Technical Sources for car audio system design

Guys,

I would like to bone up on designing a car audio system. I know very little. Not wanting to compete in any competition to make your ears bleed. I would just like to understand the mechanics of it. I have looked on Amazon and there are tons of books out there, but just like hot rod books, some are far superior. Who or what would you recommend? I would like to design my own system for the 36 pickup build I am doing next.

 

I just upgraded the stereo in my wife's BMW and https://www.crutchfield.com couldn't have been more helpful, easy to deal with, and good pricing on components. They have a very good tech support division and very good ratings on customer service. If you are going to do the work to install it all and wire it these guys might be a good option.

 

I have talked with them some. They get a little confused when you tell them it's for a 36 Ford. They kind of start stuttering.....

 

It's as much art as it is a science... Yeah, Crutchfield won't be much help on component selection if your car isn't in their 'system'.

There's basically two design aspects of car audio; speakers and their enclosures (IMO the most important part of your design), and the electronics to drive them. The electronics is relatively straightforward; making sure you have enough power to drive the selected speakers at the volume you want without the amplifier clipping (being unable to furnish enough power). Your options are nearly unlimited depending on system features you may want. The fly in the ointment is the industry has gone away from tape and CDs and gone almost entirely over to digital playback, i.e. thumb drives, I-pods and cel phones. For early cars, I personally like the Retrosound head units as they offer a 'modular' design that allows you to separate the volume/tuning knobs, display and main electronics if needed for full custom installs, particularly where space is at a premium.

Speaker selection and their enclosures is where the 'art' can come in. '49-up cars are relatively simple, as they have 'naturally occurring' enclosures (the doors, quarterpanels, package trays) so packaging the speakers usually isn't that hard unless concealment is a big issue. For trucks, the mid-50s-up versions with their deeper doors can be done fairly easily. Generally speaking, the larger the speaker enclosure, the better the sound.

Older cars and trucks can be very difficult as there's a limited number of places you can mount speakers; trucks are particularly hard to fit. The acoustics inside the vehicle make a big difference; a speaker that sounds great in one application may sound like crap in another. Finding room for adequate speaker enclosure volume is a real issue.

Ultimately, every system will have compromises that will affect the sound quality. What 'quality' that's acceptable to you is a decision only you can make. If you're happy with a vintage OEM radio sound, a system may not be too hard to design. As sound quality, imaging and accuracy desired goes up (and I'm not really talking about sheer volume), the degree of design difficulty goes up too. Along with the cost....

I'm a audiophile (I've got literally thousands in my home system, and it's far from 'the ultimate'... LOL), so if you want to discuss this further, PM me...

 

Thanks Steve. I was pondering a bluetooth amp and no head unit. 4 speakers and maybe 1 sub. It's understanding the design so that the components can be integrated and hidden in the truck. I am sort of OCD on stuff, so wires just running across the floor under the carpet stress me out.

 

I figured you could use them for the components you decide you want to use and let them tell you how they work together. As with most things in hot rodding there isn't going to be an off the shelf system for a 36 pickup and I wasn't suggesting that. Your going to figure out mounting and housings anyway so you might as well get the parts of the system at a good price.

 

That's where I buy some of my stuff. They are pretty decent.

 

I'm not a fan of Bluetooth or MP3, as the trade-off in sound quality is more than I'm willing to accept (basically about the same as a '70s-era cassette minus the tape hiss). Virtually all the 'compression' schemes degrade the sound some, some more than others. But if that's good enough for you (and it will depend on how noisy the vehicle is; if it's very noisy, the noise will drown out most of the differences you'd hear anyway), then I'd recommend just two speakers, 6" round or 6"x9" two-way and skip the 'sub'. Keep in mind most 'car audio' subs aren't really subwoofers; they're just woofers and a good quality full-range speaker can deliver equal or near-equal performance. If you want a 'true' sub, you're talking a speaker size of at least 10", preferably larger and packaging the proper-sized enclosure to actually get the sub to perform will be very, very difficult in the confines of your cab.

