Gain Setting Tutorial

[ingeo 10+ year member]

I tried to setup my amp to run at 500 Watts (42.72 V) the other day and the only reading I got from my DMM was 68-69V regardless of where I set the gain. The volt read never changed more then a tenth or two.

Does this mean things were clipping?

I am a little confused about the Alpine Sub Level everyone says set it to +15.

Where I am confused is some people say Alpine set this up backwards. Does this mean that +15 is full sub output?

I would think the higher I set the output the more it should be adjusting the level of the sub.

If this is correct then I fail to understand why people say this is setup backwards.

 

[thch 10+ year member]

+15 implies a gain over the baseline setting. the HU is labeled from 0 to +15, when really it should be labeled from -15 to 0, as 0 gives no amplification of attenuation, and settings lower then 0 would give attenuation.

 

[ampresearch 10+ year member]

just a quick double check.

kicker amp with a birth sheet of 1750 watts RMS x1 at 2 ohm

I have it hooked up to 2x s15L7 wired to give a 2 ohm load.

is my math correct

1750x2= 3500

voltage out put at highest listening volume should be = 59.1

now if this is right that has my sub amp gain just below half way. while playing a 40hz test tone. IF if put the gain up the very slight click to half way the voltage jumps to 63.0 but the volume gets ALOT louder IMO still sounds just as clean. is it a huge risk to leave it at half way or am i best simply leaving it the small click below with no clipping at all. i guess my question is the 4 volt difference considered enough clipping to matter? is clipping damaging at any level or is it acceptable to a certain point? the only reason i ask is becaseu the volume change is rather drastic so of course i want more output but not at the cost of the subs.

any info would be great

thanks

 

[trigger2008 10+ year member]

what should a kx1200.1 pushing 2 12L7 wired at 1ohm be showing on the DMM.

Also what should a zx450.2 pushing some comps at a 4 ohm load on each channel be showing on a DMM. Thanks for the info in advance.

 

[Rattlebrain 10+ year member]

OK this may sound like a Noob question but....

Is it the HU or the amp that initiates clipping?

What I mean is, my HU volume goes up to 35. It starts to distort around 28.(currently nothing is amped and no sub) If I set the gains with the HU at that volume, wouldn't you be able to turn the gains to 100%?

I am have a hard time here trying to figure out how to ask this question.

I guess what I'm asking is does the amp send the clipped signal to the speakers or is it the HU or is it both?

So if you were to never turn the HU above 28, couldn't you run the amp at 100% gain?

Sorry for the possibly stupid question but it is something I've wondered about and am a bit confused about.

 

[Rattlebrain 10+ year member]

OK this may sound like a Noob question but....Is it the HU or the amp that initiates clipping?

What I mean is, my HU volume goes up to 35. It starts to distort around 28.(currently nothing is amped and no sub) If I set the gains with the HU at that volume, wouldn't you be able to turn the gains to 100%?

I am have a hard time here trying to figure out how to ask this question.

I guess what I'm asking is does the amp send the clipped signal to the speakers or is it the HU or is it both?

So if you were to never turn the HU above 28, couldn't you run the amp at 100% gain?

Sorry for the possibly stupid question but it is something I've wondered about and am a bit confused about.

ttt

 

[599GTB 10+ year member]

I am running active. What freq. test tone should i use for my tweeters?

I have the same question and can't seem to find any answer to this. I understand 1kHz in an passive x-over setup but if you go active, most likely your HP is 2kHz and up. That said, what's a good frequency to use for tweeters in an active setup?

 

[wannabelean 10+ year member]

real dumb *** question...i've selected two tones for testing i.e. one for front compos and one for the subwoofer. Do I burn these two tones on two different CDs like an audio cd? the files I have are .wav files.

Thanks

 

[wannabelean 10+ year member]

I tried to figure it out myself but it was too confusing folks. Could someone help me calculate what gains I should be looking at for my front compos and sub?

This is what I have :

Alpine 9857 - all factory settings except sub vol level which is at level 15 and main vol is at 26(3/4 of max)

Front Compos are JBL - specs

Sub is JBL - specs

Kenwood 4ch amp - specs

Speaker connections

All processing has been switched off on the alpine HU. The guide says nothing about amp. Are these settings alright ?

What voltages should I get looking at for the front compos and the sub?

Thanks in advance

 

[599GTB 10+ year member]

real dumb *** question...i've selected two tones for testing i.e. one for front compos and one for the subwoofer. Do I burn these two tones on two different CDs like an audio cd? the files I have are .wav files.

You can have as many test tones as can fit on a CD -- whether they be in CD-Audio (.wav), MP3, WMA, etc. formats. Just be sure to have the track on repeat for the coresponding speakers you're testing (i.e. 1kHz for components and 60Hz for subwoofer).

Regarding your question on how to calculate what voltage to read from, it's easy. Answer these question for yourself:

1. How many watts (PER CHANNEL) is your amplifier outputing to

a: component speakers

b: subwoofer

2. What is the impedance (it's more likely 4Ohms) rating of your speakers?

3. Take the two readings above and plug them into the two blank fields on this webpage calculator.

Voila.

 

[wannabelean 10+ year member]

Thank you for the quick reply.

The front compos are rated for 70 rms @ 2ohms. The amp outputs 70rms@4ohms. I read somewhere the lower one should be considered. So sqrt (70 x 2) = 11.8v is what I'm thinking I should set the front two channel to. The subwoofer is rated at 125rms@4ohms. The amp outputs 200rms @4ohms when bridged. I have ch3/4 bridged. Considering the lower one - sqrt(125 x 4) = 22.8v.

Is my method of calculation correct?

 

[noob with an RS 10+ year member]

components arent rated with reference to ohm. they're rated with power only. so you're saying those components are rated to handle 70 watts RMS? if so, what ohm are those components? i doubt they are 2 ohm

 

[599GTB 10+ year member]

Thank you for the quick reply.
The front compos are rated for 70 rms @ 2ohms. The amp outputs 70rms@4ohms. I read somewhere the lower one should be considered. So sqrt (70 x 2) = 11.8v is what I'm thinking I should set the front two channel to. The subwoofer is rated at 125rms@4ohms. The amp outputs 200rms @4ohms when bridged. I have ch3/4 bridged. Considering the lower one - sqrt(125 x 4) = 22.8v.

Is my method of calculation correct?

That is not correct. Use the wattage that the AMPLIFIER IS RATED per channel against your SPEAKER'S OHM RATING.

Here's what you calculations should be:

Component Speakers: JBL GTO607C ---> 2Ohms

Amplifier: JBL KAC-8452 ---> 100w per chanel @ 2Ohms

Formula: 100 x 2 = 200. Sq. root of 200 = 14.1v

Sub: JBL CS1204B ---> 4Ohms

Amplifier: JBL KAC-8452 ---> 100w MONO bridged @ 4Ohms

Forumal: 100x4 = 400; Sq. root of 400 = 20v

 

[wannabelean 10+ year member]

Thanks. I'll do it and let you know of my results. I should change the operation of the bridged channel from stereo to monaural right?

 

[wannabelean 10+ year member]

components arent rated with reference to ohm. they're rated with power only. so you're saying those components are rated to handle 70 watts RMS? if so, what ohm are those components? i doubt they are 2 ohm

JBL's manual says its 2 ohms. Crutchfield says 2 ohms too.

http://www.crutchfield.com/S-e5o6O1HwRjJ/cgi-bin/Prodview.asp?readmore=true&search=gto607c&i=109GTO607C#Tab