thin-walled vs heavy construction for sealed loudspeaker

[loheswaran]

I have decided upon making a two way design in a sealed box.

I am now considering whether I should go down the heavy construction type method of construction whereby I will use an inner box of birch ply, with an outside box of MDF, or to go down the thin-walled damped construction style.

Whilst I am posting my question, should the tweeter go in the cabinet, or can I purchase it on an extended front baffle like the ALON lotus speakers (ie. dipole design). I would like to try the dipole route if truth be told, as I've always liked their sound.

[planet10]

You forgot the "HF/Hi Q resonance box method" (no box is without resonance). The most effective method i've heard in the 35+ years i've been building boxes.

dave

[kenpeter]

Suppose you deliberately tune a thin walled box as a passive radiator?

[Jonathan Bright]

Hi Dave.
Intrigued. Can you post a reference to the "HF/HI Q" stuff please? Or a a brief description. Tried Google without any success.

[planet10]

Discussion on what materials to build speakers out of

Long thread. I am slowly making an article out of it.

dave

[Jonathan Bright]

Thanks. Will ponder.

[speaker dave]

Originally Posted by loheswaran

I am now considering whether I should go down the heavy construction type method of construction whereby I will use an inner box of birch ply, with an outside box of MDF, or to go down the thin-walled damped construction style.

In general, heavy construction pushes the resonances higher (but they may be more severe) and a damped construction style will lower their Q and output.

We all do the knuckle rap test on cabinets. The first cabinets I experienced that sounded really different were some BBC monitors (LS 5/1ac, I think) that were fairly thin plywood and very heavy damping pads. I really think the high damping approach is the way to go.

Surface damping isn't as efficient as internal (constrained layer). At Snell we developed some constrained layer damping techniques with 1/2" MDF twice and a thin layer of noise killer yellow in between. This worked very nicely.

David S.

[Arty]

I might be missing something, but is there any reason why NOT to build the heavy box with double walls, AND apply the heavy damping?
suposedly if something, than that should not end up bad.
Exterior damping is not a bad idea, but it -when done properly from sonic view- will look quite childish.
the material i use for the purpose and found to be working well is quite simular to the style this here dogy has on his/her skin.
http://www.dogsindepth.com/herding_d...s/puli_h03.jpg
/my english knowledge is not develop well enough to describe it properly.and i have no camera to take a shot of my speakers.

[planet10]

Originally Posted by Arty

I might be missing something, but is there any reason why NOT to build the heavy box with double walls, AND apply the heavy damping?

There is little question that a well exectuted constrained layer is amoungst one of the most effective techniques sonically.

My goal is to achieve effectively the same results thru finesse with more eleganance. To achieve with less strain on the wallet, and the back. Making less more.

dave

[Soundminded]

IMO the best advice is to build heavy wall construction with internal cross bracing. This will help stabalize the box. Another approach is an inner and outer box separated by a space filled with sand (Wharfedale WD series method.) If you build light construction you have no control over what frequencies or how much the box will flex. Pressure inside the box can get considerable. The granddaddy and champion of sealed box small speakers was Acoustic Research Inc. Their two cubic foot box with 12" systems weighed over fifty pounds. Restored they can still hold their own against speakers costing many times their price and much larger.