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Multi-Way Conventional loudspeakers with crossovers

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Old 15th June 2011, 06:44 PM   #1
chops is offline chops  United States
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Question A 2-way tower with Vifa woofer and Fostex FE103E...

I modifying an old pair of 3-way towers I built years ago when I was 17 (am now 36). They are solidly built with loads of internal bracing, they look pretty good and have amazing bass output which is pretty flat to below 30Hz, if not lower.

Anyway, right now there's a Vifa P21WO-20 8" woofer, an old cheap JBL midrange out of an old center channel speaker I blew years ago, a Bose 2" tweeter, and a high quality Parts Express 3-way crossover. It sounds okay, but nothing great.

I'm going to ditch the midrange, tweeter and crossover and install a new top baffle to fit my FE103E on. I'm going to need to design a simple 2-way crossover between the FE103E and Vifa P21WO-20 8" driver. I have the notch filter that I slapped together a while back for the Fostex drivers which worked out great and will incorporate that into the new crossover.

I'm guessing I'll be setting the crossover point somewhat low around 100-200Hz, and want it to be a simple 1st order, but want the Fostex to cover most of the range, obviously.

The Vifa is rated at 91dB @ 1w/1m, the Fostex is 89dB @ 1w/1m.

What I need to know is what are the actual component values are going to be to get things in the ballpark. That way I can at least get them up and running, then I can tweak things from there.

Many many thanks in advance for any information and help I can get on this guys!
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Old 15th June 2011, 09:03 PM   #2
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Old 15th June 2011, 09:58 PM   #3
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Hey chops, haven't seen you post in a while. Good to see you back.

You might be able to get some ideas for your FAST from this thread. EL166 MTM ML-TL

dave
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Old 16th June 2011, 02:13 AM   #4
chops is offline chops  United States
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Quote:
Originally Posted by dumptruck View Post
Thanks for that link. Totally forgot about it as it's been a while since I've done any DIY work.


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Originally Posted by planet10 View Post
Hey chops, haven't seen you post in a while. Good to see you back.

You might be able to get some ideas for your FAST from this thread. EL166 MTM ML-TL

dave
Hi Dave. Thanks for the warm welcome back. Disappearing from here for a couple years is the result of a girlfriend! LOL She's cool though and lets me do pretty much anything when it comes to my stereo(s).

Stupid question... What does "FAST" stand for?

Also, I read that entire thread, but fail to see what that has to do with my current project at hand. It doesn't talk about the FE103E driver and barely mentions anything about crossover design.
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Old 16th June 2011, 03:20 AM   #5
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Good luck on your build! I built a FAST OB w/ the fe103e for the top and I love them! Let us know your results!
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Old 16th June 2011, 04:35 AM   #6
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Also, I read that entire thread, but fail to see what that has to do with my current project at hand. It doesn't talk about the FE103E driver and barely mentions anything about crossover design.
It is broadly similar to your project & the only one i've done with an XO recently.

XO is very simple. 1 coil, 1 cap in a series configuration. If you are planning on XOing as low as you suggest you may well find a couple plate amps to be cheaper.

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Old 16th June 2011, 04:46 AM   #7
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If you are planning on XOing as low as you suggest you may well find a couple plate amps to be cheaper.
Sort of true, but you could do NPE with poly bypass caps for cheap.
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Old 16th June 2011, 05:04 AM   #8
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There is still the 15-20 mH choke each side.

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Old 16th June 2011, 05:34 AM   #9
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Yeah, you're right - the inductors would still be a lot... A 6.8mH for a 200Hz first order, would be the cheap end, and that would be what... $30-35/side including the caps? Not great, but not so terrible either. 400Hz or so would drop it to around $20.. I'm not so much arguing with you as thinking out loud here, but I don't think I'd go with plate amps.
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Old 16th June 2011, 05:49 AM   #10
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Let me think along with you.

I needed 3mH on the MTM with 4 ohm woofers XO 300-350Hz. Double that for 8 ohms and then double again for halving the frequency, that's 12 mH. If the XO is pushing down towards 100 Hz you get close to that 20 mH. An iron core choke is going to be a bad idea here, and really low you are going to get the resonance peak to really screw you up (not so bad on the high pass side, as the cap gets more effective as the impedance rises, but 103 Fs is not far from 100 Hz (a bit higher on the last ones i measured).

So if passive an XO >200 Hz. I usually try to put them near the baffle step point.

Cheapest and most elegant solution, is the thrift store or garage sale amp/reciever + a PLLXO. Over the last couple years a couple standouts i scored were a 100w Sharp for $10 and a Technics New Class A (70w) for $5.

dave
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