"V-Trac" Midrange Horn Upgrade For Khorns

[Guest " "]

k-55 on the left

k-69 in the middle

k-1133/32 on the right

[thefluffy]

That k-69 sure is pretty.

I can't afford Al's Trachorn.... let alone a 2" Throat Trachorn + a 2" driver. [:'(]

But, I sure would love to hear the combo!

Daniel

[greg928gts]

I spent a couple of hours today testing (by ear) the BMS 4592ND-MID driver versus the BMS 4591. This was in my living room with my fully upgraded Khorns.

Per pair, the 4592 drivers cost $967 with shipping, and the 4591 drivers cost $709 with shipping.

The 4592 drivers have a neodymium magnet and the 4591 have the much heavier ceramic magnet. As far as I know, both use the same diaphram.

I was told the 4592's would sound better, and they do cost more, so it's hard to get that out of your mind as you're trying to do an objective analysis of each.

Very little difference between the two in this application (V-Trac horns). I give a slight nod to the 4592's in overall clarity, and just a little warmer sounding, but we're splitting hairs here. They both sound great. So if you wanted to save a few bucks, go with the 4591's, I don't think you're giving up much of anything really.

Greg

[greg928gts]

That was my intent from the begining, to change the proportion of what I was hearing from 1" throat metal horn (K400) to modern, high-quality 2" driver (BMS 4592), and it worked perfectly.

Just to expand on this a little. During my testing today, as I switched from the 4592 to the 4591 drivers, I decided to try the BMS 4592 driver just sitting on top of the Khorn with no horn at all, just the motorboard attached to it. This is really changing the proportion of the driver to horn! All driver, no horn.

The sound was different for sure, but not like you would expect. The overall sound was basically the same as when the driver was attached to the horn, only not focused or directed into the room the same way. The imaging went away, and you could hear how the mids were coming from each side distinctly. I had to boost the mids up 5db, and they might have been just a bit hotter than before when they were on the horns, so the horns are amplifying the mids by about 4 to 5 db on their own. Not much if you ask me. Which is good! Once I boosted the mids up and sat down to listen again, other than the focus and imaging being different, the sound of the midrange was almost the same as when the driver was in the horn. Again, this is good! That means the horn is having little affect on the sound of the mids, which is something that was and is a goal for me in designing and building midrange horns.

What do you think it would sound like if you did this with the K55 driver?

Another simple test that I performed yesterday in my shop, was to speak through a K400 horn and then keeping the same tone and volume to my voice, speak through one of the V-Trac horns. You would not believe the difference. Let me say that again, because I'm telling you, most of you here would not believe the difference in sound just talking through each of those horns. You'd shake your heads in disbelief. It would change your total perception of how a midrange horn should be designed and built, and what it should be built out of. I never would have thought there would be such a startling contrast between two horns designed to do the same thing. Usually the differences in anything audio are subtle variations or measured in small increments. Not with this test. They were as far apart from one another as you can imagine. The K400 sounded like a cheap megaphone and the V-Trac horn sounded like my natural voice, with just a touch of the highs and lows taken away. My nephew and a friend were there, and they couldn't believe it either. I plan to keep a K400 and a V-trac handy in my shop just for demonstration purposes.

So what do I take from all of this? A few things. First, it's a good thing to have a bigger, higher quality midrange driver that is working effortlessly to produce sound. Second, that a large-format, wooden horn sounds much better than a small-throat, relatively long metal horn. Third, a midrange driver/horn combination that has more sound coming from the driver and less affect from the horn is much better sounding than the other way around. Fourth, this is proof that there is a lot more to be done with the design and construction of horn-loaded loudspeakers.

Greg

[Crossman]

What width plywood are you using? 14.33 inches of height leaves very little room at the top and bottom of my '74 Khorns for much more than 3/8" plywood and the top and bottom of the horns.

[greg928gts]

What width plywood are you using? 14.33 inches of height leaves very little room at the top and bottom of my '74 Khorns for much more than 3/8" plywood and the top and bottom of the horns.

Sorry, I don't understand your question.

Greg

[Crossman]

Sorry, I don't understand your question.

