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Room Problem Improvement Question: Over a Garage

My current listening space is a second story room located over a 3 car garage and about 18-20'x30' that is a 2x4 stick construction supported by 2 microlam beams that run over the garage, parallel to the cars parked below, supporting the joists and 3/4inch subfloor beneath it. The surface is thin pile carpet with a thin pad under that.

The previous owners finished the space themselves and as such did not insulate at all between the floor joists to the uninsulated concrete garage underneath. The Garage ceiling below is about 10 ft and has blueboard with plaster over it.

Acoustically speaking, this is not a bad space, with ceilings being around 8' and is actually one of the better listening spaces I've had in my last 3 houses, even though on the left wall is a 45degree slant coming out around 3 feet running a good part of the length of the long wall next to my left speaker. I get great depth and fairly decent imaging and tonal balance, but I have floors which leak a considerable amount of bass and are INCREDIBLY SPRINGY! I can be walking softly on the other side of the room and my lead and sand filled Billy Bags rack cannot stop my needle from bouncing on a record! Also, I'm concerned about room nodes and overwhelming the space with all the sympathetic vibrations/resonances going on all at once, and even some of the reverberation from sound leaking down, bouncing off concrete then coming back up.

I am getting some very full range very dynamic and very heavy loudspeakers delivered in August and am concerned about this enough to begin getting quotes from builders for some kind of fix before their arrival.

Some of the ideas I've been given include:

-Spraying Icynene foam between the floor joists from the garage below to fill the spaces that are uninsulated

-Placing another layer of subflooring with a product called Advantech, which is a type of OSB that is far heavier than 3/4" subfloor then resurfacing with either:

a) Hardwood or
b) Another carpet or the same one if it can be salvaged.

- Just placing hardwood over the 3/4 inch subfloor and call it a day.

- Move the party to the 3car garage below which would entail getting HVAC systems,carpeting as well as walling off my garage doors and dealing with my wife having to park outside during the cold snowy winters and rain.

Any ideas on what to do in this type of a space? Has anyone had a similar problem with a room over the garage? The span is so long (23 ft) that I think it may be a lost cause and that adding subflooring ($2k) plus carpeting ($3k) may not even do the trick since it may be the floor joists below that are causing the problems.

My question is if anyone out there has done this type of project, what were the results and should I give it a try or just wait and see what happens when the new speakers arrive in August? It may be impossible to move them once they are in place. I'm also concerned that if I use wood flooring the room may become too bright sounding by not having the wall to wall carpeting currently in the space.
128x128owl
newbee
4,093 posts
 
Is the garage ceiling finished? If not you might consider adding some more joists and support beams to beef up the 'music' room's floor. Without doing that I doubt you'd get much benefit from just putting in a new hardwood floor. If your ceiling joists were about 12" apart with support beams about 24' apart you could probably do most anything. But if you are spanned at 24 to 48 inches, which conforms to code in a lot of places, you'll always have a spongy floor no matter what you put on top of it. What the effect of this floor will be on bass response is another issue intirely. Have you done any analysis on the actual in room bass response yet which supports that you are in fact loosing bass thru the flexing floor?

Just some things to think about. I'm sure others will have great suggestions.
owl's avatar
owl OP
132 posts
 
Newbee

Unfortunately the ceiling in the garage is finished blueboard with plaster over it. I'm actually contemplating what you recommend as far as increasing the density/number of the floor joists but would have to do so by tearing up the carpet then the subfloor to get at it from the listening room.

Have had a RTA in here and things were fairly flat but bass output turned out to be slightly low even with a powered subwoofer. We had to crank up the sub to it's peak capability to get a flat response, where a colleague who has the exact same sub actually had to reduce it's level as much as the sub would allow. This in part due to room size and perhaps partially the floor. I guess I should have mentioned another primary concern is my equipment vibrating somewhat when I have significant volume level, although I'm using Walker Valid POints which do help drastically and the rack sits on spikes which then sit on drilled platforms of Corian solid surface material.
newbee
4,093 posts
 
Dumb question time. When you did you RTA measurements were you also searching out the nodes and nulls. Could it be as simple as finding the best nodes for speakers and listening positions? Regarding equipment vibration casued by floor movement, can you beef up the floor under the equipment by using piers under the floor extending down to the garage floor, even if set at an angle. If thats possible, then you can put down a layer of vibration absorbant materiel between your floor surface and the base of your equipment to minimize vibrations. BTW re footfalls and bouncing stylus, do you by any chance have a suspended table? If so, consider that contrary to common perception suspended tables don't like foot falls. A good isolation platform and an unsuspended table can be much better.

What a bummer, having a great space for a dedicated room, great equipment, and a lousy floor. :-(
zargon's avatar
zargon
453 posts
 
Owl, I have a similar room over a 2 car garage. The floor was somewhat spongy and was driven into a strong resonance at 31 hz. This was solved by building a beam out of 2x6s in the shape of a "T" and lag bolting the top of the "T" to each joist across the center of the garage ceiling. The "T" beam can be broken into pieces if necessary to avoid any obsticals. This beam resists flexing and ties the joists into a much tighter network. This improved the situation greatly, and might be enough for you.

However, as a extra measure, I then added a steel post in the center by jacking up the beam slightly and sliding it between the beam and the concrete floor. The post was centered between the two car parking slots.

Did it work? The 31 hz resonance is much reduced (some is still in the walls) and you can now go into the listening room and jump up and down as hard as you wish and the turntable (unsuspended on a mass loaded stand) is unaffected.

This solution is very inexpensive and totally unabtrusive to the listening room. You do have to tolerate the beam, but if you place it just ahead of the car doors (near the rear view mirror), it really doesn't get in the way. My total cost was well under $100.
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