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Hey all, I'd like to upgrade my Unity Horns, and since every path seems to branch out into other paths, I'm wondering if someone out there has done something similar, or might otherwise help me narrow down my options a little.
Option 1: stick with the time-alligned DE25 passive XO and upgrade to fancier components
Option 2: multi-amp, upgrade only tweeter passive XO and do the mids XO in the active realm -- with the mids it looks like I could get away with a 1st order bandpass
Option 3: multi-amp and go to the TAD2001 for HF, which I seem to remember reading doesn't require CD-horn smoothing, and so could easily be XO'd at the amp with 1st, 2nd, 3rd, or 4th order high pass
Option 4: either multi-amp or use a passive XO using the original mids and the BMS 4550 tweeters, which seem to be getting really good reviews lately
I've heard a multi-amped system with the XO's done within the circuit of the power amps and then the power amps OPT's connect directly to the drivers, which would involve going to the TAD2001 or maybe the BMS 4550. This is what I'd really like to do, if possible and logical. But then, the current DE25 passive XO measures flat, and would help me avoid the can of worms of dealing with a new XO scheme, which might also sacrifice the time-alligned sound, which I do like. Another consideration, is that the passive XO is about 97dB/1W/1M, and the active options would be something like 10X as efficient, inviting simpler amplification.
Thanks a lot.... --keto
Follow Ups:
Hi
The unity horn that Lambda sold under license was one of the first horns of that type I had designed (now 11-12 years ago) and came with the De-25 hf driver.
Here is one as applied by a DIY builder;
http://www.cowanaudio.com/unity.html
I know later on, I also did a crossover for a TAD 2001 back when Paul B had them but I would have to look.
The BMS 4550 is a very good hf driver that I use in many of our products at work, it has two things which make it very useful. First, it’s internal origin is also a conical horn, even a one inch driver is large enough to cause directivity or if the wavefront is the wrong shape, radiates higher order modes, bouncing off the walls internally. That driver produces an expanding wave front internally unlike many that produce a plane wave at best or a self interfering pattern at worst. Generally, on a conical horn, the BMS will also have a higher sensitivity up high and down low, on that horn, the hf sensitivity would be a couple dB higher, it tolerates lf excursion better and has a little more headroom...
So far as CD compensation, understand that IF one could make a perfectly constant directivity horn, it’s frequency response will exactly reflect the acoustic power vs frequency that the driver produces.
ALL compression drivers exhibit an acoustic power roll off up high (above 2 to 4KHZ) and all of them have a lower limit set by the suspension stiffness and excursion.
The only ways to get “flat response” is to use a horn that constantly narrows as the frequency climbs (a curved wall horn) or use a filter to correct the drivers efficiency and make it flat again.
Toole and others have shown listeners prefer CD radiation as the reverberant sound field tends to have a response shape similar to the power response so a flat power response AND flat listener response is preferred.
The goal of the Unity was to combine the mid and hf ranges in a way that they combined into one source, for that, the dimension has o be less than about one quarter wavelength, just like the distance required for sub woofers to add coherently. There have been advances but they could be adapted to that horn.
So far as “active vs passive” understand, for flat response, the real or maximum sensitivity is limited by the efficiency of the system at say 15KHz or where ever you choose as your upper limit of flat response. The correction filter attenuates the mid band where the sensitivity is much higher.
So, the questions that come to mind are what measurement gear do you have /or have access to and / or do you live near Chicago or Atlanta?
Best,
Tom Danley
Thanks a lot for all the helpful info.
I do like the effect of the (Unity) sound remaining pretty much the same in the "sweet spot" as everywhere else in the room. I visited Servodrive in Chicago about 10 years ago and was blown away by the 40"x40"x16"-ish LF speakers you were just starting to make back then. Its one of those sounds that's very memorable, mainly for its effortlessness. I've just ordered a pair of 16ft3 boxes for the Lambda 15TDX's that complement my Unity Horns, in an effort to capture a little bit of that effortless sound in my own system.
I will get a pair of the BMS 4550's this summer, when I'm in the States, see how they measure in the 60x60 300hz horns, and report back. I can see from their freq graphs and your explanation how they might increase overall efficiency. And in the meantime, I'll appreciate the DE25's and their passive XO, just as they are, and focus my attention on building better amps for > 300hz.
FWIW, don't know if this is the 'last word' WRT a passive solution for the TAD, just something I saved for future reference when it was posted long ago:
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Thanks for the schematic. While I'm now leaning away from the TAD because of cost and availability, its interesting to see that there is again basically a 1st order bandpass for the mids, in addition to what looks like impedance smoothing and padding.
Correct, combined with proper driver alignment it's what's required to get a nominally flat phase response in a multi-driver system.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Hello Keto;
Would I be able to email you? Thanks
BN
yeah, sure
Hi Keto;
Your email does not accept unsolicited emails.
BN
.
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