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horatio2

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  1. Opening the slot means going to the original throat dimension. I don't recall off hand, but the later models were something like 3X15, and the original models were more like 6x15. You can search on motorboard and find some of the traffic on this. A lot of the later (~mid 60's and beyond- sure others will chime in who know and can recite the particulars) klipsch production work was to fit woofers that would reach to 400 Hz. I went back to the original concept which was to use a very strong motor and the old motor board. Measures a bit more sensitive, and somewhat better low end, while the response near 400 Hz is not as good. I cross at 300 so I really don't care what the response around 400 looks like- would rather cut the compromise the other way. This is a great system in a 2-way configuration, provided you have the right top end setup.
  2. I was an early adopter of minidsp, as it enabled me to solve some long-standing issues that I never could get right using pro-sound analog crossovers. But the early units, as remarkable as they were, had some issues. Particularly regarding the gain structure. I moved to the 2x4 HD and this was a breath of fresh air. The gain structure issues went away, the source selection and volume are now done by hand held remote, and the sound is stunning- quite sharp, detailed, and quiet. I run SET tubes on the top end (Altec 288's into EV HR6040 CD horns, the originals of Keele), and a big MOSFET amp on the bass horn, which is Khorn with opened woofer slot and a much high motor strength woofer. And enclosed sides. All of this to the good, and measurements back it up. Best of all, the sound. The large format old-school CD horns (not the slotted CD horns- those are another kettle of fish) and drivers enable to address some of the long term issues with the Khorn, and the time alignment under active enables imaging that has to be experienced to be believed. I would have no regrets going the minidsp 2x4 HD route as a suggestion, if you are doing a two-way biamp. Hard to beat it.
  3. Don: Yes, I gather all that (FIR, IIR, all that). I run (now) the MiniDSP HD, which is a very nice improvement over the original MiniDSP. In particular, the input and output gain structure is much improved, and, with a SHARC on board, it can do quite a few things, FIR-wise, including serving as a platform for Dirac room tricks, as it supports a decent number of taps. But I got it for the gain structure improvements, mostly. Gunnesses' TQ approach is very interesting, and I really would like to know if anyone on this forum has made any attempts at doing something like this? The Fulcrum approach is patented, but the patents aren't terribly useful if you are trying to do anything with this; they have held the specifics quite close to the vest, understandably. But the basic signal processing notions almost surely have analogs in the RF/microwave/RADAR/SONAR world. So I am wondering if we have anybody playing around with the idea.
  4. Chris: I do believe I agree with you: one must think. And if one does, one discovers there are many avenues. Of course there is always the option of going with the high end pro gear and pushing the button and walking away. But where's the fun in that? I don't see that the low price of minidsp equates somehow to an inferior choice; you should try it to be sure you feel that way. But, there are those for whom the money spent authenticates the approach. Follow your bliss-
  5. I would like to weigh in on this one, having spent much time on this. I run a MiniDSP, one of the relatively early adopters (2010/2011) among Klipsch enthusiasts. I did this after spending a lot of time with a Rane AC23 and another 4 channel active setup (can't recall the name, off hand), but both pro sound. I just didn't want to bail into this exercise at $1K+, when I was not sure of the eventual outcome. Never-the-less, I have devoted quite a bit of time and dollars to it, cumulatively. There is a recent addition to the MiniDSP product line that is about perfect for this- OpenDRC-DA8, which can handle a stereo 4 way configuration, and can do room correction. It isn't cheap but it is way less than some of the other alternatives. On the noise complaints with MiniDSP: I use the original MiniDSP, 2 in 4 out, as I biamp a modified corner horn (top replaced with EV HR6040+Altec 288, driven by Decware SET on top). I do not have, nor have I seriously experienced noise issues with the MiniDSP: you MUST use a good quality power supply, but this is needed in anything that provides a DAC output. I have had WAY more noise problems with the SET than anything else, but eventually got those settled. Anything fed into the horn drivers can be heard, and you will undoubtedly notice all of it. What is more common of a concern is getting the gain structure correct: this means ensuring that your analog input (if you are using this downstream of your preamp) sensitivity is matched to your preamp and that the MiniDSP output sensitivity is matched to your amplifier input sensitivity. Get that wrong, and you will get noise, or poor dynamic range, or both. In my case, the MiniDSP not well matched to my amplifiers, which themselves have different input sensitivities with respect to one another. I have had to resort to line preamps on the outputs to trim in the gain structure. I don't think I would have had to do that for the OpenDRC-DA8, as its DACs drive to a much higher output level; I would figure to passively pad this down, if needed, to match the amp input needs, while retaining full DAC bit range. One other thing, too: the MiniDSP I run, as well as the OpenDRC-DA8 have a master volume control that moves all outputs up and down together, from their software configured levels. This is the main reason (followed closely by the analog output quality issues) I did not go with the '2496: this, once modded, can do what you seek, but will get very expensive along the way, and as I recall, only does 3 channels, stereo. Point is, you can play around with your arrangement very economically this way, and decide if you want to dump more into the matter. Get a good mic and some measurement software and prepare for some work. Once dialed in, though, I don't think you will view the world the same way again.
