pinkmouse said:
Alas, I already tested that theory. It is mounted directly upon the floor joists. Let us assume that the dimensions of the room are not user-definable.
However, my limited funds can be spread over the course of many months and years, so much can be done apart from making any change to the dimensions.
Dave
pinkmouse said:
Aha! Indeed....
Upon examination, I believe the rafters run parallel to the length of the room. That's very strange, too, because the rafters elsewhere in the basement are longways.
I suspect the carpenter felt that the living room, which is precisely the same area as the basement directly below (my auditioning room), needed shorter runs of wood, eh?
Dave
planet10 said:
That's correct. I was trying to do the math on that. So we're talking about an effective 7'5" or ~90 inch height now. In addition, those solid joists will be helping diffuse standing waves, no?
Help me work on my Canadian-speech, eh. I actually have to recover my French skills, which I lost in a closet a few years ago....
Oops, getting myself off-topic.
Dave
kneadle said:
Not standing waves, but diffusuion of frequencies on the same order of size as the joists & spaces in between.
Use of styrofoam blocks which will be mostly transparent to the long waves, might help diffuse the smaller waves better.
That stereo-typed Canadian speech pattern is not all that common at this end of the country....
dave
It's just a wall size membrane that has an Fs of some frequency yet to be determined, though a simple calc of 565/22 = 25.68Hz is probably close, so would be made using PB or MDF and broken up into easy to handle stock widths. The side walls will be similar and angle out to reduce slap echo, like a cinema or concert hall layout, from say 8ft at the front (to accommodate a decent sized 110" diagonal screen) on out to the 11ft width at the false wall absorber at some room ratio distance, such as ~17.8ft, leaving a ~4.2ft deep bass trap/storage area, though access to it would need to be from some other way than the false wall.
Another option would be to extend the tapered walls all the way to the rear and build a peaked (viewed from the top) basstrap to diffuse/absorb. Not as effective overall, but still much better than nothing and a nifty conversation piece. This makes the rear wall still basically unusable except for mounting rear channel speakers, but open style record/whatever racks could be placed along the walls for ~easy access.
GM
Another option would be to extend the tapered walls all the way to the rear and build a peaked (viewed from the top) basstrap to diffuse/absorb. Not as effective overall, but still much better than nothing and a nifty conversation piece. This makes the rear wall still basically unusable except for mounting rear channel speakers, but open style record/whatever racks could be placed along the walls for ~easy access.
GM
I can recommend a good book:
Although it's a home theatre book, it deals with room acoustics / speaker interaction very well
Here's my suggestions (some of them heavily influenced by that book):
* bass may be the most difficult problem
* don't make a room too dead as a dead room sounds boring and small rooms can very easily become dead as it is more difficult to build up reverberation - too much is bad news but too little isn't a good thing either
* consider the room acoustics and the speakers as a system and consider how to deal with room modes, and the balance of acoustic absorbers and diffusers
* dipoles may work well
* also consider sound isolation through the ceiling
With length to spare you can look into helmholz resonators to flatten the rooms response. You can also partition off a small space at one end with designed in leakiness to act as a bass absorber. You can also build walls with a flexible mounting system so the internal walls absorb the bass and give a smoother response. This technique is discussed in the book.
Dipoles might be a good alternative to extensive bass treatment in the room. If they are full range dipoles then you have the added benefit of needing less overall (if any at all) room treatment and this lets you have a room that is more live in character. You could use acoustic diffusers selectively to scatter early reflections on the ceiling and walls. I'd use diffusers on the ceiling and remove the ceiling tiles as suggested. You might line the joists and the underside of the floor above with some timber in some way that decouples vibrations to improve isolation - I know it's not much but you want to do as much as you can without lowering the ceiling significantly. I'd use a combinatin of absorbers and diffusers on the end walls.
Although it's a home theatre book, it deals with room acoustics / speaker interaction very well
Here's my suggestions (some of them heavily influenced by that book):
* bass may be the most difficult problem
* don't make a room too dead as a dead room sounds boring and small rooms can very easily become dead as it is more difficult to build up reverberation - too much is bad news but too little isn't a good thing either
* consider the room acoustics and the speakers as a system and consider how to deal with room modes, and the balance of acoustic absorbers and diffusers
* dipoles may work well
* also consider sound isolation through the ceiling
With length to spare you can look into helmholz resonators to flatten the rooms response. You can also partition off a small space at one end with designed in leakiness to act as a bass absorber. You can also build walls with a flexible mounting system so the internal walls absorb the bass and give a smoother response. This technique is discussed in the book.
