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Video: Improve Your Sound by Adding an Amp and Sub

Our Car Stereo Proving Ground, Part 2


In the second installment of our Car Stereo Proving Ground series, we added a bass system (subwoofer and amp) and an amplifier to the speakers. Anyone who's ever done this won't be surprised to hear that the music opened up and sounded better. What really impressed us, though, was how much a top-quality amp improved the sound quality and the overall listening experience in this Ford F-150.

Watch this video for the overview of what we did, and then read the full article, Adding Amps and Subs, to see the numbers.

And in case you missed the first part of the series, you'll find it here: Receivers and Speakers video.

This article is really about improving the sound, and making certain that everything that we do is about improving the sound at every little detail. The first thing that we did is we replaced the speakers. This time we've chosen a speaker which is kind of an in-between an ultra high end speaker, and an entry level speaker. And it's a JL component system which has a coaxial design, but it comes with an outboard crossover network which is really infinitely variable as far as the ability to change and fine-tune it to my system.

And one of the coolest things about them is that we have four different tweeter level attenuations that we can go: plus 2db, nominal or flat reference, down 1-1/2db or down 3db. And we also have the ability to adjust the presence of the midrange.

We've added in the Alpine Power Pack amp, which gives us 45 watts by four in an amplifier that literally plugs in behind the head unit. But this little Alpine Power Pack is a great little product. This one works with Alpine head units and adds instant 45 watts RMS power. And the best thing is, you simply unplug the Alpine harness, and then you've got your aftermarket harness which we provide when you buy a head unit from us. Click it in, and you're done.

So this step is going to give us more volume, is my prediction, but also better frequency response overall. So one of the keys to this test is that we're able to recreate what we're doing every time. So we're putting this tripod back into the same location, and we're doing our best to simulate that this is about where my ears are listening, so when we set the RTA we know we're getting as accurate a measurement as possible. So here it is.

We've just run the RTA, the real-time analyzer, with some pink noise and we've captured - and again, this is at the point of clipping, where the head unit and that little amplifier start to clip. We use the oscilloscope to determine that, and we can see by the RTA that the frequency response looks even better than it did with the aftermarket head unit. And that's due to more power. More power's always gonna give us a more smooth response.

When we switched from the really efficient speakers to the more high end speakers we did lose some SPL, which frankly is to be expected because we've got a crossover in the way, and that crossover has resistors which ultimately affects how much power gets to that speaker. What we also saw was that the frequency response on the RTA looks really pretty darn good.

The best news for us now is the fact that because we've put in a better speaker that has these outboard crossover networks, we're actually able to fine-tune this response with the crossover network. Even if I had only had a hundred and twenty dollar head unit without an internal EQ. So when it comes to the imaging, you know, Dave Matthews is singing now and I can hear his voice relatively centered. There's still a little bit of left-right biasing going on. I really feel like the band is kind of in front of me and I can pick out each individual instrument and it's getting better. Is it as good as it can be? Absolutely not, but we're certainly getting there.

So after testing several different locations and looking at the RTA, we know that we want to remove or pull the midrange down just a little bit, and we also want to back off the tweeters down 1-1/2db. 3db was way too much. So we're gonna put that back together, and I happened to find this really cool kind of hiding spot in my Ford F150. I wired these through the door and I'm able to actually mount this. I'll mount it permanently afterwards.

The subwoofer certainly added a ton of low end. As you can see, we're actually off the chart in a couple of frequencies here, probably the resonant frequency of the vehicle. The transfer function is really hopping. But it sounds great. It's nice and tactile. It's giving me that impact that I want based on just a little brief listening to music, but we should really get it back in the driver's seat and take a listen to music and then give an overall evaluation.

So overall, I don't think we've really changed much from the last imaging and the soundstaging point of view, but with the exception of adding the bass. We finally have brought the bass into the equation, and it's pulled, the illusion is still the same. It feels as if it's still in this middle area, you know, about this high on the dash, but it feels cohesive. It doesn't feel left and right. It feels kind of panoramic and allows me to feel that energy across the stage in the front, but most of all the bass just gives me good feelings.

I mean, it just makes you like to turn it up, and you kind of want to just feel the music. So that's the part I like about the bass so far. Next is, I think in my mind, the most important thing that you can do for your system, which is give it a big engine. And what we're gonna do next is add a really top of the line 4-channel amp. We're gonna replace that little power pack amp and we're gonna put something in here that has lots of headroom - lots of dynamic capabilities so that the subtle things are more subtle, and the loud things are even more loud. And there's a bigger difference between the two.

One of the interesting things that we've noticed when we were calibrating this system is that now we have more headroom in the volume control on the Alpine head unit, because we used to be really only able to turn it up to around 21 - was where it clipped using the internal amp and the high level outputs.

When we switched to the RCAs, then it doesn't clip the RCA signal nearly as fast, which allows us to get more voltage out through those lines to the amplifiers - which then gives us great potential for more head room in the system, and just better sound overall. So let's take a look at the frequency response and see what it did.

I think what we're seeing is a nice response in the bass, and it rolls down here a little bit, and then relatively flat. There's probably some peaks around 800 hertz, and that could have to do with the shape of the cone being a 6x8 versus a round cone. Probably around the crossover point with the tweeter we're seeing some dips. We'll also change the switches on the crossovers. Now that we've put more amplification behind them we might find that makes a big difference as well.

But overall, I'm very pleased with the way this is looking. And it can really, you know, it's probably just going to sound even better because now we have much more dynamic range and headroom and power behind it. So let's take a listen.

Wow! You know, this is one of those intangible things that a spec of an amplifier is never going to tell you. And, you know, often times we struggle at Crutchfield, because we know that better amplifiers sound better. But if you look at the specs on a page, you know this one may say it's 500 watts and another one may say it's 500 watts, and certainly looking at a web site or even a catalog page it's impossible to tell why it sounds better. And to me this is the quintessential proof in the pudding, because what we've just done is we've added a ton of amplitude, volume, to this system.

Mostly what I'm getting is this really awesome details, things that are just subtleties and nuances in the music. And it's no longer smeared. It's no longer just a big broad brush stroke. It's finite little tiny details that really make the music sing. I think this is probably the biggest step that I've heard. Of course the bass added a ton but frankly we knew what the bass was adding. It was adding all of the stuff we were already missing.

This has just opened, it's like taking away the curtain from the music. And it's really made it lifelike. The image has changed for sure - I'd say it's gotten wider and bigger. It's still pretty centrally located right here. I'd like it to be a little higher, but overall, but wow, compared to.remember where we started, the factory speakers sounded like this and in fact, I never even heard that right speaker 'cause this one was so on top of me, that that's pretty much all I heard. So already a humongous difference and I really like the feel.

I think this truck has a limitation in the location of the factory speakers, and that's something we might play with again. You know, maybe trying tweeters up here. I might actually build some pods up in the front corners just temporarily to see what those sound like with the new speakers. Just get geeky in the labs, you know? That's what we do. So thanks for joining us. It's been very cool so far, and the next step should be awesome.

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