What thickness of plywood did you use to construct the V-Trac horns?

a. 1/4

b. 3/8

c. 1/2

d. 3/4

e. other

[greg928gts]

The tops and bottoms are 3/4" plywood, the sides are 3/8" plywood.

Greg

[Crossman]

The tops and bottoms are 3/4" plywood, the sides are 3/8" plywood.

The reason I am asking is: If I am reading your chart correctly on the Greg's Tractrix Calculator page of your website, you list the height of the horn as 2" to 9.25". If 9.25" is 9 1/4 inches and add to that 3/4" (or for the top thickness and 3/4" for the bottom thickness (- 1/16 to allow for the actual thickness of 3/4' plywood) then the total height for the flare end of the horn would be 10 3/4".

The space between the upper and lower panels of my horn bin are a tight 9 7/8" , making your horns a non-fit for my '74 Khorns.

[Crossman]

I found this comment in an old thread (Nov 11, 2005) by Al K

"I wouldn't try using my Universal netwrok on the BMS driver. There is too may difference between what that network was designed for and what the load presented by the BMS drivers would present. The impedance of the tweeter section of the BMS is 13.5 Ohms in parallel with 0.44 mHy. And the tweeter must be attenuated, not the squawker section. It's a bad idea.

The network I built to operate the two sections of the BMS was at 6000 Hz and is 2nd order on both filters. This provides a different insertion phase then my Universal which is 2nd and 3rd order. It will have 90 degrees more phse shift. It's total guess work how it would act on that driver!

Al K"

He was referring to a BMS 4590. The only major difference between the 4590 and the 4592 is ceramic vs neodymium magnets. Does Al K still feel this way?

[greg928gts]

The tops and bottoms are 3/4" plywood, the sides are 3/8" plywood.

The reason I am asking is: If I am reading your chart correctly on the Greg's Tractrix Calculator page of your website, you list the height of the horn as 2" to 9.25". If 9.25" is 9 1/4 inches and add to that 3/4" (or for the top thickness and 3/4" for the bottom thickness (- 1/16 to allow for the actual thickness of 3/4' plywood) then the total height for the flare end of the horn would be 10 3/4".

The space between the upper and lower panels of my horn bin are a tight 9 7/8" , making your horns a non-fit for my '74 Khorns.

Ah, I see. Yes, it would seem that way, but the edges are shaped/cut so that the full thickness of the tops and bottoms don't come right out to the edge. I wanted to maximize the amount of horn mouth height, which is why everything is so tight. But it works! They will fit in your 1974 Khorns. They are an exact replica of size of the original grill frames, I guarantee they will fit. My Khorns are no different than yours (1981) and mine slid in snug and tight. Along with the V-Trac kit, I include a variety of "felts" to help shim the horns in the tophat, and to protect the wood from any damage from staples or just the glue that I use to glue the edges of the cloth.

Greg

[greg928gts]

He was referring to a BMS 4590. The only major difference between the 4590 and the 4592 is ceramic vs neodymium magnets. Does Al K still feel this way?

Apparently not, since I've had at least 25 emails with him about it. He does have one tiny suggestion for the swamping resistor, I think he said, but it's such a minor change that it's not going to make any audible difference in the system. Maybe he'll chime in here and clear up what he meant by the quote above.

Besides, my ears tell me all I need to know! I wish you could see/hear my system Crossman, that would erase any doubts you had immediately.

But keep the questions coming, others probably have similar questions but just aren't asking.

Greg

[Deang]

Greg, I'm confused -- I thought you were using the 4591 and the Beyma. The 4590 and 4592 are both coaxials -- they have built in tweeters. Al is indeed speaking of the 4590 -- he designed a network for Dana (DMan), who was using the 4590 in one of his DIY efforts.

[gaspr]

Here is a link to the 4592-Mid driver...

[Deang]

Man, they should have given that thing a different model number. So now they have a 4592ND (coax) and a 4592ND-Mid.

http://bmspro.com/Compression-Drivers.bms_compression_drivers.0.html

[greg928gts]

Man, they should have given that thing a different model number. So now they have a 4592ND (coax) and a 4592ND-Mid.

http://bmspro.com/Compression-Drivers.bms_compression_drivers.0.html

I'm using a 4592ND-MID which is midrange only.

