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Impedance Matching

Turns out, nowadays amps are not the problem, it is speakers. I have blown more speakers than I can count. Same way when I built car amps, had to tell people to just use house speakers on them.

For a while in my car I had a nice pair of horns facing front on the rear deck, and just studs sticking up for the 6 X 9s. I could change one out in like fifteen seconds. I always kept a few extras in the trunk. They mounted face down right on the bolts, not even screwed down.

And damn that thing sounded good. It was about every three weeks, a woofer or two and a fuse. It blew those 20 amp fuses all the time.
 
Thanks for all the comments. I don't think overheating will be an issue because a) I live in a small house, b) I don't want to make my ears bleed and c) my neighbours are just the other side of the wall and I'm sure they'll give me a cheery reminder if they think my amp is overheating!

From what's been said I feel more confident buying the 2020i's so that's what I'll probably be doing on Tuesday.
 
Perhaps also to mention for completeness (apology if it is old hat):

Loudspeaker impedance is not constant - at least most of them aren't nearly. As far as I know it is still supposed to be the value at 400 Hz. Broadly, a nominally 4 ohm unit can rise to say 12 ohms near bass resonance, rise again above some 2 KHz. But then just to make matters nicely complicated, some loudspeakers can dip sharply to <half the nominal value at some h.f.

This makes the minimum impedance figure and consequences thereof rather conditional. Heat generated is a function of how much music comes at that exact frequency, phase angle of, possible stability of the amplifier under that precise condition etc. All of this can play a role in the possible demise of said amplifier. (Indirect things like phase angle can cause a momentary condition to exceed a transistor's safe limits; in plain English it is mostly but not only heat generated which matters.) Meaning then that it is rather impossible to guarantee amplifier health by simple figures only. Obvious safeguard is not to go too near amplifier limits - but then again that comes at a price.
 
It's actually quite simple. If you hear or notice sounds of distress, turn down the volume. No other admonition is necessary.
 
Audiovet said:
Perhaps also to mention for completeness (apology if it is old hat):

Loudspeaker impedance is not constant - at least most of them aren't nearly. As far as I know it is still supposed to be the value at 400 Hz. Broadly, a nominally 4 ohm unit can rise to say 12 ohms near bass resonance, rise again above some 2 KHz. But then just to make matters nicely complicated, some loudspeakers can dip sharply to <half the nominal value at some h.f.

This makes the minimum impedance figure and consequences thereof rather conditional. Heat generated is a function of how much music comes at that exact frequency, phase angle of, possible stability of the amplifier under that precise condition etc. All of this can play a role in the possible demise of said amplifier. (Indirect things like phase angle can cause a momentary condition to exceed a transistor's safe limits; in plain English it is mostly but not only heat generated which matters.) Meaning then that it is rather impossible to guarantee amplifier health by simple figures only. Obvious safeguard is not to go too near amplifier limits - but then again that comes at a price.
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Whoosh...! That's the sound of that going straight over my head, I accept your apology for it being old hat and raise you a pair of socks as an apology for me being thick.

I'll just keep an eye on the volume thanks:).
 
Bottom line, crank it up. Keep going until you hear distortion and then back off. Run it a while and see how hot it gets. Jam out, play some rock n roll with bass. Test it (beat on it lol).
 
Impedance specs in speakers are simply a sort of indicative rating, as impedance is a complex function of frequency, e.g., https://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers

1024px-Speaker_impedance.svg.png


The best is to consider that figure as a sort of "representative" minimum value across the entire audible spectrum (20 Hz - 20 KHz). The practical advice that was given to you of just plugging in the speakers and listen carefully at low volume levels is a good one. Look for signals of a stressing amplifier (heat, funny smell, etc). There is a lot more in this thread: http://audiokarma.org/forums/index.php?threads/why-4-ohm-loads-stress-your-amplifier.60386/ .
 
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whoaru99 said:
Not sure why add a resistor to lower the load (raise impedance) yet then turn it up 30% more.
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See I don't know if he'll turn it up... And, if he does the amp won't be sweating bullets. If it's just comfortable listening levels, it'll just be one notch higher.

For me, it's about protecting the old gear. Not reaching max volume. You wanna go loud, get a modern AVR for $30 off CL and crank it on "2-channel" mode. It won't care, and if it blows, it's just $30 - easily replaceable :)
 
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