Al K. done good, REAL GOOD

[D-MAN]

No, not a Khorn bass bin, it's a DIY bass horn - entirely different. More like a Jubilee than a Khorn, but different from either!

DM

[tigerwoodKhorns]

So, if I kept my K Horn bass bins and built an ESN 400 and used it with a modified tracthorn and the 4591's, would that be my best setup?

Chris

[D-MAN]

You may do fine with an type-A upgrade vs. an ESN, although I really like the ESN. My design really required an ESN, where the Khorn doesn't, of course. The BMS is rated to 300Hz (at 150 watts!).

However, I recommend the ESN over the first-order crossover types, of course.

{edit} I forgot to mention that you should check with Al K. - he has some inside dope on the BMS driver, so he would be the one to ask about whether the midrange portion has some issues with a standard crossover setup. Mine has the tweeter built-in, so I know that presented a different demand on the crossover design.

DM

[tigerwoodKhorns]

So you are saying the BMS driver and tracthorn is superior to using baby cheeks and a mid driver (BMS or otherwwise) and an ESN 5800?

Chris

[D-MAN]

Well, a couple of things: 1) I do not have a tracthorn (yet), 2) superiority requires further definition.

First, I have gone through all the permutations that you suggest. K33E on a ES600T/5800 to a JBL 2404H and a 2" throat Selenium driver.

I do know that the BMS 4590 (coax) is just-as-good-if-not-better than the JBL2404H and the Selenium D305 on the same 2" throat horn. But there are differences, and that is where the term "superior" becomes a little "iffy"...

The BMS has better imaging, a larger soundstage in every direction and is much more dynamic overall. However, at the settings I prefer, the tweeter is not quite equal to the output of the JBL - mainly it is a propogation characteristic. But I'll live with it; overall, the imaging capability more than makes up for it.

Getting a seamless blend is a bit touchier with the single horn vs. the mutliple horns (i.e., the JBL 2404H), but the benefits of an incredible soundstage is the reward. Horn splay angles and dispersion patterns come into play and take alot of fussing-with. This would absolutely mean that it is not going to be a particularily good choice for a fixed top cabinet with a baffled horn mount.

My personal taste is that the BMS 4590 is the better lashup, but it has some very particular setup issues that need to be taken into account, like a custom-made crossover, and a free-standing horn mount (unbaffled).

DM

[Al Klappenberger]

Chris,

Several points:

* The Alteck 811B and 511B both have 1.0 In throats.
* My ES-400T should operate ok with any driver including the BMS.
* I would really recommend changing out the horn FIRST before changing drivers. The K55 isn't the best thing in the world, but it's better than the K400 horn it on!

Al K.

[tigerwoodKhorns]

I don't think that baffling is a problem with my K Horns. Look at my Avitar. I have false corners (with grills) so that I can point my K Horns any way I like.

When you say the tweeter is not quite equal to the output of the JBL what do you mean? I see that you feel the BMS has better imaging.

Chris

[D-MAN]

The output of the JBL tweeter is wider in angle (100x100deg) vs. the (at best) 90x40 in the mid horn (BMS coax). This has quite an effect at the listening position and with related room treatments. I think it is entirely a dispersion issue, not that the BMS lacks frequency response. However, if too loud of setting on the BMS tweeter is used, the tweeter moves the soundstage forward or becomes more strident, more than I like. However, the difference in high-frequency "loudness" is that the JBL 2404H can be effectively louder and not effect the soundstage detrimentally.

The differences are what one would expect from using different horns.

If you are specifically NOT thinking of using the BMS coax version, you will be fine.

DM

[D-MAN]

Look at my Avitar. I have false corners (with grills) so that I can point my K Horns any way I like.

Chris

I thought that was a Jubilee!

DM

[tigerwoodKhorns]

Nope, a K Horn with false corners.

You have me confused. Which setup will yield better results. The BMS 4590 or 4591 with the JBL tweeters (all using esn's)?

Chris

[D-MAN]

The BMS 4590 has a coax tweeter - do not get that if you intend on using the JBL 2404H. The 4590 will require a new crossover.

The BMS 4591 is the midrange driver only; that would work for you on a 2" throat horn. Using this, you won't need to change the crossover! However, I feel that it might be compromised in that it costs alot and doesn't have the tweeter section (i.e., it has a hole in the center). Perhaps a dedicated driver would be in order for the money, I don't know. The 4591 does have extreme power-handling capabilities, though. But perhaps this is a question that I really cannot answer.

