It seems that amongst the many cans of worms I'm naively opening with my intended 3-way project is the room layout, so i thought i'd start a thread on that to add to all the other issues being juggled.
Its a standard living room, rather than a dedicated cinema or listening room, and has a number of compromises. In particular my speakers are either side of the TV, which is mounted on the chimney-breast - which means they are stuck in alcoves less than 1m wide and around 35cm deep. This clearly isn't ideal but doesn't seem to be 'too' bad with my current modest bookshelf speakers, theres a little boominess occasionally but then they aren't noted for their impressive bass.. my 3-way project is partly intended to correct that so i woulkd expect to have more of an issue. I don't want to bring the speakers out into the room - partly to keep them at the same distance as the TV and partly because its a small room and space is limited, but they could probably come forward several inches if necessary.
(see image below)
I've started reading The Acoustics and Psychoacoustics of Loudspeakers and Rooms by Floyd Toole. Its pretty wide ranging and so not the fastest to get to the point, but he has a section comparing a bookshelf speaker sitting in a sort of shelf-type recess vs packed in with insulation vs flush with the wall (such as in a hard flush panel covering the recess), and its clear that the recess does unfortunate things to the smooth propagation of sound. The conclusion appears to be that its better to have it either flush mounted in a panel or failing that on a panel (where reflections are close enough to be < half a wavelength) rather then in a recess.
If its a problem I was considering bridging the alcoves flush with the chimney and having the speakers flush with it and the cabinets behind - possibly the whole speaker or perhaps just for the bass driver (in which case I would disguise it as a sort of built-in cupboard with the mid and tweeter appearing to be a two-way sitting on top, just above the bass driver). Or alternatively, I could look at a wide baffle design of enclosure like Troel's Poor mans Strad or the Stradivari placed a few inches forward, and hope this would push the sound into 2pi space before it has much chance to interact with the alcove.
So what I'm interested in knowing is if I will actually have a likely problem here, as I believe, and if so are my ideas any good or are there better ways of dealing with it?
Cheers
kev
Its a standard living room, rather than a dedicated cinema or listening room, and has a number of compromises. In particular my speakers are either side of the TV, which is mounted on the chimney-breast - which means they are stuck in alcoves less than 1m wide and around 35cm deep. This clearly isn't ideal but doesn't seem to be 'too' bad with my current modest bookshelf speakers, theres a little boominess occasionally but then they aren't noted for their impressive bass.. my 3-way project is partly intended to correct that so i woulkd expect to have more of an issue. I don't want to bring the speakers out into the room - partly to keep them at the same distance as the TV and partly because its a small room and space is limited, but they could probably come forward several inches if necessary.
(see image below)
I've started reading The Acoustics and Psychoacoustics of Loudspeakers and Rooms by Floyd Toole. Its pretty wide ranging and so not the fastest to get to the point, but he has a section comparing a bookshelf speaker sitting in a sort of shelf-type recess vs packed in with insulation vs flush with the wall (such as in a hard flush panel covering the recess), and its clear that the recess does unfortunate things to the smooth propagation of sound. The conclusion appears to be that its better to have it either flush mounted in a panel or failing that on a panel (where reflections are close enough to be < half a wavelength) rather then in a recess.
If its a problem I was considering bridging the alcoves flush with the chimney and having the speakers flush with it and the cabinets behind - possibly the whole speaker or perhaps just for the bass driver (in which case I would disguise it as a sort of built-in cupboard with the mid and tweeter appearing to be a two-way sitting on top, just above the bass driver). Or alternatively, I could look at a wide baffle design of enclosure like Troel's Poor mans Strad or the Stradivari placed a few inches forward, and hope this would push the sound into 2pi space before it has much chance to interact with the alcove.
So what I'm interested in knowing is if I will actually have a likely problem here, as I believe, and if so are my ideas any good or are there better ways of dealing with it?
Cheers
kev
Attachments
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Some quick and easy changes that I suggest are in the pic. Others than sofa switching can be done only when listening "seriously" 😎 Obviously the room should have some half-filled bookshelves, thick carpet, wall clothes to reduce reverberations (I guess there are but not drawn to pic).
Please study/simulate positioning of speakers and mic/listener here (enable Java) hunecke.de | Loudspeakers Calculator
Cheers,
Juha
Please study/simulate positioning of speakers and mic/listener here (enable Java) hunecke.de | Loudspeakers Calculator
Cheers,
Juha
Attachments
It looks like you have the opposite of a problem: you have the option to soffit mount speakers which is pretty much ideal.
