[FlorianO]

Quick&dirty idea:

Jordan JXr 6HD XOed  @ 200Hz, 2nd order to a 15 incher (Augie ?).


Whaddayathink  ?

[JLM]

Years ago the Chicago Audio Club (the loud and proud audio gangsters) were playing Jordan 92S in tombstone looking OBs at the Midwest Audio Fest.  Any mid/tweeter with reasonable high Qts should work.

[Rudolf]

Your X-over will be WAY too low and too flat.
I`ve tried some 3" FR (Fostex FF85K, FR83, Veravox 3) with double 10" woofers in dipole configurations. Xover was 250-300 Hz/4th order and that was still challenging for those little drivers.

For 200 Hz you should at least look in the 5-6" class for drivers with xmax >4 mm. Only the 8" class should be comfortable under all conditions.

[JeffB]

There is the following comment on the Jordan page
http://www.ejjordan.co.uk/drivers/jxr6.html

"The low frequency response of the JXr-6HD has been extended to a remarkably low limit to enable its in-box performance to be directly matched to appropriate, high quality sub-woofers. To achieve this, the conventional rear suspension has been omitted and the system resonant frequency and 'Q' values are set primarily by the acoustic suspension provided by the volume of air enclosed within a small box. This technique also provides a significant reduction in low frequency distortion."

To me, this reads that it won't work in open baffle.

This driver has got me thinking a lot lately about speaker sizes and frequency response plots.  Unfortunately, I am not coming up with answers.
The Jordan page states that this driver effortlessly cover the range 100Hz to 30kHz.
The frequency response graph is amazingly flat from 100Hz to past 20kHz at 90db.
However the specs rate it at 85db at 1m/1W
Further this driver's graph shows 75db output at 25Hz, which looks as good if not better than most 15" subwoofers.
I have read the sound propagation is uniform with respect to frequency.
Looking at the frequency response graph, this looks like the ultimate driver and appears to not even really need subwoofer help.
However, my experience in listening to speakers tell me that a 2" driver can't make bass.  It is logical to assume that it can't move enough air, but the frequency response graph shows otherwise.
I have been looking for subwoofers in the 15 to 18 inch range to provide flat response below 100Hz to pair with such a driver.  Flat response below 100Hz does not appear to exist even for 18 inch drivers.  Honestly, this little 2 incher looks just as good.  I have found 1 exception so far and that is the Dayton Dayton #295-455 15"
http://www.partsexpress.com/pdf/295-455.pdf
The response of the Dayton is not smooth and flat, but at least it doesn't drop like a rock below 100Hz.

The only thing that I can think of involves power handling and listening distance.  The best example I have is some earphones I was looking at the other day.  They were a single driver with a response from 25Hz to 18kHz.  No +/-db or graph provided.  However lets just assume it was pretty flat.  Since sounds propagates uniformly with respect to frequency this looks amazing.  However, it can only handle enough power to provide listening enjoyment in the millimeter distance.  Trying to turn it up louder would either destroy the speaker or at best probably loose linearity.  So with the Jordan, if you want 90db at 6 meters instead of 1 meter, one needs a 6db boost in output.  Plus the graph already appears boosted 5db over the 85 SPL rating.  Perhaps the driver can't take this much power and perhaps linearity falls apart with any further power applied.  It is too bad manufacturers don't provide frequency response graphs at 5 or 6 meters at 90db or so.  This would seem a better result for what you will hear at the listening position.  Too bad the Jordan page doesn't list power handling for this driver.

Still, this driver looks amazing to me.  Too bad it is so expensive.
I have bought a tangband 3" to play around with since it was $15.  The tangband was pretty flat to around 110-150Hz and is suitable for open baffle.
http://www.tb-speaker.com/detail/1208_03/w3-871sc.htm
I haven't hooked it up yet.

[mcgsxr]

75db at 25Hz is fine, IF it is 75db everywhere else.  As it stands, at 10db down, it will be relatively quiet vs a 15 that is 85-99db at that point.

