OB with a small fostex and a large woofer

[marec]

VDV:-
I thought, from the simulations, that the 108 would be more efficient than the 15a. I put in about -3db of L-Pad to reduce the level. It would seem from my measurements (at 2 metres) that perhaps this wasn't correct. However, I have, I guess, got used to how it sounds and even after correcting the response curve prefer my original x-ver....

Rgds

[Rafal]

Originally posted by rray786



Rafal,

I built Martin’s Eminence 15A OB using the Fostex FE108 E Sigma. The bass only goes down to about 60Hz in my room. That’s probably fine if you listen to acoustic music. However, I listen to a lot of Romantic period orchestral music, organ music, and rock. It just doesn’t do these justice! And I’d have to agree with Sean - the 108 has a pretty ragged response. IMO, it doesn’t sound good without active EQ. With active EQ though, the 108 sounds pretty good.

If I were choosing between the two projects, I’d choose the Jordan with the H-frame. The main question I’d have is whether or not it produces enough dynamic bass. I’m a bit skeptical that a single OB driver can deliver dynamics. Currently I’m using the Fostex 108 actively crossed over to two Acoustic Elegance Dipole 15 drivers per channel. With active EQ (it is required for the AE Dipoles; they have a 12 dB peak at 40 Hz) they go down to about 25 Hz. And people usually jump a bit when they hear the cannon shots in the 1812 Overture!

Sincerely,
Rich

Rich,

Can you share more info about your design? What xo are you using? what amps and how big is your OB? Also, where do you have your drivers positioned?

Thanks,

Rafal

[Nanook]

The suggestion of a Jordan JX92S as a fullranger in an OB system is a good one, as long as it is freed up so that it does not have to handle the bass. A caveat though: I have minimal experience with the Fostex drivers, other than planet10's modified ones.

Regarding using Jordans and a sub, please see my article in November's issue of Affordable$$Audio "DIY Hell-the Spirit of Orion"

The project is an OB fullranger and a sealed active sub borrowing ideas from Linkwitz's Orion design. These are not "knock-offs" or clones or copies,. They however look like the Orions (because I like the cosmetics). If given my 'druthers, I'd prefer a U or H frame woofer (or twp OB types), but practicality required something with a ton of dynamic headroom, and lots of guts to go with it. 250 watt per woofer plate amps do the trick. These speakers were built by myself and my daughter's BF, and he uses them in a multi-tasking (music and HT) system, although with different amplification.

These however do not have the "magic" of my "JE Labs" style OBs using old Oxford J10s and salvaged dome tweeters mounted co-axially. For music only, assuming you have the space to accommodate two 35" wide panels in your listening room, they are still my preference. If not, then narrower designs such as Martin's etc, would be the way to go, and if the need for deep bass, then some kind of active sub system would be my recommendation.

Please note that I am in no way "in the same league" as Martin, SL, JK, or Gedlee, (etc, etc) nor do I pretend to be (I can do the math, but can't be bothered). I am just sharing what has worked very well for me and those that I have followed my suggestions regarding changes to their OB systems. I also have modified the "JE Labs" OB slightly, and that seems to improve the bass across the board. No active eq, or BSC . just the drivers...

I guess I am just trying to reinforce the idea that a small full range driver and a sub(s) can work well together, that active amplification for the subs is definitely a worthy avenue to pursue, and that in the end you will most likely end up with something that is far better than you could have imagined, requiring some minor tweeking to get them very satisfying, regardless if using them for HT , music or both.

stew

[rray786]

Originally posted by Rafal



Rich,

Can you share more info about your design? What xo are you using? what amps and how big is your OB? Also, where do you have your drivers positioned?

Thanks,

Rafal

Hi Rafal,

Well, my OB system is in a state of flux. When I wrote the above, I was using a LR4 crossover of 238 hertz. Now I’m using a LR4 crossover of 2,000 Hz (which gives a huge sound) and I plan to cross over to compression horns (B&C DE250) instead of the Fostex drivers in a few days. (Since this will no longer be a fullrange project, I’ll report the results on the Loudspeaker forum.) I’m using a DCX 2496 active crossover, DEQ2496 active EQ, a Behringer A500 amp for the Fostex drivers, and a Behringer EP2500 amp for the AE dipoles. The DCX is overkill since I have active EQ; I bought the DCX first but found its EQ capabilities were not good enought for my needs. And the fan on the EP2500 drives me nuts! (I’ll eventually mount the EP2500 in another room.) The Fostex driver is mounted 39 inches above the floor with the two AE Dipoles below it on a 18 by 46 inch baffle. The baffles are about two feet away from the wall and are crossed slightly in front of the listener.

Is all of this worth it? Well, I’m not sure. The sound is absolutely huge and sounds the closest to live music that I’ve ever heard. But, I spent $1,200 US on the Fostex and AE drivers and another $1,300 on the amps, crossover, and EQ.

Sincerely,
Rich

[tinitus]

Originally posted by rray786



Now I’m using a LR4 crossover of 2,000 Hz (which gives a huge sound)
with the two AE Dipoles
Rich

2 AE dipole drivers up to 2khz, thats quite interesting

Maybe you should consider to make it a 2.5way with one AE driver cut in/above the BSC frequency, so that you have only one woofer playing midrange...could be important, theoretically