Help me understand what/where the kick panels are?
From the name I could hazard a guess but would rather know for sure

Is that really the case?

I was looking at the MB quart 268 (6x8) or the 216 (6.5)

Both use the exact same tweeter, the only difference as far as I can tell is the mid driver shape/size

MB Quart Car Audio -- Premium Speakers

 

I've never heard the 6x8 version of those, but I'm sure they are OK.

As far as the kick panel, I put my tweeters where my dash meets the panel next to your foot. Here's the theory on why. The higher the frequency of a sound, the more directional it is. (This is also the reason that you can put subs in the trunk and in a well balanced / crossed over stereo, you can't tell).

Now, Ideally you want the left and right speakers equal distances from your respective ears. Since you have to sit on one side of the car, this isn't practically possible. But in the S-Type, especially if you sit with the seat at all reclined, the drivers door speakers are REALLY close to you. So, due to that you try to space out the high pitched frequencies as best you can.

I'll try to attach this as an image, BUT it may make the thread huge, if it does, I'll resize it when I get home from work today.



Take care,

George

 

Hi George

Thanks. I was struggling to see what was going on in your pic until I realised that the wheel on your car is on the wrong side

Completely understand the theory.

In reality in most cars theres way too much diffusion and reflection going on to have any hope of a truly accurate soundstage, so we do the best we can. Conversely though, the Haas effect dictates that in such a confined space the reflected shouldnt adversely affect the perceived signal. It likely also reduces somewhat the importance of having both tweeters equidistant from your ears for most program material...when it comes to doing this I think I'll test some of this stuff out - Im used to optimizing my specially designed mastering room, not cars!

 

Reflection tends to be more audible in the higher frequencies due to the shorter wavelengths. For most music, the summation of frequencies give you an instantaneous frequency of about 4500hz. (dont forget that at ANY given millisecond - there can only be one frequency currently in the signal path). But with modern digital audio sources sampling at 44khz, the effect is minimized.

The biggest enemy to accurate soundstages in cars is the simple transfer function created by all of the various drivers firing into a relatively sealed cabin. In theory this could be considered a 2nd order enclosure where the front wave of the drivers is firing into an isobaric chamber. Regardless, there are certain things you can do to help.

Personally I like to keep the tweeters as low and as equidistant as possible. I don't want to be able to hear and isolate any particular driver with my ear. People who mount their tweeters behind the wing mirror (to use your across the pond terminology), especially with amplified component sets tend to have this problem... I've even heard a few brag about it as a "feature".

There tends to be somewhat of a midbass hump in the transfer function around 85hz in most cars. This can be compensated by setting a highpass frequency where the slopes cross there. +6db for the midbass, - 6db for the sub. Now a LOT of aftermarket amps have 12 or sometimes 24db / octave crossovers, so you may have to bring the x-over frequency of the sub up a bit to compensate.

Personally I'd take the tweeters, double side tape them into a couple places and have a good listen before deciding on a mounting location.

Take care,
George

 

Directionality of reflected signals is typically more audible, but higher freqiencies are typically absorbed more than lower frequencies, unless the material has acoustic properties designed to provide a different characteristic (for example in the studio we have absorbers specifically designed to be extremely efficient at absorbing frequencies below 250Hz, and at the same time reflect frequencies at arouynd 500Hz and above to avoid the room sounding dead.)

But my point about the Haas effect still applies here. reflections arriving less than 30ms after the direct signal are typically inperceivable as a separate signal from the direct (even when that reflected signal is up to 10dB louder than the direct) - thus we get the impression of width and depth rather than echo.
Due to the small distances involved in a car, this is typically always the case.
The same should apply to the sound from Left and Right speakers for mono sources.

Until you open the windows
Joking aside, yep, agreed. I would also imagine that the location of the sub plays a not insignificant role in determining the frequency response at a given listening position.
Given the size of most cabins, I guess this might start becoming an issue around 70 or 80 Hz.

Hmm indeed. I havent even looked at whats available, but in theory it should be possible to optimize the image in a given listening position (i.e. drivers position) by measurement and application of an appropriate delay to each driver.
Probably much further than most people want to go so I dont know if such a product would exist in the car audio market.

I think where that peak exists is very dependent on the size of the car, location of drivers etc, but 85Hz sounds about right for typical family sized saloons. Ive always found the most natural sounding crossovers in any application (be they speakers, or in a multiband compressor use 6dB/Octave slopes).
It happens that the monoblock I got uses a 24dB/Octave filter. They are a (fourth order) linkwitz-riley (Butterworth squared) filter. The Directed 200 amp uses second order L-R filters (12dB/Octave). As you say though, some experimientation and measurement at the main listening position (drivers seat) will determine the appropriate x-over points. Too many variables here to rely on theory.

Thats the plan yep, same with the sub (I would imagine SBIR will come into play)

Thanks again for the help George.

 

The issue is most of the surfaces in a car (besides the carpet anyway), tend to reflect rather than absorb. Hard plastics, glass etc.

There have been PLENTY of attempts at DSP in the mobile enviroment, both in emulating soundfields by adding echos or relfections, as well as attempting digital time alignment. I've played with a couple but the effects always seem to sound hollow or fake and overprocessed. The best example I can give you is is before and after running a track through a compressor for FM transmission.

Some examples:

Amazon.com: Pioneer DEQ-7600 DIN Digital Signal Processor and 15-Band Digital Graphic Equalizer: Electronics

Amazon.com: Alpine PXA-H701 - DSP: Electronics

As far as where the transfer function peaks, generally it's around 80-100hz, you really want to hear a dramatic difference (of removing the isobaric chamber), have a listen to my 500sl with the hardtop on, and listen to the same car with the convertible top down. It's hard to believe it's the same components.


I agree with you on the 6/db octave crossovers, as they roll off most gradually, however there are two reasons for the use of steeper crossovers in mobile applications. First electronic crossovers are capable of far steeper slopes, without multiple coil / capacitor networks. And technical specs always impress, secondly the sharp cutoff tends to hide the location of subs better, AND protect midbass drivers from hyperextension / distortion. As long as you know what you have you can tweak it to your liking, even sitting in the passenger's seat as you guys seem to do


The S-Type likes the cone of the woofer facing rearwards out of the trunk. The less airspace you have in front of the cone, the more likely you're going to have standing wave cancellation.

Take care,

George

 

Just to confirm, when I get into the doors, I don't have to run any crossovers, correct? The factory alpine setup has a set of wires for the woofer and a seperate set to go into the tweeter correct? Thanks for the help!

Also, any suggestions on getting off the trim piece around the inside door lever without breaking them? Also, is the stock alpine amp strong enough to push a nice set of component speakers or will I have to upgrade the amp too to see and hear results?

 

This is vehicle specific. If you are thinking putting in components vs coaxials will make any difference at all you are mistaken. There is no point in using a component setup if the tweeter is going to be mounted right next to the woofer as in the above picture. You just might as well go with a decent set of coaxiles which in essence is just a component system stuck together. The jaguar s type uses a 6.5 alpine coaxial for the alpine models. There is no point mounting a tweeter half an inch from the woofer , just go with a standard better quality coaxial.

 

there is no point going with components in a jag s type unless you are gonna custom mount the tweeter up higher. You will gain nothing if you are going to mount the tweeter right next to the midbass driver as done in the above pictures. Just go with a coaxile

 

ok I understand why the alpine system owners would want to use a component set up over a coax now. I didn't realize the factory alpine amp has separate crossed over leads to the speakers. I guess you kinda have to use a component system if you wanna replace them. I don't think anyone makes a coaxial with separate tweeter and midbass inputs.