LZT

[MikeInNH]

Does anyone have any experience in using the LZT UHF speakers. I have a line on a pair and I'm thinking about using one of them for the highs in a center channel system I'm building.

However according to the docmentation I've read about them there's this special pass-band network they say you need to use with these speakers. It's used in all the speakers that have this UHF (Model 8, Model 6 and Model 4).

http://www.lansingheritage.org/html/...odel-4-6-8.htm

Anyone know if I can just use a standard crossover network?? This pass-band network is a mystery to me.

[Russ Farrell]

Hi Mike

The LZT was a piezoelectric tweeter made by Motorola. Now, I really hated the sound of the Motorola "bullet" piezos used in low end musical sound gear. The sound was like fingernails scratched on a blackboard to me. At that time we were coming out with the Model 9813 in the pro audio line to compete with the JBL 4313 in the recording studio and broadcast markets. The 9813 was simply a Model 6 with a different label. I asked engineering why would we ever use a piezo device in such a product. So they had me listen to it. I didn't grind my teeth - in fact I liked it. When I asked how they got it to sound like that, they said the secret was the bandpass network.

They said if it saw frequencies outside of the designed operating band, the LZT would produce high levels of distortion. Sorry Mike, but I don't have any technical info on type of filters, slope rates, frequencies, etc. (Somewhere I do have a schematic of a Model 6 crossover.) BTW I'm not the only one who liked the sound. The 9813 was introduced at an AES show in LA. We had a demo room set up to compare the 9813 and the 4313. Double blind, levels matched as close as possible, and a questionnaire to be checked off by the listeners. Then we would pull back the blinds so they could see which speaker they picked. Several people from Northridge came in, and were gracious enough to participate. All but one picked the 9813.

The LZT's had one other problem: inconsistent sound between units was common. (The 9813 was supposed to have "select" LZT's, but I have a strong hunch that there was no "selecting" once regular production started.) Also remember that the impedance of piezos is usually very high compared to a typical cone tweeter or compression driver, and that should be considered when designing a network. IIRC they told me the LZT had a lower impedance than the old piezo bullets, but again I have no hard numbers for you. Hope this helps Mike.

[MikeInNH]

Thanks for the feedback Russ. The reason I was looking at the LZT were.

1) Small format.
2) The 9813. I too had listened to the 9813. They were AWSOME. A friend of mine worked for a Altec dealer and I visited him one day and they had just received the 9813 about a week earlier. I already had my Model 15's, so I wasn't about to switch...HOWEVER...I would have seriously given the 9813's consideration if I was looking for new speakers. They were a very sweat sounding speaker. Actually the best speaker that size I've ever heard. I think they could still compete to almost any speaker today that size or smaller for overall sound quality.

[Old Guy]

The problem with the Motorola bullets is they will actually produce appreciable volume down into the midrange region. They do it in a very distorted fashion. Agree with GM in the proper situation they can sound good. FWIW Meyer used Motorolas in one of his setups.

I preferred a crossover in the 7000 hz region. It also helps to roll off beyond 20 k as they produce appreciable response there too.

Another problem is arraying them- I found they sounded best in a vertical stack.

The BMS driver that GM posted a link to is excellent. I have used them for supertweeters on top of 299's for SR.

[MikeInNH]

The other driver I've been looking at is JBL's 2404H. I've listened to them before in a system from Gold Sound. One of the few speakers I've auditioned in the past 20 years that were as good or better then my Model-15's that was under $2k.

[GM]

Greets!

Never auditioned the LZT, but a Motorola bullet sounds quite good with a decent >5 kHz XO. Don't know about today's cheap Chinese knock-offs though. This driver is pretty small: http://www.woodhorn.com/BMS/bms_4540nd.htm

GM