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Why horn-loaded loudspeakers are subject to design tradeoffs


Chris A

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Horns just sound different, and they sound different in a very good kind of way, but if I had a question to add to a FAQ, it would be this: Do horns really produce less distortion just because they're horns?

Is it possible that, in general, horns produce less FM distortion, but equal Harmonic distortion?

See http://www.hps4000.com/pages/special/woofer_distortion.pdf for an answer to that question. This is a very good article on bass bin modulation distortion with Klipsch professional MWM and bass reflex (vented) bins under test.

I think if one were to go to Eight 15's, which, volume-wise, would be the same as the MWM bass bin he tests, things might be more equal. So one would have to listen to one and the other A/B. I'm sure the horn would still win.

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Thanks for comments about being gracious. It is sometime annoying that folks pull threads off topic. But such is our free society here.

But back to the subject of distortion.

We have some information on sources of distortion.

One is the compression of air at the throat and the front air chamber, which is fairly unique to horns. Basically, you can compress air up to double atmospheric pressure and above with some linearity. But you can't rarify air except to a vacuum, or minus one atmosphere. When we get down below one atmosphere, the function is non-linear and the transfer function gets a bit wacky.

The other source is the movement of the diaphragm inducing Doppler distortion.

When we speak of harmonic distortion we are feeding only one frequency to any "system" under test. We see integer multiples of driving freq. Generally this is a figure of merit for distortion in a system. On the other had, physical musical instruments make these. In music they are called overtones. (OT, in the 1700s a clever fellow figured that if you add a bass note two octaves below a major chord, some of the harmonics of the bass note are exactly at the three notes of the major chord. This is like, "adding some bottom." Edit: So you have some experience with harmonics even if you've not recognized it as such.)

When we speak of intermod distortion in any system, we are usually feeding only two freqs of F1 and F2 and seeing how we get F1 plus F2 (which is okay) and F1 + F2 and F1 - F2 as an output. In many areas of engineering these are called "beat" freqs. You do know this, but might not know that you know.

For example, if you tune a guitar you listen for the beat freq of the higher string being off note from the lower fretted string, and the combination makes the F1 (fretted low string) - F2.(high string) put out some low throbbing sound (they may be up around 400 Hz but their difference is low in freq causing the throbbing). When the high string is adjusted to the same freq as the fretted low, the throbbing goes away. This is because F1 minus F2 is reduced to zero. This is because the freqs are the same.

This is to say, if you've ever tuned a guitar, you have utilized intermodulation distortion. (I think the non-linearity comes from the body of guitar.) Therefore, you may say you don't understand this intermodulation theory, but you have used it. Smile.

Focusing on the subject. We have some studies on measures of harmonic distortion and intermod distortion and how horn speakers fair versus direct radiators. My guess is that horn speakers come out on top and PWK's description of total distortion for horns being low is true. This is true even though PWK seems to be using very high SPL's where his Tektronic instruments, in those days, could show it.

What is interesting an Internet publication by the great amplifier designer Nelson Pass. I'm a bit of a Doubting Thomas about subjective reviews of amps. Yet every time there is rave review, it seems to be of a Nelson Pass design

https://passlabs.com/articles/audio-distortion-and-feedback

His subject is feedback in amps. He is saying that when he does intermod testing with seven tones (rather than just two) the distortion products (added fqs) go way up. As applied to music, things get muddy

Gee, isn't that like our horns? My thought is that horns even at low levels have this benefit. We have not seen this measurement applied to speakers, to my knowledge. Therefore what has been presented showing the relative merits of horns and direct radiators do not tell the whole story. Seven freq intermod measurement may be necessary.

Something to think about.

WMcD

.

Edited by William F. Gil McDermott
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For example, if you tune a guitar you listen for the beat freq of the higher string being off note from the lower fretted string, and the combination makes the F1 (fretted low string) - F2.(high string) put out some low throbbing sound (they may be up around 400 Hz but their difference is low in freq causing the throbbing). When the high string is adjusted to the same freq as the fretted low, the throbbing goes away. This is because F1 minus F2 is reduced to zero. This is because the freqs are the same.

This is to say, if you've ever tuned a guitar, you have utilized intermodulation distortion. (I think the non-linearity comes from the body of guitar.) Therefore, you may say you don't understand this intermodulation theory, but you have used it. Smile.

this "throbbing" you speak of are merely the sound waves interfering with each other as the two tones resonate at different frequencies. it's akin to a moiré pattern in visual terms... as the two frequencies become closer they modulate slower and slower until they are nearly indistinguishable from each other and become "in tune". 440hz for the musically uninitiated as a generalized standard.

