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Old 2nd June 2004, 05:11 PM   #1
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Talking Stuffing anyone????????????

What are the best amterials to stuff a vented subwoofer with and how much do you put in there?

Does stuffing mean you will have to change the volume for the design on WinISD?

Not related to the above but what should i tune the vent to if i'm going to use the sub for loud music and exlosive films?

Thanks for any help recieved
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Old 2nd June 2004, 06:08 PM   #2
sreten is offline sreten  United Kingdom
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Vented subs are generally not stuffed they are lined with acoustic foam.

though you can stuff areas away well awway from the port, BAF
(bonded acetate fibre) also known as polyfill or pillow stuffing is
generally used.

Tuning the vent is a lot more subtle than simply choosing a frequency,
I don't know much about home theatre sub tuning.

sreten.
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Old 2nd June 2004, 07:02 PM   #3
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I have a huge roll of roofing felt for the inside walls and a roll of cotton wool.

Should i just line the inside walls with the felt and the wool?

For the tunning frequency of the vent WinISD has given me 34Hz but someone recomended 28Hz, how should i chose?
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Old 2nd June 2004, 07:11 PM   #4
Bose(o) is offline Bose(o)  Canada
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If you want the best for HT, I know that 16Hz. seems to be the magic number. At least 16-20Hz. for ultimate HT. I guess this would leave less room for being below tuning since there isn't a whole lot of musical information below 16Hz. ( yes I know there still is, but I'd bet that the LFE channel won't go that low with much intensity to really do damage).
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Old 2nd June 2004, 09:12 PM   #5
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Default Don't stuff a sub.

For a subwoofer stuffing is not only not required it actually may hurt response. I've tested a number of subs with and without stuffing/lining/damping and never found it to be of benefit and often response was compromised. Damping is a must with shorter frequencies but in subs where the frequencies are all significantly longer than the internal box dimensions (the wavelength at 100 Hz is about 13 feet, and it just gets longer as you go lower) damping does not help. Most manufacturers do so anyway because they're expected to, but not because it works.
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Old 2nd June 2004, 09:32 PM   #6
Vikash is offline Vikash  United Kingdom
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Default Re: Don't stuff a sub.

Quote:
Originally posted by Bose(o)
If you want the best for HT, I know that 16Hz. seems to be the magic number. At least 16-20Hz. for ultimate HT. I guess this would leave less room for being below tuning since there isn't a whole lot of musical information below 16Hz. ( yes I know there still is, but I'd bet that the LFE channel won't go that low with much intensity to really do damage).
You can't just pull out a number without considering the driver and enclosure you're tuning. At least I didn't think you could.

Quote:
Originally posted by BillFitzmaurice
Damping is a must with shorter frequencies but in subs where the frequencies are all significantly longer than the internal box dimensions (the wavelength at 100 Hz is about 13 feet, and it just gets longer as you go lower) damping does not help. Most manufacturers do so anyway because they're expected to, but not because it works.
The driver may not be reproducing short frequencies, but isn't it possible that resonating enclosure panels might. I think there may be more to why manufacturers do it than because they're expected to.
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Old 2nd June 2004, 10:22 PM   #7
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Default Damping panel vibrations?

If a manufacturer, or anyone else for that matter, is using damping materials to counter cabinet vibrations then the speaker is flawed and damping is the least of your problems; a properly designed and constructed speaker, sub or full-range, should not have panels that vibrate.

There may be another reason why damping material is so widely used in subs, and that would be that the manufacturer automatically put it in under the assumption that it was required without actually testing the speaker to verify its efficacy. I tested my subs with and without, they work better without, so my subs don't have added damping materials.
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Old 2nd June 2004, 10:25 PM   #8
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So your saying that i should use the roofing felt to damp the walls but not use the wool/insulation at all.

Can you try and not confuse me this is my first speaker and i've only done standard grade (GCSE) physics.

Thanks for the help so far
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Old 2nd June 2004, 10:32 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Dannyball
I have a huge roll of roofing felt for the inside walls and a roll of cotton wool.

Should i just line the inside walls with the felt and the wool?

For the tunning frequency of the vent WinISD has given me 34Hz but someone recomended 28Hz, how should i chose?
I was probably me that recommended a lower tuning than WinISD
gives, I like mildly overdamped bass alignments, they suit most
rooms better and they go lower, so IMO go with 28Hz.

Adding roofing felt to the walls is not necessary. As BF has stated
airspace damping is not strictly required in subs, but if you do it
apply the cotton wool to at least 3 non parallel walls, for each axis.

sreten.
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Old 2nd June 2004, 11:32 PM   #10
oracel is offline oracel  Norway
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Smile Re: Damping panel vibrations?

Quote:
Originally posted by BillFitzmaurice
If a manufacturer, or anyone else for that matter, is using damping materials to counter cabinet vibrations then the speaker is flawed and damping is the least of your problems; a properly designed and constructed speaker, sub or full-range, should not have panels that vibrate.

There may be another reason why damping material is so widely used in subs, and that would be that the manufacturer automatically put it in under the assumption that it was required without actually testing the speaker to verify its efficacy. I tested my subs with and without, they work better without, so my subs don't have added damping materials.
I believe you forget that there are more reasons to adding damping materials than just attempting to reduce cabinet vibrations (I assume you mean unwanted vibrations as a consquence of using something like cardboard for cabinet material). Allow me to list a few very good reasons for experimenting with and using damping:

1. Damping high frequency reflections from inside the cabinet that would normaly escape the cabinet through the membrane as sound distortion. This is mostly relevant with frequencies > 100-150Hz.

2. Reduce or distribute standing waves throughout the cabinet.

3. Lower the cabinets Q value. This will make the cabinet look "bigger" to the driver, and it will behave equally. Afaik, many cabinet calculation programs supports the addition of damping material to the final calculations, giving a good impression on this effect. This is a good behaviour if you are, for instance, designing a closed cabinet that has to be as small as possible.

Of course the lack of damping material will indeed create a more "wild" and uncontrolled bass with alot of thunder and action that alot of untrained ears seem to have a certain liking for. I hope my post will make you give damping another serious try.
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