IB by a door too leaky?
I want to experiment with an infinite baffle subwoofer. I'd like to put it in the corner of my lounge next to the door into a hallway. Would the fact that it's next to the door be an issue due to the less than perfect fit of the door in the frame causing a partial acoustic short circuit. Any thoughts/comments welcome. Basically I want to know if I'm wasting my time. Please stop me from cutting holes in the wall (it's only plasterboard studding) if you think it's a bad idea
I want to experiment with an infinite baffle subwoofer. I'd like to put it in the corner of my lounge next to the door into a hallway. Would the fact that it's next to the door be an issue due to the less than perfect fit of the door in the frame causing a partial acoustic short circuit. Any thoughts/comments welcome. Basically I want to know if I'm wasting my time. Please stop me from cutting holes in the wall (it's only plasterboard studding) if you think it's a bad idea
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It's that darn textbook picture that shows the back sound totally annihilating the front sound. Seems silly when you give it any thought.
Lots of folks who live in real rooms and produce wonderful sound with open baffles (and a variety of leaky enclosures) would say not to worry, or not to worry as much as some people do after looking at that textbook picture.
A typical room is full of reflections, phases of every angle, and eigentones large and small. As I've been arguing, think system-wise. That means putting together good components but the final consideration is sound at your chair. That also implies that there's no way to wrap up a satisfactory system without a digital signal processor.
B.
I'm one of those folks. I'm looking to fill in the bottom octave, and if a leaky infinite baffle has more in common with open baffle than a very large closed box or resonant enclosure I'm happy. I don't want to use huge amounts of power or EQ to get there......
How much area are we talking here with regard to the leaky area? With the door closed obviously.
For a typical well constructed door, I would say not a big deal. If you have a half inch gap across the bottom, that could start entering the realm of being an issue, but how big of an issue I can't say for certain.
It also depends on how large of an area the other side is. If it's a small closet, it would be more of an issue than a large open area.
Unless it's VERY leaky my gut feeling is it's probably going to give satisfactory results.
What woofer (and how many?) are you intending to use? Because you can't "tune" an IB "enclosure" you'll either have to use a woofer that naturally give you the response you want or force it with EQ.
For what it's worth, one of the best reasons to go IB IMO is that to get nice small enclosures for typical subs, you have to use powerful drivers. But since IB is basically a massive enclosure, you don't need strong motor drivers. This means you can use lots of cheap drivers for massive displacement and great results.
Also not that IB subs aren't a great option, but I rarely see people post about them here. You might find a better knowledge base at
ibsubwoofers.proboards.com
or
DIY Speakers and Subs - AVS Forum | Home Theater Discussions And Reviews
For a typical well constructed door, I would say not a big deal. If you have a half inch gap across the bottom, that could start entering the realm of being an issue, but how big of an issue I can't say for certain.
It also depends on how large of an area the other side is. If it's a small closet, it would be more of an issue than a large open area.
Unless it's VERY leaky my gut feeling is it's probably going to give satisfactory results.
What woofer (and how many?) are you intending to use? Because you can't "tune" an IB "enclosure" you'll either have to use a woofer that naturally give you the response you want or force it with EQ.
For what it's worth, one of the best reasons to go IB IMO is that to get nice small enclosures for typical subs, you have to use powerful drivers. But since IB is basically a massive enclosure, you don't need strong motor drivers. This means you can use lots of cheap drivers for massive displacement and great results.
Also not that IB subs aren't a great option, but I rarely see people post about them here. You might find a better knowledge base at
ibsubwoofers.proboards.com
or
DIY Speakers and Subs - AVS Forum | Home Theater Discussions And Reviews
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Hi, thanks for your thoughts and links, I've have a look at those.
The door has foam draught excluder around the frame and a brush like excluder at the bottom, so, from what you say, that's not likely to be an issue. The door is 18" from the corner of the room and this is where I'm planning to put the speakers.
The other side is a small hall by the front door and stairs to a small landing, so a decent area, I don't foresee any problem there.
I have an open baffle FAST set up with 4 12" drivers in two U frames crossed over at 125Hz that reach quite flatly down to 40Hz without EQ. I'm hoping to give them a little help below this.
The speakers I'd like to use are a couple of old KEF B139s that I have knocking around. They don't have a large power handling capability or xmas, but do have a low resonant frequency of between 20 and 25Hz. So I was thinking they may work quite well in IB with little or no EQ
The door has foam draught excluder around the frame and a brush like excluder at the bottom, so, from what you say, that's not likely to be an issue. The door is 18" from the corner of the room and this is where I'm planning to put the speakers.
