But a monoblock amp only has one channel, right?

Isn’t’ that what mono means?

– Well – yes.

Then why does my mono amp have 4 speaker terminals? Is it a 2 channel amp or mono?!?

I get this question quite a bit. And for good reason…

It can be confusing when you go to hook up your subs to your mono amp and notice there are 4 speaker terminals. It looks something like this:

Don’t worry. It is in fact just one channel.

When you see an amp like this, both of the positive speaker terminals are wired together internally. And both of the negative speaker terminals are wired together internally (wired in parallel).

Amp manufacturers just do this to make it easier to connect multiple subs to one amp.

How do you connect subs to an amp like this?

Say you have two single voice coil 4 ohm subs and connect one to each pair of speaker terminals on the amp.

The final load the amp sees is 2 ohms because two 4 ohm SVC subs wired in parallel is 2 ohms.

What if you have just one sub?

Just use either of the two positive terminals for positive. And any of the negative terminals for negative. The remaining two will just have nothing hooked up.

This diagram does a great job showing a few different ways to wire subs to an amp like this:

But don’t take my word for it. MTX has a great description on their website:

” A monoblock amplifier is a 1 channel amp (mono literally means 1).

Since bass is omnidirectional, meaning you can tell where it’s coming from, it isn’t necessary to run subwoofers in stereo.

You may see 2 sets of speaker terminals on monoblock amps and they will be labeled as either speaker 1 and speaker 2 terminals, or simply + + and – -. That is because the two + terminals are connected to each other inside the amp, as are the two – terminals.

The second set is there simply to make it easier to connect multiple speakers to the amplifier.

Do not confuse the two sets of terminals as separate channels.

If you’re not sure whether an amp is a mono or two channel amp, you can look at the labels above the speaker terminals. A multichannel amplifier will have the separate channels labeled as Left and Right, or L and R.”

That should clear it up for everyone, but…

If you still have any questions on this (or anything else for that matter), just comment below or send an email to taylor@caraudioadvice.com.

I’ll do what I can to help.

And if you want great info like this sent directly to your inbox, sign up for the Car Audio Advice email list.

Here is another post that deviates a bit from car audio but may still be helpful to a lot of people. This will go over how to install a dual oil catch can setup for my 2007 STI that doesn’t break the bank as much as the higher quality custom kits from name brand manufacturers. This is not meant to take away from those companies’ sales. In fact I used to sell Mishimoto, Boomba Racing, Cusco, Beatrush, and ProSport catch cans. These kits are much higher quality, have the proper R&D behind them, and shouldn’t be completely overlooked when considering a catch can or air oil system. I am offering a cheaper alternative geared more towards DIYers that like to build things from scratch and source their own materials.

Why to use an oil catch can

First thing you should know is why a catch can is beneficial. The way the stock system is setup, air is pulled from the engine crankcase and valve covers using vacuum from the intake tract. The problem with this is that this air contains oil vapors which often condense somewhere in the intake. This is worse on turbo cars or cars that are more susceptible to blow-by which will pressurize the crankcase and push more oil out into your intake. This oil in your intake air will obviously mix with the combustion gasses and lower your effective octane rating which can lead to knock on certain engines. The oil can also pool up in the intake tract and cause air flow problems, especially on forced induction cars since pressurized air won’t hold liquid as well.

The catch can intercepts the path of this air back to the intake and condenses the oil in the can. The reason I chose the cans i did is because they have a baffle and a filter media in them to help with condensing the oil back to a liquid. Some people also put other filter media in the cans to help with this.

These pictures show what happens without catch cans.

One thing I realized while doing this was that figuring out a clean looking mounting solution was difficult. This part alone may make it worth a high quality custom fit kit. The catch cans come with a couple of self tapping screws which are probably fine for mounting, but I decided to go with a more robust solution.

Below is a diagram and parts list along with links to all of the parts I used for my kit. My total cost at the time of purchase was around $130. Price will fluctuate depending on when you’re reading this.

Click Image below for high resolution copy.

The guinea pig

How to install an oil catch can

For mounting location, I used the normal area on these cars which is the passenger side strut tower after removing the engine harness bracket. I found an old bracket from an Escort 9500ci install that worked pretty well and mounted it to the strut tower with these nutserts, these screws, and these washers (check out this awesome DIY nutsert tool. The one I put together is a variation of this. Works great). I also gave it a quick spray of undercoating to help prevent rust, but I was too lazy to jack the car up to spray the other side. Maybe next time I take that wheel off.

