Energy Efficient Stereo Project (audiophile nerdathon warning!)
 

Hey gang,

When I started working on my 98 Dodge Neon for my daily driver, MPG beast of a project, I decided to make a pure dedication to this project: To make it efficient in every single category possible. As part of my background, I have been building, installing, and tuning audio equipment for many years (as a hobby). I figure this would be a new challenge.

My goals for this project...
-Stereo system must be fairly easy to install and simple in design.
-All equipment must be as light-weight as possible.
-Speakers must have the most possible decibels per watt.
-Must be able to play enough low end to warrant a lack of a subwoofer
-Must be able to play a rather smooth response, getting with a few db of "flat" from ~40hz-20Khz.
-Must run on a single CD player (no external amplifiers)
-Don't go broke trying to do all the above

So, with those in mind, I'm happy to report that, after about a month of building, installing, and tuning, I have accomplished the majority of my goals!

The drivers chosen...
Aura 6" Woofer
Vifa 1" tweeter

First, the woofers. These 6" drivers should fit in the door. The only down side is, at 8 ohm, I would need 2 per side. This does hurt my goal of an easy installation, but help several other goals. Primarily, the more drivers I put in the door, the more low-end I can get out of them (for the most part). On top of that, I would gain a bit more volume levels out of having multiples.

These speakers are rated at 91 db/1 watt. This is an impressive number! This is about 6db louder than the average driver in it's class (guesstimating that number, though). To compare, it would take a driver in it's same class to have ~4x the power in order to accomplish the same volume levels. With two of them per door, we are looking at ~94 db/1 watt (you gain 3 decibels when you either double your power or double your displacement).

These speakers also have a decent amount of throw at 3.9mm xmax. This is how far the cone will travel before distorting, basically. This should help the bass response from these little guys.

These things weight in around a pound a piece! This is very light-weight. You can thank the neodymium magnets and "cheap" construction on that. The paper cone is not the most durable material, but it reduces weight and resonance, which is great for a speaker.

Finally, these are $9 each. I don't think in today's world you can find a better contender for my requirements for this project, even if these were $20 each! But at $9 per driver, or $36 for 4 in total... Sold.

Next up, the tweeter. I wanted the tweeter to go into the stock location and keep up with the drivers very easily. This tweeter, by it's specs, have no issues with even a duo of Aura drivers!

The tweets rank in at a whopping 96db with a single watt applied to it. This is (guestimating this number again) 10db more than the average tweet. 10db is DOUBLE the loudness to the human ear! This tweet is nearing the professional sound stage loudness, at a size you can put in your pocket.

Once again, we see neodymium magnet construction, keeping it ultra-low weight. They are small enough to just fit in the dash, where the stock speakers once sat.

The only issue with the tweet selection was that I really wanted to keep the tweet crossed over as low as possible. I am a big fan of having tweets do a lot of the detailed work. I would have loved a 1.5Khz crossover point, but this tweet just isn't build with bulk duty in mind. Again, a compromise... but at $17.25 a piece and meeting my other requirements so well, it was a small compromise at that.

I already had a CD player ready to go: The Pioneer Premier 860MP. It was perfect, too! Well, the CD player itself has been beat over the years and the face plate doesn't open... and the CDs barely eject... but it has plenty of tweeking and tuning capabilities. Most importantly, it has a well integrated active crossover network.

The plan was to run this CD player in it's "Network" mode, which allows you to replace the Front and Rear speaker output for Tweeter and Midrange driver options. This allows for heavy crossover settings and adjustment capabilities. This saves on the weight, complexity, cost, and efficiency loss of a passive crossover.

OK, let's get to some pics. Sorry for the long, detailed posting. I love to write... hate to read. If I were anybody else, I'd skip right over these details and go straight for the pics... so on with the show!

You can visit my photobucket account for many, many more pics, but I'll just get the main ones in this thread.

http://i95.photobucket.com/albums/l1...627_202229.jpg
http://i95.photobucket.com/albums/l1...702_174025.jpg
http://i95.photobucket.com/albums/l1...704_154100.jpg
http://i95.photobucket.com/albums/l1...619_170008.jpg

That's the cliffnotes of the install. Made baffles out of 1/2" MDF, angled to taste, fiberglassed, installed. Mild door cutting involved (didn't need to, though). I sealed the doors up for both acoustic and thermal isolation with a mix of chloroplast, aluminum duct tape, and foil bubble insulation. Currently using stock wires, though I plan to replace with something a bit more sturdy and larger gauge in the future. The door panels will be "prettied up" later, as the audio system is functional and other priorities beckon.

The tweets were a simple piece of 1/8" hardwood, cut out as an adapter, and installed. Had to run new wires as the factory wiring was just spliced into the door speakers.

After the install, I set the crossover network to 24db/oct on all the following settings...
Woofer High Pass 31.5Hz
Woofer Low Pass 2.5Khz
Tweeter High Pass 2.5Khz

I then went through and setup my meter to get the EQ set...
http://i95.photobucket.com/albums/l1...712_184210.jpg
http://i95.photobucket.com/albums/l1.../EQcompare.jpg

I still have some setting adjustments to go through... but after seeing my graph and listening to several different albums... I can firmly say: Mission Accomplished. I can throw in something with a good amount of bass and get enough of it to rumble my chairs a bit, but most importantly, as a lover of Rock genres, the kick comes through without flying color(ation)s. The details are perfect. Loudness wise? Seems to hold 100db constantly with peaks of 104+, no distortion. This is coming from my deck, which is ~22watts RMS per channel (total power combined is roughly 88 watts).

