Help with my new purchase

blownaway
blownaway Posts: 15
in Vintage Speakers
Hello everyone, just made a purchase the other day that I am extremely happy with, but need some clarification and your thoughts. Grew up with my dad always listening to his monitor 10b's that he bought new. Bought some monitor 5's with the peerless tweets for surrounds about a year ago and a CSI5 for a center channel. Decided I wanted to see what the SDA life was about(has been a long time goal to eventually get some version of the big SDA SRS... so frickin cool!). So I came across some SDA-1c's for sale this past weekend for 300 and had to go check them out. I immediately fell in love when I heard them. They're a little rough, some of the fabric has come loose as well as one panel, but with some glue should look almost perfect. They already had the RDO 194's, sound deadener, and the motors glued. The guy also had a pair of monitor 10b's that he wanted to get rid of for 50, but one driver is locked up. These came with grills, and a set of stands for the monitors. How do you all feel I did for 350?
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So here are a few questions that I need answered... the SDA-1C with the cloth sides like mine only had pin blade connectors correct? The guy couldn't really remember but was wanting to say it had blade blade before the speakon cable was put in. He said that the polyswitches were removed, but didn't think he put a resistor inline... how bad is that, and is that something i should take care of before playing them? The monitor 10b drivers are 6503's correct? Is there a better place to source them than midwest speaker repair? Kinda doubt I would have any luck trying to correct the magnet shift(making an assumption that's what's wrong with the bad one).

I think that's all for now. Will be looking to get an amp for the SDAs in the next week or so. Eventually want to fix the monitor 10's, and do upgrades on them, as well as replace the caps and resistors on the SDAs(he said he didn't replace them). Anything you guys want to throw in or that I should know/consider, please lay it on me. Look forward to interacting with you all more in the future.
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Comments

  • F1nut
    F1nut Posts: 49,782
    Is the original SDA socket still on the binding post plate?

    The polyswitch has about .5 ohms of resistance. By not replacing it with a .5 ohm resistor the treble will be louder/brighter than it should be.

    I wouldn't spend a penny on the 10's. Part them out and use the money to repair/upgrade the 1C's.
    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

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  • blownaway
    blownaway Posts: 15
    edited May 2020
    F1nut wrote: »
    Is the original SDA socket still on the binding post plate?

    The polyswitch has about .5 ohms of resistance. By not replacing it with a .5 ohm resistor the treble will be louder/brighter than it should be.

    I wouldn't spend a penny on the 10's. Part them out and use the money to repair/upgrade the 1C's.

    No, it isn't, it was replaced with the speakon connector as well. vjp74m3cvg5v.jpg
    mq98m80b741p.jpg

    How much does the .5 ohms(I'm assuming per tweeter?)
    change the resistance an amplifier sees? Is there a point where the lowered resistance would cause much extra risk for damaging the tweeters or any other components inside the speakers? I'm not familiar with how everything is wired inside. Why wouldn't you mess with the monitor 10's? The cabinets are in fantastic condition. I'm assuming the only thing wrong with them is the single driver. The SDAs don't need much money put into them either tbh, adhesive, caps, and resistors are the only things that really can be done. Also, the serial numbers for the SDAs are 8705 for the right and 8766 for the left if it can help anyone verify what sort of connector type these were originally.
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  • F1nut
    F1nut Posts: 49,782
    I already told you what the resistor is for.

    Because they aren't all that.

    Those s/n indicate they are pin/blade.
    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

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  • BlueBirdMusic
    BlueBirdMusic Posts: 2,075
    edited May 2020
    @blownaway,
    You have the attention of one of the experts on the Polk Forum so please keep that in mind to arrive at the best place.

    Welcome to the forum!
    Harry
    "Sometimes you have to look to the past to understand where you are going in the future"


    Harry / Marietta GA
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  • blownaway
    blownaway Posts: 15
    edited May 2020
    F1nut wrote: »
    I already told you what the resistor is for.

    Because they aren't all that.

    Those s/n indicate they are pin/blade.

    Yes you did, but I didn't feel that the questions in my second post were answered regarding the damage potential of components or resistance seen by an amp. Like I said, I'm not familiar with the routing or resistances inside one of these.

    No they aren't, but I shall fix them. They are 6503 drivers correct?

