belle mod question

[edwardre]

Good day! My KHorns are somewhat elderly (pre 1955's) in that they came equipped from Klipsch with the University SAHF mid driver. The mid horns have been swapped out in favor of Altec 511B's. My Belle is a stock '80's era unit. I have collected the components (511 and SAHF) and would like to swap out these in the Belle to more evenly 'match' the KHorns. The 511 horn has the 'flange' type mount while the SAHF, like the K55V has the threaded output.

I managed to come up with two flange to thread adapters. One is pretty much a 'flat mount', that is the threads open up into the flange. The other has about an inch and a quarter long 'tunnel' between the threads and the flange. Since I got the 'tunnel one first, that's what I hooked up on the workbench in the garage for a trial run. Then a few days later, I came across the flush ones and tried them. To my ears, it appears that the 'tunnel' adapter sounds better.

Questions are: Should it or am I 'thinking' myself into circles? Also, the 'tunnel' between the input threads and the output flange is smaller in diameter than the output of the driver and the input on the horn.....like the output of the driver, as is the K55V, is about inch and an eighth. Input to the horn is slightly smaller, perhaps an inch or even 7/8ths. But both the tunnel and the aperture in the flush mount adapter are about 5/8ths. Is that normal or should I bore out whichever adapter I settle upon to 1"?

Thanks!!

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Ed

Fronts: Pre-1955 Klipschorns (slightly modified)

Center: 1984 Klipsch Belle

Sub: Klipsch KSW200

Surrounds: Tannoy PSM6.5's

Receiver: Denon AVR1701

Video: InFocus LP350 DLP front projector

Satellite: DishNetwork 4722 (DD5.1)

DVD: Panasonic A320

S-VHS: Panasonic PV-S7670

LaserDisc: Pioneer CDL-406

CD: Kenwood CD-404 5-Disc Changer

EQ (for CD player only): Furman E151X2

Protection: Furman AV1215 Power Condition/Voltage Reg

[WMcD]

This is interesting to me.

Ed, I'm having a great deal of difficulty with your description of dimensions. Can you draw the cross section of the two adaptors and the cross section of the driver output, and horn input. If a post of a drawing is not possible, perhaps you can set it out in a table form.

I'd aim for a smooth transition overall. It is just difficult to understand the cross sections you describe.

Gil

[djk]

Use the adaptor with the 5/8" entry with the "tunnel".The adaptor without the "tunnel" is made for drivers with a 1" exit.Using an SAHF or K55V without the correct adaptor will cause distortion below 1Khz.Genuine Atlas adaptors have a 5/8" entrance with a "tunnel" that is about 2" long.I have several of these plus some 3/4" entrance about 1" long and some 7/8" entrance about 1/2" long and of course 1" flush.I also have some Atlas dual 5/8" entry with 1" exit for those of you that need 6dB more output.

[Al Klappenberger]

Ed,

Like Gil, I am also confused by all you descriptions and would like to see some drawing if you could. I am also not as firmiliar as djk is with all the adapters that are available, but you might want to take a look at what I did with my Belle Klipsch. It might give you some ideas along the lines of modifying the Belles to match what has be done to the Khorns. Click on the little house icon below the post.

I also tried an adpator to screw a JBL driver into a Klipsch K501 horn (from Belle). Something generated a glitch at about 2300 Hz. I am not really sure it was the adaptor though. All I know is that it was there with 3 different JBL drivers.

Al K.

[edwardre]

Thanks all for the tips.

Gil - Sorry for the cryptic description(s). Essentially, the input to the adapter is threaded to the size of the output of the driver. Then it steps down from that thread diameter to a 5/8 inch diameter tube which is just over an inch in length. Then the tube terminates at a 3" diameter flange which bolts onto the horn input. I'll try and take a few pics tonight and post tomorrow.

DJK - Did I hear you correctly offering an adapter up? What would it take to 'make medicine' on this? Let me know please! I'd like to try a couple more before deciding which is best to use.

Thanks again!