I would echo Juhazi's point about moving your head away from the back wall when settling in for a good listen.
Soffit mounting the speakers will efficiently drive the lengthwise room mode (but so will the current location pretty much) putting room treatment behind your head fairly high on the list of things to consider. But only do this after measuring what your room is doing.
Many thanks chaps! Yes my head being too close to the rear wall is one of the deficiencies (of the room, not my head!). It wouldn't be practical to move the sofa forward permanently but I hadn't actually thought that I could move forward temporarily for serious listening sessions - of course I could; doh!
Possibly i could do something similar with the speakers too - they're likely to be heavy but not un-moveable. I do very much like the soffit idea though - I've not searched for that term before, I was trying "wall' and just getting loads of stuff on enclosure/box walls. It would look very neat and hardly intrude into my modestly sized room. Probably the big negative would be if it looked a bit too 'dedicated' for a general purpose living room. But possibly (if built strongly enough to stop things vibrating) I could use flush glass doors to form some other areas of the soffit pannel with built-in bookshelves behind, and so increase the WAF.
I guess this would inform my choice of speaker design; the width is no problem but depth should ideally be relatively shallow - the opposite of quite a few modern designs - and there may not be any noticable baffle-step. I wouldn't have much opportunity to affect sound by the shape of baffle though, so should I be looking for drivers with an inherently smooth/flat FR chart?
Cheers
kev
Possibly i could do something similar with the speakers too - they're likely to be heavy but not un-moveable. I do very much like the soffit idea though - I've not searched for that term before, I was trying "wall' and just getting loads of stuff on enclosure/box walls. It would look very neat and hardly intrude into my modestly sized room. Probably the big negative would be if it looked a bit too 'dedicated' for a general purpose living room. But possibly (if built strongly enough to stop things vibrating) I could use flush glass doors to form some other areas of the soffit pannel with built-in bookshelves behind, and so increase the WAF.
I guess this would inform my choice of speaker design; the width is no problem but depth should ideally be relatively shallow - the opposite of quite a few modern designs - and there may not be any noticable baffle-step. I wouldn't have much opportunity to affect sound by the shape of baffle though, so should I be looking for drivers with an inherently smooth/flat FR chart?
Cheers
kev
In your diagram you appear to have about 10" depth?
If you soffit mount your avoid issues to do with "baffle step correction" and other wriggles in the response due to diffraction from the cabinet. If you use an active crossover you avoid the compromises of a passive crossover. I am not sure there is much of left of existing designs to follow. The choice of drivers will have been influenced by things like sensitivity and other passive crossover constraints that you do not have.
Another option you would seem to have is to place the speakers in the corners. There can be benefits doing this if the walls around the speakers are smooth although you are now efficiently driving another room mode and the stereo image might be too wide when watching TV. You would also probably need to use waveguides for the higher frequencies. Here is a bit of discussion on the subject. This is not intended to be a recommendation but more checking that you have considered the pros and cons of both locations.
Thanks yet again, Andy. Thats a very good point; by the time I've gone active, avoided baffle step, changed the front baffle and probably the proportions of the enclosure, then I'd essentially only have the drivers and perhaps enclosure volumes & tuning from any existing design. I think this may help my decision on what to do; I could go for something conventional of simple design, and rely on the soffit to fulfill my cravings for something a bit unique and interesting for my DIY efforts. (Though I guess it wouldn't hurt if I could find drivers known to work in an existing project too, either as a back-up or for future flexibility.)
I hadn't really considered corner speakers as I'd been seeing them as alcoves, but yes aside from the intrusion from the corner of the chimney breast they are also room corners so thanks for the suggestion - I'll read up on such speakers. I've seen some things on them in passing and they seem interesting, but I sort of got the impression perhaps a bit unconventional for my first serious project. You're dead right though - I should at least consider them, rather than avaoiding it through ignorance.
Cheers
kev
I hadn't really considered corner speakers as I'd been seeing them as alcoves, but yes aside from the intrusion from the corner of the chimney breast they are also room corners so thanks for the suggestion - I'll read up on such speakers. I've seen some things on them in passing and they seem interesting, but I sort of got the impression perhaps a bit unconventional for my first serious project. You're dead right though - I should at least consider them, rather than avaoiding it through ignorance.