  6. To SWL's comment about having done the biamp with solid state bottom and tube top and the long and storied road- been, there, done that, too and I can agree with a lot of your sentiment. But, I have to say, keeping at it can bring its rewards. I use a SET into an Altec 288 on an old school 1st gen EV CD horn, and a fat mosfet amp for the bass horn, and I really never got a satisfactory result (had been using a Rane AC23) until I went digital on the crossover, and got those niggling hum problems with the tube amp sorted. The digital crossover move enabled time alignment, which, along with the CD horns, brought the image sharply into focus, and also enabled me to sidestep another shortcoming, that of the upper end bass horn response. I use the Le Cleach approach, and cross the bottom at 300 Hz. That woodiness at the top end of the bass horn is largely gone. I would NEVER go back to the original having reached the point of having this dialed in. Before getting it dialed in...sure, I kept those type A's close at hand, as I looked into the mirror asking myself if I really was all that smart to begin with. But, this is a pretty complicated system to run, now, as it must be carefully power sequenced on and off. And I recently made the jump to a full digital front end, using an RPi2 running the full digital HiFiBerry Digi into the MiniDSP, delaying analog until hitting those amps. This is pretty nice, but again, more complicated to operate than simply walking up the stereo and pushing some buttons. On the whole, though, moving smartly in the right direction. Don't discount what can be done with the biamp, just recognize there's going to be some fooling about (a lot) to get it right.
  7. Having just done this on my set of Khorns, I can add to the positives of doing this. My particular living room space has a great many windows and some of these are floor to ceiling panels that swing out sideways. Getting the bass horn to seal to the corner and dealing with the sills of the windows was impossible. Enclosing the rear solved this. More to the point, the enclosing of the rear/sides caused the response to smooth out considerably. This is a very large room, and so I don't have quite the same standing wave problems others have encountered, but the poor sealing caused quite a bit of sharpness. Now I should also mention that I just finished opening the throats to around 6x13, and switched to woofers with much stronger motor strength (about 2-3 dB greater sensitivity, determined by outdoors measurements). I like the result of these changes quite a bit. Right now, I am working out the kinks of running a Raspberry pi server (Volumio) that uses a Hifiberry Digi+ TOSlink and SPDIF digital output. I use this to drive the digital input of a MiniDSP crossover that is used to biamp this rig. It is a pretty remarkable combination, and has been liberating in terms of music source and overall quality (noise floor has dropped down even further). But, to the point of this thread: yes! enclose the backs. Biggest downside is you will lose easy access to the woofer door on the bin, but it is not impossible.
