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Setting gain with DMM

 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 209
Registered: Mar-10
i no this has ben covered many times, but can someone please explain just one more time how to do this for a sub amp.

or even just a good link would be great.

and what is the best tone to do this with for a sub amp. 50hz, 60hz? i've read pink noise is good to use for sub and component amp's. ware can i find that?

tyvm, i know these same questions get old but i just wana do it right, even though it's not full proof it's still better then setting it buy ear, right?
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2203
Registered: Nov-07
many people argue over this. some people are set on going by ear and some are set using a dmm.

i dont trust my ears - so i set with a dmm and use a 50 hz tone.

Figuring your target voltage
Example:
Say the amp provides 1000WRMS into a 1 ohm load:

Voltage = sqrt(1000W X 1 ohms)
Voltage = sqrt(1000W*ohms)
Voltage = 31.6v

descent video:
http://www.edesignaudio.com/gains_video.php

like in the video - 400w into a 4 ohm load
Voltage = sqrt(400W X 4 ohms)
Voltage = sqrt(1600W*ohms)
Voltage = 40v

You can get other tones at ROE

http://realmofexcursion.com/index.php?pageid=audio_downloads
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 210
Registered: Mar-10
ok, great. if i did it right than it looks like i'm looking for 54.7v thanks again daniel.

so do i just leave the sub hooked up, or do i disconnect it from the amp and only have the leads from the dmm going into the speaker input's. iv'e heard leave it hooked up, and NEVER leave it hooked up when you'r doing this. how do you do it?
 

Silver Member
Username: Skdooley

Roanoke, VA Usa

Post Number: 847
Registered: Oct-09
The above strategy works great. Play at 75% volume with everything on the deck at zero. Some suggest setting at 85-90% to allow extra room for bass and such.
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 211
Registered: Mar-10
well i guess my previous question is stupid because the sub has to be hooked up to present the ohm load your setting it up for. right?

and everything set at zero, not in the negatives. got it..
what about bass boost? just don't use it anymore to try and keep a cleaner signal? or set it ware i'll have it b4 i set the gain so it's already accounted for..?
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2205
Registered: Nov-07
disconnect the sub
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2206
Registered: Nov-07
IIRC you are doing 1500 at 2 ohms

so 1500x2=3000
sqrt of 3000= 54.77v
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2207
Registered: Nov-07
prior to setting the gains

make everything on the HU flat...except the sub control...turn the sub control all of the way up
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2208
Registered: Nov-07
then with the tone....turn your HU up to your normal listening level....once there - start turning up your gain until you reach the target voltage
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 213
Registered: Mar-10
ok, thanks for all the help man. im glad it's finally going to be somewhat right.

tyvm

buy the way, what are you running right now? get anything new?
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2210
Registered: Nov-07
youre welcome. nothing yet man

ive been wanting a few different subs. i just cant pull the trigger as most of my audio stuff is back in michigan still. all of the important stuff atleast.....alty, amp, batts

if i did buy - the sub would just sit here until who knows when. no sense in that.

im thinking i might do a tc sounds axis or an audiopulse axis next. not really sure yet. im going to start with a single 12 in a sealed box, firing into the cabin, on 2-3K RMS.

ive been eying this:

http://www.caraudioclassifieds.org/forum/showthread.php?t=33682
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 214
Registered: Mar-10
yeah that makes sense, but those subs look serious! even just having one 12 looks like it's guna pound.

witch ever way you decide to go make sure you post a build log for sure man. id'e like to see how it goes.
 

Silver Member
Username: Schinner

Post Number: 106
Registered: May-07
actually you should have the sub hooked up....the load will change the voltage...setting your gain without the sub hooked up (or some resistor of the same load) the voltage will measure fine but actually be higher than you want when you hook up the sub later
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2211
Registered: Nov-07
uhhhh no
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 218
Registered: Mar-10
well it finally stopped raining here so im guna go out and give this a try real quick.

but just for the record, is it with sub connected or no..?
i'll just do it disconnected and check for rise after i'm dun and have it hooked back up.
 

Gold Member
Username: Bonhamd

Traverse City, MI

Post Number: 2215
Registered: Nov-07
i just found something that explains it better and in more detail than i did

check out this caco sticky - you might have to become a member to see it....but good info for sure

http://www.caraudioclassifieds.org/forum/showthread.php?t=3106
 

Silver Member
Username: Sleste8

Shelbyville, MI United States

Post Number: 221
Registered: Mar-10
i was already a member, so that worked out. thanks for the link tho, that seems like great info.

i checked it before i started and by ear i had it at 59, but now i put it at 54.77 give or take (i couldn't get it exact) with a 50hz tone from fine custom works.

now i have to do the ssf.
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