Axiom Home Page Forums General Discussion Technical Questions Acoustics in a loft

I'm a few months away from moving into a new house, currently under construction. The house is a 1-1/2 story with the living room, kitchen and a couple of bedrooms on the ground floor plus a ~500 square foot loft built under the roof, ie the walls angle in at 45 degrees. A rough layout is attached. There is a full basement with decent windows but not planning to finish it (no $$) for a year or two. The basement will have room for a couple of extra bedrooms plus a couple of areas for rec room / family room.

The question is where to put the HT/music system before the basement is finished. There are two options -- the living room (in white at the left end of the drawing) or the loft. The living room isn't a great choice because most of the walls are windows down below waist level so the speakers would end up blocking windows.

The loft is about 23x25 feet but almost half the space is <6 foot headroom. The roof angles down with the peak running from left to right, plus there are two alcoves (marked by angled lines) where the roofline can "grow" into the front hall (below) and bedroom (above) parts of the "cross".

The result is a high central area with four alcoves, one of which opens into the cathedral ceiling over the living room. I'm planning on putting the piano over in one of the alcoves (top), and the HT in the one on the right. Entry is via a bridge from the top of the stairs at the bottom of the picture. Wall/ceiling finish is planned to be painted drywall.

So... what are the acoustics gonna be like ? I don't even know how room modes are going to work if everything is at a 45 degree angle. Reflections off the wall/ceiling seem like a potential problem so I might need treatments there.

Guess I'm mostly trying to get a feeling for what the LF frequency response is going to be like. Is this going to be a dream room or a nightmare ?

Maybe this pic will make more sense. I'm trying to figure out if I should be looking at acoustic treatments before the wall coverings go on, and/or if I should be switching part of the loft from drywall to T&G wood etc...

Main concerns are (a) I have no clue how smooth or rocky the bass response will be, and (b) it seems to me I'm going to need some kind of reflection control on the walls but since they're at a 45 degree angle I can't exactly hang things, might need to built it in.

Thanks,
JB

OK, construction is far enough along now that I have pics. The insulation should be going into the rafters soon so I need to figure out what to put on the angled walls. Plan of record is drywall, but no idea how bad an idea that is going to be.

There are some options like perforated panels which provide some absorbtion, but I'm guessing that I want an airtight wall covering so that I don't get air leaking out the top of the house.

Here are a couple of pics to give an idea of the size and shape. You can see that the alcoves aren't all that deep -- if I had to treat a couple of reflection points that would be OK but if I had to treat the whole surface after construction I would feel like a real idiot.

Here's a shot of the alcove where the HT will be going. The piano will be in the alcover going off to the left. I think I drew the speakers too big (M80 size or larger, maybe talking to Dennis too much) -- the peak of the roof is about 12 feet high and the room is about 22 feet wide at floor level.



Here's a view in the other direction, looking off the end of the loft into the space above the living room. The area is open on this end and also off to the left, overlooking the front hall.



Any suggestions on wall coverings greatly appreciated. I really don't know what to do here... also anyone who even vaguely remembers a discussion about modelling the acoustic performance of triangular shapped rooms please speak up

Thanks,
John

Here's one more picture to show the other interesting challenge -- the loft are is REALLY open. This shot is from the living room looking towards the front hall. You can just see the right hand side of the HT area in the top left corner of the picture. The loft volume is just under 4000 ft3 but it opens into... oh... about another 6000 ft3. I'm thinking a bigger sub...

Very nice, John! I'm horribly envious, of course.

I dunno about the acoustic stuff John, but I will tell you that is going to be one awesome crib from the looks of the pictures!

In reply to:

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The loft volume is just under 4000 ft3 but it opens into... oh... about another 6000 ft3. I'm thinking a bigger sub...

