There's quite a lot to know about getting really good car audio, and setting it up so it’s hidden.
(I studied sound engineering a good many years back, so maybe heres a start.......) lol
Probably a first important thing to realise is that "Watts aint Watts". Really! There has been a rip off going on for some time now.
The power output of an amplifier, is only correctly measurable in Watts RMS. When speaker performance is given in 'Watts', its pretty difficult to know what is being described. However a value in Watts RMS is usually a measurement of the power the manufacturer claims it can handle. (Speaker output is measured in Db SPL at 1metre).
The standard test for the Watts RMS measurement is to run an amplifier (or other component) until it reaches its average working temperature, play a piece of music through it chosen as one which covers the full human hearing frequency spectrum, - or more usually a series of test sine waves which cover the full human frequency hearing spectrum (approx 20Hx - 20kHz), turn it up in a testing studio as loud as it can go but (importantly) without any distortion at all, and then run it at that level for five minutes.
If any harmonic distortion occurs in that five minutes, the amp (or other component) is turned down, and the test run again until it can achieve the five minute run without any harmonic distortion. Once that level has been determined, the output of the unit is measured. This provides a measurement in Watts RMS.
It’s the only true quantifiable power rating that can be given for domestic/car audio or (e.g.) PA system component.
However, during the 80's, it became desirable for manufacturers to advertise that their product delivered more "Watts" (a term the public had now got hold of) than a competing manufacturer. "Hi Fi" audio is very hard to do, in the eighties only the very best brands were getting there, the problem is not just reproducing the full human hearing range evenly, it's in doing so at volume, very generally, the louder you get (depending on the amp and speaker design) the more roll off you get top, bottom, and mids often unevenly, - and with the cheaper gear the roll offs were (and still often are) truly awful.
Now here's where it gets interesting.
Rather than sound quality, some manufacturers realised that sound output (in volume) could be a selling factor above sound quality.
Amongst these of course were the manufacturers who didn’t have the best sound quality gear, and generally produced components that produced poor frequency response characteristics at low to medium volume and heaps of harmonic distortion when turned up, and so almost universally could only claim a lower rating for their products if required to specify Watts RMS.. Furthermore, for the manufacturers of better gear, as portable personal radio cassette players became popular, smaller speakers meant lower sound quality due to the speaker driver technology of the time.
Soooo, the manufacturers came up with a thing called Watts (PMPO). Watts PMPO means ("Peak Music Power Output") - that is, quite, literally, the loudest squawk the device can possibly make, at the loudest frequency it happens to produce turned up full bore with the highest input possible even if it just bout melts (or does melt) in the process. This is the Watts PMPO rating. Its not a sound that one would recognise as music, but usually is a speaker distorting so bad that a rock music song/program would only be distinguishable by the drum beat, vague voice, and lots of GGRRRRGGGH.
We’ve all heard cheap radio cassette turned up full bore playing bad sound, - take an 80's radio cassette/ghetto blaster (that probably says 40, 60 or 80 Watts on it, and turn it up all the way. When it begins to distort its beyond its RMS level, but not close to its PMPO, turn it up ll the wy, its loud but not listenble, - now imagine you can turn it up further till the speakers actually blow up - imagine how much worse the sound quality would be. That moment just before it blew up would be the units PPO (peak power output measured in an un listenable volume of “Watts”). Watts PMPO is somewhere between tuned up all they way and where it could technically be further overdriven to its PPO.
Because of this its very hard to verify or test a PMPO rating, and its so silly, not many reviewers bothered, it was junk stuff.
However, the Watts PMPO rating now allowed cheaper brands to start putting stickers on their equipment that said they were "60 Watts" or "80Watts" or "120Watts” etc when they were closer to 8-12 Watts RMS
In reality, a medium 80's radio cassette produces about 4 to 8 Watts RMS, and the best "ghetto blasters" round 15 -18 Watts RMS. An average home stereo at the time, anything from 20-40 Watts RMS, and a good one about 60 W RMS.