Dipoles might be a good alternative to extensive bass treatment in the room. If they are full range dipoles then you have the added benefit of needing less overall (if any at all) room treatment and this lets you have a room that is more live in character. You could use acoustic diffusers selectively to scatter early reflections on the ceiling and walls. I'd use diffusers on the ceiling and remove the ceiling tiles as suggested. You might line the joists and the underside of the floor above with some timber in some way that decouples vibrations to improve isolation - I know it's not much but you want to do as much as you can without lowering the ceiling significantly. I'd use a combinatin of absorbers and diffusers on the end walls.
Ethan Winer
I'm surprised that many people still haven't heard of Ethan Winer's Real Traps, which essentially make Helmholtz resonators obsolete. Allow me to provide this forum the service of linking you to Ethan Winer.
http://www.ethanwiner.com/basstrap.html
http://www.realtraps.com/
http://www.realtraps.com/facts.htm
I suppose there is a giant gulf between hi-fi aficionados and studio aficionados, but this stuff is for real, and applicable to hifi and studio mixing.
Dave
I'm surprised that many people still haven't heard of Ethan Winer's Real Traps, which essentially make Helmholtz resonators obsolete. Allow me to provide this forum the service of linking you to Ethan Winer.
http://www.ethanwiner.com/basstrap.html
http://www.realtraps.com/
http://www.realtraps.com/facts.htm
I suppose there is a giant gulf between hi-fi aficionados and studio aficionados, but this stuff is for real, and applicable to hifi and studio mixing.
Dave
Re: Ethan Winer
Perhaps I'm missing something but to me they look the same as all the other panel absorbers out there. They don't do the same job as a Helmholz resonator. Any treatment that deals with absorbing bass will tend to flatten the room response by taming the impact of the room modes. Using a helmholz will go that next step by providing what is effectively acoustic eq, which will work for a larger area than electronic eq. To do it right means being able to make room response measurements.
I do think some hifi enthusiasts could benefit by focusing more on the room and less on hifi voodoo, but I also think it's best to judge arguments on their merits rather than be misled by hifi vs studio distinctions.
I'm not sure what you mean by maximise the length of the room. Perhaps you could elaborate ...
If I understand correctly, dipoles excite room modes less and in a different way. The difference has to do with both the figure of 8 polar response as well as velocity vs pressure mode. One thing I haven't seen discussed is bass traps and dipoles used together. I suspect that corner bass traps of the cylinder type would be virtually useless with a dipole, and this may also apply to other types of bass traps to a degree. Whether this applies to a helmholz is another matter - I suspect if placed correctly they would still work.
An interesting solution would be to start with dipoles and do in room measurements. Then if smoother bass is desired, treament and eq could be experimented with. I can see that bass could be the most difficult problem in your room as there would be so much more bass energy stored in the room. This suggests to me that dipoles could well be the way to go.
kneadle said:
Perhaps I'm missing something but to me they look the same as all the other panel absorbers out there. They don't do the same job as a Helmholz resonator. Any treatment that deals with absorbing bass will tend to flatten the room response by taming the impact of the room modes. Using a helmholz will go that next step by providing what is effectively acoustic eq, which will work for a larger area than electronic eq. To do it right means being able to make room response measurements.
kneadle said:
I do think some hifi enthusiasts could benefit by focusing more on the room and less on hifi voodoo, but I also think it's best to judge arguments on their merits rather than be misled by hifi vs studio distinctions.
kneadle said:
I'm not sure what you mean by maximise the length of the room. Perhaps you could elaborate ...
If I understand correctly, dipoles excite room modes less and in a different way. The difference has to do with both the figure of 8 polar response as well as velocity vs pressure mode. One thing I haven't seen discussed is bass traps and dipoles used together. I suspect that corner bass traps of the cylinder type would be virtually useless with a dipole, and this may also apply to other types of bass traps to a degree. Whether this applies to a helmholz is another matter - I suspect if placed correctly they would still work.
An interesting solution would be to start with dipoles and do in room measurements. Then if smoother bass is desired, treament and eq could be experimented with. I can see that bass could be the most difficult problem in your room as there would be so much more bass energy stored in the room. This suggests to me that dipoles could well be the way to go.
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