  8. Chris: Great tip on the use of the SPL + Phase feature of REW! I use a miniDSP (since 2011) and use a delay for the Altec 288. I have not fine tuned this, and intend to, all the more since you have pointed out the REW feature. There is a bit of a delay modification, too, for the Le Cleach crossover topology I am using as well. But the time alignment is crucial if you want these all horn systems to image. Getting a handle on directivity is also a part of this, hence my interest in the 1st gen EV family that started it all. Right now, I just run this as a two-way, the 288 reaching out to around 14-15 KHz. Probably good enough for my ears at my age (!) I might play around with doing a three way, but will need to go to another crossover product for this, as my miniDSP only does two way for my needs. I may just push ahead and do the recent DA8 box, because this will get me up to 4 way, uses a Sharc processor, and runs 96 KHz with the plugin I would need. Has deeper delay adjustability, too, relative to my miniDSP. My basic interest and direction on all this is to take a classic, time-honored design, return it to its purest form, taking advantage of the superior CD horn technology, the improved drivers of today, and the very high quality amplifiers and digital crossovers now available, at a reasonable cost permitting biamp/triamp.quadamp setups. The crossover advances on the digital front go a very long way in addressing many of the shortcomings, as they can do the CD horn emphasis, correct for time alignment and enable one to pick drivers without much regard to their impedance characteristics. And the better ones do room correction, too. What's not to like? Taken together, these bring a Klipschorn system tightly into focus, and deliver a level of performance that is formidable by today's standard. This is why I have been messing around with getting the stronger driver in there, and opening the throat up to near the original design, and addressing the principal sore spot of response beyond 300 Hz by sidestepping it altogether. -M
  9. Chris: Thanks for the tips- I greatly appreciate this, as I have spent quite a bit of time on measurements as well (in room though, while these present measurements are all outdoors), prior to this current exercise, and came to the conclusion that I could not necessarily depend on these in an absolute sense, but rather, could use them for relative effects upon making changes to this system. Maybe a bit more than that, but really, the emphasis for me was on relative change. Because of this, I have tended to use my ear for absolute purposes: if it measures poorly but sounds good, I tend to de emphasize the absolute nature of the measurement, in other words. Same if it measures great but sounds awful. I must make some additional measurements before I post all of this, but I will also be picking up a better calibrated microphone as well, because I want to reliably measure north of 5-8 KHz and see how this system is behaving on the top end (e.g., after re-integrating the bass horns with the Altec 288 + EV HR6040 CD Keele-type top hat. I am using Le Cleach crossover parameters, and crossing the bass horn out at just over 300 Hz. The early take away is this: The Legend CB158 measures about +3dB stronger in response pretty much throughout the measured range, with the K33E showing to advantage by about +3dB in the 350-500 Hz range (kind of as expected, since this was the reason for the 3x13 slot change in the early 60's). This was pretty much what I was expecting by going to a driver with greater motor strength and sensitivity, and moving the throat slot to 5.5x13. I also saw this response steadily improve with repeated measurement evidently betraying breaking in of the suspension. First sweep was almost nearly on top of the K33E response recorded immediately before changing the woofer and motorboard. But by the 4th or 5th measurement pass (doing 2 sweeps per measurement), the response stabilized to what I described above. I am not too concerned about response much above 300-350 Hz, as I am not trying to push this horn beyond that point anyway, and my desire was to take advantage of a higher strength, more sensitive driver and see how this performs. Vb resonant point with the CB158 was up 1 or 2 Hz over the K33E, but I did not go back and measure this again after breaking in; I suspect it may have dropped back down 1 or 2 Hz. I say this because of the steadily improved bottom end with repeated sweeps. To me this suggests that the suspension is loosening up to its operational design point and settling in. And, this driver has a published Fs of about the same number as the K33E, so I expected it to be similar to the K33E Vb resonance. Both (K33E and CB158) are resonating around 41-42 Hz by the way. Mike
  10. Both these posts were very useful. Turned out that microphone placement was the problem. Measurements were being done outdoors, and so reflective structures were some distance and sparse in number, and size. I do not have an internal microphone on the laptop, so this was purely the external mic. I did not get the distortion plot (I will have to look to see if this information is somehow saved with the sweep). These are upsweeps. When I place the mic on the ground about 4 feet from the bass bins the responses looked much more normal and could be qualitatively and quantitatively (e.g., peaks/frequencies could be matched up) compared to curves I have collected for klipschorn responses. I have not finished this work, but when I do, I will post it and will look forward to your feedback! Thanks, Mike
