Klipschorn Bass Bin, Back Deflector Panel; Modification?

[Groomlakearea51]

Currently working on the restoration of a pair of KC-BR's. While sitting and looking at the bins and the geometry of the deflector panel, I was thinking (it hurts to do this sometimes...), and I thought about two things;

First, how would a triangular "wave guide" help really "aim" or deflect the bass around the final corner, and second, if that is a possible idea, why not a variable "wave guide vane" that allows for bias to the left or right.

Reason for #2 idea is that most folks probably don't have identical open wall space on both sides of the K'horn. The ability to "bias" which side it comes out may be an interesting option.

So... thinking about this, I also thought that most people really don't want to permanently install either a or b, so if it was made with 1/2" plywood pieces, installed with velcro, it would allow the user to experiment with the effects.

Below is a diagram; could some of the technical folks look at this and opine. I am going to test it in a couple of months and see what happens.

[Guest " "]

The wave guide has been seen on a lot of k-horn plans since the 40's.

You could argue that it will help with wave bounce back into the horn, but trying to identify the effective frequency would be a chore, and probally outside a typical k-horns operating range.

[Groomlakearea51]

Interesting! Thanks; if that is an idea to reduce the wave bounce, can I assume the apex of the wedge should be as close to the opening as possible?

Also, thoughts about "bias" to left or right by an "off angle" deflection scheme?

[Guest " "]

The dove tail modification can be seen on this k-horn rendering.

This is supposely a 1940's design.

I have used the dove tail mod on a few clones.

[Groomlakearea51]

I wonder why it did not end up in production; unless it was insignificant; that being said, how did it work on the clones?

Again the thing I'm really wondering is what a variable "wave guide" would do for unequal (cluttered, uneven lengths, etc.) corners. I think I'm going to make two versions, an equal, and a 60/40 bias version that you could "flip" and apply or force more to left or right to compensate. I suspect it will knock off spl, but for limited applications, or for folks with poor corners (at least until they move or modify a room), it may help.

[Guest " "]

It was hard to attribute the dove tail waive guide as an improvement with out controls and measuring processes, so I can't say if it was better or worse. It sounded fine to me, but I did not have a production K-horn to compare to.

If you have an issue with corners, another approach which I used in the mid 80's and is frequently discussed on this forum are the attached false corners. I have seen them in different flavors, some stop short to allow the woofer access door to be functional, others go out quite a bit so it is flush with the front lines and a second trap door is added to access the woofer.

[Groomlakearea51]

The "false corners" are like what Klipsch has done with the 60th Anniversary Klipschorn to as they described, "allow toe in or out".

The photo below is the side view of the Klipsch advertisement photo for the 60th Anniversary version. Interestingly, they also enclosed the tops.

I'm ok with my corners, but am experimenting with placements in corners that are odd or unequal from left to right. I'm testing one pair in normal corners, and a second pair as an inner pair with the left side of a component cabinet as the "right wall" for the left speaker, and the right side of the cabinet as the the "left wall", for the right speaker.

Sound's ok, and interestingly, because the second pair of Klipschorns are firing 90 degrees away from the normal axis, the apparent stereo center is much wider and further back than the normal axis intersection. When running both pairs, this "presence" becomes even wider and deeper.

[Groomlakearea51]

BTW, Below is the diagram of the setup I've been fooling around with. The basic idea was to use a second pair of Klipschorns to compensate and expand or widen the normally narrow "perfect" listening spot. It's a "home theater/ stereo" experiment "in process".

As a matter of explanation, I use an Esoteric Sound Super Connector to "collect" the 250mv outputs from the CD/cassette, turntable, DirecTV/XM radio, and DVD, and send them to an AX-7 mixer. Each pair of speakers (79' KC-BB's and 85' KC-BR's) is independently "amped"; they only see an identical source coming from the AX-7. I simply use the mixer to control master volume once the amps are "set" and matched.

