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AR9 bass cap question


Shacky
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I recall reading here that a certain cap in the woofer crossover was put in place to make the AR9 more amp friendly and if a powerful enough amp is used that cap can be taken out of the circuit and mean greater bass response (not that these really need that ;).

so is that correct and does my Oddessy Stratos amp qualify as sufficient?

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The 2500uF.

Can your amp handle/stable at < 2 ohm loads ? Your amp may not be happy and may release the 'magic smoke'

The other drivers will not be affected as far as impedance.

Doubt you will hear a difference.

There are at least 3 other threads on this topic.

Not recommended.

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I recapped a pair of 9's in July. I also read those threads and decided to buy into eliminating the 2500uf cap to run the dual woofers at 2 ohms.  

I installed a cover guard on the switch knowing that running the speakers in 2 ohm mode would destroy most amplifiers.

Here is where the two grey wires run to the switch on the upper board. Basically between the 2500uf caps and the #10 coil.

1fP2fOUl.jpg5SraIRxl.jpg

mBm50cil.jpg

I have a Crown XLS 2500 amp that can easily handle these low impedances.   It is mid September now and I have yet to throw the switch to 2 ohm. I have decided that it was probably a unwise modification. In fact I am thinking of going back in and soldering in a jumper wire across the break thus eliminating any function of the switch. Thus eliminating any possibility of some future owner damaging their amplifier.    

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Having listened to my AR9's since August 1978, I fail to see the purpose of eliminating the capacitor to bring the impedance down to 2 ohms.   Why do these speakers, which are prodigious bass capable behemoths, need to produce even more bass?   I listen to movies in 5.1 with no subwoofer and allow the AR9's to handle the LFE.

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2 hours ago, AR surround said:

Having listened to my AR9's since August 1978, I fail to see the purpose of eliminating the capacitor to bring the impedance down to 2 ohms.   Why do these speakers, which are prodigious bass capable behemoths, need to produce even more bass?   I listen to movies in 5.1 with no subwoofer and allow the AR9's to handle the LFE.

Agreed...imo, it was just another example of misleading audio forum speculation.

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Removing that cap and coil does not lower the impedance, it allows the system to peak higher 

at resonance (harder to drive because it is more reactive), and lowers the output at resonance.

The only advantage is not having to replace that large 2500uF NPE cap.

I explain it here, and Tom Tyson agrees:

https://community.classicspeakerpages.net/topic/8395-ar-9-bass-crossover-modification/?do=findComment&comment=102725

 

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I said, years ago, that I'd try to find a good solution for the 2500uF cap, it should be

(very) low ESR.  I'd probably use a pair of back to back polarized snap-in caps because

they are designed for very low ESR.  Consider that these are in series with the large 

inductor and there will be a point of diminishing returns.

Right now I'm looking at 5000uF 100V, Mouser #661-ESMQ101D502MA40S putting them

back to back drops the value in half.

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1 hour ago, Pete B said:

Mouser #661-ESMQ101D502MA40S

The specifications claim a life of 2000 hours.  What does this actually mean?

"The following specifications shall be satisfied when the capacitors are restored to 20°C after subjected to DC voltage with the rated
ripple current is applied (the peak voltage shall not exceed the rated voltage) for 2,000 hours at 85°C."

Also, does installing them in series to achieve the 2500uF requirement cause any issues?

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It means that if you operated them at the max rated temp, and the max ripple current then

they will last at least 2000 hrs.  As used in a speaker they'll last as long as most electrolytics.

No other issues wiring them in series.

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