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Old 15th March 2018, 01:06 PM   #191
luxwinter is offline luxwinter
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I am attaching some curves representing the passive crossover corrections from John Riddley (tannoy). The violet line represents the correction without roll off in the tannoy crossover. The HPD probably uses a similar circuit - same tweeter. I have seen schematics for active crossovers, but the correction circuit looked very complex.
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Last edited by luxwinter; 15th March 2018 at 01:33 PM.
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Old 15th March 2018, 01:39 PM   #192
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John Ritter's schematic for an active Tannoy Gold crossover. The circuit for the notch filter and equalization is not simple.
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Old 15th March 2018, 05:03 PM   #193
Nelson Pass is offline Nelson Pass  United States
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Pass Labs B4 crossover questions
Looks similar to the crossover for the Linkwitz LX mini, for which I am
awaiting pc board delivery today or tomorrow.

I have the Tannoy 15" HPD coaxial Gold from early 60's. Is that similar
to yours? Crossover curve looks a bit different.

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Old 15th March 2018, 05:11 PM   #194
Zen Mod is offline Zen Mod  Serbia
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Pass Labs B4 crossover questions
all Pepperpots are approximately the same

difference is , if any , in low bass department
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Old 15th March 2018, 05:42 PM   #195
luxwinter is offline luxwinter
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Quote:
Originally Posted by Nelson Pass View Post

I have the Tannoy 15" HPD coaxial Gold from early 60's. Is that similar
to yours? Crossover curve looks a bit different.
I'll be keen to see that schematic, though my electronics skills are pretty rudimentary.

The HPD succeeded the Monitor Gold some time in the 70s. The tweeter / horn remained little changed across many generations of the vintage Tannoys, and the HPDs and Golds have pretty much identical circuits for the tweeters in their crossovers. The earlier Reds didn't have a notch filter, so I guess they had a nice peak in their response.
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Old 15th March 2018, 06:13 PM   #196
Zen Mod is offline Zen Mod  Serbia
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Pass Labs B4 crossover questions
in my experience , most complete (passive) xover/s for Pepperpot equipped DCs (doesn't matter what type of magnet) are Type 1009 and Type 1011 , used for K3808 and K3838 , practically SRM boxes

there is , if nothing else, practical survey of everything needed for Pepperpot Beastie to work

btw. time delay circuit thingie is waste of time

find downloadable pdf here : Dropbox - support.tannoy Tech_Manual_K3808_K3838.pdf
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Old 15th March 2018, 07:28 PM   #197
luxwinter is offline luxwinter
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I had a look. The high pass, notch filter, and equalization look like the same design as the Monitor Gold. The results you get with a passive crossover seem to vary a lot depending on the type of caps you use in the tweeter circuit. I wound up building a crossover that allowed you to swap out the capacitors easily.
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Old 15th March 2018, 07:36 PM   #198
Zen Mod is offline Zen Mod  Serbia
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that's easy - just use good ones

and use proper chokes

and make air-choke autoformer , instead of eenyweeny original (autoformer still being necessary , due to 1.25db necessary uplift in mid range)

I think Pa also have air-core autoformer on input of HF section
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Old 15th March 2018, 09:32 PM   #199
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that's easy - just use good ones
It's not just how "good" they are - there seems to be synergy with certain types of caps. I just downgraded from Jantzen Superior Z caps to a mix of Clarity ESA and Mundorf EVO oil caps, and it sounds better.
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Old 18th March 2018, 07:22 AM   #200
tyman63 is offline tyman63  Singapore
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Quote:
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However, I suspect that an adjustable version is what is going to be

needed, as I doubt we know the exact curves.



I have such a version in the works, where there are pots on the board,

allowing a 3:1 adjustment of frequencies for the crossovers and some

smaller adjustment for a low Q notch. If I stick it on my vast to-do list

it could be ready in a month or so.

Adjustable will be good. But if the fixed component can be easily calculated, we can try out various settings.
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