Ed

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Ed

Fronts: Pre-1955 Klipschorns (slightly modified)

Center: 1984 Klipsch Belle

Sub: Klipsch KSW200

Surrounds: Tannoy PSM6.5's

Receiver: Denon AVR1701

Video: InFocus LP350 DLP front projector

Satellite: DishNetwork 4722 (DD5.1)

DVD: Panasonic A320

S-VHS: Panasonic PV-S7670

LaserDisc: Pioneer CDL-406

CD: Kenwood CD-404 5-Disc Changer

EQ (for CD player only): Furman E151X2

Protection: Furman AV1215 Power Condition/Voltage Reg

[Al Klappenberger]

Ed,

OOps.. I goofed! I misunderstood your question completely! Sorry.

I had the K55V drivers mounted to the Altec 511B horns while I was waiting for the JBL drivers. I made a simple adaptor from a piece of 5/8 inch particle board. I just put two holes in it to fit 1/4-20 screws to hold it to the 511 flange and force threaded the K55 into a big hole in the center. I never ran curves, but it sounded fine and it lined up pretty well with the throat for a quick jurey rig! I didn't use it for long though.

Al K.

[WMcD]

Drawing are going to help.

It seems to me that there are a few problems with decriptions.

The real issue is the size of the duct, for lack of a better word. The screw on drivers have a 7/8 inch diameter output. It may be that the horn as a flange connection, but a 1 inch duct. That ain't so bad.

The problem is that there are "adaptors" which mate the 7/8 diameter driver to a 1.3 inch throat on the horn. This is a mismatch unless there is a tunnel to recreate the "flare" of the horn. But that does not seem to be the situation here.

We'll have to see diagrams.

Gil

[Al Klappenberger]

Ed,

Is there going to be a tweeter in your plan for the Belle, or are you trying to used the University driver full-range?

Al K.

[edwardre]

Hi Gil....I did a 'quick draw' to try and better illustrate the situation but my scanner was giving me grief and it was getting late last night so I bagged it. I'll give it another go tonight....thanks for your patience.

I believe that the adapter mates the 7/8 driver output to a 1" throat on the 511, not a 1.3" throat. My question is should this 'mating' occur via a 'duct' that is 5/8" in diameter and 1"in length or should this 'mating' occur more like Al describes with his particle board adapter?

Al - Since I'd be using (for now) the AA network, I had thought to keep things simple and use the SAHF for the mid and the University 4401 mid-T tweeter for the upper stretch. I would also at this time replace the K33V woofer out in favor of a Stephens Trusonic 103LX2. Component wise, this would mirror my (LF & RF)KHorns which came equipped from Hope with these components in the early 1950's. The goal of course being the same as everybody elses....striving for a sonically 'seamless' transition across the front soundstage.

The question mark is the AA network. The KHorns have the K500-5000 net which I understand crosses over at 500Hz and 5KHz. The AA I believe crosses at 400 and 6K? In lieu of over analyzing every possible aspect, my thinking was that I would throw it all together and take some measurements/listening tests and go from there. Could end up being horrendous and I find myself returning the Belle to 'as is' status, which BTW sounds great to me but you know how it is.....got's to tinker.

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Ed

Fronts: Pre-1955 Klipschorns (slightly modified)

Center: 1984 Klipsch Belle

Sub: Klipsch KSW200

Surrounds: Tannoy PSM6.5's

Receiver: Denon AVR1701

Video: InFocus LP350 DLP front projector

Satellite: DishNetwork 4722 (DD5.1)

DVD: Panasonic A320

S-VHS: Panasonic PV-S7670

LaserDisc: Pioneer CDL-406

CD: Kenwood CD-404 5-Disc Changer

EQ (for CD player only): Furman E151X2

Protection: Furman AV1215 Power Condition/Voltage Reg

[Al Klappenberger]

Ed,

That's a very interesting project. It's especially interesting to me

considering my mods to my Belles that's almost done. I have only to finish

the crossover network for the center Belle. The parts are on the way to

build it. I think it's very worthwhile considering how good the 511 / 811

horns sound. I think you might have a problem with the "AA" network though

becasue of the fact that it really has no squawker rolloff within it but

rather depends on the natural rolloff of the K55 at 6000 to complete the

crossover. I don't know what the University driver's high frequency limit

is, but if it isn't 6000 you could wind up with a hole or an overlap with

the tweeter which is rolled off below 6000 by a highpass filter.

