OK, Eminence 15Alpha ordered- OB Help

[britbug]

Hi, after the usual months of procrastination, I am finally going to go for an OB implementation of my JX92S, with eminence 15alphas for bass. Same dimensions as MJK's nice project.

I will eventually try and implement something similar for the Lowther DX2, but right now this is as big as will fit in the space I have.

Since the Jordans have a load of X max to play with (and I have found them to sound really good even when their displacement is a heck of a lot) I am going to try an cross them over very low, and with a simple 1st order too, at least first.

I am looking at 150 Hz x over, anyone have any better ideas?
I found a great inductor calculator at http://colomar.com/Shavano/inductor_info.html
and will wind my own, & tune it on the fly.

Cheers, and a good summer to all!

Graham

[dviswa]

Hi Graham,

Wishing you luck. My own project has had to be put on back burner due to lack of time. Hope you succeed.

Dinesh

[pikkujöpö]

There is a nice open baffle speaker made by someone in Danmark.15" woofers, Jx92s and a ribbon tweeter.Here is what "scorpion" translated :

Crossover between bass and mid is active with 48 dB/octave at 180 Hz. Only the tweeter is passivbly crossed over at 12 dB/octave at about 7 kHz complementing JX92S.

[tinitus]

Originally posted by britbug

I am looking at 150 Hz x over, anyone have any better ideas?
I found a great inductor calculator at http://colomar.com/Shavano/inductor_info.html
and will wind my own, & tune it on the fly.

Cheers, and a good summer to all!

Graham

Aircore inductor wont cut it ... you need a big trafo inductor

Inductor needs to be active just below 100hz, and with a bit of luck you will achieve 150hz ... with help from a paralel cap or RC(resistor/cap)

[MJK]

If I were doing an OB design with the JX92S and an Alpha 15A, I would start with the following configuration.

Baffle is 24" wide x 38" tall.

Alpha 15A centered 10" from the bottom.

Jordan offset 2" off center and 32" from the bottom.

Crossover using 2nd order low pass at 200 Hz and 2nd order high pass at 400 Hz connected in phase. I believe 2nd order crossovers are a must for this type of OB design.

This produces a SPL response that is 89 dB/w/m +/- 1 dB down to 50 Hz and is -3 dB at 40 Hz.

I am using assumed properties for the Jordan that I pulled off the Internet, don't remember where, and my own measured Alpha 15A properties. If I had my own measured Jordan properties the design might change a little, but it looks really good right now.

[britbug]

Martin, thanks!
I will make baffle as described & try differing X overs.
I have no real measuring equipment (although I have an old HP tube signal generator for some sweeps) but will report back within a couple of weeks.

[Phats]

Please read an article fro Martin J. King about OB's with an Emince 15 A, vey helpfull!

Regards, Stef

[pikkujöpö]

Originally posted by Phats
Please read an article fro Martin J. King about OB's with an Emince 15 A, vey helpfull!

Regards, Stef

Martin J. King = MJK

Very informative article indeed.I think now he has plans to test JX92S in open baffle.Can't wait for the result.

[dezzz]

I have been running my Jodan JX92s's on 24" x 48" baffles without a filter, supported by two VIFA M25WO woofers with unknown specifications crossed over at 100hz 2nd order. SPL levels are more than adequate for my use. The only problem is that the JX92s's seems to become more directional when taken to its xmax limits, don't know if this makes sense or if I am imagining things.

I too am very interrested in what you latest experiments will bring MJK.