Gain question. Please help!

[AndrewBR98 0]

hey everyone i am having trouble setting my gain on my us amps xt1600.2. i am using a dmm to set it and have discovered that i need to come up with a 66.3v reading at 1100 watts rms and with my sub wired at 4 ohms. i am running my headunit at about 25 which is about as loud as i want to go because the door speakers are starting to distort and sound like ass but when i do this i am only coming up with a voltage of about 20v. this is with the gain cranked all the way and my question is could this hurt anything? since im not even close to the 66.3v i am supposed to be at (someone might want to double check that for me..i would appreciate it!) could i possibly be doing any damage or clipping with the gain cranked? also on another note i have heard that i want my subsonic filter to be set around what my box is tuned to (32hz) is this accurate? thanks!

[shizzzon 461]

what frequency are you playing?

Make sure the subsonic and the LPF are not interfering with the tone u are using.

Also, adjust sub level out on headunit as increasing this will give you a stronger signal at the amp which = higher AC voltage.

make sure both rcas are in use.

make sure bass on headunit is at 0 and not in the negatives.

make sure EQ settings, if there are any, are all set to 0.

[AndrewBR98 0]

I am playing at 50hz. So I should just make sure that the lpf and sub sonic aren't at 50hz? Thanks for the reply!

[AndrewBR98 0]

Also I am still getting similar voltage numbers with all those things covered...

[tripslipfall 0]

Is the subwoofer hooked up? If it is, try unhooking it.

Make sure it's actually wired to 4 ohms, does it have dual voice coils? Dual 2? Dual 4?

Make sure the amplifier is bridged.

Also, I'm not sure the XT1600.2 will put out 1100 watts RMS... But 20 volts at 4 ohms is only about 100 watts, so something isn't right.

Edited August 2, 2010 by TRiPP3R

[AndrewBR98 0]

the subs are unhooked and the sub is a dual 2 ohm and im positive its wired at 4 ohms. im sure that if i turned the volume up more to like 40 it would register at a higher voltage but my interior speakers just distort and start to sound muddy. so is having the gain cranked all the way going to hurt anything if its not even close to the voltage it should be at?

[KU40 173]

No, it won't hurt anything. The gain isn't like the volume knob on your head unit which will start to distort after a certain point.

Sounds like you need some highpass crossovers on your front speakers.

Where exactly are the settings for your lowpass filter? Also make sure the switch is actually on lowpass and not highpass for the filter.

[AndrewBR98 0]

it is set to the low pass freq. and im not quite sure exactly what the lpf is but its around 50hz or so i would guess. is this what you are talking about for a high pass crossover? http://www.amazon.com/Scosche-XOHP-Xohp-High-Pass-Crossover/dp/B000NWHVY8 thanks for your help!!

[AndrewBR98 0]

or this? http://www.amazon.com/gp/product/B0006N41J2/ref=pd_lpo_k2_dp_sr_1?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000NWHVY8&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=07CEEWPKXZQXXQAD8YSW

[KU40 173]

Something like those could work as low tech solutions. But I wouldn't get the value of bass blocker cap that you linked to, as that's a 200 hz crossover. You'll be missing out on all of your midbass with that, even with it only being a shallow -6db slope. The Fmods only work if you have an amplifier hooked up to the speakers, as they go inline with the RCAs. Do you have an amplifier on the front speakers? If not, those won't work. If so, why don't you use the highpass filter on the amp for the speakers?

As for the crossover on the sub amp, turn it up to 80 hz. If it is set at 50 hz, you're losing output at 50 hz because the crossover point is actually the point that is already -3db, not the point at which the crossover begins to slope off. So raise it to 80 hz for the test. Or hell, just turn it off. Since you're just going to be running a 50 hz tone to set up the gain, you don't even need the crossover on while you do that.

