Help with audio install!

I recently installed 6 JBL 6.5" speakers in my 21' Sea Pro Center Console. 4 of which were running off the Sony CDX-HS70MW head unit. The other 2 are running off a Sony XM-604M amp. This amp is set up to be either 4 or 3 channel. I bought this amp so I could run the 2 speakers on 2 of the channels and then bridge the other 2 channels for a sub install. This is what this amp is intended for. I am now finally getting around to installing a JL M10iB5-4 10" free air sub on the side of the center console about a foot above the deck of the boat. The problem is this expensive JL sub does not sound loud at all. My 6.5"s are putting out as much bass. The amp is rated at 140 watts RMS at 4 ohms. I would think this would be enough power to at least make the sub sound decent.

Should I install a box around this free air sub? Does the amp just suck? Any help would be great.

Re: Help with audio install!

If it isn't in a box it will not sound near as loud. Install the sub in a box. Also, be sure that your wiring is correct. Most JL subs are dual voice coil. If the amp can handle a 2 ohm load on the bridged channels, then bridge it and wire it for a 2 ohm load. I'm guessing it is only stable to 4 ohms as most sony amps are.

Re: Help with audio install!

Its a single voice coil 4 ohm. Amp is only stable at 4. I've checked the wiring and its good. It sounds like it just doesn't have enought power or it needs an enclosure, but I thought with these infinite baffle woofers all you needed was any kind of enclosed area. (such as the center console when the door is shut) I've never had one of these infinite baffle woofers so i'm not very familiar with them.

Re: Help with audio install!

Just a thought......
Have you any 1.0 mfd cap's on the power supply side of amp?
Your amp might not be getting enough umppff to do it's job.

Re: Help with audio install!

From Crutchfield.com.
A "free-air system" consists of woofers mounted to a board attached to the rear deck or placed in the trunk against the rear seat. The trunk of the car acts as an enclosure which houses the subwoofer and isolates sound from the back of the speaker, solving the sound cancellation problem of subs without an enclosure.

Free-air systems save space and have flat frequency response. The woofer must be specifically designed for free-air use. The lack of a box makes them more convenient to install, but their power handling levels are usually much lower than their boxed counterparts


Question: How much opening do you have in your CC. Is it completely enclosed? You could try placing some standard household fiberglass (paperbacked type) behind the subs to see if you get more sound from them. just cover & tape them temorarily) If you hear a noticeable difference then I would assume an enclosure would help. Search some of the audio forums regarding free air subs and see if a solution exists. Or, call JL and describe your dilema in detail.

By the way, most manufacturer ratings are not too accurate in the sense you would think or consider. An RMS rating of 150W on your amp is not necessarily 150W @ say half volume. The Sony spec dosent really give 150W at a level which could mean at full power (turned all the way up) Your amp may not be powerful enough to give you the sound you had hoped for when powering these subs. Try bridging the channels and running them to the sub. Perhaps then you will see what power would be expected to properly supply the subs with enough power.

Re: Help with audio install!

No cap. I have 2 batteries. If the boat is on/off or even with the battery switch on both batteries it doesn't sound any different. The power/protector light indicator on the amp never lights up so it's getting at least 10.5 volts all the time. The amp has 8-gauge terminals but I'm only running 10-gauge. I don't think this would have anything to do with it because it is still getting at least 10.5 volts

Re: Help with audio install!

Not sure of the exact cubic feet of the center console but i'm guesing between 15 and 20 cubic feet. No openings in the center console.

Re: Help with audio install!

I would try temporrarily bridging. You'll likely be suprised.

Hows the return policy on the sony?

Re: Help with audio install!

Are you using RCA's or speaker outputs for the amp input? Did you connect the sub bridged as in the positive goes on the first screw (left side) and the negative goes on the 3rd screw. Have you adjusted the level control for that side?

Re: Help with audio install!

That should be enough to drive your sub. I run two of the same amps and they sound great. Double check your level controls, it may be that they are turned way down.

Re: Help with audio install!

Free Air and infinite baffle subs get a bad rap because they normally aren't installed right or they are assumed that they don't need an enclosure. What you're probably experiencing is cancellation. This occurs when the sound waves coming from the rear of the speaker interfere with the ones coming from the front of the speaker.

Car audio was the worst for this because people would install them in the back deck or on a board in the trunk without sealing off the trunk area the result was mediocre output similar to what you are describing. Installing free-air subs in a seat bottom that will allow the sound waves to cancel each other out flat out won't sound good. You don't have to build a box of a specific size but you do need to keep the sound waves from interacting with each other.

The cubic volume doesn't really matter in a free-air setup as free-air subs are built with much tighter suspension than a non free-air sub, if anything it will require more power to drive it than a non free-air version.. If your center console is plastic or thin fiberglass you might consider reinforcing it because the sub could very well be causing the console to resonate.

Lastly, turn your gains back to 3/4 and no more if you need more than 3/4 gain IMO you need a bigger amplifier. Double check that the cross over on that channel isn't set wrong and is blocking the bass from coming out of it.



Your 6" speakers should be connected to the channel marked FRONT, and your sub to the rear outputs. The switch labeled HPF should be ON to prevent your 6" speakers from trying to pump lots of low bass, and the LPF should also be on to keep the sub from trying to produce high frequencies.

Looking at this amplifier it doesn't have an adjustable crossover its either on or off at 80 hz, try it in the off position, It also doesn't appear that the head unit has a dedicated subwoofer RCA Preout, double check your fade control and make sure it isn't faded to the front turning the volume on the sub way down.