Gain Setting Tutorial

[dvrmstrng 5,000+ posts]

56 dam i was way off....alright can anyone else back that just to make sure

 

[asaner85 10+ year member]

How do I do this if Im using a 4 channel. Where do I put the DMM leads? I mean should I put the leads as if I was bridging the front L/R, Or in each individual channel?

Can somebody tell me the voltage I should set my gains to? 4 X 75W at 4ohm. And 1100W at 1ohm.

Thanks!!

 

[2006F150Screw 10+ year member]

Problem setting gains I guess but my radar detector and seat belt reminder chimer is louder than this setup. I figured this system would be ear splitting loud.

I figured my gain settings to be 24.49 on Lrx-2.500 (sqrt of 200x4) and on the Lrx2.250 to be 20 (sqrt of 100x4)

Any suggestions would be great.

Here is my system setup:

-2006 Ford F150 Super Crew

-Pioneer AVIC-D2 Navigation Head unit.

-Audison Lrx-2.500 (200w x 2 @ 4 ohms rms) powering 6.5 " Rainbow Germanium

Comps.

-Audison Lrx-2.250 (120w x 2 @ 4 ohms rms) powering 6.5" Rainbow Coax.

-JL Audio 500/1 powering JL Audio 10Wv2 sub in a stealth box.

Audison amps are both wired from head unit to the input on the amps (not the output).

I'm running passive setup.

I used both 50 hz, 60 hz, and 1000 hz test tone (not at once but independently and than hooked speakers up after each test tone and turned radio on but not much different)

I tried setting gains using DMM with the DMM leads hooked into the speaker terminals on amp.

I have all eq settings on HU either off or set to flat.

I have volume on HU set @ 47 (75 % of max volume on radio which is 62).

I tried with both low pass and high pass filters on amp turned off and also tried with filters turned on. and set the Lrx2-500 gain setting to 24.49 on DMM and on the Lrx2.250 gain setting till I got 20 on DMM.

After doing this I was all excited turned truck on cranked radio to 48 and just wasn't don't know how to say it LOUD (it was loud but not LLLLOOOOUUUDD).

Even tried after this turning EQ on and messing with settings and low mid and high freq. are set @ +2.

Any suggestions are recommendations or something I did wrong please help me.

Below is the link to the settings on the Audison amps.

http://www.audison.it/content/eng_lrx2manuale.pdf

 

[luvinthebass 5,000+ posts]

ya clipped the amp goin over that volume setting you set the gain at

 

[luvinthebass 5,000+ posts]

I tested a few Pioneer CD players preouts the other day. With all processing off, the front/rear preouts all clipped @ volume 61/62.

I have a Pioneer CD player and my volume goes to 30 and i'm guessing it prolly clips at 29/30 with the SLA (source level adjustment) at +4 the highest it goes so i should reset my gains for 3/4 then instead of volume 20?

 

[geowick07 10+ year member]

i have a hifonics amp that is rated at 2000w rms, but it is over-rated. probably around 1800w rms. so my amp output voltage should be........42.43 volts or in the neighborhood, right? just checkin. does the number of drivers have any effect on this number? i am running 2 alpine type-r's wired to 1ohm. do i have to change anything? or just test until i have the desired voltage?

 

[creyc 10+ year member]

could someone tell me roughly what voltage im looking for....800 watts @ 2 ohms?
thank you in advance....i was guessing 40volts

You were right.

800 x 2 ohms = 1600

sqrt 1600 = 40V

 

[dawgdan 10+ year member]

Setting gains by ear > DMM method

 

[seg_representin 10+ year member]

do put impedence rise into effect?

 

[Rochambeau 10+ year member]

OK, I am gonna need some help on this. Because of the design of the amps, I am unsure if they follow the same basic formula as outlined here.

The amps are Alpine PDX and what confuses me is that they are rated at the same power regardless of the impedance of the speakers. Therefore, should I use the same formulas?

Using the forumulas as stated here is what I got (wattage gleaned from birthsheets):

PDX 4.150 bridged into 3ohm Boston Z6's: sqrt(3*318)=30.88v

PDX 2.150 into 4ohm Boston SL-80's: sqrt(4*171)=26.15v

PDX 1.1000 into 2 Boston GL512-44's (dual 4ohm voice coils, each sub wired for 8ohms): sqrt(4*1124)=67.05v

Does all this hold up?

Thanks.

