Need assistance - hooking up 30W speakers to 17W amp - will not work

Hello All,

My knowledge of audio is VERY limited and I need a little help.

I'm trying to recycle my old car stereo by turning it into a home stereo.
The car stereo outputs at 17W RMS and 50Wmax per channel (4 channels)
I have a set of speakers that are 60W max, 30W RMS, 4Ohm.

From what I understand the weaker amp should power more powerful speakers without much issue.  I tested the setup and ran into a problem.
The speaker works fine as the stereo powers up and begins to play.  As I increase the volume the speaker suddenly cuts out.
The stereo volume goes up to 50 (I don't know what 50 represents. Arbitrary value?) and the speaker cuts out around 21.
The volume at this level is much, much, lower than what it was when this stereo was in my car.  I assume this is due to the power mismatch with the speakers.  Is this a fair assumption?

What could be the reason for the speaker cutting out?
The speaker wire I used is 22 gauge, which could be a little thin.  It's all I had on hand while testing. Could this be related?

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iTinkers (author) 6 years ago
One thing I left out here was that I was testing with just one speaker on the right front channel. I had not considered that this could cause a problem.

Does anyone know if car stereo,s in general, have an issue with loading only one channel? Do I possibly need to put a load on all of them?

I had assumed it was some sort of mismatch between the stereo and speaker, but never considered that it may be some odd feature of the stereo itself.

Unfortunately, I won't have a chance to play with it tonight but I'll give it a shot tomorrow.
orksecurity6 years ago
Yes, the 50 is an arbitrary value.

I suspect the problem is that the electronics expects 8-ohm speakers, and you're using it with 4-ohm speakers (which will draw twice as much current). The cut-out sounds like a "crowbar" circuit, used to protect the amplifier from short circuits... and half the expected impedence may look enough like a short to make it unhappy.
iTinkers (author)  orksecurity6 years ago
I had assumed that the car stereo is expecting a 4 Ohm speaker. I had read somewhere that most car audio are at 4Ohm impedance so I hadn't even considered it.
I'll test it with 2 in series and see if it fixes the issue.
. +1.  It could be other things, but low impedance sounds like the best bet. Put the speakers in series on just one channel and see what happens. If you can get reasonably good performance, then you know orksecurity is right.

> the weaker amp should power more powerful speakers
.  Right. But the impedance mismatch may matter.

> speaker cuts out around 21
.  Another indicator that the speaker impedance is too low.

> The volume at this level is much, much, lower than what it was when this stereo was in my car
.  That's seems a bit odd. I would expect the volume to be about the same - maybe even a little louder - but with more distortion. That may be a result of the vast difference between the listening environments.

> speaker wire I used is 22 gauge, which could be a little thin.
.  Shouldn't be a problem for testing a fairly low-power amp if you keep the wires short. I wouldn't use it for normal operation, but it 's not your problem. If anything, the extra resistance would help the low impedance problem (until you burn up the wire heehee).
Since you seem to have the unit hooked up correctly, I can only ask: What are you using to power the car stereo? If the power supply is too weak, it will cut out early. Car stereos need a healthy 12 volt supply (actually around 13.4 - 13.6 volts) in order to push the rated power. Grab your car battery and see if it works like it used to.

Don't worry about the 22 gauge wire causing problems at this point. It can handle this sort of power easily as long as you don't have super long runs. Keep them around 20' or less. (Yep, waiting to hear from the wire with gain crowd on that comment)

iTinkers (author)  Quercus austrina6 years ago
I'm powering it with an old computer ATX power supply. The power does not seem to be an issue as the unit keeps playing properly.
It's a 450W power supply and it doesn't seem to have an issue.
orksecurity6 years ago
Low volume may also simply be a matter of less efficient speakers, or speakers which are less efficient in the frequency ranges you're paying attention to.
What is the amp supposed to feed. Are you running into a single speaker, or have you paralleled some ?

76543216 years ago
Put two 4-ohm speakers in series to get 8ohms impedance.