DCAudioDIY.com

For somebody willing to spend some cash, there is a German guy remaking the Klangfilm tractrix with either 1", 1.4", or 2" (plus others) throats.

http://stereo-lab.de/produkt/sl350hz-rectangular/

Now THAT is a really excellent sounding horn. I mainly know it from experiments with the WE594A and in its original Eurodyn applications, both cases with "native" 2" drivers. That horn was a mainstay of the Siemens Klangfilm systems from the 1930s through the late 70s. Awesome sounding horn in either aluminum or resin formats.

In Korea, jc and I built a sort of modified VOT with a huge front horn, double-tuned reflex box for a modified GIP 18" field coil good to 32hz and a 594A on the KL-304. Man, that was a truly fabulous system. I have seldom heard a better midrange. We liked the Kl-304 even better than the WE26A, which is the best WE multicell, at the close listening range in the factory.

It was stupid flat with a 594A, not a wiggle from ~400hz-8 or 9 kc. I never measured any speaker of any type with such an incredibly flat response. I'll try to dig up the Clio sweeps.

The original KL horns were either 29mm or 52mm throat, depending on vintage. Glad somebody is expanding the applicability of this killer design. I'd like to hear 802s on those, but I'm looking for a pr of 288s so I can go with the 1.4" model. Any leads on 288s appreciated...

$700 is a lot of cash for staunch DIYers but this will get you into the stratosphere of horns fast.

I figure the savings on VAT for export should pay most of the shipping costs.

Found a few sweeps of the KL horn with a GIP replica WE594A beefed up with 20 extra pounds of permendur.

The red curve is on axis at a couple feet, the yellow curve is way off axis maybe 45deg @9-10 ft. Not referenced to 1V, we were just messing around trying different things I think the blue line may have been a real 594A on a 31A horn.

These sweeps are unsmoothed, BTW.

The big black driver in the pic is the GIP modified 594A.

I a question about sweeps.
I know most testers used them and they always look so bad.
I am just curious why are they used as opposed to using pink noise.
To my my of thinking sweeps have very little to do with the real world.

That is a funny thing about "tests," unrecognized by most.

They only work because they are not the real world. They provide a more or less (usually less) controlled and defined, if artificial, situation.

Projection of results into non-test scenarios is often more precarious than assumed.

In most cases, the information collected by the test is only valid for the limited conditions of the test, if you really dig in and think about it.

One advantage of sweeps is that they do not allow standing waves to form, whereas pink noise does. So sweeps may reduce room influence on measurements for those of us who do not have anechoic chambers.

At home, lately I have been using noise files and an RTA app for my phone. I am comfortable with a general idea of what is going on in most cases and I think that such impromptu in situ measurements may be considered more "real world."

In the case of the KL horn, I was much more blown away by the listening experience of Louis and Ella that day than the Clio sweeps. That is an unbelievably natural, smooth, and 3-D horn. Don't know how to measure that.

Thanks
That the point I was trying to make
We do or listen to our system, we listen to the room in which the system is playing in.
Our ears are the best test equipment we have once we learn to trust what we hear.
The best way to calibrate our ears is to listen to live music to learn what music is supposed to sound like.

There are other less expensive ways to do maximum length sequence testing than MLSSA. It was the first one to use this technique extensively and is still quite good if expensive. Whatever gated method you use you can eliminate room reflections by choosing the gating point on the return pulse. That is why they call them quasi-anechoic.

However, in a normal room you are limited to frequencies above about 250-300 Hz with this technique. Below that you need to do close miking of the drivers to minimize room effects. The mike should almost but not quite touch the dust cover at the maximum forward position. I do use these methods as my first found of testing. After that I use a series of single sine waves at a wide range of frequencies and at least 8 or 10 microphone positions around the listening area. The results are put into an Excel spreadsheet and the real outliers, ie variances over about 10 dB are not used for the next stage of averaging the results at each frequency. That average becomes the basis for my EQ.

Sine wave testing generally gets a bad rap for good reasons. You can't do that type of testing only at one position as slight movements of your microphone at higher frequencies have significant effects on the measured results. You do need to start with measurements and follow up with listening tests using a series of test music that you know well to get to your endpoint. If you do not test first and only do listening tests you may end up with the same results but will spend a lot of time "wandering in the desert" as I call it.

Don't forget that room treatments and speaker positioning are much more effective than electronic room EQ. Eectronic EQ should be use primarily to get the speaker response correct, barring any gross problems with the speaker itself. Electronic EQ for room corrections is most successful at frequencies below around 50 Hz where the wavelengths are long and in my opinion virtually useless in most cases at higher frequencies.

Quantitative testing and music listening are separate fields of human activity.

