You then EQ the darn thing down not up …with so much headroom you can afford to do that and still you are pushing the whole contraption to even lower THD level in the low bass ... The thing with IB is HEADROOM .. Lot of it, thus agility . You do have power too, lot of it, yet that i not what you need, that is what you have. Coupling that with additional commercial subs if you need to smooth out the bass in the room and you have the best bass your money can buy. The cost to make an IB with 8 superlative drivers such as the Fi IB318 ( less than $1000 for 4) and 4000 watts or of Pro amp would be low.. I venture $5000 including a contractor for the woodwork, wall cutting, driver mounting and wall finishing ... Expect single digits in the low bass at substantial output and you can have the flattest bass you will have experienced or you can have house curves and shape the bass the way you want it .. Tilt is for the low, flat, tilt up you can because you have the headroom to never run the drivers hard. Then you smooth out the response in the bass with one or two smaller subs ... Say a pair of JL AUdio Fathom F 113 and you add digital DSP and be fine .. very fine... Total? Less than $10,000 and I am pushing .. As for the measurements on IBs it is a sub, albeit a fixed sub. The method most people use is to get a small subs and find the best locationin the front wall, I know I am repeating, then yo mount the manifold or drivers there.. power the darn thing and measure as if it were a "normal" subwoofer. EQ is the same you would have done for a "normal" sub ...
Disadvantages? I don't see many
Planning? Within what audiophiles routinely do ... We lift our cables for God Sake ! And plan their routes!!!
And if you don't like the results? It is best to start with 2 drivers and a manifold ... Could be less than $1000 including amplifier ... If you really , but really don't like it .. You close the wall and are out of $1000 .. The vagaries of an audiophiles, we have spend much more and lost much more on gear we hated thereafter ... I doubt it though .. IBs are that good $ 1,000 will have you shaking your head in disbelief .. Often more than your head ..

[microstrip]

That's rather silly and defeats the purpose. If you are serious about DIY you have plenty of tools at your disposal to verify your end result. That's what measurements are for, they confirm that you got the engineering part correct and they won't lie to you if you are doing them correctly.

When I DIY a pair of speakers I don't worry about getting my design certified. I build the cabinets, take measurements in the cabinets, design the crossovers and then measure the finished system. It works very well.

Rob

Rob,

I respect the DIY approach - I manufactured a lot of DIY speakers to finance my hifi addictions when I was a student, and a few of my friends currently follow the DIY approach and we frequently discuss technical aspects, mainly of tube amplifier DIY. If I had the time I would love to come back to DIY.

But assuming that the few measurements that a non-expert, such as myself, can carry using the modern PC based tools available - and I have and use a few of them - can confirm that such system is superior or comparable to the best subwoofers available in the market is not an easy assessment. 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.

I have to say I am seriously considering the IB. But the back wall of my listening room is a 1.5 feet thick stone wall - experimental drilling is out of question. I will only try it if I have confidence in the project.

Thanks for your advice.

[microstrip]

Hi

The biggest drawback of the IB is its immovability. Once it is there it is there. One must carefully chose where you will put that opening on your front wall or ceiling or floor (...) .

Just the big question for me. It seems there is no unanimous opinion on these matters.
To make it worst some people clearly state that positioning the opening is very critical and putting it in the wrong position will spoil it ...

[FrantzM]

Subwoofers are one area where measurements, ver easily correlate to what one hears .... If it is reasonably flat in the bass, then it sound like that... I can understand that one has to approachIB with some reserve when you are dealing with a 1.5 feet brick wall... The point is that you have to find the position where a normal, commercial wsubwoofer would sound the best along the front wall, once this is done, then you have to take the leap of faith ... As I said you don't go big, you simply use a pair of driver and power them with any available high power amp you have handy ... If you don't like what you hear from the 2 drivers then you close the wall , end of the story. My experience is that any person who's tried this doesn't come back .. The two drivers will outperform most any commercial subwoofer you can dream of ... as for sound quality the only competition for IBs c might be dipole subwoofers .. My extremely superficial dabbling with them was that they seem to tax the drivers too much, likely due to the fact that some frequencies have to be boosted to compensate for the cancellation dues to the out of phase back wave ... I quickly abandoned this idea when the size of the baffle started looking like a strange wall in the listening room ... IBs are completely invisible, taking no space in the listening room ...
I also would not put an IB in the back of the listening room for 2-channel listening. YMMV