I used the install instructions from both Mishimoto and Radium to base my install on, but to make it easier, I just vacuum capped the little white plug that runs from the back of the PCV valve tee fitting to the turbo inlet and used the factory metal valve breather tubing that’s mounted to the intercooler.

To get the 1/2″ hose to fit on the turbo inlet, I used a heat gun and the end of a ratchet wrench to expand it. Didn’t use a hose clamp on this fitting since I put it on with the hose still warm, so it shrunk in place.

These cans come with fittings made for 1/2″ hose, so I needed two 3/8″ hose barb fittings. That’s where the brass ones came from. For my setup, I needed one 2 port and one 3 port catch can, but I liked the blue which was only available in 3 port. I used the plug that came on the bottom of one can to plug the extra inlet port for the PCV can since I put valves on the bottom of the cans to drain them. I used some thread sealant to seal the fittings on the cans.

Scroll through the pictures below to see what I’m talking about.

Oh and if you want a sweet LED hood light kit, let me know: CAAInstallations@gmail.com. It works great. I had to finish up after dark and could see most of what I needed with just that one light.

Update:

After I had this installed on the car for a bit, I would recommend upgrading to higher quality drain valves. One of mine had a very slow leak to it, but other than that, this kit worked out great. I’m not sure how it’s holding up now because I sold the car a few months after installing this.

This mini series shows how to upgrade speakers in a 2007 STi, or any 2002-2007 Subaru Impreza model. I will be showing how to remove door panels and speakers, make speaker adapters, seal doors and apply sound deadening, and how to install a set of 2 way component speakers with passive crossovers.

The second part of this video series goes over making custom speaker adapters:

Check out Part 1: How to Remove Door Panels and Speakers here

This mini series shows how to upgrade speakers in a 2007 STi, or any 2002-2007 Subaru Impreza model. I will be showing how to remove door panels and speakers, make speaker adapters, seal doors and apply sound deadening, and how to install a set of 2 way component speakers with passive crossovers.

Equipment used in this install is listed below. I am an authorized dealer for all these products. If you are interested, just contact me or order through the affiliate links below:

• Source unit: Sony RM-X7BT Bluetooth controller

• Amplifier: Zapco ST-4X SQ 4 channel amp

• Speakers: Sony XSGS1621C GS Series 6.5″ 2 way component speakers
• Sound deadening: SoundSkins Pro. Also check out Second Skin here.

The first part of this video series goes over door panel and speaker removal:

Check out Part 2: How To Make Speaker Adapters here 

Grounding kits have been proven to provide several benefits including:

• Freeing up horsepower and torque
• Increased gas mileage
• Improved throttle response
• Quicker starts
• Reduced audio noise
• Smoother idle
• Smoother power after shifts

This is a true 8 gauge OFC grounding kit with each wire cut to a custom length based off of a 2007 STi but should fit any EJ engine in a GD chassis or similar and most likely even more Subaru or other vehicles including Forester and Legacy. Please contact for fitment on vehicles not listed.

Features

• Wire: True 8 AWG OFC full copper marine grade wire for  maximum conductivity and corrosion resistance. Has similar conductivity to 4 gauge CCA wire with better corrosion resistance
• Ring terminals: Full copper ring terminals with better conductivity and corrosion resistance than gold plated terminals
• 3M heat shrink on each connection
• Includes everything needed for installation:
  • 5 custom cut lengths of wire for a chain connection that is proven to provide better performance than high cost “circle” grounding kits that connect major engine components all across the engine bay
  • Full color detailed installation instructions
  • Bolt for securing wire to passenger side intake manifold if your car does not have one
  • Nut for securing wire on back of alternator. Easiest alternator mounting of any kit
  • Zip ties to secure wires out of the way

Instructions

1. Start with wire 1 (long) that runs from the passenger side strut tower to the passenger side intake manifold.

Scrape off paint behind wiring harness bracket then secure ring terminal between the bracket and strut tower.

Run other end of wire 1 to passenger side intake manifold.

2. Secure the other end of wire 1 and one end of wire 2 (short) to the passenger side intake manifold. Use the supplied bolt if your car does not have one in this spot.

Run other end of wire 2 to the throttle body.

3. Remove upper throttle body bolt and connect other end of wire 2 and one end of wire 3 (short) to this bolt.

Run other end of wire 3 to driver’s side intake manifold.

