Horatio

Freddy: Missed that altogether! Hmmm. Maybe I need another cup of coffee. Your remarks on the sound in the upper register are not entirely unexpected, are they. The off-axis response tells this pretty well. I am a little surprised that they don't show stronger performance at the low end. But, I have not seen a plot on the Cobraflex before. Yours is the first I've seen. Tx.

Hello Freddy: Thanks for the plots- they clearly show how the KHorn is about the only game in town to get that last octave deep with a horn in a reasonably sized package. They also show the superior ability of a design with much less re-entrance, like the Classic, with respect to the upper end bass response. The data you have on the 151311 is nice to see; I have an older EM datasheet that Madisound published with the 151311 (which is where I bought it), and the parameters I gave earlier came from this sheet. I would expect your data to be more representative of current production. These were bought about 4-5 years ago, and sat until I had time to build these bad boys, about a year ago or so. Good point on the EV12L having potentially more on top; I have a couple EV15Ls that I might just put in the cabinets to give a look-see. Hope your health is better than you expect. That's not fun at all.

I don't know too much about the 1828R, but I have attached the EV datasheet on this driver, which clearly indicates that this driver was specifically intended for re-entrant PA style horns like the Cobraflex. I would guess it is a good match. It's curious how this driver ended up on an 8HD, which is, if I recall, an 800 Hz type horn. The 1828 goes much lower, which is why it is suited to things like the Cobraflex. The Cobraflex was used on the University Classic BECAUSE of the difficulties in folded bass horn/drivers making it to 300-400 Hz in an acceptable manner. I have never heard one of these (knowingly, critically), but I would expect, due to the re-entrant design, one would see some interesting response characteristics as the frequency moves up (e.g., phase cancellations in the turn, when the frequencies/wavelengths are on the order of the size of the turn dimensions). Probably best to cross it out lower than normal and let the tweeter take up the slack. On the other hand, it may be pretty good over a fairly wide range, response-wise; the issue will be the choice made by the designer with respect to where the bend occurs. Radiation pattern will be another issue. Anyone got polar plots on the Cobraflex? 1828R EDS.pdf

The part I'm using is an Eminence 151311: Qts=0.31, Qes=0.32, Fs=38Hz, 8 ohms, Vas=299Liters, die cast frame. This set of T/S pars is ordinarily characteristic of a driver that is suited to horn loading. However, I wonder how the K33E will do in this design (that is, I'd like to hear this); I know the T/S pars on this woofer, they've been published many times. But, I suspect that the K33E has a rising (or at least shaped) frequency response, when measured on a baffle, in order to offset the attenuation experienced in the folded corner horn. This is why I suspect that the K33E will almost always be a better bet in almost any folded bass horn design; the folded designs always suffer in the 'mass roll-off' range of the driver, and will struggle to get to 300 Hz or higher in an acceptable manner. I'd love to see a K33E response plot, if anyone's got one. I'll bet its response is tuned up this way. The University Classic does a better job than most folded designs in the upper end of the bass because the folding is less re-entrant. This Eminence driver works pretty well in the Classic. On top, I have the HR9040/DH1012 being driven at around 350Hz on the biamp setup, using 24db slope crossover, and in home audio environments, the driver tolerates this just fine. There are alot of the HR9040's running around, for a song. You just need to find 'em locally, because they'll cost you twice what you paid, by the time you get 'em shipped, because they are so unbelievably large. The DH1012's are likewise available for not a lot of money, and they are a pretty credible driver. One thing: the HR series horns are 1.4" throats, so your driver choice is going to be limited a bit, although one can use adapters and run 1" drivers (finding 1" drivers that will go to 3-400 Hz is another challenge, though, unless you are looking at the K55/Atlas types). When Keele first published on this new design in the 1970's (AES, 'What's so special about exponential horns?'), he noted the similarity of this design to the midrange horn PWK patented in the 1950's- you know the one: the pretty big radial type design that you see on the 1950's vintage KHorns. Anyway, EV's early HR series are the ones that started the whole industry stampede toward so-called Constant Directivity designs, with the industry trying to reduce the overall envelope of the horn to accomplish the same ends. But, physics will, in the end, have its way. The early HR series sound awfully good; if they're big, well, that's the compromise that must be wrought. PWK is on record about the trials and tribulations of the midrange on the KHorn, and the struggle to get it right, and at an acceptable production cost. I would guess that the reason the K400 horn was introduced had more to do with production cost than it did with sound properties: the older, radial type design had to be significantly more expensive to produce. Mods like the Trachorn are appeals to deal with the directivity issues that have always plagued classic exponential, and especially cellular (lobe issues) designs. This is why I am going to use the EV HR90 on the KHorn; I'd LOVE to use the HR9040, but, this thing is too monstrous to integrate into the overall envelope (e.g., for reasons of domestic peace, I'm going to the HR90...). FWIW.

Saw your post on the University Classic, and then followed the thread back. These are great! I built a pair of these, and loaded them with Eminence 15" drivers. The upper end is EV DH1012 on EV HR9040A horns. This is a magnificent combination. Absolutely stunning! I biamped this setup with great results. I then picked up a pair of Speakerlab K's for a song. Changed the drivers to EV15's, no joy. Changed to K33E's, and found bass, but the response was really peaked in the midbass area. Installed a Type A crossover, and viola! I had that Klipschorn sound that I was after. I still like the mid and top end of the Classic's I've built, and I'm about to fit EV HR90's (little brothers to the HR9040's, which are simply enormous) to the top of the K's. This ought to settle it, really. The HR9040 is gigantic for home use, but, ohhh, the sound... The classic is a great design that performs very very well. I would guess that loading these with K33E's would be even better; I would expect NO issues in the 300-400 Hz range, based on what I heard on my K's. Anyway, nice to see this.

Hello all: I am new to this forum, but not new to horns, have designed and built several sets. I have done a great deal of searching on this forum and elsewhere, but, I can't for the life of me, figure out what I need to do to make a simple change of driver (which also means going to 8 ohms here instead of the 16 ohm K55) in the midrange of my Klipschorn-based system. I am running a Type A crossover. Succinctly: what must be done to this crossover to enable it to work with an 8 ohm driver, using the same crossover point(s)? Is this a simple change of which terminals on the autotransformer, or is it more involved than this? I see that changes like this can be accomodated by ALK's universal unit, but, it seems to me that such a simple change ought to be accomplishable with the Type A as is. Surely someone has done this? Thanks!