Infinty RS2.5 resistance at terminals

rudedogg

rudedogg

AK Member
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Hey folks. I brought home a nice looking and sounding set of RS2.5 today. Just for kicks, i checked resistance at the input terminals after unloading them, with my good Fluke meter. I am seeing ridiculously high resistances! Both read around 150kohms when first checked. Then it rose to 800kohm!! But the reading climbs or drops depending on the polarity of my test leads… What the hell am i seeing?? A major crossover failure? Or something else? They sounded fantastic when auditioned…
 
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mrfredo said:
You're measuring crossover caps.
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I am/was hopeful it is something that simple! Lol… All my other sets of speakers do indeed show around 3ohms resistance for 4ohm impedance, 5-6 for 8… etc. also, these have a “biamp/single amp switch at the top. Yet somebody added a copper jumper across the two sets of terminals as well! I am having a nervous breakdown something is amiss!!!
 
rudedogg said:
these have a “biamp/single amp switch at the top. Yet somebody added a copper jumper across the two sets of terminals as well!
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Maybe the switch(es) became troublesome and a previous owner jumpered the inputs.

If something terrible were amiss with your speakers, it's unlikely they would sound great. But you say they do, and that's definitely a positive.

That said, your speakers are 45, so more likely than not they need work in order to be their most reliable and best-sounding selves again.

Also, you will need serious amps to drive them. What amp(s) do you currently have?
 
mrfredo said:
Maybe the switch(es) became troublesome and a previous owner jumpered the inputs.

If something terrible were amiss with your speakers, it's unlikely they would sound great. But you say they do, and that's definitely a positive.

That said, your speakers are 45, so more likely than not they need work in order to be their most reliable and best-sounding selves again.

Also, you will need serious amps to drive them. What amp(s) do you currently have?
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Yes i am sure they can use a crossover rebuild. I am thinking of using a solid state 2 ohm stable amp for the lows. Maybe a couple big tube monos up top? Or my 275 there
 
I would say 2 ohm stable is baseline minimum. My monoblocks are 2 ohm stable and 400wpc rated @ 4 ohm. They're up to the task of driving my RS-II, but they don't have much headroom to spare at high SPL.

You can biamp yours, so that gives you more options. Do you have the active Infinity crossover? It may have been an option with the 2.5
 
Definitely measuring capacitors and the fact that you see resistance increase and then probably decrease, means they are working normally
 
mrfredo said:
I would say 2 ohm stable is baseline minimum. My monoblocks are 2 ohm stable and 400wpc rated @ 4 ohm. They're up to the task of driving my RS-II, but they don't have much headroom to spare at high SPL.

You can biamp yours, so that gives you more options. Do you have the active Infinity crossover? It may have been an option with the 2.5
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Hmmm… now i regret selling off my Yamaha PC400m! It would have put over 500 per side into these at 4 ohm. The guy who sold these to me still has Monitor II, RS 4.5, RSII, and RS1b! He has the active crossovers on two sets. But i did not get one with my set. The one powered unit is for either the 2.5 or 4.5. I will have to hunt one down
 
Assuming you meant PC-4002M - yes it would have been a good candidate.

But honestly many pro amps will perform well on bass duty. Vintage Crown Macrotech or some such.
 
mrfredo said:
Assuming you meant PC-4002M - yes it would have been a good candidate.

But honestly many pro amps will perform well on bass duty. Vintage Crown Macrotech or some such.
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What are your thoughts on using a modern lightweight pro amp? I have a Crown XLS-1502 that is stable to 1 ohm i believe? It is spec’d to 525wpc 4ohms. It is class D IIRC? but will it provide enough current i wonder… The amp weighs like 12lbs! Lol
 
rudedogg said:
What are your thoughts on using a modern lightweight pro amp? I have a Crown XLS-1502 that is stable to 1 ohm i believe? It is spec’d to 525wpc 4ohms. It is class D IIRC? but will it provide enough current i wonder… The amp weighs like 12lbs! Lol
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It will provide the voltage and current necessary to produce rated power.

No amp can provide "higher current" than commensurate to its actual output power.
 
rudedogg said:
I am/was hopeful it is something that simple! Lol… All my other sets of speakers do indeed show around 3ohms resistance for 4ohm impedance, 5-6 for 8… etc. also, these have a “biamp/single amp switch at the top. Yet somebody added a copper jumper across the two sets of terminals as well! I am having a nervous breakdown something is amiss!!!
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That would have made me think something was wrong, too.

But it looks like every driver has a capacitor in series and that will make the DC resistance measurements look like they did.

 
RVT1K said:
That would have made me think something was wrong, too.

But it looks like every driver has a capacitor in series and that will make the DC resistance measurements look like they did.

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Thanks, and yes, i looked at that as well and wondered if that indeed affects the resistance readings. I did try checking the drivers at their tie points at the crossover caps. And i am seeing around 1ohm for the Emim and Emit drivers. And 5ohm for the woofer. These measurements are also “in circuit”, but give me confidence things are better than they appear at the terminals! I am going to try and carry the heavy things upstairs to my main room today. Remove the “bus bar” jumpers at the terminals, and test them with the Crown XLS and a Mac tube pre…
 
rudedogg said:
Thanks, and yes, i looked at that as well and wondered if that indeed affects the resistance readings. I did try checking the drivers at their tie points at the crossover caps. And i am seeing around 1ohm for the Emim and Emit drivers. And 5ohm for the woofer. These measurements are also “in circuit”, but give me confidence things are better than they appear at the terminals! I am going to try and carry the heavy things upstairs to my main room today. Remove the “bus bar” jumpers at the terminals, and test them with the Crown XLS and a Mac tube pre…
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Good luck with all of that!

I'm more than a little envious..I have always lusted for Infinity speakers but never had the opportunity to own any.
 
RVT1K said:
Good luck with all of that!

I'm more than a little envious..I have always lusted for Infinity speakers but never had the opportunity to own any.
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I honestly drove 90 minutes in the crappy weather to look at a different set. Monitor II speakers. Those are small, heavy little towers with the Walsh cone tweeter. He demo’d them, and i was sold! He then asked if i had time to listen to some of his other Infinity collection which i did. The 2.5 and 4.5 were amazing to my ears. And he was willing to give quite a good deal to move these ones out, due to them being repainted in satin black at some point. The paint work is exceptionaliy well done. But i made a couple jokes about being “Bose black” and he agreed and let me have them very fair. I might be convert to vintage Infinity if all goes well at home with this set.
 
Here are a few pics..
 

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I read thru the owners manual and now understand things a little better. I redid the messy jumpers at the terminals and hooked them up. Loving them so far! Please excuse the messy cabling as i just threw things in place to test run them. They are being driven by a Crown XLS 1502 and a McIntosh MX110z for the moment
 

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RVT1K said:
That is an interesting take on a stereo rack.

Did you make it yourself?
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My buddy made it from fallen trees on his property. All live edge dried/seasoned wood. I traded him labor on a restoration for the stand
 
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