4. Connect other end of wire 3, one end of wire 4 (short), and one end of wire 5 (long) to driver side intake manifold.

5.  Connect other end of wire 4 to the back of the alternator using the supplied nut if your alternator bolt is long enough. If not, loosen the easiest to get to alternator bolt, cut center part of ring terminal off, slide terminal in between bolt and alternator, and re-tighten bolt.

6. Connect other end of wire 5 to the negative battery terminal.

7.  Secure wires using the included zip ties and make sure all bolts are tightened up.

Finished Product

About us:

CAA Mobile Installations is a mobile car stereo business from Southeast Louisiana that knows all about 12 volt mobile electronics and how to improve on them. This exact kit was tested on the owner’s 2007 STi and immediate throttle response and improve idle was noticed. Only the highest quality materials were used in this kit.

Shipping cost included in price. Shipped in a USPS flat rate box to US only. Item will be shipped once payment is received via PayPal

I’ve done this on several cars successfully including a couple of Toyota Tundras and Chevy trucks. Here is how I did it on my wife’s Subaru Forester XT:

First thing you’ll need to do is cut off an end of an RCA cable with enough slack to run up to the camera connector. Strip back the insulation and separate the signal and shield wires. I forgot to take a picture of this, so I stole this one. I would recommend using a high quality RCA cable for this as cheap ones usually fall apart when you strip the insulation back.

On my 2015 XT, these are the wires you’ll need to tap into. The shield is the translucent blue wire, and the signal is the black wire. This is the 8 pin connector on the back of the multi function display.

Make secure connections then plug the RCA into the backup camera input on your new radio.

You’ll also need to run a separate wire to tell the radio when you’re in reverse. On my car, it’s on the driver kick panel. Brown/yellow wire. Just splice into that and run it up to the reverse wire on the radio harness.

There you have it. Backup camera image mirrored onto the radio screen.

Also, the iDatalink Maestro is awesome and gives you gauges and steering wheel controls in one on select cars and radios.

Finished product

There are many different ways to get cheap lightweight sound in your car. Of course the easiest and lightest is just listening to music on your phone from its speaker or a set of earbuds, but phone speakers suck and earbuds aren’t safe while driving. So here I will cover a few different options you have to get some decent sound in your track car.

First thing’s first. Get rid of your radio and any other sound related stuff like any amplifiers, subwoofers, etc. This is still a race car.

Speakers

Coax speakers are going to be lighter than components in this case, so I would recommend sticking with those. If you don’t know the difference, check out my Basics to Upgrading Your System post.

Factory Speakers

One option for speakers, and often one of the lightest depending on your vehicle, is just keeping the stock speakers installed. Many factory speakers use tiny magnets and have plastic baskets and paper cones. Speakers made like this are usually the lightest but won’t sound too great. But who cares? It’s a race car!

Some factory speakers (cough cough Chevy) are terribly and barely handle radio power, so hooking an amp to them will probably blow them pretty quick. Get prepared to upgrade at some point if you go this route.

Upgraded Speakers

If you want better sound quality than stock speakers even though it’s a track car, find a decent set of coax speakers like these 6.5″ Polk db651 (check price on Amazon). They are some of the best sounding coaxial speakers I have heard for the price. Amazon has the weight listed as 5 pounds. I’m guessing this is shipping weight, so just the speakers should be even less. Or you can get the shallow mount version and save a few dollars and half a pound: Polk db651s slim mount (check price on Amazon).

Some of the lightest 6.5″ speakers I found were these Infinity Reference 6032si shallow mount 6.5″ coax speakers (check price on Amazon). Amazon has them listed at 1 pound. I’m guessing that’s not the total shipping weight like the Polks.

To save even more weight, go with a smaller speaker like a 5.25″.

Most of the weight of a speaker will come from the magnet, so the smaller the magnet, the lighter the speaker generally. But this usually means a less powerful speaker unless you find with a neodymium magnet like the Lanzar VX60S VX (check price on Amazon). Speakers aren’t going to add much weight, though. Maybe 5 pounds at the absolute most.  

Amplifier

This is where most of the weight savings will come in. I don’t recommend you use a big traditional style amplifier like the JL Audio JX360/2. Many companies are starting to make very small, lightweight amplifiers. Check out the mini amp section of Sonic Electronix. As you can see there are many different amps to fit any budget.