You already know which one I prefer, and I haven't heard the 4591. However, if you wait long enough, I might get a pair, I have to replace the Seleniums (for another pair of speakers) with something else anyway...

DM

[tigerwoodKhorns]

D Man,

I did some reading on teh 4590's last night.

You may have already answered this - are you using an external x-over for the mid/tweeter or the built in x-over?

Thanks.

[D-MAN]

I had Al K. make a custom external with an attenuator on it for the tweeter.

DM

[D-MAN]

3+ WEEK REVIEW

===============

(more incessant rambling on a subject close to my heart and even closer to my wallet)

A new question has come up... but let me preface it with the following:

I'm running a high-current SS amp and am using cd's as source material, which would automatically tend to make the response pretty dynamically "variable", to say the least. Couple that to the new lashup, and now I've got dynamics in spades.

The question is: Is there such a thing as too much dynamism? Not that I think that my lashup is too dynamic, but let me put it this way: I would not want any more. That is to say that now that I have it, can I live without it? No, but I don't want any more. This is enough...

Basically, I am talking about what I would call WHACK. Especially from percussion, especially drums of all types. This is an element that I think we tend to accept the ordinary lack-luster response and when it becomes extraordinary, it really makes us sit up and take notice. Well, that's where I'm at now, the drums and how they are engineered on the recording is very clearly revealed, and if that happens to be in-your-face, that's exactly where it ends up! Realistic to a degree that I have never experienced before. For demo purposes, I intend to use a track that expressly promotes percussion as the first eye-opener in the series.

The determining factor of the overall voicing, dynamics, and frequency response is drums IMO. If your system is doing drums (i.e., all things percussive) right, it is highly likely that it is doing everything else right, too. Snare drum rim-shots, cymbals, gongs, triangles, wood blocks, bells, bass drums, etc. If the drum kit sounds REAL, then the rest (vocalist, instruments, bass, etc.) will sound real too. It's sort of automatic.

However, I would say that the overall dynamism of the system is going to be the first thing noticed by other people. This is a well-known attribute of horn-loaded speakers, but I honestly have not heard a folded bass horn do it quite as well as this!

How can you have realistic WHACK and NO TIME-LAG?

============================================

The answer is, I don't really know, except there seems to be a combination of things at work.

Evidently, the ESN crossover prevents it from being noticable, although I also think that the particular woofer has a great deal to do with it, too. The same ES slope was used on the K33E in the previous lashup, but the new driver seems to be quicker and more timely as part of its capabilities.

I feel that the new driver is simply more efficient, and that increases its dynamic capability (i.e., it is physically faster in response time) and THAT in turn gives it a sense of being "quicker". You CAN hear the difference! Why should that be the case, the horn length is still slightly over 5 feet overall, let alone the exit splay angles which will also add transit time to the listening position? But believe me - YOU WON'T hear any recognizable time-lag artifacts! No kidding.

Dynamism is apparently the direct result of efficiency, and therefore, since WHACK has gone up, it figures that the overall efficiency went up in order to accomplish that. The fact that these do not seem to overload the room until excessive (i.e., more than 100watts) is an indication that the frequency response is likely smoother overall than the previous lashup incarnation using the K33E. The response stays clean and clear (although extremely loud) at high volume, where the previous incarnation became what I consider unlistenable above 1 watt per channel or so. Same room, same horn, same gear, same source material, different drivers (I blame the K33E). It has to do with the power bandwidth(s) of the drivers IMO.

Same WHACK as WHAT?

=====================

In comparison to any other speakers that I have ever heard, I'd have to say that these sound closest to what I remember Altec A7 VOT's (I borrowed a pair years ago) sounded like. I'd guess about the same amount of WHACK between the two, although I am convinced that the corner horns in their present configuration have a wider overall response and produce a more homogenous soundstage presentation.

Certainly they beat the A7's on appearance, footprint size and placement criteria (none of these being a "fault" of the A7). That's as far as I'll go with that because I'm drawing these comparisons from memory. Since I've never heard a Jubilee, I would imagine that it's something clearly related to what a Jubilee sounds like, but that is just an estimated guess, based on the designs.

I'm convinced that I've got a winning configuration at a reasonable investment by my standards anyway.

