In car Stereo

[Fabiaman]

To ALL ICE fans here including Barakian, Skodaman & Ghostrider, thought I bring up a new topic for further discussion. On of the things that I cannot understand until today is the stereo imaging in a car. I still do not understand how that is possible in an enclosed car with 1 speaker so close to you while the other is much further away.

 

Stereo sound is composed of identical sounds (mono) and differences. The blend produces images when the listener completes what is known as the stereo triangle . See diagram.

 

Pls find below a diagram of a normal set up in a Home Audiophile set up where the listener is sitted in front & between the Left & Right speakers. As experience which most of us will know , is that sitting a bit to left means that we will lose the stereo effect and instead hear the sounds more from the left speaker unless the right speaker reproduce something different from the left.

 

 

 

This is the stereo triangle and the distance indicated by the blue line between the 2 speakers must not be longer than the distance between the listener to the speakers as indicated by the 2 black lines.

[Fabiaman]

Due to the limitations of placement of speakers and the seating positions in car stereo, the " stereo triangle" and the stereo effect is not easily reproduced. Unless you consider removing the windshield and putting the speakers on the bonnet.

 

The distance to the listeners' ears is much shorter from one channel'

s speaker than the other channel' s. So instead of the mono sound arriving

at both ears from both speakers at the same time, it arrives at different

times preventing a center image. That is, the listener is out of acoustic

alignment....

Edited December 30, 2001 by Fabiaman

[Fabiaman]

In home audiophile, listeners attempt to make sure that the tweaker , where all higher frequency resonance & sounds are emitted, is on the same level as the listeners' ears. Reason being high frequency sounds are directional (ie. it travels in straight line). Unlike low frequencies which travel in almost all directions. Hence, we often see subwoofers at home tucked away at a corner and still able to hear its beautiful low groaning sounds.

 

In car stereo, I often do not see the tweaker aiming at the driver. Since its directional, the best position for it is to face the listener as I learn in home hi-fis. While most of the tweakers are at the neck/chin level of the driver, its pointing at whereever the location allows it to point to.

[Barakian]

Brudder, wah lieueh!! Diagram and all! Cool man!!

 

On to the topic of imaging. Agreed that in a car environment, the listener sits closer to one channel than the other. This cannot be avoided unfortunately, unless you are driving a McLaren F1 where you sit in the center.

 

The trick to achieve imaging is time alignment. With the use of electronic circuitry and time delay, the sound from one channel can be made to arrive later at the listener's position than the sound from the opposing channel.

 

Let's assume that the driver is the listener in question. Time alignment makes the sound from the channel nearest to him arrive later than the sound from the opposing channel by delaying the time it takes for the signal to reach the speakers nearest the driver. The delay may be in the order of a few hundred milliseconds, but it is long enough to be audible. It works on the same principle of PHYSICALLY shifting the speaker so that the listener is right smack dab in the centre of the sound stage.

 

By doing this, we are tricking the listener into believing that the sound is actually eminating from directly in front of him, or slightly offset to his right, right smack dab in the middle of the dash. Keeping this setting constant, if one were to sit in the front passenger's seat, the imaging would be totally off.

 

Now for a mathematical perspective. In home audio, we have the listener sitting in between 2 speakers. Say the distance from the listener to each speaker is X metres. Therefore, the time taken for sound to reach the listener's ear would be (X/330) seconds (assuming speed of sound = 330m/s and that the temperature of air remains a constant). Both channels of sound reach the listener at the same time, so centric imaging exists.

 

In car audio(for RHD cars), the listener sits closer to the RIGHT channel. Let's assume the distance between the RIGHT channel and the listener to be X metres. Therefore the distance between the LEFT channel and the listener would be (X + a) metres where a is the extra distance that the sound has to travel to reach the listener.

 

Under normal circumstances, the time taken for the sound from the LEFT channel to reach the listener will be greater than that from the RIGHT channel, i.e. [(X+a)/330] sec > (X/330) sec. With time alignment, electronics are employed to introduce a small time delay in the channel nearest the listener, in this case the RIGHT channel, so as to achieve centric imaging. So with time delay, the equation looks like [(X+a)/330] sec = [(x/330) + b] sec, where b is a small time delay introduced by electronics. Centric imaging can now exist.

 

Time alignment can also be used to center the image toward the front passenger, center the image ANYWHERE on the dash or provide a wide stage for ambient listening.

 

Speaker placement also plays a part. Unfortunately, speaker placement is not something I am familiar with, so can't say much here.

Edited December 30, 2001 by Barakian

[Spinner]

This is getting interesting. What Fabiaman is implying is that all these thousands that owners spend on improving the sound in a car is probably a waste since the set up constrain in the car hinders the proper sound reproduction? More , more more.... pls enlighten more since I am quite keen on upgrading the set up that I currently have (which is stock).