I am going to experiment with the "wave vanes" on K-Horn pair #2. Using separate (but identical) amps allows for fine tuning with sound volumes. It also allows for use of one, the other, or both (or more) sets of speakers, dependent upon what I'm doing. I can do work at my desk with only one pair at a really low volume with the weather channel or an XM channel, or grab a cold one and turn it into the "wall of voodoo" (if my wife is not home...).

Other thing I'm going to do in a few months is modify the system cabinet to hold a pair of LaScala's as a "center" channel. They will be on a separate identical amp also. When that time comes, I'll probably look up the bass mod plans for the bass reflex ports for the LS's and add that when I re-finish them.

My current testing method (until I can replace my 4 ancient and not working omni directional microphones), while far less than scientific, works fairly well in my case.... I go get my wife... (WAF factor...). She's fairly critical sometimes, and as the mother of children, has that super human, ultra enhanced, almost mythical ability to hear anything that does not sound right (especially when the kids are up to something...) I put her in the center and ask her, "Honey, does "a" sound better, or.... "b" sound better?".

First project, however is to fool around with wave guides on pair #2.

[Guest " "]

That's a first seen for me...kinda like direct-reflecting horns.

Have you ever looked into using 511b mid horns and bi-radial tweeters like the EV-st350, jbl 2505, etc, to wide the sweet spot.

Al has a few articles on his site with some tech data as well.

[Groomlakearea51]

Yup, I suppose it sorta puts Bose to shame....; you can see why I'm thinking that if I can slightly deflect the bass, or bias it left or right, it could widen or narrow (or lengthen or shorten) that "circle of life" to suit other room configurations.

As far as other mid horns, bi-radial tweeters, etc., my budget is really too restrictive and my wife (bless her WAF heart) really likes the appearance of the Klipsch speakers. When I had JBL control monitors (4311's, 4312's, L-166's) and Klipsch all over the place, she complained alot about the house looking like a high end stereo store. So all the JBL's went to other new homes....

While the diagram does not show it; each K-Horn also has a Heresy-I on top that can also be angled (Sometimes I just listen to the Heresy's). There will also be a pair of angled up and out Heresy's in the rear corners at some point when I get finished with a Heresy-I rebuild project (cabinets done, but still waiting for more lacquer primer to come in).

[DrWho]

Sounds like you're in need of Jubilee bass bins.

And not to diminish your ideas, but you're introducing a lot of comb-filtering by using multiple speakers playing the same material.

http://www.prosoundweb.com/studyhall/am/lobes/lobes.php

http://www.prosoundweb.com/live/articles/jbrusi/pa.php

An interesting conclusion of the articles indicates that by spreading two khorns apart and playing the same material, that the horizontal dispersion is going to narrow (so in your diagram the sound will be steared to the sides of the listening position). It almost seems non-intuitive until you try it for yourself - it's definetly something to be concerned about.

[Groomlakearea51]

Please, you are not diminishing my ideas at all; the more constructive criticism, observations and information, the better off I will be (besides I diminish my ideas all on my own). The greatest thing about the Forum (for me, anyways), is that it makes one think about alternatives and consider other good ideas!

Yes sir, as soon as I win the lottery, a pair of Jubilees are right up there on the list. Actually, if I win the lottery, I'll build a new house and flush mount a couple pairs of the KPT-MCM-3's or 4's (or whatever those monsters are called), throw a few KPT-535 Jubilees in the bedroom, and give the Klipschorn's to the kids (pearls before the swine...).

In any event, I first noticed that pesky comb filter problem (well discussed at those two articles you kindly provided) many years ago when I first stuffed 2 pairs of K-horns, 2 pairs of Heresy's, and 2 pairs of 4311's in an apartment living room the size of most bathrooms while on active duty in Germany.

It seemed, and still does, that the number one thing is the "horizontal plane" of placement. Arraying them all in line, along that "line", seems to be the root of the problem.

