Speaker Box Damping

[fantfool]

OK fair enough. Part of the question was regarding stuffing materials. I have read for years that wool was a very good material for stuffing, some people used fiberglass. I remember most of the speakers I took apart when I was a kid had fiberclass glued to the inner box walls. The first set of speakers I built about 16 years ago I used fiberglass on the walls only. More recenty there seems to be more people talking about polyfill or pillow stuffing materials and stuffing the cabinet relatively full. I was kind of considering using both. Any thoughts?

[Svante]

Originally posted by fantfool
OK fair enough. Part of the question was regarding stuffing materials. I have read for years that wool was a very good material for stuffing, some people used fiberglass. I remember most of the speakers I took apart when I was a kid had fiberclass glued to the inner box walls. The first set of speakers I built about 16 years ago I used fiberglass on the walls only. More recenty there seems to be more people talking about polyfill or pillow stuffing materials and stuffing the cabinet relatively full. I was kind of considering using both. Any thoughts?

I suggest some experiments to get first hand information. Put a cheap omni electret microphone inside the box and run a few sweeps. Then you will see the effects of different materials on box resonances.

If it is box resonances you want to kill, polyfill is not a good idea. If it is only isothermalizing you want (eg for a sub) it might be a very good idea. A sub typically has a crossover filter that removes the frequencies where there are box resonances.

[fantfool]

Well I am trying out 100% wool blanket material wrapped in poly to stuff the balance of the cabinets. I previously had them about half stuffed. We'll see what effect this has.

[MJL21193]

Originally posted by fantfool
Well, I have a 2 way system with 2-6 1/2" mid-woofers from the Zetag Hi G1s, (not the copper looking ones), and 1 Focal TC90 in each box. I finished these about a year or so ago, but haven't been entirely happy with the sound.

Hi,
Did you design the box correctly? Is the port tube length and diameter correct? How about the crossover?

These have a bigger effect on the sound quality than stuffing.

[fantfool]

You know I wish I could emphatically say yes, but not knowing the T/S specs on the woofers makes it less then certain that I calculated the box volumes correctly. The x-overs I got from the same person I got the drivers from. They are a Wilson Cub emulation. Like I said they sound good, just not the wow factor I was expecting. They sound better for HT then for stereo which is a disapointment.

[MJL21193]

Originally posted by fantfool
You know I wish I could emphatically say yes, but not knowing the T/S specs on the woofers makes it less then certain that I calculated the box volumes correctly.

All speakers sound better on HT (source material, that is).

I take it they sound boomy? Box tuning might be lower than it should be.
Do this: Block the port with a pair of socks or something and see if that improves the way they sound.

[marchel]

10 years ago, I've read an article form Car Stereo Review magazine.

It was an experiment about the effect of poly fill on the box volume of a sub box, AFAICR, It was a 1 cu/ft box.

There were 25 to 40% gain in volume of the box, depending on how much poly fill was filled.

AFAICR again, with 1 pound polyfill on a 1 cu/ft of box, the gain is about 25% increase in volume.

You can increase the polyfill up to 1.75 pounds per 1 cu/ft of box, But increasing it beyond 1.75 pounds per 1 cu/ft would have the effect of decreasing the box volume due to over stuffing.

For the larger box on the experiment, I think it was about 3cu/ft, the Gain in volume was less, only up to about 35% max.

All in all, from what I',ve learned from that article , is that 1 pound of polyfill per 1 cu/ft , is a good starting point.

[fantfool]

Originally posted by MJL21193


All speakers sound better on HT (source material, that is).

I take it they sound boomy? Box tuning might be lower than it should be.
Do this: Block the port with a pair of socks or something and see if that improves the way they sound.

Boomy........maybe a little. I would call it more muddy than boomy. They don't sound clear and natural in stereo, that is why I was thinking box resonance. You may be right about the box tuning because I went by the information given to me by the person who sold me the drivers. I built my center channel out of the same drivers and x-overs, but built a sealed enclosure, obviously to make it smaller and better for voices, and it does sounds better. If he was off, my box tuning would definately be off as well since I used a program to give me box volume and port area. That is why I was asking if anyone had any info on those Zetag Hi G1 drivers. I think they are good quality thats why I'm disapointed in the result. I'not 100% sold on the Focals either, but thats for a different thread.

Thanks for your input, it is starting to make more sense to me now.

[fantfool]

OK tomorrow I do some experimentation!