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Memo 02-11-2014 01:38 PM

Fusion MS-RA205-JL M400/4 help
Has anyone connected a JL M400/4 amp to a Fusion MS-RA205 head units speaker output? Do I need a line output converter or can I splice an RCA jack to the speaker out and connect to the amp? Fusion MS-RA205 has 2 zones with 4 speaker outputs and one RCA out for amp. I am using RCA out to connect one JL M400/4 Amp to drive tower speakers. That leaves me with (4 x 50W) speaker outputs for the in boat speakers. My plan was to connect a JL M400/4 amp to speaker output. According to JL manual The M400/4s input sections are designed to accept signal voltages from 100mV 4V. This will accommodate all preamp level signals and many speaker level signals. I know in some cases line output converter is needed to step it down before Amp input. Looking for info before I blowup something.:D

David Analog 02-11-2014 03:41 PM

The JL Audio XD400/4 (same as the M400/4) manual clearly states, as does the video, that no external adapter is required to run a high level BTL HU output into the amplifier. In that case you should avoid using an external and redundant step down device. I do not see a problem.
However, let's look for an exception just to be safe. Wire everything up according to the manual. Easy does it to begin with. If you experience alternator, ignition noise or switching transients of any type, a foreign noise, pop or distortion, as you elevate the volume level, or the input sensitivity control on the amplifier is not responsive enough, then disconnect everything and turn to an external device.

Memo 02-11-2014 06:30 PM

Thanks for the advice will M400/4 drive 4 in cabin JL 7.7s ok?

David Analog 02-11-2014 07:53 PM


Originally Posted by Memo (Post 1013466)
Thanks for the advice will M400/4 drive 4 in cabin JL 7.7s ok?

Yes it will....but just okay. Give it a C+.
The JL Audio M400/4 power is under-rated and will actually meet its 14.4V supply rating with a 12.6V supply. That's rare. So you can count on 4 X 75 watts into a 4-ohm load under most any conditions.
However, the M series 7.7s will handle twice that much power and really come alive with more power. The midbass attack and dynamics with 150W per speaker is a jaw dropper.
I think the M400/4 on four 7.7s is perfectly balanced with 200 to 300 watts going to a single 10-inch sub. But when you start building in bigger and more powerful subs you need to fortify the in-boat satellites in order to have balance. Besides more power, the most productive thing you can do is to add a third pair of 7.7s so that you have two pair in the cockpit. That extra surface area and extra 2 X 75 watts makes a huge difference, especially in how the coaxials mesh with the sub. The moment the sub bass overdrives the mid bass you have muddy, boomy bass.

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