Stereo System Options

[Dr.Jeff]

The unit shown in the "Ebay link" (SWM-80A) is rather interesting. It claims a power output of 4 x 60 watts using a TDA7388 amplifier module. Looking at the TDA7388 data sheet, the minimum guaranteed maximum output per channel when driven with a square wave is 37 watts. If you actually want to listen to audio, you can get 22 watts per channel at 10% harmonic distortion (not good). If you want it to sound decent, you can get 0.15% harmonic distortion at 4 watts per channel. So, the 240 watts ends up at 16 watts if you want good sound.

I've never fully understood how amps are rated and how to know exactly what you are getting. Most seem to claim a lot more than I believe to be true. And as you say the quality of the sound is definitely a factor. However for the most part if you are driving one pair of quality 4 Ohm speakers at reasonable levels, and it is mostly background music in a car (not exactly high fidelity), I don't think a ton of power is needed. But I don't know how exactly to gauge that. Like @LarryC alluded to, the X isn't necessarily a vehicle where I'd try to create a audiophile level system.

EDIT: I realize I might not have been clear in the above comments. I understand some basic principles of a sound system. But when it comes to knowing just how much power (amp output) is really needed, and more importantly how to gauge the manufacturers' ratings of amps, I'm not sure.

 

[Dr.Jeff]

Ebay link

You can use a micro SD card up to 32G, so that would work for your music collection...

Another with back up camera option - clean looking interface also

Thanks for the link. I'll have to look into it more.
When I first saw the pics of it in your earlier post (#70) I thought this was smaller than a full DIN size. The proportions appeared a little deceiving until I saw the specs and a pic of it installed in a dash.

The basic music players that I tried a couple of years ago were about a quarter that size. So they were not intended to fit a normal DIN opening, but more of a add-on unit. And that is a consideration for me, where I mount it.
1) If I decide to mount something in the stock (DIN) location on the dash then I'd prefer something rather "period correct" looking. Perhaps along the lines of a true vintage radio with a modern conversion internally. Or maybe one of the ones discussed earlier by @KBabcock or @LarryC.
2) If I decide to mount one in the glovebox then I'd prefer one as small as possible. However the appearance would not matter much in that case.
3) If I decide to mount a "hidden" unit completely behind the dash then I guess it really wouldn't matter. Other than the fact there isn't much room behind the X's dash, so I guess the smaller the better.

 

[KBabcock]

I've never fully understood how amps are rated and how to know exactly what you are getting. Most seem to claim a lot more than I believe to be true. And as you say the quality of the sound is definitely a factor. However for the most part if you are driving one pair of quality 4 Ohm speakers at reasonable levels, and it is mostly background music in a car (not exactly high fidelity), I don't think a ton of power is needed. But I don't know how exactly to gauge that. Like @LarryC alluded to, the X isn't necessarily a vehicle where I'd try to create a audiophile level system.

I spoke to a professional audio installer once and he said the one factor that his customers related to good sound quality was volume and amps allow you to up the volume without distortion. In the kingdom of audiophiles most us are peasants and don't know the finer points, myself included.

I would not call our X's amphitheater design sound environment with the top off and engine being thrashed 6" behind me. I just want decent sound for longer rides reliasing the poor stereo will be fighting my engine for my ear time.

 

[Dr.Jeff]

I spoke to a professional audio installer once and he said the one factor that his customers related to good sound quality was volume and amps allow you to up the volume without distortion. In the kingdom of audiophiles most us are peasants and don't know the finer points, myself included.

I would not call our X's amphitheater design sound environment with the top off and engine being thrashed 6" behind me. I just want decent sound for longer rides releasing the poor stereo will be fighting my engine for my ear time.

My guy says when he does a custom installation he sets up the system and adjusts everything for optimum sound quality and a flat response before it leaves his shop. But when the vehicle returns for any reason he always finds the owner has reset things for lots of bass and treble, to a "U" shape curve of sound. And as you say, they always want it louder.

