I had my first subwoofer (alpine type r 12") in a ported box and amplifier (alpine mpr m500) installed in my TL today. Well I noticed there are three knobs on top of my amp for adjustment (The low pass filter, gain, and bass eq). I am curious how each one changes the sound/ what they do?

I am looking to achieve a tighter bass than what it's currently outputting.

Also, if any of you guys have this amp, what are your three knobs set at?

 

size of the box? what's it tuned to?

 

the dimensions of the box are 15"x15"x30" (HxWxL) it's not custom made either. I was playing around with the controls when I found the gain to have been set to full, I figured that couldn't be right so I put it at about 1/3 way. The LP is at about 75, and the bass boost is around 4-5. I am very new to car audio and just related gain to the gain of a electric guitar amp which makes the sound distorted at full. So any help would be great.

 

you can put the gain to about 3/4 on most amps

 

is gain like volume? Or how often the sub kicks in/sensitivity? I'm a bit confused what the low pass filter, gain, and bass eq do.

 

turn the bass boost off..and NEVER turn that gain past 1/2

it's not a volume knob

 

what about the LP filter? I just set it to lowest at 50 to play it safe for now.

 

The LP is the top cutoff point for the sub... Play around with that one. Some people like their subs to play higher, some don't. It's your call...

 

ooh, so that's somewhat of a sensitivity adjustment? Because I have everything except gain at 0 with the gain at 1/3 and it's much closer to the sound I was looking for, especially in rock and alternative music. Although for hip hop and rap, songs like BIA BIA by ludacris, there's hardly any bass compared to what it was before. Any reason why this is?

 

1. For LP, go between 20-30, but 50 is too high for a sub.

2. Gain adjustment: Set your headunit's bass to zero, not minus, but zero. Then, turn your headunit volume up to about as high as you'll ever turn it. Now, go to your gain on the amp, and turn the gain up as high as you can go before distortion occurs. (<-- This method is directly from Alpine).

3. Bass Eq: This is dependent on your personal preference.

 

Probably your HP filter. It's probably set too high for the rap music (generally into the 30hz range) whereas rock/alternative is generally in the 50hz range.

And no, LP is not sensitivity. Gain is sensitivity. LP and HP are cutoff points that tell the amp what signal to send to the speaker (sub in this case).

 

I couldn't edit in time, but it's your HP, not LP. Also, set your HP at the tuning of the box, not just any random number. If you set the HP lower than box tuning, you can bottom out the sub, and that's not a good thing...

 

Thank you, this was pretty helpful. But my LP starts at 50 so it can't be too high. I'm pretty sure it goes from 50-250 or something.

I never had my box tuned, I just went to my local audio store and asked which would be best for my alpine type r and this is the box they gave me. I may be misunderstanding something though. I can also go back to best buy where I had my amp installed and ask them to tune it for me which might be better.

 

More than likely you just voided any installation warranty you had with the shop that installed it. However their use of the bass boost and gain turned up all the way doesn't instill confidence in me about their installation abilities. princelybug provided a very good description on how to set the gain properly. Of course the source material used will be important as well.


The above are absolutely wrong. Sometimes the best setting for the gain is all the way up. Sometimes it is all the way down. And many times it is somewhere in between. It all depends on the gain structure of the amplifier and the output voltage of the head unit. The gain control is there to adjust for varying output voltages on head units to maximize undistorted power output. A higher voltage head unit will require a lower gain setting.

Setting the filter will be best done using your ears. This is because most amplifiers use pretty cheap potentiometers for the filter adjustments. They don't change linearly when turned so the markings are inacurate. You want your sub to blend with the front speakers. Most front speakers can't play down to 50 Hz with any authority, so you will want the sub to play higher than that. Unless we are installing some high quality speakers with a good midbass response, I generally set it around 80 Hz.

As for the bass EQ, use it at your own risk. Just know that if you do use it, your gain will have to be adjusted accordingly to keep the signal clean.

 

^ x2... Personally, I set my sub amp gains using Ohm's Law, a DMM, and a 40hz test tone. Turn the hu volume up to 75% of max (the is general, since some hu's put out clear signal above this, and some start to distort below this) and figure out what kind of output voltage I need to see on my amp. It's worked so far for me.

Your LP is too high. You need to turn it down lower towards the tuning of the box. The box tuning is determined by the physical dimensions of the box. Internal airspace and port volume (length and area) determine tuning. In order to find what your box is tuned to, you need to measure the port area (cross sectional) and the length of the port. It's probably an L port, so the length is different than what it may seem like it is. From there, we'll be able to help you with tuning...

 

Disregard what I said about the LP filter. I was thinking the SSF (sub-sonic filter). The SSF (if the amp has one) needs to be at the box tuning, whereas the LP should probably be up near 80hz or so, if you have factory speakers. If not, then you get to play with the settings. The LP depends on how low your mids will play. Mine play down into the 50's with no problems, but I have some pretty beefy mids... Most other speakers will not play as low as the ones I have (especially not 6.5's), but if your front speakers are factory, you should set the LP up near 80hz or so...

 

the gain is never suppose to be jacked up

 

What if your hu only has 2v outputs or something like that? To get the correct voltage out of your amp, you're going to have to crank the gains a little more. Now, if your running one of the old school rf hu's that have 8v pre-outs, your gain will be much lower. And you can turn the gain up until you get the amp to start clipping, then turn it back down a little bit. Again, you should use a test tone. The best way to set your gains is with an o-scope, but not everyone has one of those sitting in the garage.

 

good point

 

The port is 13 inches tall, 3 inches wide, and 16 inches deep.

I also moved the LP from 50 to 75 and barely noticed any difference.

 

What material is the box made of? Better, how thick is it? 3/4"? 1/2"? And I'm assuming all the dimensions you gave were external? If you could draw something in like paint or whatever showing a top down view of the box with all the dimensions, that'd be great...

 

want me to just take pictures? Also the size of the port was internal. I'm thinking it's anywhere from 3/4 to 1 inch thick.

 

just so you guys on the forum know as stated wrong before,

A High Pass Filter (HPF): Controls highs/mids and tells them not to go under a certain ferquency... *80-250 is a good setting depending on your needs

A low pass filter prevents your lows(Subwoofers) playing HIGHer than a certain frequency.. Usually don't wanan go higher than 80...

A SubSonic filter is to prevent damage to your subwoofer.. find out what frequency your subwoofer can play down to... Ussually around 25 n up depending on your subwoofer...

The Gain is suppost to be set equal to your head unit's volts.. Easiest way to explain is if you set it too high your subwoofer will become louder than your mids/highs if you set it too low it won't be loud enough..

If you have the right amount of watts to each subwoofer and have the gain set correct the bass boost should be at 0!!!!

Remember your amp is not the only place to mess with bass boost and filters!!! Check you Head Unit make sure the equalizers are set to zero and then you can adjust them as you feel necessary its YOUR system... Just dont blow the subs trying to put unesscesary bass boost...

Alright theres my rant if you have any questions pm me or email r wuteva yahhh....