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I'm thinking M80s

Thanks, guys. It's not a real big house (these three pictures show about 80% of the house, the only thing not shown is the master bedroom) but I do like the way the design worked out. When you meddle with a design you end up living in fear while the crews are building... hoping you didn't muck it all up too badly. As it turned out I think I got real lucky -- a couple of desperate last-minute decisions (usually after staying up all night worrying about the design) came together pretty well.

I have been wondering about M80s, but my thinking is that since the loft opens out into... well, into the entire house... there are going to be some practical limits on how loud I can play up there. I'm hoping M60s will be enough for reasonable SPLs but I agree that Dennis' system would not be overkill for that area.

The bank is already having kittens so I don't think a change order adding 5 M80s and a stack of Halos would go over too well

Yeah, you should definitely be looking at power amps. I'm not sure how much the M60s can handle, but... Needless to say, I wouldn't try the M2s in there!

I'm also not sure what dB you usually listen at.

Oh yeah! That's going to be nice! I'm thinking M80's too though.

>>I'm also not sure what dB you usually listen at.

About 20 dB less than Dennis (Tharkun), apparently . Seriously, I usually listen to music around 80dB, movies around 85dB, "really loud" music can be up around 95dB. The M2s can (just) do that with a good sub in a smaller room but they sure aren't going to make a dent on this room.

So, like, what should I cover the walls with, huh ?

I'm wondering if you're not going to get some weird resonance out of the piano. Being a guitar player, I know nothing about these things. Does having the key cover closed just kill everything, or do you still get the occasional hum?

I am actually a bit concerned about resonances off the piano. Right now the HT is in the basement and the piano is in the living room so I don't get a chance to hear them together.

The only saving grace is that I was originally planning on putting the HT down in the basement... until two months ago when I suddenly realized that I wasn't planning to finish the basement yet due to budget concerns, so where the heck am I gonna put the HT ?

I'm not planning on playing the HT real loud so hoping it won't be a concern... and if it is a real problem then I can move the HT down into the basement in the future after I save some more pennies...

Thanks !!

John:
I've been gone for the weekend and have a lot to do tonight. But I'm skimming through the forums and came across your new photos here. Nice, nice place. Type of house I dream of! So nice, I showed the photos to Joyce and she said "Will those windows effect his projection system?"

Any question why I love her? And...... will it?

John
It certainly looks like it will sound good.
Looks like a place to be VERY proud of.

>>So nice, I showed the photos to Joyce and she said "Will those windows effect his projection system?" Any question why I love her? And...... will it?

You are a lucky man.

There will be a bit of a problem on summer evenings because the setting sun will wash across the seating area. The screen will actually be in that triangular alcove (about 18 feet deep at the top, 6 feet deep at the floor) which should block light from the screen unless I have a lot of fat people in white shirts watching the movie.

You did get me thinking about wall finishes on the left hand side some more. They probably need to be darker (or more "woodish" ) than I first thought. Excellent timing there !!

I should mention that Dennis is doing a great job of convincing me to finish the angled walls in T&G pine rather than drywall... while my real estate agent (and good friend, part of the "design council") is pushing hard for drywall to keep the place bright and boost resale value

I have my HT in my loft until I finish the HT room in the basement. One thing for certain, is that sound carries to the great room below. When the youngin is watching something upstairs, even at very low levels, it is very distracting downstairs. I suspect you’ll have the same problem. And for your reference, my HT speaker system is a POS Bose system with those little cubes, so I can’t imagine having a need for my M80’s up there. But the other side to this, is you could listen to stereo downstairs if you wish. The sound will definitely carry. As far as pine vrs rock, I have T&G knotty pine on all my ceilings, and rock on the gable walls in my log home. I used a clear latex wood coating with a satin finish on the pine. It is not dark at all. Actually, if anything, it has a slight yellow tint to it and it reflects light from the windows quite well. Even at night when the sun’s down, the house is still light and not dark at as one would expect. With the gables being rock, painted off-white in a semi gloss, the house is unusually bright and airy. I have a lot of windows, which help too.