basement window, how to avoid the 3 leaf

[TomM]

First off, i'm a bit confused about the 2 leaf/3 leaf thing.. Is 2 leaf ONLY better than 3 leaf in a set amount of space???? For example, if you had 12 inches maximum space, I understand that the 2 leaf is better than 3 leaf because you get a bigger air space. Well what if your studio is surrounded by 2 leaf walls.... but one wall has another leaf a few inches away??? So your minimum 12 inch two leaf surrounds the whole studio except one wall with an additional leaf after the 12 inches.

Would that wall actually have worse isolation???? Or would it be slightly better? Or not different at all?


Now.. onto my question about the window. I've read a lot of posts about windows, but they don't really apply in my case.

I have a basement window at the top of my wall. It's 32 inches wide, 12 5/8 inches high, and 5 3/4 inches deep to a really crappy, thin window. It's NOT a perfect rectangle. It's about 1/8 inch off on one side.

Besides that window, my outside walls are all poured concrete which i think will make for a pretty good outer leaf. (The basement is also mostly underground). The inner leaf wall will be about 5 1/2 inches in from the concrete walls... (that is to the inner sheet rock)...the 2X4 frame will start about 1 1/2 inches in).

How do I plug in that window to make it as good as the poured concrete? (or at least close). Also, even though I don't need it to be removeable... I don't really want it to be permanent... so I can't fill it in with concrete.

Drums are extremely loud outside of my house, and I bet just filling in this window could make a huge difference!!

[sharward]

First off, i'm a bit confused about the 2 leaf/3 leaf thing.. Is 2 leaf ONLY better than 3 leaf in a set amount of space???? For example, if you had 12 inches maximum space, I understand that the 2 leaf is better than 3 leaf because you get a bigger air space. Well what if your studio is surrounded by 2 leaf walls.... but one wall has another leaf a few inches away??? So your minimum 12 inch two leaf surrounds the whole studio except one wall with an additional leaf after the 12 inches.

Would that wall actually have worse isolation???? Or would it be slightly better? Or not different at all?

My understanding, having run into this issue on one of my walls, is basically this...

Third leaves are detrimental to low end isolation due to, as you asked about, the fact that the air gap between the outer leaves is divided, thus resulting in two smaller air gaps than there would otherwise be if the middle leaf were not there.

There are also issues pertaining to resonance in which I am less knowledgeable.

I believe mids and highs actually benefit from third leaves, but that's rarely the "problem area." So, conventional wisdom around here is to attack the low end with as much M-A-M as you can afford (cost- and safety-wise), and the mids/highs will be quite happy.

Sometimes third leaves can't be practically avoided. When that is the case, you can usually mitigate their effects by increasing the depth of one of the gaps and adding more mass.

More clarification from others smarter than I is welcomed... But hopefully that clears things up a bit.

I'll definitely leave your window question(s) to others, as I (thankfully) am not dealing with any window issues in my project and am therefore pretty ignorant on that subject.

--Keith

[bert Stoltenborg]

Avoid three leave systems.

But: when you have, fe, a thermopane window and you put a third leaf on a large distance from that, it won't always be a hazard for your LF TL performance.

Same for walls, but it's hard to give general rules.

Triple leaf constructions can indeed give better performance on mid and high freqs, but for sound with musical spectrum you're not looking for that.

Brian Ravnaas published some data on this on, I guess, the studiotips site.

You have to consider each case and then draw conclusions.
No general rules here, except that 2 leafs with same mass and gap will (almost) always be better for music sound TL.

IT NEVER GETS ANY EASIER!