JXR6 design analysis for near field setup

[kamppi]

Colin: I know that you have experiences for both JX92S and JXR6 drivers. I have JX92S in modified GM MLTL (30cm wide) and I am happy, but new JXR6 is available and I would like to try it together with Peerless 8" HDS PPB or Scan Speak 18W4531G00. Sensitivity for both of the drivers are 90dB.

How the midrange of JXR6 compares to JX92S? Vocals, piano... imaging ability? I am planning to use passive crossover around 200Hz. One option is that I won't put any passive components for Jordan.

[Colin]

Hi

The JX92 and JXR6 have a similar ability to pull out small details but they do sound a little different. The 6 is smoother, more delicate and more electrostatic-sounding, whereas the 92 comes across as slightly brasher, more exciting a listen. The 6 is very seductive, though, and definitely goes higher into the HF. The freedom from any sizzle or glare is really, really nice. I'm still using a pair on their own in the ceramic enclosures. Backed into corners or against walls the bass is surprisingly good, despite having no real weight to it.

Re imaging, in my current set up, the 92s win, with more depth. BUT, I haven't sorted edge reflections from the 6's cabinet yet and it is in a narrower cabinet to begin with, which might effect things.

The 6 with a Scanspeak or similar will, I suspect, be a more accurate speaker. Let us know how you get on.

[kamppi]

Thank you Colin for a good answer. I trust your opinion and I will walk to the retailer and buy a pair of JXR6 speakers

I am still unsure which driver I should use for lower frequencies. SS 18W4531G00 is a strong candidate. 90 dB efficiency, small cabinet and SS sliced paper cones have a very good reputation. It is quite expensive, but maybe good value for the money. Peerless costs less than half of the SS price...

[Colin]

Go for the driver which suits the bass extension and cabinet size you want - the JXR6 is covering the important range. I'll be interested to hear what you come up with.

One thing to watch is that the JXR6 is a 4 ohm driver, so you have to be careful matching the bass output. Although on paper the JX92 would seem a good match, I've found the JXR6 is actually more sensitive and needs a bit of fiddling to bring it down to the 92's level. Going active would sort it but I thought fullrange was supposed to simplify things.

I had a go at matching the JXR6 to a redundant Scanspeak TL I had sitting around. Not a bad match for speed etc but I didn't get the levels right. The TL only went to 50Hz and rolled in at just over 100Hz so half the time I couldn't even tell it was there.

The Jordan cones are very light and sensitive to back reflections, so a non-reflective shape cabinet would be a good idea. And they don't come with any form of protection, so as soon as you get them, make a cardboard or plastic mask you can tape over the chassis whilst you're fitting them to the cabinets. One screw falling on the cone will dent it.

Good luck with the JXR6 project and I look forward to seeing how it turns out.

[kamppi]

Today I tried to buy JXR6, but seems to be that these drivers are not available yet. There has been some problems with the production.

[deandob]

Finally I have set myself up with a decent measurement microphone, the RadioShack SPL meter is no good for speaker frequency response measurements.

I purchased the "mad about sound" mic & preamp kit which uses the panasonic WM61 electret, brass rod and a decent preamp. After loading up the MW61 generic calibration file into Room EQ wizard, I get a much flatter graph than those posted earlier in this thread. The graph has the subwoofer wired with inverse polarity (the 100 - 500Hz frequency range is flatter that way) as well as the speakers toed in about 20 degrees which provides a flatter treble response. If you have noticed that 100Hz and below looks boosted - its because I like it sounding that way!

To perfect this setup I will add electronic equalisation for the dip at 300Hz and the peak at 2Khz, as well as room impulse response correction and this project should be done. Fiddling around with the equaliser based on the results from Room EQ wizard using a digital convolver removes some of the mid range forwardness and does make it sound more neutral.

Regarding the back reflections, I used a couple of blocks of wood angled at 45 degrees to break up the back wave as well as stuffing to remove the reflections. I suspect its still not perfect as its possible the 2Khz peak is a function of the box and that the stuffing may be robbing the driver of some dynamics.

Regards,
Dean

[Colin]

I believe the JXR6 is about to go into its second production run and there are one or two modifications being made prior to ramping up to a larger run.

[soongsc]

Originally posted by Colin
I believe the JXR6 is about to go into its second production run and there are one or two modifications being made prior to ramping up to a larger run.

Very interesting! What is being improved if this quality driver?

[Colin]

I'm not sure, I think Ted's just improving the specs slightly now he's had a chance to play with the first production units.

[kamppi]

I talked to the importer in Finland and they said that the JXR6 units which they have received are quite promising.