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Multi-Way Conventional loudspeakers with crossovers

Mission 751 Crossover Circuit Diagram
Mission 751 Crossover Circuit Diagram
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Old 10th June 2017, 10:08 AM   #21
ThetaII is offline ThetaII  United Kingdom
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..also, would I be right in thinking that changing this cap combination to a 6.8uF cap, as suggested on the first page, would have the effect of rolling off the treble a bit? ..or is that over-simplifying how it works?

Last edited by ThetaII; 10th June 2017 at 10:36 AM.
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Old 10th June 2017, 10:55 AM   #22
Lojzek is offline Lojzek  Croatia
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The most probable answer why they used a combo of poly/electrolyte capacitor is the simplest one. Either they had a stock of these and/or it was cheaper that way without making too much of a compromise. Increasing to 6.8 uF would elevate lower trebble, lowering XO point, increasing the SPL summed in XO region, which may or may not be a good thing, who knows.
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Old 10th June 2017, 11:22 AM   #23
ThetaII is offline ThetaII  United Kingdom
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Thanks again for the information
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Old 11th June 2017, 01:48 AM   #24
system7 is offline system7  United Kingdom
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From what I've read, the Mission 751 has a rather irritating metal tweeter with a polycone 5" 6 ohm bass.

The ferrofluid is prone to solidifying, but easily replaced:
https://www.bluearan.co.uk/index.php...new=Ferrofluid

I suspect a 7.5R/0.68uF Zobel across the tweeter might help tame the top end.

Rough and guessy circuit below, disregard the level adjusting resistors. It all looks OK to me.
Attached Images
File Type: jpg Mission 751.JPG (20.6 KB, 74 views)
File Type: png Mission 751 Guess Circuit.PNG (7.0 KB, 131 views)
File Type: png Mission 751 Guess FR.PNG (17.8 KB, 70 views)
File Type: png Mission 751 Phase Guess.PNG (16.1 KB, 70 views)
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Old 11th June 2017, 08:11 AM   #25
ThetaII is offline ThetaII  United Kingdom
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Thanks for the info Steve. Regarding the 'irritating' metal tweeter, I think people have made unfair comment on that in the past - my perception is that it may sound a bit harsh on bright systems. It doesn't appear to have issues on most british or french made sources/amps ...from my experience (some amps tested with: A&R A60, Musical Fidelity A1, Atoll IN200).
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Old 11th June 2017, 05:46 PM   #26
dewdrop is offline dewdrop  Singapore
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I have replaced the capacitors with Dolan but noticed that one speaker is now more prominent than the other, louder on one of the tweeters.

Now, I have to use the amplifier balance setting to negate this.

Any advice to fix this?
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Old 11th June 2017, 05:47 PM   #27
dewdrop is offline dewdrop  Singapore
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Quote:
Originally Posted by dewdrop View Post
I have replaced the capacitors with Dolan but noticed that one speaker is now more prominent than the other, louder on one of the tweeters.

Now, I have to use the amplifier balance setting to negate this.

Any advice to fix this?
It should be Solen caps, sorry for the auto correction.
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Old 11th June 2017, 09:44 PM   #28
ThetaII is offline ThetaII  United Kingdom
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Hi Ed. You've probably worked out that I'm no expert but my logic says if you have checked the components and solder connections then maybe there is an issue with one of the tweeters/drivers. Did you replace all 4 caps or just the 3.3 and 1uf for the tweeter?
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Old 11th June 2017, 11:16 PM   #29
dewdrop is offline dewdrop  Singapore
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Quote:
Originally Posted by ThetaII View Post
Hi Ed. You've probably worked out that I'm no expert but my logic says if you have checked the components and solder connections then maybe there is an issue with one of the tweeters/drivers. Did you replace all 4 caps or just the 3.3 and 1uf for the tweeter?
Unfortunately I have already checked for dry solder joints. No luck.

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Old 12th June 2017, 07:44 AM   #30
ThetaII is offline ThetaII  United Kingdom
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What capacitor values did you use?
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