Wondering about Polyswitches

[transmaster]

Now that I know what a polyswitch is and what it does, and how it works I am wondering. I have read the other threads that allude to this part and most of the advice it to remove and install a jumper. The thing that I wonder with the original tweeters no longer made wouldn't it be a good idea to do what ever you can to protect the original if you have them. I am not sure what the value is on the installed MCI-500 but the 500 number on the ones I checked on means 5.0 Amps. The part is $1.70 at Mouser wouldn't this be cheap insurance? If you look at the schematics for the Model 10 the earliest one has no protection, the 2nd generation XO has a fuse, after that a polyswitch called safetyguard. What is the consensus out there. The biggest problem can I see is will there be room to install one with the beer keg sized capacitors that will be installed.

[falconcry72]

The best tweeter protection is using a quality amp capable of driving the speakers to desired levels without clipping. If you're doing that, you don't need the polys, and you might as well keep them out of the signal path.

Add to that the fact that the replacement tweeters still sold by polk are superior to the originals, and you can find originals easily, adds up to no polys.. for me at least.

[agfrost]

The consensus has been that, assuming you have quality amplification and use the volume control judiciously, there are sonic benefits to be gained by bypassing the polyswitch. Most of Polk's crossover designs eventually deleted the polyswitch/fuse; for example my RTA11TL crossovers never had a polyswitch, while the RTA11T they replaced did have one. I believe the same occurred in the SDA lineup.

The idea behind using a quality resistor in place of the polyswitch rather than merely a jumper is to maintain the resistance provided by the original polyswitches. While the majority use a resistor, I do believe some preferred to just use a wire jumper.

Bottom line (IMO), if you value most the peace of mind that a new polyswitch offers, order a handful and install 'em. If you're more interested in squeezing that last 3% of sonic performance, put a 0.5 ohm Mills resistor in there and call it a day.

[Lasareath]

My two pairs of 1.2tl's will have 0.5ohm resistors.

I say will because my 1st pair only has a jumper right now. I've bought the 0.5ohm but never had the chance to put it in.

After purchasing a pair of MIT Shotgun S1.3's I could hear a lot more highs, a little too much highs and i was told that the 0.5 resistor will tame those highs.

The reason for adding the 0.5ohm resistor is that the poly switch adds some resistance to the crossover and if it was there in the original design then we should have the same resistance even if we are not using the polyswitch.

[tonyb]

Bottom line (IMO), if you value most the peace of mind that a new polyswitch offers, order a handful and install 'em. If you're more interested in squeezing that last 3% of sonic performance, put a 0.5 ohm Mills resistor in there and call it a day.

Spot on, though most tend to go the resistor replacement route, either way.

[transmaster]

Thank you. I never thought about the protection afforded by a modern amp, My new TX-NR709 Onkyo is superb in this area. When the right hand Wharfedale's 8 inch woofer did it's death rattle the protective circuitry killed the right channel before I could even react to the situation. It will be a 0.5 ohm Mills.

I am not a noob with electronics in general, but in the audio world I am, this forum, The Classic Speaker Pages, and AudioKarma are a real treasure.

[pitdogg2]

5 amp polyswitch would be WAY too much!! I believe most were 1.0 amp or less I'll double check mine that Polk sent out to me at one time.(if you'dlike me to) I'm going with the 1.0 amp figure only because most of the fused models had 1.0 amp fast blo fuses. I also replaced mine with a .5 Mills resistor.

[bmbguy]

The SDA2A schematic has part listed as RDE050A. Parts Express has the Raychem RXE050, and it says that the 'current rating' is 0.5A, and the 'trip current' is 1.0A.

Agreed that 5 amps doesn't sound right.

[transmaster]

Thank you that is the problem with a part that is no longer made, 5 amp's did seem a bit high. I am going to go with the 0.5 Ohm resistor and let the output protection in the Onkyo take care of the rest. Again this forum is a treasure, thanks.

