I originally updated an old post, but decided I needed a new post.

Here is the background:

I installed a JL MHX280/4 and some Arc Moto 602 speakers in my 2017 Road Glide. I wasn't very happy with the volume, especially at 70+ MPH, I thought it should be louder.

Last night I took the fairing off and decided to tweak the gains on the amp, this is what I found:

I used a number of different 1Kkz test tones and the results were all over the place here is an example of two of them:

here are the two 1 Khz tones along with the MP3 Gain volume and DMM voltages:

https://www.stevemeadedesigns.com/bo...w-links-again/

MP3 gain volume = 98.1

26.0 volts with this one.

https://www.mtx.com/d/mtx/testtones/1kHz.mp3

MP3 Gain volume = 102.1

39.1 volts with this one.

What the???? I'm confused in which one to use. I can say using the first one above, at 70+ MPH leaves a bit to be desired from my system, I wouldn't be very happy with it!

 

MHX280/4
4-Channel Class D Full-Range Marine Amplifier, 70 W x 4 @ 2 Ω / 50 W x 4 @ 4 Ω - 14.4V

look at the Sticky "Setting Applifier Gain for Vac setting:
2 ohm speakers: ~ 11.5 - 11.8v
4 ohm speakers: ~ 14.1v
Moto 602's are 4 ohm

So not sure how you got the 26v and 39v dialed in with the amp you got but IMO there is no way you can get there.
Moto's need a way stronger Amp and to be honest 50W per channel is not going to cut it for 70+ Mph

the MP3 Db level only will impact the dial in, nothing else (with same gain setting the 102.x file will distort on a lower volume setting on the HU than the 98.x one.

Others will chime in here...

 

It's bridged.... therefor recommended output voltage when bridged is 23.7, but many people push that amp harder.

The JL MHX280/4 will easily push 150+ watts per channel when bridged.

 

ok - no experience with this amp but when (if possible) you ddm it to 39Vac with the MTX test tone, I am 100% sure there is something wrong with the mp3 or something else - that 350+W!!!
without having the amp on my bench I cannot tell you where the amp starts distorting (on the scope).

 

The lower the db your test tone without adjusting the input sensitivity, the less output from the amp, as less output voltage is produced from the source unit. So -5db test tone puts your amp gains up a bit higher to accommodate other music sources that produce a lower output such as satellite radio. Running mp3 gain for music at 93 imo tends to reduce the volume of the music a bit much. 96 db is a happy medium. Run a -5db tone, music at 96 and be done. You clipped that amp so bad had it had a load on it a fuse would have blown. Keep in mind set the test tone on your primary listening source. I never use cd on my bike so usb is my primary source. I use satellite radio so run a -5db tone. If you do not listen to other sources then run the 0db.

 

SlyeDog,

OK, with this test tone (the 1000 Hz -5 Db from your Sticky) http://www.mediafire.com/file/o7x85a...rta/1000Hz.zip I am running 26 volts.

I don't know why this test tone (1000 Hz -0 Db) https://www.mtx.com/d/mtx/testtones/1kHz.mp3 jumps up to 39.1 volts but it does.

To throw a little wrinkle into the mix, I called Biketronics, they now make two different BT 355 Line Levelers, they are sending me one for the Boom! 4.3 HU. Mike said that it will make a dramatic difference and that I will definitely be able to tell.

So as it stands, I'm waiting for the new BT 355 before doing anything else!

Slyedog, if i use the 1000 Hz -5 Db Test Tone from your sticky, I should be ok, right? Many people have told me 26 volts for the JL MHX280/4 is in the playing field (up from theie 23.7 recommendation).

More thoughts on this would be appreciated.

 

I cannot tell you outside of the rated output where to put that amp without it on my scope just like AAWAV said. The reason the 0db put out more I explained in my previous post. What goes in comes out. The more in the more out with input sensitivity in same position. I would think 26 is just fine but again without my scope I cannot say. Also music being dynamic you will still need to play it on the side of caution with your volume ****. Do not exceed 14 on your volume