    And thank you very much. That makes picking an amp up a little easier/less worrisome if nothing else lol. And speaking of an amplifier, I really only have a budget of about $500 that I care to spend right now. I live in Indiana, between Indianapolis and Fort Wayne. I don't mind having to drive as far as like Chicago area, Cincinnati, etc. I was thinking about picking up a crown XLS 1502 if I couldn't find anything better used... which I had not seen so far in my searches. Would anyone care to help me out in case there's an amp I have missed? I definitely like to listen at louder volumes for longer periods than i probably should, so larger power is definitely something I could use.
    Post edited by blownaway on
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  • blownaway
    blownaway Posts: 15
    BlueBirdMusic wrote: »
    @blownaway,
    You have the attention of one of the experts on the Polk Forum so please keep that in mind to arrive at the best place.

    Welcome to the forum!
    Harry

    Thank you for the information, as well as the welcome! It is always nice knowing someone knows their stuff.
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  • [Deleted User]
    [Deleted User] Posts: 7,658
    The polyswitch is a resettable fuse, it's made of a small amount of a plastic material that has carbon black suspended in it. At normal operating temperatures the structure of the plastic compound has the carbon black molecules in contact and the material is conductive. When a certain amount of current flows through the polyswitch the plastic material begins heating up and liquifying and the carbon black particles are no longer in contact and the switch stops conducting. The polyswitch begins cooling down and the plastic compound begins solidifying and the carbon particles regain contact and begin conducting again.
    This polyswitch is in series with your tweeter and it has an internal resistance, if you remove it you need to restore this resistance as F1nut states with a small value resistor otherwise the frequency response will be different than original.
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  • blownaway
    blownaway Posts: 15
    KennethSwauger wrote: »
    The polyswitch is a resettable fuse, it's made of a small amount of a plastic material that has carbon black suspended in it. At normal operating temperatures the structure of the plastic compound has the carbon black molecules in contact and the material is conductive. When a certain amount of current flows through the polyswitch the plastic material begins heating up and liquifying and the carbon black particles are no longer in contact and the switch stops conducting. The polyswitch begins cooling down and the plastic compound begins solidifying and the carbon particles regain contact and begin conducting again.
    This polyswitch is in series with your tweeter and it has an internal resistance, if you remove it you need to restore this resistance as F1nut states with a small value resistor otherwise the frequency response will be different than original.

    Didn't know that's how the polyswitches actually work... pretty neat. If I had read it before, it definitely went in one ear and out the other lol. Has anyone ever taken measurements with various resistors? Hadn't come across any hard data in my readings so far. I know in older threads I had seen people use various resistances or none at all after removing a polyswitch. F1nut had a post i saw where he mentioned that he and a number of others just found it too hot without the resistor. I wasn't sure if it was completely safe to try it without one, or if there is a point where I would risk damaging any component? If there isn't any real risk of damage, I'm curious to see how I like it, but do imagine I will want one eventually. If there truly isn't one in there now, the guy I got them from played them for who knows how long without it, and that's how I heard it demonstrated(granted at fairly low to moderate volume). It didn't bother me in the conditions I heard it under, which of course could change with my setup, but I also was wondering if there is anything that may have been negatively affected by him doing so. Also, are mills resistors recommended for putting in place of the polyswitch or something else? And is there a currently recommended place to source caps and resistors from?
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  • Gardenstater
    Gardenstater Posts: 4,180
    edited May 2020
    How much it increases the risk is anybody's guess or estimate but less resistance means more current without a doubt. The most important thing is to make sure you use an amplifier that has plenty of surplus power and to avoid clipping at all times. I think everyone here would recommend that only resistors like Mills/Vishay be used that have low self inductance and to use a higher power rating so as to reduce the thermal noise in the system. Most people here favor Sonicaps and Claritycap CSA's, as reasonably economical choices. You can go much higher end if you don't care about price of course.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
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  • [Deleted User]
    [Deleted User] Posts: 7,658
    edited May 2020
    Another approach would be to place a 4 ohm resistor (assuming the tweeter is 4 ohms) in parallel with the polyswitch. That way when the switch is tripped the tweeter's volume would be reduced by approximately 3dB. In effect turning it down instead of shutting it off.
    Post edited by [Deleted User] on
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