 

[Dr.Jeff]

On the general subject of sound quality. With my preference of music I really like a strong bass, although I find many of the subwoofers (for cars) do not sound right to me. Over the years I've played with numerous different sub set ups in my vehicles and have learned that bigger is not better. And it certainly seems to have gotten out if hand these days. There are cars in my neighborhood that literally shake the house as they approach and drive by. I can feel them coming from a few blocks away. I guess I'm getting old because I cannot imagine how it must sound inside those cars.

As overall stereo technology gets better (especially for speakers) and sound quality improves I find it is possible to get a good bass response without the need for a dedicated subwoofer. Particularly in my vintage cars with less than optimal acoustics, as has been said by others. I think a lot of it has to do with the installation as much as the equipment.

 

[Bjorn Nilson]

But when the vehicle returns for any reason he always finds the owner has reset things for lots of bass and treble, to a "U" shape curve of sound.

There's a good reason for that because the road noise and engine noise are in the low and high-frequency range. You will always hear the midrange frequencies thru the noise but the low and high ranges need compensation. Flat curve is for quiet living rooms.

 

[Dr.Jeff]

There's a good reason for that because the road noise and engine noise are in the low and high-frequency range. You will always hear the midrange frequencies thru the noise but the low and high ranges need compensation. Flat curve is for quiet living rooms.

Excellent point, I never thought of it that way. However it seems many people like that "U" curve on their home systems as well. So maybe there's a general preference for hearing more toward the ends of the spectrum? Personally I tend to like more low and mid range and not a lot of treble. But that may have a lot to do with the type of music I listen to.

 

[Bjorn Nilson]

There's another factor involved as well called loudness. Low and high frequencies can appear less noticeable at low volume (especially in a noisy environment). But they will be much more noticeable when playing loud. On (old) stereo systems the Loudness function/push button was quite common. It boosted high/low freqs when playing at low volume but flatted the frequencies when the volume was raised.

 

[dllubin]

There's another factor involved as well called loudness. Low and high frequencies can appear less noticeable at low volume (especially in a noisy environment). But they will be much more noticeable when playing loud. On (old) stereo systems the Loudness function/push button was quite common. It boosted high/low freqs when playing at low volume but flatted the frequencies when the volume was raised.

Yes, the old Fletcher - Munson curve.

 

[LarryC]

Regarding power levels needed for good sound, I have always been suspicious. The wife's father was an audio engineer at a major radio and did lots of audio recording. He use to laugh at claims of the need for "200 Watts" and the like for "real" sound and was always ready to give a demo of good sound coming out of a good set of speakers regardless of the power input. So I figure reasonable power plus good to very good (=expensive) speakers and you are good to go.

 

[Dr.Jeff]

Regarding power levels needed for good sound, I have always been suspicious. The wife's father was an audio engineer at a major radio and did lots of audio recording. He use to laugh at claims of the need for "200 Watts" and the like for "real" sound and was always ready to give a demo of good sound coming out of a good set of speakers regardless of the power input. So I figure reasonable power plus good to very good (=expensive) speakers and you are good to go.

I agree that the speakers are typically the biggest factor in sound quality. And in relation to loudness and the power levels needed, the speaker's resistance (e.g. 4 vs 8 ohm) also makes a huge difference.

 

[Dr.Jeff]

There's another factor involved as well called loudness. Low and high frequencies can appear less noticeable at low volume (especially in a noisy environment). But they will be much more noticeable when playing loud. On (old) stereo systems the Loudness function/push button was quite common. It boosted high/low freqs when playing at low volume but flatted the frequencies when the volume was raised.

Great point.

Do they still offer a "loudness" button? A always left mine turned 'on'. And with some units it seemed to have the same effect at higher volumes as with lower volumes. I suspected on those units it was merely a preset EQ curve that was constant.

And speaking of "EQ's", they were quite the fad in the 80's. Either as add-on units or built into the head unit. Even today's "modern" car stereos have a selection of pre-set EQ curves for various types of music. Often I don't particularly care for any of them and do my own setting adjustments.

In regard to loudness and volume, remember the amps with a dial that went to "11" instead of "10"?

 

[lookforjoe]

Great point.

In regard to loudness and volume, remember the amps with a dial that went to "11" instead of "10"?

Wasn't that just from "Spinal Tap" ?

 

[Dr.Jeff]

Wasn't that just from "Spinal Tap" ?