Revisiting the goals...
-Stereo system must be fairly easy to install and simple in design.
Used most stock locations and wiring!
-All equipment must be as light-weight as possible.
Without a doubt!
-Speakers must have the most possible decibels per watt.
I don't think I could find much better than what I went with.
-Must be able to play enough low end to warrant a lack of a subwoofer
It goes down to about ~45hz pretty easily, good enough for most music!
-Must be able to play a rather smooth response, getting with a few db of "flat" from ~40hz-20Khz.
Still needs tuning, but I believe I can get it within 3db of a flat response!
-Must run on a single CD player (no external amplifiers)
Check!
-Don't go broke trying to do all the above
Drivers were around $67, had CD player already, construction materials ~$25... Under $100! Far from going broke.

I believe I hit all my goals. There is always room for improvement, but I am satisfied. If I ever feel I need extensive low end and can't get it out of these, I may find an efficient class-D subwoofer and redesign the rear end for an "enclosureless" sub... would only add 10lbs or so... but this should do the trick for now.

I know this isn't an audio forum. Sorry if this isn't something that should be posted here. I just figured that there might be some people who wanted some ideas in the future for their own stereo upgrades, without adding the weight or power drain of a complex audio system in their vehicle. Most people have to run heavy copper wiring, large and weightful amplifiers, and expensive speaker components in order to accomplish the same thing. The initial up front cost is less than a single amplifier alone... I couldn't imagine huge fuel savings, but when every little bit counts...

Thanks for reading.

I love stereos.
Those tweets up front will sound great.

You matched your stereo well, no need for big amps in a small compartment, I'm not using any amps either, even though i have 2 from a previous vehicle.

I put a top of the line Kenwood excelon deck in the Beetle, 4 x 45 watts, control over bass cut off frequencies and cross over frequencies.
No need to use cross-overs at the speakers, but i do, to further cut off the frequencies.
I picked up a older bass cannon Bazooka tube, but have yet to install it.
My plan is to mount it where the stock cd player is in the back.
If you can run a mp3 player off the deck it would consume less power then playing a cd.
My deck has a input for an mp3 player or what ever uses a mini jack.
I have a extension mini plug line off the back off the deck,then use it to plug my iphone in and play tunes off it.
I have got say, you got a pretty nice sound pressure reading off those speakers.

Thanks, ecomodded. Glad to see other stereo lovers on here.

I actually have a phone dock and can play through it... though, I'm charging my phone with the 12v system by doing that. However, I have eventual plans to change my sunroof into a small ~80w solar array, which should help cover some of the electrical costs.

As an update, I did a 2nd round of tuning. I knew there was room for improvement... I think I got it pretty fine tuned this time.

http://i95.photobucket.com/albums/l1...comparison.jpg

Very nice work. I too am a recovering audiophile...

If you decide to add a sub at any point look into getting a T-class amp I know people have used them to power PA speakers on trikes and can use relatively small batteries and have a long play time.

I need to change out the deck in my golf for my nice pioneer unit, and remove the 6disk changer from the back. That will remove a few Lbs and give me a little more storage space in the back.

I asked the guru at alpine how to bi-amp my setup. I currently run focal poly v which are 92 db/w. i'll get more output at the front, cleaner sound, and a little more power without the passive crossovers. Do you use brown bread or dynamat?

I see you get virtually inaudible sub bass. I thought I could live without my sub...but it makes me happy - even though the box is 55 lb alone :o. Maybe I could save a few lb switching my 12" for two 8"?

I used a minimalistic amount of dynamat and fatmat... whatever was on hand and cheap! ;)

My fronts get enough punch for most of the rock/metal I listen to. Sure, a sub would be nice... maybe in the future.

For light weight, there are a few options...

heavily braced 1/2" MDF
Fiberglassing non-flat boxes (spherical if possible)
Infinite Baffle

I'll be going the infinite baffle route, if I end up with a sub. I'd prefer a single 10" or larger... but depends on the subs of course. I have 2 18" Fi Audio IB subs in my home theater... plays flat to 7hz. ;) lol

Lol. Beats my single 15" ht sub :)

I've looked at cylindrical boxes, mdf and fiberglass. Hugely lighter, and complicated to build. I'll look at ib. Would you mount it in the parcel shelf?

With my car, I'm planning on removing the rear window (ultimately) and making a "hatch back". The back can do 2x 6x9 speakers right now, but would be able to do a 10" or 12" sub pretty easily. Would have to brace it well. Getting a good seal is critical for IB setups, which is where it gets tricky. You can also do "half trunk" setups, where you mount the sub on a single board and have that board sealed off, making 1/2 the trunk the box. Can always go less than half, just depends on your car and how you can pull it off... but there's quite a few ways to go about it.

In my experience, you can get the bottom octave (20-40Hz) in a car without too much effort; since a car is a sealed "room". I used two 6x9 Boston Acoustics woofers that I added about an ounce of epoxy to the cones and mounted them on 1/2" CDX plywood. Using the old Stereophile CD test tones and a Radio Shack SPL meter, I had nearly flat extension down to 20Hz.