I think the questions you should ask about speakers are these:
1. What's the frequency range of the speaker? Most good full-range speakers in the larger sizes can go as low as 40 hertz with decent output. The smaller so-called 'subs' won't go much lower and what little you'll get will tend to disappear due to vehicle noise.
2. What's the recommended minimum enclosure size? This is really the crux of the matter; how much room will you need for an enclosure. Bigger is usually better, but keep in mind that that one 'great' speaker with a minimum-sized enclosure may not sound as good as a 'good' speaker with a larger-than-minimum enclosure.
3. How much amplifier power does it need? Keep in mind that the speaker manufacturers shamelessly lie about 'minimums' required to make them more attractive to buyers, if you like to put much volume on them try to at least hit the mid-point on amp power. And power required goes up exponentially with volume level; if the amp starts clipping, not only does sound quality drop but actual damage to the speaker can occur. Too little power can be as bad as too much.

You might even consider small 'bookshelf' home audio speakers that you can easily install/remove. I've got a set of ancient ADS 200S speakers (bought in the '70s) that are still my go-to 'temp' speakers if I want tunes but if I'm not ready to cut any holes. Small (7"H x 4"W x 5"D), with a cast-aluminum enclosure, these have pretty decent sound as long as you put enough power into them. They sound pretty good with a 75W-per-channel amp, although they sound better with more power. These are long discontinued, but they still turn up on the used market (and still fetch good prices even today). For current offerings, I'd also look at outdoor or marine units.

 

Excellent replies, Steve!

I've noticed that I'm not an audiophile at all, and mp3 recordings have to be really crappy for me to hear the distortion.

Also my old heaps are pretty darn loud, so it's not like I could hear much sound quality, imaging, or accuracy....

This was a pretty good system, aside from the problem with the old inverter not being quite 60 Hz, and the media being 40-50 years old and in pretty bad shape.

 

Not sure I've ever seen a car sub that hasn't been an actual subwoofer, have any examples?

sent from my toilet

 

Yeah, after years of guns, airplanes and hot rods I am not going to hear the difference. The high pitched whine I have pretty much drowns out most anything that would be heard at that frequency anyway. I just like music. Some folks like talk radio, I like uninterrupted music, thus the mp3 or bluetooth transfer.

Was looking at something like this.

https://www.crutchfield.com/p_109GT...&awnw=g&awcr=104893290145&awdv=c&awug=9026218

I like the D class stuff because they seem to run a lot cooler. Don't need anymore heat in the cab.

I have no room for any kind of bookshelf speakers. It's wall to wall in there.

 

It's not really distortion, it's more all the stuff missing. All of the compression algorisms compress the full-range recording, discard large or small chunks of it, then play back what's left. Harmonics, echoes, ambient noise, some part of the frequency response, all things that help 'flesh out' the recording may or may not appear on the decompressed recording. To me, MP3 recordings sound 'one dimensional' and a bit lifeless.

The other thing that's funny is all the used home gear you show is probably equal to or better than most modern car audio (well, except for the 8-track... LOL). The distortion numbers (when they give them) for car stuff would get you horse-whipped out of the CES if you showed up with home gear with those specs.

 

is this with a particular person in the car or all the time? If you can find some car stereo geeks (think dB Drag racers etc) They should point you in the right direction for the cost of a ride in your car.

 

I'll be following this thread, I'm building a '33 pu and since the wife is calling dibs on it, I'll probably have to install a sound system. She's a big iTunes, Pandora fan. Me, I'm more like Squirrel but I've advanced to the cassette/CD level.
Even in my quietest old car (my '56 Chevy), the road noise and general engine noise makes serious listening a joke while driving. It sounds great when you're stopped. It has a Pioneer head unit with four 6" coaxial speakers as recommended by our local car audio "expert". I'll put in some better sound deadener when I swap out the seats.
In my other hot rods I didn't even bother with a sound system. I'm so glad they invented those blue tooth ear pieces, now I don't look so silly when I'm driving along singing to myself - people just think I'm on the phone.....

