Sub distortion and amp power
Discussion
Hi, hoping someone can help with this. I've just fitted an 8" Alpine sub to a ski hatch enclosure in a 3 series. Previously I was running an amplified box in the boot as a temporary measure without issue. The problem I'm having is quite a lot of distortion at very low volume levels. I have a suspicion but I'm looking for other opinions - I'm wondering if the amp is not sufficiently powerful? I thought I'd try an Alpine amp that I just happened to have in the garage which is rated at 140w RMS, the sub is rated at 350w RMS - does the amp just not have the balls to run this sub?
Many thanks!
Many thanks!
140w RMS isn't much when it comes to a bass line.
The amp should have a gain dial for controlling when the amp/sub combo get to their peak abilities and start distorting. Ideally that would be about the same time everything else does. Might be worth having a fiddle with that but I wouldn't expect miracles.
The other thing I would check is that you are getting sound in to the amp on both rca leads. I've came across problems before where the bass has been disappointing only to find that its only half the signal coming in for amplification in the first place.
The amp should have a gain dial for controlling when the amp/sub combo get to their peak abilities and start distorting. Ideally that would be about the same time everything else does. Might be worth having a fiddle with that but I wouldn't expect miracles.
The other thing I would check is that you are getting sound in to the amp on both rca leads. I've came across problems before where the bass has been disappointing only to find that its only half the signal coming in for amplification in the first place.
Edited by ALY77 on Tuesday 19th April 20:44
Hi,
How is the musical signal being input to the 140W RMS amplifier? if you are using a speaker level to RCA converter, then what's happening is the in built amplifier of the car's head unit (if OEM) is being driven into distortion, which is quite easy to do as it's not very powerful. The distortion is then passed straight to your 140W RMS amplifier, where it 'amplifies' it and passes the even more distorted signal to the subwoofer. This is the main reason why voice coils heat up and then will fail. People who go this route will then turn the gains and bass control on the amplifier to try and compensate which then reduces the levels quite a lot.
If you have the output from a higher quality head unit with RCA phono outputs and perhaps with a dedicated sub out then you might have the gains and bass levels up too high on the amplifier. Also, as mentioned, 140W RMS is on the light side of power output. Another aspect could be that the wiring might not be capable of delivering enough current to the amplifier.
Check all of these areas and I'd say the best solution would be a good quality head unit with a sub output RCA/Phono connection. A more nomninally more powerful amplifier 250W-300W RMS to perhaps 450-600W RMS and a Class D small footprint one which are very efficient and at this level of power won't really need any bigger batteries/alternators or bigger thicker cables etc, a well installed power and ground connection/wiring once you choose a good amplifier and also a similar amplifier of perhaps 4x60-90W RMS for the front and rear upgraded speakers in the cabin of the car. A setup like this, well installed and setup will have absolutely minimal distortion and will sound a whole lot better than what you currently have.
Cheers, Dennis!
How is the musical signal being input to the 140W RMS amplifier? if you are using a speaker level to RCA converter, then what's happening is the in built amplifier of the car's head unit (if OEM) is being driven into distortion, which is quite easy to do as it's not very powerful. The distortion is then passed straight to your 140W RMS amplifier, where it 'amplifies' it and passes the even more distorted signal to the subwoofer. This is the main reason why voice coils heat up and then will fail. People who go this route will then turn the gains and bass control on the amplifier to try and compensate which then reduces the levels quite a lot.
If you have the output from a higher quality head unit with RCA phono outputs and perhaps with a dedicated sub out then you might have the gains and bass levels up too high on the amplifier. Also, as mentioned, 140W RMS is on the light side of power output. Another aspect could be that the wiring might not be capable of delivering enough current to the amplifier.
Check all of these areas and I'd say the best solution would be a good quality head unit with a sub output RCA/Phono connection. A more nomninally more powerful amplifier 250W-300W RMS to perhaps 450-600W RMS and a Class D small footprint one which are very efficient and at this level of power won't really need any bigger batteries/alternators or bigger thicker cables etc, a well installed power and ground connection/wiring once you choose a good amplifier and also a similar amplifier of perhaps 4x60-90W RMS for the front and rear upgraded speakers in the cabin of the car. A setup like this, well installed and setup will have absolutely minimal distortion and will sound a whole lot better than what you currently have.
Cheers, Dennis!
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