Dunno, I still haven't worked out all the things on my single CD player that's been in my Pulsar for the last 5 or 6 years. I can't even work out how to set the programed stations yet.Originally Posted by damienengland
Dunno, I still haven't worked out all the things on my single CD player that's been in my Pulsar for the last 5 or 6 years. I can't even work out how to set the programed stations yet.
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).
Last edited by SLR_dave; 11-06-2014 at 09:03 AM.
Dave, awesome post. Like others, i took all day to get through this but you're bang on. I haven't studies sound engineering but have spent many years installing audio, including car stereo (Morley Hi-Fi and Micro Electronics), home theatre (electrical contractor with a West Coast Hi-Fi contract) and finally commercial sound systems in bars and clubs etc.
The keys to power are exactly as you said and i have always been told to work our the needs of a venue then double it so the amp racks are essentially idling when in use. A couple of notes i would add include checking out the given Total Harmonic Distortion (THD) specification vs RMS power and also remember the power supply is critical to the peak performance requirements we are seeking.
Have a look at the specs on this Alpine Mono Block amp as an example-
Specifications
CEA-2006 Power Rating (40hm @ 14.4V = 1%THD+N), S/N 80dBA (Ref. 1W into 4Ohm): 1000W x 1
RMS Power (at 14.4V THD+N,20Hz-200Hz)
Per channel into 2 ohms : 1000W x 1 (<=1%THD+N)
Per channel into 4 ohms : 1000W x 1 (<=1%THD+N)
Dimensions
Heat Sink (WxHxD) in: 10-1/8" x 7-9/16" x 2-7/16"
Heat Sink (WxHxD) mm: 257mm x 192mm x 62mm
Bass Engine®
Crossover Frequency : 50Hz-200Hz, -24dB oct (LP)
General
Input Sensitivity (For Rated Power): 0.1 V to 8.0V
Input Impedance: 10k Ohm
Power Requirements: 14.4V DC (11V to 16V)
Speaker Impedance: 4 or 2 ohm
Frequency Response: 20Hz-200Hz (20Hz/-3dB)
Signal to Noise (S/N): 110dBA (Reference to Rated Power)
- See more at: http://www.alpine.com.au/showItem.ph....HZlb9G1U.dpuf
A couple of the keys here are that the RMS rating is given for a consistent 14.4VDC supply with a 1% THD (plus noise) and the frequency response is only quoted at 200hZ maximum so i take it there is some fudge factor in this amps performance. Even so, i bet this amp does very well connected to a sub woofer!
Great example. For a premier manufacturer producing some of the best car audio this doesn’t make heaps of sense, when really it could be made very clear. And all manufacturers are doing it of course, the market requires it.
The specs you have quoted from this manufacturer are for one of their top notch, high performance single channel subwoofer amplifiers (some other manufacturers are calling these “monoblock” amplifiers).
Its actually designed to power a subwoofer only. (This is why the very limited 20Hz-200Hz) frequency range. Its mono, and will not be able to reproduce frequencies higher than 200hz with much volume or accuracy at all. This is because it is not intended too, its job is all in the sub frequency range. As you say, its most likely it would perform really decently in those ranges. (although for $800 just to power a subwoofer it would want to)!!
I noticed manufacturers using 14.4V as a standard quoted supply voltage a few years back, that seems fair enough to me actually, (they have to use something, and most cars will have around 14.5 avail when running) but yes I agree it may also allow them to tweek the final output specification upward depending on how they’re measuring it, but, theres other stuff in there too that is fairly meaningless.
For instance, it seems to be claiming 1000W RMS (including noise as you point out) going into 2 ohms, and also 1000W RMS (including noise) going into 4 ohms, (ok, assuming that its feasible that the electronics can do this at either 2 or 4 ohms... ), where is the explanation of exactly what it means. What are they actually saying? It’s a fairly important spec for sales.
Remembering that its only producing a very small amount of the audible frequency range (20-200Hz) and that it seems to have a “crossover” (probably a High Pass Filter – adjustable you’d hope at that price) that can operate at around 50Hz – again it doesn’t say if its fixed, or goes up, or down from 50Hz , which will further limit this very narrow frequency range, so, what frequencies will it actually be able to produce to provide its optimum “1000W RMS”?
…..1000 Watts of what exactly?.
If you think about it, its producing such a limited frequency range, that its performance is going to be closer to a version of Peak Music Power (perhaps continuous, and before distortion), but I don’t know if that (if thats what it is) should really be called 1000W RMS - but theres no way of knowing reading the specs, what is actually being described.