 

Oh, any 'sub' that's 8", about 95% of the 10", and a fair number of the 12". Once you get to the 15" size you see real subwoofers.

A good, larger full-range speaker can have usable LF response down to 40 Hz. Most car 'subs' are only good to 30 Hz, it's only when you get into the better 12s and 15s that you see usable response below 30 Hz and particularly down to 20 Hz. Worse yet, the smaller subs reach all the way up to 200 Hz or more, degrading your stereo imaging unless you pay close attention to your pass filter settings.

Car audio is still infested with a lot of smoke-and-mirrors marketing. While the FTC imposed a set of standards on the home audio market so you could make meaningful comparisons, that hasn't happen in car audio. Explain to me how a car amp can have a 30 amp input yet 'produce' 750 watts (100 watts x 4, 350 watts x 1) with only a 360 watt input...

My home amp makes 500 watts x 2, but needs 1800 watts to do it...

 

This is good timing for me. I'm just getting into my 53 F-100 project again and hope to see it to the end this time. Some 20 years ago I bought a ton of sound stuff for it at a Car audio store. All that stuff is still new in the box. I know less than Zero about how to make good sound and now with hearing aids I doubt high quality is an issue for me. I would however like it to be done the best it can with what I have. I had just last week pulled everything out to see what it takes to mount the player. Think I'll go wright down the info on all the pieces and just maybe Steve can add some info to get me headed the right direction.
The Wizzard

 

Didn't they have problems with capacitors about 20 years ago?

 

This is my go to place for all things audio

 

And to think my home stereo/record player has a tube going out and the volume starts going up and down when the tubes get hot and you guys are talking capacitors !

But I love the sound it produces!!

 

Ok, I'm not a stereo pro by any stretch but I have installed my share of systems over the years (good and bad). I agree with Steve about the MP3 files lacking fullness BUT what they lack they make up for in versatility......you can take them with you and you can have a large selection at your fingertips (I have over 10k songs on my iPod and usually play it on random in the car). What I know is enclosures make speakers sound better, more watts per channel the better and it's a pain in the ass to hide stuff.

I'm my '41 I went with RetroSound because of the modular system, old looking and features. Also if you have a stock radio you can convert it to a more modern set-up with higher wattage, Bluetooth, MP3 via 3.5mm plug or thumb drive and hands free phone. If you like to play with circuit boards and solder,
http://www.tech-retro.com/Aurora_Design/Automotive_Home.html

There's a few guys here on the Hamb that will convert it for you.

On your '36 it's a small cab, 2 speakers (6-6.5 or 6x9) and a powered sub (if you want the punch) should work very well. I would also hide a USB charger under the dash to charge the gadget of your choice.



Here's my '41 and it sounds goooooooood.
https://www.jalopyjournal.com/forum...lly-i-gotta-stop.1057277/page-5#post-12242904

 

Lots of great info here; http://www.diymobileaudio.com/forum/ (I've been a member for 7-8 years.)
It's mainly an SQ (sound quality) oriented forum, with a couple "bass heads" hiding in the shadows.
I've been into car audio for nearly 25 years. From competition level, to bare bones, and everywhere in between.

Key goals to address when planning a build;

1) Budget
Self explanatory, but typically the primary tool when deciding how to best allocate your available funds.
IE; don't spend 3/4 of your budget on great speakers, then go cheap and buy a flea market amp and CD player.

2) Space/install limitations
This will be a big factor in a small cab.
What locations do you have available to install;
A) Source unit
B) Speakers
C) Amplifiers

3) Aesthetics
Ties into install, but can be more important in older cars, like ours.
(Big shinny CD player in the dash looks fine in a Honda, not so much in a Deuce roadster)
Will this be a stealth/hidden stereo, or limitless, as far as looks go?
How much interaction will you want with your stereo?
(Do you constantly change songs/volume, or do you just listen?)
(A stealth glove box mounted stereo can be nice, but difficult to access while driving.
This will help when choosing equipment.

