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Multi-Way Conventional loudspeakers with crossovers

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Old 19th October 2012, 09:18 PM   #221
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The phase margin at gain=1 @MHz ?
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Old 19th October 2012, 10:42 PM   #222
Remlab is offline Remlab  United States
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Originally Posted by SY View Post
OK, so one more try- how do we deal passively with a woofer to match its spl with a less sensitive mid and tweeter without affecting the efficiency of the alignment? Clearly, a series resistance won't fulfil the challenge.
Glue dumbbells to the woofer cone?
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Old 19th October 2012, 10:58 PM   #223
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Quote:
Originally Posted by James Lehman View Post
Using a transformer is a bad idea. If the woofer, mid and tweet all are the same nominal impedance to start with then that will get all screwed up with a transformer on the woofer. The only way to compensate for that is to give the low end current another path around the woofer. Bad idea! There goes your SPL!
The whole POINT was to answer your question about altering the SPL of the woofer relative to the rest of the speaker. That's what it's SUPPOSED to do. The transformer does so without any change in efficiency or the alignment. Yes, it changes the impedance- so what? Let's say you have an 8 ohm nominal woofer that needs a 6dB reduction in sensitivity. Its impedance will vary from (say) 6 ohm below resonance to maybe 30 ohms at resonance to 10 ohms above resonance; these are not atypical numbers. 2:1 stepdown means 4:1 impedance transformation, so the speaker impedance ends up varying from 1.5 ohm below resonance to roughly 8 ohms at resonance to 2.5 ohms above resonance. A decent SS amp will have zero problem with that- its source impedance is low, well under 0.1 ohm. So.. the passive solution works. It's not convenient- a big bass transformer is heavy and bulky, and biamping will be cheaper- but it's absolutely doable if you want a passive solution.
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Old 19th October 2012, 11:34 PM   #224
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I understand that many years ago B&W used a transformer to lower the sensitivity of the 10" bass unit in their 3 way DM6 (also known as "The Pregnant Penguin". If you ever see a photo of a gloss white version you'll see why.). The cross over was published somewhere here a year or two ago.

Edit; and just for completeness the thread is; DM6 Recap. Post #1 24 June 2011.
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Last edited by Jonathan Bright; 19th October 2012 at 11:38 PM.
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Old 20th October 2012, 12:29 AM   #225
Remlab is offline Remlab  United States
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Why would Linkwitz say this as a simple "Case closed" statement if it wasn't true? He is an an authority on active vs passive if there ever was one. Yet he claims that the reason is quite simple..

"Crossovers may be implemented either as passive RLC networks, as active filters with operational amplifier circuits or with DSP engines and software. The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time, if accuracy of reproduction is the goal."
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Last edited by Remlab; 20th October 2012 at 12:34 AM.
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Old 20th October 2012, 01:13 AM   #226
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Linkwitz is hardly an irrefutable source on the subject. "A little biased, me thinks"
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Old 20th October 2012, 01:29 AM   #227
Remlab is offline Remlab  United States
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Linkwitz is hardly an irrefutable source on the subject. "A little biased, me thinks"
Hardly an irrefutable source? He knows at least as much about crossovers as you do about HOMs. Maybe even more..(Trying to be funny. Kind of.)
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Last edited by Remlab; 20th October 2012 at 01:33 AM.
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Old 20th October 2012, 01:54 AM   #228
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I don't care.

I have "passive" capacitors in series with tweeters, LC filters for woofers and for subwoofer, but before corresponding power amps. Digital Audyssey does for me the rest.
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Old 20th October 2012, 03:50 AM   #229
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Neither do I, but that's not what I was getting at.
Well, what were you getting at?
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Old 20th October 2012, 04:16 AM   #230
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Quote:
Originally Posted by James Lehman View Post
Oh. That's nice. Screw up the impedance of the whole system.
Are you serious?

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