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-   -   Dampening a must? (http://www.diyaudio.com/forums/multi-way/31326-dampening-must.html)

squidbait 31st March 2004 05:12 PM

Dampening a must?
 
Is dampening a must?

I see some people use foam, some fiber, even saw someone use insulation.

What are the avantages/disadvantages of these different materials? Also, is it trial and error to find out how much to use?

Do you have to use anything?

Timn8ter 31st March 2004 06:22 PM

(btw, it's damping not dampening, "to dampen" would be to get it wet :bigeyes: )

There's two kinds of damping, cabinet damping and acoustical damping. You're referring to acoustical damping which may or may not be necessary. It can present a larger virtual volume to the driver and/or reduce HF resonance inside the cabinet.

squidbait 31st March 2004 07:33 PM

Ooops. Damping.

I am talking about cabinet damping.

Is it just a trial and error type of thing?

Timn8ter 31st March 2004 08:05 PM

Or an experience thing. Cabinet damping would involve gluing something like tile, asphalt sheets, another layer of wood, bracing or any combination thereof to the inside of the cabinet panels. I've used a combination of bracing, to limit the length of paneling that can vibrate at an undesirable frequency, with asphalt sheets typically used as damping material in car doors. It's generally accepted that having a vibration free enclosure is the ideal and I've heard speakers made from rock that are exactly that and they sounded great. It may have had something to do with superior drivers and crossover too. On the other hand, I've heard speakers (with full-range drivers) where the cabinets were allowed to resonate and blend their sound in with that of the driver making it similar to a musical instrument like a guitar. They have their appeal too. I think that for low-frequency reproduction (like a sub) a well damped cabinet is definitely better.

squidbait 31st March 2004 08:14 PM

I am confused. I assumed cabinet damping was adding foam or some sort of fiber material.

I learned something now that I probably would have asked later!

Now for acoustical damping... How does that come into play? Are some materials better than others? Foam, etc...

Timn8ter 31st March 2004 09:13 PM

If you just want to control some HF resonance all you'd probably need is some polyester batting to line the inside of the cabinet with. If you're trying to increase the virtual size of the cabinet then polyester wool (Poly-Fil, Acousti-stuf) would be your choice. In the case of tuning TLs poly-fil is generally used and then it's stuff listen, remove or add, test, until it sounds right to you. As a rule of thumb, you shouldn't have to add more than 2/10th to 3/10th lbs per cubic foot to your enclosure to get the results you want. Some box programs like Martin King's MathCAD worksheet include a stuffing measurement which helps a great deal. Other than that, AFAIK it's stuff and test. An interesting tidbit; Steve Margolis (Seventh Veil) came up with an idea of putting a sand filled sock in the bottom of his cabinets to eliminate standing waves between the top and bottom parallel surfaces (which did work). Later, he removed the sock and put a small amount of poly-fill in the middle of the enclosure. The results were the same.

Bill Fitzpatrick 31st March 2004 09:20 PM

Quote:

Originally posted by Timn8ter
On the other hand, I've heard speakers (with full-range drivers) where the cabinets were allowed to resonate and blend their sound in with that of the driver making it similar to a musical instrument like a guitar. They have their appeal too.
They may have their appeal to the ocassional odd-ball but this kind of thing has no place in music reproduction.

Jocko Homo 31st March 2004 09:37 PM

No, you say????
 
I could introduce you to some people who used to carry some of my products.

Used to is the key phrase here........

Anyone care to wonder why it is "used to"?


Jocko

officeboy 31st March 2004 09:48 PM

Quote:

Originally posted by Bill Fitzpatrick


They may have their appeal to the ocassional odd-ball but this kind of thing has no place in music reproduction.


Sometimes.. People should just settle down. :whazzat:
Beauty being in the eye (or ear) of the beholder and all.

Timn8ter 31st March 2004 11:53 PM

Re: No, you say????
 
Quote:

Originally posted by Jocko Homo
I could introduce you to some people who used to carry some of my products.

Used to is the key phrase here........

Anyone care to wonder why it is "used to"?


Jocko

Somebody bought out your company and now you're too young to retire, too old to start over, and generally upset about the whole thing?
Just a guess.

;)

I don't get your point though. Is this about acoustical damping?


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