My Recommendations

Alpine Power Pack: There are many other amps similar to this one, but this is the only one I have experience with and have nothing but great things to say about it. Great size. Great sound. Great power output. It’s even bridgeable which means instead of using 2 of its single channels to get 45W, you can bridge it to 2 channels and get 90W per channel. It’s also very lightweight. Amazon has it listed at just 2.4 pounds. But that’s not it; this amp is very easy to unplug and take out of the car. So you could very easily just mount it with velcro or something similar, and when you get to the track disconnect it and take it out to save even more weight.

Make sure you get the Alpine KTP-445U model and NOT the Alpine KTP-445A as the “U” stands for Universal and the “A” stands for Alpine. The “A” model is meant to be plug-and-play to an Alpine head unit and won’t come with RCA inputs which is important as you will see later.

This amp has individual left and right channel gain settings as well as a selectable high pass filter.

Lepai LP-2020A+: This little amp isn’t necessarily made for car audio, but it will definitely work and is very light. I have one of these powering a set of speakers in my apartment and it’s a good little amp. Using it in a car, I would make sure it was mounted securely and you will be fine. It’s not quite as powerful as many of the other choices out there at only 20W per channel, but it was also only $20 on Amazon at the time of writing this (click here to check most recent price).

Just make sure to get the right center positive pigtail to wire it into a car like this one, or you might be able to get away with cutting of the AC power supply and using the other end as a pigtail to hook up power and ground.

2021 Update:
Now that bluetooth amps are so cheap and small, they are definitely worth a look for this purpose. This will use the bluetooth on your phone as the source, and all you need to do is hook the amp up like normal minus the RCA inputs and hide it away somewhere. This Herdio marine bluetooth amp also comes with an external controller, so you can keep your phone in pocket.

Connections

Now that you’ve picked out your speakers and amp, you will need to get it all hooked up. You can follow my How to Install and Tune an Amp – With Wiring Diagram post if you need help wiring up an amp.

If you chose one of these smaller amps that don’t draw much current, you can just hook up power and ground at the radio connections (though you may need to run a separate constant power wire to the battery if your amp draws more current than what the radio fuse is rated for your car). You can either cut the wires off the harness or use an aftermarket radio wiring harness to make it easier, and you won’t have to cut into the factory harness. To find what harness your car needs, go to metraonline.com and search for your vehicle. You will be looking for a female plug similar to this:

Now that you have the amp wired up, you are probably wondering what goes into the RCA input. Go buy a cable similar to one of these RCA to headphone jack Monster Audio Cables and plug it into the amp. Run the other end up to where you will put your phone or mp3 player.

Now you control everything with your music player and do away with a radio completely. This method of simple sound also works great in Jeeps or anything else where you don’t need a radio in your car.

An alternate method would be to buy a bluetooth adapter like this one. This might be a little advanced for a race car, but it will get rid of an extra wire that may be in your way otherwise. And this one uses regular RCA cables to connect to your amp.

Now you can do away with your radio and any other factory sound system you have and get way better and louder sound than what came in your car and still stay light enough for the track.

Update

My personal setup in my Miata is a Pioneer mechless single din head unit with bluetooth and the factory speakers. The mechless (no CD player) radio is lighter and has more features than the stock radio. The one I have is very similar to this newer MVH-X390BT (check price on Amazon) and it works great.

In my STi, I have an Alpine Power Pack with an auxiliary cable for the input with a volume control knob where the factory aux input jack was running the factory speakers. I will soon be upgrading the speakers to these Sony GS components (check price on Amazon) / (read my review on them here) and possibly adding some sort of bluetooth. Sony also has a version of a mini amp like this that I have had great success with, but it is not bridgeable like the Alpine (check price on Amazon).

Update (1/20/2019)

I no longer have the Alpine power pack in my STi. I did install the Sony GS components and love them. Check out my review (here) and installation videos of them (here). I also added a Zapco ST-4XSQ amp and Sony XAV-AX5000 head unit. I may do a review on this soon as it is by far my favorite radio out right now for the price, quality, and features offered. I am a Sony and Zapco dealer, so if you are near Baton Rouge, feel free to call or email me for pricing and availability.

Many people like to save money by installing their parts themselves. It can also be fun and a great way to make sure it is done right. With this guide, I will explain how to install an amp. Whether it’s for subs or door speakers, the connections are still the same.

What You’ll Need

• Amp (duh)
• Subs/speakers
• Wiring Kit
• Aftermarket head unit or a line out converter to install with the factory radio

Amp/Speakers
The basics of amps and speakers can be found in Car Audio Basics and Basics to Upgrading Your System. If you have questions about how to match your amp and speakers, check out How to Select and Match Subs and Bass Amps. I will be doing a section soon on how to match amps with other speakers, but it is pretty much the same thing.