In the case of this room, I'm wondering several things; first, if this "false" corner from the stereo cabinet has not altered the propagation geometry to where the "dead spots" are not as noticeable. Second, I'm wondering that since the inner pair is firing towards the side walls, whether that additional delay in arrival by using the walls to reflect the signal may also be somewhat compensatory.

I also found that placing other objects in the room (symetrically) also helped, probably due to benevolent interference.

This room is 24' x 24' and because they are "unnaturally" close to each other, I may not be far enough away to really notice it. That being said, I always have found in the past (and this room is no exception) that whenever I used the Heresy's on top as a speaker system B (when also using the system A's Khorns at the same time) required a very careful adjustment in and/or out, and adjustment of the angle of "attack" (toe in/out) to overcome the filtering effect. Once I found the right spot, the difference was dramatic.

Same issue arose with the 2 Heresy pairs in the living room when we first bought the house and moved in. I had to alter the "angle of attack". The pairs are 24' apart, two on each side of the room, at about 7' off the ground and about 4 inches apart. Outer pair is about 10 degrees off the axis of the side walls; inner pair set about 4 inches further back, but are about 15 degrees "off axis".

This took trial and error, and once I found the "spot", they sound fine pretty much throughout the room. There are two "lobe" areas about 3' square, of some bass attenuation that are present (about 2/3 of the way deep, and about 1/3 of the way from either side wall), but these are symetrical and unless someone stands on the two coffee/end tables located at those spots,.....

Trial and error, and each room has always been different.

When I retire and move, we are going to build another house, and have a dedicated stereo/ home theater room that is about 36' feet wide but only 24' deep, with a 16' wide x 12' deep "church nave" in the center of the speaker wall. I also want to have the ceiling "vaulted" with the speaker wall as the starting 8' height and opening up to 14' to take advantage of the volume change. Sort of a giant horn.

Experimentation is certainly the way to go.

[D-MAN]

I'll throw in my 2 cents on the 1946 Khorn seen above.

The 45 deg. reflectors at the tailboard is a good idea, it certainly won't hurt anything. However, at the time, it was a 12" driver version, and 12" drivers typically have a higher frequency corner than a 15" one naturally would. Therefore, the point of retaining higher frequencies becomes somewhat pointless if you want to stay with a 1rst order (6db slope) crossover.

So I see it as being related to the mass roll off of the driver as to whether the extra work of a 45 deg. reflector on the tailboard is going to be beneficial or not. I take it that PWK decided it was relatively pointless (or "non-ecomonical") for the 15" variety. The crossover and driver/reflector issues and subsequenct decisions were apparently economically based IMO.

The 12" version also used a front-chamber (at the throat) to reduce the upper frequencies (mass reaction) acting as a low-pass filter, and allowing a 6db slope crossover to be used. This is enough to indicate the ability of the 12" driver to put some upper bass frequencies through the horn. The lack of a front chamber on the current 15" version also indicates that the upper frequency rolloff limit of the K33 is low enough to make a front chamber uneccisary.

There is an issue with the intermediate channel structure in the Khorn as it goes from horizontal to vertical to exit at the tailboard. This "twisting" of the waveform is naturally detrimental to upper bass frequencies.

It seems to me that if you WANT to use the wedge reflector at the tailboard, you should also go with a driver with a rising response curve, to compensate for losses and acheive a higher band pass. That way, there MIGHT be some upper bass frequencies to reflect!

I'm sure that there is a finite limit to the frequencies that can be forced through the channel twisting, although I don't know for sure. Seems to me that one could theorectically expect to acheive a 500Hz crossover point, though. I would be willing to bet it could be done, but more than likely, you'd have to change drivers to do it. Also the crossover would have to change, of course. Whether you could stay with a 1rst order crossover would also have to be resolved and that would depend on which 15" driver is used.

It would be a major undertaking, in other words.

DM

[Groomlakearea51]

Interesting!

Maybe a good question would be: If one wanted to deflect or bias the bass to one side or another, and having the option of removing the "tailboard", how would one do that?

