Question regarding the 16 ohm 1500 HZ Mastering Labs Xover

[mogsailor]

I asked this question over a year ago on a different forum but it was never answered so I'll ask it here:

I have a pair of these which apparently were originally used in the "Super Red" version of the "Big Red" monitor. Why do I think this? In addition to the 4 connections required for hookup to the 604E driver, it has another pair of connectors. My guess is that these extra two connectors were for the supplementary 15" woofer in the bottom of the "Super Red" cabinet. However, they don't connect into the crossover circuitry at the same locations as the primary woofer connector leading to the 604 driver's LF section. Perhaps the two EQ adjusting controls do not affect the lower woofer.

I have one unit installed and I'm listening to it now. The extra connections are unterminated - simply unconnected and separated from each other. The speaker sounds fine to me.

My question is: Is it electrically safe to simply ignore this extra connection and not connect it? Or, should a resistor be connected across the connectors to simulate a speaker load?

Thanks in advance for any answers or advice!

Best to all you Altec enthusiasts out there!

Fred

[Phil-G]

is there any marks by the terminals?

I asked this question over a year ago on a different forum but it was never answered so I'll ask it here:

I have a pair of these which apparently were originally used in the "Super Red" version of the "Big Red" monitor. Why do I think this? In addition to the 4 connections required for hookup to the 604E driver, it has another pair of connectors. My guess is that these extra two connectors were for the supplementary 15" woofer in the bottom of the "Super Red" cabinet. However, they don't connect into the crossover circuitry at the same locations as the primary woofer connector leading to the 604 driver's LF section. Perhaps the two EQ adjusting controls do not affect the lower woofer.

I have one unit installed and I'm listening to it now. The extra connections are unterminated - simply unconnected and separated from each other. The speaker sounds fine to me.

My question is: Is it electrically safe to simply ignore this extra connection and not connect it? Or, should a resistor be connected across the connectors to simulate a speaker load?

Thanks in advance for any answers or advice!

Best to all you Altec enthusiasts out there!

Fred

[mogsailor]

is there any marks by the terminals?

Hi Phil,

No markings for these extra wires.

They look like part of the original crossover in that they are similar to the 4 primary wires leading to the 604E driver itself. They even are sheathed with the same grey tubing as the primary wires. It's my opinion that the crossovers were originally constructed this way. It's also my opinion that they were, at some point, original equipment on a Super Red speaker
system.

My question is, how to I deal with these extra wires since, in my system, they are not used? What I have done is to protect the bare ends with tape, coil this separate "harness", and secure it with plastic ties.

My other question is, since they are unterminated, what, if any, are the electrical implications? The crossovers seem to operate just fine judged simply by listening.

Thanks for answering,

Fred

Forgot to say - the extra wires are color coded, black & red. The main harness includes red, green, white, and black wires, which match the diagram on the case.

[endeeinn]

Did you try to see if the Black wires are common? Likewise the Red wires?

[mogsailor]

Good question.

I didn't test with a meter but when I opened the case, I did notice that the leads for the 2nd woofer did not terminate at the same locations in the circuit as the leads to the main woofer of the 604E. There is no chassis used in this unit which uses a plastic (or Bakelite) case, so the grounding is sort of a bus type with all ground wires leading to it.

Unfortunately, the schematic I have for the ML Xovers does not show this later modification as used in the Super Red version of the monitor.

Perhaps an owner and current user of a Super Red system might have already looked into this and notice this thread.

I'm confident that using not these extra leads will not hurt anything but there are much better heads on this site than mine. Perhaps there is an impedance issue here.

Fred

[Phil-G]

Perhaps an owner and current user of a Super Red system might have already looked into this and notice this thread.

I'm confident that using not these extra leads will not hurt anything but there are much better heads on this site than mine. Perhaps there is an impedance issue here.

Fred

I know there's at least one person on this site that has a super red or knows the crossover.
have you tried the search Altec user board.

604e UREI horn mod?

[mogsailor]

No, Phil, I haven't done such a search. I'm an old guy somewhat new in the forum world. I've looked for a long time but rarely participated.

I'll try a search as you suggest.

Tks, Fred

[mogsailor]

604e UREI horn mod?

Phil, for the life of me, I have no idea where that came from or how it got into my reply!

I told you I was an old guy but hopefully not yet senile.

[GM]

Pretty sure you're right, but if you have an otherwise complete schematic (trace it to be sure), then trace/add these extra wires and post it.

[mogsailor]

Good afternoon, GM,

With your extensive background with Altec pro gear, I would guess that you must have seen inside a ML crossover. A lot of stuff packed into a smallish case with most of the space being occupied by three immense air-core inductors and the 2 large variable resistors used in the HF and MF circuits. Sorta hard to tell what is what. Also seems to violate a lot of "rules" for inductor placement in a circuit!

However, your advice is good as always and of course, logical. I have the schematic and will do as you suggest the next time I have the crossovers out of service - I'm listening to them now.

I also have two other crossover pairs, the OEM N-1500As which are like new, and another pair that I built from a schematic that Bill H. at GPA kindly sent me. These were designed by his friend, Jerry Hubbard, who was a acoustics engineer at Altec back in the day. I will no doubt be swapping in my DIY pair sometime soon.

Thanks, Fred