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Old 28th March 2006, 01:37 PM   #11
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Default It is thought to be an experiment

I think I was not clear enough that the sole purpose of crossing over two *identical* (same model) FR drivers is to experiment in what degree a crossover is detrimental to percieved sound quality. A real setup would naturally use deivers appropriate for each of their frequency ranges. The point was to have an apples to apples comparison. The 1-2kHz piont was suggested because that is where we should be able to percive de negative effects most easily.

The *real* system I am thinking of is a 2 or 3 way with a compression driver in a controlled directivity waveguide above 1-1.5kHz or a 3 way with a fullrange from 300 to 6-12kHz dipole augmented below and horn augmented above.
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Old 28th March 2006, 10:04 PM   #12
KCHANG is offline KCHANG  United States
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Default I've tried both ...

Quote:
The *real* system I am thinking of is a 2 or 3 way with a compression driver in a controlled directivity waveguide above 1-1.5kHz or a 3 way with a fullrange from 300 to 6-12kHz dipole augmented below and horn augmented above.
I've a pair of JBLCS3115 speakers, each of which has a 15" woofer in BR arrangement, an 8" mid driver with a front horn covering about 350-1600Hz, and a horn-loaded compression driver for tweeter. I've also built various OB speakers using fullrange/widerange drivers. Some of the OB systems use woofers in big BR boxes, and some use dipolar woofers on the same baffles with the fullrange/widerange drivers, and some of them simply use a subwoofer for bass. For instance, I currently have OB speakers in my home theater system as front speakers. Each of them uses a BR box with two 15" woofers, an Audax PR170MO on OB for 300Hz to perhahps 7KHz (no lowpass), and a cheap Fostex horn tweeter.

The JBL speakers sound quite nice, but somehow I am more attracted to the sound of OB systems. To my ears, the Audax-based OB system rivals the JBL speakers in sound quality and perhaps surpass them in terms listening enjoyment. My experience is of course only one data point, and is not conclusive because I likely have not have extracted the best performance out of either system. Nevertheless, I just want to say that I think a 3-way system using a fullranger in a dipolar configuraiton can be quite good.

Cheers,

Kurt
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Old 28th March 2006, 11:10 PM   #13
AJinFLA is offline AJinFLA  United States
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Quote:
I think I was not clear enough that the sole purpose of crossing over two *identical* (same model) FR drivers is to experiment in what degree a crossover is detrimental to percieved sound quality. A real setup would naturally use deivers appropriate for each of their frequency ranges. The point was to have an apples to apples comparison. The 1-2kHz piont was suggested because that is where we should be able to percive de negative effects most easily.
Unfortunately, two identical drivers (fullrange or not), crossed at 1k, would have a completely different polar response than a single driver. So it wouldn't be an apples to apples comparison. Actually, someone has already done exactly what you described, using 2 small midbass units. I can't remember all the details, or I'd give you a link.
Maybe if you lowered the xo to 200hz or so, but even then still would be an imperfect comparison.
If you were interested in the audibility of crossover phase distortion, there are tests, like what I thought maybe choky had taken, such as SL's: http://www.linkwitzlab.com/x-phs-dist.htm
A little info you might also be interested in: http://www.linkwitzlab.com/frontiers.htm#F

cheers,

AJ
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Old 29th March 2006, 02:22 AM   #14
m@ is offline m@  Thailand
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AJ,

Polar response would be different, but isn't that part of the point? Crossovers do awful things to polar patterns - even an LR4 is far from perfect in this regard (and in general it gets worse as you go down in order).

Linky himself addresses this (polar patterns) - not discussing his own designs, but discussing planars - and suggests off axis/reflected contribution must 'fill in the gaps' in the polar pattern. I think of it as a type of 'averaging' that goes on - and I can definitely tell the difference between my own dipole design and the full range design I put together. Someone on one of these sites suggested that when we move away from a single point source (to a multi-way) design the 'brain has to work harder.' I agree with this one hundred percent. We divide a signal electrically - through a very inexact process - then expect it to sum acoustically? No. I think we're making the ear/brain do most of the work.

