Need help desining subwoofer enclosure for 2 x 15" subs. - Page 5 - AVS Forum
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post #121 of 135 Old 04-02-2014, 10:17 AM
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if this is your amp:

http://www.crownaudio.com/media/pdf/legacy/133617.pdf

then wiring for 2 ohms will give some more power than in 8 ohm stereo mode, but obviously the amp isn't 'doubling down', so it isn't really designed to be run full out at 2 ohms per side. for most, it would probably be fine.

looks like the dcr is 2.24 ohms when wired for 2 ohms, so that will present an easy '2 ohm' load to the amp.

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post #122 of 135 Old 04-02-2014, 10:26 AM - Thread Starter
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It doesn't quite look like above that but yeah...

It definitely says XLS 402 on the front. I've had it for a decade. Used it to drive some PA speakers for parties, and used as a PA amp when I used to jam. I'm phasing out all my pro audio equipment, but this is left over and not used for anything currently. If it would work I would dedicate it to a sub in the garage, which might get moved outdoors for parties and such. If not, I'll search down a better solution.

It looks like this:

images?q=tbn:ANd9GcTh1YdwNz-5K4YvTerASshpTpGC24drlddYmSoiC2N4vh0e-Nys

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post #123 of 135 Old 04-03-2014, 06:33 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

if this is your amp:

http://www.crownaudio.com/media/pdf/legacy/133617.pdf

then wiring for 2 ohms will give some more power than in 8 ohm stereo mode, but obviously the amp isn't 'doubling down', so it isn't really designed to be run full out at 2 ohms per side. for most, it would probably be fine.

looks like the dcr is 2.24 ohms when wired for 2 ohms, so that will present an easy '2 ohm' load to the amp.

Thanks. I'll give 2ohm stereo a shot and see how it works. 8ohm stereo was already enough to challenge the structural integrity of the garage eek.gif

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post #124 of 135 Old 04-05-2014, 07:26 PM - Thread Starter
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Wow! 2ohms for the win. In a million years I'd never have guessed this big of a difference!

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post #125 of 135 Old 04-10-2014, 01:21 PM - Thread Starter
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Another quick question,

Is there a way to measure or determine actual port tune ? I mean after a box is built ?

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post #126 of 135 Old 04-10-2014, 01:24 PM
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Yes
it appears as a peak on an impedance sweep

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post #127 of 135 Old 04-10-2014, 01:29 PM
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A quick way to find the tune is to have a look at the drivers excursion while playing tones or a sweep. At tuning, the driver excursion will be much less.

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post #128 of 135 Old 04-16-2014, 10:23 AM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post

I think I made the port 55" long but I can't remember exactly...

I am trying to reverse engineer this to determine exactly what "tune" I have on my port but I am struggling since I am not sure about a few things. Here is what I remembered : (I changed some in build process)
Quote:
I think I am going to make it 24" deep by 24" wide by 42" tall. That is about 14 cubic feet before the port and speaker.

The port will be 21.75" x 4" (24" wide minus 3/4" each side+ 3/4" brace down center) and run the full width and depth almost. It will be about 38" long - (24" deep minus 4" = 20" + go down about another 18" to get me to about 38" or whatever exact I need for a 20hz tune)

I figured the port would take up 38"x22.5"x4" [3.16666' x 1.875' x .3333' ] or 1.979 cubic feet. <--- DID I DO THIS RIGHT ???

Minus the woofer puts me around 11 cubic feet I'm guessing after bracing- I'll look closer at it when I get to the port length to get it exact. 38" puts me about 21hz I think

I don't think I used a port length of 38" thougt. I thought it was 55" - which I think was because I made the box volume different, or I had calculated it wrong.

I just took a look at the box volume calculator here:

http://www.hometheatershack.com/forums/enclosure-volume-calculator/

I entered in 24" Wide by 24" Deep X 42" TALL
Then I entered .75 for the material thickness.

Bracing volume I entered 360 inches/3 ( I think I figured this was 4" wide x .75 material by 24" long times 6 of them) this seem right for about how much bracing volume it should be ?

