No!! I would just ask all the wrong questions
And upset people, perhaps
No!! I would just ask all the wrong questions
And upset people, perhaps
Ya think?
Naaaaaaaaaaaaaaaaah!
se
I want to talk about horn theory, how it was initially used, and how it evolved, and was generally replaced for home hi fi reproduction, even with the most expensive systems.
Horns were with us over 100 years ago, and the only practical way to get enough level from a portable mechanical phonograph, and even from early AM radios. Around 1925, Rice and Kellog (sp) wrote a fundamental paper that opened up INTELLIGENT DESIGN of the direct radiator speaker. This required math such as: Mx:+ Bx. + Cx = some drive force. They found that if you can get M to dominate, you could have a 'mass controlled' system, normally known as a direct radiator, and get relatively flat response down to the resonant frequency made by the Mass and Compliance of the speaker.
Using a horn was not absolutely necessary, although you would get a lot more acoustical output, if you used a horn in front of the loudspeaker. Of course, this was necessary in many situations like movie theaters, but at home, you just might be able to get away with not using a horn, if they beefed up the audio output stage a bit, which they did. more later
Horns were with us over 100 years ago, and the only practical way to get enough level from a portable mechanical phonograph, and even from early AM radios. Around 1925, Rice and Kellog (sp) wrote a fundamental paper that opened up INTELLIGENT DESIGN of the direct radiator speaker. This required math such as: Mx:+ Bx. + Cx = some drive force. They found that if you can get M to dominate, you could have a 'mass controlled' system, normally known as a direct radiator, and get relatively flat response down to the resonant frequency made by the Mass and Compliance of the speaker.
Using a horn was not absolutely necessary, although you would get a lot more acoustical output, if you used a horn in front of the loudspeaker. Of course, this was necessary in many situations like movie theaters, but at home, you just might be able to get away with not using a horn, if they beefed up the audio output stage a bit, which they did. more later
Mostly churning away for Jan's ezine, will probably skip New Years Eve this year. Too old to party.
It is hard to fix all the holes.
During the '30's there was a revolution in movie theater sound reproduction, for example, in England, USA, and Germany to name three countries. They all built their own horns and direct radiators to drive them. Here, expense was secondary, because it served so many people over a long period of time, and loudspeakers improved. In the USA, by 1950, most of the professional loudspeakers were made by JBL and Altec, and used for PA and movie theaters, everywhere. Other companies made lower cost consumer loudspeakers, and some manufacturers like Bozak made their own version of an expensive high fidelity speaker driver.
There were a few differences between expensive loudspeakers and cheap ones, even IF they pretty much looked the same at a glance. The first thing was magnet weight, but this had to go with a efficient magnetic path to be really useful and effective. Altec and JBL went the extra amount to make an efficient, linear speaker, usually with some 'throw' or back and forth movement more than a small amount. To get 'everything', specs had to be tight, tolerances close, and materials like Armco steel necessary.
Another manufacturer might make a loudspeaker with the same nominal sensitivity, BUT it would not have any 'throw' as the magnetic motor had a limited range, although at midrange frequencies, it might work just fine. more later
There were a few differences between expensive loudspeakers and cheap ones, even IF they pretty much looked the same at a glance. The first thing was magnet weight, but this had to go with a efficient magnetic path to be really useful and effective. Altec and JBL went the extra amount to make an efficient, linear speaker, usually with some 'throw' or back and forth movement more than a small amount. To get 'everything', specs had to be tight, tolerances close, and materials like Armco steel necessary.
Another manufacturer might make a loudspeaker with the same nominal sensitivity, BUT it would not have any 'throw' as the magnetic motor had a limited range, although at midrange frequencies, it might work just fine. more later
John even you are not old enough to talk about this. There actually are some great recordings done totally acousticly. Please allow for some historians of recording history to have a say in these matters.
One of the problems with later Klipsch speakers was Paul Klipsch's decision to use a cheap cone speaker for both his horns and his direct radiators. To be sure, this minimized any generation of FM distortion, but it kept the real bass response very limited. What he should have done would have been to make real sub-woofer speaker with some throw, early on. This would have isolated the FM distortion, without requiring extra movement from the mid frequency drivers.
FM distortion, itself, is virtually eliminated in horns IN THEIR WORKING RANGE but all bets are off, below the horn cut-off.
In direct radiators, FM distortion can be a MAJOR contributor to distortion, yet many here probably do not now how to calculate it or how much of a contribution to distortion it gives in a given direct radiator system. Because of this, we used dozens to hundreds of speakers in parallel to reduce FM distortion in the GD sound system, helped with AM distortion, as well. more later
FM distortion, itself, is virtually eliminated in horns IN THEIR WORKING RANGE but all bets are off, below the horn cut-off.
