Audiolics Anonymous Chapter 21
Beauhorn and Border Patrol
Article by Bill Gaw
Click here to e-mail reviewer
Welcome to another meeting of our wild and crazy group of
tweekaholics. Back in
Chapter 19, I did a review of a new system that my good friend, Kwami Ofori-Asante had purchased. As the system sounded wonderful, I decided to review the individual pieces to see if it was the system, or the individual components that were important. Last
month in Enjoy the Music.com Audiolics
Anonymous 20, we began the review, bringing the Audio Note phono cartridge and interconnect into my system, and ended up buying them.
Today, I'm finishing up with a review of the Beauhorn, from Thomas Transducers of Hastings,
England. They are Lowther based speakers of an unusual design, using both a front and rear horn, and using the biggest phase plug you have ever seen, I mean one very manly plug.
Why two horns; a front mid and rear bass? Up till now, Lowthers have been primarily placed on the flat front surface of a rear horn cabinet, using the Lowther's high sensitivity from the mid range up, balanced with the rear loaded horn gain for the bottom end. The problem with this set-up is that the Lowther's have a natural peak in their frequency that sometimes gives a honkiness to the sound. Also, it is difficult to match the gain of the rear loaded bass horn with the output of the front mounted driver. Also, there is a time alignment problem between the two outputs that leads to some combing artifacts.
Each company has used some form of kludge, either a second whizzer cone or a phase plug, to try to eradicate these problems. The most successful that I had heard, was the
Rethm horn, which I listened to at the last CES. It uses a second whizzer cone suspended outside the original Lowther whizzer and a transmission line for the rear firing bass. While it got rid of most of the honkiness of the Lowther, it still left a little of the bass to mid discrepancies.
The Beauhorn's design is based on an all wood cabinet measuring 13 x 41 x
26" and weighing in at 78 lbs. each. They are finished in either maple or cherry veneer. Both the front mid and rear bass are elliptical
horns and having straight walls. The large wooden phase plug appears to have a tractrix contour, weighs several pounds,
is finished in the same wood and stain, and screws into the cap area of the Lowther. The inside of the cabinet is lined with some thin Styrofoam, and the speaker posts are gold plated and solid. The speaker can be configured with any of several of the different Lowther drivers, but Steve Klein imports only the top of the line DX4 drivers. They claim a frequency range of 50's to 20 kHz.
Advantages of Lowther speakers:
1. Very wide frequency range. If not driven too hard, the Lowther's can be run from 50-20,000
kHz. In other words almost full range. Thus they are one of the few drivers that can cover the whole frequency spectrum except the mid and low bass. This has the advantage of no discontinuity in the sound that multi driver speakers all have.
2. No crossover required unless a subwoofer is used. This is a necessity if one listens very
loudly or to music with significant deep bass.
3. Very high efficiency driver. Having a very light paper cone with massive magnets gives the driver an efficiency of about 100 dB, and combining it with a horn adds another 4-6 dB. The light cone and heavy magnet also give tremendous speed and control to the cone motion, giving a very
accurate and low distortion sound.
Disadvantages of Lowther speakers:
1. Poor bass performance. To get anything below 50 Hz. a subwoofer is a must. Also if the cone is driven too hard to obtain bass, distortion rises even in the upper
frequencies. If pushed hard enough the cone can be torn from its attachments! Then it doesn't sound quite as good.
2. Honkiness. I don't know whether it is a product of the main cone, or the whizzer cone used to extend the frequency range, but there is a honkiness which I have heard on almost every Lowther speaker I've auditioned. Its not a major distortion, but once
heard cannot be forgotten.
3. Long break-in time. This driver has got to have the longest break-in time of any driver out there. One can hear changes in sound a year into its use. This may be why some of the older units have a mellower tone than the new ones. Or it may be that the older units used Alnico magnets, which are known for their more natural tonal color.
4. Very narrow gap between cone and magnet. Any misalignment and the former will rub against the magnet, giving horrible distortion. This can occur if the cone is overdriven, but may also occur on a brand new unit. Sometimes, the factory has not been very fastidious in checking drivers before they are sold. This is obviously not a problem when one buys a complete speaker as it is the manufacturer's responsibility to check the driver.