I think it is important to look at the region that the driver will operate in, and compare the relative slope inside that bandpass - not looking at what db a 15 is at 400Hz, compared to 50Hz.  Look at 25-100Hz for that sub, and it should be relatively flat.

Bass (OB especially) is often EQ'd anyway, and with more XMAX, and larger surface area, comes the ability to move more air, and be more impactful.  My DIY Cable FR125's will make some bass at 40Hz, but it is -6db compared to 100Hz, and NOTHING compared to my dual OB 12's at 40Hz, which are biamped, and bass boosted.

Implentation is at least as valuable as raw data...

[opnly bafld]

JeffB,
The graphs you are looking at and comparing mean nothing in relationship to each other.
Some of the drivers have been measured in boxes (including the PE IB subwoofer-15 cuft) and others are measured in a way that shows no gain from a box or a room.

Hope this helps,
Lin

[JohninCR]

Jeff,

Be careful what you read into graphs, especially at the extremes.  For example, that little Jordan reaches its excursion limit at only 56db at 25hz.  Another example is Eminence.  The graphs for their woofers are meaningless below 200hz unless it specifically says so.  I talked to one of their tech people, who said the below 200hz response was too dependant upon the alignment, so they don't measure it.

[JLM]

BTW, Jordan is notorius for exagerating driver performance.

[FlorianO]

BTW, Jordan is notorius for exagerating driver performance.

Ah. Good to know . While it doesn't bode too well, I've read some raving reports about that driver.

The reason for asking about the JXr 6HD on OB in the first place is along the lines Jeff mentioned.

IF (and that is a big IF) that lil' driver can reach 100 Hz -- btw,  for the stated T/S params the F3 is about 150 Hz -- XOing it an octave higher at 12 dB should be safe without risking that the lack of back suspension would launch the cone all the way to the listening position

So, one hand 100 Hz from a 2 incher doesn't sound too good, as Rudolf said. Maybe they are claiming that in a box or very specific setup .... who knows.

The only way to know for sure is someone to measure the T/S params in free air.

Any takers ?

[JohninCR]

BTW, Jordan is notorius for exagerating driver performance.

Ah. Good to know . While it doesn't bode too well, I've read some raving reports about that driver.

The reason for asking about the JXr 6HD on OB in the first place is along the lines Jeff mentioned.

IF (and that is a big IF) that lil' driver can reach 100 Hz -- btw,  for the stated T/S params the F3 is about 150 Hz -- XOing it an octave higher at 12 dB should be safe without risking that the lack of back suspension would launch the cone all the way to the listening position

So, one hand 100 Hz from a 2 incher doesn't sound too good, as Rudolf said. Maybe they are claiming that in a box or very specific setup .... who knows.

The only way to know for sure is someone to measure the T/S params in free air.

Any takers ?

OK, just for grins, and btw I'd love to have 64 of those little Jordans to build a pair of arrays.  In an infinite baffle the driver hits it's excursion limit at 100hz at only 80db.  At 300hz things become more respectable with a 99db limit before becoming excursion limited, however, that doesn't even consider OB bass cancellation.

Like I always say, the place to start with any OB idea is Linkwitz's DipoleSPLmax spreadsheet.  Since you have no box to turn the rear wave into something it isn't in order to inflate the overall bass response, the potential output from a driver is pretty straight forward.  That's why when I use my FE108's (twice the cone area of the Jordans) in OB, I cross them at 300hz or higher.  Plus I limit the volume to only moderate levels below 90db.

[lizardBrain]

I am a big Jordan fan. I have a pair of the JXrs and am going to pair them with two Aurum Carus 6.5 per side in an MTM. Roll it off around 200, 1st order.

Too many projects...

[FlorianO]

First order ?!?! And I thought I was pushing the envelope... You are talking about a  small, closed small enclosure, right ?

John,

You were right, I should have started with Linkwitz spreadsheet. A quick perusal of that spreadsheet -- and engaging the brain for a change -- brought some common sense in me. It doesn't make much sense to consider that tiny driver on an OB, at least not seriously. Maybe during a "just for shit and giggles" afternoon if I already had the drivers, but  otherwise...

The overall lesson is not to get carried away by the hype