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studiomaster 20th June 2012 07:31 PM

wadding???
 
Hi all
Knowing the apparent advantages of using a wadding or some sort of foam liner to the inside of a speaker cab , is the same true when talking about bass bins or should the insde walls of the bin be left undampened to perhaps resonate more freely?

Cheers

Kev.

richie00boy 20th June 2012 07:44 PM

You don't want walls to resonate! Even if you have a good steep filter on the sub I still recommend lining the wall behind the drive unit if you can.

OMNIFEX 21st June 2012 12:11 AM

All my bins have wadding. I don't like standing waves.

studiomaster 21st June 2012 01:14 AM

Thanks for your replies chaps
I appreciate your points of view.
Bearing that in mind should i cover all internal areas? will the sound be improved further than just lining the face opposite the speaker cone (inverted) or would it be overkill? would it have any detrimental effect on output volume even if it DID improve quality?
From my place of work i can get waste packing foam that seems to be very similar to the stuff used in studios,etc, as sound deadening material, corrugated and two inches thick approx, do you think this could work? if not what sort of thickness would you suggest?

Cheers

Kev.

5th element 21st June 2012 02:04 AM

Personally I think it depends on the cabinet dimensions. If the cabinet is small enough compared to the wavelengths that the driver will be reproducing then you're unlikely to get any standing waves forming inside. Stuffing the box is also going to have only a minimal effect on reducing any cabinet wall vibrations. Stuffing the box will however increase the apparent volume of the box and also reduce the effectiveness of any reflex loading should it be present.

Top Shelf 21st June 2012 02:20 AM

Did a test last summer with levels held constant, found a lined box had 0.5 db less average output compared to the same box without. Nothing too significant. But no gain for the extra effort, IME. Every professional subbox I've looked inside has been bare.

5th element 21st June 2012 02:27 AM

Quote:

Originally Posted by Top Shelf (Post 3066831)
Did a test last summer with levels held constant, found a lined box had 0.5 db less average output compared to the same box without. Nothing too significant. But no gain for the extra effort, IME.

What were the conditions of this test? Driver, box type/size/alignment?

OMNIFEX 21st June 2012 12:40 PM

Quote:

Originally Posted by studiomaster (Post 3066785)
Thanks for your replies chaps
I appreciate your points of view.
Bearing that in mind should i cover all internal areas? will the sound be improved further than just lining the face opposite the speaker cone (inverted) or would it be overkill? would it have any detrimental effect on output volume even if it DID improve quality?
From my place of work i can get waste packing foam that seems to be very similar to the stuff used in studios,etc, as sound deadening material, corrugated and two inches thick approx, do you think this could work? if not what sort of thickness would you suggest?

Cheers

Kev.

Right!

The difference in sound, when using wadding in a bin as opposed to leaving it empty will depend on how large of a bin you are using, in addition to the TS Parameters of the loudspeaker.

If the bin is not large enough to accommodate the loudspeaker to achieve a relatively flat response, the end result is having an oval curvature. Such a curvature tends to offer a good amount of gain over 0 dB, and tends to offer this type of gain within the upper bass (60 – 200 Hz) region. This tends to have the bin ring at frequencies residing above 0 dB.

If the bin is very large the side panels will resonate at certain notes.

Wadding dampens the offending frequencies to achieve a more even response. It reduces the chances of the bin adding it’s own influence to the audio signal.

Some professional manufactures will sacrifice an even response for an uneven response for the sake of more SPL. Considering the amount of SPL can be achieved from an enclosure resonating, it is not surprising some companies will not add wadding to increase their sales.

The material used as a means of damping will offer it’s own characteristics in the end result based on its properties. My experience is more to wards the traditional wadding used when building homes.

I tend to cover all walls except the baffle board due the magnitude of the enclosures I design. You may need to dabble around to find which works best for you under the given conditions.

studiomaster 21st June 2012 07:57 PM

Thanks to all for your thoughts and explanations.

Cabs contain 15", 8 ohm 375 watt subs. (only cheap and second hand,but dont sound too bad)Do not know any specs I`m afraid. Drivers fire INTO empty chamber (not tapped) (btw what is the correct name for this design) out thru cab-width port at bottom rear,using scoop to push forward. Not sure if its worth lining.

ta

Kev.

Ron E 21st June 2012 11:44 PM

Quote:

Originally Posted by studiomaster (Post 3067721)
(btw what is the correct name for this design) out thru cab-width port at bottom rear,using scoop to push forward. Not sure if its worth lining.

That is a horn - don't line or stuff it. You could put some lining in the sealed chamber if you want.


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