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In Reply to: RE: Marchand XM44 in hibernation ... posted by watts on January 23, 2017 at 18:55:36:
The suggest biamp XO in the manual is obviously a typo. The 3.5 model gives 3rd order 200hz LP and 2nd at 200hz HP or 1st order at 250hz HP. I think they just swapped the freq. for high and low pass when the 3.6 manual was written.
Spacing the crossover using a 6db HP for the mids is pretty much the "standard" maggie approach.
From the 20.1 manual (corrected for obvious typo)
"Set the high pass section at 200-300 Hz, 6dB per octave. Due to standing
waves at the crossover frequency, the low pass section may require adjustment
from as low as 90Hz (12dB Bessel) to 150Hz (18 dB Butterworth). Typical
settings are in the middle of this range. Optimization of the low pass can be done
by ear (with music) or spectrum analysis"
For the T IVa they suggest LP Butterworth 3 at 250hz
HP 12db at 400 hz.
They also suggest that symmetrical 12 or 3rd order XOs at 250-400 hz would work well.
I have tried many combos on my T IV/Neo8 for both triamp and biamp. The main deal is to get good time alignment. Aside from the XM 44 that I used with Marchand's suggested LR4 modules I also used an Ashly XR 77/18 3rd order and later a Rane LR4 to experiment further as well as various 1st order and 2nd order symmetrical and asymmetrical crossovers.
The LR4 symmetrical did quite well but you could tell that the bass was crude as you passed from playing the violin in the upper strings to its low string. And Cellos changed character going from one end of the range to the other. B3 was better in that regard, but 1st order was magic. With the drivers time aligned in an arc, imaging was perfect.
I then went on to switch the setup to the short wall and try my hand at wall loading. After much frustration trying the 1st order again just without managing an equidistant setup with the bass panels face forwards to max out wall loading, I swapped to the classic maggie 3rd LP and 1st order HP, just that I lowered the HP to below the midrange driver's acoustic rolloff and let the Neo8 do as much as they can and filled in
with the bass at B3. If you go up with the LP to the -3db acoustic HP point of the mids at about 250-275hz and fix time alignment then you have a full if not slightly ripe tonal balance but lose clarity as the bass panels are audibly losing detail and take over output in the 200-250hz range. Lowering the LP down to below 200hz lightens the tonal balance and makes it a bit lean to the benefit of clarity and imaging. Time alignment is adjusted to compensate for group delay differences between the LP freq) In that circumstance it is a bit better to raise the bass level somewhat to compensate for the leaner subjective balance, particularly if you take the LP down to 150-160hz.
Biamping with LR4 loses you phase info at the mids and damages imaging and tonal texture. It may not be that bad with the 3.x models but with 3 of them I cooperated on the 6db HP was pretty much necessary to make the most of the midrange, anything else squished the soundstage and made the images lose palpability. The main thing is to carefully tune the B3 LP to match with the 6 db HP. It wasn't very practical to do that with the Marchand but once I had things dialed in I redid the boards and it was fabulous, just that it is more so with only a cap rather than the whole Marchand gain structure. So I ended up selling it.
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- RE: Marchand XM44 in hibernation ... - Satie 00:20:45 01/24/17 (0)
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