 

[bimmeracer 10+ year member]

quick question. i am confused about one part when setting up a subwoofer. I have figured out that i will need to tune the gain to 40v, but what should the lpf be set to when adjusting the gains?

and i assume the bass boost should be set to the 0 or the minimum when setting the gains.

also after adjusting the gains, should i adjust the lpf or bass boost first?

 

[Rochambeau 10+ year member]

Just put the lpf where you would normally have it (80hz is a popular setting) prior to setting the gain.

Put the bass boost where you will normally have it, taking note of what the center frequency of your bass boost is (it will be included in the specs in your manual). If it is 45hz, for example, use a 45hz test tone and set your bass boost prior to setting the gains.

Carputer, eh? The ultimate car gadget! If I had a use for it, I would so go for that! 7-foot screen too! //content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif How do you get the doors closed?

Sorry couldn't resist, you may wanna make that a double quotation mark (inches) rather than a single quotation mark (feet). //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[bimmeracer 10+ year member]

lol thanks. I love my carputer.

 

[tracyrick 10+ year member]

1. Looking for the cheapest Digital AC Voltmeter possible that will still work at least once for my amp install. Any recommendations? Links...?

2. Best test tone link? I think the one above is broken.

Thanks.

 

[XTRProBoy 10+ year member]

I dunno about this whole setting method really... I mean I tried this today on my newly acquired HCCA-D2400 and I must say this did not work out well at all.

Considering I'm supposed to be getting something near 1200W into 1-Ohm that means I should be looking for 34.64 VAC right?

So I tried that, with a 50Hz tone at 0dB (verified by the signal meter on my MD deck when I recorded it) and then I went out and tried this in the car.

Keep in mind I *just* got this amp so I hadn't even installed it doing the "by ear" method yet...

I have a few DMMs including a Fluke 77 but I used my UEI one because it has TrueRMS on it. Sure enough it indicated 50Hz cycle frequency and then I set the gain so that the output voltage was around 34V AC (RMS). And I must say when I played some music it appeared to me I had just installed a 120W amp and not a 1200W one, LOL.

Head unit was up so there were only two more "bars" before full volume (a Sony CDX-C7850 but connected to an XDP-210EQ) when I did the gain setting. I tried again, going to about 40V instead, and then reconnected everything but again to no avail. The sub sounded waaay underpowered to me with music playback.

So then I remembered the way Orion used to say to do it with the DMM (back before they were taken over by DEI this info was on their website). Instead of setting the gain to some calculated voltage they said to turn the gain up until you see the voltage stop increasing rapidly and sort of level off, then turn it back a bit. I did this and it "slowed down" at around 70V and maxed out at 72.x volts before I hit the stop on the gain knob. So I dialed it back to around 68 volts and left it there.

Connected everything again and tried once more and I have to say it was sounding *much* better.

This was at maybe around 66% of the knob travel I think? With the input voltage range on the amp stated as 150mV-5.0V I believe. So I'm not sure what its set at in terms of input voltage, but I'm thinking it has to be around 1.5V or so. The XDP-210EQ is supposed to have 4V output all around, so I think I've either set a 2.5:1 gain overlap (or 2:1 if you consider that 34V figure "right" as I had about twice that voltage from the amp) or the whole JL audio method is messed up, lol. 0

But honestly I don't get how the root of the product of power output and impedance driven works out like that. Because say I had my sub wired for 4 ohms (instead of 1), then I would be looking at 450W from the amp and therefore it would be (1800W*ohms)^.5 = 42.42V . Why would I set the input stage gain such that the output voltage from the amp, with no load connected (as JL tells you to do), was at a higher speaker output voltage on the amp?

How does that make any sense? Because the only difference with no load connected would be me making the amp's input stage more sensitive and nothing else. I.e. All I'd be doing would be making the amp more sensitive for the 4-ohm load (42V) as opposed to the 1-Ohm load (34V). But for what reason??? The RCA level from the HU did not change, so why would I look for a higher no-load voltage on the speaker terminals if I were driving a higher impedance? I don't get that. Because gain is supposed to match the amp's input stage with the RCA level it receives from the HU. How does that have anything to do with what load impedance I'm driving? Especially considering you measure the outputs of the amp with no load connected (other than the DMM itself).

I dunno but the Orion method seems a lot better to me. However I don't remember if you were supposed dial up the gain with the load connected to the amp or not, but I just did it without since I didn't want to deafen myself, lol...