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New sub tuning?


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#1 of 10 OFFLINE   Geckogeek

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Posted January 03 2007 - 02:30 PM

I bought a DAYTON RSS390HF-4 15" HIGH FIDELITY SUBWOOFER, built a 10.5' ported box with a 26" x 6" port, braced and stuffed, and have a 300 watt rms amp running it.
The sub seems to be maxxing out when the action gets heavy during movies.....trying to push its guts out (what it looks like) and doing this it makes a hollow sound like tapping on a driver with your hand. I've got the eq set at 50hz and the gain down, but it does this at what I would consider not a very loud level. Any ideas? Is the box too big or not tuned properly? I got the box dimensions with help from another site.

Thanks, Joe

#2 of 10 OFFLINE   Robert_J

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Posted January 04 2007 - 01:40 AM

Your sub reaches maximum excursion at 30hz with 300w of power. I'm not sure what you mean by "EQ set at 50hz". If you have some sort of boost enabled, then you are reaching max excursion even higher in the frequency range.

Quote:
Originally Posted by Geckogeek
I got the box dimensions with help from another site.
The Shack, AVS or HT Guide? This sounds like one of Steve's LLT designs.

The Dayton sub is a good sub but you are just overpowering it in such a large box. Either cut the power down or step up to a better sub like the TC-2000, RL-p, or Fi.

-Robert

#3 of 10 OFFLINE   Geckogeek

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Posted January 04 2007 - 07:51 AM

Thanks for your help....I got the box design from "Home Theater Talk". The eq is the one on the amp....I'm assuming it will keep the sub from playing higher than 50hz.
I think I got it figured out again with help from the above mentioned site....my plate amp has 6db of boost at 30hz built into it......so I need to do a little soldering to flatten it back out when I find the instructions.

Thanks again

#4 of 10 OFFLINE   Robert_J

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Posted January 04 2007 - 10:24 AM

50hz is your cross-over frequency. Turn that up as high as it will go and let your receiver's LFE output filter everything.

What plate amp are you using?

-Robert

#5 of 10 OFFLINE   Geckogeek

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Posted January 05 2007 - 12:07 AM

My amp is from parts express, 250w with bass boost, AB Class, rumble filter etc. I tried to link it to this page but it wouldn't let me.

#6 of 10 OFFLINE   Mattak

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Posted January 06 2007 - 06:36 PM

How long is the port?

#7 of 10 OFFLINE   Robert_J

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Posted January 08 2007 - 02:58 AM

Quote:
Originally Posted by Geckogeek
My amp is from parts express, 250w with bass boost, AB Class, rumble filter etc. I tried to link it to this page but it wouldn't let me.
This amp? http://www.partsexpr....number=300-796

Use the included documentation with the amp to remove the bass boost. No wonder you are bottoming out the sub.

-Robert

#8 of 10 OFFLINE   Brent_S

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Posted January 08 2007 - 11:31 AM

Ok, we need a few more details to trouble shoot this properly.

First of all, do you have a sound level meter? We need to know how loud it's playing when you don't consider it very loud. Tell us what tone source or movie your listening to when you take the reading, including distance.

How much stuffing did you place in the cabinet? Is there an unimpeded path between the driver and port?

Is the 10.5 ft^3 net after bracing/driver/port or gross before you added stuff?

Have you checked the cabinet joints, including driver and amp openings for air leaks?

Assuming your 10.5 ft^3 is net, WinISD says your sub will reach Xmax with less than 250 watts in the 20-26hz range. However, folks over on PE's TechTalk board say the 15" Ref drivers have 21mm of mechanical excursion. In other words, even with 300 watts continuous, you shouldn't bottom this driver based on the cabinet you've described. You still don't need the bass boost unless you just like the sound...you're f3 is around 17hz and your'e only -.5db @ 30hz.

I've never clipped an amp, but I've read that it can make bad sounds of its own that some confuse with the sound of a bottoming driver.

Brent

#9 of 10 OFFLINE   chuckg

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Posted January 12 2007 - 07:59 AM

Quote:
Originally Posted by Brent_S
I've never clipped an amp, Brent

Really? Then you're just not living right! grin grin.
--ignore the man behind the curtain

#10 of 10 OFFLINE   Brent_S

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Posted January 12 2007 - 12:11 PM

Quote:
Originally Posted by chuckg
Really? Then you're just not living right! grin grin.

Figured somebody'd have to take a shot at that. Posted Image

In all seriousness...my main amp, an Adcom 5 channel, has warning lights on each channel to indicate when that channel is approaching 1% distortion. In order to even get them to flash briefly, my SPL meter is reading 110+ db peaks with stereo material at the sweet spot. For me, that's well into pain territory and is in the mandatory hearing protection category on OSHA's noise exposure chart. My typical movie watching level produces roughly 95db peaks on something like a THX intro.

-Brent


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