Cheers
kev
Hi Kev, thinking about the room is probably going to put other things into perspective somewhat 😉 I did some measurements in room recently to try and work out whether there was anything (simple) I could do to improve things.
I ended up repositioning the speakers a bit and got a slight improvement. The main problem is the 4M length of my room. It causes some big nodes, I suspect you will see the same. Using the simulator in REW shows what I should expect and it certainly looks a lot like what the in room FR curve looks like.
I've attached a plot. Blue is the FR of one of my speakers measured outside. Green is both speakers playing taken at the listening position (with mic carefully positioned to be almost exactly equidistant from each speaker).
As you can see the room changes things a bit!
The graph looks a bit scarier than it really is due to the 40db scale, and it is only 1/16th octave smoothed.
There wasn't much I could do with speaker positioning with my particular room. It is nominally 4 X 5M but one side of that is a walk through area so it is more like 4 X 4 for where the funiture can go. I think in reality some sort of absorbtion on the wall behind the sofa would be the most effective thing for me, and certainly when I have put big cushions behind my head on the sofa it seems to make a bit of a difference.
I'll have to check out the room sim program that Juhazi linked. REW is ok and it helped me to reposition the speakers a bit better, but my room is a bit asymetric due to walkthroughs to other rooms and a staircase so it would be interesting to see something else that allows for something a bit more complex.
Tony.
I ended up repositioning the speakers a bit and got a slight improvement. The main problem is the 4M length of my room. It causes some big nodes, I suspect you will see the same. Using the simulator in REW shows what I should expect and it certainly looks a lot like what the in room FR curve looks like.
I've attached a plot. Blue is the FR of one of my speakers measured outside. Green is both speakers playing taken at the listening position (with mic carefully positioned to be almost exactly equidistant from each speaker).
As you can see the room changes things a bit!
The graph looks a bit scarier than it really is due to the 40db scale, and it is only 1/16th octave smoothed.
There wasn't much I could do with speaker positioning with my particular room. It is nominally 4 X 5M but one side of that is a walk through area so it is more like 4 X 4 for where the funiture can go. I think in reality some sort of absorbtion on the wall behind the sofa would be the most effective thing for me, and certainly when I have put big cushions behind my head on the sofa it seems to make a bit of a difference.
I'll have to check out the room sim program that Juhazi linked. REW is ok and it helped me to reposition the speakers a bit better, but my room is a bit asymetric due to walkthroughs to other rooms and a staircase so it would be interesting to see something else that allows for something a bit more complex.
Tony.
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Thanks Tony, thats most interesting, especially as I have a similar room length. There certainly is a big difference there! Damping behind the listening position sounds like a cunning plan too, especially for those occasions when I can't pull the sofa forward. Not certain what i could do about room nodes but even if the answer is nothing then its still useful to know whats going on
I've not yet tried the the room sim program that Juhazi linked to; I seem to be having trouble with my Java plugin. But if I can get that sorted I'll definitely give it a go, as the description looks encouraging.
Cheers
Kev
I've not yet tried the the room sim program that Juhazi linked to; I seem to be having trouble with my Java plugin. But if I can get that sorted I'll definitely give it a go, as the description looks encouraging.
Cheers
Kev
About that sim, It is a great learning tool to study "what if". It acccepts only a rectangular room. The sims don't match my HT room very well, but generally rather close. The effect of moving the mic/head is often more important than moving the speaker! some 10cm difference in height means a lot too! Actually it made me a little frustrated, because many of the "best" positions were impossible/impravtical for people in the room, eg. placing the sub in the middle of floor!
Happy simulation sessions!
Happy simulation sessions!
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Absolutely agree with that.
I wish I'd be in a situation where I could soffit mount or quasi-soffit mount mine!
You might want to read up on how to build bass traps (there are as many kinds as there are different types of woofer enclosures) to go behind your listening position.
If you build them yourself you can make them quite unobtrusive, pretty even.
Hi Kev, the big spike at a bit below 50Hz is the mode from the room length. I think that the asymmetry of the room throws it off a little bit from the Sim (only by a few Hz) I only get that problem with the right speaker, measurement on the left speaker doesn't have the big peak because it is beside the walk-through so to the left of the speaker is actually a cavity of at least 4 square M behind.
I would think in your room the sims will be more accurate, though the bay window may have some interesting effects, working like a parabolic reflector potentially?!
Since I still had the sim from my room open I just changed it slightly to match your room and the result is attached. I put in an arbitrary 40Hz f3 and 2.4M for ceiling height.