On those lines, I'm wondering if the "vane" could simply be a thin, say 1/4", vertical strip, approximately 4" wide and the length of the two opening areas. It would be flush to the tailboard, rotate on that axis, extend to the rear opening, and be able to "swing", and physically block or partially block one side or another?

Since that final "twist" is at the exit ports, it would seem that it would be more a matter of "defeating" either the right or left twist?

Let's say that, by putting that vane in there, and biasing it to one side, the displacement volume of the horn at the exit ports would, in substance not have the dramatic increase in displacement volume as it does when it "hits the walls" with both sides (volumes) available. Then would it possibly stand to reason that the side to which the volume is displaced would be quite "strong" at a closer distances?

This may also have an impact on the "comb effect" because the horn, while the same length, now does not have the final exit volume, and probably not the same wave propagation characteristics(?).

Any ideas, or should I just get some mics', try it, test the spl, get my wife's ears in here, and "report back..."?

[D-MAN]

I don't follow what your purpose is... what are you trying to achieve?

If you become asymetrical on the horn (now this really DEPENDS, but), you will trash the phasing of the waveform, the higher in frequency you go, the worse it will get.

Also, are you modifying or building from scratch?

DM

[DrWho]

I think false corners (as laid out in the Dope from Hope) would be a far better alternative. Then you just toe in the entire enclosure (which you will want to do anyway). I believe heavily in the KISS principal.

For what it's worth, a pair of Jubilee bass bins aren't that expensive (relatively speaking) and even something you could build yourself if you wanted.

[Groomlakearea51]

What I'm trying to do is figure out a simple way to at least partially compensate for crappy/ odd corners, and/or alter the bass "point of origin" as it exits the KC's to compensate for crappy or odd room acoustics. This crazy idea goes back to the idea of deflecting to one side or the other. Midway in the discussions, the issue of comb filtering came up and I got sidetracked.....

The bass horns will still be symetrical (both guides would be the same adjustment), but the volume at the exit port would be reduced.

While refinishing the one pair of KC-BR's, I'm considering modifying that pair. Got three pairs and the "mod" pair will eventually head back to the stereo room to experiment with; other two pairs are in place per the diagram. LS's are stripped and in line for refinishing. Won't go there until January.

What I'm doing is looking at the different possibilities.

Bear with me; I'm not the brightest candle in the chandelier (or is that the crayon in the box...), but I'm willing to learn. I've started "learnin myself" as fast as possible on acoustic wave stuff, but to this point, It's been trial and error with simply physically adjusting the placement of speakers to achieve a good solid sound from multiple speakers of the same design, using independent amps, but with the same input source.

What's my goal: to better understand the basics of sound waves, how they work, and how to get as much of them them to some point (bigger the better) in a room without too much interference.

[Groomlakearea51]

I think I'll also return to the table saw and cut some false corners as well. The deflectors will be a 15 minute job (attached by velcro), and the false corners would be from 1/4" plywood, also attached with velcro (I've got big rolls of the stuff from other non-Klipsch related projects).

I'll fool with both and see what happens; n the interim, break out the books and start studying sound waves....

[DrWho]

Do you have any means for measuring your results?

You might also find this thread (rather the pdfs in it) an interesting read:

http://forums.klipsch.com/forums/thread/796165.aspx

[Groomlakearea51]

Dr Who

Means of measuring? Other than what it sounds like, not yet, but am going to get more "edumacated" first. Then make a decision as required.

Read the thread (twice....) started by Mas

In regards to "Small Room Acoustics", one of the things that immediately made the most sense was, "Thus, to overly simplify, our need is to control the early reflections and create an effective ITD/ISD gap, and then to create an environment where the early reflections Lre are well behaved and not intrusive, as well as to diffuse the remaining Lre specular reflections into a pseudo reverberant field".

As soon as I can get a chance, I will buy a copy Sound System Design. As for now, I'm wading through the study hall of Syn-Aud-Com articles on Proaudio's site. Got signed up for a couple of free tech magazine subscriptions too![]