Help with Jordan design....

[navin]

dave,

this might be a culmination of a lot of ideas.

think jx53+125.

jx 53 above 300Hz, jx 125 below 300hz. 6db PLLXO.
jx 53 driven by EL83 PPP (parallel push pull).
jx 125 driven by 30W SS amp (made in India group project)
use amplifier gain to compensate for BSC

next level.
2-4 x jx 53 in line array open baffle.
2 x jx125 in push push box

U see any problems? Any better ideas? A still simpler design? Fostex a better bet?

Sorry for the personal post but I have great regard for your opinion.

[Colin]

I use a JX53/125 cobination in a sealed enclosure and they sound very good. The drivers are very natural and dynamic. Crossover is the recommended 500Hz. After first hearing the Jordans, I gave up bothering with other drivers.

My JX92s are still awaiting enclosures to see how the HF response matches (but the Pass Labs J-Low article claims they're fine into the HF). I have briefly heard the JX92 in a sealed enclosure and I thought it sounded fine (although I wasn't comparing it to anything at the time).

I've also heard Ted Jordan's 4xJX53 linear array system. This has an amazing ability to provide a rock steady image whilst you wander about the room. He uses the array without a crossover, so it operates to around 100Hz and the bass sytem picks up from there. I did notice a slight loss of HF sparkle when I stood up out of the vertical 'beam'. Fine for the favourite armchair though...

Hope this helps.

Colin

[navin]

i am told that tilting the array a bit reduces the loss of HF sparkle. My fear however is that the comb filtering might introduce other distortions not only a loss of hf sparkle.

[AudioGeek]

so do I have room boundary issues putting that 0.5 driver on the back???

My enclosure is about a foot wide. What value of inductor should I use for my 0.5 driver? also, NO resistor in parallel with inductor correct? As we want to totally filter the HF on the rear?

Finally, Can I supplement the drivers HF response with a super-tweeter?

i.e. a piezoelectric or something? And where would the best place to mount it?

Thanks for all the info!!

p.s. vent on front or back?? I can get -3db at 45Hz with WINISD. Should I make the vent dimensions longer to drop off the response sooner to account for room gain???

[Colin]

Other than the HF loss (and that only happens when you're above or below the beam of the array), I don't think there is anything else to criticise about the JX53 array. Bear in mind they are designed to be quite directional and have been designed from the start with array applications.

Regarding the JX92, adding a tweeter may extend the HF but will probably muck up the stereo imaging to some extent (phase shifts, non-time aligned tweeter). The attraction of this driver is being able to use it as a pure point source.

Have a look at some of the Konus Essence reviews for comments on the sound of the driver used on its own.

Colin

[planet10]

Originally posted by navin
this might be a culmination of a lot of ideas.

think jx53+125.

jx 53 above 300Hz, jx 125 below 300hz. 6db PLLXO.
jx 53 driven by EL83 PPP (parallel push pull).
jx 125 driven by 30W SS amp (made in India group project)
use amplifier gain to compensate for BSC

next level.
2-4 x jx 53 in line array open baffle.
2 x jx125 in push push box

EL83? Do you mean EL84 -- i've a couple Class A PP in the works.

I think either of these would be quite stunning, 300 Hz 1st order XO for a single JX53 might limit dynamics somewhat.

Originally posted by AudioGeek
so do I have room boundary issues putting that 0.5 driver on the back???

A little bit, the speaker can't be right up against a wall (hardly ever a good idea anyway). With it used 0.5 it is less of an issue than run FR.

dave

[AudioGeek]

so....

should I run the rear driver full range or roll of the HF????

oooorrrr.......

just thought of this... how about a notch filter?? keep the low end to account for the baffle step, roll of say 3K-10K and have 10K and up full.

That way I can keep them a little closer to the wall, and also have a bit of top end sparkle with the diffusion of the rear off of the walls.

How about it??? thoughts???

Thanks!!!!

[planet10]

Originally posted by AudioGeek
should I run the rear driver full range or roll of the HF????

just thought of this... how about a notch filter?? keep the low end to account for the baffle step, roll of say 3K-10K and have 10K and up full.

That way I can keep them a little closer to the wall, and also have a bit of top end sparkle with the diffusion of the rear off of the walls.

Try it all 3-ways... it will be a room dependant thing... my room loves bipoles (and dipoles)... i am using a broad "notch" on my curretn $20 specials for both BSC and a little more top (8" FRs), i don't see why something more radical couldn't work (as long as it doesnt cause an impedance problem with the amp)

dave

[ozynigma]

Originally posted by planet10


As you roll off the 0.5 driver its phase rotates thru 90 degrees. As it rotates it gets more & more out of phase with the driver that is not rolled off.

When you mount a 2nd driver on the back of the box it will perfectly compensate for baffle step loas. As long as the 0.5 rolloff is above the bafflestep frequency, the phase roll is hidden in the shadow of the box (ie this part of the sound only radiates backwards -- by the time it gets back off the back walls, it is so delayed and so mixed with the room, that the phase roll has little if any effect).

Further, by mounting on the back, it is convienient to mount the drivers back-to-back (push-push) and, if rigidly coupled, actuvely cancels driver vibration and improves downward dynamic range.

of course you can also choose to not roll off the back driver at all and have a bi-pole (works well with FRs)

dave

I am working on some multimedia satellites with 2 x 4" drivers and a tweeter. Front baffle will be slanted back 15 degrees.

I was going to go 2.5 way with both drivers at the front in an MTM configuration and roll the bottom driver off for BSC.

For a rear facing driver how important is symmetry with the front driver?

If I rearface the second driver will it matter that the rear baffle is vertical and the front is slanted?

Does the rear facing driver have to be at the same height as the front driver?

Or what if I slanted the rear baffle mirror image to make a triangular bi - pole configuration?

Howard

[AudioGeek]

so how do I do a broad and deep notch filter?

My baffle is about 12in wide, so probably start at 1Khz -> 10kHz for the notch.

4-6db down or even more.

Thanks!!