There have been quite a few discussions on how the cone serves as a not so good waveguide in a coax.
But I am interested to know if small coax, (say a good one like KEF Uni Q) if crossed over quite high (above 500 Hz) to a woofer, will make the cone behave almost like a normal waveguide (below threshold of audibility) ?
Seas also has new mid only Coax drivers MR18, C18 (very costly) ...
Though, maybe, coax are not worth the hassle if listening is in midfield or farfield or unless wider vertical directivity is desired. (Coax based will also be a 3-way as compared to waveguide based)
But it will be interesting to compare the two designs in nearfield application ....
[In general , though, it will be nice to listen and compare Genelec 8260 and Dr Geddes Summa/NS15 in the same room
]
But I am interested to know if small coax, (say a good one like KEF Uni Q) if crossed over quite high (above 500 Hz) to a woofer, will make the cone behave almost like a normal waveguide (below threshold of audibility) ?
Seas also has new mid only Coax drivers MR18, C18 (very costly) ...
Though, maybe, coax are not worth the hassle if listening is in midfield or farfield or unless wider vertical directivity is desired. (Coax based will also be a 3-way as compared to waveguide based)
But it will be interesting to compare the two designs in nearfield application ....
[In general , though, it will be nice to listen and compare Genelec 8260 and Dr Geddes Summa/NS15 in the same room
]Namaskar
Have you seen this website?
http://medleysmusings.com/kef-q100-drive-unit-testing/
It seems like KEF really did their homework. The woofer produces some fluctuation around 7k to be sure, but it's no dealbreaker given the benefits of the coax design, and might be close to inaudible as it is. I never considered before that using the woofer in a 3-way would alleviate much of that effect but I've no doubt your hunch is correct: the less the woofer moves, the less effect it will have on the tweeter. I'd love to get my hands on a pair of these drivers.
Have you seen this website?
http://medleysmusings.com/kef-q100-drive-unit-testing/
It seems like KEF really did their homework. The woofer produces some fluctuation around 7k to be sure, but it's no dealbreaker given the benefits of the coax design, and might be close to inaudible as it is. I never considered before that using the woofer in a 3-way would alleviate much of that effect but I've no doubt your hunch is correct: the less the woofer moves, the less effect it will have on the tweeter. I'd love to get my hands on a pair of these drivers.
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Namaskar
Namaskar to you as well
I had seen that page, though was not sure how the final FR will turn up in 3-way and if it will be smooth enough like in case of some of the separate drivers..
Coax FRs are never nice to look at
Only way to get those uni Qs is to buy a Q100 (say used) and use the drivers ..... Would be nice to use it with a 8" woofer like RS225 in a 3-way.
Check this out a short lived ,due to KEF legal, commercial offering posted in another thread
Serious Audio: Listening Impression with Cursory Measurements: Soundfield Audio Monitor 1 Standmount Loudspeaker
Serious Audio: Listening Impression with Cursory Measurements: Soundfield Audio Monitor 1 Standmount Loudspeaker
Its more stringent than that! They expect the existing drivers to be returned
[atleast here in India]wont get q100 cheaper than this!!
KEF Q100 IN EUROPEAN WALNUT MAIN / STEREO SPEAKERS PRESTINE CONDITION 0637203207327 | eBay
KEF Q100 IN EUROPEAN WALNUT MAIN / STEREO SPEAKERS PRESTINE CONDITION 0637203207327 | eBay
There have been quite a few discussions on how the cone serves as a not so good waveguide in a coax.............
[In general , though, it will be nice to listen and compare Genelec 8260 and Dr Geddes Summa/NS15 in the same room
Regarding coaxial midrange/tweeter combo - 5th element did something similar to Genelec 8620 with his loudspeakers. He uses B&W FST midrange with phase plug out and tweeter mounted instead of it.
Measurements for Genelec looks awesome. I do believe that it sounds great being that it is a three way loudspeaker.
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I had quite a few conversations with 5th Element over PMs for my first build for nearfield and he is of the opinion that (technically) coax with woofer should be the best option ...
