05 July 2008

DIY Sealed Jordan JX92S Bookshelf Speaker

A while back I purchased a pair of Jordan JX92S fullrange speakers. At the time I purchased them I didn't really know what I was going to do with them, but having read so many positive comments about these drivers, I really wanted to hear them for myself. At $180 each, the drivers are costly, but these drivers have a large Xmax, good low end extension and a fairly smooth frequency response. It is uncommon to find all of these attributes in a medium sized fullrange unit. I was eager to hear these drivers, so I figured I would first try them in a sealed loudspeaker enclosure, with the idea to convert the box to a bass reflex or aperiodic enclosure later on. Figure 1 shows the calculated frequency response for the JX92S driver in a 0.25 ft^3 sealed box. The orange line is the calculated response using the manufacturers T/S parameters and the yellow line is the calculated response using parameters that I measured with a Dayton Audio Woofer Tester 3 (WT3). The calculated impedance is shown in Figure 2. See the Jordan JX92S fullrange driver page for the measured Thiele-Small (T/S) Parameters.

Jordan JX92S Frequency ResponseFigure 1: Calculated Frequency Response - Jordan JX92S in 0.25 ft^3 Sealed Box

Jordan JX92S Impedance Response
Figure 2: Calculated Impedance Response - Jordan JX92S in 0.25 ft^3 Sealed Box

For the loudspeaker enclosure I used prefabricated 0.25 ft^3 curved cabinets from Parts Express
. A rectangular or do-it-yourself (DIY) box of the same volume would also be fine. Damp the walls of the cabinet with upholsterers felt or use poly fill to stuff the box. Adjust the damping materials to suit your taste. The driver is counter sunk, but I didn't have any black low profiles screws on hand and I wasn't about to run out to buy some.

Jordan JX92S Sealed EnclosurePhotograph 1: Jordan JX92S in a 0.25 ft^3 Sealed Loudspeaker Box - Front

Jordan JX92S Sealed Loudspeaker
Photograph 2: Jordan JX92S in a 0.25 ft^3 Sealed Loudspeaker Box - Rear

The measured frequency response is shown in Figure 3. The frequency response measurements were completed using a Radio Shack 33-2050 SPL Meter. On axis, this is a fairly smooth driver. At about 15 degrees and more off axis, the high frequency response drops off
rapidly due to beaming.

Jordan JX92S Measured Frequency ResponseFigure 3: Measured Frequency Response - Jordan JX92S in 0.25 ft^3 Sealed Box

The impedance response was measured using the Dayton Audio Woofer Tester 3 and is shown below in Figure 4.

Jordan JX92S Measured Impedance
Figure 4: Measured Impedance Response - Jordan JX92S in 0.25 ft^3 Sealed Box

The temptation will be run these drivers fullrange and some may actually be happy by only sucking the drivers up against the wall. However, most people will likely prefer some amount of baffle step correction / compensation (BSC). The amount of attenuation required will be a function of the listening room, amplifier and personal taste. I was happy with about 4.5 dB of attenuation (Lbsc=1mH and Rbsc=3R9 for a 7.5" wide baffle). You can use the online baffle step correction calculator to determine a
suitable circuit for your baffle width and desired attenuation.

Jordan JX92S Temporary BSCPhotograph 3: Temporary BSC for Jordan JX92S Sealed Loudspeaker

Most will likely be satisfied with this driver running fullrange plus a simple BSC. However, off-axis the high frequency response starts to quickly disappear. Personally, I like to toe the speakers so they cross just in front of the listening position with Radio Shack 40-1310 Super Tweeters toed out at the same angle. Add a diy active subwoofer (I cross mine in at ~60 Hz) and this makes for a very pleasant and simple 2 channel system. It seems that everyone who hears these drivers prefers them over the Fostex FX120. Myself, I prefer the FX120. I don't find the JX92S as "engaging" as the FX120. Next step is to convert the speaker box into an Aperiodic Loudspeaker Enclosure. Stay tuned.

Related DIY Jordan JX92S Loudspeaker Projects:

What's Playing: Sarah McLachlan -The Path of Thorns (Terms)

6 comments:

  1. Hello! Which do you prefer the sound of, the Jordan in the sealed or the Fostex project in your blog?

    Jeff

    ReplyDelete
  2. Hi Jeff, I assume you are asking about the FX120. Personally, I like the FX120 better, but that is likely a matter of personal taste. Everyone else who has heard the two at my place prefer the JX92S.

    The sealed JX92S makes almost as much bass as a larger and ported FX120. The JX92S can actually move some air and still sound good.

    Cheers

    ReplyDelete
  3. hello:) i play harp and violin :)

    ReplyDelete
  4. Howdy. I built an almost identical system, in 2004 I think it was. Same size and brand of box, except I got the ones with straight sides. I don't think the curved sides were available at the time. I built it for an office, but I am using it at home now. I built the powered sub with a 10" Peerless XLS driver and matching passive radiator. Those passive radiators are getting hard to come by. Discontinued, I think.

    Some observations...

    The Jordan drivers are designed to be toed in. Works good that way.

    I did not use a BSC circuit at the office, because I was able to place the speakers on the walls, which is ideal. However I did include a BSC-like circuit in the box to remove a 5dB dip around 200Hz. From your measured response, it appears you do not need it.

    At home, the speakers are about three feet from the back wall. I can't help it. I compensate for the baffle step using a graphic equalizer. It requires about a 4dB shelf centered at 630Hz.

    I also use the EQ to boost the low end, +6dB at 60Hz and lower. That gives a flatter raw response for the crossover to work with. It's a 4th order Linkwitz-Riley, crossing over to the sub at 80Hz. I actually have separate EQ's on the mains and the sub. (It's an accident of history that I have the two EQ's, but it works real good.) If you are not boosting the low end of the mains, I think 60Hz is much too low a crossover point. If I were not using the EQ to boost 60Hz and below, I would cross over at 120Hz rather than 80.

    One more thing. Have you rotated those bolts 90 degrees yet? :-)

    ReplyDelete
  5. P.s. It was 2005 when I made mine. Here's a thread about it. You'll see that the "BSC-like" circuit was going to be a BSC, but it turned into something else. :-)

    Click for the sordid details.

    ReplyDelete
  6. Hi Jive,

    These JX92S are from a 2007/2008 run and there are numerous forum posts that indicate they are different than the earlier Jordans like you used. I measured a Qts closer to 0.55 while the previous runs were reported closer to 0.4. So these should be a bit warmer in a sealed box.

    60Hz worked best for my room setup at the time as it balanced out the room modes.

    Cheers

    ReplyDelete

GET WEBSITE UPDATES VIA EMAIL