I am no horn expert, not by a long shot, but I suspect that just mounting

the squawker driver directly against the 511 flange would put any throat

discontinuity so close to the driver that any standing waves that would

occur would happen well above the squawkers frequency range. A mismatched

throat adapter might be long enough to be cause problem at a lower

freqeucny. I'd like to hear some thoughts on that theory from some of you

who are better educated on the subject. If you are interested, I could

reattach the K55V and my flat plate "rig" to the 511 horn and make some

response curves. Let me know if you think it's worth the trouble. Since it

was intended to be temporary, I didn't bother to do it before.

Al K.

[WMcD]

I'll go out on a bit of limb here.

The match between the driver and the throat is effected by sudden changes in area. And such discontinuities do harm the response, and perhaps issues of reflected waves.

My intitial thought was somewhat to the contrary. The acoustic impedance presented by the horn to the driver is really controlled by the overall flare of the horn. If everything from inch 2 to inch 15 along the length is okay, a small error from 0 to 2 is not gonna make much of a difference.

It is difficult to figure out the real story because the industry is not presenting sound curves. It is deserving of actual measurements.

I was thinking recently, though, of the work of D.B. Don Keele in his paper, "What's So Sacred About Exponential Horns." This is the primary paper on constant directivity horns.

In that, he describes the use of a conical horn, like a megaphone, for "constant directivity." However, this is made to work by the use of a hyperbolic horn shape between the driver and the cone shaped horn. In some cases, it is rather short, on the order of 1 inch in some applications.

The bottom line is that the 1 or 2 inches between the driver and the rest of the horn does have influence. And perhaps more critical than the rest of the length of the horn, when considered inch for inch.

There is another issue beyond simple "response." Now I don't have the literature. A bad "match" at the throat can set up a situation where there are bad matches across the frequency range. Not just at any one frequency. So the otherwise well matched horn might start acting as a resonator at multiple frequencies. These peaks and valleys could be more easily perceived because they are periodic in frequency. Like harmonic distortion.

The bottom line is that a good "impedance match" at the junction between the driver and the throat of the horn IS important. Generally, the impedance is established by the cross sectional area. So, smoothness of transition of area is important.

Gil

[TBrennan]

Gil--A paper I have from EV shows some effects from mismatched driver exits and horn throats. It shows that if the throat of the horn is larger than the driver exit little damage is done but if the horn throat is smaller than the driver exit lots of nasty things happen. If I recall correctly the horn throat of K-400s, K-600s etc. is actually smaller than the exit of the screw-on Atlas and Ev drivers, I wonder if this is the source of some of the harshness some hear with these horns. The tractrix KP-301 horn I modded my Cornwalls with has a much larger throat than the K-600 and sounds better.

[edwardre]

So...that would say that not only is the distance critical between driver output and throat (via adapter), but diameter of that distance is as well.

Al - According to Tom, since the throat of the 511 is smaller than the threaded output of the driver, 'bad things can happen'. How about you ream out the throat on one of your 511's, test for results, then post? If it works for you then maybe I'll....... Also Al, great point about the AA network and it's lack of high frequency rolloff built in. Hooked up on the garage workbench it appears to sound ok, but I haven't tossed in the test CD and measured for (+)'s and (-)'s in db at different freq's.

In any event, it sounds like I should in the least bore out the 5/8 inch diameter adapter aperture to more closely approximate the output and input diameter(s) of the driver and horn respectively, taking care to create as smooth a bore as possible. Problem with that is that as was my original question "is there any reason that this one adapter with the length and small bore should sound better", what if I bore it out and it (for whatever reason) sounds funky? I'm toast! Now I wish I had some more adapters to dink around with bore size, length, etc.

