Output voltage to subs when setting gain just isn't right

[*Ace* 10+ year member]

Hey,

I just got a new Soundstream Rubicon 2500. I got everything installed today in my car but am having problems with the output voltage to the subs when setting the gain. I am trying to set the voltage to 50volts, as I am using 2500 watts at 1ohm. I have already tested and verified that the amp is getting power, 12.5V when the car is off and 14.35 when it is on.

However I seem to have two issues. First, I have a Pioneer DEH-P5000UB headunit. It is suppose to have 4V pre amp outputs. The Rubicon has two pre amp voltage settings, .1-2V and 2V-8V. Now since my head unit is suppose to be 4V I set it to 2V-8V. However when I was setting my gain using a 0db 50HZ tone, my voltage to the subs was only 5-9V!?!?! This was with the gain knob maxed out!! So then for the heck of it, I changed my setting on the amp to .1-2V. This seemed to help a lot. Although the gain knob was still maxed out, I was now seeing ~40V on my DMM.

But this still can't be right and I want to know whats wrong. The gain knob is maxed right now, and the most I'm seeing voltage wise to the speakers is 40V, 10V's short of what I need? I had a Memphis PR.1000 hooked up before this which worked 100% fine and saw the correct voltage. The only difference was the grounding location and I used a slightly thicker remote lead cable. The rubicon is sharing a ground with my component amp at this moment and during the testing. The components and their amp seem just fine so I'm not sure if it's the ground. The only thing I can think of is maybe the remote lead cable? Any ideas?

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[cyn 10+ year member]

set the DMM to AC not DC if you already did then no idea

 

[*Ace* 10+ year member]

Yeah it was on AC of course. But no worry I already found the issue.

To everyone who has an Alpine or Pioneer head unit. Not all models put out the voltage they claim supposedly. After doing some searching I found quite a few other people with the same issue. The only way to resolve this is to turn up the bass boost function in the deck itself to up the voltage the head unit sends out. If this still isn't enough you also need to set your gain at a higher volume level. I usually set mine with no bass boost and at volume 40. With this amp for some reason I had to turn the bass boost all the way up and set the gain at volume 50. I am now getting 50 volts with the gain knob a little over halfway //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Moble Enclosurs 10+ year member]

The preamp voltage settings on the amplifier is based on a voltage impedance. So, setting it to the .1-2v setting should yield better results. You also do not want to increase the gain above a certain point or you will introduce distortion, whether audible or not. The max output voltage of the amp may not be able to extend to 50V as requested due to amplification losses which are very normal in a setup. Usually, you will see about 70% of the max voltage available with minimum distortion on an amps good day.

so, with the 2500 watt amp, you can max out at around 58.71V without losses, but get around 41.1v max with losses. Make sense?

The fact that you are getting 40v out of it shows that the amplifier can hold its own. But 2500 watt amps are generally not 2500 watts total. You are getting your 50v from the max wattage. And that's just not possible unless the specs are less than rated. And that's rarely a case.

So, you will only get about 41v out of that amp nominally without considering peaks and such.

 

[*Ace* 10+ year member]

The preamp voltage settings on the amplifier is based on a voltage impedance. So, setting it to the .1-2v setting should yield better results. You also do not want to increase the gain above a certain point or you will introduce distortion, whether audible or not. The max output voltage of the amp may not be able to extend to 50V as requested due to amplification losses which are very normal in a setup. Usually, you will see about 70% of the max voltage available with minimum distortion on an amps good day. so, with the 2500 watt amp, you can max out at around 58.71V without losses, but get around 41.1v max with losses. Make sense?

The fact that you are getting 40v out of it shows that the amplifier can hold its own. But 2500 watt amps are generally not 2500 watts total. You are getting your 50v from the max wattage. And that's just not possible unless the specs are less than rated. And that's rarely a case.

So, you will only get about 41v out of that amp nominally without considering peaks and such.

I think I get what you're saying. I know that we will never see the max output of the amp on most occasions, however I'm assuming that I still want to set the gains so that it reads 50v with the DMM using a 50Hz 0db tone, that way I'm still seeing at least around 41V nominally correct? Since if I understand correctly, If I set the gains to where I'm getting 41V with the DMM, when playing actually music I will most likely only reach ~30V right?

 

[Moble Enclosurs 10+ year member]

I think I get what you're saying. I know that we will never see the max output of the amp on most occasions, however I'm assuming that I still want to set the gains so that it reads 50v with the DMM using a 50Hz 0db tone, that way I'm still seeing at least around 41V nominally correct? Since if I understand correctly, If I set the gains to where I'm getting 41V with the DMM, when playing actually music I will most likely only reach ~30V right?

never assume when it comes to electronics. Yes, you can get it to read 50 and even higher, but can likely do some damage to your components if the amp is not meant to put that out. The amp takes the signal and amplifies it, but it does not have a brain as to say how much of a preamp is given. It takes your signal and says, here you go. So, you can easily overpower an amp over time. For instance, if you put the load at .5 ohms instead of 1ohm. The amp may not be capable of holding that input voltage from that resistance, it man will it try and give it everything it has. You are not helping its safe functionability by using bass boost either. Better to get a more powerful amplifier than try to squeeze the life out of the one you have.

And no, setting it at 41v will not bring it to around 30 peak if the music is on the same level dB reference as the tone. If not, use a tone equal to the music dB reference, which will likely be -3dB. That's why you get that drop in output from cds and such compared to digital output and tone testing. Its in the recording levels. Use a -3db tone and see how close you can get to 41v without going over. That would be better if your music will produce less output than the tone will. Because you will not be playing the tone......which is why that is of a concern to you.

And the 70% efficiency is not related to dmm levels. Dmm levels are precisely what your get. The 70% factor is only internally from the system, not the readout. That's why you have a dmm....to see what the efficiency is. So, no, setting it at 50 will not yield 41v average if you are basing that on readout voltage. What you see is what you get with readout.

So again, best thing to do is use a reference tone equal to the musical reference dB and set it that way. That's about what you will get out of it. Bass boost and increasing gain levels are only going to do slow damage. You may not see it in a few years or a few days. Better safe than sorry though.

The more important thing to note though, is that basing gain settings on maximum amplifier voltage is not the way to go. You should base it mainly on the drivers voltage capabilities and give yourself some voltage leeway by getting an amplifier with higher than nominal voltage than the driver can handle and setting it that way. Right now, you are basing it on what the amp is capable of, and not what the sub(s) are capable of. You have the possibility to blow subs that way Alsop from voltage peaks. So, if the sub(s) can handle 41v or even 50, then you should be ok setting it to music reference at 41v. That way, you are slightly underpowering the subs, or matching it as close as possible, and still getting the most out of your amp.

When getting a sub/amp setup, best to find out the voltage c,capabilities of the sub, then get an amp to power it from there with some leeway, based on the voltage minus the 30% efficiency drop off.

Make sense?

 

[subzero 5,000+ posts]

wurd.