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In Reply to: RE: Tracktrix Horn Upgrades posted by John Sheerin on July 23, 2016 at 11:03:09
regarding Le Cleac vs. Tractrix, Beuce Edgar would disagree. IMHO - regarding round vs. rectangular mouth, we conducted several tests switching only horns and leaving everything else in place and found that rectangular mouth actually sounded superior to round, ceteris parabus. The photo is of my latest 340 Hz tractrix horn and the jig I built for it.
Edits: 07/24/16 07/24/16 07/24/16 07/24/16 07/24/16 07/24/16 07/24/16Follow Ups:
I don't think you read my post very closely. I said avoid a square throat, not mouth. I said use a round over at the mouth, ie, a radius at the edge of the horn's mouth. This sounds much better than a sharp edge in my experience, at least with midrange horns. Le Cleac'h horns have this as part of the calculated flair. You can stitch something similar on to a tractrix horn and it will be fine as well.
Fair enough. The adapter that also serves as the driver mount provides for a smooth transition from square to round throat. I made two types of adapters - 2" and 1.4" (for Altec 288) BTW, another discovery we made was that in home environment Altec 288 bested JBL 2441 by a tiny little bit. I said in home environment because in a large room with the volume control considerably up, Altec 288 tended to be a little bright and then JBL 2441 sounded better. This can be explained with JBL superior power handling ability. Again, all strictly IMHO.
Hi John,
For a basic 2 way JMLC mid horn + direct radiator.. What XO (passive) do you find works best? There's the 'quasi-optimal 18dB BW' slope espoused by the late JMLC of course, but you may have liked something else that worked for you.. Thank you.
Regards...
Hi Fred,
Each case is likely different, depending on the directivity of both devices, relative positioning, and for passive crossovers the response and impedance of the devices. I usually use digital crossovers and play with the slopes and crossover points in software to get the best match I can find in the combined polar response. For my current system, for the midbass (15") to midrange horn crossover, I found a 6th order Linkwitz-Riley HP at 770Hz for the midrange and 550Hz 6th order LR LP on the midwoofer worked best. Those don't sum to flat, so there was additional eq applied to both drivers to get the final acoustic slope which ends up being a non-text book curve. I attached a screenshot - the solid curves are the initial slopes I used, and the dashed curves are with eq applied to get a flat response.
Hi John,
Thanks for sharing the details of your speaker XO.. Yeah, it all boils down to certain variables.. There's a steep learning curve for some non-engineering folk like me when it comes to this.. I mean, knowing where to start (beyond the empirical) with all the options for a mid horn 2 way with DR midbass. So I really envy guys who can "pick these things up" easily.
I've seen a photo of your JBL Be pro based diy JMLC wood mid horn with the 15" DR bass bin, plus modified horn tweeter on top in another forum almost a couple of years ago. It really looked sweet, and I bet it sounds sweeter.. I'm thinking though that with vintage type drivers (Altec-GPA small format comp driver) and Altec midbass, maybe I could get away with some mild Eq for the mid horn and likely non at all with Altec DR midbass.
Anyway, apologies to the OP for diverting the topic to crossovers.
Regards....
Hi Fred,
How much eq you would need would just depend on your drivers. I needed some EQ on both midbass and midrange to get it to meet my crossover targets. Here's my JBL 2225 in its sealed enclosure along with my target and the eq needed.
Thanks John... I'm curious as to what Active XO/DSP software, and what amps for multi-amping, and source/s you use.
The convenience of changing XO settings on the fly to hear the differences is really nifty..
Regards...
Hi Fred,
It sounds weird, but I use an old Mark Levinson car amplifier I have that has an AD Sharc built in along with 16 channels of discrete amplifiers. I'm using Crown amps for the low frequency channels. I have a miniDSP setup that I eventually want to transition to that will let me use FIR filters in addition to parametric ones. Then I'll have to find some different HF amps to go with that. I do all my filter design and measurements with Matlab.
Hi John.. Thanks for the details, miniDSP seems like a good affordable kit for relative new comers to active-digital.. That's actually cool, ML car amps. If they're relatively old, I'm also a fan of Madrigal Audo Labs designs, even if I still havr a bias for glassware. I guess you have the Harman setup for the mids and up since HK owns both JBL and ML these days.. Nice, I've seen a few folks use new Crown amps for the LF and low mids.
Thanks again.
Regards....
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