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I thought some here may be interested in the first complete speaker that will be offered by Lambda Acoustics. At 7' tall and ~ 450 lbs. each, they aren't for the faint of heart, but they won't be anywhere near as hard on your amplifier as they are on your back at 99dB to 102dB depending on the impedance of the system. I have my Unity Horns operational now, but still working on covering below 300Hz.Mark Seaton
Follow Ups:
How does it work?Mike
Ummmm... I presume you are reffering to the Unity horn implementation since you didn't specify. Below is a link to the Proffesional products that use the technology and the company Tom Danley works for(Servodrive is the same people).I am by no means an expert on horns, so I'll do my best to explain the basic idea, recalling from my chatting with Tom Danley and an explanation he made to the BASS list a long while back. First, the Unity horn is not really a single product per-se, but rather a type of implementation of a multi-way, common horn, co-axial design.
As a little background, the idea came from a joking comment made to Tom about making a speaker out of a pyramid, as he had just been sent out to the great pyramids to perform measurements of their acoustic properties for a documentary. Well, if you put a Constant Directivity (CD) horn on it's face, it looks like a pyramid :-). As Tom explained to me, CD horns generally sound quite good, yet they only load a driver for a limited bandwidth due to their increasing rate of expansion. From this fact, you see most CD horns for tweeters with limited bandwidth. What Tom essentially did with the Unity was to "stack" multiple CD horns. Each section of the horn further from the throat is used to load the frequencies which it's profile suits. The tweeter is a compression driver which loads conventionally into the throat of the horn. Then, a few inches from the throat, the 4 midrange drivers are compression loaded into the horn through 8 critically placed holes. The profile of the horn from this point out to the 16.5" square mouth loads the midrange driver allowing response down to ~300Hz.
The use of 4 midrange drivers makes for a midrange system of about 110dB/1W when passively corrected, and a power handling of 100W RMS. As you can see with the various iterations available in kit form, the compression driver is the limit of the system efficiency above 300Hz. Since the midrange is not loaded all the way from the throat of the horn, this configuration also greatly reduces throat SPL levels which in some horns can get high enough to cause distortion from the non-linearities of air. Likewise, the 2 sources are phase and time aligned when an appropriate crossover is used. The point source nature of the horn also has some serious benefits in the axial response, which I have seen measured as near perfect over a 25 deg. window, and tightly controlled within a 60 deg. window. Like other horns, you can imagine the lack of early reflections has a great effect on the sound in a room.
I wish I had more time to talk about this concept which I am so fond of, but back to work for me...
More later,
Mark Seaton
Hi Mark -big boxes! - I'm looking forwards to the TD15 woofers - any idea of what he final specs, real world performance and price will be? I'm thinking "fat Karlson" with good 15" to replace my 18" boxes
Freddy
Freddyi-The speakers pictured use 4 of the TD 15 series woofers on the front face with 4 15" PRs on the back. Nick's been working on the TD woofer for a while now, and has finally given out some specs for 2 of the iterations via e-mail. I'll post them later when I dig them up. Right now there is one model with about 94dB eff. and another version of the same driver with a well placed 40g of mass loading that brings efficiency down to ~92dB for those wanting nicer F3 numbers.
With that monsterous aluminum phase plug, and all the other features in the motor, it has proven to be VERY good at dissipating power. When Nick tested it at ~200W RMS for over an hour, he returned to find the phase plug idling at over 140 deg. F! Much more importantly, the DCR of the driver had only shifted ~10%! Nick will also be making a very high efficiency version with an accordian surround and shorter Xmax, and I hear he has his sights on 99dB+.
Obviously everyone here likes the ideal of high efficiency, but with the thermal performance this woofer has been doing, it could make the 92-94dB drivers easily enough for most people. For those who have a very high efficiency top end to their system, and can't fit closet sized bass horns, this could be a really hot option to fill in the bottom end when equipped with some moderate power.
My Unity speaker will eventually have a pair of TD 15 woofers in a sealed box underneath each Unity horn. The F3 should be around 65Hz, which will be perfect to mate to my sub, and should be around 100dB/2.83V even with the passive XO.... of course active is in the plans, but much further out in time.
Mark Seaton
Hi Markcertainly this 94dB version would be a nice compromise for many people and I'll look forward to your posting the specs - do you think the the 94dB unit may be able to xover as high as 1.8Khz? (I know this is high but I like it with some pro woofers and compression horn)
once I tested a woofer @150 watts - within a couple of minutes the voice coil melted the poly cone - then silence - I'm impressed by such a small change in Re under such conditions and hope to see the short-throw model with accordian surround.
Your Unity project should be a good one.
Freddy
Oops, I forgot to mention the top end performance of the TD-15. I recall Nick mentioning that the useable response is up to nearly 2kHz. I think he had said that the high end of his prefference would be about 1.5kHz. In fact he had talked about offering a version with the TD-15 mated to either a Raven tweeter or a compression driver like the TAD. Obviously dispersion will narrow some at the upper octaves, but I imagine it could mate well to a horn of similar dispersion at the crossover point.
Agreed Freddy,I myself am not so much a fan of efficiency for the sake of efficiency, but the amplifier options, huge headroom, and mostly the reduced power compression are my main reasons for the interest. At the same time, my subwoofer design is rather compact for what it does.
The higher efficiency versions of the TD-15 woofer will prove very interesting indeed, and I'll be looking at the benefits/compromises between those for my design.
It's hard to realize how much heat is really getting dissipated with those 200W delivered. If we go back to the actual efficiency (no. in %) of the woofer itself, the percentage of power which isn't turned into acoustic output HAS to go somewhere. Most all of that power turns into heat. So, the more efficient versions of the TD15 will have less heat to dissipate with the same input, and obviously will also have more acoustic output for that same power input... Things get quite scarry, especially given the physical throw these drivers are capable of :-).
I'll post the T/S specs this afternoon.
Mark Seaton
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