Drew Daniels was one of the highest regarded engineers at Altec Lansing and JBL. His home speakers used a horn loaded compression driver tweeter that mated to a 10" cone midrange and two 15" woofers in a BR cabinet. Here are his comments.
"THE MAGIC HORN FIX
There are some tricks that are essential for eliminating horn "honk." The first is to use the cone driver placed just below the horn, all the way up to a frequency where it begins to "beam" due to the relationship of sound wavelength and cone diameter. At a frequency where the resulting Q-factor (directivity) of the cone matches that of the horn, the transition from cone to horn will be smooth, and not abrupt-as it can be in systems where the cone is too large and the horn is too small. If this condition is met, and the frequency response of the cone is good well beyond the frequency up to which it is used (a well-behaved upper end rolloff), then the horn will enjoy a seamless transition from the cone and will not honk, assuming its frequency response is good and uniform over its output angle. This latter condition is referred to as being "power-flat" and is very important to the transparent operation of the speaker system in rooms, with their concomitant acoustic implications. If the speaker system is power flat, the sound in the room will be as good as that particular room will allow it to be.
THE MIDRANGE
The midrange driver must be a cone, unless you live in a theater and don't mind a 4-foot high horn (I crossed my mid at 300 Hz into the woofers). As it turns out a mid cone supplying 300 Hz to 1200 Hz gives the proper effortlessness with very little power, and thus has extremely small cone excursions and low distortion. As I mentioned earlier, I had to trim the 2123H mid cone back 10 dB on the amp's gain control to get the response through the band flat. The power absorbed by the mid cone driver amounts to milliwatts most of the time, which helps to hold harmonic distortion to very low levels, typically well below 1% THD up to dangerously loud volume.
I experimented with a dozen midrange drivers before I was confident that the 2112H with its high efficiency and limited excursion linearity would produce sufficiently low distortion. It is a wonderfully transparent driver and a large part of the reason this speaker system sounds like listening to live music rather than loudspeakers.
The driver is mounted on the baffle as close to the horn as I could get it with my inexpensive mid chamber geometry. You could do better if you are willing to cut the shape of the mid driver's frame into the lower lip of the horn and snug the mid frame up into the cutout and, of course, figure out a mid chamber arrangement that would clear the horn and driver behind the baffle, but this is not measurably better than just a touching fit.
The enclosure for the mid cone consists of a 10-inch diameter concrete casting tube made of plasticized paper. Such tubes are made by Burke Tube and Sonotube and no doubt many other regional paper products manufacturers. The tube is mounted to the baffle by gluing into a counter-bored shoulder cut-out, routed in the back of the baffle around the mounting hole. The tube is about 12 inches long (deep), it is filled completely but loosely with a "jelly roll" of unbacked fiberglass house insulation cut from a roll about 4 feet long. The back end of the tube is sealed air-tight with a disc of 1-inch thick medium density fiber board-the same material used to build the rest of the box."
A dome tweeter could not match the directional dispersion pattern of the 10" midrange, and this would put different levels of direct power and reflected power at the listener - a small sweet spot. If the tweeter horn is a CD with the same width as the midrange, and generated 90 degree horizontal dispersion, it will provide seamless CD radiation - a wide sweet spot.
Domes seem limited to 95 db/watt SPLs. Above this efficiency, compression drivers or ribbons(planars) are required. Ribbons are more challenged to deliver wide vertical dispersion, but new solutions are looking promising.
"THE MAGIC HORN FIX
There are some tricks that are essential for eliminating horn "honk." The first is to use the cone driver placed just below the horn, all the way up to a frequency where it begins to "beam" due to the relationship of sound wavelength and cone diameter. At a frequency where the resulting Q-factor (directivity) of the cone matches that of the horn, the transition from cone to horn will be smooth, and not abrupt-as it can be in systems where the cone is too large and the horn is too small. If this condition is met, and the frequency response of the cone is good well beyond the frequency up to which it is used (a well-behaved upper end rolloff), then the horn will enjoy a seamless transition from the cone and will not honk, assuming its frequency response is good and uniform over its output angle. This latter condition is referred to as being "power-flat" and is very important to the transparent operation of the speaker system in rooms, with their concomitant acoustic implications. If the speaker system is power flat, the sound in the room will be as good as that particular room will allow it to be.
THE MIDRANGE
The midrange driver must be a cone, unless you live in a theater and don't mind a 4-foot high horn (I crossed my mid at 300 Hz into the woofers). As it turns out a mid cone supplying 300 Hz to 1200 Hz gives the proper effortlessness with very little power, and thus has extremely small cone excursions and low distortion. As I mentioned earlier, I had to trim the 2123H mid cone back 10 dB on the amp's gain control to get the response through the band flat. The power absorbed by the mid cone driver amounts to milliwatts most of the time, which helps to hold harmonic distortion to very low levels, typically well below 1% THD up to dangerously loud volume.
I experimented with a dozen midrange drivers before I was confident that the 2112H with its high efficiency and limited excursion linearity would produce sufficiently low distortion. It is a wonderfully transparent driver and a large part of the reason this speaker system sounds like listening to live music rather than loudspeakers.
