|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
In Reply to: A couple of questions.... posted by Adnan on September 23, 2001 at 18:45:25:
Umm...why exactly do you want to replace the cabinet of the KEF Q15.2? I ask, because I am sure that you must have considered that the driver(s) in question are optimized for the box that they are in and yet, you seem to feel that you can gain something by placing the drivers in a different cabinet.A small box like that of the Q15.2 will not have big problems with diffraction effects. The small surface area of the box is actually ideal for avoiding these types of problems. The Q15.2s already image very strongly by controlling treble dispersion, essentially by mounting the tweeter in a shallow-horn, which acts as a wave-guide and which also matches the tweeters dispersion pattern to that of the woofer at the crossover point. This is why the crossover between the drivers is so seamless in a dual-concentric design.
My advice: leave the drivers in the cabinet. That design offers very little room for improvement.
Follow Ups:
Hi,The Q15.2, as a ported design, attempts to strike a balance, as so many bookshelf speakers seem to try to do, between small size and low-frequency response. On this model, there are slight colorations in male vocals that can be easily picked out.
KEF's center channel speaker, the Q95c.2 uses the same driver in a closed box of half the volume as the Q15.2. The result is that the Q95c.s does not go as low as the Q15.2 but vocals and imaging are even better, in fact, the coloration practically disappears.
I called KEF and they admitted that the Q15.2 has that problem and also agreed that the sealed box is superior. The sealed box offers a -3db point at ~80 Hz, which is perfect in an HT application with a subwoofer.
I would use the Q95.c all around except for two issues - the cabinet shape is unappealing for anything but TV-top use and KEF, in their infinite wisdom, have chosen to price it the same as a pair of the Q15.2s.
I'd like to make custom cabinets that blend in well with my room and having made cabinets before, the mechanical aspects don't worry me. Are you suggesting that I keep the front baffle dimensions the same and just make the cabinet half the depth?
I wouldn't attempt it unless I was fairly sure that I'll see an improvement. The concentric design with its superb imaging and dispersion is what attracted me in the first place.
Regards,
Adnan
I'd be curious to know what you think the source of the coloration is. If it is spurious resonance from the port, you should definitely consider plugging up the port, before replacing the entire cabinet. Do you believe the volume of the cabinet to be too large for the driver in question? Unlikely, but if you feel this to be a problem, you can partially fill the cabinet (perhaps with sand) until you acheive the desired volume.Replacing the cabinet seems like an interesting experiment, but in this case I think that you will end up with a no improvement or perhaps even worse colorations.
Hi,The cabinet volume is probably fine for a reflex design. If I were to simply stuff the port, the cabinet will be too large for a sealed design.
I'm not sure exactly where the colorations are coming from. It is most likely the port but there may also be improvements possible by adding bracing and using Black Hole 5.
The good thinag about this project is that if the new cabinet fails to offer an improvement, I can always reinstall the drivers in the original cabinet and call it quits.
Regards,
Adnan
In addition to a port resonance, you might also be dealing with a coloration (null?) produced by the interaction of the driver and it's mid-range backwave (perhaps the cabinet needs more internal damping) or perhaps it is a boundary effect caused by the speaker's proximity to nearby boundaries. I agree with your final point. No harm in trying. Would be curious to know if the experiment is a success.
This post is made possible by the generous support of people like you and our sponsors: