Found the bass culprit in my monitor speakers...

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

Without it, it will make the bass sound boomy

@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.

@audiodav

A lot of good comments, I am not familiar with your speakers, but I assume that you have sealed box woofers, the comments are reflecting such. I would recommend that you do a search and read about the spec called QTC. This spec reflects the smoothness of your bass using a woofer in a sealed box. A flat response has is a qtc of .707. As your box gets bigger Q goes down, then as the box gets smaller, Q rises. So in a larger boxQ will drop, below that number, say .6, your woofer will roll off faster and eventually takes a dip, your speakers lose deep bass and develop a dip. As your box size goes down, Q rises, a Q of 1.0 will have a significant hump in bass response normally causing boomy bass.
I prefer a QTC of .7 to .8, but many designers like a lower Q to design for room settings, I’ve seen speakers with a QTC as low as .5. If your speaker had a Low QTC, It is possible that when removing the stuffing that you raised Q to a more flat consistent output.... I really don’t know this about your particular speakers, but it is certainly a possibility.
You can slowly add fill to your boxes, as your boxes become stuffed, as others have stated, it will act as though you are getting a larger box, once you get totally stuffed, the stuffing has the opposite effect, once are travel starts being restricted, stuffing starts reducing air volume in the speaker.
This is the basics of how and why, I hope this helps,
Tim

Another, less technical, way to think of it- not that any of the above is incorrect, its not-

The sound coming off a driver doesn’t just come out the front and into the room. It goes off the back and into the speaker cabinet as well. So now just imagine if there was another mini speaker playing music inside the cabinet. For sure some of the sound it makes is gonna come out through the driver and you will hear it.

Well, that is exactly what happens with every speaker cabinet. The drivers send just as much sound back into the cabinet as out to the room. The sound that goes into the cabinet, by the time it bounces around and comes back out the front there’s only one word for it: distortion.

Now sometimes at certain frequencies this distortion is just right to actually reinforce the same frequency coming off the front. When this happens, if it brings up a dip in response then we are happy and say the speaker is flat. But if it reinforces a peak we complain and say the speaker is boomy. So another example of how people can prefer even something as seemingly obviously bad as distortion.

But its not just the low bass that comes out. All the sound at all the frequencies bounces around in there, and the less that’s attenuated inside by stuffing the more that’s gonna come out the front.

Any one particular individual might like this distortion. With his ears. His music. And equipment. In his room. Speaker builders usually try and design for a wider appeal. That means designing for lower distortion, less color, more neutral tone, etc. That’s why they stuff em.