Tony.
I would think in your room the sims will be more accurate, though the bay window may have some interesting effects, working like a parabolic reflector potentially?!
Since I still had the sim from my room open I just changed it slightly to match your room and the result is attached. I put in an arbitrary 40Hz f3 and 2.4M for ceiling height.
Tony.
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I got the plug-in working now and tried the online simulator. Obviously its quite simplistic and I can't get very close to my intended speaker designs but it is still very interesting to quickly/easily see how the speaker and mic locations change things. I also do get a 20dB spike in SPL at between 30 and 50hz, as you mentioned, Tony. This diminishes as I move the mic forwards to the centre of the room and increases again if I continue on towards the front of the room. My current speakers start to crap out before they get that low, but my intended 3-ways certainly shouldn't, so that may be something to consider 🙁
Thanks very much for testing out my room too - I've not tried that simulator but it looks very useful! The peak is still there but not quite so scarily large as with the more general online sim above.
Cheers
Kev
Thanks very much for testing out my room too - I've not tried that simulator but it looks very useful! The peak is still there but not quite so scarily large as with the more general online sim above.
Cheers
Kev
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Thanks! Its taking me a little while to adjust my thinking from a free standing speaker to building things into the room, so support for the idea is most reassuring. The more I read about it the more I like the idea though so it may well happen if I can achieve a suitable WAF.
Thanks for the thoughts on the rear bass trap, too. Most of the ones I've seen online have been pretty obtrusive slabs of black foam or boxes but a quick search shows some recessed into false walls and/or disguised as art/pictures so you're quite right - I should be able to do something acceptible. In fact my sofa has a fairly low back with no head-rests - I could potentially make a sort of deeply patted head-board affixed to the wall.. hmm.
Actually, I was also intending to build false walls with insulation behind for thermal reasons - I don't know what the building/fire regs say about the idea, but if there is some more acoustically transparent alternative to the plaster board and if I use a softer type of thermal insulation I could possibly combine the two ideas in one. Or failing that, I could leave a recess in my thermal wall and fill just that area with a bass trap.
Cheers
Kev
If you were already thinking of thermally insulating the wall behind you look into limp membranes type bass traps as there is the possibility of killing two birds with one stone.
This stuff might be good for the membrane part:
Acoustistop 1.2Mx3M Sound Blocking Sheet at Studiospares
But do read up on it yourself as I'm not an acoustician and it's been a few years since I seriously looked into that.
I would have thought that soffit-mounting has a much greater WAF than any free-standing speakers since it allows you to make the speakers to almost completely disappear visually.
Btw cloth-covered sofas are excellent absorbers/bass traps in their own right. Leather ones not so much though.
This stuff might be good for the membrane part:
Acoustistop 1.2Mx3M Sound Blocking Sheet at Studiospares
But do read up on it yourself as I'm not an acoustician and it's been a few years since I seriously looked into that.
I would have thought that soffit-mounting has a much greater WAF than any free-standing speakers since it allows you to make the speakers to almost completely disappear visually.
Btw cloth-covered sofas are excellent absorbers/bass traps in their own right. Leather ones not so much though.
Trapping bass is not easy using absorption alone. I have tried using several bags of acoustic rockwool (over 100 cubic feet) along the ceiling and down the corners behind the speakers. The effect was worthwhile but not very practical, and I've been able to maintain good results after removing some of this by paying more attention to room placement.
Bass trapping is still a good thing. It would be most effective if the walls were transparent (obviously 😉) and one way toward this end is to use panel absorbers. A look through some of the threads here would suggest that false walls installed to acoustic specs is one of the best ways to achieve this.
Bass trapping is still a good thing. It would be most effective if the walls were transparent (obviously 😉) and one way toward this end is to use panel absorbers. A look through some of the threads here would suggest that false walls installed to acoustic specs is one of the best ways to achieve this.
You might find some worthwhile info here:
Acoustics/Treatment Reference Guide - LOOK HERE! - Gearslutz.com
Acoustics/Treatment Reference Guide - LOOK HERE! - Gearslutz.com
Directivity is the other side of absorption, used together they can make things easier. It begins with the speakers. You could improve this with something as simple as radiusing the edges. You could even transition them (radius them back) onto the walls.
At the lowest frequencies you can add a sub whose only purpose is to negate some of the room induced problems.
At the lowest frequencies you can add a sub whose only purpose is to negate some of the room induced problems.
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