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Query on Damping a cabinet to absorb all internal reflections


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Hi all...

Been looking for a way to improve my DIY speakers. Understand that DIY builds have 2 common failures, that main stream deep pocketed manufacturers with acess to anechoic chamber testing don't. One being baffle edge diffraction and second being internal standing waves. 

I found a cheap way to try and neutralize baffle diffraction with the use of felt pads around the tweeter and the mid range driver. Don't know if wrapping  the wool felt around the edges also a makes a difference or not at this point.

Coming to internal standing waves, any reason why we can't stuff enough absorbent material in the dedicated tweeter and mid range cabinets, to completely absorb the internal waves, so that they don't strike the back side of the driver, causing a smearing in sound.

I understand that it would change the sound signature of a passive speaker completely, running off passive crossovers. But since my case in point is converting a passive speaker to active. I can put more power to the drivers, as well as alter the frequency response in the active crossover. So are there any detrimental effects of damping the internal part of the cabinet too much. Thanks in advance for your time and help :)

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Sorry forgot to mention, if adding too much of damping or internal absorption leads to a drop in efficiency of the driver. Then that won't be a issue, as there is enough amp power to handle the drivers even with the cabinet fully stuffed with absorbent material behind the driver .

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Posted (edited)

If they are sealed enclosures, then in my experience the more damping the better, not so with reflex speakers. Loose lambs wool is my choice.

Also the more damping gives the speaker driver the illusion of a bigger cabinet.

Edited by greybeard
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11 minutes ago, greybeard said:

If they are sealed enclosures, then in my experience the more damping the better, not so with reflex speakers. Loose lambs wool is my choice.

Also the more damping gives the speaker driver the illusion of a bigger cabinet.

Thanks sir :)

The cabinets for both the mid range and tweeter are fully sealed. Though the bass driver is in a seperate TL enclosure in the bottom, which I plan to now seal completely, as I will be adding stereo subs to handle bass below 100 or 120 hz , depending on where it blends best :)

so considering the above, can I stuff as much loose lambs wool as possible behind the mid range and treble drivers as possible, as long as they don't start touching the voice coils etc :D

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What is the cabinet material?

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2 hours ago, newlash09 said:

Thanks sir :)

The cabinets for both the mid range and tweeter are fully sealed. Though the bass driver is in a seperate TL enclosure in the bottom, which I plan to now seal completely, as I will be adding stereo subs to handle bass below 100 or 120 hz , depending on where it blends best :)

so considering the above, can I stuff as much loose lambs wool as possible behind the mid range and treble drivers as possible, as long as they don't start touching the voice coils etc :D

Tweeters are generally a sealed unit so no need to stuff them. But the mid range yes as much as you can manage, and then see how they sound to your ears, and adjust accordingly.

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20 hours ago, TheFlash said:

What is the cabinet material?

Hi sir :)

The cabinet is twin layered MDF. If I remember right, the front baffle is 50mm thick.

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In my bass units the most effective damping material was the aluminium foil/ rubber adhesive sheets used to damp sound/vibration in cars/vans ....proved it with REW analysis - OMG I’ve become a measureist 😁

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Posted (edited)

I'm using a mix of all sorts in a loosely based ns1000. lead, lambs wool, baf and egg crate foam. 

Edited by tackleberry
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2 minutes ago, MF 1000 said:

In my bass units the most effective damping material was the aluminium foil/ rubber adhesive sheets used to damp sound/vibration in cars/vans ....proved it with REW analysis - OMG I’ve become a measureist 😁

Yes I always use that on the cabinet walls first, then sometimes old fashioned carpet underlay, before  eggbox foam for diffraction, and then loose lambs wool if it is a sealed enclosure.

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3 hours ago, newlash09 said:

Hi sir :)

The cabinet is twin layered MDF. If I remember right, the front baffle is 50mm thick.

Great stuff. It doesn't come better.

2 hours ago, MF 1000 said:

In my bass units the most effective damping material was the aluminium foil/ rubber adhesive sheets used to damp sound/vibration in cars/vans ....proved it with REW analysis - OMG I’ve become a measureist 😁

I used this to line my gorgeous looking but rather too resonant teak Posselt Albatrosses. It is excellent.

On 07/05/2021 at 19:12, greybeard said:

If they are sealed enclosures, then in my experience the more damping the better, not so with reflex speakers. Loose lambs wool is my choice.

Also the more damping gives the speaker driver the illusion of a bigger cabinet.

I'd never heard this. I think I need to take a peek inside the Posselts. I have something in there but not necessarily lambswool; will review materials and quantity!

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With sealed units yeah👍

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My Posselts are downward ported. Just saying. For me and in case anyone else reading this is interested...

 I would have expected the “impression of a larger cabinet” thing to apply with or without port due to how the material affects air flow. No?

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Given my bass cabs are over 150l ....if the damping makes them seem bigger they gone from huge to immense then :rofl:

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My Posselts are downward ported. Just saying. For me and in case anyone else reading this is interested...
 I would have expected the “impression of a larger cabinet” thing to apply with or without port due to how the material affects air flow. No?
In transmission line design the stuffing lengthens the apparent length of the line so yes, at least sometimes.
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