The driver is mounted on the baffle as close to the horn as I could get it with my inexpensive mid chamber geometry. You could do better if you are willing to cut the shape of the mid driver's frame into the lower lip of the horn and snug the mid frame up into the cutout and, of course, figure out a mid chamber arrangement that would clear the horn and driver behind the baffle, but this is not measurably better than just a touching fit.
The enclosure for the mid cone consists of a 10-inch diameter concrete casting tube made of plasticized paper. Such tubes are made by Burke Tube and Sonotube and no doubt many other regional paper products manufacturers. The tube is mounted to the baffle by gluing into a counter-bored shoulder cut-out, routed in the back of the baffle around the mounting hole. The tube is about 12 inches long (deep), it is filled completely but loosely with a "jelly roll" of unbacked fiberglass house insulation cut from a roll about 4 feet long. The back end of the tube is sealed air-tight with a disc of 1-inch thick medium density fiber board-the same material used to build the rest of the box."
A dome tweeter could not match the directional dispersion pattern of the 10" midrange, and this would put different levels of direct power and reflected power at the listener - a small sweet spot. If the tweeter horn is a CD with the same width as the midrange, and generated 90 degree horizontal dispersion, it will provide seamless CD radiation - a wide sweet spot.
Domes seem limited to 95 db/watt SPLs. Above this efficiency, compression drivers or ribbons(planars) are required. Ribbons are more challenged to deliver wide vertical dispersion, but new solutions are looking promising.
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I cross at 1khz (24db LR, drivers down -6db at crossover point).
Ideally you cross a 15" at near 800hz (90 degree dispersion), but my ears like 1khz.
The system is loud, clean, and very fun.
Mids are very good, but they can be improved by turning it into a 3-way. My crossover has an 18db 80hz selectable switch that really cleans up the mids when there is lots of bass, but 95% of the time, 2x15's and horn are plenty for me.
But this is using one of the best horns (ev hr90) with a great compression driver (ev dh7) with cd-eq on.
To my ears, I found you have to match the dispersion plot of the horn to the crossover frequency. And a steep crossover will allow you to run closer to your minimum. Since my horn is 13" tall, it loses its pattern control below 1khz. Yes it is deep enough for 1/4 wavelength much lower, and yes it has enough mouth area to cross lower, but it sounded worse (10' away) as the crossover point was moved down. Jbl theater stuff is almost 3' x 3' and one was crossing 24db at 630hz. Yes you can cross lower, but now you lose volume because the directivity is no longer loading (free horn boost).
Norman
Ideally you cross a 15" at near 800hz (90 degree dispersion), but my ears like 1khz.
The system is loud, clean, and very fun.
Mids are very good, but they can be improved by turning it into a 3-way. My crossover has an 18db 80hz selectable switch that really cleans up the mids when there is lots of bass, but 95% of the time, 2x15's and horn are plenty for me.
But this is using one of the best horns (ev hr90) with a great compression driver (ev dh7) with cd-eq on.
To my ears, I found you have to match the dispersion plot of the horn to the crossover frequency. And a steep crossover will allow you to run closer to your minimum. Since my horn is 13" tall, it loses its pattern control below 1khz. Yes it is deep enough for 1/4 wavelength much lower, and yes it has enough mouth area to cross lower, but it sounded worse (10' away) as the crossover point was moved down. Jbl theater stuff is almost 3' x 3' and one was crossing 24db at 630hz. Yes you can cross lower, but now you lose volume because the directivity is no longer loading (free horn boost).
Norman
Cones up to about 1k and CD's above that.What do people here prefer, compression drivers or high-eff cone drivers for mids and up? And why so...?
I have used the 2" BMS 4592 ND for a quite a while on two different horns. It has impressive bandwidth, all the SPL and dynamics you could ever want in a home environment, but I must admit that I never got it to sound as natural as I would have liked. In my experience it had to much sibilance in the app. 2-6 kHz range.
I know that Bert Doppenberg from BD-Design has modded the driver in a way that should have made it sound better, by that's beyond my skills.
The 2" Community M200 was to my ears more relaxed and open sounding than the BMS coax in the mids, but covers much less bandwidth, and the 1" B&C DE25 sounded better in the highs than the BMS coax.
Still, I now prefer cones to compression drivers in the mids.
Best regards
Peter
the m200a is better, the peak past 4khz is lower due to the shape of the phase plug / magnet. Avantgarde uses that driver (and they used the m200) but changed the voice coil impedance for matching.
I believe you can get a group of 4 m200 drivers plus big horn for outside mounting for a reasonable price, then sell a pair at cost to a friend that likes your system.
Norman
I believe you can get a group of 4 m200 drivers plus big horn for outside mounting for a reasonable price, then sell a pair at cost to a friend that likes your system.
Norman
oops!
better that any!I ordered Radian 950. I havn't find home system with large drivers\horns to listen various drivers nearer 1000 km. and I can't purchase several pairs
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