Now because its only a mono (one channel) amp, and the range is so low, and giving the manufacturer the benefit of the doubt lets assume it is able to produce, from an amplifier that size, some form of continuous bass frequency operating at 1000W. Lets imagine the current drain.
Power (Watts) = Volts (V) x Amps (A).
W/V = A
1000 / 14.4 = 69.4
Close enough to 70 Amps!
So , for the amplifier to produce the claimed 1000W of power, it would need to be able to draw 70 Amps or thereabouts continuous current draw from the battery or the charging system. .
The draw on the charging system would be unsustainable very quickly. And on top of that, you still need another amplifier around the same size to run the front channels. (so say 120 Amp current draw for both).
Now I’m not saying that this doesn’t happen, it can happen quite easily, a big amplifier and Sub set up installed improperly is easily likely to threaten a cars charging system, and, can (for instance) cause fires, stop the headlights, or windscreen wipers from working properly, etc it happens! Installation is a serious issue with big amps in cars, extra batteries, beefed up alternators, even an extra alternator in some cases may be needed or justified.
It is quite possible to achieve 1000W RMS in a car, (if one really wants it) but, it makes me think twice about whether a big brand would sell an amplifier that big on the net, it needs professional installation so in the back of my head I wonder, perhaps another discrepancy there.
So yep a good example. (And all the manufacturers are doing it). All that said however, I reckon, reading carefully, (guessing between the lines basically) specs like these can actually give you a vague idea of the capability of the unit in question because, you can judge how far the manufacturer is prepared to be caught out lying blatantly – some lower quality brands may not care, the better ones will care more, whilst these specification descriptions may not be at all clear, for the higher end manufacturers the gear still has to sound like it meets what those specifications may seem to claim, so with care you can still make a fairly informed choice.
This doesn't mean that the specifications given above can't be believed, its just that its not easily clear to see exactly what they are specifying.
They are after all a top brand, if you have their components and they are set up correctly its pretty hard to go wrong. This is perhaps why its a good example, they make great gear, you'd have to imagine its an excellent piece of equipment, but even their specs aren't clear about the RMS rating.
So coming to terms with the issue of volume and “Watts”/ "Watts RMS" not necessarily being what they say they are (and most often, many many miles apart) is really important in selecting car (or any) audio system. A more important specification for all amps, head units, and speakers is the Frequency Response figure, (distinct from frequency range) from this you can get an idea of overall sound quality produced by a component (as opposed to volume) but this is turning into another essay atm so maybe more a little later.
Last edited by SLR_dave; 13-06-2014 at 03:06 AM.
Dave, another great thesis and its awesome to see Ohms law getting a workout on MySandman. With reagrds to the current draw, i have seen this in action. I had a Sony X-Plod (1000W RMS branded) amp running two Alpine 12 inch subs some years ago and suffered several failed alternators in my VT 5lt common door. I connected an amp meter to the alternator wire and measured a max draw of 120A with everything on such as headlights, A/C, sound system up full etc etc. Its an area not many people think about.Power (Watts) = Volts (V) x Amps (A).
W/V = A
1000 / 14.4 = 69.4
Close enough to 70 Amps!
Nice novel Dave!
Normally if I want to read something that long I buy a book.
Good info though, if a little eye glazing for a forum.
Point gracefully accepted, however, perhaps spare a thought for me, (I entered the entire post without using an "a" key - I spilled beer in the keyboard). so, I was actually tryna save words (I had to cut and pste each "a" - and still am!)Nice novel Dave!
Normally if I want to read something that long I buy a book.
Good info though, if a little eye glazing for a forum.
Holy s*#t Dave, I had to make a cup of coffee before I sat down to read that. I still don't know how to program in radio stations.
Awesome post Dave. That would go a long way to explaining why the "150 Watt" 3way 6x9 Blaupunkt (spl?) speakers I put in the doors of my ute 10 years ago still seriously outperform the supposedly "bigger and better" ones I recently put in my daily commuter wagon, even though they are mounted correctly and have a similar sized void behind them. Both are just driven directly from the head unit and both head units are rated at the same output/channel.
Cheers.
Nunc est bibendum...
Very informative thread...top stuff guys
Now...can anyone recommend me some speakers that are able to handle metal music? I'm being brick walled every time i go to a car audio store and ask the same question. Usually met with a blank look or a stuttering response which indicates they have no freaking idea. A friend has an audi that has factory stock Bose speakers that sound great at mid volume levels, but farts out when the volume is cranked. At low and mid volume level its sounds great, but metal isnt meant to be listened to at acceptable levels.
Any help would be great
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