Time-Alignment for Folded Horns (Patent)

[D-MAN]

I can't say I've ever heard that from a Khorn. But I DO know what THAT "tubby" sound is...

If one attenuates a point in the 500-600 Hz range down in a "trough", one is sure to get what I think that sound being called "tubby" is... In that case, it's too much bass horn (coloration at that range) and not enough midrange. It has NOTHING to do with diaphragmic offset timing issues.

But that's the room, not the KHorn! Either that or the midrange is attenuated too much via an inappropriate autoformer setting.

DM

[DrWho]

Ok, let's see if I can get this right...

[blockquote]"Other smarter folks" are often wrong. Get in

your car and come see me this weekend -- I'll pay your gas bill. I'd

like to show you how smart other smarter folks are.[/blockquote]

lol, not all the "other smarter folks" are wrong though...but I do

agree that we can't just trust everyone's opinion (even PWK for that

matter). I might have to take you up on that 1/2 gas bill offer...how

far is the trip from Indy? I make it by colter's place every once in a

while.

btw, I hope people don't get the impression that I hate the khorn or

anything like that...I have heard the speaker in a variety of very

quality environments and there are attributes very prevalent in every

system (it's just the "khorn sound") and the tubbiness isn't always

present in all source material (but it shouldn't be there in the source

material that it happens to occur in...which can be verified my

numerous high quality headphones and studio monitors). I would describe

the tubbiness more as a ringing horn that needs to be damped...just

like how those annoying metal mids need to be rope caulked; i want to

"ropecaulk" that bass horn section. I do feel that the delay only

amplifies the effect because it is not effectively masked by the

midrange sounds...

If you can't post the reasons dean, would you perhaps PM or even PM me

your email so that I can find out? it's been driving me nuts to the

point that I will blaim anything as being the reason (for all I know

they tubby sound is because "Dr. Bose" is off in a corner farting in

beat with the music trying to make me hate the speaker....and the

reason it doesn't happen all the time is cuz he has to charge

up...how's that for a kid's imagination). I do know that it's not the

amplification, source material, or the room, so it's gotta be the

speaker (and even "deafy" my nickname for kait who is deaf if in one

ear can hear it....in fact she approached me on it! i didn't even have

to ask if I was looney). []

btw, tubbiness comes from a boost in the 200-600Hz region (yes i know,

that's a huge range)...Tubbiness is also a think very easy to achieve

in a PA (due to the distances involved) so it's pretty much common

practice to implement a -6dB wide Q EQ in all the monitors and FOH...I

don't always do it, but it's one of the first things you can do to

unmuddy something.

[Deang]

When I read your comments, I thought, "That's because corner placement stinks". Since that's probably not the smartest thing to say around here -- I bit my lip. It's really not the K-horn's fault though, but what I feel to be something related to poorly constructed corners. Klipschorns situated on the inside walls of modern homes are going to struggle. There's an immense amount of energy released against the tailboard and side walls -- and pushing Klipschorns into what amounts to being nothing more than narrow resonating chambers just isn't going to be conducive to good bass. Outside walls or good false corners is the way to go. I chose the latter. No corner is better than a weak corner.

I'm in the Dayton area -- a little less than two hours from Indy.

[DrWho]

aye, but I still heard it at artto's place and he has gone way

overboard with getting a good strong corner: his speakers are bolted

into his foundation and the walls are extremely reinforced...now that I

think about it, I forget what exactly he did, but he still had that

same signature sound...

[Deang]

That's interesting. I don't know how to respond except to say maybe we aren't talking about the same thing, or maybe mine do it too but I don't notice it. Klipschorns I heard back in the late 70's sounded "tubby", and a bit boomy -- like the cabinet was resonating. I heard the same thing with mine when I first got them and had them pushed into my corners on the short wall. I was bent over by the wall one day straightening out my power cords when my hand touched the wall where the power strip was laying. The amount of vibration surprised me -- since I was almost 15 feet downstream of the Klipschorn. Placing my hand on the wall and following it down the room, it was apparent the whole wall was shaking. My house was built in the 50's, and by today's standards -- it's pretty solid. After building my false corners, pulling them out and turning them -- I don't have anything but what I would consider to be a rock solid bottom. Of course you never know, I could just be in denial.

