Horatio

Been away from this forum for a while, but am getting ready to make another biamp tuning run on my khorn setup. Toward this end, I wanted to see if anyone on this forum has dabbled with Temporal Equalization, the process that Fulcrum acoustics uses. The approach can do very interesting things, like eliminate the sonic effects of horn reflections. Got your attention now? For me, biamped and digital is the way to bring the khorn to a modern spec, as it enables one to address some of the long-standing issues with this speaker, and enables it to perform at a very high level in contemporary terms. But beyond being able to tailor the crossover and deal with time alignment, we still have the issues of horn reflection, and for compression drivers with phase plugs, path distortions due to those phase plugs. Fulcrum's (patented) TQ equalization approach uses IIR and/or FIR approaches to remove/minimize these contributions. They are the last bits to be dealt with, in my opinion. Anyone using the TQ approach with their digital crossover?

I have been using a MiniDSP to run my Speakerlab K (uses K33E woofers), that has EV HR6040+Altec 288 top end. This is a two way configuration, and the Altec drivers give a bit more top end than the EV DH1012's I've used, enabling this to effectively be a two-way setup. The bass horns were set up along the tuning parameter lines that Greg Oshiro has done using a different crossover. I have found those frequencies and gains to work reasonably well, although I had to hand tune some of the gains for my room. I run the LeCleach butterworth configuration on the filter. Very pleased with this. Run 100W Mosfet monoblocks on the bottom, SE84 SET (2w) on the top. I am not necessarily golden-eared, but this arrangement gives a system that images unlike any horn system I've ever listened to. Quite pleased. Be careful with the MiniDSP, and turn your amp gains way down. While messing around with my unit during setup, I was able to introduce transients into the horns that actually took pictures off the wall in my livingroom (not to mention scaring the he** out of me in the process), Approach with care and caution, and you will be rewarded. I keep my unit powered on 24-7, because the management of the turn on and shut down of my system requires a bit of care (tube amps don't turn off instantly). So, I sequence the power to the system using one of the power sequencer units often used in pro sound. Have fun!

Thanks, will check with Steve as well. The ZKIT1 was an easy build, but mine was complicated by the fact that the board design and schematic were dated and the parts list incomplete. A major complication was the fact that builders invariably had to use the Edcor transformers, and the power transformer did not have a center tap as originally designed into the circuit and board. I fashioned a pseudo tap that worked fine. I understand all these things were corrected in the latest board rev (which also uses the same pseudo tap I used). Once I sorted those details, though, to ensure a clean build, it went together and worked without much incident. Just had to get used to working with tube amps again (feels a bit like picking up a rotary dial telephone, you know? But the sound....). -M

Dave: I run a ZKIT1 SE84, and I am interested in the mod you describe. Are these replacements for the 33 uf caps on the high voltage taps? I have sorted through the ZKIT1 posts and don't find any mention of this mod. Thanks! M

OK, that link led to about the funniest audio site I've been on in quite some time!

Modding compression drivers is a pretty touchy thing. On good ones (pro sound, large format), the clearances are pretty tight and the machine work also quite exacting. The only thing I've seen done is the introduction of ferrofluid in the coil gap, ostensibly to improve power handling, and can also be claimed to smooth response. Speakerlab did this on their later compression drivers for their Khorn knockoff. The driver was based on the EV 1824, if I am recalling correctly. I had written to them around 1980-81 about this alteration, and they sent me the frequency response curves for the non-fluidized driver and one with fluid. I think these were on their K400 knockoff midrange horn (H350, a model number like this, anyway). The curves did reveal a somewhat smoother response. The fuuid they used was called Magnar. I suppose you might be able to somehow introduce a different phase plug....other than that, it gets pretty tough, pretty fast, I think. The concept also presumes that the manufacturer somehow missed key factors during development, and I have rather strong doubts that companies like JBL, Altec, EV and the like did this. I can see more likely changes that address manufacturing shortcuts or cost/value engineering compromises. But this is less likely to be the case in the high line large format drivers. That's speculative, of course. -M

OK, that's one for the books, for me, anyway. I've been using a MiniDSP on my Khorns+EV HR6040's (w/Altec 288's), and a Decware SET to drive those 288's. Using the MiniDSP for over a year; added the SET last spring. I have found that the LeCleach parameters worked spectacularly well for setting up the crossover. In this design, the low pass for the woofer can be set to something like 305 Hz while keeping the high pass for the tweeter (top end, however you call it) at 400 Hz (I think I have the LeCleach design set to 350Hz, which is why the lower end and upper end turnover points are as they are). The delay on the top is incremented a bit, and the slopes are butterworth, 18db/octave. Polarity on the top is inverted, also. Some have commented that they have tried this and that this doesn't sound any different than straight LR @400 Hz and 48db/Octave, but I beg to differ. The imaging simply pops into existence with the LeCleach parameters, at least for this combination of bass horn and top end. I just A/B'd this with the LR 48 db settings again yesterday, and it is undeniably favoring the LeCleach approach. Anyone who claims that horns can't image, or that Klipschorns can't image are in for a rude awakening with this system. Your idea is clever! How did you arrive at 7.5 ms for the delay? -M

