Hey all. For those of you using JL Audio amps, I have a question for you. Have you used the JL method for input sensitivity? For those who don't know, here's the procedure:
- Get reference-level (not attenuated) test tones. 1000Hz for mains, 50Hz for sub
- disconnect speakers!
- Set HU to 3/4 full volume
- Set Sub level (if separate) to 3/4 full volume
Then run the test tones and use an AC voltmeter to check the voltage. Set the voltage based on a chart from the JL manual.
I set the gains up initially using this method, figuring I'd do the final tuning from the HU. In my case, I have a JL 450/4 running the whole system. 75w/2 running the fronts (Alpine Type R components) and 150/2 -> 300w bridged running the sub (an AW100T in a modifry V1 passenger side enclosure). Head unit is an alpine 9855.
So here's the deal - the sub was WAY too quiet. I couldn't even tell it's on when the top is down at highway speeds.
What I did to fix it:
- Backed the front channel gain down to make the sub relatively louder
- Increased the JL gain about 7 volts higher than the chart indicated for a 4 ohm load (I set it for that of a 6ohm load)
Now it thumps like it should, but I'm weary of exceeding JL's specs.
Anyway - anyone else sign off on this method? Is their manual a bit on the conservative side to cover their *****? I'm hoping that's the case! I dont notice any audible distortion (hard to tell w/ a sub), even at 32/35 volume.
- Get reference-level (not attenuated) test tones. 1000Hz for mains, 50Hz for sub
- disconnect speakers!
- Set HU to 3/4 full volume
- Set Sub level (if separate) to 3/4 full volume
Then run the test tones and use an AC voltmeter to check the voltage. Set the voltage based on a chart from the JL manual.
I set the gains up initially using this method, figuring I'd do the final tuning from the HU. In my case, I have a JL 450/4 running the whole system. 75w/2 running the fronts (Alpine Type R components) and 150/2 -> 300w bridged running the sub (an AW100T in a modifry V1 passenger side enclosure). Head unit is an alpine 9855.
So here's the deal - the sub was WAY too quiet. I couldn't even tell it's on when the top is down at highway speeds.
What I did to fix it:
- Backed the front channel gain down to make the sub relatively louder
- Increased the JL gain about 7 volts higher than the chart indicated for a 4 ohm load (I set it for that of a 6ohm load)
Now it thumps like it should, but I'm weary of exceeding JL's specs.
Anyway - anyone else sign off on this method? Is their manual a bit on the conservative side to cover their *****? I'm hoping that's the case! I dont notice any audible distortion (hard to tell w/ a sub), even at 32/35 volume.
The instruction from JL set the gains so that the amp will rarely be driven to clipping. In my opinion, that's the proper way to set them but that's rarely satisfactory for those who require heavy bass. Running the gains higher will stress the amp more but it should handle it fine. Most amplifiers are able to handle heavy clipping into the lowest rated speaker load (they have to be able to do so because that's how they are run by the majority of users). Of course, running an amp that way for extended periods of time will reduce the service life of the amp (depending on build quality).
I'm not a big fan of that method, but whatever you use you're still going to run into that "lack of bass" problem you have now. Believe it or not, the sub might actually be at the level it's supposed to be at, this is just so far below what you're used to that it sounds like it's silent. Either way, you can honestly set the gain wherever you want, but if you want to make sure you're being safe, simply run through this procedure again, but only to check at what volume the amp does hit full output. So if you set the gain where you think it sounds good, then you do this check again and find that instead of getting their specified voltage with the volume at 25, you get it at 22, that's fine, just try not to pass 22 on the volume control (even lower if you have any kinds of boosts in the EQ)
Also, the 9855 preouts won't clip until you get to ~33/35, so set your gains at that level if you want to maximise output voltage and reduce noise.
If you want to try another gain setting method:
http://www.resnet.trinity.edu/areynol1/gain.htm
Just be aware that any of those should yield results similar to what you found already.
Also, the 9855 preouts won't clip until you get to ~33/35, so set your gains at that level if you want to maximise output voltage and reduce noise.
If you want to try another gain setting method:
http://www.resnet.trinity.edu/areynol1/gain.htm
Just be aware that any of those should yield results similar to what you found already.
Thanks for the advice everyone. I think I'll leave the gain where it's at and try my luck. I calibrated with the voume set to 25, and most of my listening turns out to be between 22 and 27, so everything is reasonably close. I guess I'm driving the sub portion of the amp a little hard, but my only alternative is to sell this amp and go bigger - which I can't really afford to do at the moment.
Thanks again.
Thanks again.
Power=voltage squared divided by resistance ie: 25w into 4ohms = 10v. Jl Audio's method is very sound. You want to achieve the RMS wattage at the point just before the source clips. A good amp will usually put out a little more but nothing wrong with headroom. Not loud enough? More power. I personally like to acheive my maximum volume at about 2/3 of amps rated RMS output. Amp stays cool, distortion kept at minimum and there's lots of room to make it hurt when the need arrises.
- Status
- Not open for further replies.