Jxr6 Hd - Crossover - diyAudio
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Old 31st March 2006, 04:45 PM   #1
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Default Jxr6 Hd - Crossover

Hello everybody,

I was following the discussions on the new Jordan very closely. However, there are still some questions I would like to ask.

Some prefer to cross over at 300Hz. Others recommend to go down to 100Hz.
According to the surface of the membrane (24sqcm) the movement of the membrane increases drastically below 300Hz. This is not only an issue of power handling. I would believe that it also effects distortions badly. Anyway, with a 6dB x-over power handling below 300Hz would be still needed. I am looking forward to using a passive filter. Maybe the low x-over is only reasonable with an active filter?


My next uncertainty is if I should use a 6dB or a 12 dB x-over?
The 6dB is well known for SPL problems at the crossing frequency. The 12dB has the disadvantage of non-linear phase; ...if this is a disadvantage. Some people say that 6dB x-over are prefered by audiophiles, but it has never been proved to sound better.
What would you prefer???

Has anybody experience with impedance compensation of the JXR6? With such a low x-over it would need to be compensated? - or not?

Many thanks for your answers!

Michael
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Old 31st March 2006, 07:04 PM   #2
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I would go about it by getting a handful of Solen capacitors that will give you the various crossover points and go from there. Personally, I think you're on to something if you say the cone activity increases drastically below 300 hz. I'd start there and work your way down, (or vise versa). It may not make a huge difference if you don't listen too loudly. Chances are, the higher the crossover, the better the Jordan will sound if you're correct about the 300 hz bit. I'd start with first order myself, as it's easy. You can always change that later if you leave the crossover external or easily accessible.

However, looking at 300 hz means you need a good woofer, as this enters the lower voice region for some folks. No longer will a cheap sub driver do, (my opinion).

As for crossover types, different strokes for different folks. Some like an immediate cut off, like a fourth order, and some like a smoother blend, like a first order. Then there are the Butterworth, Linkwitz, etc. I don't understand the differences they each offer. But to get the most out of single drivers, simpler seems the better route.
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Old 31st March 2006, 08:42 PM   #3
Dumbass is offline Dumbass  British Antarctic Territory
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For the JX53, Ted Jordan recommended a (passive) first-order crossover between 200 and 500 Hz to one of the bass units (JX125 or JX150). Even though the JXR6 goes slightly lower, I think that's probably a good place to start. You'd have to find a bass driver that is roughly equivalent; ideally something with similar efficiency, impedance, Qts. I think there are some 6.5" and 8" Hi-Vi bass drivers that might fit the bill.

Google "rune phase linear" for a cool project. Even though he used active filters, I think a lot of the ideas would translate to passive. He put the JX53 in a separate enclosure, so he could physically fine-tune time alignment. And the TL enclosure for the bass unit is very cool.

On the Linkwitz site, he has a little spreadsheet to estimate max SPL capabilities, based on driver radiating area and Xmax. It might give you some intuition about where you'd want to set the xover point. (Remember you'll get a 6dB lift at xover freq from the bass driver.)
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Old 31st March 2006, 08:59 PM   #4
Tenson is offline Tenson  United Kingdom
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I am doing a project with a Tangband 871 crossing to a cheap Dayton woofer passively. The Tangband is not a lot different to the JX6.

I plan to cross around 400Hz, as max SPL and distortion is an important factor for me. 600Hz-700Hz would be better in terms of low distortion and high SPL but the driver I have doesn’t sound too good that high up.

I can let you know how I get on if you want to wait a week or two? I am currently running in the drivers for a few days before making measurements.

I mean really the JX6 and Tangband stuff are best thought of as just midrange drivers with extended high frequency IMO.
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Old 31st March 2006, 10:14 PM   #5
Dumbass is offline Dumbass  British Antarctic Territory
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Quote:
Originally posted by Tenson
I mean really the JX6 and Tangband stuff are best thought of as just midrange drivers with extended high frequency IMO.
AFAIK the Jordan 2" drivers were never envisioned as full-range drivers:

Ted's present Company originated in 1975 with the launch of the JORDAN 50mm MODULE, the original ancestor of the current JX53. This was a 2" metal foil coned unit which covered the entire frequency range above 150Hz and required only a first order crossover to be used with readily available bass units.

http://www.ejjordan.co.uk/jordan.html
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Old 1st April 2006, 02:27 AM   #6
soongsc is offline soongsc  Taiwan
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I have crossed over at 450Hz with good results. Initially I would avoid impedance compensation. If the sound is a little harsh after finishing the XO, I would look into compensating after the XO is completed and impedance measured, that is the load the amp sees. Then figure out how to compensate from there.

If you are picky about imaging and music details, then first order or whatever transient perfect XO would be best. If you find the harmonics characteristic of speakers more satisfying, the you can use higer order XOs.

I think this Jxr6 should be in the Loudspeakers category though.
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Old 1st April 2006, 09:21 AM   #7
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Thank you very much for all your useful answers!

I am going to use a scan-speak 15W/8530K00 as woofer which could be used up to 8000Hz. For sure not the cheapest choice, but the parameters suit for the existing enclosure and the low end is quite surprising. AND in my application I could even run it "closed" - just in case of future dipol-sub-operation

Regarding the x-over i will go for a 6dB! I had used he JX53 before in an application with 1st order and was not unhappy at all.
Dickason describes 10dB drops of 1st order cuircits.... but at the crossing frequency of 300Hz (e.g.) the wave length is around 1.4 meter (sorry... around 4,6 feet) so the "sweet spot" should be rather huge. And outside it is, in any case, more a question of room acoustics.

My "old" JX53 was crossed at 250Hz, which was definitely a bit too low. The attached graph shows the membrane activity. (differerent colours represent enclosure sizes 1, 2.6, 4 liters) That problem is the same for the JX6 as it is defined by the size of the membrane. However, the JX6 will be more able to handle frequencies below 300Hz as it has a x-x of 6mm. But for the distortion it will be the same as with the JX53.

Anyway, I understood from your explanations that it is more a matter of testing. Thats what I will do now!

Best wishes

Michael
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Old 4th April 2006, 04:43 PM   #8
Colin is offline Colin  United Kingdom
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To add an additional bit of information: the German distributor uses a JX53-Jordan woofer combination at 300Hz but I think it's a 12dB x/over. I've been using the JXR6s with only their enclosure rolloff, at around 120Hz BUT I don't listen loud and I'm still experimenting. If I was using them was a purpose-designed x/over to the bass, I'd feel safer at a minimum of 200Hz, which fits in with other experience here.

They have more body in the sub-300Hz region than the JX53s but could do with a little more, either via compensation or another JXR6 running in series.
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