Setting my amp sensitivity!!

[yoffer]

Ok guys, this was my first time ever doing this so go easy on me. I went out and bought a good DMM from radioshack and i also downloaded some 50hrtz test tones and put them on a cd. Now i turned my bass boost all the way up and the sensitivity all the way down on the amp. My HU was on FLAT with the bass at 0. My goal was 800rms at 4ohms. That is roughly 56.5v. I put the DMM in the Speaker terminal and played the test tone on repeat and slowly turned the sensitivity up until i reached 56.5v. Afterwards i bumped the bass boost down just a little bit and put the speaker Wire back into the terminals and listened to some music ( i did not adjust the HU settings). Just to be on the safe side i put the DMM into the terminals with the speaker wire in as well. While listening to the test tone and the speakers blaring in my ear i saw that there was only 46v instead of the 56.5v that i set without the speaker wire in the terminal. Now is this normal for voltage to drop with a load on the amp? I tried adjusting the amp with the speakers hooked up to try and reach the 56.5v mark, but there was entirely to much distortion so i backed it down almost immediately. After i set everything back to the way i originally did it, the system sounded very good with no distortion, but i just wanted to know if i did everything the right way.

[Fallen]

Don't use bass boost. Turn that right off.
It's going to wreck your response.
The voltage going down is probably because you turned the bass boost down.
Keep in mind a noticeable difference is often 3dB.
So from 800 watts to 400 would be 3dB.
400 watts is 40 volts at 4 ohms.
That's right in line with what you observed.

Set the gain again, with the bass boost off, and leave it off.

[yoffer]

Originally Posted by Fallen

Don't use bass boost. Turn that right off.
It's going to wreck your response.
The voltage going down is probably because you turned the bass boost down.
Keep in mind a noticeable difference is often 3dB.
So from 800 watts to 400 would be 3dB.
400 watts is 40 volts at 4 ohms.
That's right in line with what you observed.

Set the gain again, with the bass boost off, and leave it off.

But heres the problem, with the bass boost all the way off on the amp i cannot even come close to the 56.5v mark. Keep in mind that this is a SPL Z1X-2400D which has a rms rating of 900 watts @ 4 ohms and its powering 2 4ohm kenwood kfc-3012 which are rated at 400watts rms. If i go out there right now and turn the bass boost all the way down i wouldnt hardly hear the subs at all. I always thought that you had to have the bass boost all the way up when setting the input sensitivity so when you wanted to turn up the bass boost you wouldnt be overdriving the amp, (no distortion).

[kovemaster559]

Originally Posted by yoffer

But heres the problem, with the bass boost all the way off on the amp i cannot even come close to the 56.5v mark. Keep in mind that this is a SPL Z1X-2400D which has a rms rating of 900 watts @ 4 ohms and its powering 2 4ohm kenwood kfc-3012 which are rated at 400watts rms. If i go out there right now and turn the bass boost all the way down i wouldnt hardly hear the subs at all. I always thought that you had to have the bass boost all the way up when setting the input sensitivity so when you wanted to turn up the bass boost you wouldnt be overdriving the amp, (no distortion).

ive never used the bass boost at all just the gain and filters

[Fallen]

Originally Posted by yoffer

But heres the problem, with the bass boost all the way off on the amp i cannot even come close to the 56.5v mark. Keep in mind that this is a SPL Z1X-2400D which has a rms rating of 900 watts @ 4 ohms and its powering 2 4ohm kenwood kfc-3012 which are rated at 400watts rms. If i go out there right now and turn the bass boost all the way down i wouldnt hardly hear the subs at all. I always thought that you had to have the bass boost all the way up when setting the input sensitivity so when you wanted to turn up the bass boost you wouldnt be overdriving the amp, (no distortion).

If it isn't coming close, then your HU preout is not putting out enough voltage.
Also make sure your electrical is up. If it's dropping to 12V, then the amp won't put out nearly as much as at 14.4.(assuming it's power supply is unregulated).
If everything is ok with the electrical, and it's still not hitting the 800Wrms mark it might be necessary to get a line driver.

Do not use bass boost. It only increases the amount of bass in a narrow band of frequencies. It's usually centered around 45Hz. So in the end your upper bass and lower bass will suffer. And if you turn it up to compensate you'll end up clipping the amp if you play anything at 45Hz.

One quick question, was the bass boost on the amp or HU? If it was on the HU, that means it is capable of outputting enough voltage to drive the amp to 800Wrms. If it was on the amp, it was merely increasing the sensitivity more around 45Hz.

Now if it's a bass boost/cut knob(very few amps have this, as parametric EQs like this are more complex), make sure it's not set to cut. It should be set to 0dB.
I hope this helps.

[blackdragonx1186]

Most crappy amps like that have a horrible sensitivity, which is compounded by using low voltage output hu's. You might not have a choice but to use some bass boost. Try either getting another hu that has more output, or get yourself a line driver.

[yoffer]

Ok, i just got back from playing around with the levels. With the bass boost all the way down and only adjusting the input sensitivity i was able to get it to 31v, which is 240watts. Now, after that i reset the input sensitivity back to zero and i turned the bass boost up half way and then adjusted the sensitivity, as soon as i passed the half way mark the meter tipped out at around 46v. Ok, so i turned the sensitivity back down and turned the bass boost up to 3/4 and then adjusted the sensitivity again and a little after the halfway mark i was able to get it at 56.4-5ish. After i had set the sensitivity at that i started playing around with the bass boost, when i turned it up the voltage stayed the same, so i turned it down and until i got the 56.4v. After everything said and done, the bass boost knob is a little past the haflway mark (3/4 ish) and the input sensitivity is just shy of 3/4 way up.

