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Old 6th March 2017, 10:05 AM   #521
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I'm building an open baffle speaker with twin Eminence 15A Alphas, a Fostex FE168es mid and a yet-to-be-selected tweeter.
Q1. For best sound quality, should the woofers be parallel or put in series? (So the impedance would be halved or doubled, respectively)
Q2. To follow your method, what adjustments must I make to the other woofer driver properties?
Thanks.
Great tutorial. I'm itching to start.

Doug
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Old 6th March 2017, 09:04 PM   #522
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Brisso57 View Post
Q1. For best sound quality, should the woofers be parallel or put in series? (So the impedance would be halved or doubled, respectively)
Your amp may prefer to provide voltage, or to supply current. If one way sounds better, it's likely to be subtle. Is there something specific you are concerned about?


Quote:
Q2. To follow your method, what adjustments must I make to the other woofer driver properties?
The concern I would have is integrating their radiation pattern into the room. When this doesn't play well with the listening axis response the speaker can become difficult to cross, let alone to get the system right.

Electrically, if you use two drivers in series then treat them as one, doubling resistances and inductances, and halving capacitances.
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Old 6th March 2017, 11:33 PM   #523
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Quote:
Originally Posted by AllenB View Post
Your amp may prefer to provide voltage, or to supply current. If one way sounds better, it's likely to be subtle. Is there something specific you are concerned about?

The concern I would have is integrating their radiation pattern into the room. When this doesn't play well with the listening axis response the speaker can become difficult to cross, let alone to get the system right.

Electrically, if you use two drivers in series then treat them as one, doubling resistances and inductances, and halving capacitances.
Hi AllenB

Thanks for the prompt response.
I have a Yamaha M70 and a Quad 303. I could use either of these, or I could tri-amp, using some class D units.
I note your concern about the radiation pattern, but I guess I'll just have to hear it and judge if it is acceptable. The room is LARGE (hence opting for dual woofers), with a skillion ceiling, sloping down from R 16' to L 9', as viewed from the listening position.
I asked about the dual woofer arrangement out of sheer lack of knowledge.

cheers

Doug
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Old 7th March 2017, 04:58 AM   #524
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Brisso57 View Post
dual woofer arrangement
If you cross below, say, 300Hz then they should be acting as one. Once you go significantly higher than this then their vertical directivity may begin closing a tad earlier than for horizontally. It's difficult to predict whether this will be an issue without measurement.
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Old 7th March 2017, 10:22 AM   #525
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Originally Posted by AllenB View Post
If you cross below, say, 300Hz then they should be acting as one. Once you go significantly higher than this then their vertical directivity may begin closing a tad earlier than for horizontally. It's difficult to predict whether this will be an issue without measurement.
Thanks. I'll try that.
I read elsewhere that paralleling the woofers means the cost of the XO inductors would be cheaper. If there's nothing else either way, then that sounds the way to go.

cheers
Doug
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Old 8th March 2017, 04:59 AM   #526
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I'm awaiting for my resistor too arrive to measure driver impedance.. meanwhile I felt in love with old fathioned Vu meter...

Click the image to open in full size.

Awailable at Alie...

Will the vue meter impact the cross over calculus ?
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Old 8th March 2017, 06:05 AM   #527
AllenB is offline AllenB  Australia
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I doubt it. They are usually used (by DIYers) at various points within an amplifier rather than at the speaker. Even so, if you did you'd find their relative impedance to be high. Look at the specification for input impedance for the board.
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Old 20th March 2017, 12:28 PM   #528
gadut is offline gadut  Indonesia
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I'm playing with my first XO trial, tested on my horn tweeter fostex fd600. I have some inductors value : 0.22, 0.39, 0.82 mH and many capacitor value. I have tried caps filter only up to 5.6uf and i find that the vocal is very dominant. tried 2nd order which is currently use 6.8uf & 0.82mH but i hear annoying resonance.

with tweeter Fs around 500Hz, i tried to make notch filter and use 0.39mH - 220uf (bipolar cap) - 7ohm

now it's more enjoyable, but i'm thinking to play with notch filter LC value. what if i increase L value and reduce C value to get same 500Hz target? is there any variable like Q in notch filter? which one is better from my attach 2 combination, 60uF & 1.5mH or 220uF & 0.39mH where R is the same 7R.

thanks
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Old 21st March 2017, 01:24 PM   #529
AndrewT is offline AndrewT  Scotland
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the impedance plot shows a peak @ ~500Hz indicating a resonance.
But there is also a peak in the response plot @ ~ 700Hz.

I think you should be crossing well above that response peak, or taking steps to EQ the response to nearer flat till you get down to your chosen crossover frequency.

I wonder if a 2kHz cross might be better, if the mid can extend cleanly to fill the new gap.
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Old 22nd March 2017, 01:44 AM   #530
gadut is offline gadut  Indonesia
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@andrew
yes the target is 2kHz based on fostex recommended xo with 12" woofer, but i have no EQ available.

testing some iteration of parts combination last night, it was very interesting. below some scenario:

HP : 5.2uF & 0.6mH.
Notch : 220uf & 0.6mH (0.6R dcr), tried resistor 10R, 3R, 1R and best result to my ear without any resistor. then I tried to change HP inductor 0.4mH & 0.8mH and no significant difference.

also tried in another notch 60uF & 1.5mH with various resistor value, the result is not good.

finally settle on HP 5.2uF &0.6mH with notch 220uf & 0.6mH (0.6R dcr)

my testing is only by connecting the horn tweeter and play Yao Si Ting album, which is the most sibilance recording and many SSSS that really hurt the ears if tweeter is not correct.

15" woofer has 0.8mH in series to reduce the peak above 5kHz and reduce some vocal. without inductor, 15" vocal is too dominant.

now they woofer and tweeter blend nicely in open baffle
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