Then again, according to djk, the 5/8 inch adapter with the length is the appropriate one. Hmmm....what to do, what to do.....

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Ed

Fronts: Pre-1955 Klipschorns (slightly modified)

Center: 1984 Klipsch Belle

Sub: Klipsch KSW200

Surrounds: Tannoy PSM6.5's

Receiver: Denon AVR1701

Video: InFocus LP350 DLP front projector

Satellite: DishNetwork 4722 (DD5.1)

DVD: Panasonic A320

S-VHS: Panasonic PV-S7670

LaserDisc: Pioneer CDL-406

CD: Kenwood CD-404 5-Disc Changer

EQ (for CD player only): Furman E151X2

Protection: Furman AV1215 Power Condition/Voltage Reg

[Al Klappenberger]

Edwarde,

I think I am confused again! If the University driver you want to use has the same threads as the K55V (1 1/8 18 I think) it's actual throat is smaller than the 511 horn throat, not biger. I know the K55V is smaller. I think that is what counts, not the thread size. If I am right, all you have to do is hold the driver flat against the 511 flange and it will be a smaller driver into a larger throat. What am I missing?

AL K.

[johnnyp]

If there is a taper in the bore of your adaptors, I suggest NOT to straight-bore them.

I learned an expensive lesson when I straight-bored a pair of fiberglass K-horn "squawker" replicas. I straight-bored the horns to remove a small discontinuity or rough spot in the throat of one of the horns that i could feel with my finger, about 1 1/2" from the threaded end of the horn. I can't remember what size bit I used, but I only removed a minimal of material. The result was a big disappointment even after careful sanding and blending. Although only an inch or two of the horns were affected, the straight-bore ruined the horns. Gave them that distinctive "cupped hands" horny sound and excessive distortion at higher volumes.

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John Packard

[edwardre]

Al....if anything, as I hold either the SAHF or the K55V to the input of the horn and peer down into the horn, I see pretty much all the 'screen area' of the driver and perhaps a skosh of the bright 'ring' that surrounds the screen are of the driver(s). Is this too what you see? The horn I'm using is a 511A. It clearly has a 1" input. Does the 511B have a larger one? In any event, still sounds like the 'tube' needs to be enlarged.

JohnP....the bore of my adapters are NOT tapered, just considerably smaller in diameter than either driver out or horn in. The shorter one has some pitting. Certainly not smooth as a baby's rumpus. Since this one kind of sucks sonically anyways, perhaps I'll bore it out first and pending the results, consider boring the long one later. Maybe if this proves to be a disaster, I can Helicoil it to repair!

So...with all this in mind, how come is it that for woofers it's different? I know that on the La Scalas and K-Horns, as well as no doubt the Belle, the 'sound' from the 15"ers goes through a slot 3" wide and 13" tall before entering the 'horn' proper. Why? Wouldn't that be equivalent to the 'sound' from the K55V going through a 1/4" slit before entering the horn throat?

------------------

Ed

Fronts: Pre-1955 Klipschorns (slightly modified)

Center: 1984 Klipsch Belle

Sub: Klipsch KSW200

Surrounds: Tannoy PSM6.5's

Receiver: Denon AVR1701

Video: InFocus LP350 DLP front projector

Satellite: DishNetwork 4722 (DD5.1)

DVD: Panasonic A320

S-VHS: Panasonic PV-S7670

LaserDisc: Pioneer CDL-406

CD: Kenwood CD-404 5-Disc Changer

EQ (for CD player only): Furman E151X2

Protection: Furman AV1215 Power Condition/Voltage Reg

[Al Klappenberger]

Ed,

Yes! What you describe is exactly what I see. The bug screen in the K55 is about .75 inch diameter and so is the throat of the Klipsch K400 (and K500) horn. The Altec 811B and 511B have exactly the same throat diameter at the flange. It measures almost exactly 1 Inch.

AL K.