That's where it originated, but then some guitar amp manufacturers actually put that on their control panels as a sales gimmick.

 

[lookforjoe]

The Volvo amps are very compact - they are rated at 20W per channel, which should be more than enough for the X1/9

they use a 6 pin DIN - so I'll make an adaptor like this, just with male pins to go from the signal level head unit output to the Volvo amp. I have the 14pole female socket to make the amp feeds & output to the speakers

 

[LarryC]

Indeed, with good speakers, 20W per channel will be more than enough.

 

[Dr.Jeff]

This is a good example of what I was saying earlier regarding amp ratings. Several reputable manufacturers offer small amp units with ratings around 20+ Watts/channel and good specs (SNR, distortion, etc.). Another example like the Volvo items shown above is a Pioneer amp I have from the 80's. Similar specs and it has excellent sound, plenty of power for a pair of speakers, and extremely reliable despite a lot of abuse by me....all in a small package. By comparison, other makers claim hundreds of watts, outstanding specs, and build them in all manor of enclosures. However in reality they are terrible; lots of noise, distortion, short lived, etc. And unfortunately the price of an item no longer has anything to do with the quality of what you are buying....thanks to profit greed you do not necessarily get what you pay for. This makes it difficult - at least for me - to know what I'm looking at when it comes to electronics like car stereo amps. Especially when some of the brand names that were once well respected for making excellent products are now putting out low level junk.

 

[Bjorn Nilson]

Many manufacturers are not stating REAL/USEFUL power output. Most of the car audio industry use Peak watts rating which is bogus. RMS is the only serious power rating and is used in high quality and professional audio.
Car speaker specification is also a joke. A car speaker that claims to handle 100W probably do so at 1000Hz. But feed the same speaker with 100W 50Hz and it will blow up.
IMHO all car amplifiers from the 80s are crap as they didn't convert the 12V feed from the battery to a higher voltage. So at 4 Ohm speaker impedance the maximum (peak) power is about 30W or just 10-12W RMS. Modern car amplifiers convert 12V to maybe 50-100V and that's why they are able to produce hundreds of Watts (RMS).
So old car stereos may look nice but they do not play very good.

RMS and Peak Watts

RMS and Peak Watts: In the consumer electronics world, you will often hear about watts, power handling, and power output - techformusic

techformusic.co.uk

 

[Dr.Jeff]

Modern car amplifiers convert 12V to maybe 50-100V and that's why they are able to produce hundreds of Watts (RMS).

Most of the products I see actually state the RMS and peak. But I guess the thing I wonder is how to know if a particular amp is actually what they say? How can you tell if the voltage has been converted higher? How can you trust their claimed output? Most products do not give much detailed information about such things, other than some basic "claims".

By the way, is the fact the older amps did not up the voltage the reason they were so robust compared to modern ones?

 

[KBabcock]

This is a good example of what I was saying earlier regarding amp ratings. Several reputable manufacturers offer small amp units with ratings around 20+ Watts/channel and good specs (SNR, distortion, etc.). Another example like the Volvo items shown above is a Pioneer amp I have from the 80's. Similar specs and it has excellent sound, plenty of power for a pair of speakers, and extremely reliable despite a lot of abuse by me....all in a small package. By comparison, other makers claim hundreds of watts, outstanding specs, and build them in all manor of enclosures. However in reality they are terrible; lots of noise, distortion, short lived, etc. And unfortunately the price of an item no longer has anything to do with the quality of what you are buying....thanks to profit greed you do not necessarily get what you pay for. This makes it difficult - at least for me - to know what I'm looking at when it comes to electronics like car stereo amps. Especially when some of the brand names that were once well respected for making excellent products are now putting out low level junk.

I think the amps used in a car need to be of better qualify because they have to last, they might be under a 5 year warranty. Many after markets are not on the hook if their products fail prematurely so they can get away with the 90 day warranty and sub standard quality. China making most the products now puts a huge swing in quality and , as you pointed out, cost does not always equate to quality.

I find I depend more and more on users reviews (though you have to be careful here), experts who take the products apart and discuss the quality of the construction (in this case electrical engineers in the audio field) and real world testing from sites like "Project Farm".