  11. I am making measurements on my Khorn bass bins after having made some mods, and these measurements are being done outdoors, as I have brought the bins to the garage for the mod work, and bring them out into my yard for measurement. Only one audible mod, here, in these measurements: I enclosed the sides with 'wings' similar to the last production model Khorns. These are Speakerlab builds. I have opened the throats from 3x13 to 5.5x13, but right now am running the 3x13 motorboards with K33Es. So, I don't think throat issues are in play here. I have used REW in the past, in my home listening room for measurements, and frankly, room resonances have always made this pesky, and this is why I wanted to make the measurements outdoors. I have also measured the resonant frequencies of both bins, and these measure right around 42-43 Hz, which was a bit of a surprise for the K33E's. I can detect evidence of what is likely sealing issues with one of the bins, and you can see this in the slightly different frequency responses as well (probably). I have, in order to get decent signal to noise, run the sound levels up quite a bit, and I believe I am in a workable sensitivity range; levels are good, not clipping. I am sure my neighbors are wondering what the hell I am doing, as I sweep those bins.... My question is, I see really interesting bass performance in these measurements: have a look at the response curves for each bin in the attachment. They show an unexpected behavior in the 20-40 Hz range. And I can't really explain that too well. I can tell you that I (surprisingly) hear output from these bins in the mid 20's of Hz, and it really gets strong by about 35-37 Hz, and proceeds along. I can clearly see the mic picking up output when the bins are excited at the beginning of the sweep, and I can hear output as well. So it seems to be there. I just expected a rolling off starting around 38-42 Hz, and just the opposite is happening (and I don't think it is real, in spite of hearing output). For those who've made these measurements in the past on their bins or on other systems, how do these look to you? I am not sure I trust the numbers under 35 Hz. Microphone is a Radio Shack analog meter (the later model), REW correction file applied, Behringer UAC 202 ADC/DAC, calibrated in REW. Serviceable equipment for what I am doing, but clearly not lab quality gear. I will be undertaking a similar measurement upon fitting of the CB158 loaded 6x13 motorboards, including measuring the resonant frequencies of the bins. Probably should break those in a bit before making the runs, but we'll see. I plan on uploading a full summary of the measurements for inspection and comment when these are completed. -M
  12. For those interested, I have proceeded to open the throats of my bins to approximately 6x13 (5.5x13 net, done purposefully). I have also prepared two more motorboards and fitted these with Eminence Legend CB158's. The motorboards are cut for 6x13. In the next several days, weather permitting, I will be making two types of measurements on these, the first will be establishing the resonant frequency for each bin/driver combination. The second type will be to establish the frequency response. For this, I will be making the measurements outdoors, and will be using REW and a voltmeter measuring across a resistor on the + speaker terminal. Depending on how these measurements go, I may or may not add a set of Kappa 15C's into the mix. The two configurations being compared are: K33E on 3x13 throats, and CB158's on 5.5-6 x 13 throats.
  13. Boom3: Thanks for the precise rendering of this quote. I will have to look in my literature collection on horns to see if I have this paper. If you have a pdf, I would be grateful. The Plach and Williams paper linked to earlier in this thread was not the one I thought it was- it references the original, classic work, though. I found that linked to paper quite interesting and helpful. Spent much of this weekend cleaning up the bass horns, fabricating 'wings' to partially close up the sides of the horns (like the last production models of the OEM Klipschorn) and opening the throats, preparing new motor boards. I hope to get some measurements with REW somewhere along the way- probably outdoors measurements, as these are in my garage at present. Right now, I am deliberating on which woofer to choose: Kappa 15C or Legend CB158. I like the lower Fs of the Kappa C (31 Hz), but I really like the strong output of the CB15. Keele modeling shows the Kappa to require the smaller throat and Vb, and both bracket the model for an EV 15WK. The CB15 seems closer to the K33E round magnet St and Vb, too, and shares a similar Fs (34, vs 34.5 or so). I know many have found good results for the Kappa 15C in the LaScala and in vented box designs. I have seen reference to exactly one lister who's used the CB15 in a bass horn with essentially the same parameters as the Khorn (throat is 6x13, but flare is 38 Hz, same corner design, slightly different folding), and really liked this. I am using a biamped setup with a miniDSP (since 2011), and so I have no concerns regarding differences in sensitivity of the bass horn vs. the top end- I will dial it in as needed. Anyone have any advice on the woofer choice? I suppose I could buy one of each and try both, too.