4) Expectations
What are your typical listening levels for volume?
Making a low volume stereo sound good is easy, however, as the volume goes up, lots of other factors start to play bigger roles in maintaining the same level of sound quality.


Sound deadening is the first thing I would plan for.

CLD (Dynamat) does not have to completely cover every surface! 25-50% is fine.
The key is to put it where large open panels can resonate.
There are lots of cheaper options from Fatmat, Hushmat, Knu Concepts, ect.
A complete layer of MLV (mass loaded vinyl) is my recommendation for the primary noise barrier.
You can find bulk roles on Amazon; https://www.amazon.com/Loaded-Vinyl...=1427585168&sr=8-2&keywords=mass+loaded+vinyl
There are smaller roles available also.

Couple threads with info;
https://www.jalopyjournal.com/forum/threads/whats-the-best-insulation-for-heat-and-sound.60862/
https://www.jalopyjournal.com/forum/threads/best-sound-deadener.977364/#post-11568240

IMO, a pair (or two, if you have the room) of 5.25"- 6.5" co-ax speakers (has the tweeter mounted in the center of the woofer) paired with a small subwoofer, should be more than enough to get good clean, full sound, in a small cab.
Kenwood makes a nice slim under seat subwoofer, that has the amp built in, and can fit almost anywhere.
If space is an issue, look at "micro" or "mini" or "motorcycle" amps.
Lots of good companies making amps the size of a post card, these days.

If this is deemed too off topic, feel free to PM me, or sign up at DIYMA, and we can continue the convo.

 

Well here's the info I have for now. What I have is a brand new in the box Alpine Cassette player. Ya, Strange. I doubt I'll be mounting it in the Dash. It says 25 W x 4 amp. Can the player have the amp in it? Then there's a new pair of 1" Silk Dome tweeters 60 W 24 Hz. A pair of Lanzar 6.5 midrange drivers 150 W 4ohms. An Olympian 8" Subwoofer 46oz Magnet 120 W with 2" 40 Ohm voice coil. An Alpine Bridgable power amp 150 total output. Then I seem to have added a new remote 6 disc CD player. There was a receipt with all this stuff and I believe it was dated 1992. Geezzz! This may be over kill for a small Cab truck.
The Wizzard

 

The cassette player and CD changer if not DOA probably won't live long after put into service because there's all kinds of rubber bits inside those that will go bad with time and disuse... Both obsolete anyway....

The rest of the stuff should be usable, but look for the dreaded 'foam rot' on the speakers. Again, this is age-related but will depend what material was used for the surrounds. I haven't heard of either speaker manufacturer, but that doesn't mean much.

 

In my 35 phaeton I have an older AM/FM radio cassette with CD stacker. I downloaded a program that allowed me to convert all my CDs into MP3 format on my PC, I then copied all the MP3 files from my PC onto a micro SD car in my phone. Next I bought a cheap iSimple. There are a few other options on offer if you look at the site.
I can now play all my music direct from my phone through the cassette player after I plug the device into my phone. Pretty simple stuff. I only have 2xF & 2xR speakers in the 35 and the sound is OK. I have tinnitus from work and manage.
In my 46 closed car I will do the same however I have an amp and subwoofer this time around.

 

The reason I am researching this, is I bought a bunch of nice stuff for the produce truck, to run through my phone. It took me 5 years to complete the truck, so by the time I got a round to hooking it up, everything is out of warranty. It has never worked, I think my amp may be bad. I just want to learn and understand up front, so I could test it on the bench this time.

