Cabinet Dampening- Your Experiences.

fredgarvin

fredgarvin

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I'm sure a lot of you have tried alternative dampening experiments with your speakers in an attempt to improve the sound. Deflex sheets, fiberglass, polyfill, Dynamat and other automotive deadening products. It's controversial to some as they hold the opinion that manufacturers test their products and what they have stock is probably best. Q, cabinet volume etc. Others feel price point demands often necessitate shortcuts that can be improved. So, what have been your findings?
 
I only stuff cheaper speakers that didn't have any stuffing to begin with. I used fiberglass (leftover from renovation work), or polyfill (out of old pillows). IME, stuffing tunes the bass, and fiberglass makes a bigger change than polyfill when you use the same amount. Some people will tell you not to use fiberglass in ported enclosures citing health risks. From what I've gathered, studies on the health risks of fiberglass have been inconclusive.
 
Stuffing materials damp the air in the cabinet. They have little effect on the cabinet itself. The point of stuffing is to control airborne bass frequencies and lessen 'boom', making the bass 'tighter'. It is possible to go overboard and make the bass too tight.

Cabinet damping needs a dense lossy material, typically bonded intimately to the cabinet inner surface over a broad area. The purpose is to prevent transference of cabinet vibrations to the outside air, where they would pollute the signal with out-of-sync information.
 
I use to work with the NVH group at Ford product development. We tested a number of damping materials for prroduction. The best we found for killing resonance is Dynamat. Clean the surface really well with a grease cutter and heat the area with as hair dryer, then stick on the Dynamat.

WARNING!!! It can kill bass if the cabinet is used to augment bass. The difference will shock you.
 
djnagle said:
I use to work with the NVH group at Ford product development. We tested a number of damping materials for prroduction. The best we found for killing resonance is Dynamat. Clean the surface really well with a grease cutter and heat the area with as hair dryer, then stick on the Dynamat.

WARNING!!! It can kill bass if the cabinet is used to augment bass. The difference will shock you.
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That is one major warning.

What type of cabinets are used to augment bass. I’m thinking you mean ported as opposed to sealed.

I would not changed a thing on my Adagio cabinets, just curious for restoration of older less expensive models.

Thanks
 
bobins08 said:
That is one major warning.

What type of cabinets are used to augment bass. I’m thinking you mean ported as opposed to sealed.

I would not changed a thing on my Adagio cabinets, just curious for restoration of older less expensive models.

Thanks
Click to expand...

That is why we have cabinets in the first place. Dampening cabinet vibrations via bracing in my Fortes made a huge improvement - not just the bass - top to bottom. Sealed cabinets also augment bass.

Dampening filler is for internal reflections, I think. Someone correct me.
 
musichal said:
That is why we have cabinets in the first place. Dampening cabinet vibrations via bracing in my Fortes made a huge improvement - not just the bass - top to bottom. Sealed cabinets also augment bass.

Dampening filler is for internal reflections, I think. Someone correct me.
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Yes, I get that, all cabinets should augment bass. I just don’t understand what @djnagle means in reference to damping a cabinet with material like dynamat “... it can kill bass if the cabinet is used to augment bass.” I assume he was talking about adding dynamat - it helps but it can also hurt. What kinds of cabinets does it hurt?

Not talking about filler or bracing.
 
I have had success using carpet padding--comes in various thicknesses and densities, and can be cut to fit and glued or stapled to the interior of the cabinet.
 
I could be completely wrong but I seem to recall reading that Wharfdale deliberately used thin wall cabinets for some speakers because they wanted them to resonate. If I'm not having a hallucination or remembering wrong that would be an instance where one wouldn't want to use cabinet dampening material.

On the other hand I also seem to recall that they also built some cabinets with a sand filled cavity in the rear wall.

Someone please correct me if this is wrong.

As for myself, after 33 years of use I removed the Dacron fill in my Speakerlab 7's and replaced it with fibreglass, about 80-90% full. Bass is now less boomey and tighter. I'm very happy with the change.

Cheers,
James
 
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When I was using a pair of Polk RT10's as my mains I replaced the thin stock foam that the manufacturer had in place due to aging and falling out of place inside the cabs. I lined the inside using Sonic Barrier sound damping with very nice results. It returned the imaging, opened the sound stage and was just an overall worth it improvement.
 
bobins08 said:
Yes, I get that, all cabinets should augment bass. I just don’t understand what @djnagle means in reference to damping a cabinet with material like dynamat “... it can kill bass if the cabinet is used to augment bass.” I assume he was talking about adding dynamat - it helps but it can also hurt. What kinds of cabinets does it hurt?

Not talking about filler or bracing.
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'djnagle' might be referring to ported cabinets which should be lined not stuffed, where damping material can kill the bass if overdone.
(That info from an old Altec speaker building guide and from personal experience, BTW.)
Overdamping can also cause a ported speaker to sound quite lifeless.
It's all about controlling the reflections (standing waves) inside the cabinet without killing the backwave which is essential to supplying the energy for the port.
 
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James' statement reinforces the need to always consider the original designers intent and realize the voicing of the speaker may change substantially with modifications.

I mean, you can't just take general statements like, "Adding internal bracing always improves frequency response" and assume it's true for any particular speaker.

Doug
 
BBC monitors are a good example of using the resonant frequency of the cabinet to augment bass... adding dynamat would change them for the worse.

Btw, not to be a curmudgeon, but the term is damp, or damping. To dampen, or to experience dampening involves moisture, and should be avoided in any speaker enclosure.
 
ref: my above post - those Polk RT 10's are port designed. My everyday mains now: ADS CM7, are sealed, they are stuffed with the fiberglass looking material.
 
I dampen an enclosure based on what the plans specify. Some speakers use dampening while others don't. My Zu speakers used no stuffing but rather a large foam cone.

The carpet underlayment from a junk Ford F150 provided the correct thickness for these Frugal Horns. The Polyfill is pillow stuffing.

P3040012.JPG
 
For me I have tried all types -- however one of the better options and even easier to handle than fiberglass, is Denim Insulation. As stated, a good speaker designer gets it right. If I tend to mess with speakers, it is for the budget friendly under $300 speakers, or some old ones found on Ebay or Craiglist or thrift stores
 
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