Multiple Small Subs - Geddes Approach

[gedlee]

Originally posted by pjpoes

Materials with the appropriate stiffness and mass would seem to be quite heavy, no? One thing I'm wondering about here is supporting such big pieces without having further support. If done in a manner that allowed relatively free movement, could "stand-offs" be used to offer necessary additional support.

Yes, this is a design difficulty. The sag from the weight will be fixed by the weight / area which has to be correct for the resonant frequency to be right. Some sag of the panel will be unavoidable. You might be able to use standoffs, but they will stiffen the panel and reduce its effectiveness. The best thing would be to design for the sag, which should be predictable and build it so that when hung it sags to the right location.

Getting the stiffness of the foam should not be a big problem.

[Sheldon]

Originally posted by gedlee
The sag from the weight will be fixed by the weight / area which has to be correct for the resonant frequency to be right. Some sag of the panel will be unavoidable.

Why not suspend the outer panel? Since the panel movement is horizontal, suspending it with flexible line shouldn't have much effect.

Regarding panel area: How about ceiling panels? Usually that surface is available to a greater extent that walls in a room.

Sheldon

[gedlee]

Originally posted by Sheldon


Why not suspend the outer panel? Since the panel movement is horizontal, suspending it with flexible line shouldn't have much effect.

Regarding panel area: How about ceiling panels? Usually that surface is available to a greater extent that walls in a room.

Sheldon

All good points, but practicality gets in the way. I just recommend "suspending" the panels with glue that also works as a damping mechanism. This kills two birds ... Ceilings are good choices, I do that, but its very difficult to impliment. And you really want the absorption somewhat distributed or certain modes may not "see" it.

[Baseballbat]

Hi,

Originally posted by gedlee I do not admit to any errors. I thought that I made that clear.

this can be misunderstood. You do not dmit to any errors?

There IS a frequency shift in a decay, thats clear.

No, there is not. You know this and you try to say this, but you use a mistakeable verbalisation.

I prefer this:

The decay around the resonance frequency becomes dominant above the decay at other frequencies.

I think, this comes next to the facts and is also understandable by non-PhDs (so by me, I am only a bloody graduated engineer, nothing that could compare to a real PhD (also, I am awfully drunk at the moment, but that was the purpose of this evening).

Bye
Baseballbat

[pjpoes]

Originally posted by Sheldon


Why not suspend the outer panel? Since the panel movement is horizontal, suspending it with flexible line shouldn't have much effect.

Regarding panel area: How about ceiling panels? Usually that surface is available to a greater extent that walls in a room.

Sheldon

unfortunately the ceiling isn't available in mine, but maybe in others. I have unusual shaped vaulted ceilings with multiple recessed lights and two ceilings fans. It leaves very little ceiling space to mount a bass absorber, and they would have to hang at a strange angle relative to the ceiling. It's probably a great options for others, all the better if you have suspended ceilings to hide them in, but I think walls will have to be my option.

I got a price on some perforated metal, I'm going a different route. a 6" wide strip of perforated metal rolled for cheaper packaging, with enough to do 1 trap, was 130 dollars. Then a steel front panel was another 120 dollars. I'm going to have to look for surplus materials or get more creative. Drywall's cheap, maybe I should try that instead.

[TRADERXFAN]

I plan to just stick with the drywall, when the time comes. Nothing too exotic needed.

[gedlee]

Its really hard to beat drywall.

[gedlee]

Originally posted by Baseballbat
Hi,
this can be misunderstood. You do not dmit to any errors?

No, there is not. You know this and you try to say this, but you use a mistakeable verbalisation.

I prefer this:

The decay around the resonance frequency becomes dominant above the decay at other frequencies.

I think, this comes next to the facts and is also understandable by non-PhDs (so by me, I am only a bloody graduated engineer, nothing that could compare to a real PhD (also, I am awfully drunk at the moment, but that was the purpose of this evening).

Bye
Baseballbat

I put this post down to "not my language" and "I'm too drunk!" and let it go at that.

Hey Markus - all these Germans are going to give you a bad reputation!

[gedlee]

Originally posted by Baseballbat

this can be misunderstood. You do not dmit to any errors?

You know, this one grinds at me. I DO admit errors when I make them. But should I admit to an error when its not mine? Would that make any sense? I did not see any concrete proof of any error on my part that I should admit to. Someone said "Your worng!" - I should admit an error simply on those grounds? Please!

[Baseballbat]

Earl,

I put some salt in my post and you only tasted that flavor. Why not lick on the sugar?

Originally posted by Baseballbat
The decay around the resonance frequency becomes dominant above the decay at other frequencies.

Baseballbat