Removing poly switches from crossovers on SDA-2
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Scott99
Posts: 33
I have decided to build new crossovers for my SDA-2's. I have read some people have removed the poly switches and replaced them with .5 ohm resistors. Has anyone done this? Would you recommend this? Any thing I should consider? I measured the resistance of the two poly switches in my left speaker. One was 2.3 ohms and the other was 6.2 ohms. I have read that poly switches should be .5 ohms.
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many have removed them it is well documented. What are you powering the speakers with and which SDA2?
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I plan on using an Arcam Delta 290 integrated amp. 70 watts per side at 8 ohms. Not sure if this amps wattage goes up to 140 at 4 ohms. I don't listen at very loud levels so I should not be at risk of clipping.
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My SDA-2's have two tweeters SL2000 tweeters, 3 mid woofers and a passive radiator.
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Did you remove the polyswitches from the board before testing them?Post edited by F1nut onPolitical 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 -
I have not taken them off yet. I figured they should at least measure close to the same value even if the other components were affecting the measurement.
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You have to measure them out of the circuit.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 -
Anyone know where I can find .5 uf caps for these crossovers? I could not find them at Part Express or Parts Connexion.
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You want .5 ohm 10 or 12 watt Mills resistors. Sonic Craft carries them, but so should the others.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 -
I had found the mills resistors but have been having trouble finding the .5uf caps. I found .47 and wonder if this is close enough?
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Ok i see it is across a resistor. What caps are you going to use?
I would think .47 would be close enough BUT since it is used across a resistor in a contouring means I'll let more experienced folks chime in. -
I attached the circuit diagram for the crossovers below. Has anyone heard of any updates since this was done?
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I had found the mills resistors but have been having trouble finding the .5uf caps. I found .47 and wonder if this is close enough?
Apologies, the .47uF will be fine.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 -
Thanks!!!
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Since I am trying to keep my cost down. I am considering the caps below. The prices below are for the 12uf caps. I am intrigued by the 1% tolerance of the Dayton. Any Suggestions?
Dayton Audio PMPC 1% Tolerance, 250V, $8.87
Solen Fast Cap PPE 5% Tolerance, 630V, $6.26
Clarity Cap PX 5% Tolerance, 250V, $9.23 -
Forget Solen that 650v will be HUGE.
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I am building new boards so size should not matter unless you are saying the larger size could effect the sound?
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Also wanted to ask if you guys had any opinions on the coils. I am thinking reusing the original coils. They are all air core and in good condition. I think I read someone suggested upgrading the largest coil. What do you think? Is this a worthy upgrade for the money?
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Ok no problem but they are about the size of a can of soda.
For those may not be worthy upgrade for the inductors -
Thanks for the advice!
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Since I am trying to keep my cost down. I am considering the caps below. The prices below are for the 12uf caps. I am intrigued by the 1% tolerance of the Dayton. Any Suggestions?
Dayton Audio PMPC 1% Tolerance, 250V, $8.87
Solen Fast Cap PPE 5% Tolerance, 630V, $6.26
Clarity Cap PX 5% Tolerance, 250V, $9.23Also wanted to ask if you guys had any opinions on the coils. I am thinking reusing the original coils. They are all air core and in good condition. I think I read someone suggested upgrading the largest coil. What do you think? Is this a worthy upgrade for the money?
Many people re-use the inductors. Finding exact inductor matches with the proper resistance can be difficult, and in some cases need to be hand unwound to get the proper value. The caps and resistors will be the biggest gain.
For caps SonicCraft are the most recommend for polks (and a number of other speakers). They can do custom values. Clarity ESA/CSA are often next in line. Solen and Clarity PX have been recommended for the low pass caps as a cost saving, followed by Dayton caps.
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I just ordered the caps yesterday. I chose the Clarity PX caps for the 6.5" drivers and the Dayton 1% tolerance caps for the tweeters. Also ordered Mills resistors. One of the reasons I chose the Dayton is the 1% tolerance will keep the cap closer to the original .5uf spec. I could only find .47uf caps in the affordable range. I hope it all sounds good. Keeping my fingers crossed.
Thanks for your advice. -
So it looks like the poly switches caused my left speaker to have slightly lower volume. finally got around to taking everything off the crossover boards. I retested the poly switches and they still measure the same as they did on the board 6.2ohms and 2.3 for the left speaker. They should measure .5ohms. For future trouble shooting. You can check the resistance of these poly switches while they are on the board. You should have the drivers disconnected as well as the jumper wires between boards, speaker wires and interconnect cable. I measured the capacitance of the caps and they were all in spec as well as the resistors and coils.