[pitdogg2]

Thank you that is the problem with a part that is no longer made, 5 amp's did seem a bit high. I am going to go with the 0.5 Ohm resistor and let the output protection in the Onkyo take care of the rest. Again this forum is a treasure, thanks.

well just so you know whatever protection your Onkyo has it is to more protect the receiver not your speaker.. Do not depend on it to protect the speaker you will still burn up tweeters with distortion and clipping the onkyo past it's limits..

[transmaster]

Now I am getting cold feet. I am telling myself with my Jazz, and big band blasted ears I would not be able to hear the 3% anyway. It would seem most everyone in out of stock on this part, my old friend Allied Electronics, as usual, comes through the part TE Connectivity RXEF050 is .37 cents each http://www.alliedelec.com/search/pro...59#tab=similar
One of the things I love about Allied Electronics is this: They have data sheets on all of their stuff below is the one for the TE Connectivity RXEF050:

[drumminman]

Now I am getting cold feet. I am telling myself with my Jazz, and big band blasted ears I would not be able to hear the 3% anyway. It would seem most everyone in out of stock on this part, my old friend Allied Electronics, as usual, comes through the part TE Connectivity RXEF050 is .37 cents each http://www.alliedelec.com/search/pro...59#tab=similar
One of the things I love about Allied Electronics is this: They have data sheets on all of their stuff below is the one for the TE Connectivity RXEF050:

Like others have said, quality amplification is the key to not blowing speakers. If it makes you feel better by all means insert a polyswitch. It's just not necessary, and you'll get more clarity with a resistor in its place.

I did resistor for polyswitch swap in my 2.3TL's and have had no problems at all, and I crank it to concert hall levels when I get inspired

[transmaster]

Just keep holding my hand I'll go through with it. I have a lot of time to vacillate the Warfedales W-35's get refurbished this next weekend, while not up to the blast levels of the Monitor 10B never the less they do a good job for a 3 way with an 8 inch woofer.

[DarqueKnight]

The thing that I wonder with the original tweeters no longer made wouldn't it be a good idea to do what ever you can to protect the original if you have them. I am not sure what the value is on the installed MCI-500 but the 500 number on the ones I checked on means 5.0 Amps. The part is $1.70 at Mouser wouldn't this be cheap insurance?

Polyswitches were included to protect tweeters from careless owners. If your speakers are not in danger of being overdriven, you really don't need them.

With regard to replacing polyswitches with resistors, that is a matter of personal taste and I would advise experimentation.

Here are a couple of threads in case you missed them:

SDA-Polyswitches-Are-Nasty

Resistor-Replacement-For-The-SDA-SRS-1.2TL-Polyswitch

[Joe08867]

I have replaced my polyswitches with small resistors in all my SDA's. It is a tiny resistor like .35 or something of that nature. Its been a while.

I tried just using a jumper but prefer the sound with the resistor.

[lanchile]

ok, my two cents here! first a 5 amp fuse for tweeter is WAY to high. Second I would NOT put a resistor to replace the poly-switch as protection. if you really want to put a protection for speakers, just use fast acting fuse. But again,that will not ensure 100% to save drivers. as long as you have a good amp with enough juice to drive speakers, it will not be a problem. I would worry more about putting a DC blocker protection for speakers. Beside you will "hear" wend the speakers are pushed to their limit then you should lower volume. The key is in the amp power.

[Joe08867]

The resistor isn't for protection it is to mimic the polyswitch in the signal path keeping the crossover within spec. Nobody said the resistor was for protection.

For protection he would need a polyswitch, or like you said a fast acting fuse The original ones with a fuse used a 1.0amp fast acting. Personally I would not do either. Just keep your volume in check and you should have zero issue.

[lanchile]

The resistor isn't for protection it is to mimic the polyswitch in the signal path keeping the crossover within spec. Nobody said the resistor was for protection.

For protection he would need a polyswitch, or like you said a fast acting fuse The original ones with a fuse used a 1.0amp fast acting. Personally I would not do either. Just keep your volume in check and you should have zero issue.

What is the resistance value of that Poly-switch? I do not think it will make an audible difference if it is replaced with a jumper.Even the best amplifiers can become faulty. One of the more common faults is destruction of the output stage and this presents a problem for speakers connected. If the output stage becomes short circuit, then the available rail voltage will be connected to the speaker directly and without intervention will quickly destroy them. unless the amp has a speaker DC blocker circuit build.

