how to soundproof a small club on a budget?

[JohnD]

What kind of neighbors do you have, is this in a totally commercial area, or a commercial building in a mostly residential area? When you speak of windows, is it just a few windows or a wall of plate glass?
In defense of the book I suggested, the idea was that it provided the basics of sound attenuation, what to do and why, in a more accesable form than an expensive college textbook. Also, since this is a commercial space, get permits, and run anything you want to try(construction wise) past the building inspector, A building inspector can be your best friend, or your worst enemy.
I was curious about dboomer's idea of isolating the subs and was wondering if something like this would help? At least it is cheap.
Rubber Horse Stall Mat, 4 ft. x 6 ft. - 2219003 | Tractor Supply Company
Also, I stand corrected on my use of the term fireproof.

 

[museav]

Going from a completely acoustically reflective room to a completely acoustically absorptive room will only reduce the sound level the room adds, it does not provide any reduction in the direct sound itself. In a typical venue you may be able to get a couple of dB at low frequencies via added absorption and you likely need more than that.

Installing 'soundboard' over existing sheetrock could actually reduce the low frequency absorption the wall provides. Sheetrock walls tend to exhibit diaphragmatic absorption at lower frequencies, the sound energy actually 'flexes' the wall and that mechanically absorbs some of the energy. How that applies to your situation depends on the specifics of the existing construction but making the wall surface thicker and stiffer and you may reduce any diaphragmatic absorption. This is an example of where you might have to look at the details of what you have and the effects of changes rather than just assuming that products or treatments that addressed some other acoustical problem or are advertised as an acoustical product will work in your application.

A 'sound lock' may indeed be beneficial, especially if it provides another barrier from the windows. But is that the only related sound path? Since it would become part of an exit path, what would be required in terms of accessibility, life safety, HVAC, etc. to make it code compliant? What wall construction and construction details would be structurally required and also appropriate in order to achieve the attenuation desired? What is that desired attenuation?

Perhaps the general situation can be summed up simply by your defining whether the goal is to do something or if the goal is to solve the problem. If the goal is to do something then somewhat randomly throwing inexpensive 'acoustical' materials and construction changes at it is fulfilling that goal. However, that doesn't necesarily relate to preventing the neighbors complaining. If the goal is to prevent the complaints then it seems that you first have to determine what that represents and requires, and if it even is achievable, before starting to consider how to achieve it.