Tom: Thanks for that! I finally dug up what I am running in those Classics I built: Eminence 151311, which has these parameters: Fs = 38Hz Qts = 0.31 Vas = 299 liters mms = 60 gm xmax = 5.5 mm SPL = 99 dB Now, that is not a shabby woofer, at least on paper. I was going for as high an Fs value as I could find in a 15" (that had low Qts as well) to improve the uppoer end of the response. The Legend CB15 is reported as having these pars: Fs = 34 Hz Qts = 0.34 Vas = 336 liters mms = 70 grams xmax = 4.8 mm SPL = 98 On paper, those two woofers could be mistaken for each other. I have no idea about the actual sound differences! And the Crites' CS1526: (K33E) FS: 26.3Hz SPL: 97dB Xmax: 7.15mm Pmax: 150W Re: 3.36 ohms Vas: 506.3L BL: 12.49 Qe: 0.27 Qm: 9.93 Qt: 0.26 It is clear that the woofer I am using and the Legend CB15 have pretty similar specs, as you can see. The Crite's K33E replacement is quite different (and differs from many of the published sets of T/S pars for the K33E that can be found elsewhere on this site). Hmmmm. What I DO know is this: I have a set of Speakerlab K's, and I was not happy with the original WS1504's that were in these, and replaced them with EV15L's. Still not what I liked, at least did not sound like the real thing. I bought K33E's from Crites and those babes woke those bass horns right up. Better on the bottom, much better above 250 Hz. I put in the Klipsch Type A or AA (can't recall, right now) and it got better still. In fact, that combo would raise the hair on my neck the way the Klipsch originals would. Never looked back with regard to woofer choice. I am powerfully inclined to pick up another pair of the K33E replacements and see what these do. Thanks!

Thanks for that. Checked the T/S specs on the CB15 Legend, and these match very close to circ 1998 K33E T/S data I have tucked away. Unfortunately, those pars are very different from the Crites CS1526, which is pushed as a K33E replacement (CS1526 has quite a bit lower Fs, lower Qts and about 40% bigger Vas, for example, compared to the CB15). How's the bass on your 'Dean with this driver? It is promising that your high end is up there; this is what I am most concerned about, as I figure the bottom end, with a well-matched driver, ought to take care of itself.

Hello all: A few years ago, I built a pair of University Classics, and I fitted these out with Eminence woofers with T/S parameters that ought to have been decent for horn loading (low qts, fs around 45 Hz or so; don't recall the rest, but can dig them up, as I have a file somewhere). I like the horns, but I think the woofers aren't the best fit- lows aren't where I expected them to be, and moreover, with the gentle folding of the 'Classic, I expected to reach 400 Hz and better without much issue. These struggle to make it. I have not tried actively EQ'ing them, but really don't want to go down that path just yet. My question is, has anyone on this list tried other woofers in this design, and what seems to be the recommendation? The old University C15W does not seem to have published T/S data, so it is difficult to find something that is a reasonable match. I am considering picking up a pair of K33E's, because my experiences with a Speakerlab K showed that the standard W1504's, and some EV15L's were absolutely left in the dust by K33E's. The horns came alive with those K33E's. Anyone with advice on this? I guess I can buy and try, but if any of you are running a set of Classics and are happy with the woofer choice, I'd like to hear about it.

If you check the EV datasheet for these, they are good to 500 Hz. EV recommends an 800 Hz crossover if you are wishing to keep to the coverage angle specifications (e.g., '800 Hz beamwidth limited' minimum recommended crossover frequency). -M

FYI, scanned ebay and saw these, for those interested in using this type of horn: http://www.ebay.com/itm/EV-Electro-Voice-HR90-Horns-/280949385362?pt=LH_DefaultDomain_0&hash=item4169e36892

I use this on my Khorns+EVHR6040+Altec288, where the top is driven by a Decware single ended triode amp. The miniDSP is the least of my worries in this system. The one thing I *really* like about this little guy is, contrary to, say, using a Behringer, the miniDSP can, via a *single* volume control, run the whole deal. No need to find buy or build a means of running all the DACs from their trimmed positions.

If you are looking for a really capable crossover and don't want to spend huge $ to get there, take a look at minidsp.com. I am using their standard unit 2X4 to biamp a modified set of Khorns (Khorn bottom, EVHR6040+Altec 288 on top), and I can do practically anything I wish to with this unit, including some DRC stuff. Cheaply. And with better quality than I was able to acheive with any active analog unit I tried. The 2X8 units give even higher sampling rates. No affiliation, just a veteran of the 'gone active' campaigns.

The EV is fiberglass. That 18 Sound horn mentioned further down in this thread looks really cool. Pity it doesn't load lower. If you are looking for a retro type of look, and you are good with the loading to 500 Hz, you might look at the EV HR90 or HR60. These are the little brothers to the great whites, EVHR9040, HR6040. They are much easier to deal with in terms of size, and fit a rectangular opening with a full bezel around. -M