Am I going to damage my Sub using "gain" on Alpine MRD-M300?

[Soul4t]

Hi All!

This is my first post so appologies for any novice mistakes!

I have aquired the Alpine MRD-M300 mono amplifier with the Alpine SWR-1241d 12" from a friend who I'm certain won't have given it any abuse and would have had it set up for him, then probably didn't touch it.

The Sub is in a box, I pressume wired in parallel (it's a typre r dual coil, 2 x 4ohm coils) to two connectors on the side of the box, set up to connect to the amp which, when powering the sub in 2 ohms, should match the 300watts RMS rating of the Sub...spot on match?

I'm using a head unit that specifies that the "Preout max output" is 2.2v.

In the amp manual, it has instructions for Input level, on my amp it has this Input level (3 stages I think...-12, -6, or 0db) then another option (no trace of in manual), for Input gain (3 stages 0, +6, +12db). In the manual it says it has Input level (-18, -12, -6, 0db).

On a different forum someone posted that it's not technically a gain as it's a digital amp?

Anyway, the apparent setting for a 2v Preout from HU to amp, is -12db.

I currently set the amp at 0db Input level and 0db on gain but I want to up the gain as I have to turn the HU up too much (too much to components) to get any real kick at all.

After all that...my question is:

Will I damage either Sub or amp if I up the "gain" so long as I ensure the amp overload light doesn't come on?

I'd appreciate any help!

Thanks!

Click to read more...

 

[keep_hope_alive Premium Member]

yes, you can increase the gain since you won't operate the HU at a volume level that will produce enough signal to clip.

well written question, thank you for the details.

 

[Soul4t]

Hi!

Thanks for the quick response!

Great, I thought that might be the case, thanks for confirming for me.

Just out of interest, do you know if this would be much different if the amp wasn't able to support 300w RMS? I don't fully understand the reason, but I think I've heard that it somehow causes the coils to overheat/overwork?

Again, Thanks for any help!

 

[Soul4t]

Hi all!

Just an update, I've put a 60hz sine wave out the HU at vol. 44 (I think out of 50) and measured the RCA output volume by putting a multimeter on AC ("20" as opposed to "400"..screen shows -00.0), put the positive terminal to the middle pin on the RCA and the negative on the ring part of the RCA. The only thing that happened was the screen went from "-00.0" to "00.0". There is no finer sensitivity setting on the multimeter. I did put the meter on DC at it's lowest sensitivity some milivolts and it showed a .0025 signal or something, but I'm not sure if it's a test of anything really.

This appears to explain why I've been able to put the input level at highest setting and also the gain setting. I've played music through it with added parametric EQ, full volume and the Sub's moving a fair bit (it boasts 3" excursion potential) but I still can't get the "over" indication light to go on! I can't hear any aparent distortion or breakdown in sound quality. I also set the display to show the current that the amp is drawing, it stayed mainly around 1amp, but jumped up and down a bit, no more than 4amps. The amp sports 2 20amp fuses, so this seems ok for full drive certainly. Sufficeth to say I've taken these settings right down to more reasonable levels and would probably next to never drive it that hard.

So having not been able to even detect the RCA voltage, could this mean that either the HU is not putting out hardly any voltage...hence the amp high settings, or is something else going on?

Thanks for any thoughts!

 

[keep_hope_alive Premium Member]

giving a sub less power than it's rated for is fine. that is what happens at low volumes. your amp will rarely, if ever, produce 300W RMS even though it's rated for it. music is dynamic and it takes a very specific set of circumstances for the amp to make rated power.

some people will say that "underpowering a sub can damage it" but it's not a true statement. what they are trying to say is that having an amp that is smaller than your expectations of the amp, can cause you to set gains so that you encounter frequency clipping. but the clipping still needs to be of sufficient power that the coils overheat.

higher power than rated kills subs. you can increase RMS power by clipping.

having an amp that is larger than you NEED allows you to avoid clipping altogether. but you destroy a speaker thermally or mechanically from too much power (clipped or not)

 

[Soul4t]

Hi,

Thanks for the info, makes perfect sense! Do you know what clipping sounds like in a sub? I imagine it's typically very difficult to hear!

Thank you.