The other side is a small hall by the front door and stairs to a small landing, so a decent area, I don't foresee any problem there.
I have an open baffle FAST set up with 4 12" drivers in two U frames crossed over at 125Hz that reach quite flatly down to 40Hz without EQ. I'm hoping to give them a little help below this.
The speakers I'd like to use are a couple of old KEF B139s that I have knocking around. They don't have a large power handling capability or xmas, but do have a low resonant frequency of between 20 and 25Hz. So I was thinking they may work quite well in IB with little or no EQ
If the Cult of the Infinitely Baffled don't know, it's unknowable and/or irrelevant
: Home | "Cult of the Infinitely Baffled" Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer design Established 1999
GM
: Home | "Cult of the Infinitely Baffled" Hear The Bass, Not The Box The definitive online resource for Infinite Baffle subwoofer design Established 1999GM
Hi. Yes I've been experimenting along those lines. This is how I have it at the moment. The cabinet is in the corner of the room, with the drivers (KEF B139) back to back. The dotted line is a slot that is firing through the wall into the hall. I wonder whether it might be better the other way round, ie box in the hall firing into the room? Also whether the slot is too small? It sounds ok at the moment, I have yet to measure. PS, my scale door v box is way out!
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I'm not sure those drivers will give you much output below 40Hz, though room gain might help get something you like. Qts is quite low, but you can tune that with a series resistor to get more output around Fs.
Piston Excursion calculator
Chris
Piston Excursion calculator
Chris
Fs is the spring-mass resonance of the cone and suspension, so wiring won't change it.
A series resistor reduces electrical damping a little, so Qes (and therefore Qts) goes up, giving you a flatter IB response.
Chris
Model it as a BP4 to find best overall slot area.
I'm with Ron, IME vibration losses are going to be > any 'wheezing' around a gasketed doorway, but with only a published 3.5 mm Xmax, 6 mm Xmech, you really need a hi-pass [TT rumble] filter to protect them, which in turn will help with vibration at higher SPL, though really need to brace the baffle wall with a layer [or more] of 3/4" [or thicker] drywall, MDF, PB or similar to lower its Fs below the driver's ability to excite it enough to matter.
Note that if you have a suspended ['floating'] floor like mine, then to a great extent you'll be 'chasing your tail' as the floor will still be the dominant problem as I learned the hard, expensive way, so no infrabass at high SPL for me till I either move or plow this one under and build a concrete foundation [preferably all construction] home/bomb shelter.
GM
Reading GM's good post, I think Scott (love that avatar) is back to pre-guessing about a half-dozen imponderables. That's the reality.
Time to measure the system. Wheezing or panel vibrations might show up in sloppy RTA curves. If the floor or walls are eating SPL, that may simply be a call for EQ.
But even if measurements are favourable, there are still sound qualities that are hard for us amateurs to measure. But measurements provide much better info than speculations.
BTW, was GM's comment about building a bomb shelter a veiled observation about US politics?
B.
Time to measure the system. Wheezing or panel vibrations might show up in sloppy RTA curves. If the floor or walls are eating SPL, that may simply be a call for EQ.
But even if measurements are favourable, there are still sound qualities that are hard for us amateurs to measure. But measurements provide much better info than speculations.
BTW, was GM's comment about building a bomb shelter a veiled observation about US politics?
B.
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The Vas is 164 litres, pretty high? The cone is expanded polystyrene.
I'm using a Rane graphic to deal with the peaks I have and it also has an adjustable HP filter which is handy for the subsonics. I'll try some bracing. I'm getting wall vibration at around 70Hz, but 40Hz and below there isn't any strangely.
The floor is 4mm cork tiles on concrete on bedrock (seriously) so no problem there.
Measurements is where I struggle. All I have is on-line tone generator, Panasonic WM-61A mic and homemade amp into an oscilloscope. I have been told this is useless but I'm not sure why, surely it is adequate to do relative comparisons of SPL?
At one time (long ago) I had nothing but an EICO scope, Heathkit audio oscillator, and twin-tee filter for 68 Hz I made myself. Not a bad place to start.
Almost any mic will work just fine and you are 99% pro for us$60. REW works on Macs as well as on more primitive OSs and is honour ware. You'll be gobsmacked delighted.
Ben
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