[Barakian]

I would not really say that the money spent on ICE goes to nought, although the interior of a car is generally not the best place to play audio. However, the money spent can make the install pretty credible although not home-audiophile standard as one has engine noise, aircon noise, road noise, horn noise, rain noise, etc to contend with in a car. It boils down to equipment matching, the installer's skill in installing and tuning, and the acoustic characteristic of the interior of the car itself.....

[Spinner]

Barakian, sounds like tons of variables to consider in getting a ICE set up. In your opinion, if I want to change my stock set up from scratch, abt how much is enough to make it a credible and value for money set up? I approach this audio shop in Joo Chiat (I think his name is Chris? Very muscular one) and he told me to spend $2,700 and that is it! Comments pls. Thanks!

[Barakian]

Time alignment is going to the higher reaches of ICE liaoz....people normally pay in excess of 4K for such a setup cuz the equipment used is not cheap.

 

For 2.7K, you should have a very decent setup indeed. I'm assuming that he intends to install component speakers up front, throw in an amp and possibly even a subwoofer or basstube with an amp to drive it. Mebbe got extras like a pre-amp. Can gimme the list of equipment that he quoted to install for you, as well as a list of your current stock system please? I can have a better idea from there...CHEERS!

[Spinner]

Tks Barakian, I am not familiar with what sort of components in the 2.7k. But definitely subs and amps in it (just not sure what type & what brand). I just remember he said the speaker is CDT...?

[Barakian]

CDT Cambria components? Quite good stuff ler...well, maybe you would like to have a chat with your installer and take down a list of equipment that he intends to install for you? Also you can ask him whether he intends to change your existing headunit (HU) or whether he intends to upgrade with your current HU intact.

[Spinner]

Tks Barakian, will ask him for a listing of the components.

Alternatively, that guy also told me to change just the front speakers if I am not keen on forking out 2.7k. So which set of front spkrs can I change to? Any recommendations? CDT?

[Barakian]

For front components, you can try CDT, Helix, Velocity...these 3 should be able to give you very decent performance at a bargain price. But then again, running comps without an amplifier is pretty much akin to running an S14 minus the turbo....try to include at least a 2-channel amplifier if your budget permits it, and run your rear speakers off of the HU.

[Skoda_Man]

Well already replied - Time Alignment for the imaging, not forgetting you need rear fill to complete the entire picture.

 

Also, there is a long discussion in ICE forum some time back about imaging and time alignment is the new tech, old tech uses different vloume control to 'trick' the ear to get the singer right in front of the driver. Very tough to get it right.

 

Time alignment stuff is not cheap my friend, you need powerful processor to get it done up cprrectly.

 

Just imgaine the price of these HU, Sony C90 + UC50 or 4000, Alpine F1 series, Pioneer P1, P9, and others. easily a few K an above.

 

Try to go to the ICE forum meet up and you can see those HU with Time alignment.. cool HU

[Ghostrider]

Kawan....dun really need the rear fills if your time aligment is setup proper....remember one meet we had at Fort Rd CP ?? (where you there ?). One Civic VTI-S had just a 12 inch sub boxed & front speakers....running on C90, the time aligment processor.....and some tube amps......very nice setup.....dun miss the rear fill much.....if you wan proof....call me...I arrange a audit for you !!

[Roadblock]

Okay, you spent thousands on time alignment, but that means the passenger beside you, ie. your gf or wife will suffer as well because to her, its a mono source since the left speaker will be faster than the right speaker right?

 

Considering the speed of sound of 331.45m/s and that the distance between speakers and listeners are well less than a metre, the timing alignment must be very precise then. Correct?

[Fabiaman]

Tks Barakian for that in depth analysis on getting imaging right for ICE. Yes, it does make sense that timing delay does help in creating that imaging effect.

 

Now we might want to address whether its worth the money spending on $4k plus on a set up with timing delay. Given that same amount at $4k, is it too much to spend given that its to rectify something as easily in home audiophile as sitting arrangement.

 

So how much is the timing delay equipment alone?

[Skoda_Man]

Dun want to audit..... think will sound funny... unless the C90 uses some DSP to create the sound way to make it sound like a complete setup.... but then I might be wrong....

 

sorry man, when it come to ICE, I have China Man illness, nothing beats more POWER and Speakers hor... and not forgetting that I love the warm sound of analogue, so TA is out for me..... :P

[Barakian]

Here's the nice thing about a processor equipped with time alignment and other such features.....your soundstage can be set such that you have ambient sound, meaning both the driver and passenger get to enjoy a wide sound stage. You can preset a few settings into your processor to cater to different situations where different imaging positions are required, such as when you are travelling alone, or travelling with gf, or making out in back seat, etc....

 

Agreed. Timing for alignment must be very precise due to te relatively short distances between speakers and listeners, as well as the high speed of sound.