Okay, the gloves are off. Let the fur fly

Twl, given some of the responses here, i'm going to start another thread. It is related to the comments here but is somewhat of a different subject. As such, i don't want to dilute this one too much or steer it completely off course. Look for one titled "SPL, dynamics and bottom end". Sean
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Please keep in mind that i am a fan of "single driver" or "point source" designs and own two such speaker pairs. However, being the realist that i am, i can not overlook the flaws that go along with ANY design. Nor should i think that there are only benefits to that design just because i happen to like that specific product or concept.

The basics that any speaker systems have to work with include mass, transient response, radiation patterns, resonances, impedances, output levels, Xmax ( maximum excursion capabilities ), damping / suspension characteristics, etc... One can not achieve the necessary traits with high accuracy in all of the aforementioned categories within the audible frequency range using one driver. As such, the end result of a design that tries to do so is simply a matter of selected trade-offs.

Deep bass requires large surface areas to move a lot of air and mass to achieve a low resonance. It also requires long excursion. What it takes to achieve extreme high frequency response is completely contradictory to those requirements. Clean treble response requires small surface areas to minimize beaming and low mass to respond quick enough for good transient response. Since very short and rapid excursions are what is required for high frequency reproduction, a driver that is simultaneously trying to make large excursions to cover the bass range will end up fighting itself. The end result is distortion. Measurements show that THD, IMD and several other types of distortion sky-rocket to various levels when this takes place.

Trying to achieve excellent results in one area of the audible spectrum over the other ranges results in an unbalanced approach. This is therefore not acceptable to most avid audiophiles. One can achieve a good balance of many of these attributes, but this requires compromises in almost EVERY area of performance. The normally chosen path is a driver that works best over a wide frequency range but not have to cover the extremes with as much finesse.

The end result of almost all of these designs is exactly that. A point source that sounds quite fabulous over the upper bass / lower midrange, up through the midrange and into the lower treble. If one tries to push deep bass out of something like this, the necessary excursion tends to create a "warbling" or "tremolo" effect at upper frequency ranges. This becomes far more apparent as volume levels are increased. On the opposite hand, if one expects "purity" out of the top end, then the driver must be excursion limited and this hurts bass.

As such, if one is willing to live with phenomenally seamless midrange response that is very liquid and coherent at the expense of deep bass, extreme highs and limited SPL capabilities, a single driver system may be for you. Otherwise, you'll have to choose what is acceptable to you in terms of other trade-offs and go that route. Sean
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Herman, what driver is used in a Lamhorn ? Is this a Lowther based unit or something similar ? I've read about them but can't remember the specifics.

I forgot to add that the single full range driver that i'm using will reproduce a 5 Hz signal up to appr 17 Khz tone with reasonably linear amplitude. Unlike most "full range" drivers, it can and easily does shake the floor with great authority. I found out about the "5 Hz response" when playing the Ayre Acoustics disc that was mentioned in another thread. The Cardas sweep tone starts out at 5 Hz and progresses up from there. Needless to say, i was amazed to see the driver responding at all let alone easily throwing back and forth at that rate.

In terms of frequency response irregularities, room loading is probably responsible for most of that. You see, this driver radiates in a 360* horizontal pattern so cancellation and reinforcement become critical in terms of measurable frequency response and output levels. Before you consider the omni pattern and room loading characteristics a drawback, take into consideration that it also produces the widest and deepest soundstage possible. Not only that, it also reproduces notes in a fashion that resembles most acoustic based instruments.

There are four major problems with this design:

1) It takes a very muscular amp to get it moving and keep it under control. It operates at under 2 ohms at very low frequencies. As such, you need an amp that is very low in output impedance in order to maintain a reasonable damping factor. You also need an amp that can produce sustained amounts of high voltage and current to keep the driver under control and deal with the higher than average amount of reflected EMF.

2) It is definitely limited in terms of absolute SPL and dynamic range. Some may say that it plays plenty loud ( fans of chamber music, mellow jazz, acoustic recordings, female vocalists, etc... ). As such, the more that you increase the average listening level, the less dynamic range you have above that point. In plain English, the driver will go into compression on peaks. It can play rock and very dynamic classical recordings so long as you don't ask for extended periods of high listening levels. If you do, the driver begins to produce signs of distress.

3) Since the speakers are in-efficient and a tough load to begin with, you need to throttle them with power to get reasonable SPL's out of them. If you try to squeeze a little more out of them, not only is it pretty demanding of the amp, the driver begins to saturate, overheat and "warble" profusely. As such, you have a somewhat limited window of operation with them.

4) The drivers are no longer made. As such, it is tough finding someone to work on them and do it right. This obviously tells you that they should not be abused in the least if you like them and want to keep them around for any amount of time.

With all of the above taken into consideration, if one can live with listening at low to medium levels, they sound fantastic if fed a high quality signal. After all, there is nothing to get in between you and the sound made by the system in terms of coils, capacitors, impedance compensation networks, notch filters, time and phase delays, etc... that one finds in many "high tech" speakers. The low volume constraint really isn't such a big deal, as it is one of the few speakers that maintains tonal balance regardless of listening level ( so long as you're below the point of saturation ).

All of the "good points" about this design FAR outweigh the "bad points" mentioned above. That is why i own two pairs and have publicly stated that i will never part company with them. Sean
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Danner, thanks for the story. I find it to be quite believable. Only two problems though:

1) Crown amps are great for pro sound, but they typically just don't sound "good" : ) At least your test method ruled out a LOT of variables.

2) Dahlquist speakers are not "realistic". You can only get those from the Tandy Corporation : )

Sean
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Greg, now you're getting somewhere. One can correct a lot of the problems of a multi-way system simply by getting rid of the passive crossovers or at least minimizing them down to the bare essentials. This is what Israel Bloom does with the Coincident's.

However, one still has to look at how the individual drivers will sum at a specified distance, play with their positioning on the baffle and then study the lobing / cancellaton / reinforcement that takes place. Then re-position accordingly and study some more until you've got everything as good as you can. This becomes even more critical if you aren't using any crossover at all, since you now have to select drivers that will have complimentary frequency response curves and roll-off rates. VERY tough to say the least.

To take things one step further, you can remove ALL electronics from between the speakers and use an active crossover. This gives you direct drive ( just like an amp driving one driver ), greater efficiency from the amp, FAR more detail, impact and lucidity than with a passive crossover, etc...

Then all you have to do is make sure that you've got all your amps gain matched, use good quality amps and crossover, take into account the lobing and positioning of drivers, etc... This is a LOT of work, but it is also probably the highest fidelity that your going to achieve if done correctly. Obviously, this is strictly my point of view and others may / may not agree. Sean
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