Gain setting with DMM

KHPower · Post by **KHPower** » Mon Sep 29, 2008 4:20 pm

I need some help , that nifty calculator from car audio 911 does not exist and I am trying to set up my line driver and RSD 1200.1 to a 1200 rms rated sub. Is there any calculators anywhere or can some one give me the voltage?

Thanks

Post by **stipud** » Mon Sep 29, 2008 4:43 pm

Just type it in google...

voltage = sqrt ( impedance * wattage )
voltage = sqrt ( 2 * 1200 )

So google "sqrt ( 2 * 1200 )"...
sqrt(2 * 1200) = 48.9897949

KHPower · Post by **KHPower** » Mon Sep 29, 2008 5:05 pm

stipud wrote:Just type it in google...

voltage = sqrt ( impedance * wattage )
voltage = sqrt ( 2 * 1200 )

So google "sqrt ( 2 * 1200 )"...
sqrt(2 * 1200) = 48.9897949

Thank You very much I appreciate it! So rounded out 48.99?

Post by **stipud** » Tue Sep 30, 2008 6:15 am

Yup. Although that amp is capable of well over 1200 watts you know. You can DMM it at 1400-1450 if you like.

Also, you might not be happy with a gain matched subwoofer amp. I normally do my gain matching with my LPL at a lower setting, then use it to turn up the bass on quieter songs. Much more tunability that way. I always gain match everything else though...

KHPower · Post by **KHPower** » Tue Sep 30, 2008 8:55 am

I read that you do that in another post the other day and was considering it. i used to use my lpl with my ax204a and now that its outta the equation I will try what you do and have it set on the lowest or 1/4 level of the lpl.

The reason I was going to gain match this amp to this particular woofer is because this Bahn Eternal sub is the most pickiest sub I have seen and it seemed to not like my 2200HCX or my ZX500 but now with my 1200.1 it seems to take the power and like it.

what do you recommend I do ? I would kinda like a little head room with this sub and amp. And would you say matching it at 1400 watts would be a safer closer bet then at 1500?

Post by **stipud** » Tue Sep 30, 2008 8:58 am

Yep, I would do 1400 personally. You can do it anywhere on the LPL range as long as you remember where it is. I set it at 1/4 and put a mark on the LPL so that it is pointing vertically when you are gain matched.

KHPower · Post by **KHPower** » Tue Sep 30, 2008 9:20 am

Sweet! i did your google recommendation and got sqrt(2 * 1 400) = 52.9150262

Does that sound about right?

Also , I will go with the 1/4 setting on the LPL , that sounds like it will be a perfect match for myself and my current sysytem

Thanks

Post by **stipud** » Tue Sep 30, 2008 9:49 am

You got it. If you can't reach that voltage at 1/4, you might have to do 1/2. Depends on your system voltage... if you're running 8 volts it will be no problem

KHPower · Post by **KHPower** » Tue Sep 30, 2008 10:32 am

Actually I am running a straight 7.88 volts because for some reason my basscube will only alow that exact voltage as its top throughput voltage.

I shouldnt have a problem at 1/4 considering I can turn up the gain settin g on the amp if need be correct? Im a little confused

Post by **stipud** » Tue Sep 30, 2008 10:49 am

With 7.88v you will have plenty of room on the gain knob. The problem is if you have 1 volt and want to do the LPL trick... then you can't set the LPL very low since you are already near max gains, just to support base voltage.

KHPower · Post by **KHPower** » Tue Sep 30, 2008 12:19 pm

stipud wrote:With 7.88v you will have plenty of room on the gain knob. The problem is if you have 1 volt and want to do the LPL trick... then you can't set the LPL very low since you are already near max gains, just to support base voltage.

Gotcha! and now I understand a little better because I was just out in my van and hooked up the LPL to the amp and set the LPl to 1/4 and lost alot output so I guess I should try setting up the LPl at around 7/8 the way up? and then from there set the amp gains?

