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Old 10th January 2008, 09:58 PM   #1
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Default 15 inch sub plus FR125

Am I just being goofy in thinking this will work?

If one was to take this sub http://www.partsexpress.com/pe/showd...number=295-470 and but it in a 10 cubic foot box, it will hit around 23-25 Hz with a 4 ohm resistor in series with the driver. Because it is a 4 ohm driver with 4 ohms in series, it would be effectively an 8 ohm driver. A FR125 could be built into this box and put in parallel with the 15 inch sub with appropriate crossovers. Then the system would hit around 23-20kHz.

Is this just foolishness on my part or do you think it is doable?
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Old 10th January 2008, 10:11 PM   #2
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Hello David,

I'm not sure why you would want a series resistor on a woofer. That's not a common practice. What is your idea there?

The FR's will require a separate chamber from the main woofer.

The FR driver is very inefficient so you will likely want 4 per box to keep up to the woofer. A single driver will run out of gas long before the woofer.

You might wish to consider using a plate amp and using the high level outs for the FR's. That will mean using the high level ins. It will give you better overall control of the system and save money on XO's.
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Old 10th January 2008, 10:21 PM   #3
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Ditto what Cal says. Additionally, if you are set on this design, at least use a series passive crossover to mate the 4 and 8 ohm drivers. That is much more efficient than just throwing heat away in a series resistor just so you can use a parallel crossover.
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Old 10th January 2008, 10:51 PM   #4
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Thanks for the comments guys.

The series resistor would effect the Qt of the system, pushing the response of the woofer in the low end down from ~40 Hz in the sealed box to ~23 Hz in the same sized box. This would also reduce the SPL making it easier to match to the FR125 as well as allow a parallel crossover arrangement between the two speakers.
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Old 11th January 2008, 01:05 PM   #5
Nanook is offline Nanook  Canada
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Default perhaps a different approach?

As Cal suggest maybe a sub with a plate amp? I've been looking at building something similar. 12" sub + plate amp per side with an OB full-ranger (+ super tweet if needed). Use the internal (low level) crossover on the sub amp. That way the FR125 need not even try to produce any bass below the crossover point and freeing up your amplifier for the mid and high range.


Happy New Year leadbelly, haven't seen you around here for a bit.

stew
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Old 11th January 2008, 02:55 PM   #6
tinitus is offline tinitus  Europe
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You may consider this nice 10" AurumCantus...might mate nicely

http://www.partsexpress.com/pe/showd...number=296-430

or even the Dayton 15" IB in a dipole

http://www.partsexpress.com/pe/showd...number=295-455


There are a couple of problems with "your" Dayton 15"
Ragged top
Too efficient(?)
Peaked midbass

What you need is BSC, hence a higher xo point around 300hz
Fore that you need a woofer with smooth FR
Bass will probably need to be exstremely tight, not to "overfloat" the delicate FR125
I suppose you may get a decent result with even a simple "6db" filter

But as Cal said, you wont be able to play insanely loud with the FR125...not his words, but something like that
I dont know, but it might help a lot when FR125 is relieved of its bass duties

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Old 11th January 2008, 03:14 PM   #7
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Default Re: perhaps a different approach?

Quote:
Originally posted by Nanook
Happy New Year leadbelly, haven't seen you around here for a bit.

stew
Same to you, Stew. I was away for Xmas for 2 weeks. I only have dialup at my mom's house, so I doesn't make it easy to follow the forum.
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