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Old 22nd February 2010, 06:56 PM   #1
Lucky13 is offline Lucky13  United States
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Default Crossover Upgrade: Newbie Seeks Advice

Greetings all ó please allow me to introduce myself as a new member seeking some basic advice & pointers.

Iíve decided to undertake my first DIY project: updating the crossovers for my c.1989 Dahlquist M-905 speakers. These were purchased new by my brother back in the day and passed along to me as a gift about 10 years ago. Theyíre in great condition and perfect working order, but I have the itch for an ďupgradeĒ without the budget for a new pair of speakersÖdonít suppose Iím the first to find myself in this situation

After doing some research and reading, I settled on the idea of replacing the capacitors as a cost-effective way to gain some improvement in my systemís sound quality. That said, Iím hoping to to benefit from the experience of folks on this Forum who have gone before me and are willing to share their knowledge. Listed below are some of the initial questions Iíve been thinking aboutÖ

- What kind of changes (presumably improvements) in SQ might I expect after upgrading the crossover components?

- For those of you whoíve done this kind of project before, what tips, pointers, advice would you offer to someone whoís starting their first project? Looking for anything at all here in terms of tools, materials, process, common mistakes to avoid, etc., which could be of help to a newbie.

- Should I replace other components while Iím in there? e.g., resistors, wires, inductors, etc. Iím basically interested in doing things which will provide the most noticeable SQ improvements.

- Can you recommend suppliers for parts? So far Iíve found Sonic Craft (soniccraft.com) but of course am open to other suggestions. I also know of a company called Regnar which supports old Dahlquist products and sells a cap upgrade for the M-905, but prefer to go the DIY route as I suspect Iíll get better bang for the buck.

- What kind of budget should I expect to need?

- Lastly, is this a lot harder than it looks? I have good mechanical and basic electrical/soldering skills mostly from working on cars & motorcycles, but havenít gone the DIY audio route before. Red flags?

The M-905s are 2-way speakers, so the XO design is pretty simple (see attached photo) and contain only 4 caps total. The cap values are 10k and 5k mF.

Thanks in advance for your advice!
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Old 22nd February 2010, 07:54 PM   #2
Lucky13 is offline Lucky13  United States
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Photo failed to attach to original post, here it is...
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Old 24th February 2010, 09:01 PM   #3
Lucky13 is offline Lucky13  United States
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Bump...anyone...Bueller...?
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Old 24th February 2010, 09:41 PM   #4
DcibeL is offline DcibeL  Canada
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If that photo is the original crossovers, I wouldn't touch a thing.
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Old 24th February 2010, 09:48 PM   #5
Face is offline Face  United States
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It's fairly simple, replace said parts with newer parts of the same value.

Unless the wiring and inductors looks burnt or corroded, leave them alone.

I would replace the resistors with Mills 12w units. As for caps, Sonic Caps would be a good choice. For large shunt values, Sonic Craft offers AEON caps.
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Old 24th February 2010, 10:16 PM   #6
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Quote:
Originally Posted by Lucky13 View Post
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Well, those caps are not electrolytic caps( they will not dry out). so I would not touch that crossover.leave it original!. most the time when you change caps in crossover it is because they have electrolytic caps that with time they start leaking and dry out, those are the ones you change!. in my opinion I would leave them original.
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Old 24th February 2010, 10:48 PM   #7
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I agree, there is not much to be done here. You could bypass those capacitors (the yellow things) with some .22uf film and foil polypropylene caps from parts express. The existing caps are film type, not electrolytic which would really benefit from upgrading. It is possible that those caps are polyester, though, and could potentially benefit slightly from upgrading to polypropylene caps. Dahlquist fanatics would probably know if that was the case. Find another project, no huge gains here from tampering, in my opinion.

By the way, those caps are not "10k and 5k"... the smaller one is 6uf.

Last edited by DreadPirate; 24th February 2010 at 10:59 PM.
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Old 25th February 2010, 12:07 AM   #8
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Leave The XO "As IS"
What are you actually seeking to "IMPROVE"
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Last edited by Moondog55; 25th February 2010 at 12:08 AM. Reason: Clarification
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Old 25th February 2010, 12:28 AM   #9
DcibeL is offline DcibeL  Canada
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Perhaps somewhere that would be of some benefit to improve is the cabinet. Can you post some photos of that? How thick is the material? How much bracing is there? Does it sound hollow when you knock on the side with your knuckle?

You can always cut some dowels and insert them into the cabinet to improve bracing, as well you can always add some more damping material. These are simple and cheap tasks.
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Old 25th February 2010, 02:03 AM   #10
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Welcome!

Pick up a set of speakers from a thrift store and practice your de-soldering skills on it before you ruin good speakers. What tweeter is in there, by the way?

Madisound or Parts Express for parts. (And Apex Jr actually has several film caps cheap.)

Last edited by Andersonix; 25th February 2010 at 02:06 AM.
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