[3dzapper]

There may be some compromise in the paper cone of the K-33. It also manifests itself in the midrange of Cornwalls. I find Heresys with the K-22 to have a clearer midrange than Corns where the only real difference between the two is in the woofer. The 400 Hz horn of the khorn takes almost an octave of this midrange responsibility from the K-33 however, some mids still reside with the K-33.

Just my thoughts, I have no emperical measurements to confirm this.

Nevertheless, despite the shortcoming, I wouldn't trade the ability to hear NEAR perfect reproduction with any amp from 1 watt to 1,000 watts for any other speaker.

Rick

[DrWho]

Well ironically I very much like the cornwall and don't hear the sound

there at all....but the cornwall does emphasize the lower lower mids a

bit, but it's never noticeable with rock too much because it helps

fatten out the sound. I'd say more in the 80-120Hz range (a different

range than the tubby khorn bass)...that said, hornloading a driver

changes a lot of things so perhaps something with the loading is

bringing that out.

Dean, perhaps you don't notice it so much is because you've already

heard such a huge contrast in the sound...source material and the room

itself are other factors as well (perhaps you've got a standing wave

centered at the frequency).

I really think some time impulse measurements of the speaker would

really put me to rest...One thing that sits in the back of my head is

the fact that rock was meant to be played back on direct radiating

speakers (that's what was used in the studio most likely)...there are

certain distortions inherant to the design that a horn loaded subwoofer

minimizes....I would argue that these distortions are supposed to be

part of the music (similar to the distortion concept with guitar amps).

Distortions in the mids and highs however are annoying and that's why I

love the hornloaded mid and tweeter sound (it doesn't really screw up

the mix)...but every single hornloaded sub I've heard has always failed

in comparison to an equally performing direct radiating one (to qualify

that, I've heard 4 other hornloaded subs apart from the khorn and

lascala.....and I HATE the lascala sound) []

There is a cleanliness to the khorn sound that I can't deny and

non-rock stuff sounds amazing on them (though that tubbiness keeps

returning every once in a while). When it comes down to it, I can't say

that the khorn is ultimately flawed per say, but I can claim that it's

certainly not the right speaker for the music I listen to. So no

offense if I don't like your khorns, but I'm totally open to changing

my opinion (if indeed you got rid of that tubbiness dean, then I

certainly want to hear that sound.....well, maybe I don't cuz then I

might end up selling my car for some speakers..........) []

[D-MAN]

So are we talking cabinet resonance, cone deformation, corner placement, or horn-induced colorations? - or D (all of the above)!

Whatever it is, it certainly doesn't seem like a time-alignment problem to me...if it was you would hear it consistantly across the board, regardless of the source material.

Ok, well, corner placement is particularily "hard" on the midrange frequencies, but is great for low bass reproduction.

The use of 1/2" plys in the Khorns construction is not particularily good for preventing resonances unless rigidly braced - I recommend that you check out the Speaker-lab K plans for internal bracing - works pretty well.

The K33E is a peculiar animal - very light cone, probably a bit "peaky" in its response and with a 6db slope on the crossover, MIGHT not fall off as rapidly as MIGHT be desirable - who knows?

In most cases, though, the room itself is probably the issue IMO.

But since I don't really know what "tubby" actually is, nevermind!

DM

[DrWho]

aye, don't forget that I can still hear the time delay despite the

tubby thing...I just think the time delay increases the apparent

magnitude of it (because it's not being masked). I hope that helps

reconnect the two seemingly unrelated aspects...