In direct radiators, FM distortion can be a MAJOR contributor to distortion, yet many here probably do not now how to calculate it or how much of a contribution to distortion it gives in a given direct radiator system. Because of this, we used dozens to hundreds of speakers in parallel to reduce FM distortion in the GD sound system, helped with AM distortion, as well. more later
Yes there are. I've heard some. Amazing what can be done with a good engineering.
Hi John,
The low frequency cut off is always determined by the mouth area of the horn. If you figure out what dimensions you need to cut off at 20 Hz, you'll be looking at a huge horn opening. That's why K-Horns are designed to be mounted in the room corners - the walls of the room extend the effective mouth size.
The entire reason a stiff speaker suspension is used is to match the radiation resistance of the horn at the other end. The horn is similar to the idea of an acoustic transformer where the normally low impedance of the air can be increased to make coupling better to the driver. That is how the efficiency is raised. The resulting reduction in cone displacement required reduced the distortions you are talking about.
I used to do warranty service on K-Horns and have crawled in to a few for service. Blown woofers are not common unless people get way out of hand! The woofer driver wasn't a cheaply made speaker. Not the most expensive to be sure, but it wasn't a low quality speaker.
BTW, the other drivers in the Klipsch speakers were both greatly varied and also not the least expensive woofers I have ever seen. They are actually better than average. Don't forget that they concentrated on efficiency rather than how many watts the VC could absorb. That is a lesson from "back in the day" that we seemed to have forgotten about. If you can generate 100 dB with a couple watts, you've eliminated or reduced several problems, like VC heating that throws off the tuning and reduces efficiency by 2 dB or more. The industry lost sight of the actual goal of the speaker, which is to transform electrical power into acoustic power (with low distortion).
Want to knock a product? Go after Bose. Those are inexpensive drivers. There are many other more deserving brands out there for singling out as cheap woofer drivers. Almost every Japanese system speaker common in retail stores for example. "House speakers" some retailers use are really terrible.
One of the few times I have seen blown K-Horn woofers came from a "dude" that was using a Carver PM-1.5 to drive them. One wonders.
When you talk about all bets being off below the horn cut off frequency, you have to also point out that the same thing is true of all speaker systems. Closed box types don't suffer nearly as much, but ported enclosures really unload the woofer well below the cutoff frequency. Many horn enclosures run the woofer with one sealed chamber, so the woofer isn't unloaded as much as the sound pressure falls into the basement.
You also forgot one of the best speaker companies that was active back in the day. Electrovoice. They had better theater penetration than almost anyone else until recent times. One slogan was "Voice of the Theater" for that reason. In the 70s, they made an awesome 8" for horn duty. I think it ran about $450 each back then (1978 or so).
I'm not an expert, but this much I did pick up from those who made horn speakers their professions.
-Chris
The low frequency cut off is always determined by the mouth area of the horn. If you figure out what dimensions you need to cut off at 20 Hz, you'll be looking at a huge horn opening. That's why K-Horns are designed to be mounted in the room corners - the walls of the room extend the effective mouth size.
The entire reason a stiff speaker suspension is used is to match the radiation resistance of the horn at the other end. The horn is similar to the idea of an acoustic transformer where the normally low impedance of the air can be increased to make coupling better to the driver. That is how the efficiency is raised. The resulting reduction in cone displacement required reduced the distortions you are talking about.
I used to do warranty service on K-Horns and have crawled in to a few for service. Blown woofers are not common unless people get way out of hand! The woofer driver wasn't a cheaply made speaker. Not the most expensive to be sure, but it wasn't a low quality speaker.
BTW, the other drivers in the Klipsch speakers were both greatly varied and also not the least expensive woofers I have ever seen. They are actually better than average. Don't forget that they concentrated on efficiency rather than how many watts the VC could absorb. That is a lesson from "back in the day" that we seemed to have forgotten about. If you can generate 100 dB with a couple watts, you've eliminated or reduced several problems, like VC heating that throws off the tuning and reduces efficiency by 2 dB or more. The industry lost sight of the actual goal of the speaker, which is to transform electrical power into acoustic power (with low distortion).
Want to knock a product? Go after Bose. Those are inexpensive drivers. There are many other more deserving brands out there for singling out as cheap woofer drivers. Almost every Japanese system speaker common in retail stores for example. "House speakers" some retailers use are really terrible.
One of the few times I have seen blown K-Horn woofers came from a "dude" that was using a Carver PM-1.5 to drive them. One wonders.
When you talk about all bets being off below the horn cut off frequency, you have to also point out that the same thing is true of all speaker systems. Closed box types don't suffer nearly as much, but ported enclosures really unload the woofer well below the cutoff frequency. Many horn enclosures run the woofer with one sealed chamber, so the woofer isn't unloaded as much as the sound pressure falls into the basement.
You also forgot one of the best speaker companies that was active back in the day. Electrovoice. They had better theater penetration than almost anyone else until recent times. One slogan was "Voice of the Theater" for that reason. In the 70s, they made an awesome 8" for horn duty. I think it ran about $450 each back then (1978 or so).
