Choices of speakers

[rdarlington]

This is an old trick to bring an old (sitting on the shelf a long time) electrolytic capacitor back to life. It "forms" the layers of foil and insulation back to normal. We use to do it attaching a variable power supply and slowly cranking up the voltage over a few hours to the capacitors rated voltage. A resistor would do the same but less controlled.
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That's what my Sencore Z-meter is for ;-)

But yah, the old trick is to bring the voltage up slowly to reform them. I learned the hard way with old equipment and now use variacs the first time (usually old tube based test equipment I restore).

-Bob

[Malevy]

Are you actually arguing that a capacitor in parallel with a load does not smooth out transitions in voltage?

Either way, I don't have to rely on the perception of my ears to tell me the capacitor is doing its job- I can see it in my AFR readings.

[Malevy]

Explain why putting a tiny battery (the capacitor) in parallel with a big battery (the car battery) without a resistor in between them has any impact at all.

Actually, there is a resistor- the wire between the battery and the amplifier.

(for example) 10 feet of 8 AWG wire will have a 1/2 volt drop at 40A.

1/2 volt may not seem like much on the input of the supply, but (depending on the internal power supply design of your amplifier) that "loss" is multiplied internally because the actual "rail voltage" of the amplifier is much higher.

[rdarlington]

Are you actually arguing that a capacitor in parallel with a load does not smooth out transitions in voltage?

Either way, I don't have to rely on the perception of my ears to tell me the capacitor is doing its job- I can see it in my AFR readings.

No, that's not what I'm arguing. I'm saying the capacitor isn't boosting the power to your amp.

[Malevy]

I never claimed it "boosted" the power..

Maybe this will explain it better; https://www.parts-express.com/resour...apacitors-faqs

[rdarlington]

Yes yes, I'm aware of that page and that theory and that it's bunk. I'm officially giving up and will no longer comment on this. It's not worth it to me.

[aipri]

Looking forward to installing the 1 farad Monster Cable cap I have with my system soon. I'm sure it will work well as they always have.

[Malevy]

Theory? Bunk?

Even if you cant *hear* the improvement with the addition of a capacitor, you can clearly see the difference with a simple test- Hook up a DVM (with the ability to hold min/max) to your car, and see how much the voltage drops while a high power amplifier driving a low impedance woofer at 500W (or more). Install a large capacitor, and repeat the test. You WILL see a difference (if you do the test correctly). If you think the difference is "in the noise", take the amplifier apart and repeat the test monitoring the rail voltage inside the amplifier. I have a feeling after you do this test, you will want to hook up some stiffening capacitors directly to the rail inside the amp.

Reminds me of when I started out as a tech at Bell-Labs, I had an argument with one of the senior engineers who said "Audio is AC, so polarity does not matter", and made a wager that I could not hear the difference. I bet him that *HE COULD* hear the difference. It was not until I set up an experiment in the lab, with a switch for him to do an A-B comparison of "in phase" and "out of phase" for him to admit he was wrong. I won the bet.

At my age, I doubt I could hear the difference with/without a stiffening capacitor- but I know it is saving my alternator (and electrical system in general) from unneeded abuse from my audio system.. Funny enough, I have "big systems" in 3 of my cars but only have the capacitor in the DeLorean (because of the ECU issues I mentioned).. So, on the way home last night I was blasting the crap out of the system in my BMW and could clearly see the headlights dim with every pound of the woofers. Maybe time for me to add a capacitor!

[AirmanPika]

Thanks for the feedback, though I think the discussion strayed a bit. Having been working on vintage home stereo gear I do understand the principals behind the cap. My concern was would I put too much load on the power supply the car itself is supplying when you factor in everything else. Tomcio answered most of that for me (and yes I mean 130A, thank you). What I was worried about was seeing things like brownouts, dimming lights and so on should the amp actually push close to its max 400W output (unlikely but I'm thinking ahead, and again to Tomcio, yea it would be a true 400Ws). For now I think I'll skip the cap and just go with the raw setup.

Otherwise I finally fixed the amp. I installed the new terminal block (it was fried from some past catastrophe and bypassed) and did a final inspection. All is good and functional so I did a quick fit test tonight and to my delight the parcel shelf is comfortably deep enough for the amp. I was thinking it might be a tad too narrow but that isn't the case. It will be warm(ish) tomorrow so I may try and get this thing wired in finally.

[AirmanPika]

Got everything hooked up though I still need to work out some of the cable routing to make it neat. I came across a tiny Alpine KTP-445U head unit amp while grabbing parts and decided to try it out as a sub amp.

alpinesubamp.jpg

It's super small and since I'm only pushing one channel (it can only be bridged down to 90x2W so I'm just doing 90W to the sub) it should be OK sealed up inside the subwoofer cubby. If it doesn't work out I'll get that small Rockford Fosgate 300x1W amp which should also fit, but I dunno how it will like enclosed spaces with no ventilation.

ampinstall1.jpg

I just want to complement the lows, not shake the car apart (it does that fine on its own).