Since we use the stuff for music listening, i have long advocated that the best test is using the thing in your normal audio life. If it stays hooked up long term, it is good.

Meaning is always contextual. Change the context and the meaning changes. Thus, home audio gear should be evaluated listening to tunes in the domestic context.

Some folks think this is a radical notion, but careful consideration of the knowledge conditions among various forms of equipment evaluation, suggests that lines should be drawn. The logical positivist standpoint that underlies what usually passes for science considers that only that which is measurable has meaning. For musical experience, most of the meaning is well beyond measurement.

Instrumentation based testing is basically descriptive and literal. Musical evaluation is experiential, aesthetic, and emotional.

Vast implications radiate out from these differences. I studied this kind of stuff for many years in school and after and think about esoteric questions while I'm walking the dog, but I'm sure most people think it is all pedantic nonsense.

And that's fine if they err on the side of listening. It is those nerds who valorize "testing" when they do not fully understand what it is and isn't who have serious conceptual and logical problems.

That said, instrumentation can tell us if something is working correctly, i.e. as expected, and it can point out aberrations that may intrude upon enjoyment, or helps us to understand what they are.

I posted the sweep of the KL tractrix because I think it does show technical excellence. Go measure 100 horns and see how many come up that flat. Flatness is a measure of well-controlled reflections in the geometry and at the edges of the horn. Waterfall will tell even more but FR is a useful index in this regard.

But if this 1930s design didn't SOUND exceptionally great, far better than most, I wouldn't be posting about it here.

I've done both and you can hear with your ears when you hit a room node when sweeping.

That's why Clio and other such instruments sweep the full audio spectrum is a half second or less.

Second -- like Paul pointed out -- having experience with the live event (without sound reinforcement) can "tune" your hearing memory to understand where you are headed with any audio product -- not just speakers.

People like to say this but if they actually did it, there would be a lot less HF coming out of speakers.

I live a 15 minute walk from the Kennedy Center. This summer my son and I heard up to four or five concerts a week. I would come home and listen to the well-recorded podcast on a WE 728B full range with no tweeter ( good to ~10k minus a few dB)and I found that the tonal balance was extremely close to what I was hearing live, but more importantly, the perspective an relationship I had to the music was similar.

Most high end stuff is way more hyper-detailed and in my face than live music. I have to listen harder to live music, get more involved.

In one case, a comparison of Stradivarius and Guarneri violins. where I was sitting about 25 feet away from the players, there was some very interesting HF crazy stuff going on that the 728B couldn't do. Violin is an amazing instrument.

Anyway, i posted this story on my mailing list and got some intelligent input from Cool Hand Luc in Oz, former NYC recording engineer. Apparently, Roy Allison and B&K have been making this point about the downward tilting character of natural room sound for decades and hifi never noticed.



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Which is in essence a fairly uniform tilted curve having more bass and less treble, tweaked to room and taste... largely concurring with the findings in the 1974 AES paper by Bruel & Kjaer....

> On Feb 12 2017, at 5:42 PM, Cool Hand via Sound <sound@soundlist.org> wrote:
>
> "Surely distance is a major factor."
> "We're all averse to exaggerated , unnatural & excruciatingly 'detailed' reproduction but I'm not sure if that means limiting HF bandwidth is the obvious inference"
> "I remember that if you brickwall above 8...10k, *any* recorded music will lack spatial information."
>
> What I've arrived at is largely an extrapolation of the above observations....
>
> As Joe duly noted, part of the whole live thing relative to home listening thing is the very distance a listeners ears are typically located, and with this distance comes the inverse square law and also significant diffusion thus the level but NOT specifically the frequency response itself is which is curtailed, which Owen points infers.

When listening indoors you get the exact opposite, closer sound source and significant reflection which exacerbates the very issue in question.

Again, as Christian noted limiting the highest freq's, regardless of whether they are apparently musically relevant, sucks the spatial information out.

So as apparently obvious is all this may appear, much experimentation was undertaken before arriving at my present system tuning whereby the frequency response extends well beyond my own tested hearing 'limit', but the amplitude of high frequencies is gently attenuated from approx. 4K, and it took a heck load of tweaking with the crossover topologies (2-way horn loaded system) to optimise the curve rate and shape to taste

The result is such there's absolutely no sense presence or spacial information is lacking, quite the contrary, but instead of hyping the presence band and above which a great many speakers (and microphones in the first instance) do in order to add excitement, the opposite occurs and the listener feels more enveloped and drawn into the sound-field, instead of being pushed backwards by an elevated amount of information.

A large part of the art is in understanding (i.e: by critical measurement) how very significantly your indoor listening space detrimentally influences the response of speakers no matter how well designed, and for me I'm far more irritated by excess or irregularities in the high frequencies than lows, which are often considered the greater problem !