Infinite baffle sub OK with most speakers?

[JonW]

I'm looking into building up a new stereo system, maybe for 90% music and 10% movies. Some people have pointed me in the direction of building an "infinite baffle" subwoofer. Most of the info is here:
http://www.f20.parsimony.net/forum36475/
Basically, you cut a hole in your wall, put some large drivers in there, and make a whole room/attic/basment your sub. Or something like that. They claim it's the best sounding bass available at any price. I haven't heard one yet. My room happens to have a hole in the floor from an old heating system. And I'm up for a little DIY construction project.

I'm curious if I build this thing, will it match OK with most any main speakers I decide to go with later? From what these people say, it's great for everything and as good as it gets. Idunno...

[kexodusc]

IMO if you can do it, IB is the best possible way to go. I've heard inexpensive IB setups that would put $5K subs to shame...
For most of us, it just won't ever happen as long as the wives run the house...but if you can do it...go for it...don't worry about it matching speakers, it's pretty much independant of what speakers you use.

[JonW]

Hi Kex,

Thanks for the response. I haven't heard one of these things yet, but I'd very much like to. I already have a hole in the floor from an old heating system. Not sure if it's in an OK place, though. Certainly the hole is not in the optimal place, though.

I'm shopping for stereo equipment. I'm up for a DIY project. And I don't have a wife. So... :D

[kexodusc]

Hi JonW, there are a bunch of criteria that you have to meet in order to successfully pull off an infinite baffle alignment.
I see you've already found one of the best websites on the subject, I never post there but I read every day. When I buy my next house or redo my current living room (just bought this house last year) it will defintely have IB subs.
I've only heard a few IB setups, only found out about these last fall. They won't disappoint you, but if you decide not to, you can get exceptional bang for the buck in a boring ol' box sub if you're willing to DIY one.

[JonW]

What criteria do you have in mind? I just heard about this the other day, for the first time. So I've got tons to learn. Right now, I'm most concerned with where the hole in the floor is versus where the rest of the speakers will be.

I just posted a few starting questions over at the "Cult." Could be fun if I do it. We'll see.

[kexodusc]

By criteria I mean there is certain aspects you'll have watch closely, there is flexibility but performance is a direct result of how you design this. The space the woofer's in has to be a certain volume, preferrably in the same are as the front main speakers (but not necessarily).

Read the FAQ at the Cult's web page....they can give you way more (and better) info than I could on this subject.

[JonW]

Yup, I've been reading a lot over there. Tons of good info. If I do this, I've got a lot of learning to do. I've posted a series of questions, a couple days ago.

Last night, I measured the room and made a diagram of the room, where the hole in the floor is, where I might put the main speakers, etc. I posted the picture over there. Hopefully someone can help me figure out if the configuration I have will work for an IB.

Could be fun. :)

[JonW]

UPDATE-

Well, I was posting questions about IB's over there at the Cult. I drew up a diagram of my room and Thomas seems to think the locations in my room are not workable.

Here's the diagram of the room:


http://members.roadfly.com/captainahab/floorplan1.jpg


I realize the IB position isn't perfect. But is it workable at all? Can things be fixed by adding in some time delays such that the sub and regular speakers will arrive at the listener at the same time?

Would it sound not perfect, but still better than just buying a box sub?

Not good news so far.

[JoeE SP9]

Where is your listening position? Your diagram shows a very large distance between your mains and your projected subwoofer position. The best position for a subwoofer is between the front 2 speakers. http://forums.audioreview.com/images/icons/icon6.gif

[Mr Peabody]

Infinite Baffle sub for the home is a new concept for me but I have some experience building car audio systems and in that Infinite Baffle woofers are designed differently that a typical box woofer. You may want to do some more investigating on which woofers to use on your project. I have also helped in PA speaker projects using Electro Voice drivers and the woofers had very specific parameters, even to the length of the port and diameter. Maybe this home IB is a whole new can of worms, but I wouldn't recommend using, just any, woofer as an IB sub.

[This Guy]

yeah you're gonna need a woofer(s) with a QTS near .71 and as much xmax as possible.

[JonW]

yeah you're gonna need a woofer(s) with a QTS near .71 and as much xmax as possible.

Sorry- I didn't understand any of that. Translation for a newbie?

[JonW]

Where is your listening position? Your diagram shows a very large distance between your mains and your projected subwoofer position. The best position for a subwoofer is between the front 2 speakers. http://forums.audioreview.com/images/icons/icon6.gif

Yeah, I know where the ideal IB position is. Unfortunately, that's not going to work here. Not sure where I'll have the main speakers- either at location A, B, or C. So I'm not sure if an IB will work here. Hmmm...