I also would like to use the LPL not just for a small boost(well thats all I am going to get) , but my use would be completely opposite of yours Stipud. I would want to turn the amp way down at times instead of using my eclipse HU because while driving the new eclipses are not the easiest to navigate to turn the output level down.

Too bad my SLD-44 doesnt have a votl level thing.

Post by **stipud** » Tue Sep 30, 2008 12:31 pm

If you want to turn it down, just set your gains with the LPL at max. If you want to turn it up, set your LPL lower. Pretty simple.

KHPower · Post by **KHPower** » Tue Sep 30, 2008 12:32 pm

Perfect! Thank You ! I will have to see which best suits me

deathcloud · Post by **deathcloud** » Thu Oct 02, 2008 9:27 pm

So I am kind of getting this but still a little lost. Let me give you a scenario and see what you would do Stipud and anyone else could chime in.

I just want to do it the way that the SLD-44 says to do it and that is get a 60 hz wave from the websites you have then put my volume 3/4 and then with the SLD-44 turned down and the amp turned down slowly start turning the sld-44 up until it peaks or blinks. Then I would turn it down a little until it doesn't peak like it says to do. Now this has nothing to do with using a DMM so is this bad?

Is there something I am missing...

Or I could do what Bfowler did and measure my SLD-44 output RCAs at a certain voltage... lets say I put the 60hz CD in 3/4 volume then hook up the leads to the RCAs and turn up the SLD-44 till it hits 10 volts, then I plug that into the amp. THEN do I hook up the leads to the xenon amp and read the volts comming out of it? it should be around 28.28 volts right? and lets say its not then do I turn up my amp sens till it hits 28.28 volts? is it going to clip? I just am going to do the install monday and want to be pro!

bretti_kivi · Post by **bretti_kivi** » Thu Oct 02, 2008 11:23 pm

personally, I'd go for the second of those. Why? the first one doesn't make sense - turn the SLD up to close on its limits (if it says 10V, maybe

and then repeat the process with the amp.

Bret

Post by **stipud** » Fri Oct 03, 2008 6:20 am

No, that sounds just about right deathcloud.

There are two ways you can do this... you can either measure the RCA voltage, then set the amp gains.... OR you can get two birds stoned at once!

Leave the RCAs connected to the amp, with both of the gains turned down. Now increase the SLD gains until you reach your desired AMP voltage (in your case 28.3 volts). If your SLD clip light starts to flash before you reach this point, turn it down until just before it starts flashing, then set your amp gains to achieve the extra bit of voltage.

bretti_kivi · Post by **bretti_kivi** » Fri Oct 03, 2008 12:54 pm

So, the SLD has a "clip" LED too? If you're using a test tone, of course that makes sense, because if you push it (at a digital, source level 0dB), then you know you've just stepped a little over the line. the first makes more sense now.

How's the clip LED implemented? Is it known?

bruther · Post by **bruther** » Tue Jan 27, 2009 7:03 am

I'm so freaking confused with this whole process........

I'm running 2 600.2's
1 is being run two components......4 ohm
1 is running dual voicecoil (so 2ohm) subwoofer.

Help..... lemans terms...Help....help....help...

Please help...

Post by **stipud** » Tue Jan 27, 2009 7:19 am

bruther wrote:I'm so freaking confused with this whole process........

I'm running 2 600.2's
1 is being run two components......4 ohm
1 is running dual voicecoil (so 2ohm) subwoofer.

Help..... lemans terms...Help....help....help...

Please help...

600.2 does 150x2@4 ohms, so...

sqrt(150 watts * 4 ohms) = 24.5 volts -- measure it out of ONE channel

As for the sub, that's a bit more complicated. The amp is 600 watt 2 ohm stereo/4 ohm bridged load optimized. If you were going to run it at 4 ohms bridged the formula would be:

sqrt(600 watts * 4 ohms) = 48.9 volts

You would measure this across the terminals BRIDGED.

