Amp to match speakers

dlagace · 26th November 2003, 11:04 PM

I noticed my head unit is under-powering my speakers. Could this be the cause of my speakers distorting even when the volume isn't loud?

If so would it be favorable to get an amp capable of giving them proper clean power? The continuous average power output of the H/U is only 18W x 4 into 4 ohm, 20 Hz to 20 kHz, 1%THD. The capabilities of the 4 speakers are 2 Memphis 15-PR46S 4x6 30W RMS, 86dB, and 2 Memphis 15-PR92S 6x9 60W RMS, 120dB. I'd like one amp to safely drive these 4 speakers. Is this possible? Or do I need 2 amps to compensate for the power handling and sensitivity issues?

Also, my sub amp is currently using the rear speaker pre-outs from the head unit. Only front pre-outs remain, do 2-into-4 RCA cables exist (to split the signal between 2 amps)?

Sorry for the newbie questions, I figured someone here must know some answers and I apreciate you reading. I'd like to get more technical info before I speak to the sales people so I can make a more informed choice.

Regards,
DL

sreten · 28th November 2003, 10:25 PM

since no-one has answered here goes :

The simple answer is no, lack of maximum power should not cause
distortion at low volume.

86db/W for one set of speakers sounds reasonable, 120db/W for
the other set has to be incorrect, its way beyond any reasonable
value - I'd guesstimate 87-89dB/W for the 6x9's.

You should not need a new amp or 2 amps to safely drive your speakers.
There are almost certainly no sensitivity issues.

Assuming there is nothing wrong with the head unit :

The most probable cause of distortion at low volume is a channel
shorting to ground causing the power sections to overheat and shutdown.

Another possibility is a very poor power conection to the head unit.

Another less likely possibility is your sub connection is causing
distortion at line level in the head - easily checked by removing it
temporarily.

Regarding your lead question an output can drive a number of inputs
1 into 2 adaptors are readily available if the leads aren't.
(you can't connect a number of outputs to an input)

I'd say the overall wiring of your set up needs to be checked.

I'd take the power ratings of your speakers with a pinch of salt and
suggest you don't need any more power, especially as you have a
seperate powered sub.

/sreten.

26th November 2003, 11:04 PM	#1
dlagace diyAudio Member Join Date: Nov 2003 Location: Canada	Amp to match speakers I noticed my head unit is under-powering my speakers. Could this be the cause of my speakers distorting even when the volume isn't loud? If so would it be favorable to get an amp capable of giving them proper clean power? The continuous average power output of the H/U is only 18W x 4 into 4 ohm, 20 Hz to 20 kHz, 1%THD. The capabilities of the 4 speakers are 2 Memphis 15-PR46S 4x6 30W RMS, 86dB, and 2 Memphis 15-PR92S 6x9 60W RMS, 120dB. I'd like one amp to safely drive these 4 speakers. Is this possible? Or do I need 2 amps to compensate for the power handling and sensitivity issues? Also, my sub amp is currently using the rear speaker pre-outs from the head unit. Only front pre-outs remain, do 2-into-4 RCA cables exist (to split the signal between 2 amps)? Sorry for the newbie questions, I figured someone here must know some answers and I apreciate you reading. I'd like to get more technical info before I speak to the sales people so I can make a more informed choice. Regards, DL

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28th November 2003, 10:25 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	since no-one has answered here goes : The simple answer is no, lack of maximum power should not cause distortion at low volume. 86db/W for one set of speakers sounds reasonable, 120db/W for the other set has to be incorrect, its way beyond any reasonable value - I'd guesstimate 87-89dB/W for the 6x9's. You should not need a new amp or 2 amps to safely drive your speakers. There are almost certainly no sensitivity issues. Assuming there is nothing wrong with the head unit : The most probable cause of distortion at low volume is a channel shorting to ground causing the power sections to overheat and shutdown. Another possibility is a very poor power conection to the head unit. Another less likely possibility is your sub connection is causing distortion at line level in the head - easily checked by removing it temporarily. Regarding your lead question an output can drive a number of inputs 1 into 2 adaptors are readily available if the leads aren't. (you can't connect a number of outputs to an input) I'd say the overall wiring of your set up needs to be checked. I'd take the power ratings of your speakers with a pinch of salt and suggest you don't need any more power, especially as you have a seperate powered sub. /sreten.