View Full Version : Long shot, tuning help with amp...

06-01-2011, 08:45 AM
So just wanted to get some input, as I have never tuned an infinite baffle sub, nor am I really familiar with wetsound products. Though so far I love the way this amp sounds...

(1) WetSound Syn 6 "hybrid" amp
(4) 4 JL Audio m770 marine 7.7" speakers w/ 1" tweeters M770-CCS-CG-WH (100w rms)
(1) JL Audio 10" Marine subwoofer M10IB5-CG-WH (250w rms)

The Wetsound amp is considered hybrid because it has basically 2 power supplies. One which runs channel 1 - 4 and one which runs channels 5 - 6.

The rated specs on the amp in my current setup is:
60w rms x 4 @ 4 ohms (channels 1 - 4 for the JL m770 speakers)
600w x 1 @ 4 ohm (channels 5 - 6 bridged going to the subwoofer)

My issue is that i switch from a sony marine amp which put out something like 140w rms / 300w max to the sub, and this jump to 600 watts is not much louder. I mean don't get me wrong it sounds great, but not like I expected. It seems that I have to turn the gain almost 3/4 of the way up on the 5 /6 channel.

The sub is installed as an infinite baffle setup in the stock location for the boat, is this pretty typical with infinite baffle setups that a large increase in power really does not increase the output by that much due to the install?

Also, the sub is only rated for 250w, and the way the amp is setup now is suppose to out put 600w, so having the turn the gain up so much really doesn't seem to make sense to me, I would have expected the sub to distort at a much lower gain level.

Anyways, he is a picture of how I have my amp tuned to right now. For the gain knobs, the top dot is the lowest setting.


06-01-2011, 05:24 PM
I have an Arc Audio KS 900.6 running the factory JL infinite baffle sub off channels 5 and 6 and it's not that great either. I have a separate channel input from my Wet Sounds 420 EQ for the sub and when I turn everything down except the sub I get more of a rattle than a boom that I've gotten from the enclosed subs I've used in the past. May be the down fall of the infinite baffle vs an enclosed sub.

06-01-2011, 05:52 PM
Volume (SPL) increase isn't linear, it's logarithmic. You generally get about 3dB increase for every doubling of power and that's audible, but not a knock your socks off increase. Also, infinite baffle isn't the most efficient method of housing a speaker but it is convenient.

At a lower gain setting, the amp isn't going to clip. OTOH, the woofer could have problems if you overpower it by too much, especially if it doesn't have an enclosure to control its motion. Another thing going against being able to perceive large SPL increases is the fact that you're using this in a boat, which is open to the space around it and not a group of boundaries, the way a room is. The walls, floor and ceiling all reflect the sound and any sound that's reflected back to the listener adds to the perceived loudness. In a boat, the sound just leaves.

If you want to find out where the crossovers are working and how well the woofer is blending with the high pass, download Room EQ Wizard. Don't worry about the highest frequencies- laptop computer mics aren't good enough to do well over 10KHz but the rest of the frequency response will be good enough for this purpose. It's a free download but you will need to register at Home Theater Shack.