BTW - I have the "How to build a small budget recording studio from scratch" book and I would be willing to send it to you if you paid for postage, or I would even just sell it to you for a small fee. I won't be building another studio anytime soon. My current room in the basement in this house has no forced air entry/exit into the room and it also has a big sliding door closet stuffed with winter clothes and linens - that combo and my mic choices have been pretty forgiving compared to the old purpose built room.

To be honest, quite a bit of stuff in that book was quite a bit over my budget when I built my basement studio.

I'm pretty adamant about the HVAC stuff because it's specifically what I was unable to accomplish in my build and it was by far and by spades the weak link in my whole build.

The issue for me was that I had to create this basement 'studio' in a space where the built-out ceiling would be just under 7' and I had to run HVAC via the space over the main I-beam and between the floor joists and I had no ability (though I just read a very interesting idea while looking for some links for you) to make the tortuous path I was referring to above - particularly for the return path.

I WAS able to keep the foot traffic noise above to nearly non-existent through both isolation as well as absorption - thick batting between the joists, 'sound stopper board' (which looks just about the same as the old asphalt bound sawdust sheeting they used to use on stick construction before foam became the norm), furring strips across that, then resilient channel (I used the stuff that is 'z' shaped), and then hung the drywall from that. I should say that I did all of that work except for the hanging of the drywall, the guy I paid to help me did all of the drywall work.

On one side wall - it was running along the length of the main iron I-beam for the house, so I built a wall on either side of the I-beam using two different thicknesses of sheetrock for each side - and stuffed it with batting. Door details in the previous post.

With all of that work - I could still hear my kids playing coming through the HVAC, two floors above and probably 40-50 feet of duct-work in between. Normal forced air HVAC ducts are incredibly efficient sound transmission devices!

I saw a really cool tip yesterday on how to perhaps help with that: Use a section of wall between studs as a plenum of sorts, make a tortuous path in the plenum with some of that stiffer fiberglass insulation - dump in at the top of the wall, and make your exit into the room at the bottom of the wall. This is from the Auralex site:

"• If you do your wall construction appropriately, you might even consider terminating your duct into the space between two wall studs, which you can line with fiberglass board, then venting that space into the room. We have seen this done and it proved to be very quiet!" If I was to do this all over again, I would make some flex-breaks in both inlet and outlet air, do this tip for both inlet and outlet (make sure you have enough x-sectional area for flow both ways) and be done with it.

I wish I had seen that before I did my build. Now, in order to make this work, you would need to caulk the sheetrock and stud interfaces in that section pretty tight, to avoid airflow leaks. I know I saw a diagram of this yesterday as well.

I was able to keep actual system noise to a minimum very simply because about 5 steps outside the door was the main power for my forced air HVAC. The only issue is that now and then after late-night recording sessions, I would forget to switch the system back on and the house would be really cold in the morning!

I guess the reason for my passion is that the amount of work that is done with noise & vibration control is dependent on the weakest link/system in the whole design. I'd like to see anyone avoid the big mistake (well, I was incredibly limited as to what I could do duct-work wise based on the existing construction and that danged I-beam) in my system design. I rolled the dice - I did know that HVAC could be the weakest link, and in a way I lost. I still had to wait until the family was at rest before I could do my mic'ed recordings as I was using a pretty sensitive LDC microphone at the time (I've almost completely 'switched teams' now using a very forgiving and inexpensive EV dynamic mic designed for vocals)

-Scott

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