hey everyone,

so finally got my amp and sub installed but when I play my 50hz test tone as per direction of some gain setting tutorials (to match the max volume to the amp to prevent clipping), the cabin woofers are also responding so it is very hard to do this by ear. I unfortunately do not have access to an oscilloscope or any other instrumentation so I'm running the risk of damaging my amp/sub right now.

any advice? Should I be doing this with the bass setting on the headunit set to the middle or all the way up? Most audio shops I know just play it by ear and will probably do it incorrectly. How did you guys set yours? Do you know the voltage of the stock Bose headunit that I can just match on my amp? Anyone in socal know where I can use an oscilloscope for free/cheap? Thanks for your help

good info: http://www.bcae1.com/gaincon2.htm

 

amp: mrp m500
sub: alpine type are 12in

should I just set the headunit bass level to the middle value, turn up the volume with the 50hz tone playing up to one notch under the cabin speakers clipping and then go set my external amp gain to a level where the sub is not clipping? Then when I play songs that are not bass heavy I can turn it a bit via the headunit controls and then put it back to the middle to be safe when bass heavy music.

 

with the stock bose i set my mrp350 by lowering the crossover all the way then raising the base 2 ticks below max, volume at half (where i usually listen to the stereo). i adjust the gain to .5V and then the boost is about halfway. i noticed that the sound is very much below par for when i had my setup (mrp350 and type-S DVC 10" sub in ported box) hooked up to an actual alpine head unit. it seems that the levels from the bose system are very low and require some upwards adjustment.

i adjust overall bass using the head unit adjustment, when desired. i honestly think you're better off adjusting the amp to your taste at the normal volume you listen to the system at. don't adjust to clipping, don't keep it super low, just where ever you find yourself normally listening to the system.

 

If you're feeding the aftermarket amp from the BOSE sub connector before the BOSE amp as opposed to speaker connectors, then any bass setting over 0 on the HU has no effect on the input your aftermarket amp. In other words you can use the HU bass **** to attenuate your entire bass response BOSE and SUB by going below 0, but it will only increase bass to the factory BOSE system i.e. your speakers when turned up past 0.
If you have a digital multimeter, you could use it to set the initial gain to prevent clipping, and then attenuate the amp as you see fit to match the factory system.
The generic formula you could try is: desired power output multiplied by impedance equals the square root of target output voltage. In your case if you are hooking up the sub in a 4 ohm configuration, the amp is designed to produce 300 watts when seeing a 4 ohm impedance. 300W x 4 = 1200. Square root of 1200 is 34.64. Play the 50 Hz tone with the HU volume at about 75% of the way up, with the sub disconnected. Hook up the multimeter to the amp sub outputs to measure AC voltage. Start with the gain at its lowest setting and bring it up until you reach 34.64 volts. At that point your amp should be producing ~ 300 watts. If you were to use a 2 ohm sub, the target output voltage would be 31.62 volts to achieve 500 watts that the amp is designed to produce when presented with a 2 ohm load.
Keep in mind that this is a good starting point, and that you'll ultimately use your best judgement when it comes to the way your system sounds best to you.

 

thanks for the responses guys. I tapped into the harness pre factory sub so the bass **** controls the interior bass as well as the the new sub. It sounds good right with my random configuration. Bass boost set to zero and gain set halfway between nominal and max.

the reason it is set like this is because I like to hear the bass in my music that isn't bass heavy like some alternative bands. I set the gain so that when I listen to these types of music I just have to turn the headunit bass control to max to get decent drum kicks etc (just how it should sound nothing crazy) when I listen to hip hop or rap the stock bass is set to the center bass setting and it is pretty boomy, but I might go up or downs tick or two depending on circumstance. I think the sub is fine in these instances.

I like to push the sub occasionally and get the cabin rattling good from time to time and this is where I am scared I m damaging it cause I never calibrated it from clipping. I had a 1000W rms amp pushing an alpine type x in a previous car and that thing blew me into the sky constantly lol so my current 500W rms setup is hard to determine if I'm trying to get too much out of it.

I really wish I knew if I was clipping it or nor, other than that I think the bass controls in the stock system do a good job of calibrating how much bass is needed on a song by song basis. I'll try to invest in a DMM thought and see where my gain should be so I can estimate what I should be hearing when I am pushing the sub with bass heavy music and not actually damaging it.