P.A. 18 TH (18tbw100 30x38x22.5") - Page 2 - diyAudio
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Old 13th September 2013, 09:31 PM   #11
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I do think people stress the importance of being perfectly "flat" way too much. ESP when there is EQ available, and when the subwoofer (or any speaker) is placed in a room.
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Old 13th September 2013, 09:50 PM   #12
sine143 is offline sine143  United States
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I agree with this sentiment. but if the *flatness* of your measured response was a result in reduced sensitivity in the LF (without an equivalent decrease in displacement at those frequencies) then it means less overall peak output.

now, if cone excursion between 37and 45 decreased as well, then hell, you've gained flatter, and more peak output (although it will take more power to reach it) as tapped horns tend to exhibit peak excursion within their passband (with a hipass activated).

regardless, I'm liking where you are going. I may very well build a PAL12 (found a pair for 200 even), considering its a small amount of build materials, and low cost. It will be a good first tapped horn build. Thank you for posting your results, and your designs, I love reading of your work

please dont take my posts the wrong way. The only thing that irks me at all is the scale of REW, and thats not your doing lol.
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Old 13th September 2013, 09:52 PM   #13
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Default changing scales on REW graphs

Quote:
Originally Posted by sine143 View Post
Is there any way you can adjust the scale on the REW measurments to match the scale of hornresp? i have no idea why REW rrpresents data on a 10db scale, cause that pretty much makes everything look 'flat'
.
The little plus and minus symbols in the upper left hand corner allow you to change the scales.
The ones in the right hand corner change the phase scales.
Also, the second from right dialog box labelled "Limits" above the screen will let you set the default scales.
You can also turn on the scroll bars to allow the traces to be moved up and down.
.
And, trying to get the graph to match one from HRSP requires that you resize one or the other, but it can sort of be done.

Hope this helps,
Dave
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Last edited by Shadydave; 13th September 2013 at 09:55 PM.
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Old 13th September 2013, 11:20 PM   #14
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Quote:

please dont take my posts the wrong way. The only thing that irks me at all is the scale of REW, and thats not your doing lol.

I'm not. Always looking for constructive criticism!
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Old 13th September 2013, 11:37 PM   #15
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Originally Posted by m R g S r View Post
I'm not. Always looking for constructive criticism!
On that note, if you are trying to max output and extension in limited space, why not a quad of lab12 2x12 ported or twin beefy 2x18's?
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Old 13th September 2013, 11:39 PM   #16
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Power requirements. How much power is needed with those 4 18" monsters to reach that level?

If I had lab gruppen amp with 9-14kw on tap, I wouldn't even bother with all the space tapped horns take up.
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Old 13th September 2013, 11:44 PM   #17
sine143 is offline sine143  United States
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Art himself noted that a pair of his keystones exceed a quad of ported 2x12, in output with similar extension.

granted, they'll take 2kw x 2 at 4 ohms (or more)
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Old 14th September 2013, 12:01 AM   #18
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Originally Posted by m R g S r View Post
Power requirements. How much power is needed with those 4 18" monsters to reach that level?

If I had lab gruppen amp with 9-14kw on tap, I wouldn't even bother with all the space tapped horns take up.
A pair of NU6000's would drive a pair of low-ish tuned 2x18's beyond xmax and cost about $900 including 4U case. But should each be on their own 15a or 20a breaker.

I would model that B&C woofer in a ported box targeting 20mm excursion (one way) on 1500w and see where that gets you for extension and output.

Last edited by turbodawg; 14th September 2013 at 12:08 AM.
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Old 14th September 2013, 12:15 AM   #19
sine143 is offline sine143  United States
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so its your opinion the tbw100 is good to 20mm xmax? wow. that changes things for me a lot, as I was pretty much shoehorning myself into sw115 territory by being unwilling to let sims for the tbw go over 12 mm. (not trying to derail your thread mrgsr, but I'd say thats applicable for you too)
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Old 14th September 2013, 01:31 AM   #20
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Originally Posted by sine143 View Post
so its your opinion the tbw100 is good to 20mm xmax? wow. that changes things for me a lot, as I was pretty much shoehorning myself into sw115 territory by being unwilling to let sims for the tbw go over 12 mm. (not trying to derail your thread mrgsr, but I'd say thats applicable for you too)
Well, they are saying xmech is 28.5mm, so (IMHO), if you aren't super concerned about a bit of distortion when going full tilt, modeling to a target of 70% of xmech (28.5 x .7 = 20mm) & real world RMS amp output (1500w nominal) seems like a reasonable target, assuming you intend to set hard highpass and limiters to keep things from blowing up.

Granted, this is a "low tuned" (~30hz) design scenario where power is reasonably low. I don't think it would be a good idea to tune to 45hz and hit it with 3000w for 20mm excursion, would either burn it out or tear it apart.

My subs xmech at around 20-22mm, nominal xmax 12mm, and have seen plenty of action at the 14-16mm range on a maxed out nu6000 (amp tested 1500w rms, subs 800w rms nominal) without a problem.

Last edited by turbodawg; 14th September 2013 at 01:40 AM.
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