Wiring Kit
Now that you have your amp and speakers, it’s time to get the wires to hook everything up. For help selecting an amp kit, check out Selecting Amp Kits.

Aftermarket head unit or a line out converter 
In order to send a low level signal to the amp through the RCAs, you will need an aftermarket head unit or a line out converter. Aftermarket decks have RCA outputs built in (usually at least one pair even on cheap ones).

Factory radios do not have RCA outputs built in, so a line out converter is needed to convert the high level speaker wire outputs to low level RCA outputs. I will do a how-to on installing these soon.

Some amps have high level inputs. In this case you don’t need a line out converter or RCAs, but if you are using an aftermarket radio, it is still recommended to use RCAs.

Installation

Now that you have everything you need, let’s move on to the installation.

The first thing you’ll need to do is get your layout right. If you are installing a sub, get it in the box and find a place for it. Find a spot for your amp where you can mount it securely and it can get good airflow.

Now you’ll want to disconnect the negative lead on your battery. This will keep you from shorting out any electronics in the car during installation.

Once everything is laid out, you can start running wires. It doesn’t matter what you start with, but I like to get everything run a short distance to a common point where I can run it all back to the amp together with the exception of the RCAs. It is best to run the RCAs down the opposite side of the car to avoid noise.
See this diagram to see what wires go where:

Power Wire
This will be one of the biggest wires in the kit. There will big a long one and a short one. The long one is the power wire. This goes from the +12V connection on the amp straight to the battery.

There should also be a fuse holder and fuse in your amp kit. The fuse should be no more than 18″ from the battery. This keeps the shortest distance possible of wire getting hot in case of a short.

Ground Wire
This will be the short big wire in your kit. The ground wire should be as short as possible, usually 3ft max, and even that is long. This wire will go from the negative terminal on your amp to the vehicle chassis or body.

When making the ground connection, make sure the ring terminal is secured on the end of the wire and find a good spot on the body of the car to scrape off the paint and connect the ground with a grounding bolt or self tapping screws.

It is very important to have a good secure ground connection free of any paint, debris, or rust. A lot of problems are caused by bad ground connections.

Remote Wire
This will be the single long wire in your kit. It is usually blue. It needs to be hooked up to a +12V source that gets power when you turn the key on. This is the wire that tells the amp to turn on when you turn the car on.

For an aftermarket radio: There will be a wire coming off the radio wiring harness (usually blue with a white stripe) that is for remote turn on. Simply connect your remote wire to it and run it back to the amp.

For a factory radio: You will need to find your own source for switch power. Sometimes this can be caught behind the radio, but if not it may be easiest to run it to the fuse box. Either way, fuse the wire!

RCA Signal Cables
These are the cables that carry the low level output signal from the radio to the amp to be amplified. These run from the back of the radio (on aftermarket units) or from your line out converter (on factory units) to the RCA input on the amplifier.

I see a bunch of people hook up their amp with no sound to find out they actually plugged the RCAs into the output on the amp. The output is so you can link two amps together without having to run another set of cables.

Speaker Wire
You are now ready to run your wire to your speakers.

For speakers installed in factory locations (doors, rear deck, etc.) it is usually easiest to run wires behind the radio and cut the speaker wires coming from the doors to the radio and tapping into them there. This is much easier than trying to run wires into each door.

For a sub, you just run the speaker wire straight from the amp to the sub.

Now that everything is hooked up, reconnect the negative lead on the battery and move on to tuning your amp.

Tuning

Once everything is hooked up, you need to tune the amp. There are a few ways to do this: by ear (the easy way), by using a multimeter (the better way), and by using an oscilloscope (the max output way). My old boss swore that it is good enough to set the gain by ear, and it usually was for what we were doing. But I always set gains with a multimeter now.

First you’ll want to roughly set everything:

Filter
Set to low pass for installing subs and high pass when installing other speakers. This prevents low frequency sounds from damaging your mid or high frequency speakers and high frequency sounds from playing through your subs.

Filter Frequency
Usually set around 80-100 Hz depending on personal preference and the speakers used.

Gain
Start with this turned down. This is by how much the incoming signal is amplified which equates to how loud your speakers play. You can’t just turn it up, though, as this can damage your speakers even if it doesn’t sound like it. Setting the gain properly will prevent clipping and overpowering your speakers and increase the life of every component in your system.