[j-roadtatts 1,129]

Something like those could work as low tech solutions. But I wouldn't get the value of bass blocker cap that you linked to, as that's a 200 hz crossover. You'll be missing out on all of your midbass with that, even with it only being a shallow -6db slope. The Fmods only work if you have an amplifier hooked up to the speakers, as they go inline with the RCAs. Do you have an amplifier on the front speakers? If not, those won't work. If so, why don't you use the highpass filter on the amp for the speakers?

As for the crossover on the sub amp, turn it up to 80 hz. If it is set at 50 hz, you're losing output at 50 hz because the crossover point is actually the point that is already -3db, not the point at which the crossover begins to slope off. So raise it to 80 hz for the test. Or hell, just turn it off. Since you're just going to be running a 50 hz tone to set up the gain, you don't even need the crossover on while you do that.

VERY innteresting, I did not know this about crossover points.

[KU40 173]

http://www.bcae1.com/ go to either #27 or #30 on the right side.

[AndrewBR98 0]

thanks for the suggestions guys..i will look into that. but today i was messing around with it and brought the volume up to 30 and it read 53v or so..i then hooked the subs up again and readjusted my eq and this point the gain was all the way cranked on the amp and i started to hear what sounded like clipping from the sub on a song that hit about 33hz or so. could my us amps xt1600.2 not be putting out 1100 rms like it says? and possibly need a lower voltage rating maybe around 800 or 900 rms? just throwing it out there

[tripslipfall 0]

thanks for the suggestions guys..i will look into that. but today i was messing around with it and brought the volume up to 30 and it read 53v or so..i then hooked the subs up again and readjusted my eq and this point the gain was all the way cranked on the amp and i started to hear what sounded like clipping from the sub on a song that hit about 33hz or so. could my us amps xt1600.2 not be putting out 1100 rms like it says? and possibly need a lower voltage rating maybe around 800 or 900 rms? just throwing it out there

It's definitely possible, I heard XT line was overrated but I'm not sure.

[KU40 173]

What headunit do you have? Does it have crossovers on the RCA outputs you are using?

[95Honda 486]

It is pointless to do any of these voltage calculations without knowing the impedance.....

[AndrewBR98 0]

the head unit is a sony cdx gt24w and im not sure if it has a crossover. also the sub is wired to 4 ohms so thats what im going by. should i maybe be reading it at 2 ohms because it says to look at the impedance coming out of 1 channel i believe.. but its bridged so i got confused.

[AndrewBR98 0]

i looked and it says it has an active crossover?

[KU40 173]

ok. Are you using front, rear, or sub RCA outputs on the head unit? Find the crossover menu on the head unit for the output you are using and see where it is set.

Reason being, if you are using a front or rear RCA output, the crossover on the head unit for those channels will be HIGH pass, thus completely attenuating the signal to the sub amp. If it is on a sub channel, it should be a lowpass crossover, but perhaps it is set too low, like 40-50 hz, thus also attenuating your signal.

[95Honda 486]

Again, you don't have any clue what your impedance is, so all of this is a waste.

[AndrewBR98 0]

Again, you don't have any clue what your impedance is, so all of this is a waste.

i apologize...this is a new hobby to me and im still learning. i understand that impedance is the ohm rating? if so the amp is at 4 ohms which on the box states that it will produce 1100 watts rms x 1 channel. the sub is wired at 4 ohms...if this is not what you mean please help me out. thanks!

[AndrewBR98 0]

also the manual said that it has a built in lpf and hpf but im not sure if they are adjustable? i just purchased the head unit so i am still learning about it but after messing with it for about an hour i still couldnt find a way to adjust those.

[95Honda 486]

The impedance costantly changes with frequency. So if you don't meaure it at the frequency you are taking your voltage readings at, you hav eno idea what power levels you are dealing with.

This all boils down to the numerous posts we see on here that say "I set my voltage at 53.6753V blah, blah, blah" that have people thinking they are doing something productive when all they are doing is playing wiht a bunch of crap they don't understand.

Set the gain by ear. It is really easy if you have one amp. If it starts distorting, you have it too loud, turn something down.