Setting Gains on Overrated amp.

[kicker06 10+ year member]

I've wondered this forever, and I am finally going to ask.

MY amp is a Hifonics bxi-1500d.

Rated @ 1500wrms @ 1ohm, more realistically around 1000-1200 depending on voltage. When doing the calculation for the amount of volts needed to power my sub, what should I try to set the amp too?

1200w Seems like a realistic figure. So when I do the calculator I just plug in 1200wrms and 1ohm and then I should get my voltage.

Also, when setting the gains, I realize I need to turn off all the settings on the HU, but what should I have the phase, Bass EQ or Bass Boost set at when I am using my DMM to find the voltage?

Also, do I have to unhook my 6.5" Speakers when playing the 50hz test tone? I have the speakers crossed @ 125hz on the headunit, so they shouldn't play the tone anyways right?

Thanks!

Also I realize the two stickies, I have read throughly, but I don't see the point of setting it to 1500w if it's realistically going to put out 1200w.

Click to read more...

 

[Immacomputer 10+ year member]

I would recommend using your ear with that amp. I would disable all crossovers and play a 60hz tone (You can disconnect your front speakers if you want to but it's not needed). Boost the gain until you hear the sound change then back down a little. From there, lower the volume some and play some sweeps from about 25-80hz and watch for over excursion. Play the sweep and start moving the volume back to where you had it when setting the gain with the 60hz tone. If the sub starts to mechanically struggle, back of the gain a little more.

 

[kicker06 10+ year member]

I would recommend using your ear with that amp. I would disable all crossovers and play a 60hz tone (You can disconnect your front speakers if you want to but it's not needed). Boost the gain until you hear the sound change then back down a little. From there, lower the volume some and play some sweeps from about 25-80hz and watch for over excursion. Play the sweep and start moving the volume back to where you had it when setting the gain with the 60hz tone. If the sub starts to mechanically struggle, back of the gain a little more.

This is going to a napalm, so there will be no over excursion or overpowering.

So I should turn it up until I hear that there is a difference in sound?

What should I do with the phase, bass boost and such?

 

[Immacomputer 10+ year member]

Don't touch the bass boost - keep it off. The phase won't make any difference really. I'm not sure about that amp but if it is just a 0 or 180, it will be the same thing as reversing the polarity - nothing. If it's adjustable from 0-180, it can help the sub blend better with the front stage but it won't effect the levels.

If you slowly adjust the gains with a 60hz tone, you should be able to hear a slight difference in sound, almost like a mild buzzing noise. I'll see if I can make a 60hz tone and then a 60hz clipped tone and post them so you can listen for yourself.

 

[Immacomputer 10+ year member]

Here are two tones for you:

60hz, no clipping: http://media.putfile.com/60hz

60hz, minor clipping: http://media.putfile.com/60hz-Clipped

Open them with windows media player and set the visualization to Bars and Waves: Scope. From there, play each wave and you can see what they look like.

 

[kicker06 10+ year member]

Ok thanks.

I had my previous sub set up by a shop. They had amp at FULL gain and had the bass eq set at 3/4 full. Ill just turn it off.

So I should set my SSF to 20hz, since my box is tuned to 30hz, and set my low pass to 80hz, which is where it is set on my haedunit as well (Ill just turn my HU Filter off).

After I have set the amp, can I turn on my loudness again on my headunit among other things?

 

[Immacomputer 10+ year member]

No. Have the headunit set up just like you are going to listen to music. I suggest setting the bass to flat and loudness on low or off.

Once you set the gain, the only thing you should really change on your headunit is the volume. Once you start increasing things, you can cause the amp to distort even more.

 

[kicker06 10+ year member]

Well my speaker amp is set already with medium loudness among the many other settings that the headunit has.

 

[Immacomputer 10+ year member]

Well keep those settings then and adjust your sub amp with those same settings but start with the gain all the way down and the volume to the max that you can listen to the front stage at.

 

[kicker06 10+ year member]

48/53(or 54)

ok cool, Thanks man!

 

[kicker06 10+ year member]

Well at 48/54 volume, 60hz tone, gain full, bass eq @ 3/4...it read 63.4v

lol that's super high. I am going to lower it down to 34.6 volts which is around 1200wrms.

Sound good? Ill turn bass eq off.

Also, the when the volume is that high, setting my amp to max around the 3/4 mark is fine right?

EDIT: Ok got it at 34.6v which reads from the speaker terminals. Turned the bass eq to 0 and adjusted the SSF to 23hz and Low Pass to 85hz.

We are good too go.

Also it was weird, when I played the 60hz tone (speakers are crossed @ 125hz on the HU) sound came from my SSCS6's. I just unplugged the RCA's from the speaker amp so I wouldn't damage the speakers, but the speakers shouldn't see that freq if they are high passed @ 125hz, right?

 

[Immacomputer 10+ year member]

Also it was weird, when I played the 60hz tone (speakers are crossed @ 125hz on the HU) sound came from my SSCS6's. I just unplugged the RCA's from the speaker amp so I wouldn't damage the speakers, but the speakers shouldn't see that freq if they are high passed @ 125hz, right?

That's normal. Crossover points do not eliminate frequencies below the level but rather lower the volume of those frequencies by what ever the slope is per octave. the steeper the slope (ie: 12dB/octave, 18dB/octave, 24dB/octave), the lower the volume level will be for frequencies below the crossover point.

 

[kicker06 10+ year member]

Oh ok, I see.

Tomorrow I'm going to reset the gains because I want to change some things on the headunit.

But anyways, it worked well and I am happy.

Thanks for the help!