Like I said earlier, it would all be verified with some impulse

measurements at lots of frequencies (klipsch has the stuff to do this

and prob even have the measurements recorded somewhere, but i doubt

they want to share them with us....so one of you rich guys go get all

the fancy equipment needed and let me borrow it along with a pair of

khorns) []

[D-MAN]

Well, on the time-delay thing, agreed. It's undeniably present. I've not really noticed, though.

Here is a mod that would be beneficial to a Khorn in lessening turbulence (which would increase speed somewhat) at the tailboard, as well as serving to strengthen the tailboard against vibration to a noticable degree.

This is from PWK's first 1940 patent, top view. I notated the tailboard wedges. 45 degree angle is used.

DM

[D-MAN]

Here is the Speakerlab K back chamber brace I previously mentioned. This diagram is from PWK's 1945 Khorn patent, which I notated.

Both of these mods can be done after the fact.

DM

[3dzapper]

I would think that it is easier and less detrimental to apply those braces in the left hand image to the inside of the motor box. I have pieces of Dynamat there to damp the board's resonance.

Who, Next time you are at CP1s, listen to a clean piano recording. You can hear the effect I refer to in the lower to mid right hand. at these frequencies, the 400Hz Xover of the Khorn is letting the K-55 play those notes. On the Corn, this point is 1/2 octave lower and a bit of cone break-up in the K-33 can be heard. Corns do sound great, it's just that all speakers have their quirks.

As I said the K-22 is better here but it lacks an octave of bass.

BTW, if you want to rock, there is nothing better than a pair of Khorns. Their ability to play at very loud levels, with proper power, with no distortion is remarkable. I'm talking well in excess of 100Dbs and long term listening with no listener fatigue. Well, the things that go along with hours of loud rock and roll do cause some fatigue.[]

Rick

[D-MAN]

I would think that it is easier and less detrimental to apply those braces in the left hand image to the inside of the motor box. Rick

Rick, it is probably fine either way. My opinion (questionable anyway) is that the back chamber of the Khorn is already somewhat undersized and adding anything further to it that decreases volume will raise the Fs of the driver slightly.

The braces in the horn channels is somewhat more negligible, IMO. I have heard horns with this mod (Gil could chime in about this, he built some Speakerlab K's) and there was no degredation to the sound in any fashion that I could hear. I imagine the benefits of reducing resonances outweighs all other concerns (it's only 1/2" plywood and doesn't displace alot of space or cause much of an obstruction). Perhaps my drawing wasn't clear.

DM

[D-MAN]

Here's the brace as defined in the Speakerlab K plans...

I redrew it - the dimensions are accurate, maybe not the proportions of the drawing...

DM

[D-MAN]

Here is a slightly better view of the mod using the previously posted pieces...

{edit} oops, I guess that I assumed it was a better view!

DM

[3dzapper]

I was playing one of my Belles as I sanded and oiled some of the pieces of the other. When I was done wiping, I just listened for a while. I seemed a tad boomy in the upper bass like cabinet vibration so I put my hand on the side. Now granted, I was playing if louder in the open garage than I would generally in a closed room but how loud can a ca1958(?) Scott 99C 6L6 amp get?

Sure enough the side panel was vibrating to beat the band.

My questions: has anyone put side reinforcements in a pair of Belles? What effect did it have? Is it worthwhile? Do you have plans, measurements or pictures?

Rick

[D-MAN]

You certainly won't hear any degradation. My corner horns are braced in the manner that you are talking about. There is a thread on this subject somewhere... might be a La Scala thread.

{edit} found this, its Frode's super-modded LS, but it's got the side channel braces.

DM

[3dzapper]

DM, I've seen that before on a LaScala. The difference with a Belle is the vee grill. If nobody has done it, I'll figure a way and be first.[]

[Marvel]

I'll interject a post that I found by Tom Danley, about time delay.

