Jordan JX92S power handling - diyAudio
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Old 7th February 2007, 12:58 PM   #1
cs is offline cs  United Kingdom
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Default Jordan JX92S power handling

I've been looking at doing a full-range MLTL design using the Jordan JX92X, but am wondering whether it would be severely limited in terms of bass power handling.

The MJK worksheet shows that the cone displacement is about +/-2mm at 50Hz and 87dB/W/m, which is half the maximum permitted. So there is no way that a more realistic 100dB at 1m can be produced, without the driver hitting the endstops.

Anyone tried using the Jordan unit full range, and if so, is the bass output very limited as I suspect ?
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Old 7th February 2007, 01:02 PM   #2
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There will be some reinforcement depending on positioning and size of room. I find the JX92S in a sealed box goes pretty loud.

It all depends on your taste and room configuration. 90dB may not look much on paper but it's fairly loud.

To be honest hitting 100dB in the bass is going to take some doing. A vented 12 inch sub I built along time ago before monster Xmax drivers came along, would only just about manage that on a good day.
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Old 7th February 2007, 02:15 PM   #3
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You've got the wrong driver for monster bass SPLs. Or monster SPLs of any sort come to think of it. That's not what Jordans or any 4in driver is for. If you want to shift a lot of air, loudly, you're going to need either the Audio Nirvana 10in in an MLTL as a minimum, or an 8in driver, horn or TQWT loaded.

Quick word of warning: anything over 85db will cause hearing damage in the long term. I realise you probably know this, but I'd rather mention it than otherwise, if you know what I mean. The occasional blast is OK (I'm a bit of a rocker so I do indulge, but rarely at those sort of SPLs), so long as it's not too often.
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Old 7th February 2007, 03:04 PM   #4
cs is offline cs  United Kingdom
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My 100dB target is really only to enable peaks to be reproduced without distortion. Average levels would be much lower.
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Old 7th February 2007, 03:23 PM   #5
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With any driver of that size you're not going to see real anechoic 100dB bass. I say just build it and if you find it lacking add a sub.
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Old 7th February 2007, 03:24 PM   #6
MarkMcK is offline MarkMcK  United States
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Hi cs,

Some of your assumptions about specifications and what they mean are not quite correct.

For example, suspension max and xmax are not the same thing. The Jordan claims an xmax of 9 mm peak to peak or 4.5 mm in each direction. This is not how far the cone can move before hitting the stops. This number represents the movement before the amount of voice coil winding in the magnetic gap begins to change.

The suspension will allow the cone to move significantly beyond this point. When it does, particularly on sine waves, but less so on transients like music, the distortion will increase. How much distortion can you tolerate?

If you can tolerate three to five percent distortion for sine waves, then the limit at fs will be about the continuous power rating.

If you do not know what this value is, check:

http://www.ejjordan.co.uk/drivers/jx92.html

Do you understand this? If so, then please tell others when they ask the same question. This confusion of xmax and suspension max happens all too often.

Thanks,

Mark
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Old 7th February 2007, 03:45 PM   #7
cs is offline cs  United Kingdom
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Jordan don't state the absolute max suspension travel, but I have observed that for most drivers, it is around 2x the Xmax. So maybe I can assume the end stops are +/-9mm.

The MJK worksheet is predicting 87dB/W/m at 50Hz for +/-2mm, so my target 100W peaks will try to move the cone +/-20mm !

If I assume a more reasonable +/-5mm on peaks (to avoid the midrange being adversely affected), then this equates to 8dB more SPL, or 95dB. Maybe this is sufficient.
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Old 7th February 2007, 08:10 PM   #8
PJN is offline PJN  United States
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Default JX92S volume

I have the JX92S in backhorns and they can easily exceed 90 dB. How much louder they can go I don't know I needed ear plugs when I was measuring them at 90 dB. I normally listen at ~ 80 dB so they get more than loud enough for me. This is in a 24" X 19' room. They are great drivers BTW.

PJN
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Old 7th February 2007, 08:26 PM   #9
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Hi!
Listened to the VTL last week and I must say they sound really good! It was in a room filled from floor to ceiling with speakers. Not the best listening place, yet....
Plenty of sound at least for me.

Cheers
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Old 7th February 2007, 08:48 PM   #10
MarkMcK is offline MarkMcK  United States
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Hi again cs,

50 Hz may be a problem regardless of loudness. Small cones do not couple well with air at low frequencies. Even when a simulator/modeler suggests small diameter transducers will go low, it is difficult to measure output (including TL) from the "box" at anything approaching fundamental levels. I have measured this decoupling effect with transducers ranging from advertised cone sizes of 3 to 6.5 inches. Expect the acoustic output to be falling below fundamental levels at frequencies much higher than 50 Hz.

Still, there is a second question here. Will you be able to tell the difference between 95 dB at 50 Hz and 100 dB at 65 Hz?

Excursion requirements drop quickly as frequency increases. When listening to music, are your ears and brain sensitive enough to tell the difference?

I know what the literature says about human hearing sensitivity. Your ears may be different.

Also, it may not be sensible to "design" for a single spec. The Jordan may do things for you that will not be trumped by its inability to do 100 dB at 50 Hz. If so, a subwoofer would be a easy extension of the system.
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