[bmbguy]

What is the resistance value of that Poly-switch?

The spec sheet for the RXEF050 that transmaster linked to yesterday had:

Rmin (?) = 0.50
Rmax (?) = 0.770

That matches what I've seen other places. So those opting for the 0.5 ohm resistor are right in the ballpark.

[lanchile]

http://www.google.com/url?sa=t&rct=j...L3jTP5cWRQPQwA

[Joe08867]

lanchile, read the two links above. You are over thinking it big time. We have been doing this for many years.

[heiney9]

Lanchile, once again you have taken everything to the absolute extreme. I have been running amps with no DC protection, muting relays, in rush limiter pretty much my entire life. Never an issue, not a single one. My current amp has nothing but an AC fuse to protect the amp. I can short the leads and the amp will not flinch. It has no relay, muting circuit, in rush limiter, etc. doesn't need one. The poly switch and or fuse is not neccessary if you have an amp that can deliver clean power for whatever your listening needs are. If the OP is not convinced then just use the poly.

I would love to be your insurance salesperson Lanchile, I bet I could sell you about every coverage available.

H9

[lanchile]

yeah, I think you are right Joe08867! I am over thinking it too much!. one time I remember, I called Polk Audio asking why they did not use "zobel network"(impedance compensator)in their crossovers and the sales Representative told me that it was not necessarily in their speakers...lol. Since then...I just build my staff.

[PreCd]

It really is about clean power. My SDA2Bs were run for 20 + years with a Yamaha R-9 receiver, 125 wpc. I hated my system. For the 1st few years I bitched and changed poly switches and the company I purchased the gear from even changed tweeters. Long story there so I will not go into it.

When that little SOB finally died I purchased a Adcom GFA-555, removed the poly switches when I TL'd them, and have no problem at all. And I can even listen to music now with my volume control past 10 0'clock. When I ran the Yamaha at 10 0'clock the poly switches would kick in. It really ruined my love for listening to music. Now it is back.

It was all about clean power.

It was all about clean power.

[F1nut]

I do not think it will make an audible difference if it is replaced with a jumper.

Oh yes it does.

[falconcry72]

Oh yes it does.

+1000. The difference is not subtle.

[jcaut]

It does make a difference, and that's coming from someone who really didn't think it would. The resistance of the polyswitch, I think, is enough to make a difference as well, though it's a small enough difference that it might just come down to personal preference whether one might prefer just a jumper vs. an additional padding resistor. On my SRS2's, I bypassed (jumpered) the polyswitch and increased the padding resistor to 4 Ohms from 3.5. Polys measured .3-.4 Ohms.

Also, DC on the amp output would be unlikely to damage a tweeter because any high-pass filter is going to have a cap in series with the tweeter, and capacitors don't pass DC. I suppose you could argue that a high enough DC voltage might short the cap too.. But again- highly unlikely, IMO.

The polyswitches were really just there to offer some degree of protection from careless and or clueless owners who would overdrive their amps.

[littlewoodboats]

Has anyone tried something along the lines of a stepped attenuator to make this adjustable or is that swatting at Butterflies with a sledgehammer?

[PolkClyde]

[QUOTE=heiney9;1750794]Lanchile,
I would love to be your insurance salesperson Lanchile, I bet I could sell you about every coverage available. END QUOTE

I would love to sell Mr. Lanchile some insurance pm me. :) it's a joke Lanchile.

[PolkClyde]

It

It was all about clean power.

It was all about clean power.END

This may be a stupid Question... How do you know you have clean power?.

1. When there's no audible noise or distortion coming from your speakers.

2. The manual says Hamonic distortion 0000.01 20hz to 20k or how ever they say it.

3. Those Amps are good and worth dropping 5gran or more on them. over 5 Gran,got to be clean.

4. Krell (now demised,I think) Amps are the best.. very,very clean power.

5. Buy any amp but a Carver...... darn, I got those bad mono blocks.

6. Ask somebody here on the Forum... they will never lead you astray.