My new-to-me 820s

[alancohen]

MiniDSP seems like a good answer for your needs.

You just need to check the input sensitivity of the amps and make sure you won't have a gain issue. I was going the MiniDSP route before I built my Hiraga passive XOs. But the passives sound so good I'm leaving well enough alone.

[wws944]

Short of running the wires straight to the components, the best speaker terminations are cold welds [ideal crimped] with the clamped ring tongue connector being its disconnect equivalent, so cheap as they look, Altec provided the right kind of terminal strip, though probably not of the best materials, but an anti-oxidant paste such as Penetrox will ensure a long term, low loss, electrically stable connection.

The problem is that one has to unscrew/rescrew about about 20 screws to remove/replace each of the back panels. This makes access to the strip a PITA.

Another option would be to remove the N800D crossovers and run separate woofer and HF horn wires to the outside. Then I can easily play with biamping vs the original crossovers (and HF horn settings on the N800D) for a while.

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You just need to check the input sensitivity of the amps and make sure you won't have a gain issue. I was going the MiniDSP route before I built my Hiraga passive XOs. But the passives sound so good I'm leaving well enough alone.

That MiniDSP board looks nice! And certainly is reasonably priced.

The amps I would be using for biamping are 1970s era SS McIntosh. One is my trusty MA-6100. (I bought this amp new in 1975ish.) The power amp section is direct coupled and rated at 70w/ch. The other is a MC-2100 - 105w/ch with autoformers. The MC-2100 has gain controls on it. So I should be able to match the input sensitivities pretty closely. Yeah, it is way more power than these speakers will ever need. But since I already have them, the cost is zero.

I'd assume I'd want the MC-2100 on the woofers due to the autoformers and lower DF?

[alancohen]

Yes, being able to attenuate after the MiniDSP is a plus. I was planning on running my preamp into the MiniDSP and then two amps out that did not have attenuators. One had .8v Input sensivity, the other 2.2V. Getting all that to work without noise would have been a challenge. I'm glad my passive XO worked out.

[amandarae]

Hello Alan,

People suggested to have a TVC at the output of the preamp, not the conventional position of having it at the input, then to mini dsp or active XO. Since its a transformer base, and attenuating line level already, noise introduction is strongly minimize. Please post your result if you are going to try it this way as I want to know your experience/impressions. All the best!

Abe

[GM]

The problem is that one has to unscrew/rescrew about about 20 screws to remove/replace each of the back panels. This makes access to the strip a PITA.

Another option would be to remove the N800D crossovers and run separate woofer and HF horn wires to the outside. Then I can easily play with biamping vs the original crossovers (and HF horn settings on the N800D) for a while.

I'd assume I'd want the MC-2100 on the woofers due to the autoformers and lower DF?

Well, the assumption here is that the terminal strip is accessed without removing the rear cover same as a later version I've seen, so a relocation project on your part. .

Yeah, more wiring, but with large cabs a near 'must do' when 'voicing' a speaker.

Well, normally this would be my choice, but I guess it depends on what what you want to do with the Mini-DSP.

GM

[puppybeast33]

Great thread...you are so lucky to have two of these. After reading this I dusted off my old 820, mono'd er' up and started thinking of things I can do with with her so there might be two 820 threads on here soon.

[wws944]

Great thread...you are so lucky to have two of these.

It took my uncle several years, back in the 1960s, to find the second 820 to make the stereo pair. And that was in Los Angeles, where one might expect a lot of them to be around. (In the meantime he used a Avalon, updated to Carmel specs with a second woofer, for the other channel.)

After reading this I dusted off my old 820, mono'd er' up and started thinking of things I can do with with her so there might be two 820 threads on here soon.

Nice! Yours appears to be a very late 820C. Has green components and the Little Conductor emblem on the grill - like my 1957 cabinet.

Do you know if yours has holes on the bottom, the tilted wood piece, or both, to tune it? Based on mine, I would guess it has just the tilted wood piece.

[puppybeast33]

I really want to find a match but until then I'm going to part them out for stereo cabs like your uncle...just haven't decided on the design yet. I already have another horn driver and n-800d crossover but may go with a different xover scheme after reading your thread and several others.

So as you can see from the pics, the cabinet has the holes on the bottom. It's dated 1951 on the back label. I can't speak for the components but when I purchased this about 6yrs ago everything looked really clean and stock on the inside but I'm no expert on the subject. Bass drivers are 803a, 811a horn, 802c driver for the horn, cabinet is marked 821a.

[GM]

It's interesting the number of different ways these were assembled, especially the HF horn and XO mounting/wiring. Apparently, the worker either didn't have a very detailed assembly sheet or chose to 'personalize' it and/or engineering kept changing it for better or worse to justify their job.

GM

[wws944]

I really want to find a match but until then I'm going to part them out for stereo cabs like your uncle...just haven't decided on the design yet. I already have another horn driver and n-800d crossover but may go with a different xover scheme after reading your thread and several others.

Horrors! I would look for a couple more 15" woofers, rather than even thinking about parting out the 820.

So as you can see from the pics, the cabinet has the holes on the bottom. It's dated 1951 on the back label...

Is that the label which tells how to pull the grill nose off to fit through narrow doorways? I think that one is dated from 1951 and refers to the cabinet as a 820A.

Your cabinet is much more similar to my 1957 cabinet than my older 1955 cabinet. There should also be schematic on the inside of one of the back panels. If it is there, I bet it is dated as a 'issue 3' 820C. There should also be date codes on the woofer cones.

Interestingly your cabinet has *both* the holes and the tilted piece. It also has a brace on the back of the HF horn - which neither of mine have.