Passive Crossovers Guide - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 22 Old 03-31-11, 06:06 PM
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Re: Passive Crossovers Guide

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dyohn wrote: View Post
Thanks for the comments. I suggest using the best quality caps you can afford in series with drivers, and film/foil tend to be faster and have tighter tolerances (and to sound better to my ears) but certainly a good sounding crossover can be made using poly caps. As to your questions:

1) Yes. At the very least the tweeter must be protected from too much power at fs.
2-4) No. These components are only necessary when they are, well, necessary. BSC can be avoided with proper front baffle design, notch filters are only required to tame resonances that might be present in some drivers, and Zobels are only necessary when a woofer's impedance rises so much that it affect the crossover performance, which may or may not be the case for every driver. You can test this in any good modelling program.

Cheers.
Thanks dyohn, that is very good information to know.
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post #12 of 22 Old 03-31-11, 06:21 PM
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Re: Passive Crossovers Guide

In this particular driver the nominal impedance is 8 ohms. The impedance IS 32 ohms at the X-over point of 1200 Hz. I had intended to use a Zobel on this driver.
Does the harmonic distortion of the driver plus this added circuitry of X-over and Zobel change for the worse? How about any of the other driver qualities ie: dispersion, freq res, delay, etc.?
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post #13 of 22 Old 04-01-11, 05:41 AM
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Re: Passive Crossovers Guide

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ISLAND1000 wrote: View Post
In this particular driver the nominal impedance is 8 ohms. The impedance IS 32 ohms at the X-over point of 1200 Hz. I had intended to use a Zobel on this driver.
Does the harmonic distortion of the driver plus this added circuitry of X-over and Zobel change for the worse? How about any of the other driver qualities ie: dispersion, freq res, delay, etc.?
That is a hard question to answer, it depends on the driver and it's parameters.
A) the harmonic distortion of the driver can not be changed.
B) the added circuitry of X-over and Zobel are purely to send the correct signals to the driver and present a uniform load to your amplifier.
C) all these other factors should be analysed and compared before you commit to a design.

The manufacturers data sheet should give recommended settings for maximum and minimum crossover frequencies, you should err on the safe side when designing a passive crossover.

Hope this helps.

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post #14 of 22 Old 04-01-11, 10:11 AM
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Re: Passive Crossovers Guide

The driver I'm working with is a:

Woofer, 6.5 inch Peerless 830874 with the PPB cone in the HDS series.

The X-over treatment questions arise over the change in manufacturer's T/S data (significant) and my own testing results using WT 2 woofer tester.
I have minimal testing equipment and can't test harmonics, decay, freq res, etc.
I'm mating the Peerless woofer with a textile dome tweeter:

Seas Prestige 27TDF.

First initial modeling with 1st order X-over showed both speakers with exceptional detail but had some audible peaks in the cross over region and the spl difference of +3db indicates an L-pad for the tweeter.
I'm currently in the 2nd order X-over testing stage and now believe a Zobel and notch filter may be required to achieve a good response curve.
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post #15 of 22 Old 05-11-11, 01:16 PM
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Re: Passive Crossovers Guide

Don't forget that the roll off of the driver can and often does contribute to the db/octave crossover slope so that an electrical crossover of 12db can become 24db with resulting phase changes. Also, if one knows how, a crossover can take into account the inductance change and do without the extra circuitry the zobel adds. The only way "proper" baffle design can eliminate the "baffle step" is by using a large baffle which effects imaging.
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post #16 of 22 Old 05-12-11, 12:10 AM
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Re: Passive Crossovers Guide

Thanks Theresa.
I'm in the listening stage and settled temporarily on 2nd order crossovers for both woofer and tweeter but separated the frequencies an additional 200 Hz to flatten a hump @ crossover. I placed a zobel on the woofer and THAT seems to clear some woofer irregularities in the mids and into the X-over region. I also reversed wiring on the tweeter to phase match with woofer.
I have designed a minimal baffle in an attempt to achieve soundstage and imaging.
Right now I'm pleasantly surprised with their overall performance.
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post #17 of 22 Old 05-12-11, 07:44 AM
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Re: Passive Crossovers Guide

Isn't the gratification of building and designing one's own wonderful? I lived with some Vifa's for years always amazed that I put them together. Now I'm using Eton and ScanSpeak drivers and am even more amazed. I'm going to replace the Eton midwoofers with ScanSpeak Revelators to match my center as soon as Meniscus has the baffles cut and ships them and the drivers to me. I use active crossovers with independent amplification of each driver for the front's and sub's. I'm in high end DIY bliss!

Last edited by Theresa; 05-12-11 at 07:53 AM.
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post #18 of 22 Old 05-12-11, 09:20 AM
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Re: Passive Crossovers Guide

LOL yup, you're high end all right. Any time you use an amp per driver you got yourself a high high end system.
I have no experience with the "Revelator" series of drivers but hear great things about them and observed they are used by high end manufacturers. Cost per unit has a limit for me.
I have a Pioneer AVR and use the MCACC circuits to further adjust response curves beyond the X-over.
I like to think I've got the poor man's "Theta".
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post #19 of 22 Old 05-18-11, 09:24 AM
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Re: Passive Crossovers Guide

Zobel's make crossover design a lot easier. I used them on the last few passive speakers I designed.
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post #20 of 22 Old 01-10-12, 04:59 AM
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Re: Passive Crossovers Guide

In My last speaker proekts I used condensatorless ( Acoustic Reality crosower) filters.
Work perfektly in My TL proekt Scan Speak 18W8531G + twit9900O-Revelator.
My inductors-Mundorf copper foil 1.5mH and 0.12mH
Resistor-Mundorf M-resist.
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