Btw 3rd party 8260 measurements : http://resolution.nodecube.net/products/pdfs/Monitoring/Genelec 8260A.pdf
Btw 3rd party 8260 measurements : http://resolution.nodecube.net/products/pdfs/Monitoring/Genelec 8260A.pdf
The KEF Q-something that I measured and posted on my site in PolarMap work very well. The best of the speakers that I have measured recently. They were fairly old however, but all three that I measured worked the same and quite well.
Someone posted what happens to the tweeter response when the cone is move forward and backward - it was quite substantial. this is a serious concern as this kind of modulation might be quite audible.
The DI of the KEFs was not as high as I would like to see in my mains, but they would be superb surround speakers where early reflections are not such an issue (we don't expect good imaging from the surrounds.)
The idea of coax is appealing, but there are some serious issue with implementation. The coax compression drivers that I have tested have waveguide that are too small and don't work very well. I think that I posted results of one of those some time ago. A direct radiating tweeter works better, but these small tweeters have serious power and thermal limitations that would prevent these type of source from being a good speaker in a high output situation, not to mention the modulation of the highs by the lows.
If I were to use the KEFs as mains, I would certainly HP them with a first order filter to limit the cone motion, and then use multiple subs (of course). This would be a very effective system except at fairly high output levels (like one would incur in a Home Theater.)
Someone posted what happens to the tweeter response when the cone is move forward and backward - it was quite substantial. this is a serious concern as this kind of modulation might be quite audible.
The DI of the KEFs was not as high as I would like to see in my mains, but they would be superb surround speakers where early reflections are not such an issue (we don't expect good imaging from the surrounds.)
The idea of coax is appealing, but there are some serious issue with implementation. The coax compression drivers that I have tested have waveguide that are too small and don't work very well. I think that I posted results of one of those some time ago. A direct radiating tweeter works better, but these small tweeters have serious power and thermal limitations that would prevent these type of source from being a good speaker in a high output situation, not to mention the modulation of the highs by the lows.
If I were to use the KEFs as mains, I would certainly HP them with a first order filter to limit the cone motion, and then use multiple subs (of course). This would be a very effective system except at fairly high output levels (like one would incur in a Home Theater.)
Did you mean using KEFs as the only driver ?
I was actually thinking of using it along with a 8" woofer in a 3-way speaker (and then adding subs below 80 Hz) And that too maybe with above 500 Hz crossover.
Also wonder if an even small coax say 3-4" with 0.75" tweeter , used above 800 Hz, be a even better idea ...
Btw let me check out the KEF's measurements in you polar map app.
Yes, one of the major problems when designing concentric drivers is not Doppler distortion from the cone moving, but as earl said, from the change in response of the tweeter due to the displacement of the cone. It changes the transition of the wavefront as it enters the cone and can at extreme positions make response differences in the order of 3dB.
The real answer is to restrict movement by high pass filtering and adding a bass driver, so turning it into a three way system.
I am not sure I would use just a 1st order filter. From my experience in observing my concentric designs, there would still be too much cone displacement. I prefer to use at least a second order filter around 250hz.
The other problem with concentrics is the edge termination, as the cone/surround transitions to the baffle. This causes response errors particularly on axis, and get worse the larger the surround. Another reason for restricting the low frequency response so that I can use a small profile narrow surround. I did once experiment with a flat profile surround while at KEF, and this worked well, except that it had a response dip due to the surround anti-resonance.
KEF seem to have a good handle these days on getting a smooth response from their two way drivers (LS50 for example) with good surround design and good transition into the cone, but that does not solve the issue of large cone displacement.
Andrew
Those magnesium / ceramic CST units you worked on are really damn nice too. It's almost a shame that you had to limit them with those thin profile / low efficiency woofers in the S-EX but I'll presume you had fun with the constraints.
As I asked earlier, what if its used as a mid-tweet above 500 Hz or even higher (or maybe an even smaller coax )
Btw I did see KEF Q15 (which looks like older version) on polar map. quite nice, though not as good if I were to compare with Behringer 2031.
Which gets me back to my question in OP. How do the two designs fare in nearfield, except maybe the vertical dispersion ? Because otherwise the 2-way is relatively simpler right from driver procurement to crossover...
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