Mr. Peabody- Yeah, there are some woofers that seem to be favored by the IB crowd. I'm not yet sure why. Lots for me to learn here,

[kexodusc]

yeah you're gonna need a woofer(s) with a QTS near .71 and as much xmax as possible.

There's a bit of flexibility with IB's...you can go in the low .6's if you need too. I'd shoot for lower xmax to preserve sound quality. Get a bigger woofer instead of a high-xmax driver, or look for better sensitivity or more woofers if necessary. Too much happens as you start significantly increasing xmax, output increases, but sound quality deteriorates.

[This Guy]

I'd say look at the Dayton 15" IB, The xmax is around 14-15 mm and the QTS is around .6. But I don't know if IB would be good for this guy. The position for the sub is pretty far from the rest of the set up, i think he'd get better results with a boxed sub closer to his main speakers. If that 5' opening wasn't there it would be better.

[JonW]

Hey Guys,

Sorry, but I still don't know what you're talking about. I'm not yet up on the lingo here. For woofers, I was thinking about using 3 of the Ascedant Avalanche 15". The IB folks seem to really like these. Because of a wall under the hole (there in the basement) I can only fit woofers on 3 sides of the box.

[Timn8ter]

Hey Guys,

Sorry, but I still don't know what you're talking about. I'm not yet up on the lingo here. For woofers, I was thinking about using 3 of the Ascedant Avalanche 15". The IB folks seem to really like these. Because of a wall under the hole (there in the basement) I can only fit woofers on 3 sides of the box.

Hey Jon,
They are referring to the Qt of the driver which is a combination of the mechanical (Qm) and the electrical (Qe) suspension compliance. To put it simply, drivers with a high Qt, say over .6, are better able to maintain cone control in an infinite baffle application because they rely less on the air inside a box acting as a "spring" on the back of the cone for help.
As for Thomas' comments, I would agree. It may seem great at first but after a while you're going to get tired of the bass compression coming from someplace other than the soundstage created by your mains. If you can't get the IB reasonbly close to that point it may be best to look at another solution, especially considering how much you are about to invest.

[Mr Peabody]

I haven't heard an IB set up in the home but isn't any sub supposed to be set up to blend with the music and the location not be detected when listening? When the subs are in a IB there's no moving them, at least not without some major construction. Most of us with boxed subs have gone through much experimentation with placement of the sub in our room to get the best performance. This isn't possible with IB. Some subs have a phase control and many use SPL meters or other equipment for the perfect placement. If this IB project ends up being the wrong location in the room it could be an expensive folly.

[JonW]

Hey Jon,
They are referring to the Qt of the driver which is a combination of the mechanical (Qm) and the electrical (Qe) suspension compliance. To put it simply, drivers with a high Qt, say over .6, are better able to maintain cone control in an infinite baffle application because they rely less on the air inside a box acting as a "spring" on the back of the cone for help.

Got it. Thanks for the explanation.



As for Thomas' comments, I would agree. It may seem great at first but after a while you're going to get tired of the bass compression coming from someplace other than the soundstage created by your mains. If you can't get the IB reasonbly close to that point it may be best to look at another solution, especially considering how much you are about to invest.

Yes, good point. The hole is already there in the floor, I'm up for a DIY project, and I'm about to put together a whole stereo system. So the IB sounds perfect. However, if the placement is poor, it may not be a good idea. :( When I get home (I'm traveling at the moment) I'll have to see if I can do some testing on the location. I don't know anyone with a sub to borrow and I don't even have a stereo system to hook the sub up to. I've got some computer speakers at work- a Klipsch system with 4 speakers + sub and the sub is supposedly 160 W or something. I'll test the room with that, because it's all I've got. Then we'll see what I find. I certainly hope it's OK. But if it's not... And even if it sounds OK with my whimpy computer sub, I'm not sure that's a good test for whether or not I should build an IB, Hmmm...

[JonW]

I haven't heard an IB set up in the home but isn't any sub supposed to be set up to blend with the music and the location not be detected when listening? When the subs are in a IB there's no moving them, at least not without some major construction. Most of us with boxed subs have gone through much experimentation with placement of the sub in our room to get the best performance. This isn't possible with IB. Some subs have a phase control and many use SPL meters or other equipment for the perfect placement. If this IB project ends up being the wrong location in the room it could be an expensive folly.

You are correct. Not sure if an IB is for me, although I'd very much like it to be. Read my response to Timn8er above. I'll test the location with my small computer sub and see what I find. Hmmm...