 

Thanks Steve; I hadn't thought about actually using the cassette player being I don't have any to put in it. Roothawg makes a good point of bench testing things before doing an install. Maybe I should fire it up and let it run in the shop for a few days to see how the speakers hold up? What are your thoughts on using all this stuff in such a small space? If I remember right I was told to mount the Tweeters up high around the sun visors if possible. Does that sound right? The player itself for AM/FM should be ok to use, right?
The Wizzard

 

I had bought those micro tweeters for the overhead above the windshield in the Produce truck, 2- 6" speakers in the kick panels and 2 10" subs under the seat in the old fuel tank, an Alpine amp. I used the Isimple connector and an amp volume control knob. Something in all this stuff is the culprit.

https://www.jalopyjournal.com/forum/threads/the-legrange-produce-tribute-truck-build.936696/page-11

 

Roothawg; When you say "it has never worked" how do you mean that? Volume controll, balance or?

 

Sounds like we have the pieces for the same basic system.

 

There's so many ways you can skin this particular cat.... Personally, I'm not enamored with the use of separate component speakers (tweeters, mid-range, woofers and subs). If you're chasing the best possible sound, that's the path you want but it comes with it's own set of issues. First, you have to come up with mounting points for each component. In anything built before '49, this can be difficult if not impossible, particularly if you're trying to conceal the install. I can't emphasize the importance of proper enclosures too much if you want the speakers to perform to expectations. Second, it will be your job to balance the system; level controls into each speaker and crossovers can be needed, maybe even an equalizer (yet another component you have to hide). Using a two or three-way speaker can eliminate this issue as the manufacturer has usually already addressed this.

Third, so-called sub-woofers. These became 'required' somewhere along the line, primarily because of home audio speaker manufacturers figuring out they could reduce the costs of speaker systems by removing the low frequency requirements from their 'main' speakers to a 'sub'. Home theater accelerated this change, as large speakers dominating a room became unpopular (primarily with 'significant others'). Go into any medium-to-higher-end audio store and as speaker performance goes up, these systems disappear pretty quickly. Of course, the car audio manufacturers were quick to climb on the bandwagon, seeing an opportunity to sell more 'stuff'. But are they really needed? A case in point is my OT '13 Mustang. Equipped with the 'shaker' optional audio system, it has two 6.5" speakers in the doors, two tweeters (also in the doors), and two full-range speakers on the package tray; it doesn't have the optional sub. This puts out great bass at any volume level I use while driving (and I do like it loud sometimes; my home system packs 1400 watts total and I use all of 'em on occasion) because Ford paid very good attention to the speaker enclosures which is one reason it performs so well. Most 'subs' are 'fixes' to cover up the inadequacies of the 'main' speakers and/or their enclosures. If you spent the money needed for a typical sub (sub and dedicated amp) on higher-end main speakers, more power to the mains, and proper enclosures, you probably won't hear the difference unless you like loud thumping bass or like to bounce quarters on the deck lid...

True subwoofers are a different kettle of fish. These are the 12" and larger speakers, designed to reach down into the low 20s Hz (or even lower in home systems) for added punch. In a home audio system, they can add a whole 'nother dimension to the sound. But the home environment isn't the same as a vehicle; you don't have the ambient vehicle noises to deal with that will tend to drown out the LF information you'll hear at 'normal' listening levels. These are for the quarter-bouncers IMO, at sane volume levels much of the effect will be lost.

But at the end of the day it's all opinion; virtually every system will have compromises in it, whether it's install issues or budget considerations. I've spent a lot of money chasing ever-diminishing returns on my home system, but have stuck with the KISS principle for my car audio because I haven't seen enough improvement in sound quality to justify the costs or install issues.

And for some context, the system in my avatar is an inexpensive JVC in-dash AM/FM/CD receiver dash-mounted in the '41 Ford dash speaker hole (yeah, it's butt-ugly, but it fits... barely) and a pair of 6" round speakers (Kicker brand IIRC, and the largest that would fit on the narrow package tray). The speakers cost more than the head unit. I consider this only 'adequate'; at the time I didn't have spare money and I'm planning on a dash change down the road using a Retrosound unit for better visuals. It really needs more amp power and another set of speakers up front. The plan is to cut speaker holes in the body at the kick panels so I can conceal the speaker enclosures under the front fenders. The doors are too shallow for most speakers, plus they'll be too obvious there.