DM

[D-MAN]

4 weeks review

============

I have some thoughts on SPL and room overload. As I stated before, the new woofers now make for extremely loud without overloading the room, where the K33E would **** it out above 1 watt per channel. My theory is that the woofer/horn bandpass is more "balanced" than with the K33E in the same horn. This makes sense in that I previously decided that the K33E is balanced towards the extreme low-end and falls off rapidly above 350Hz or so. The CB15 is balanced towards the mid-and-upper bass frequency corner. This is all apparent when one runs the numbers on the drivers and the horns in question using Keele's T/S horn formulas.

The K33E results are upper corner (Fhc): 177 Hz, Low (Flc): 6.1.

The CB15 results are upper corner (Fhc): 226.6 Hz, Low (Flc): 5.1.

The K33E is theoretically reactance annulled at 5 cu. ft. of Vb, and the CB15 at 5.8 cu. ft. Note that neither is fully annulled in either the Khorn nor my horn, which is based at least in part on the Khorn parameters.

Judging by the above upper and lower frequency corner results, one would assume that the low frequency response of the two drivers would be somewhat equivelent to each other, but I find that to not be the case. I am satisfied with the low end response though, but the K33E is definitely more balanced towards the extreme low end, and is seemingly more efficient with the extreme lows. It lacks in the mid-bass as can be seen in the results above. But the low frequency differences is not as numerically apparent from the above results...

This could be that the LF response could be further annulled by the addition of absorptive material into the back chamber of my horns, although the calculated differences are about 1 gallon more volume as it sits, and this puts me at the typical varaince between the theoretical volume and actual volumes preferred by PWK (upto 20% difference). This tend to raise the Fs by a few cycles, though. I could conceivably recover those with a little fiberglass in the back chamber, it would seem. Just haven't done the fine tuning yet.

The theoretical throat size for maximum efficiency is 115 sq. in. for the K33E (surprise!), and 75 sq. in. for the CB15 which is a perfect match to the max-sized Khorn throat opening as well as my design (78 sq. in max).

The sensitivity was guestimated by me at being 96+ db at low frequencies, but you cannot rely on manufacturers ratings on sensitivity as it is very frequency dependent and they usually don't specify (or rate below 200Hz!).

So I got to thinking about frequency curves and power bandpasses in drivers and come up with this...

Here are the curves for the CB15 woofers as specified by the manufacturer and the end result in a hands-on test specific to the bass horn. There is quite a bit of difference between the testing, as you can see.

I've added boxes in the graphs to relate them to the K33E graphs that follow in the next post...

DM

[D-MAN]

K33E comparisons from published sources with the same area highlighted (200-400Hz) as tested in a Klipschorn. The Jubilee paper curve was made out-of-doors, and the Audio Magazine curve was measured indoors, as was the Edgar measurement. Even so, these all look unrelated, don't they?

Black art or science? A bit of both maybe.

DM

[D-MAN]

Here is the P-Audio 4525 midrange horn frequency curve as published by the manufacturer (probably a plane-wave source was used for a driver, somewhat typical of horn freq. tests).

As you can see, the response of the horn tends to be the controlling factor, and we can extrapolate that the same occurs in all horns, including the folded bass variety. The general shape of the horn response is closely followed by the following response using the BMS 4590 coax driver.

I find it particularily striking how it so closely follows the lower trace of the manufacturers plot in overall pattern...

In essence, it boils down to the horn itself, and although the horn driver is an important consideration, it will never be any better than the horn it is placed in...

DM

[D-MAN]

This is the published response of the BMS 4590 coax driver (plane-wave).

This is a very nice looking response.

The previous attachment shows how the response follows the capabilities and limitations of the horn it is placed in...

DM

[D-MAN]

One VERY IMPORTANT thing to note is that MY CUSTOM ESN's

do not have fuses in the signal path!

This was like pulling teeth getting Al K. to leave them out, but I managed (FINALLY!). He will undoubtably put up quite a fuss here, too, should he see this post. But HEY - I'm the customer, and I'm ALWAYS RIGHT!

Remember this PWK (dope from hope extract):

(particularily the last paragraph)!

[Al Klappenberger]

Dana,

That fuse thing reminds me of General Motors comments about seat belts back in 1960!

BTW: I'm building your networks now but I don't have the transformers yet so there's a blank spot on the board where they go. There's a blank spot where the fuse belongs too!

Al K.