I just got an Alpine MRP-M450 subwoofer amplifier. My head unit is a Pioneer DEH-P4800MP which has a 2.2V preouts. Initially, I set the amplifier gain to what I thought was 2.2V according to the scale on the dial. This was too low. I could hear very little bass. My head unit EQ was set to Flat. I had to turn the gain very high to get a decent bass output. Right now im temporarily using some old noname 8" subwoofer in a vented box. I plan on replacing it with an Alpine Type-R 10" subwoofer (SWR-1042D) once I build the box for it.
I called Crutchfield (where I bought the subwoofer amp from) and the first guy i spoke with said that the gain should not have to be set so high. He suggested connecting the front and rear preout RCA cables to the subwoofer amplifier to make sure that it wasnt the sub RCA cable that was at fault. I tried both the rear and front RCA cables and it was the same thing as before.
I called Crutchfield again and this time the guy said that the gain depended on the output of the head unit and that I should set the gain to its lowest setting and set the head unit volume to the highest volume I listen at and then increase the gain until subwoofer distortion is heard and then back off a little bit.
I am thinking the amplifier is defective because it doesnt seem logical that I have to set the gain on the amplifier lower than 0.5V (close to Max) in order to get decent bass when the preout voltage of my head unit is 2.2V. Doesnt having a high gain lower the sound quality? The specs say that its input sensitivity is 0.2-4.0V so since my headunit's output voltage is 2.2V, my way of thinking tells me that the gain know should be in the 10 to 11 o'clock position.
I have an Infinity 7541a 4-channel amp for my front and rear speakers and in that amp, the gain is set to less than half; clearly nowhere close to the max.
I called Crutchfield (where I bought the subwoofer amp from) and the first guy i spoke with said that the gain should not have to be set so high. He suggested connecting the front and rear preout RCA cables to the subwoofer amplifier to make sure that it wasnt the sub RCA cable that was at fault. I tried both the rear and front RCA cables and it was the same thing as before.
I called Crutchfield again and this time the guy said that the gain depended on the output of the head unit and that I should set the gain to its lowest setting and set the head unit volume to the highest volume I listen at and then increase the gain until subwoofer distortion is heard and then back off a little bit.
I am thinking the amplifier is defective because it doesnt seem logical that I have to set the gain on the amplifier lower than 0.5V (close to Max) in order to get decent bass when the preout voltage of my head unit is 2.2V. Doesnt having a high gain lower the sound quality? The specs say that its input sensitivity is 0.2-4.0V so since my headunit's output voltage is 2.2V, my way of thinking tells me that the gain know should be in the 10 to 11 o'clock position.
I have an Infinity 7541a 4-channel amp for my front and rear speakers and in that amp, the gain is set to less than half; clearly nowhere close to the max.
Is there anyway you can swap out the sub with another?Maybe a lower watt sub and see if sounds different.It sounds like you are on the right track but, i didn't see you try another sub.Did you try to bridge the amp and see if it was just the alpine didn't have enough power?Maybe the no name sub is a 4 ohm and the amp you have is pushing it at 4 ohm and that would cut the music lower.At 2 ohm you would here a difference and it would be louder.Get some more info on the sub for me and even if it is a 
.I can tell you the type-r 10 is going to want some power and maybe more than what the alpine can give.It all depends on how loud you like it and i'm sure you like it loud!LOL!I have my share of type-r 12's and they are nice subs.
.I can tell you the type-r 10 is going to want some power and maybe more than what the alpine can give.It all depends on how loud you like it and i'm sure you like it loud!LOL!I have my share of type-r 12's and they are nice subs.Yes, I do.Lothar34 said:
shallowfu said:Is there anyway you can swap out the sub with another?Maybe a lower watt sub and see if sounds different.It sounds like you are on the right track but, i didn't see you try another sub.Did you try to bridge the amp and see if it was just the alpine didn't have enough power?Maybe the no name sub is a 4 ohm and the amp you have is pushing it at 4 ohm and that would cut the music lower.At 2 ohm you would here a difference and it would be louder.Get some more info on the sub for me and even if it is a
I first tried the 8" sub.
The noname
8" subwoofer has an internal crossover and it also has two satellite outputs (L+R). The sub box is in my car right now but im pretty sure its only rated somewhere around 100Wrms. The subwoofer has dual voice coils and it says on the sticker that its impedance is 6 ohms. The subwoofer box has 2 inputs (L+R) and I wired them in parallel, so I am also powering the subwoofer in parallel. Im not sure if the 6ohm impedance takes into account the parallel wiring or not, so I may be really wiring it at 3ohm. I'll have to use my DMM to test the voice coils.I then tried the Alpine Type-R sub.
It hit harder than the 8" sub even though it doesnt have a box, so it may be fine when I put it inside a sealed box around 1.0 cu.ft. (minus the volume of the subwoofer). The gain was still at the very high level close to max.
Since you mentioned the Alpine amp may not be enough for the Type-R subwoofer since it only provides 400W at 2ohm, do you think I should get a higher rated amplifier? I was thinking it would be ok since it will be going in a sealed box and I read somewhere that sealed box lowers the power that can be given to a subwoofer. I am still within the 30 day Crutchfield satisfaction warranty so I can still return it and get a better amp.
Well if your Alpine sub sounds OK, then the amp probably isn't the problem.
I can't find the page with the instructions I used, but IIRC it goes something like this.
Turn off all EQ and loudness setting on the HU
Use a CD with 0db sine wave test tone. Something around 60Hz for the sub
Unplug all the speakers from the amp
Turn the HU's volume up to around 80% (shouldn't clip at that point)
Set the multimeter to VAC (if it's not an auto-ranging multimeter, use the range that goes higher than 50V)
Stick the positive lead into the positive output from the amp and the negative lead to the negative output.
(Volts * Volts) / Impedance = Watts
So for your 3ohm sub, you'd want about 19V. (19 * 19) / 3 =~ 120W
That's assuming the amp can put out 120W at 3ohm.
If you have an oscilloscope, you can check to see just how high the amp can go before it clips.
I can't find the page with the instructions I used, but IIRC it goes something like this.
Turn off all EQ and loudness setting on the HU
Use a CD with 0db sine wave test tone. Something around 60Hz for the sub
Unplug all the speakers from the amp
Turn the HU's volume up to around 80% (shouldn't clip at that point)
Set the multimeter to VAC (if it's not an auto-ranging multimeter, use the range that goes higher than 50V)
Stick the positive lead into the positive output from the amp and the negative lead to the negative output.
(Volts * Volts) / Impedance = Watts
So for your 3ohm sub, you'd want about 19V. (19 * 19) / 3 =~ 120W
That's assuming the amp can put out 120W at 3ohm.
If you have an oscilloscope, you can check to see just how high the amp can go before it clips.
I tried one input at a time and it is louder with both voice coils powered, so it is not a phase issue.
I am going to build the box for the Type R subwoofer next week and then ill post again to tune it. If even after having everything set up, I still have to turn the gain almost to max, then I think it will be the amplifier that is defective and ill have to exchange it.
I am going to build the box for the Type R subwoofer next week and then ill post again to tune it. If even after having everything set up, I still have to turn the gain almost to max, then I think it will be the amplifier that is defective and ill have to exchange it.
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