2. speakers
  3. 150090-129355

Found the bass culprit in my monitor speakers...

Hello to you all. Months after months of changing the positions of my Leema Acoustics speakers only to hope to get better frequency response and bass output that was always lacking and missing in some certain frequency points. And then I hit this wonderful idea - let’s see what is inside. After opening the back of the speaker and admiring a really nice component crossover I took out about a 50cm long and 3cm thick acoustics wool out. The wool was literally stuffing almost 90% of the whole inside cabinet. Crazy (?) - and now this - after taking out the damping. More bass, more clarity, the great sound has come back again. Now the question - why did they stuff so much wool inside ? I think this is the main point why the users complain about bass output in Leema speakers. Secondly, I can suggest to anyone to experiment with damping inside. Sometimes it is not necessary at all I think. I think it is in closed enclosure speakers but not so much in back reflex port as mine ? I wonder what you think...
audiodav
mijostyn's avatar
mijostyn
8,570 posts
 
The original paper on this was done by Acoustic Research in I think it was 1954. They released the first "acoustic suspension" loudspeaker shortly there after the AR-1. Before then most speakers were infinite baffle and much larger like Bozak speakers of the time which did not use any stuffing. 
bdp24 the air molecules "moving around" does not explain the increase in enclosure size perceived by the woofer . As I explained above it is a thermal-barometric principle.
Obviously, a speaker can be over filled which happens as soon as you start compressing the acoustic cotton. It has to just fill the enclosurewithout compressing it. 
I think "monkey see monkey do" insults the intelligence of many thoughtful speaker designers out there. An excellent manual on the subject is The Loudspeaker Handbook by John Eargle. 
Audiodav if you like the sound better than let the force be with you:)
stereo5's avatar
stereo5
6,404 posts
 
@mijostyn...........................

Bozak did use acoustical stuffing inside their speakers. The walls and back were covered in a half inch thick padding that was stapled to the inside of cabinet.  I should know, I sold and replaced many a woofer and tweeter in Bozak speakers back in the 70’s. 
mijostyn's avatar
mijostyn
8,570 posts
 
stereo5, yes you are right. My father had a pair of B302as and as you describe they had I think it was fiberglass insulation probably between 1/2 to 1" thick stapled to the inside wall of the cabinet. They were doing that I think to reduce resonance in the enclosure walls although I can't see how that would work. It would not in any way work in the same way acoustic cotton works in a smaller sealed enclosure. To work the cotton has to just fill the entire cavity. Also in a larger enclosure the pressure (temperature) changes are not as extreme so even if you filled the entire cavity the effect on the systems resonant frequency would be negligible or greatly reduced. The point being that it is not acoustic stuffing in the usual sense, it is dampening of some sort. Maybe there is an old Bozak designer around that could fill us in:)

Mike
miketuason
337 posts
 
Without it, it will make the bass sound boomy
stereo5's avatar
stereo5
6,404 posts
 
@mijostyn...………………...

Sadly, Rudy Bozak is no longer with us.  I met him in the early 70's.  I drove my company's truck to The RT Bozak Manufacturing Company on Connecticut Ave. in South Norwalk, CT.  I was picking up an order of speakers and I met him on the loading dock!  He showed me around the entire factory (They made all their own drivers) and even treated me to lunch at a Greek diner down the street.  What a nice man.  He had some talented engineers, they are probably all gone now.
More to discover