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In Reply to: RE: Bi-amping posted by EmailTim on August 25, 2014 at 09:41:00
The 3.x models don't have a 1:1 ratio of top and bass, it is more like 2:3. But many of us like to elevate bass slightly above the mids so being set for 1:2 (top to bass) is useful.
In the 20.x the crossover is set lower so it is more like 1:1, still, the current demand is more on the bass so even there I would like a stronger amp on the bass.
On my tympani in its original form I could just about make it with a 200 WPC @4 ohm amp for the top. The previous amp had less power into 4 ohms and would run out of steam routinely.
In my current variation on the Tympani, the mids are a 96 db sensitive array of Neo8 drivers. I can power the mids with 30 watts triode but for large scale music I still go back to ultralinear at 60 watts. The XO is at 250hz or 300 hz. That is by no means the actual halfway point in the large scale music I listen to. I believe that for most big classical and rock you need the bass to be well more than the theoretical breakeven would imply. I ended up with a pro amp with 2kw/ch into 4ohms. Under unusual circumstances I even clipped that.
So even if the stats indicate you would need a similar power on top as the bass, the bass will fare better with an order of magnitude more power. A 1kw Emotiva monoblock (4ohms) is not that much overkill. a 100W tube amp for the top is a good beginning.
Follow Ups:
"... The 3.x models don't have a 1:1 ratio of top and bass, it is more like 2:3. But many of us like to elevate bass slightly above the mids so being set for 1:2 (top to bass) is useful. ..."
Hi Satie,
This is from the 3.6 manual, Section 11.3:
"Since the effective crossover point for the MG3.6/R is approximately 250Hz, the power requirements for the bass midrange/treble amps are nearly the same. Therefore, use amplifiers of similar power rating. ..."
Is Magnepan and the manual wrong ???
The 20.x panels are crossed over lower, but they also go lower than the 3.X's.
I usually use @ 700 WPC (or more) top and bottom when I biamping my 3.x or 20.x.
The nominal 50/50 power distribution point is at 350Hz. If you put your crossover at that point, and you had symmetrical HP/LP electrical crossover slopes, you would need equal power amplifiers for top and bottom.
Cheers,
Dave.
Hi Davey,
Is 350Hz for the 3.X, 20.X or [20Hz to 20kHz] range ?
TIA
P.S.
Are you still running dual dipole subs ?
350Hz is approximate for the 20-20khz range. Some would argue it's lower than that. It might be, depending upon the type of music listened to.
Of course, you don't actually achieve the benefits of bi-amping unless the bandwidth is limited upstream of the power amps via a line-level crossover. This could allow the usage of lower-powered amplifiers and still yield the same effective power, or the same powered amplifiers but yield much increased effective power.
I've been using the dual-dipole woofer setup in my primary system for over fifteen years now. :)
Dave.
"... 350Hz is approximate for the 20-20khz range. Some would argue it's lower than that. It might be ..."I would assume if the speaker can not reproduce the lower octave(s), then the half-way point would change accordingly (i.e. move up).
"... I've been using the dual-dipole woofer setup in my primary system for over fifteen years now. :) ..."
I saw your old post and looked up the Adire DPL-12 (fs 16.3) drivers. Looks like they would make good subwoofers. Sorry to read the Adire driver company is no longer in business.
http://www.adireaudio.com/Files/OldAdireDrivers.pdf
Edits: 09/02/14
Even though the speakers might not be able to reproduce it, the amplifier is still trying to drive it, so that wouldn't shift a "half-way" point unless there was a low-frequency high-pass filter employed ahead of the bass amplifier.
The Adire DPL-12 drivers were ideally suited (Q-wise) to dipole usage with only 6db/octave dipole correction required. However, there are still plenty of drivers that will work effectively. It's mainly about quiet operation and large excursion capability. The necessary equalization can be handled by a variety of electronic solutions.
Dave.
I would say they are wrong if you listen to large scale classical and rock, which have a heavier bass proportion. Furthermore, bass requires serious damping which the upper range is not likely to need.
That said, 700 WPC top and bottom is likely sufficient for the bass unless you have a large room and overkill for the top.
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