Some has to do with the phase response of a signal going through a

speaker. This all makes my head hurt, but I thought it might add more

useful info to this thread. I don't remember where I found it, but it

is one of those things I saved.

Consider how a normal "perfect"

speaker spreads out a signal in time. Make an imaginary signal that has

equal amplitude content from 100 Hz to 25 Hz, a specific waveshape

which has this property. Take an imaginary perfect flat response

speaker who's upper and lower cutoffs are way past our needed

bandwidth. This mass controlled "flat" response speaker has a -90

degree lag or delay, at 100 Hz the phase shift is equal to a source

2.83 feet behind the speaker cone, at 50 Hz, the delay is equal to 5.66

feet, at 25 Hz is equal to 11.32 feet and so on. This test signal's

wave shape defines the input "time" of each frequency component. When

reproduced, the highest frequency component at 100 Hz emerges from the

radiator 2.5 ms AFTER the signal arrived at the driver terminals. At 50

Hz, this component emerges 5 ms AFTER the signal hit the terminals and

at 25 Hz, the signal emerges after 10 ms and so on. With the driver

spreading the signals frequency components out in time, it is simply

not possible to retain the same waveshape as the input signal, lower

frequencies arrive progressively later in time than the original

signal.. Any signal reproduced is done so with the spectrum rearranged

in time by the drivers acoustic phase response.

If one had a driver which had a very strong motor or a normal motor but

very low moving mass, one gets an "over damped" response. This term is

from filter design meaning that it is not optimally flat, excessively

damped, rolling off too soon and gradually Should the slope of the

response reach 6 dB per octave, the driver is operating in the Velocity

controlled mode, while the response is not flat, the acoustic phase

DOES track the input signal (zero degrees) and the different frequency

components are not spread out in time. The waveshape of the input

signal is more closely replicated as the frequency components are in

the original "time" although the amplitudes are off 6 dB/oct. Each 3 dB

/oct change in the slope produces a 45 degree change in phase.

An over damped response more closely retains the time information where

a flat amplitude response cannot. A proper LF horn can have flat

acoustic response AND roughly zero degree acoustic phase.

For a person more sensitive to "time errors", they will likely find an

over damped system more realistic. For a person more sensitive to

"amplitude errors" the traditional "flat response" system will be more

satisfying. For the person lucky enough to have heard a proper lf horn

system, you have heard that one can have "lightning fast" sounding bass

and still make your pant legs flap.

[pauln]

I guess its time to throw in some thoughts that will mess up most of what has been discussed here (my new hobby), and maybe clarify why PWK thought time alignment was BS.

Let's start with a note at 50Hz and let's see how many cycles it needs to execute before you can hear it as such. Although you won't if it only completes one cycle, let's pretend that you do. That cycle takes 20ms to complete. Wow, that's a long time? How far into the cycle's execution did you hear the 50Hz note? Did you wait until the end or did you (still pretending) get it before it was finished?

I'll jump to the answer - it takes quite a few cycles in this range, more as the frequencys get lower. There is a web site that lets you set the number of cycles to hear this for yourself http://sig.sapp.org/sounds/wave/00readme.html. Look under the Psychacoustic section Minimum Periods for Pitch.

Five cycles at 50 Hz is one tenth of a second (100ms).

Five cycles at 30 Hz is 333ms - a third of a second!

Yet in both of these examples you will not be able to determine the pitch.

Furthermore your ear/brain is not instantaneous either. By the time you add all these delays (not counting the speaker/horn wall stuff), I would have to conclude that if you DID create a system that did perfect time alignment it would not sound natural or correct.

In fact, if you listen to some modern hip music with the drum machine bass drum track (with the beats monotonously pounding on the 1 and 3 beat like a demented march) you will notice that the programmer DID evoke and execute an approach to time alignment by virtue of the way the midi score is composed. The result, if you listen, is that the drum beats are slightly too early giving the effect of a drummer playing a little faster than the rest of the "band".

Hope this helps.

Paul