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In Reply to: RE: Boxed Bass posted by emailtim on May 23, 2021 at 08:24:02
use pairs of drivers facing opposite directions driven out of phase.
That doesn't seem to be the case with Jazzman's design.
Follow Ups:
Alternating the drivers in the H-Frames (as sometimes pictured in the GR-Research subs) distributes the magnet weight within the H-Frame cabinet provided even number of drivers are used. He has many triples out there.It supposedly averages out non-linearity of the driver's back-2-forward and forward-2-back movements (assuming even number of drivers), but I have not able to measure or hear any discernible differences between the 2 mounting options. The force on the cabinet is still the same (both fire towards the front at the same time and fire at the back at the same time), but the weight distribution is different.
The Linkwitz Phoenix cabinet design both centers the weight in the cabinet, averages out the non-linearity driver movement and also throws in force cancellation making the cabinet as still as a tombstone (provided it is sufficiently strong for the task). It does exhibit different front and back waves due to asymmetrical chase openings which can interact with the room differently than the H-Frame design. I have tried the Phoenix in a 2-driver configuration, but not a 4-driver configuration which has the same number/size of front and back chases.
The W frame is somewhere inbetween the 2.
Edits: 05/23/21
What high/low pass settings are employed with your 20.1s?
The OEM user's manual indicates the passive XO is the following:
Low-pass (bass): 18dB Butterworth @108Hz
High-pass (midrange/tweeter): 6dB @330Hz
http://www.magnepan.com/pdfs/manual/MG_20.1.pdf
The stock XO has always left a hole in my room.
I use a steep slope symmetric linear phase 250Hz XO which doesn't leave the hole.
"Stereo DIY GR Research OB/Dipole Subs"
Thanks.
I have run them as high as 250Hz with steep symmetric XO's to see what they could do, but needed to use my own XO and amps to do it.The plate amp had its own undefeatable DSP and XO which got in the way of what I was trying to do. Their XLR plate amp version supposedly has a defeatable XO, but the DSP can't be bypassed.
I am currently running them at 100Hz which gives some visceral bass reinforcements. I have a Stockfische test disc that has an outdoors fireworks track which hasn't sounded better.
If you cross them over too low, you lose the impact of the drums. That choice is also in part decided by room nodes based on the sub and bass panel's placements. I measured the subs and bass panels individually, looked at their respective room modes and chose the XO point that would minimize the holes.
Edits: 05/23/21
I am currently running them at 100Hz which gives some visceral bass reinforcements. I have a Stockfische test disc that has an outdoors fireworks track which hasn't sounded better.
Similarly, I let the room determine the most linear results between the 1+1s and dual subs in the HT.
Empirically, it turned out to be high pass to mains at 90 hz to fill a trough with low pass to subs at 60 hz.
I run my 2+2 down to 60hz and the 4-15" open baffles handle the rest :)
There are a number of speakers that use a single driver. It all depends upon how much output capability is required.
In Jazzman's case, the single driver would seem to be adequate based on the limited SPL ability the main speaker has. It is a symmetrical configuration, apart from the driver itself.
Other than the phase distortion of the crossover, there is nothing less coherent about this approach than a large, full-range panel.
Large, full-range panels are not inherently coherent either since there is phase distortion associated with differing path distances, in the near-field.
There isn't any speaker that's truly coherent (using the strict acoustic definition.) They would have to be much smaller.....and thus not able to produce adequate bass.
Headphones are your best bet if you're really into "coherency." :)
Dave.
I may be mistaken, but I believe the Quad 63---owing to it's progressive circles of ESL driver segments---is able to produce very coherent sound. But coherency isn't everything; some still prefer the original Quad ESL to the 63.
Other than the phase distortion of the crossover...
along with a couple other factors. ;)
My choices are driven by what I hear - as opposed to what I read. YMMV.
"Coherence" being a subjective thing for you. I understand.
As I've said many times, I'm not (and neither is anyone else) equipped to argue with somebody's subjective evaluation.
However, the physics are undeniable.
Dave.
Neither speculation nor the use of circular reasoning is used in my evaluation process.
Good day!
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