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GM's 31 Jordan JX92S MLTL finally built
GM's 31 Jordan JX92S MLTL finally built
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Old 9th February 2011, 05:09 PM   #1
Colin is offline Colin  United Kingdom
diyAudio Member
Join Date: Aug 2003
Location: UK
Default GM's 31 Jordan JX92S MLTL finally built

It’s been a while but I finally got round to finishing my build of GM’s 31” Jordan JX92S MLTL.

The build was straightforward. I used 18mm MDF with dowel bracing. The reflex tube exits via the floor of the enclosure and I extended the sides to form a stand. It doesn't incorporate the reflector plate on the original plans.

I currently have access to a pair of two-way active speakers which have a good reputation for accuracy. Compared to these, the MLTLs sounded too hard. I fitted the same BSC that Jim Griffin recommends (a 6dB cut, I believe) and the MLTLs immediately sounded a lot better, much closer to the actives. Given I'm using a low power (30w) Tripath amp on them and have no idea what that sounds like in isolation, the MLTLs do very well and I could happily use them as my main speakers. Minor tonal differences aside, they lose out in headroom but gain in imaging.

With BSC, the bass is now a touch too strong but I haven't done any fine-tuning on the stuffing or tried reducing the resistor value in the BSC.

Compared to my 48" MLTLs, the 31s sound colder in the bass (if that makes sense). I can see why people might prefer the 48s but now I have the actives as a reference, the 31s are undoubtably more accurate, as predicted by GM. Using test tones, the 31s generate 40Hz very clearly in my room.

So all in all, a superb design. They use hardly any floor space and look very neat. Visitors are intrigued when they only see one little circle on the front generating all that bass.

Thanks to GM for putting in the work on the design and making it available (and to Martin King, of course, for the modelling software).

This probably marks the end of my single driver adventures. I love the simplicity but the actives have got me intrigued. The next step I want to try is an active 2-way, combining a JXR6 with a JX125. I had a similar passive system. When I sold it and the buyer used it in his system, I realising it was held back by the Naim amp driving it and I'd never heard it at its best (I may have said "Bah" or similar).

Last edited by Colin; 9th February 2011 at 05:15 PM.
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Old 9th February 2011, 07:30 PM   #2
rjbond3rd is offline rjbond3rd
diyAudio Member
Join Date: Jan 2007
Congrats, Colin. That build is on my radar. It is amazing how much bass can come out of the JX92S. I felt that a 2A3 was a nice combo to warm things up a little (underpowered, of course, but not as much as I had expected).

What's the appeal of active vs. passive in this case? Are you trying to get steeper crossovers, EQ or...?
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Old 9th February 2011, 08:53 PM   #3
Colin is offline Colin  United Kingdom
diyAudio Member
Join Date: Aug 2003
Location: UK
Thanks for the comment.

I feel going active is a technically more elegant approach and would enable me to hear the JXR6/JX125 combination at its best. The actives I've been using have made me realise the importance of decent headroom (they're 300+ watts per cabinet).

The JXR6 is smoother at HF than the JX92S, so that's a possible combination for a smaller speaker. Jim's recommended Aurum Cantus ribbons are expensive to buy from the UK. As I already have the JXR6s & some Gainclone bits, it would be as cheap to go active.

Enjoy reading your website, btw.

Last edited by Colin; 9th February 2011 at 08:57 PM.
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