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Interesting subjuct matter at this place in time, i just so happen to be buying Justins horns from, well, my old splits, and will be experimenting with various cap combo's wile leaving the two 8" Mid Drivers fully wired in.

This sure would be a great time to get a PC audio program W/Mike and see the before and after, i have quite enough on my plate with these speakers already, ill just trust my ears and give the wife a before and after sound check with Bella.

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I was directing it towards all the Math geniuses to put all these flaws on a note pad and build something similar with none of them. It AINT happening.

Well I've been working on several approaches for a good 3 years or so.....you're right, it's crazy near impossible to do.

However, I do think an improvement can be made if you only target an LF corner of ~80Hz or so....and can get away without folding the horn. If I had big dollars and better tools, I'd have it done already, but I've been limiting myself to simple construction methods (and that phase plug requirement gets annoying).

Btw, the Othorn blows away anything that has come out of the Klipsch gates - and that was entirely DIY. I'd be willing to stack that design up against anything that takes up the same volume and covers the same bandwidth - it's just that good. The only piece missing in an ideal 3-way system is that MF unit to go between the Othorn and the HF unit...

I've been stubborn about hitting a 1kHz corner with constant polars so I can use a 1" throat tweeter. Relax that to a 500Hz xover to the K402 and that's already finished. I've also been stubborn about the 80Hz xover frequency - even though the Othorn sounds just fine up to 150Hz or so...

But the short summary is that there will always be compromises...even with that "ideal" system floating around in my head.

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I was directing it towards all the Math geniuses to put all these flaws on a note pad and build something similar with none of them. It AINT happening.

Well I've been working on several approaches for a good 3 years or so.....you're right, it's crazy near impossible to do.

However, I do think an improvement can be made if you only target an LF corner of ~80Hz or so....and can get away without folding the horn. If I had big dollars and better tools, I'd have it done already, but I've been limiting myself to simple construction methods (and that phase plug requirement gets annoying).

Btw, the Othorn blows away anything that has come out of the Klipsch gates - and that was entirely DIY. I'd be willing to stack that design up against anything that takes up the same volume and covers the same bandwidth - it's just that good. The only piece missing in an ideal 3-way system is that MF unit to go between the Othorn and the HF unit...

I've been stubborn about hitting a 1kHz corner with constant polars so I can use a 1" throat tweeter. Relax that to a 500Hz xover to the K402 and that's already finished. I've also been stubborn about the 80Hz xover frequency - even though the Othorn sounds just fine up to 150Hz or so...

But the short summary is that there will always be compromises...even with that "ideal" system floating around in my head.

That's good to hear. Im not going to pretend that I know half of what you guys talk when it comes to the deep math, but I certainly know the struggle to build something not just with a better response, but something that is going to sound good and come in an equal size. PWK, had to make compromises, but all the new "builds" will have to as well as long as we keep them to a single horn cab. I think its a struggle which has no solution and it all just goes back to little low end, but great sound and timing with the LaScala or Timing issues and a fews ugly peaks, which involves the long path of the K cab. IMO, Its going to take two horn cabs to truly pull off an "on paper" better solution of the LS or the K. What we gain in one area, we will lose in another.

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For example, if you tune a guitar you listen for the beat freq of the higher string being off note from the lower fretted string, and the combination makes the F1 (fretted low string) - F2.(high string) put out some low throbbing sound (they may be up around 400 Hz but their difference is low in freq causing the throbbing). When the high string is adjusted to the same freq as the fretted low, the throbbing goes away. This is because F1 minus F2 is reduced to zero. This is because the freqs are the same.

This is to say, if you've ever tuned a guitar, you have utilized intermodulation distortion. (I think the non-linearity comes from the body of guitar.) Therefore, you may say you don't understand this intermodulation theory, but you have used it. Smile.

this "throbbing" you speak of are merely the sound waves interfering with each other as the two tones resonate at different frequencies. it's akin to a moiré pattern in visual terms... as the two frequencies become closer they modulate slower and slower until they are nearly indistinguishable from each other and become "in tune". 440hz for the musically uninitiated as a generalized standard.

If I may take a little issue with Schu.

This arises in my head because of an episode in high school. An English teacher and director of our theater group had a nifty idea which we technical students shook our heads at. His idea was to take two film projectors set at right angles and see if the projected beams caused some interaction making the image on the screens wacky. Of course not. But in retrospect it showed some real original thinking by him.

The beat thing I describe is heterodyning (note "different" in hetero) in a non linear media. Nelson Pass has an equation in his article.

If the media is linear, like air, we can get "interference" which he mentions. This is technically called superposition, which is addition. Even with a single freq there can be the standing wave effect in a room with addition. If the waves are out of phase the negative value causes addition of a negative, which is subtraction. So there can be "nodes" which are the resulting zero relative pressure or anti-node where the pressure from the two waves are in phase and effectively double. However, no new frequencies are created.