Once all of these are set roughly, you’ll need to set the gain.

For this, use test tone frequencies from 0 to -10db. Use about 40-50 Hz for setting your subs and around 1k Hz for setting your mids. Test tones can be found here.

And I’ve also heard use 60 Hz for the subs and 100 Hz for the mids (with the high pass filter turned off). This is because AC voltage meters are made to measure 50-60 Hz tones most accurately. Measuring a signal much higher (like 1k Hz) will result in lower readings, so measuring 100 Hz will be more accurate since it’s closer to 60 Hz than 1k Hz is. But it’s not too low to blow your speakers.

Also make sure all the EQ settings are zero or off (loudness, bass, treble, etc.). Once you get the amps set up and you decide you want to use some sort of loudness or bass boost, I would recommend checking the gains again to make sure they are still playing unclipped.

Easy Way
This really isn’t a recommended way to set amp gains, but it’ll work and be better than nothing.

1. Start with the gain all the way down, and turn your radio up (playing the test frequency) to where it starts to distort and back it down a bit. On most radios this will probably be around 3/4 of the way up. You can go less to ensure your radio isn’t distorting but never turn it up past this level after you set everything.
2. Now start turning the gain up until your speakers/subs start to distort and back off a bit.
3. Done. Now play different sources of music to make sure one or the other isn’t a lot louder (which is usually the case). If so, set it to the source you use most and be careful when playing louder sources.

Better Way
Now to the better way, which is a bit more technical and requires a multimeter.

This way works great if you have an amp that is rated properly, i.e. CEA rated. If you have some cheap amp that says “1500W” and cost $25, that amp probably doesn’t do 1500W and you won’t be able to use this method.

1. Disconnect the positive speaker wires from the amp.
2. Determine gain voltage: V=√PR where V=AC voltage, P=power, and R=resistance. P is going to be the RMS power of your amp in Watts at the impedance of the speakers you are running. R is the resistance of the speaker. And V is the AC voltage we are going to calculate to set the gain. Here’s an example: You have a 4 Ohm 500 Watt RMS sub and an amp that puts out 500W RMS at 4Ω. V=√500×4=44.72V. We are going to set the gain to 44.72V.
3. Start with the gain all the way down, and turn your radio up (playing the test frequency) to where it starts to distort and back it down a bit. On most radios this will probably be around 3/4 of the way up. You can go less to ensure your radio isn’t distorting but never turn it up past this level after you set everything.
4. Set your voltmeter to AC voltage and put the positive lead on the positive speaker terminal that is disconnected from the amp. Put the negative lead on the negative lead of the speaker that is still in the amp.
5. Increase the gain until the meter reads your calculated voltage.
6. Turn the radio down, and turn the car off. Reconnect the positive speaker leads, and you’re done!

To easily calculate the voltage you need, check out the Car Audio Calculator Page.

Max Output Way
This method will get the maximum RMS power out of your amp before it starts to clip.

This way would be best if your subs can handle more power than your amp or if you think your amp may be underrated.

This method uses an o-scope or distortion meter to set the amp gain to the max clean level it can put out.

You can use something like this Pokit meter (I actually got selected for the beta testing and like it but the small size makes it kinda hard to use). The Pokit meter also has a max input of 42 VAC, so it’ll work for most stuff but not super high power amps.

Or an actual oscilloscope like this.

Or a distortion detector like the Steve Mead Designs DD-1. This is very popular in the car audio world and can take an input up to 125 VAC.

This method is similar to using a multimeter, but instead of setting the gain to a certain voltage level, you just set the amp to clip then back off a tad.

1. Disconnect the positive speaker wires from the amp.
2. Start with the gain all the way down, and turn your radio up (playing the test frequency) to where it starts to distort and back it down a bit. On most radios this will probably be around 3/4 of the way up. You can go less to ensure your radio isn’t distorting but never turn it up past this level after you set everything.
3. Hook up the o-scope or DD-1 to the amp channel you are setting.
4. Increase the gain until the DD-1 distortion light turns on or the sine wave on your scope starts to become flat (clipped).
5. Back off on the gain a tad until you have a clean signal.
6. Turn the radio down, and turn the car off. Reconnect the positive speaker leads, and you’re done!

Now that your gains are set, you can fine tune your cutoff frequencies to your liking.

Finishing Up

After all of this is completed, secure the amp and sub down to prevent them from sliding around and yanking wires out. Tire your wires together to make them nice and pretty, and your done! See, it’s not too bad.