Looking for a 20hz sub for an already existing custom enclosure - AVS Forum
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post #1 of 8 Old 03-12-2013, 02:50 AM - Thread Starter
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I have a 5.8 cubic foot enclosure with two 4 inch aero ports tuned to 20hz and has a flush mount with a dayton HO 15 in it but am somewhat unsatisfied and able to over drive it too easily in the low end at high volume (can hear the aluminum plate hitting something ). Not sure what I should replace it with and more importantly what can I replace it with that will fit the enclosure because I tried putting in one of my 15 Titanics in to it and would not fit unless I took off the rubber covering on the rim of the sub. The enclosure was custom made for the dayton ho for me by Dave the box guy so of course it's a perfect fit for the ho and also limits the rim size for a replacement sub and also some depth.

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post #2 of 8 Old 03-12-2013, 08:29 AM
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What amp are you using?
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post #3 of 8 Old 03-12-2013, 10:20 AM - Thread Starter
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I have 3 different amps I can use with it and each one seems capable of pushing it over, have a Behringer Epx4000 which I use for 2 15 titanics, Dayton Audio SA1000, and a buttkicker bka-1000n.
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post #4 of 8 Old 03-12-2013, 10:22 AM
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high pass filter at just under tuning?

Listen. It's All Good.
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post #5 of 8 Old 03-12-2013, 10:56 AM
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The only one with a high pass filter is the sa1000, and that is to much power. (Dont know anything about the butkicker actually)
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post #6 of 8 Old 03-12-2013, 12:38 PM
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Here's an odd-but-worthwhile suggestion - seal the ports and use the new Dayton Ultimax 15" which happens to be on sale for $170.

Comparing the RSS390HO vented vs. the Ultimax 15 sealed, both in a 5.8 cu ft box:
Driver . . . F3 . . . F10
RSS390 . 18.7 . . 15.4 Hz
Umax15 . 20.1 . . 16.7Hz
... with no need for an infrasonic filter to protect the driver below box tune... you hear 15Hz rather than filtering it out.

Now, double your box size and drop tune to 15Hz, and the Umax gets an F3 of 15Hz and F10 of 11Hz. But you like your box...

The key point is that U-max drivers are very conservatively rated for Xmax. 19mm is geometric. Klippel testing puts it in the low 20's and Xmech is ~30mm. Can't find the reference, but this is from PE. You should be able to drive it just as hard as the RSS390HO, but with an extra 15mm of travel before anything hits, so think 800W @ 15Hz yielding 104dB. The HO at that power/frequency is self destructing (at 30mm on its way to 43mm).

Like I said, odd, but not bad at all.

Have fun,
Frank

PS Umax 15's bolt circle's 372mm, so it's closer to the Titanic than the 368mm for the RSS390... but in a 6mm smaller hole.
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post #7 of 8 Old 03-12-2013, 01:59 PM - Thread Starter
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Quote:
Originally Posted by fbov View Post

Here's an odd-but-worthwhile suggestion - seal the ports and use the new Dayton Ultimax 15" which happens to be on sale for $170.

Comparing the RSS390HO vented vs. the Ultimax 15 sealed, both in a 5.8 cu ft box:
Driver . . . F3 . . . F10
RSS390 . 18.7 . . 15.4 Hz
Umax15 . 20.1 . . 16.7Hz
... with no need for an infrasonic filter to protect the driver below box tune... you hear 15Hz rather than filtering it out.

Now, double your box size and drop tune to 15Hz, and the Umax gets an F3 of 15Hz and F10 of 11Hz. But you like your box...

The key point is that U-max drivers are very conservatively rated for Xmax. 19mm is geometric. Klippel testing puts it in the low 20's and Xmech is ~30mm. Can't find the reference, but this is from PE. You should be able to drive it just as hard as the RSS390HO, but with an extra 15mm of travel before anything hits, so think 800W @ 15Hz yielding 104dB. The HO at that power/frequency is self destructing (at 30mm on its way to 43mm).

Like I said, odd, but not bad at all.

Have fun,
Frank

PS Umax 15's bolt circle's 372mm, so it's closer to the Titanic than the 368mm for the RSS390... but in a 6mm smaller hole.
Looked at the dimensions of Umax compared to Titanic and the RSS390 and I'm fairly certain the Umax will fit without a problem into this flush mount

Thank you very much for that input, was actually strongly considering the Ultimax 15. Some follow up questions though to what you suggested... (NOOB ALERT)

Why not leave the ports open? Have two sealed 15 titanics as it is, always thought ported regardless of driver will give better low end output.

This box has no polyfill or anything in it and neither do my two 2 cubic foot sealed enclosures for the titanics, I want to put some in all 3 but what's the ideal amount for each?

Also, what exactly should I plug the ports with?

NOTE ABOUT MY SETUP: Right now I have the RSS390 paired up with the SA1000 amp and frequency cut off to just do 40hz and below, since after measuring with my UMIK it shows at around 37hz and under there is a significant drop in db, have the RSS390 for boosting that low end drop.
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post #8 of 8 Old 03-13-2013, 09:54 AM
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Quote:
Originally Posted by dece870717 View Post

...Why not leave the ports open?
...This box has no polyfill or anything in it
...Also, what exactly should I plug the ports with?...
When using a woofer simulator, one can look at several alignments. The Umax 15 driver works well in 5.8 cu ft sealed.
- 1/2 rated power is just ticklinig Xmax, so no need for low end filters and an opportunity for boost
- System Q is adjustable in the 0.65-0.75 range by adding fill, so response is flat
- a comparably good vented alignment requires 2.5x larger box.... and I don't see a point in an F3 of 13Hz.

Other drivers behave differently.

I use dense fill in sealed subwoofers. Acoustically, fill acts to raise the apparent volume seen by the driver, lowering Q and smoothing out response. You may want to experiment. With 5 cu ft, think 5-15 lb of fill, with a clear area around the driver so it doesn't touch (remember the cone moves +/- 1"). Densities as high as 4 lb/cu ft aren't bad.... Love actual fiberglass, but pillow stuffing is a common alternate. I suggest starting with 5 lb and adding another 5 to see how the sound changes, or just go right to the whole 15lb packed densely into the corners to make room for the driver basket.

Plug the ports with foam. Nerf footballs are popular. Fabric stores that sell piloow stuffing also sell foam.
Quote:
NOTE ABOUT MY SETUP: Right now I have the RSS390 paired up with the SA1000 amp and frequency cut off to just do 40hz and below, since after measuring with my UMIK it shows at around 37hz and under there is a significant drop in db, have the RSS390 for boosting that low end drop.
With a sealed sub, you don't need that filter. the air volume in the box provides the driver with protection from overexcursion. I get strong output, in room, into the low teens, using a bit of boost plus room gain. I can go 1 step lower, but don't see the need... and I start getting untoward sounds. This with a Tempest X driver that's very comparable to the Ultimax 15.

HAve fun,
Frnak
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