Monitor 10B Crossover Upgrade
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MattB23
Posts: 5
I found a pair of Monitor 10B's in my parents' basement and want to get those fired up. I am definitely a beginner in the audio world, but have been listening on a very basic setup for many years and want to start a proper entry level audio system. I found a Denon DRA-245 as well and ran the speakers through that with the pre-amp built in to my turntable. The sound was super fuzzy on both the low and high ends with only remote quality in quiet mids. From what I have seen I would guess the problem is simply degradation of XO components as they've never been replaced.
From what I've seen online I think I need two 12-microF caps and one 34-microF cap. I just have a few questions before buying the replacement parts:
Are these the correct values for the caps?
From the schematic I looked at, it specifies 'electrolytic' caps, but I see people installing polypropylene caps. What's the difference, if any?
Also, would you recommend replacing the resistor as well? I see a 2 Ohms resistor on the schematic, but is this correct?
I know this is a lot but I would really appreciate any help you all can offer! Thanks!
From what I've seen online I think I need two 12-microF caps and one 34-microF cap. I just have a few questions before buying the replacement parts:
Are these the correct values for the caps?
From the schematic I looked at, it specifies 'electrolytic' caps, but I see people installing polypropylene caps. What's the difference, if any?
Also, would you recommend replacing the resistor as well? I see a 2 Ohms resistor on the schematic, but is this correct?
I know this is a lot but I would really appreciate any help you all can offer! Thanks!
Comments
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I found a Denon DRA-245 as well and ran the speakers through that with the pre-amp built in to my turntable.
Are you sure the Denon model number is correct because I can't find a thing about it.
Do you mean your turntable has a built in phono pre-amp?
What input on the Denon did you connect the turntable to?
Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Ah yes it is a DRA-425 NOT 245. And yes my turntable has a phono pre-amp. Connected the turntable through the phono input on the Denon. Thanks
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That's the problem. Use an input other than phono on the Denon and report back. The turntable is already applying the riaa curve so you don't want to use the Denon's phono input.
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Agree ^^^^^ Question is - does it have a switch on the turntable to shut it off ? before hooking it to the phono input. Some (Audio Technica atpl120 I think it is - has a switch) otherwise I'd hook it to Aux if using phono preamp.... Not sure you have done this to your 10's but reseal your cabinets inside & put a bead of glue around all your MW driver magnets. To prevent magnet shifting..
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Randy/Maine -
Forgot to ask. What do you have for tweeters ? Maybe upgrade them. Well worth the $$$ imo..
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Randy/Maine -
Ah yes it is a DRA-425 NOT 245. And yes my turntable has a phono pre-amp. Connected the turntable through the phono input on the Denon. Thanks
I knew you had the TT phono pre connected the phono input. That, as DaveHo pointed out, is a big no-no.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
boston1450 wrote: »Agree ^^^^^ Question is - does it have a switch on the turntable to shut it off ? before hooking it to the phono input. Some (Audio Technica atpl120 I think it is - has a switch) otherwise I'd hook it to Aux if using phono preamp.... Not sure you have done this to your 10's but reseal your cabinets inside & put a bead of glue around all your MW driver magnets. To prevent magnet shifting
Ok that makes sense. I tried switching the TT pre-amp off (still plugged into phono input on Denon) and got no sound through the speakers. I'll keep the pre-amp on and try it through an AUX input so see if that makes a difference. Haven't resealed them, but can I just use a hot glue gun for that? Thanks! -
boston1450 wrote: »Forgot to ask. What do you have for tweeters ? Maybe upgrade them. Well worth the $$$ imo
They have the Silver Coil Dome in them -
Maybe try something else for a preamp. Even a USB DAC with a headphone amplifier has enough output to drive an amplifier quite well.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
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Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
That's the problem. Use an input other than phono on the Denon and report back. The turntable is already applying the riaa curve so you don't want to use the Denon's phono input.
Brilliant. I plugged the TT into the AUX input and everything is coming out perfectly clear. Thanks for all your help everyone! -
The input voltage levels are at least an order of magnitude different between the Phono and Aux. You may have damaged your phono input by overdriving it.
I've got a 625 which shares most of the design with the 425 and the service manual list the max input level for phono @ 110mv
