I have two memphis audio street reference subs, 12 inches. My speakers are two pairs of Alpine SPS-619s, And my amp is a Pioneer GM-3500t.
I got this all installed by a professional car audio shop. I want to figure out what the problem is before I drive all the way back there. The bass is fine when the volume is at a reasonable level, but when I try to turn up the volume bass fades and you can barely tell there is any. And there was one time when the treble was muffled and starting to become fairly faint.
It would be greatly appreciated if someone could give me some advice. Thanks in advance.
Ok there could be a number of reasons for this happening, one of the likely reasons is that the original speakers were higher impedance compared to the aftermarket ones, say the stock speakers were 6 ohm and the aftermarket ones are 4 ohm. Or the HU limiting bass at higher volume to protect the original speakers.
To make sure each speaker is in it's own channel you should be able to both fader and balance, connecting more than one speaker to the same channel can also create issues.
If this just functions like that then likely you would need to continue your upgrade by changing the stock HU to an aftermarket one, best, one that has independent subwoofer outputs, and this needs not to be that expensive:
Now the other thing to check is that the subs are connected independently to each of the amplifier's channels and NOT paralleled and that the amplifier is powered correctly, it should have a power line directly connected to the battery.
I had another question that is not relevant to my first post. My friend has a single 10 inch sub power by 1400w amp. His bass is a lot better than mine, how would I go about increasing my bass? I am assuming it is because I have such a weak amp? If this is right what kind of amp should I replace it without? I really enjoy my bass by the way, but then I do not want to drown out all the lyrics and everything. If anyone can help me out it'd be greatly appreciated.
There is not enough infos to tell you why are you doing so bad, the usual suspect is the box being misdesigned and you should be sourcing 200 RMS to each sub, for a complete system makeover get Sundown E12 subs are in the price range of those memphis and will perform better than the kickers as well.