By the 90's, if you had $3000 bucks and could buy the Yamaha amp with Bose speakers you would get 120W RMS. This would seriously annoy your neighbors unless they agreed with your music choice, at full crank, 120W RMS in the lounge room will shake every room in a modern Australian 4 bedroom house, and you'll have your hands over your ears and they will still hurt to get close enough to turn it off. (Only try it if you think your speakers can handle it.)
For any who don’t believe me, the last gig I played at the ANU Bar we had 2 x 250W RMS amp (500 W RMS) - it filled the Sports Bar at ANU, rattled the windows and didn’t run close to peak.
Cheaper brands "PYE" (was amongst the worst) jumped on the PMPO band wagon to flog crap stereo systems to the masses shamelessly, they put stickers on the same model stereos that were previously rated t 14W, and promoted the new models as 60W, but it was the same electronics with different face plate. No reputable sound laboratory was ever gonn bother testing this gear, and so they got way with it.
The manufacturers of better stuff that you’d see in your department store side by side with this gear (Big brands like Akai, Marantz, (aka Phillips) Technics, (aka Panasonic) Sony, Toshiba were quickly forced to join in, and advertise PMPO ratings for their components (even though they were meaningless figures in terms of performance).
This is because the bulk of customers would buy the stereo that said it had the biggest "Watts”. No customer was interested in Watts RMS, that was boring, no sales person would show it either, they were (generally) only round 25W RMS, this confused the customer, who wanted the unit that said 150W!!!.
The more important performance rating is Watts RMS over Frequency Response.
Frequency Response figures provide the output (or for a microphone, input) level of an audio deice over the entire human hearing range at given rating in Watts RMS - however, the bigger manufacturers decided this was too complicated for the average buyer, and overall, their gear naturally had a better PMPO rating then the cheaper stuff anyway. So they joined the circus and the bogus and totally meaningless standard of Watts (PMPO) became accepted.
It means as little today in terms of how loud an amplifier is, or how it will sound, as it did then.
So how does this relate to car sound? - Well, the the first thing Watts aint Watts. This is actually really important, particularly for car audio. All decent audio components need to have thing called "headroom", that is; in order to sound good, they need to be able to comfortably reproduce any given frequency between 20 Hz and 20 kHz (human hearing range) without distortion t the required volume. This is arguably more important in car stereo because, the sound has to not tire the driver, (your ears will try and compensate, this uses up thinking power and human energy) and has to overcome the road noise etc.
Headroom is provided by having surplus power avail by the components to combat difficult to reproduce sections of the music with accuracy (perhaps the high ht in "Thunderstruck" , or... if you re so inclined... Dame Kiri Te Kanawa, or even, just the full range of the piano in Flametrees, or, anything for that matter.
By having q bigger output capability, the components will sound better when used at only part of that total ability.,
This is why an 80's boom box sounds way better when its only tune bout 1/2 to 2/3 of the way up. t bout that level it is close to the top of its RMS capacity, but it has just enough more to stretch that the odd frequency here and there beyond it doesn’t sound too bad - the mp and speakers can nearly reproduce it, and your ears do the rest of the work
So ideally, you want really big system, and only run it to half volume. This way the system can comfortably reproduce all the frequencies and the harmonics need not to make it sound like a tiresome blast of metal distortion, and instead give you whatever program you chose from Hendrix to Rage Against the Machine to Dire Straits and make AC/DC sound so good your mates just look at you in awe.
But, you want that headroom in Watts RMS – and 120W RMS is genuinely available, and its more than enough , but my best advice, really, don’t believe whats written on any amp, unless the manufacturer also states the RMS figure on the box in the specs.
And these days they’ve got outrageous. I saw one the other day 3000W?? yes they all say it now cause they have to 3000 W yeah right!!!.
I'd like to see a genuine 3000W RMS sound system in a car, I reckon, if you closed the doors and windows and turned it ll the way up it could smash its glass. But of course, if you do that, you put it in the tray, it's quite possible, but a little pointless! 120 to 200 W RMS is more than plenty.
(... It does also happen that I do have a heap of HUGE brand new subs and amps to sell, but that has nothing to do with this post, really, I promise, and I’ll chuck in these bathroom scales…. Lol).
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