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How much can an air leak of this kind reduce the performance?


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#1 of 4 ClaudeL

ClaudeL

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Posted December 28 2003 - 03:26 PM

Hi,

I finished my Tumult sub last week (but without the wood veener finish yet). If you remember, I wrote a post about the Tumult gasket, if alone it would be enough. So I tried the sub without any other gasket. The first time I played a song, I could hear really bad air leaks around the woofer but it was due to me, who didnt place the woofer well into the hole (I almost dropped it :B)!!! So I unscrewed the woofer, and I screwed it for a second time. And this I didnt touch it since then. Now, I can hear again one or two air leaks around the woofer, but it is not as worse as before. I just hear the air coming out of one or two screws when I play the subwoofer at a loud volume or when I fire very low test tone (16-25 Hz). It was during the low test tones that the air leaks were the most noticable due to the bass which is less audible.

From that point, in a 1500 cubic ft room, corner placed and this is by the way the best placement, I get only 110 dB at 20 Hz, no more. If I push the sub volume farther, it just makes bad noise, air leaks or distortion. I can get about 1 or 2 more dB when the sub is sit on the floor (it is placed presently on a piece of furniture but still in a corner). I expected more output than that. When you look into simulation softwares and that you compare a sealed (Q of 0,6) Tumult powered by a 2400W amp to a SBB4 Tempest powered by a 300W amp, you can clearly see that the Tumult is not SOO far behind the Tempest in output at 20 Hz. I could get about 115 dB with my Tempest at 20 Hz, so you see why Im disapointed.

Do I expect too much of my Tumult??? Does these air leaks around the screws can drop that much its performance? Its not like a LOT of air come out (around air leaks), you can feel it just a little with your fingers but again, the sub must be pushed quite loud (at about 1.5 to 1.75 inch of peak to peak excursion).

I plan to buy a neoprene gasket + the wood veneer soon. Im pretty sure than with the new gasket, the main air leaks around the woofer will be gone away. But do you think that with the wood veener, other kind of possible air leaks (behind the sub, sides, etc) can be gone away too? Afterall, the wood veneer will cover the entire surface... But I didnt detect air leaks anywhere else than around the woofer.

Quite a lot of question anywhere, I hope that you wont be lost in that post Posted Image

Thanx for any inputs!

#2 of 4 Hank Frankenberg

Hank Frankenberg

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Posted December 29 2003 - 12:02 AM

1. You have excellent hearing to be able to hear air leaking out around a screw.
2. Why would you want more than 110 dB??

Seriously, you can buy some closed-cell foam weather seal at a harware store or Home Depot type store and place it over the factory gasket. I use that stuff all the time and have not had any screw hole leaks. Good luck.

#3 of 4 ThomasW

ThomasW

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Posted December 29 2003 - 02:49 AM

As I recall I posted to your thread that using the stock cosmetic gaskets wasn't a good idea.

Regardless of size any air leak will have a negative impact on the performance of the sub. The cabinet must be air tight.

Until you have the leaks stopped commenting on the sub's performance is a waste of time

#4 of 4 ClaudeL

ClaudeL

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Posted December 29 2003 - 06:08 AM

Quote:
1. You have excellent hearing to be able to hear air leaking out around a screw.


Yes I have Posted Image But when you use low test tones (16-25 Hz), because you dont hear so much the bass and you most likely feel it, its easier to detect any kind of air leaks. During a 20 Hz test tone, it was VERY obvious that the air leaks came near the woofer. And when I put my ears near it, I know that its all about the Tumult gasket.

Quote:
Why would you want more than 110 dB??


Because I am a bass FREAK!!! I know that I will have to build another enclosure for the Tumult later, a passive radiatored one. I would like 120 dB @ 20 Hz. But of course, I dont listen LOUD everyday to my music. Only on occasions, and not a lot of time each time.

Quote:
As I recall I posted to your thread that using the stock cosmetic gaskets wasn't a good idea.

Yeah, and I thought about your post a lot of time. Brian Bunge (I hope that I spell it right) doesnt seem to have any problem by using only the supplied Tumult gasket. So I said to myself: why not using that gasket first and we'll see after... and now I see! :b

I dont know if its unthinkable, but I hope to get near 113-114 dB once the new gasket will be bought and once the sub will be really finished and a 120 dB+ somewhere else, near and in the mid-bass region. Therocally, I should get these numbers but pratically...





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