I'm not an expert, but this much I did pick up from those who made horn speakers their professions.
-Chris
Would be interesting to see what could be done using current technology.
There'd certainly be no arguing about tubes vs. transistors.
se
It's backwards now, using high efficiency (i.e. class D) amplifiers driving low efficiency loudspeakers.
"Voice of the Theater" was Altec, not Electrovoice.
se
Hi Steve,
I stand corrected. Thank you.
Well, I did see many EV systems in theaters when I was doing Sound and Lighting work. They seemed (EV) to be very strong in that market, but their consumer speaker drivers left me with a very positive impression. So did Altec to be fair.
-Chris
Oops!
I stand corrected. Thank you.
Well, I did see many EV systems in theaters when I was doing Sound and Lighting work. They seemed (EV) to be very strong in that market, but their consumer speaker drivers left me with a very positive impression. So did Altec to be fair.
Pretty much. Now, if they can refocus and do the speaker thing properly. I guess that due to large enclosures and shipping issues, there will be no returning to common sense anytime soon. The car audio market is the one place where speaker technology seems to be chasing down the wrong path.
-Chris
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Anatech, I have taken my own K-horn apart. The Eminence $15 driver did NOT have a stiff compliance, it just had a 1:1 winding to magnetic path that pulled the bobbin out of the magnetic field during movement and reduced the excursion. I put the SAME woofer from my k-horn in a jbl test box and compared it to similar JBL loudspeakers that we used in the wall of sound. The difference was staggering.
Later, as a consultant for an other PA company, I tried to get Eminence to make us a custom PA speaker to save the cost of buying JBL's. They could add all the magnet that we ordered, but no 'throw' could be added. It is just a construction restriction that is based on maximum efficiency for lowest cost. For throw, you have to over-wind, under-wind, or at least widen the magnetic thru-path. This is expensive and requires more magnet, Armco steel, etc to get efficiency back to something useful.
Later, as a consultant for an other PA company, I tried to get Eminence to make us a custom PA speaker to save the cost of buying JBL's. They could add all the magnet that we ordered, but no 'throw' could be added. It is just a construction restriction that is based on maximum efficiency for lowest cost. For throw, you have to over-wind, under-wind, or at least widen the magnetic thru-path. This is expensive and requires more magnet, Armco steel, etc to get efficiency back to something useful.
It is not my intention to add other speakers into the equation at this time, because nothing new will be learned, and I would like to give my experience first, before we go on. In any case, what happens in a real situation, with a loudspeaker operating at high input levels with a horn, below its cutoff, is what I am most concerned about here.
We all know that horns limit driver excursion within the bandwidth of the horn, either because the output is so high, that you normally turn it down, and even if you don't, the driver excursion operates with 1/f rather than 1/f(squared) and the speaker does not have to move as much at low frequencies.
However, John Meyer once told me that he put a plexiglas port on a Klipsch LaScala horn system and noted the cone movement during a live performance. He said that the cone was very stressed by input under the loudspeaker cutoff. Why don't you ask him about it, if you have any questions?
We all know that horns limit driver excursion within the bandwidth of the horn, either because the output is so high, that you normally turn it down, and even if you don't, the driver excursion operates with 1/f rather than 1/f(squared) and the speaker does not have to move as much at low frequencies.
However, John Meyer once told me that he put a plexiglas port on a Klipsch LaScala horn system and noted the cone movement during a live performance. He said that the cone was very stressed by input under the loudspeaker cutoff. Why don't you ask him about it, if you have any questions?
No problem.
Well, I did see many EV systems in theaters when I was doing Sound and Lighting work. They seemed (EV) to be very strong in that market...Oh absolutely.
And they also did well in the instrument speaker market. You were either a Celestion fan or an Electrovoice fan.
And let's not forget Western Electric who was there at the very beginning.
Naaaaaaaah. Not for any broader audience anyway. And the mass market seems quite content with 2 inch speakers with 5 inch "subwoofers."
That market is just insane.
se
Ed,
3rd harmonic is about 3-5x more audible, than the 2nd. You can make your own test easily, and you will hear the 3rd of 0.X%.
Regarding "In a musical reproduction system I expect -20 of second harmonic may be heard, possibly -30", I doubt that high numbers. I was also thinking that some -50dB of the 2nd would be inaudible. But, comparative listening tests performed on amplifiers with something like 0.0X% CCIF IMD (19+20kHz) and 0.00Y%, with complex orchestral classical music, show that 0.0X% is audible. You would probably not hear harmonics only, but the intermodulation products are audible. Some like it hot, as they apparently 'smooth' the resulting sound, but worsen resolution.
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Not just in one. The flagship SP-10 also used the little horrors for muting. On top of distorting they also didn't last very long.
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