  14. The advice to look at Edgar's Show horn sparked me to re-read that article. It is an excellent article as it covers most of the design issues one encounters with folded bass horns in real listening environments (rather than a recapitulation of the infinite horn cases). He mentions that in actual testing, he had to double the Vb in his design (according to Leach's formulas) in order to get it to resonate at the desired design frequency. This is interesting to me, because when I run the Keele calculations for St, Vb and mass rolloff, they match pretty well to the Leach counterparts EXCEPT for the Vb. Leach gives about half of the Keele values. I remember running into this when I did a LaScala-like design in the early 80's, and I never could resolve the reason, until, that is, I re-read that Edgar article. Message: believe the Keele numbers, at least as regards Vb. Another interesting part of that article is the very practical guidance on setting the Vb experimentally. But you need to have a pretty good guess to begin with, because if you build it too small, you are out of luck, as it is really difficult, in most horn designs, to increase Vb. As an example of this issue, run the driver case shown in the Leach article through Keele's equations, and you will see what I mean. Edgar evidently thought the difference had to do with Leach's equations being set for infinite horns. The Khorn, though, defies much of what we try to do, with the design equations, it seems. We are constantly told, for bass horns, go with drivers that have low Qt and/or Qes and high Fs, to get that mass rolloff as high as possible. And yet, the drivers that PWK chose seemed to go the other way on Fs, trying very hard in the 1950's to get the Fs numbers down by almost any means possible, and the Qes and Qt values, well, it is evident from the T/S parameter sets on the K33E that drivers ranging from 0.28 to 0.68 in Qes have been used by the factory. In the same design. With only a throat size change. So what's a good driver, then for these applications? I guess it keeps coming down to high motor strength, principally. But there are evidently other factors, because, as a practical example, I have tried an EV15L in a 3x13 slot Khorn, and it just did not do what I expected, nor was its performance remotely acceptable to me. A K33E on the other hand, seemed to do very nicely by comparison. But I am really interested in opening that slot to 6x13 like the early models, and running a driver with very high strength motor in there, and seeing what I get. On the University Classics that I built, I am running a driver that by all estimates according to theory should provide excellent performance in this design, and I am not at all happy with the result. This is a driver that has parameters not all that different from a K33. But I think a high strength motor is needed here, too. We shall see. I am focusing first on the Khorn, hoping to take this design to its roots by going to a 6x13 slot and a strong driver, but with a lower Fs than typical of the 1950's. The fallback is the venerable K33E. Then I will move to the Classic and see what can be done there.
  15. boom3: The comment you paraphrased from PWK has the answer I was seeking: annul a little higher so that Vb keeps control over the woofer. In other words, always have enough compliance in the box volume to maintain control. For those who've offered the papers by Plach and Williams (the classic reference) and the paper by Leach (another take on horn design with T/S driver parameters), thanks! I am aware of these, having collected my copies some 25-30 years ago, now (and that includes the reading of them ;-). While I write a lot of software for the work I do, I am not so much a fan of using design codes that I cannot inspect, so I don't use hornresp or any of the other codes. I guess that makes me old school, but there it is. The SpeakerBuilder article that boom3 mentioned I also have, got the original issue from when it came during the days when SB still published. That is the 'show horn' as I recall, and it is loosely based on the University Classic, but last I looked at this article, while Edgar mentions the Classic, he does not do any reverse engineering of it, other than to use it to suggest how he approached his own design (primarily with regard to folding choice). I want to recall that the Edgar design was a 50 Hz flare, though. All from memory, so don't quote me. The reason I am asking the question is, when working with an established design like the Classic or the Khorn, you can't do too much (esp. if you have the cabinets already, as I do) to enlarge the volume. You can take it down some, though, but this means you must choose woofers for which you have a reasonable chance of reaching the Vb. Most of the 15" drivers I am looking at require somewhat larger volumes, a few have smaller Vb's, and so it's a push. I am just trying to figure out the likely audible effects of going too larger or too small, and choosing the lesser of the evils. It looks like choosing a driver that has a predicted Vb that is equal to or a bit larger than the available Vb is the way to go, if I am thinking about the Klipsch quote correctly. I suppose one answer lies in the analysis I've done on the EV 15WK (1950's khorn) and the variants of the K33E (square and round): the old EV15 WK models at 84 liters for Vb, whereas the K33E models 210 (square) and 128 liters, respectively, for a 38 Hz Fc horn. These K33E numbers would suggest a sloppy cone down low, but it may be that the small throat is keeping it in line, I don't know. There's a lot about that Khorn design that seems to defy attempts to model it in any rational way. But beyond that, there've been quite a few woofers used in that horn, and within a certain range of parameters, they evidently all see to work. I am looking closely at a Kappa C because it is so very close to the target numbers, close to the EV 15WK, and within a few percent of an EV 15L. All these need the large slot throat of the 1950's khorn, and would seem to match well to the Classic, which has the 6x13 throat like the 1950's Khorn. I was first looking at the CB15, because it has a higher BL motor, but CB15 numbers just don't dial in as nicely as those for the Kappa C. I know another prominent member of this list uses a CB15 in his Khorn with a 6x13 throat and is very pleased, waxing rhapsodic about the thwack that it has. That is what I am going for- the in your face punch that an A7 has. Thanks for all your well reasoned and studied responses! I knew I could rely on this site-
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