Advantages of the Beauhorn:
1. Cabinet is very well constructed. On all six units I saw, fit and finish were superb. I worked in a furniture factory for two summers in high school, and with a trained
eye I could find no fault in construction. As an added bonus they have a Bau-art sort of style that should be pleasing the
L.O.L. (little old lady). Each has four spikes which should be left off until speaker placement is firmed up, as they are shaped like 16 penny nails, and could do a job on the floor or carpet. Also, for solid
floors you might think of putting a coin under each to prevent floor gouges.
2. Light. These things weigh only 78 pounds each so you don't need weight lifters to position them in your room.
3. Both rear and front horn loading. This should add to the continuity one hears from the Lowther since the driver is loaded the same front and back. Theoretically pressure should be equal on both the front and rear side of the driver, cutting distortion further, and the gain of the horns on the drivers efficiency should be equal.
4. Time alignment. Because of the shape of the speaker, and the use of two horns, the distance between the front and rear horn mouths are closer to equidistant from the driver to the listener, so this should ameliorate some of the time alignment problems that a rear loaded Lowther has.
Theoretical Disadvantages of the Beauhorn:
1. Light cabinet. The cabinet does not pass the knuckle rap test, singing like a drum. Some people like this in their
horns as it adds some even harmonics to the sound, but I think a speaker should be neutral. This can be very easily solved by adding some weight to the cabinet tops. Kwami used some Elephant
feet while I used some 25 lb. bags of lead shot. Both worked to cut down on cabinet resonance.
2. Conical mid horn. An Conical curve horn is much easier to build than any other horn since one can use flat
walls and this does not seem to matter in bass horns with long wave lengths, but in mid-tweeter
horns I think they are much more colored than a Tractrix curve. I find it interesting that the phase plug looks to have a
Tractrix contour and think this speaker would sound even better if the front horn curve matched that of the phase plug's...
plus it would look much more elegant. Would it make a difference with this speaker's sound. I don't know, but would love to find out. There's the
tweaker in me again.
3. Rear horn walls free of sound absorbent. One problem with a rear horn connected to a front horn is that both are reproducing the whole signal. Thus the mid range may show some smearing and combing. Again, while I don't hear this with the
Beauhorn, probably because they have placed the double mouth venting to the back sides, I wonder if placing some Sonex in the rear chamber might improve the sound by getting rid of the mid-upper frequency information coming from the rear. (See,
there are two tweaks already that one could try.)
Previously, I had heard the speaker in two other systems at Kwami's and Steve Klein's
(US distributor) house. The systems were similar with most equipment the same and was very favorably impressed with the sound. So I asked Steve to let me review a pair in my listening room. He obliged and brought them over, unhappily at a time when I had to be at the hospital, so he placed them in the front of the room next to the mouths of my bass horns, about a third of the way out in the
room and left final setup to me. So I took my trusty home-built 2A3 monoblocks with cobalt transformers and Vaic tubes and sat down for a listen.
Horrors! The sound was atrocious. It was glary with absolutely no
bass and the Lowther honk was there in spades. My computer speakers sounded better. Were these the same speakers I had loved? Did my equipment suck? Was there some major anomaly between the speakers and the amps?
Then I thought... could it be room placement? They were in the golden spot of 1/3rd out in the room, but they were right next to the mouth of my bass horns. Could that be the problem? I certainly
was not going to move my 900 lb. horns to see, and the rest of the front of the room was cluttered with center speaker, equipment, etc. So I decided to try the back of my room, which only has four surround horns placed way in the back and into the corners. Then I had to decide whether to run long interconnects or speaker cables. This was a problem since I
do not have any long speaker cables and the only three meter interconnects I had were
ten year old Distech silvers which were great in their day, but not top of the line now. I therefore called Steve and suggested he come over and help me with setup, which he agreed to do the following weekend.
While waiting I began to experiment. At first I used the rule of 1/3rds for placement, placing them out into the
room. There it was! The same sound stage I had heard at Kwami's. Gone was the honkiness and stridency, and in its place was the best sounding Lowther based speaker I have heard, even more coherent than the
Rethms. This, while using outdated long interconnects that had to have detracted from the sound. The only problem I had was in the bass. Out in the room, the stage extended laterally beyond the
speakers and back several feet. They presented the same massive amount of air I had heard in the other two systems. But there was almost no bass below about 60 Hz, and thus the presentation was lightweight, giving the appearance of a tipped up high end.
