Replacement ceramic resistor for my crossover/amp question...

Joe70

A little back story:
I happen to have an extra Crown XTi 2000 laying around and decided to hook it to my Polk Monitor 70's. For 8 ohm stereo, the amp delivers: 475W (per channel) with 0.5% THD.
The 70's are rated at 275W, so I figured If I keep the Amp at or below 50% I should be well in the safe zone.

Perhaps not...
The setup has worked for quite a few months. However, one of my towers was producing no highs recently; I thought one of my tweeters was blown and I ordered a replacement from Polk. Upon installing the replacement I realized my crossover is blown (probably should have checked that first). A ceramic resistor labeled 5W1RJ is visibly scorched on the crossover PCB. It is the first component coming from the the upper set of plugs on the exterior plate.

First Question:
Can I order the resistor here as a replacement:
http://www.parts-express.com/1-ohm-5w-resistor-wire-wound-5-tolerance--015-1

Second Question:
Is there a danger is using this Crown XTi 2000 at half power with my Monitor 70's? (It sounds a hell of a lot better than then my TV receiver)

F1nut

You'd be better off replacing with a Mills 1ohm/10watt resistor, do both speakers. The Mills is a much better sounding resistor and the higher wattage rating will help it from cooking. Speaking of which, clipped signals generate a lot of heat, which is the more likely cause of your issue rather than sending too much clean power.

Is there a danger is using this Crown XTi 2000 at half power with my Monitor 70's?

How did you determine the amp was putting out half its power?

JeremyJ

That resistor will work. You can also find them on ebay. Also, at 50% it's possible for that amp to peak far above 275w. I wouldn't worry about it though. Especially if it's already worked for you for a few months. You can check the power with a multimeter, or just turn it down a notch until you stop blowing resistors.

Joe70

Thanks guys!

@F1nut
I have the volume knobs for the channels at 12:00
I will try to measure this a little more accurately!


Which of these would be the better choice:
1. http://www.soniccraft.com/product_info.php/11-ohm-mills-mra-10-p-4586

2. www.parts-express.com/mills-1-ohm-12w-non-inductive-resistor--005-1

Wasn't sure if the 12w resistor would hurt anything tonally or make the tweeters the next weakest link...

F1nut

I have the volume knobs for the channels at 12:00

Ah, you meant the level on the amp. Forget that for a minute, how high was the volume level on your AVR?

The 10 watt will be fine.

Joe70

I used to have the volume level on my AVR (Pioneer VSX-40) between 40 and 50 in loud situations.

Currently there is no receiver in this setup. Essentially I hooked my 70's to a rack of equipment I had for live sound/PA use...

Signal Chain:
PC w/ Foobar2000
Behringer XENYX X2442USB
Behringer ULTRAGRAPH PRO FBQ1502
CrownXTi 2000
Polk Monitor 70's

The only two devices I currently have that go from USB -> XLR for the Crown are the mixer mentioned above and a Digitech RP1000 (Guitar Effects Processor).

I bought a a pair of Monitor 40's for my TV/AVR, so, eventually I will come by enough money to buy an appropriate amp. I'm thinking an ADCOM GFA-555 II if I can pick it up at a decent price used.

Thanks Again!

georgejo

You could use any available ceramic resistor you can get hold of. Just a reminder the higher the wattage rating the larger the physical size of the resistor will be. Going back to pairing your amplifier with your monitors, be sure that the rated output impedance of your amp matches that of your monitors. If they are matched the burning of the ceramic resistor would not happen in the first place.

Regards,
George J
http://blog.7pcb.com

F1nut

Going back to pairing your amplifier with your monitors, be sure that the rated output impedance of your amp matches that of your monitors. If they are matched the burning of the ceramic resistor would not happen in the first place.

How do you figure that?

tonyb

I think you might be pushing them a tad too hard. Maybe you should have sought out pro speakers instead of home speakers to run with your pro gear. In any event, keep the volume down some from your previous positions.

Joe70

tonyb wrote: »

Maybe you should have sought out pro speakers instead of home speakers to run with your pro gear

Actually that amp normally drives 2 JBL JRX 125's... I upgraded the horn drivers and I still hate those speakers! They do nice outside in a field.

I will definitely keep the volume down a bit. I finished upgrading the resistors and they sound good.

Thanks.