AMP Settings? Help

Forbidden · 26 Oct 2006 at 17:07

The amp is a JBL GTO75.2 and I have 1 sub.

Ok, thanks got my amp and sub working. Just need to find what settings to do it in?

I'm running one sub, and it says you can connect 2 subs so it has.

Left +
Left -
Right +
Right -

Terminals, which on do I connect it to?
Left + and Right -
or
Left + and Left -

Also on the mode settings what should it be LP, HP Flat (I think thats the 3)

FreQ 32hz or 320hz

Like playing bass

mc_bob · 26 Oct 2006 at 17:09

If you open up the manual it tells you everything.

You want to run the subwoofer off bridged mode. So the positive lead goes on the very left of the four connections, and the negative lead goes on the very right.

You want Low pass filter so select LP.

Tdh1987 · 26 Oct 2006 at 17:17

I wouldn't run one sub off that amp, never mind two. Make sure your one sub is bridged.

mc_bob · 26 Oct 2006 at 17:20

Tdh1987 said:
I wouldn't run one sub off that amp, never mind two. Make sure your one sub is bridged.

Why not?
I'm using that amp with one sub.

You want your Frequency so it cuts out voices etc. You gotta select your frequency, input voltage and gain yourself.

Tdh1987 · 26 Oct 2006 at 17:23

Because its not really capable of powering a sub.

Set it on a Low pass filter (LP) and the gain as low as possbile, not to low that you can't hear it.

Forbidden · 26 Oct 2006 at 17:30

Whats the gain? :S

mc_bob · 26 Oct 2006 at 17:35

Tdh1987 said:
Because its not really capable of powering a sub.

Set it on a Low pass filter (LP) and the gain as low as possbile, not to low that you can't hear it.

It gives out 294W RMS (I think...) so it's capable of powering a single subwoofer easily.

And the Gain is marked as Bass Boost.

Tdh1987 · 26 Oct 2006 at 17:48

mc_bob said:
And the Gain is marked as Bass Boost.

It shouldn't be, check again.

It'll sound alright, but it'll be miles off a Vibe slick A7 or MonoBox 3.

Firestar_3x · 26 Oct 2006 at 17:56

Tdh1987 said:
I wouldn't run one sub off that amp,

What a load of gash, bridged thats easy enough powerful enough for a sub, i used to run mine through a Vibe Black Box 1 Bridged gave about 150watt rms and that sounded great.

monkeyspank · 26 Oct 2006 at 18:04

Bass boost and gain are 2 different things on that amp. Gain is labelled as input level. you need to match this to your headunit. Read up about clipping. Set bass boost to 0.

crossover is labelled frequency IIRC, and depending on what other speakers you have you will want it about 80 as a very general guide. The problem is that there aren't any markings on that amp so you have to do it by ear.

mc_bob · 26 Oct 2006 at 19:10

monkeyspank said:
Bass boost and gain are 2 different things on that amp. Gain is labelled as input level. you need to match this to your headunit. Read up about clipping. Set bass boost to 0.

crossover is labelled frequency IIRC, and depending on what other speakers you have you will want it about 80 as a very general guide. The problem is that there aren't any markings on that amp so you have to do it by ear.

Oooh my bad. Yeah I'm always twiddling them about...

Tesla · 26 Oct 2006 at 19:42

monkeyspank said:
The problem is that there aren't any markings on that amp so you have to do it by ear.

I used a 80hz test tone MP3 when setting mine up, then slightly changed it when i stuck on some vocal stuff.

The amp is perfectly adequate to power a sub, just under 300W RMS.

FireBIade · 26 Oct 2006 at 20:32

Years ago after a bit of tweaking I came to the conclusion that, to get a good setup I would do the following

Headunit setup:
Reduce most if not all bass gain from the main speakers by setting a -db figure. But keep/leave loudness control on (this is personal preference etc).

Amp setup: (obviously bridged, on-board LowPass filters generally aren't as good as having a seperate coil)

Wire using the fatest earth cable you can fit on the power terminals, and make sure it is as short as possible and makes a good connection to the car body.

Make sure bass boost is all the way down/off.

Adjust the volume/gain of the amp so that it matches the music at desired levels and doesn't clip, then reduce it a bit.

Finally tweak up bass boost to add more rumble to the punch at desired levels. Not too high etc!

Had 2x10" Kenwood subs running quite nicely & it went chuffin loud with all the bass removed from the main speakers.

Tdh1987 · 27 Oct 2006 at 17:13

Firestar_3x said:
and that sounded great.

I bet it did

Try running a sub off a decent amp and you won't believe the difference.

needmorespeed · 27 Oct 2006 at 17:23

best way to set up an amp is to turn all bass boosts off they just muddy the bass and make it sound rubbish. set all eq's to flat(these can be adjusted later) turn all gains to minimum and turn the headunit up until you get to 2/3rds to 3/4 of max volume. EG if you maximum volume is 60 go to 45 maybe 50 but no more and then start turning the gain up until you hear distortion and then back it down a touch Dont go over the 3/4 volume as that is now your max volume going over that could damage the speakers. For subs the crossover should be set to LP(low pass) and the frequency should be between 80-120Hz don't go over 120Hz as bass starts to be come diretional the high up you go

mc_bob · 27 Oct 2006 at 17:41

Thanks to FireBIade and needmorespeed. I just re-set up my Amp and it sounds a bit better

Reckon a power cap is in order now

Tdh1987 said:
I bet it did Try running a sub off a decent amp and you won't believe the difference.

Elaborate how a 75.2 is no good at powering a single subwoofer please.

FeFiDoh · 27 Oct 2006 at 17:50

Sorry to hijack this thread but it was quite useful in a way...

I have 2x10" vibes powered off a black air amp its pretty powerful more than enuff to do these two subs (says 1400w rms cant remember the real W per channel tho).

I tried to follow that advice but my amps different and has bass boost and line in along with Hi-Pass Flat Low-Pass settings and gains for each. I dunno what any of them should be set to? At the minute its on flat and the gains are in the middle with bass boost and line input between 1/2 and 3/4s.

My CD player also has settings for the bass, at the minute its -8 for that but it has Bass F with it going from 100hz down to about 60 or something. Im lost when it comes to all this stuff tbh

mc_bob · 27 Oct 2006 at 17:55

Ok lol.
Ill give it a go.

You want your headunit to be giving little bass to your main speakers. So adjust your bass on the headunit so your main speakers are mostly Mid-Highs.

You want all the equalizer and stuff to be on standard settings, or lower

I put the loud setting onto low just to boost some of the lower sounds.

Move over to your subwoofer amp when your happy and start tweaking the settings. To start off with.
Set your bass boost and level input to minimum.
As your using subwoofers, you want it to be on lowpass (LP) for definate.

Turn up your headunit to about 80% of its maximum sound. Go to your sub amp and start raising the level input till it starts to distort, when you hear it distorting, turn the it slightly lower or you'll eventually just burn the sub out.

Now fiddle with the Bass boost till you get the effect which you want.

Please correct me if I said something wrong lol, I'm kinda new to the subwoofer game.

FeFiDoh · 27 Oct 2006 at 18:02

sounds like everything from thread bundled into 1 msg there thanq bob i shall give it a go in a minute

headunit has amp settings tho have flat or low, so i guess set that to low also?

Luke · 27 Oct 2006 at 18:04

mc_bob said:
Reckon a power cap is in order now

For a relatively low powered amp and sub? Don't bother, it won't do any good whatsoever (unless you are doing it for looks).