Next I placed the speakers as close to the corners of the room as possible. What does that do? The size of a horn's mouth and its length determines how deep the horn will produce sound before it begins rolling off. Thus to get bass, the horn has to be long and big. For a 20
Hz note for instance, about 20 feet long and 10 feet square. Obviously this can present problems if one wants to sit in the room to listen. Each wall the horn is placed against acts as a mirror thus increasing the relative size of the mouth. Thus, if one knows that the horn will be built into a corner, one can decrease the size to
1/8th of its theoretical value. If against a wall an floor, to 1/4. Disadvantage to this is that the mid and high frequency information is also bouncing off of that
wall giving combing artifacts and narrowing and flattening the soundstage. These speakers are built to be placed out into the
room but appear to have a mouth area equivalent to a 1/8th horn, thus the weakness in the bass compared to my true 50 Hz horns, which have a
3x4 foot mouth and are truly flat to below 50 Hz... and have a zero WAF.
And indeed I gained about 10 Hz of response down to the mid50s, although still not as full as the bass produced by mine. But the back of the sound stage shortened to just behind the speakers, giving a flatter and narrower image. Then I got some 3" Sonex
(tweak #3 for the day) and placed a sheet on the walls lateral and behind the mid horn mouth. This expanded the stage almost to where it had been with the speaker in the middle of the room while retaining the bass. Finally, I turned on my subwoofers, two of which happen to be in the rear corners and adjusted their output to the Lowthers. There it was. Almost the same quality of sound that I had heard at Steve's, minus some of the clarity.
Then Steve came over with his Audio Note interconnects, speaker cable and Border Patrol 300B amps from
England (probably the best sounding SET amp I have heard). Review to follow in a few months if I can beg one away from
Steve. While not completely equaling the sound I get from my system, this was the next best sound I have heard from a stereo
system (of course mine sounds best!). The WAF (Wife Acceptance Factor) is infinitely
higher as these speakers actually look great compared to my 6 foot horns. Even I have to admit that. The only thing missing was the low and mid bass presence that the six foot horns give to orchestral music. The soundstage, I have to admit, was
cleaner and more open with a stage larger than with my Edgar Horns (i.e. the soundstage to die
Would I buy these guys at $8,500 a pair? Most certainly. Would I buy five for a super surround system at
$42,500, with another $3,000 for subwoofers? Yes if I wanted superb surround sound using SET
amps comparable to anything you would get from the best home theater speakers, with the advantage of the best in stereo reproduction. Have I done it: thrown out my
seven horns and bought the Beauhorns? No. For the first time in my high end audio
life I have resisted temptation. I am proud of myself. Fellow Audiolics, I have been saved from that Son Satan, Steve Klein, the Tempter who has forced upon me those toys of the devil. How did I do it. By throwing Steve and his damn speakers and amps out of my house that very day, and not letting them back. Did I almost succumb? Yes. This weekend when I went back over to Kwami's to test an amplifier for
review and heard them again. But I swear I will not let temptation strike again. Kwami's and Steve's listening rooms are off limits as of today. Did I get horny over the
Beauhorn? You betcha.
So what have I learned from the past three columns?
First, each component is important, with the most important and most easily distorted being the transducers (cartridges and speakers) and moving
components (tonearms, turntables and CD players).
Second, the components have to be synergistic (i.e. they must work together and complement each
other). Horns will not sound great with megawatt speakers. Low compliance cartridges work poorly with light tonearms and vice versa. Three, get the best dealer you can with the most experience and squeeze him dry of knowledge, then pay him a fair amount for his services. Try for the discount, but stick with him and not go to a discounter once
you have gotten the information.
Next month's article will be early as Enjoy the Music.com
has asked me to cover the EMAP/Stereophile Home Entertainment Show in New York. I know, just two month's ago I swore I'd never go to another show, but that's what happens to Audiolics. Oh well, at least they
will not be selling product, at least I hope not for my bank accounts sake.