I've described the following before but I'll do it again. Put a pure 200 Hz tone into one speaker and walk around the room. At some points it seems like the speaker stopped working because there is near silence. This is interference. You'll never believe it until you try it. No new freqs are created.

When we have a linear media it is like a straight line graph. If you put A + B on the X axis and go up to the straight line (it's linear) the Y axis shows an output of the slope times (A + B) in the time domain.

If the media is non-linear it is often exponential. When we put A on the X axis it translates to some point on the exponential curve. When we add B it gooses the result up to an even higher slope on the exponential curve. This results in multiplication of the result. In radio work, "mixers" are non-linear devices which multiply rather than add. (An audio mixer box only adds) This is in the time domain. In the frequency domain we get an output of A freq and B freq and A+B freq and A-B freq.

These new freqs show up in guitar tuning as I've described because the guitar body or something in not linear. But air under normal pressure does add pressure sources (musical notes) without introducing new freqs.

We know this from experience. It is like things you know but didn't know you know (ahem).

George may be playing an A-440 in the left channel with a perfectly tuned guitar. John is playing an A but his guitar us tuned a little flat at 420 Hz. We don't hear a beat tone in our living room (as we do when strings are not tuned to equal freqs) even if it is not pleasant to have a guitar tuned flat.

Overall, if simple interference (superposition or adding) created new freqs, the music from our left speaker combined with the music from our right channel would create A+B and A-B freqs which would be a total mess.

I just wanted to make that clear.

Smile,

WMcD

Edited by William F. Gil McDermott
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I was directing it towards all the Math geniuses to put all these flaws on a note pad and build something similar with none of them. It AINT happening.

Well I've been working on several approaches for a good 3 years or so.....you're right, it's crazy near impossible to do.

However, I do think an improvement can be made if you only target an LF corner of ~80Hz or so....and can get away without folding the horn. If I had big dollars and better tools, I'd have it done already, but I've been limiting myself to simple construction methods (and that phase plug requirement gets annoying).

Btw, the Othorn blows away anything that has come out of the Klipsch gates - and that was entirely DIY. I'd be willing to stack that design up against anything that takes up the same volume and covers the same bandwidth - it's just that good. The only piece missing in an ideal 3-way system is that MF unit to go between the Othorn and the HF unit...

I've been stubborn about hitting a 1kHz corner with constant polars so I can use a 1" throat tweeter. Relax that to a 500Hz xover to the K402 and that's already finished. I've also been stubborn about the 80Hz xover frequency - even though the Othorn sounds just fine up to 150Hz or so...

But the short summary is that there will always be compromises...even with that "ideal" system floating around in my head.

Blows away anything from klipsch huh?? Another "expert " opinion......

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Well Mike, the KPT-180 uses an 18" active driver and an 18" passive. The cabinet isn't really gigantic at 72" x 48" x 31", though it weighs in at 300 pounds. In the chamber at 1/2 space, it's +/- 3dB, 26Hz-240Hz, with a continuous output of 130dB plus. I think the vented horn thing hangs with the tapped horn thing pretty good. It also probably has less distortion and I have a feeling it probably caves your chest in after it knocks the snot out of you.

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Well Mike, the KPT-180 uses an 18" active driver and an 18" passive. The cabinet isn't really gigantic at 72" x 48" x 31", though it weighs in at 300 pounds. In the chamber at 1/2 space, it's +/- 3dB, 26Hz-240Hz, with a continuous output of 130dB plus. I think the vented horn thing hangs with the tapped horn thing pretty good. It also probably has less distortion and I have a feeling it probably caves your chest in after it knocks the snot out of you.

The KPT-1802 is ported, no passive.

It is huge though for sure.

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Well Mike, the KPT-180 uses an 18" active driver and an 18" passive. The cabinet isn't really gigantic at 72" x 48" x 31", though it weighs in at 300 pounds. In the chamber at 1/2 space, it's +/- 3dB, 26Hz-240Hz, with a continuous output of 130dB plus. I think the vented horn thing hangs with the tapped horn thing pretty good. It also probably has less distortion and I have a feeling it probably caves your chest in after it knocks the snot out of you.

Haha, that's 3x bigger!

Where do you hit the gigantic line in your book?

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From the product page.

An industry-first horn-loaded vented cabinet design

Ported horn loaded. I still haven't quite wrapped my head around that but it's a biggun for sure.

Bill Fitzmaurice has been using ported horn design for some time.

DR200_zps417facf5.jpg

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From the product page.

An industry-first horn-loaded vented cabinet design

Ported horn loaded. I still haven't quite wrapped my head around that but it's a biggun for sure.

