[YoungDave]

All,

I admit my ears are not as well trained as many of you - maybe they never will be, but I am working on them...

Some weeks ago I applied BH5 to the insides of my cabinets and left them pretty well stuffed with fiberfill.  I don't mean loose, I mean pretty darn full, but not packed tight.  I understand that BH5 is primarily to reduce cabinet resonance and may have little effect on PR dampng, but I wonder how one figures the effect of all that fiberfill?  Mightn't everyone use a little different amount, leaving the PR damping highly variable?

I note that I can push in on the PR and see an immediate resonse in my woofers, so they are obviously not isolated by the fill, but still, it must affect the damping, what?

If removing just a little putty at a time, passing the null, and then adding a little  leads you to the golden sound, but if the additional damping of a lot of fill makes it so all the material has to be removed & you never hear the null, how will you know where you are?

FWIW, I have a FFT spectrum analyzer, low-distortion oscillator, good mikes, etc, but I can't measure any difference in woofer distortion while fooling with the putty - I think mike measurements in a room are just not feasible...

Obviously, I am trying to get clues about how to get near that golden zone so that I don't go right past it without noticing...

Any hints?

[Corbin Johnson]

I think this is an excellent question.  I once added some additional insulation because it seemed loose because I'd done so many upgrades.  I called Brian to ask how much is enough and he didn't seem very concerned that a little more or less would impact the sound.  He told me to stuff it tight, but not so tight that the insulation could expand into the cage of the passive and affect the movement of the passive.

A while back I recall reading that you can tune the 626's by removing some of the insulation.  So if that's true, the amount of insulation should be a critical factor.

I'm still waiting for my BH5 and waveguides.  What's your impression after adding the BH5?

Corbin

[JoshK]

modern research and modeling on the subject, done in part by ML, has suggested that in terms of optimally dampening standing waves within the cabinet, stuffing should be added to 3/4 of the length of the longest dimension, with the 1/4 unstuffed portion closest the port (in this case PR).  This would mean that the upper 3/4 of the cabinet should be stuffed densely, but not super tight and the bottom 1/4 should be left unstuffed (but definitely treated with BH5 or other dampenings .  

I learned this after doing my cabinet dampening so I haven't tested this stuffing guide myself, but had intended to.

[warnerwh]

The amount of stuffing can definitely affect the sound. Pull a bunch out and listen again. Then add more than had been in there before.  More seems to soften the sound and dynamics and less of course the exact opposite. I'm sure amplitude variations also come into play here also.

[ctviggen]

The book "The loudspeaker design cookbook" has a ton of information on how stuff affects sealed systems.  It affects the F3 and a bunch of other stuff.