Now please keep it mind that with the bass boost all the way down, i wasnt able to get anywhere near 56.5v (800 watts). But with the bass boost about 3/4 way up i was able to and i cannot hear any distortion in the speakers and they sound better now after playing around with it.

And just for reference, my HU is a Alpine CDE-100 with 2v preouts.
The bass boost was turned up on the AMP, not the HU.

[Fallen]

Originally Posted by blackdragonx1186

Most crappy amps like that have a horrible sensitivity, which is compounded by using low voltage output hu's. You might not have a choice but to use some bass boost. Try either getting another hu that has more output, or get yourself a line driver.

Agreed

Originally Posted by yoffer

Ok, i just got back from playing around with the levels. With the bass boost all the way down and only adjusting the input sensitivity i was able to get it to 31v, which is 240watts. Now, after that i reset the input sensitivity back to zero and i turned the bass boost up half way and then adjusted the sensitivity, as soon as i passed the half way mark the meter tipped out at around 46v. Ok, so i turned the sensitivity back down and turned the bass boost up to 3/4 and then adjusted the sensitivity again and a little after the halfway mark i was able to get it at 56.4-5ish. After i had set the sensitivity at that i started playing around with the bass boost, when i turned it up the voltage stayed the same, so i turned it down and until i got the 56.4v. After everything said and done, the bass boost knob is a little past the haflway mark (3/4 ish) and the input sensitivity is just shy of 3/4 way up.

Now please keep it mind that with the bass boost all the way down, i wasnt able to get anywhere near 56.5v (800 watts). But with the bass boost about 3/4 way up i was able to and i cannot hear any distortion in the speakers and they sound better now after playing around with it.

And just for reference, my HU is a Alpine CDE-100 with 2v preouts.
The bass boost was turned up on the AMP, not the HU.

Again the bass boost is essentially increasing the amps sensitivity at a narrow band of frequencies. The proper solution would be to use a line driver. The output in the 60Hz+ and 35Hz- range is going to be lacking.
Since you set the gain with a tone near the 45Hz boost frequency, it seemed to be normal. But check the output voltage at 35Hz and 60Hz. I'd be surprised if it's over the 46V.

[yoffer]

Originally Posted by Fallen

Agreed

Again the bass boost is essentially increasing the amps sensitivity at a narrow band of frequencies. The proper solution would be to use a line driver. The output in the 60Hz+ and 35Hz- range is going to be lacking.
Since you set the gain with a tone near the 45Hz boost frequency, it seemed to be normal. But check the output voltage at 35Hz and 60Hz. I'd be surprised if it's over the 46V.

Ok, so i would have to get a line driver? Considering i love alpine HU, but almost all of them are 2v preouts so getting a different brand HU is out of the question for me. What do you guys reccomend for line drivers? I was looking at the Pheonix Gold TLD22 or the AudioControl Overdrive, but the PG is deff cheaper but i wouldnt mind shelling out a extra bill for better quality. Now after i do install a line driver, what should i set the gain on the driver to? My amp can accept 8v inputs.

[Fallen]

PG usually makes decent equipment. I would imagine it would work just fine.

Before you shell out more cash though, want to check if the HU is putting out 2V?

Set it up like you did for setting your gain, and measure the voltage on the RCAs. Red prob to the pin of the RCA and black to the ring.

The 2V rating is probably peak. So expect to see 1.414V. Ideally you would have an oscilloscope to see when the deck clips.

Anywho, have you tried increasing the sub channel on the deck. If it clips the deck, don't use it. But 2V preouts should be enough for most amps...:S Most require just .2V on their most sensitive setting.

[yoffer]

Originally Posted by Fallen

PG usually makes decent equipment. I would imagine it would work just fine.

Before you shell out more cash though, want to check if the HU is putting out 2V?

Set it up like you did for setting your gain, and measure the voltage on the RCAs. Red prob to the pin of the RCA and black to the ring.

The 2V rating is probably peak. So expect to see 1.414V. Ideally you would have an oscilloscope to see when the deck clips.

Anywho, have you tried increasing the sub channel on the deck. If it clips the deck, don't use it. But 2V preouts should be enough for most amps...:S Most require just .2V on their most sensitive setting.

Ive already decided to order a line driver but i cannot find the PG line driver anywhere, it seems like it is discontinued and everyone is out of stock, so im probably going to go with either the audiocontrol or the rockford fosgate 3sixty. OH and my HU doesnt have a sub channel.

[Fallen]

For sure there isn't some place to control the level of the pre outs? I'd hate for you to drop a lot of cash on something you didn't need because it was just a setting on the HU turned down.

[yoffer]

Originally Posted by Fallen

For sure there isn't some place to control the level of the pre outs? I'd hate for you to drop a lot of cash on something you didn't need because it was just a setting on the HU turned down.

Im pretty sure there isnt. All it has is is bass and treble controls. Its a very basic unit. I really wish it had separate high and low pass filters.