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 ?
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 ?
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.
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.
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.
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.
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
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
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.
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.
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
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
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.
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.
Is not fundamental resonance of more importance for low frequency response than cone excusion? For a correctly tuned cabinet the cone excusion should be minimum at around the -3db level. Agreed, a high excursion will help at mid-bass frequencies and coping with the adverse effect of the port much below tuned frequency.
My experience with the Jordan is that it has a relatively low f0 for the cone diameter, so allows tuning of the cabinet to effectively boost the bass response through a reflex port or transmission-line port. I don't know the effect of the latter on cone excusion but I know using the reflex the excursion around the tuned frequency is a small fraction of that say 20Hz higher. The port/VTL resonance effectively loads the driver so it draws much more power for a given excusion. This effect is noticeable with poor amps that cannot provide for the extra load.
My experience with the Jordan is that it has a relatively low f0 for the cone diameter, so allows tuning of the cabinet to effectively boost the bass response through a reflex port or transmission-line port. I don't know the effect of the latter on cone excusion but I know using the reflex the excursion around the tuned frequency is a small fraction of that say 20Hz higher. The port/VTL resonance effectively loads the driver so it draws much more power for a given excusion. This effect is noticeable with poor amps that cannot provide for the extra load.
Yes you are right, the cone excursion does indeed reduce at the line/port resonance.
In the ML-TL I am contemplating, the line/port resonance is at about 35Hz, and so the cone excursion peaks at about 50Hz, just where I am assuming most of the low bass will be ! (It also rises below resonance, but hopefully there won't be much energy down there for music).
So my dilemma is whether to build the TL cabinets and hope the bass is OK, or put the Jordans in smaller boxes and use a separate sub.
In the ML-TL I am contemplating, the line/port resonance is at about 35Hz, and so the cone excursion peaks at about 50Hz, just where I am assuming most of the low bass will be ! (It also rises below resonance, but hopefully there won't be much energy down there for music).
So my dilemma is whether to build the TL cabinets and hope the bass is OK, or put the Jordans in smaller boxes and use a separate sub.
I'll second that. I have the 48MLTL and really like the sound. Adding a sub to it does nothing much to add to it. By the time the sub is matched up for dB and cutoff, it is hardly contributing. (In my room, the sub drops off below 25Hz). If I was building again with the sub in mind, I'd go for the 31MLTL.
BTW, at 35Hz, the driver cone hardly moves in the MLTL. Don't rely too much on computer spreadsheets to tell you how the driver will perform.
BTW, at 35Hz, the driver cone hardly moves in the MLTL. Don't rely too much on computer spreadsheets to tell you how the driver will perform.
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