Bill Fitzmaurice has been using ported horn design for some time.

DR200_zps417facf5.jpg

Yeah baby, now your talkin my kind of size!!!! YEAH! :emotion-19::emotion-19::emotion-19:

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From the product page.

An industry-first horn-loaded vented cabinet design

Ported horn loaded. I still haven't quite wrapped my head around that but it's a biggun for sure.

Bill Fitzmaurice has been using ported horn design for some time.

DR200_zps417facf5.jpg

Yeah baby, now your talkin my kind of size!!!! YEAH! :emotion-19::emotion-19::emotion-19:

That's the little one in the DR series with a melded piezo array.

Edited by jason str
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From the product page.

An industry-first horn-loaded vented cabinet design

Ported horn loaded. I still haven't quite wrapped my head around that but it's a biggun for sure.

Bill Fitzmaurice has been using ported horn design for some time.

DR200_zps417facf5.jpg

Yeah baby, now your talkin my kind of size!!!! YEAH! :emotion-19::emotion-19::emotion-19:

That's the little one in the DR series with a melded piezo array.

Thanks for the name, iv just spent a little time on the site and bookmarked for futher use, and use it i will, this guys stuff is right up my ally.

  • Like 2
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From the product page.

An industry-first horn-loaded vented cabinet design

Ported horn loaded. I still haven't quite wrapped my head around that but it's a biggun for sure.

Bill Fitzmaurice has been using ported horn design for some time.

DR200_zps417facf5.jpg

Yeah baby, now your talkin my kind of size!!!! YEAH! :emotion-19::emotion-19::emotion-19:

That's the little one in the DR series with a melded piezo array.

Thanks for the name, iv just spent a little time on the site and bookmarked for futher use, and use it i will, this guys stuff is right up my ally.

I agree. I think an active Crown amp and a home built box has my interest now as well.

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I was directing it towards all the Math geniuses to put all these flaws on a note pad and build something similar with none of them. It AINT happening.

Well I've been working on several approaches for a good 3 years or so.....you're right, it's crazy near impossible to do.

However, I do think an improvement can be made if you only target an LF corner of ~80Hz or so....and can get away without folding the horn. If I had big dollars and better tools, I'd have it done already, but I've been limiting myself to simple construction methods (and that phase plug requirement gets annoying).

Btw, the Othorn blows away anything that has come out of the Klipsch gates - and that was entirely DIY. I'd be willing to stack that design up against anything that takes up the same volume and covers the same bandwidth - it's just that good. The only piece missing in an ideal 3-way system is that MF unit to go between the Othorn and the HF unit...

I've been stubborn about hitting a 1kHz corner with constant polars so I can use a 1" throat tweeter. Relax that to a 500Hz xover to the K402 and that's already finished. I've also been stubborn about the 80Hz xover frequency - even though the Othorn sounds just fine up to 150Hz or so...

But the short summary is that there will always be compromises...even with that "ideal" system floating around in my head.

Blows away anything from klipsch huh?? Another "expert " opinion......

Allow me to clarify what I feel are facts and not opinion:

Klipsch claims 130dB at 1m ground plane: and it is a calculated maximum - not measured. Usually that's a convenient way to ignore power compression and claim a big number. But let's take that number at face value...

At 1m ground plane, the Othorn measures 132dB with a CEA - 2010 measurement:

http://www.data-bass.com/data?page=systems&col=7&type=1&sort=desc&mfr=-1

http://www.data-bass.com/know-how (NOTE: Ricci uses a 2m measurement for a variety of reasons, so I added the 6dB to correlate to a 1m spec).

One might even claim 134dB with a more insane driver.

The Othorn dimensions are 2x3x3 feet, which is over 3x smaller than 6x4x2.5. Coupling three Othorns together will net 141dB versus a (calculated) 130dB in the same footprint.

By my measure, that's a 10dB improvement and justifies using language like "blow away".

I'd be all ears if someone from Klipsch comes back with numbers showing greater performance with the same solution size. CEA-2010 numbers would be a great start. I don't want to diminish the genius of the 1802-HLS design, which clearly is doing a lot more with a lot less. However, there's only so much room in the back of the truck, or your living room so I think it is very fair to compare designs that take up the some amount of space. Amplifier power requirements and cost are inaudible traits so I don't worry about them too much if there are existing solutions that meet the needs....

Anyways, that's where I'm coming from. I'm all ears for another way to make the comparison. Is there something about the 1802 that will sound better for other reasons? Obviously maxSPL is a completely arbitrary spec for normal listening, but it does give insight into the potential linearity of a system (generally we see distortion decrease as level is reduced until we hit the noise floor). The Othorn is under 1% THD even all the way up to 110dB....

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