7.6 cu.ft Maelstrom- X 18" build - Page 10 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #91 of 305 Old 10-05-09, 05:45 PM
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Re: 7.6 cu.ft Maelstrom- X 18" build

Time to engage the common sense button and back off a bit throttle jockey
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post #92 of 305 Old 10-05-09, 05:59 PM Thread Starter
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Re: 7.6 cu.ft Maelstrom- X 18" build

That's what I did as soon as I heard the distortion as far as I could tell. I am NOT going to hurt my sub haha

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post #93 of 305 Old 10-05-09, 06:36 PM
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Re: 7.6 cu.ft Maelstrom- X 18" build

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sub_junkie wrote: View Post
Yes, I modeled quite a few things in WinISD. I found out that I would need to run a minumum of 3100w to make it reach its Xmax at 24.40hz. To reach it at 30hz, I would need 3600w. 40hz would need 6500w. All of these are asuming at 10hz HPF. Now, I know that the EP2500 can't put out anythig near those numbers, unless the EQ is jacking it up. I checked that in WinISD, and with running 1950w, the Xmax was at 37mm at 21hz. Anything above 27.48hz is in check with the Xmax. That is atill running at 10hz HPF.

There's no way that this problem can't be associated with my bad cable, right?

Thanks again for the help everyone. I really appreciate it.
hrmm... if your modeling is correct, then it sounds like youre getting more power than you think... your amp is rated RMS, so driven into clipping ( I think you said it's indicators are saying it's not though?) it can put out considerably more.... but yeah, volume check!
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post #94 of 305 Old 10-05-09, 06:39 PM Thread Starter
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Re: 7.6 cu.ft Maelstrom- X 18" build

You are correct. When the sub looks like its at Xmax, the EP's clip lights are not on.

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Last edited by sub_junkie; 10-05-09 at 08:08 PM.
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post #95 of 305 Old 10-05-09, 08:11 PM Thread Starter
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Re: 7.6 cu.ft Maelstrom- X 18" build

I forgot to put in my post about the 1950w being at 37mm Xmax at 21hz. That was also with a Parametric EQ at 15hz, with a Q or 1.2, and a dB gain of 5dB. That was incorrect. I had thought that that was what it was set on, but the fc was supposed to be set at 10hz. When its set at 10hz, the Xmax is in check until 12.93hz.

Just wanted to clarify that.

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post #96 of 305 Old 10-06-09, 11:20 AM
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Re: 7.6 cu.ft Maelstrom- X 18" build

I modeled things and you should be fine with most content even with 2000w. However here's the deal, things are not as simple as they are made out to be in a modeling program.

In your alignment there will be 2 spikes in impedance one above and one below the port tune because it's a resonant alignment. A sealed system will only have one. Higher order systems like BP 6th, BP 8th, TH, etc will have 3 peaks or more. The upper impedance high point will occur at about 29hz in your system and should be above 20ohms from 28-31hz, which is a very bass rich region. What this means is that your sub is very efficient right there and the high impedance above 20ohms means that very little actual power is needed to get the subs cone moving like crazy. Only a few hundred watts. Model your sub in WINisd and then look at the impedance tab and the amplifier apparent voltage tab to see what I mean. Then there is also the fact that heating in the vc's and impedance rise can change things as well. Under the driver tab add 140deg to the vc's and watch what happens. If the EP2500 can supply 200w or so into the drivers impedance around 30hz then yes it could cause over excursion.

Also what are you using for a HPF? You'd be safer with it moved up a little to 12 or 13hz. You could get a high level 10-12hz transient that could cause problems if you've got it cranked. It's probably not likely but hey....I'm throwing it out there. Also notice that the second impedance maximum is well below your tuning at about 8.6hz. It requires virtually no actual power applied to the driver there to make it go crazy. 55w applied to the driver at 8.6hz gives 45mm excursion. This is another part of the reason it is ill advised to run a resonant system much below tune.
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post #97 of 305 Old 10-06-09, 01:53 PM Thread Starter
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Re: 7.6 cu.ft Maelstrom- X 18" build

Can I fix any of those issues?? And, even though the HPF is set at 10hz, the bottoms out on the higher fc's in Bass I Love You. It looks well within its limits on the 6hz and 11hz tones even with EQ set at 10hz with a Q of 1.2, and a dB gain of 6.

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post #98 of 305 Old 10-06-09, 03:24 PM
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Re: 7.6 cu.ft Maelstrom- X 18" build

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EQ set at 10hz with a Q of 1.2, and a dB gain of 6.
You're boosting 10 hz with 6 db?




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post #99 of 305 Old 10-06-09, 03:53 PM Thread Starter
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Re: 7.6 cu.ft Maelstrom- X 18" build

A 10hz HPF setting


http://i111.photobucket.com/albums/n.../MIC2200/1.jpg

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post #100 of 305 Old 10-06-09, 05:22 PM
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Re: 7.6 cu.ft Maelstrom- X 18" build

Quote:
Ricci wrote: View Post
I modeled things and you should be fine with most content even with 2000w. However here's the deal, things are not as simple as they are made out to be in a modeling program.

In your alignment there will be 2 spikes in impedance one above and one below the port tune because it's a resonant alignment. A sealed system will only have one. Higher order systems like BP 6th, BP 8th, TH, etc will have 3 peaks or more. The upper impedance high point will occur at about 29hz in your system and should be above 20ohms from 28-31hz, which is a very bass rich region. What this means is that your sub is very efficient right there and the high impedance above 20ohms means that very little actual power is needed to get the subs cone moving like crazy. Only a few hundred watts. Model your sub in WINisd and then look at the impedance tab and the amplifier apparent voltage tab to see what I mean. Then there is also the fact that heating in the vc's and impedance rise can change things as well. Under the driver tab add 140deg to the vc's and watch what happens. If the EP2500 can supply 200w or so into the drivers impedance around 30hz then yes it could cause over excursion.

Also what are you using for a HPF? You'd be safer with it moved up a little to 12 or 13hz. You could get a high level 10-12hz transient that could cause problems if you've got it cranked. It's probably not likely but hey....I'm throwing it out there. Also notice that the second impedance maximum is well below your tuning at about 8.6hz. It requires virtually no actual power applied to the driver there to make it go crazy. 55w applied to the driver at 8.6hz gives 45mm excursion. This is another part of the reason it is ill advised to run a resonant system much below tune.


It seems no matter how much research you do, the game just keeps getting deeper. Going from experimental days of "drop a PVC pipe in there and see what it does. Cut it shorter, try again. How about a 2nd port?" to playing with WinISD... but now it seems WinISD's main transfer function, excursion, and SPL tab don't tell the whole story either? 55 watts from 8-9Hz? A couple hundred from 28-31hz?

Last edited by Ryan Anderson; 10-06-09 at 10:23 PM.
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