Port Volume I used 4500 inches/3. This again was a guess. I factored in 21.75" x 4" x 53" = 4611 (or something like that I remembered)

Drive volume = .3

Drivers = 2

The calculator spits out about 8.99 cubic feet volume with these figures. So it appears my box is about 9 cubic feet of volume. Anyone see anything that is a mistake or wrong above ^ ? Or does that look about how is should ?

If I did make the port 53" long then my tune should be pretty close to 20.5hz right ?

You think this is something I could measure by putting some white out on the cone and watching for the least excursion and what frequency it happens at ? Is that really accurate?

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post #129 of 135 Old 05-17-2014, 05:18 AM - Thread Starter
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I have another question :

When I built this box I didn't seperate the woofers and they share the same volume internally - is this a problem running them each on their own amp channel ?

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post #130 of 135 Old 06-05-2014, 06:36 PM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post

I have another question :

When I built this box I didn't seperate the woofers and they share the same volume internally - is this a problem running them each on their own amp channel ?

Anyone ?

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post #131 of 135 Old 06-09-2014, 06:45 AM
 
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no, just don't only run 1 driver or it could over-exert itself.
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post #132 of 135 Old 06-12-2014, 08:40 AM - Thread Starter
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My amp has separate gains for left and right channel so that's why I figured I'd ask.

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post #133 of 135 Old 07-13-2014, 03:13 PM - Thread Starter
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Here is a pic of the box before bracing:



and on first testing it:



I have some additional questions again. I bought a DSP feedback destroyer but I don't really understand how to set a subsonic filter on it.

I grabbed a Berhringer Feedback destroyer PRO DSP1124P from Guitar Center for $39. I want to enable it on this dual 15" sub box. My amp I am using is a CROWN XLS402 and it has nothing for subsonic filtering or EQ or any of that.

This is what I bought

http://www.behringer.com/assets/DSP1124P_P0124_M_EN.pdf

Anyone used one ? Can I get cliff notes on how I should set it up ?

It's the dual 15" big box one on the left in the above picture. I just don't want to damage it if it gets pounded on so I'd like a nice EQ solution to provide max output for music but also protect the driver under my 20hz port tune. How do I set it ?

It looks like the unit I bought actually only has setting for 20hz-20khz. Is there a way to just cut the lower frequencies with a big cut, but still boost my port tune of 20hz a tad so it's flat or slightly heavy instead of lower ??? Can I do that with multiple filters or EQ settings?
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post #134 of 135 Old 07-17-2014, 11:31 AM
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Quote:
Anyone used one ? Can I get cliff notes on how I should set it up ?
A lot of us bought one before the miniDSP became popular. I still use mine. What measurement tools do you have? Analog Radio Shack SPL meter is minimum. Calibrated mic and Room EQ Wizard is best. Without proper measurements, you can't set this up.

Quote:
I just don't want to damage it if it gets pounded on so I'd like a nice EQ solution to provide max output for music but also protect the driver under my 20hz port tune. How do I set it ?
It's an EQ only. Not a high pass filter.

Quote:
It looks like the unit I bought actually only has setting for 20hz-20khz.
You can tweak the center frequency down to 17hz.

Quote:
Is there a way to just cut the lower frequencies with a big cut
Not really.

Quote:
Can I do that with multiple filters or EQ settings?
It does have multiple filters and I used 5 or 6 for a flat response. You can also save different response curves in memory.
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post #135 of 135 Old 07-17-2014, 11:33 AM - Thread Starter
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Quote:
Originally Posted by rlj5242 View Post
A lot of us bought one before the miniDSP became popular. I still use mine. What measurement tools do you have? Analog Radio Shack SPL meter is minimum. Calibrated mic and Room EQ Wizard is best. Without proper measurements, you can't set this up.

It's an EQ only. Not a high pass filter.

You can tweak the center frequency down to 17hz.

Not really.

It does have multiple filters and I used 5 or 6 for a flat response. You can also save different response curves in memory.
Thanks! I am starting to figure it out. It's not ideal but it works.

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