I'm not a die hard full range person, but I do think there are significant benefits to keeping the mid band (lower/mid hundreds to 5 or 6 k) free of crossovers. The ear is significantly less sensitive outside of this midband.
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Old 29th March 2006, 03:28 AM   #15
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Pick your poison. Single driver systems suffer from either a lack of and/or compromised bass or treble. Crossed systems have crossover probs (to some) but have the potential to have both resolved and balanced bass and treble.

Try using two identical "full range" drivers, say two 4", but instead of crossing @1200Hz, just low pass one of the drivers and let the other run full range. Then compare to a single 8" or a 4" to see which sounds better.
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Old 29th March 2006, 05:25 AM   #16
m@ is offline m@  Thailand
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hi ultrakaz,

but then aren't you just hearing the driver with its high end rolled off? crossovers enable driver integration as well as bandwidth limiting. and i think integration is where they have most or all of the problems. maybe i misunderstand what you're suggesting.

i agree that full range drivers are usually too much of a compromise by themselves (i hate 'polite bass' - i want to feel bass as well as hear it, even if that means some loss of accuracy). but if you augment the top and/or bottom octaves - you can design them to put crossover(s) out of the most critical band. with some care, you can even leave the crossover off the mid/wide range driver, where it seems to matter the most.

it's just like the different ways to cabinet load - BR works pretty well (despite being a resonant system) for the bottom two octaves or so, but I wouldn't want to do it somewhere in the upper mids - the ear is decidedly more forgiving outside of the critical (voice) band.

i don't want to be an evangelist - but in my own experience, the difference between a traditional two or three way and using a wide range in the middle band - the difference is not subtle. I love the spaciousness of a three way dipole system - and love a lot of traditional 3 ways in general - but a wide range driver system is absolutely the most involving of anything i've listened to. YMMV
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Old 29th March 2006, 02:00 PM   #17
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Quote:
Polar response would be different, but isn't that part of the point?
Yes, that is a very important part of the point, since crossovers with one single fullrange are net very common
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Old 29th March 2006, 08:15 PM   #18
AJinFLA is offline AJinFLA  United States
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Swak, I was simply pointing out why your comparison using 2 fullranges would be flawed. I think both you and m@ are mixing up the issues. The polar response is different (worse) not because of the crossover, but because the two (fullrange) drivers are non coincident. They can't be.
If you believe crossovers cause poor polar response, then you have never seen the polar response of a good coaxial, or better yet coincident driver, where there is greater alignment in the z-axis. They certainly use crossovers, don't they?
The polar responses will look very much like a fullrange, except most likely (much) better in the treble region.

cheers,

AJ
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Old 29th March 2006, 09:28 PM   #19
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Default AJinFLA, you make a point.

Yes, that is right, the worse polar response problems are not due to the crossover, but to the driver separation. I have heard mixed things about coaxials and have not heard any. Some peaplo that know their stuff say (look over at AA) they introduce worse problems than the ones they solve.
I should have specified I was more interested in a comparison between 1 driver, no crossover (over a range) against two non coaxial/coincidental with XO.
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Old 29th March 2006, 10:01 PM   #20
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Default Kurt (KCHANG)

I had overlooked your post. That is very interesting. May I ask if you measured the directivity of the audax @ 7k? That was one on my list, too bad the paper cone version is no longer available. Magnetars setup with 2 of these has olways catched my attention. There are similar drivers anyway (b&c and phl for example, ther was someone who compared the audax to a Pr65-neo, and found the latter better http://db.audioasylum.com/cgi/t.mpl?f=hug&m=101904). The visation B200 up to 12k is another candidate, although I have no idea about their dispertion pattern that way up. One advantage of this setup is certainly the simplicity of the system.

Did you prefered the BR over the OB subs?

PS: I read you were willing to audition the Summas, did you listen to them?
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