I've heard the coax in a Bentwood horn and didn't like it nearly as much as with a separate tweeter. Which I was able to try within seconds on the same system (JBL 2404 I think that's the model). The separate tweeter sounded much better to my ears. I've always liked three way, it's taking a bit for me to get used to two way designs, but I'm working on it.

Greg

[khorn#1]

Greg,

Not to take any business from you but, your v-trac horn is very close in every way to Al's trachorn. I am strictly going by look of both designs. I have not taken any measurements.

I have Al's trachorns installed in my khorns along with his es - networks and crites tweeters. I was wondering if with a little modification the trachorns could be setup to take the two inch BMS drivers. Im concerned that the voicing of the trachorn would change in a negative way if this mod was tried but if it would work, trachorn owners could possible convert to two inch mid drivers.

I've never heard khorns with two inch mid drivers or any other driver except the k-55 for that matter. I know what the trachorn did for me over the stock horn and as you have heard the two inch driver is another very positive step in the khorn upgrade. One I am very interested in.

Thanks,

Randy

[jwc]

Not to take any business from you but, your v-trac horn is very close in every way to Al's trachorn. I am strictly going by look of both designs. I have not taken any measurements.

That isn't the case at all. This is not a Trachorn that was cut short to accomidate a larger driver. This horn has a larger mouth and thus a calculated lower cutoff Fc. The Trachorn is "like" this horn in that it is tractrix, a midhorn, and built "Edgar style". Greg wanted a Big tractrix midhorn that would fit w/in a Khorn top hat. He started with what the "maximum size" the mouth should be and thought went into horn length restrictions.

This is not to say you can't cutoff a trachorn to accomidate a 2" driver though.

jc

[greg928gts]

Greg,

Not to take any business from you but, your v-trac horn is very close in every way to Al's trachorn. I am strictly going by look of both designs. I have not taken any measurements.

I have Al's trachorns installed in my khorns along with his es - networks and crites tweeters. I was wondering if with a little modification the trachorns could be setup to take the two inch BMS drivers. Im concerned that the voicing of the trachorn would change in a negative way if this mod was tried but if it would work, trachorn owners could possible convert to two inch mid drivers.

I've never heard khorns with two inch mid drivers or any other driver except the k-55 for that matter. I know what the trachorn did for me over the stock horn and as you have heard the two inch driver is another very positive step in the khorn upgrade. One I am very interested in.

Thanks,

Randy

What business? LOL

Modifications that included some kind of adapter attached to the ALK Trachorn to accept a 2" driver would not work. Cutting the throat off the ALK Trachorn and then mounting a motorboard for a 2" driver might work, but technically the horn design will not be correct.

Keep an eye on this thread in the next week or two, I will be offering a "demo" kit for Khorn owners that would like to hear what I'm hearing from my own Khorns. I'm putting together a pair of Khorn tops that can be shipped easily, and they will be loaded with all the best stuff. I'm spending another $2K to do this.

In spite of what some may think, my real interest here is in building better sounding speakers, and sharing the extraordinary improvements I've realized from the 2" horn/driver on my Khorns, it's not to make money. There is no money to be made here really, it takes so much time to make these and promote them, answer emails, answer to this thread, pack the darn things up, etc... $5 an hour is what I figure, but that's only if I sell a couple! If it was about money, I'd be better off getting a part time job at McDonalds.

In the end, even if I don't sell any, it's all still worth it to me. I do take this hobby very seriously, and the improvements I've made to my own Khorns with all these modifications have made any investment that I've made on this project worth every penny. Compared to the money I've spent in the past trying to make my system better, this has been cheap. Maybe I'll end up giving the V-Trac horns away some day!

Greg

[bonsairich]

Greg, is there a possible 2nd choice to these BMS drivers for those of us that would like to go for the 2" driver and horn combo but simply can't afford ( especially now in these economic times) a possible outlay of $3000 to build it yourself. This $ would account for horns, woofers, crossovers, tweeters, and building cabs or purchasing a pair of Khorns which would be even more. The object here is to go with the larger 2" V-trac horns, which you have obviously done your homework on, can you suggest an alternative ( if in fact there is one) for those of us less fortunate?