However, at 2 ohms this means the amp will try to produce 1200 watts:

48.9 volts ^ 2
---------------- = 1200 watts
2 ohms

This will cause moderate clipping, and the powersupply will have to regulate itself. Instead, I would recommend setting your gains at 2 ohm a bit lower, to 600-800 watts.

sqrt(600 watts * 2 ohms) = 34.6 volts

bruther · Post by **bruther** » Tue Jan 27, 2009 1:02 pm

So where do I test this....coming out of my SLD44 or coming at the speaker output level on the amps??

Post by **stipud** » Tue Jan 27, 2009 1:11 pm

bruther wrote:So where do I test this....coming out of my SLD44 or coming at the speaker output level on the amps??

Your SLD has separate gains and puts out 8 volts. You measure it separately from the amplifiers.

Disconnect the RCAs from the amp. You would measure the RCA + (pole) and - (shield). Set your headunit to 3/4 volume and increase the SLD gains until you read 8 volts, or the clip light starts flashing (whatever comes first).

Then go back to your amp, and with the speakers disconnected...

On ONE of the front amp channels measure 24.5 volts (2x150 watts @ 4 ohms)

And BOTH sub amp channels bridged measure 34.6 volts (1x600 watts@2 ohms)

That's it

bruther · Post by **bruther** » Tue Jan 27, 2009 6:29 pm

stipud wrote:
bruther wrote:So where do I test this....coming out of my SLD44 or coming at the speaker output level on the amps??
Your SLD has separate gains and puts out 8 volts. You measure it separately from the amplifiers.

Disconnect the RCAs from the amp. You would measure the RCA + (pole) and - (shield). Set your headunit to 3/4 volume and increase the SLD gains until you read 8 volts, or the clip light starts flashing (whatever comes first).

Then go back to your amp, and with the speakers disconnected...

On ONE of the front amp channels measure 24.5 volts (2x150 watts @ 4 ohms)

And BOTH sub amp channels bridged measure 34.6 volts (1x600 watts@2 ohms)

That's it

What setting do I set my DMM to?

thedeal7235 · Post by **thedeal7235** » Tue Jan 27, 2009 6:51 pm

ac volts, or at least thats whats worked on my cheap radio shack one, and my system sounds GREAT!!!!!!!!
imho, the best part of this method, is you can truly, equally get both left and right channels EQUAL @ SAME LEVEL; B/C, IMHE,DIALS,wether you have independent left and right gains, or a single gain( such as on the amps) truly aren't equal-
i may go ahead and take my sld-44 out just to look at the gain pots, i can clearly see on my mx3i though, the mids independent left/and right gains arent in the same place(meaning the dials dont match) but with the dmm they do!!! and, b/c u have the sld-44 YOU are going to have even MORE control, imho, set both rca outs to 8volts, thus ur amps are getting 8 volt inputs, just my 2 cents
-stipud explained better than i did( once u do this 3-5 times youll have it down, trust, it took me awhile to get, and im not stupid, or a rocket scientists, or a spelling bee winner either

mayb adjust it the way u think it sounds good(w/out blowing anything up-then use this method, i GUARANTEE your going to hear night/day difference, and ur amps will last longer, and ur speakers too,this is, all my experience though (after reading it here several times)- U CAN DO IT!!!

bruther · Post by **bruther** » Sun Feb 08, 2009 12:13 pm

I need help help help again.......
If anyone is bored and can help walk me through some of this....PM me and I'll give you my cell number.

I turned the Head Unit up 3/4 of the way ( which is 22 out of 31)and had the gains on the SLD44 turned all the way down along with turning the Amp gains all the way down. The clipping or (signal, orange light) on the sld44 is staying on almost constantly when playing a 80 hertz sine wave......I also played some test tones and it stays on the whole time as well...... Need some help....since I can't back down the gains on the sld44 anymore should I being turning the head unit down to say maybe 18 or 15 but then that would be 50% of volume level for the head unit and then start turning up the gains on the sld44.......

Somebody help PLEAASSEE

bruther · Post by **bruther** » Sun Feb 08, 2009 12:22 pm

What setting on my DMM should I use?