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Multi-Way Conventional loudspeakers with crossovers

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Old 28th December 2007, 09:49 PM   #11
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I will look at the data sheet for the impedance values... I don't think that I will be finding any schematic for the Sonus Faber Xovers, I'm going off of what they listed (which may be vague?)

"2.5khz, non-resonant acoustic first-order, optimized acoustic phase response, highest-grade components"

maybe sombody can tell me what this means and give me a little guidance on my X-over design, since my values are wrong then maybe I won't have to parallel any Caps!
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Old 28th December 2007, 10:04 PM   #12
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hmm... I can't read this graph too well but it looks like the impedance of the mid @2500hz is 6ohms??

tweeter impediance looks like 3.5ohms @ 2500hz

i'm looking at the tymphany site with the 5.5 revelator mid and the 7100 revelator tweeter
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Old 28th December 2007, 10:11 PM   #13
jnb is offline jnb  Australia
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Quote:
Originally posted by StefanPoPolsku
"2.5khz, non-resonant acoustic first-order, optimized acoustic phase response, highest-grade components"

maybe sombody can tell me what this means
The crossover is done by requiring the drivers response to be first order, and using whatever electrical components are required to do the job. This doesn't necessarily mean you have a first order crossover in the text book sense.

Unless you're prepared to graph the electrical and acoustic properties of the drivers, you're only guessing.

If you want to produce a makeshift crossover, you could develop a zobel impedance compensation network for your woofer first, then add a textbook first order crossover. Tweak until you find something you like.

Quote:
Originally posted by bzfcocon
Is there any reason why paralleling is bad ?
There are some good threads here about this, some get quite technical. The issue in a nutshell is resonances between the caps involving stray inductances. IMO this is less of an issue with speakers, but still a matter of trial/taste.

I am thinking that the accuracy of the extra 0.9uF is a little pointless in this case due to the expected inaccuracy of the crossover design at this point.
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Old 29th December 2007, 12:07 AM   #14
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I can get the measurement tools from a friend, but was hoping to use the data listed on their website
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Old 29th December 2007, 02:43 AM   #15
jnb is offline jnb  Australia
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You can take a published frequency response plot and add the effects of the enclosure on the bass, and the effects of the baffle (baffle step). These both can be simulated with reasonable results.

Rarely do you find published phase data, and with baffle effects it would probably be inaccurate for individual cases, anyway.

Published impedance data correlated with simulated in box impedance data at the low end, should get you close. You probably wont find impedance phase data, though, and this will make your crossover design inaccurate, however you can measure this data with a normal sound card and no mic, so it isn't as painful.
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Old 30th December 2007, 01:06 AM   #16
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The natural driver roll off is 2nd order (-12dB/oct) so a 1st order XO will morph to a 3rd order at some point. Not quite sure how you "optimize the phase response" using a 1st order XO but hey, I'm not a marketing type.

The driver impedance is very important as this will change the performance of a 1st order electrical XO greatly. As will the actual value of the capacitor/inductor.

Don't believe what is written on the component. Measure it. You'll be surprised how "off" the value is. Personally, I buy several parts of values around the target as well as a few "top-up" values. If you need 14.7uF and your 15uF cap is actually 13.9uF you can add a 1uF cap that is actually 0.8uF to get it dead nuts. Make sure you balance left & right.

As for paralleling/seriesing caps, if they're the same brand/product line then you can pretty much mix any values you like. That's all the mfg is doing when they make bigger caps, really. The issues come in when you mix brands and one cap has low esr over one freq range and the other has low esr over a different range. But this is not usually a problem in the audio band - with good quality parts of course. If you're cannibalizing that 1950's radio for parts well then, your performance may vary.
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Old 30th December 2007, 02:54 AM   #17
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Quote:
Originally posted by Iain McNeill
Not quite sure how you "optimize the phase response" using a 1st order XO
Amongst the options, you could create a second order electrical filter with an especially low Q factor tuned above the crossover point, which is chosen to be below the woofers natural rolloff. If done right this can behave like a first order acoustic for an octave or so.
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