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Multi-Way Conventional loudspeakers with crossovers

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Old 7th September 2004, 10:37 PM   #11
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I use the W22s and Millenium for my main speakers and center and the L21 and Seas 27TDFC for my surrounds.

It is surprising how little sound goes into the surrounds, even with SACD and DVD-A. Switch off your mains one day and have a listen.

I use the Behringer DCX2496 for crossover and EQs so I can tweak everything.

Steve
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Old 8th September 2004, 02:25 AM   #12
Ken L is offline Ken L  United States
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Quote:
Originally posted by sfdoddsy
It is surprising how little sound goes into the surrounds, even with SACD and DVD-A. Switch off your mains one day and have a listen.
Agreed


There is so little information in the rears on _most_ DVDs that IMHO, it is a questionable use of resources to max out the rears.

Been there, done that, got the t-shirt _big grin_

Regards

Ken L
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Old 8th September 2004, 04:00 AM   #13
tktran is offline tktran  Australia
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I'll chime in here too- agreed 110%.

OTOH in most DVDs the centre gets so much action!

Either go without a centre (use processor to mix centre into front L/R) or use one at least as good as your L/R.
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Old 8th September 2004, 07:26 AM   #14
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Quote:
Originally posted by Drew Eckhardt


Nope.

Monopole excursion limited output adds a 40 log f term, meaning excursion is quadrupling with each octave decrease in frequency. The additional compensation for dipole roll-off at 6dB/octave nets you an octupling of displacement requirements for each octave decrease in frequency.

2/3 * 8 = 5.3X displacement change

Or at constant displacement, maximum output decreases

2/3 * 18dB = 12dB

Sources:

Linkwitz spreadsheet
Linkwitz forumula
DIY subwoofers sealed forumula
Monopole displacement should double per octave and this is equivalent to 6d/octave. This is why a first order HP slope maintains constant excursion. Now if there were 4x displacement / octave, then this would mean a 2nd order crossover would in fact maintain constant excursion and would not prevent tweeters from overexcursion.

We concur on the dipole side of things, but differ regarding the above.

Now if someone can point out any errors in my logic or information, please do so!
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Old 8th September 2004, 09:53 AM   #15
Pan is offline Pan  Sweden
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Monopoles excursion increases with 4x/octave to maintain 0dB spl. So, a true 1st order acoustic slope will not have constant excursion but increasing excursion as we go down in Fr.

A 2nd order slope will have constant excursion for a monopol (and 12dB/oct rolloff). So for a driver crossed well above its fundamental resonance we need 3rd HP in order to decrease the excursion as we go down in Fr.

A dipole will need to have 8x the excursion (18dB) for every halving of octave in the range where the 6dB/oct spl rolloff occur.

/Peter
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Old 8th September 2004, 12:10 PM   #16
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Can anyone point me to some info that shows if it is 2x or 4x excursion / octave? (Drew, I had a look at those links, but didn't find anything, unless I missed something)
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Old 8th September 2004, 01:18 PM   #17
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Peter us correct. Displacement goes like (1/f)^2 above resonance (mass controled region) for a sealed box. For a dipole it goes like (1/f)^3.
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Old 9th September 2004, 04:34 AM   #18
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Well, I looked at the specs on my Rotel RMB-1066 and found out that I have 6 channels x 60W. I had been running it at 3x150 for a while now.

So, I really only need 8 more channels at 60 W of power each - which I'm not likely to find in just one amplifier.

Sigh.

I also have a Mark Levinson ML-9 two-channel amp with scads of current/voltage (I think that an old issue of Audio actually arc-welded with one). The ML-9 was rated at 100 W, but I'm guessing that it was good for a lot more. It's probably unusable in this setup, since I can't control the amount of gain on the ML-9.

I'm not too familiar with amplifier designs. When I adjust a level control on an amplifier, I assume that I'm linearly adjusting the slope of the gain (gain factor), correct? For a 60W amplifier, the 60W would always be available, but I may need a higher line-level voltage to get there.

The reason I'm asking is because I'll need to match my 60W/channel Rotel with another amplifier. I'm thinking that just because they are both 60W/channel doesn't mean that they'll get there at the same time for a similar input level. So, I need to probably take a signal generator to all the amp channels and measure outputs at different levels to try and get a matching set of 14 channels.

Am I correct with my thoughts on this?
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Old 9th September 2004, 05:35 AM   #19
DougL is offline DougL  United States
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Quote:
Am I correct with my thoughts on this?
You are spot on. Power and voltage gain are not necessarly the same. You have the correct idea to measure them. And if the ML can drive dificult loads, it could drive both woffers. Just a thought.

Doug
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Old 9th September 2004, 01:53 PM   #20
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The amp requirements for triamped dipoles are significantly less than one amp driving a whole three way through a passive crossover. There's a bunch of stuff on this on SLs site, but your 60w will be fine.

I'm not sure how you are doing the crossover, but it makes no difference where you adjust the gains as long as they are equal coming out. In other words if you have an amp that is twice as sensitive as another, simply reduce the gain going into it. There are many ways to attenuate a signal.

Cheers

Steve
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