Dear rotary and music friends.

I'm a German guy who was reading your postings very interested.
I only had an account to RX-7 Forum, so I decided to join the party. :-)
PLS TAKE YOUR TIME READING THE LONG FOLLOWING "NOVEL", IT'S WORTH THE TIME.

I did not hear a RX-8 sound system cos the RX-8 is not available here so far.
You guys are ordering the car like lunatics, so we have to wait. ;-)
I saw it first time on the IAA in Fankfurt last week. Great car.

Being rotary lunatic (owning FD), liking listening to good music and adicted to technical stuffs, this is the right forum for me I guess. ;-)
I will try to learn from you about the RX-8's factory systems. Together we can begin to improve the system if necessary.
I did not change the factory speaker setup in the RX-7 cos the German one is damn rare (around 100) and I want to leave it stock.
But I think the RX-8 will not be that kind of "collectible" and so hey, why don't do some custom stereo?!
I do work at a German car audio magazine as a sideline, so I think we will have some fun here. :-)

First of all, I think the Bose system could sound quite well and most of the "average" listeners seem to prove that.
The 9 inch doorsubs should produce enough bass for most of us. Well, I will have to hear myself.
The only bad think imo is that Bose again did not give us "real" tweeters. I would say the 2" speakers are good for frequencies upto 10kHz.
So I may miss the "magic" that higher frequencies add to the music.

Bose systems are not easy to modify/upgrade cos each component is setup with the others.
The speakers usually have low impedances to reach max output of the amps. And Bose uses (usually well done) equalization to eliminate the special car acoustics and to improve the standard quality speakers.
So any afermarket speaker will not fit the installation.
My personal opinion regarding Bose systems is: Leave it stock or throw anything out.

Well, adding subs with external amps might be a problem. How does Audiopilot react? Is the speaker were I get the high level signal time delayed or equalized?
Changing speakers is different as we do not know the impedance (it is not the same like dc resistance!). And remember the equalizing thing! Most important the spl of each speaker fits the others.
If you miss the magic I told above, I would recommend using a additional 1" tweeter left and right door.
Put it in the panel where the 2"s are living, I think it's big enough there. Just use a 3,3 yF cap to make him play over 10k (if 4 Ohms speaker).
That might work. Not sure about equalizing or Audiopilot. Just be sure that the spl level of the 1" tweeters fit the other speakers. You could use resistors to make it softer, but can't do anything to make it play louder. ;-)
Ah, not to forget, changing the simple 22yF cap will improve the 2"'s sound quality. Just use one with higher quality (foil cap), but these will get damn big.
So just wire a small high quality cap parallel to the big stock one, that works as well. Maybe 2,2 yF?

Step two would be to make your own custom stereo. Well, I think we can keep the headunit and the features like fantastic style integration, display and steering wheel switches.
Bose amps usually have high-power inputs to be able to use the same headunit like the non-Bose systems do. At least the 3rd gen. RX-7 did so.
We just need a high fidelity high/low converter. We did test one recently and it had impressive mesurements. -1 dB at 20 Hz and -2dB at 20 kHz. Wow, that should do fine for us.
It's about 150 USD, but most cheap adapters are just yuk.
Of course it is possible to replace the whole headunit thing, but lots of work and no display or remote control any more.

The frequency measurement was good work. But I have to say that frequency mesurements in car are damn tricky. You cannot just put a micro in the car.
We do use an average of 100 single mesurements (the PC does of course) to get a fitting frequency curve. Turning the mike around our head from one ear to the other.
And I have to say that the bass boost is badly needed in the car. That is because of the car acoustic, quite complicated. Maybe I will try to explain later, but I fear my English is not good enough.
Depending on the car size, we need a bass boost of about 10..14 dB starting slowly at about 250 Hz. Smaller cars need more boost, vans work fine with 10 dB.
And to compensate driving noise (hey, Audiopilot? ;->), we even need some more dBs.
And the highs should play a bit softer starting from about 8k downto -6dB at 20k.

Also the AUX-In was good job. I just don't like the thing with extra cassette unit.
If we knew the pinout and signals of the connectors, should be possible as well easier.
I don't think they used digital signals to sitch the decks, just different lines turned on/off.
We just need to know HOW...

So you see, lots of things to take care of, even many more than I did mention.

Some things that come to my mind and I want to know:

- were is the Audiopilot function integrated? The headunit? The overview says it's in the 5-ch-amp. How about the fronts then?
- impedances of speakers?
- time delay?
- speaker equalization? in amps? or headunit!?!
- frequency range of speakers and place of dividing networks? only the tweeter caps?
- what equalizer possiblities in headunit or just bass/treble?
- any low-level outs? I guess no.
- PLS post scans of the headunit connectors and what they are for!!! You should find in factory workshop manual from Mazda garage.
- Also PLS post the system specifications and the COMPLETE wiring overview.
- do the 9" have enclosures or use whole door space?
- does the headunit show CD-Text?
- ....

All of that will help us to find a way how to start serious high fidelity. ;-)

The following picture is my first contribution to this great audio forum.
It shows what components are used in the Bose system.
I think not all of you were sure what's behind the covers.



So just slow down running a bit before we know exactly where to go. ;-)

rgds
Tobi :-)

 

Thanks for the post - really interesting...

I'm convinced my concerns are about the high frequencies... and following from spin9k's mods, I'm keen to know exactly the right plan to add a tweeter.

- What frequency range are we after (you suggest 10K+) ?
- How do we hook it up ?

 

If I do anything to the sound system, it'll probably be adding a self contained sub unit and a pair of tweeters mounted in the footwells and aimed at my head..

I've done this before in a convertible and it made a world of difference.

Trick is getting a line signal and not robbing it too much.

 

Thanks for all of the good info RX-8-Tobi. I think you managed to grab our attention with your insights. I've also attached the back page of the BOSE handout that truly highlights what you are saying about equalization.

I'm planning on installing an 8" sub in the trunk and possibly some tweeters either in the enclosure with the existing ones, or pointing towards the windshield. I'm letting the custom audio shop look into this.

I am a little worried about the AudioPilot response though. I know...TURN IT OFF is an option, but I'd still like to use it.

 

great pic
I never saw that layout before

 

It's also in our Canadian books that Mazda sent us.

 

(get ready for some more pix, fellas! )

Additional tweeter thoughts

How to reduce spl level:





Note (basics):

We can only just hear 1dB differences.

+3dB is twice the power
+10dB is 10 times the power
+20dB is 100 times the power

+10dB "seems" as about twice the volume to our ears!!
Same speaker "plays" with 100 watts only 4 times louder than with 1 watt, not 100 times!!!


How to make dividing network:



To make things easy, -6dB/oct. should be ok.
I don't know how high the Bose 2" play, but usually they should say goodbye at around 10kHz.
As -6dB/oct. is not a "sharp" crossover, we might try 3,3 or 2,7 uF (if 4 ohm speaker).
A 19mm (<1") tweeter works fine. No need to play downto 1k, right!?
I do not know whether the equalizing makes the Bose tweeters play 10-20k. Might be.
In that case with our hook-up-tweeters it will be agressive I fear.
A small low pass air coil for the Bose tweeter could work to keep high frequencies away from the Boses.
"Real" tweeters handle those frequencies much better than the "forced" big mammas.
But don't ask me how the EQ or AudioPilot handle this modification!


How to hook up all the ****:



Just connect the small tweeter parallel to the Bose one.
Cap size has to be tried out as well as the volume reducing resistor circuity.
Pls refer to the tables above.
Also try out the best sounding polarity of the add-on-wiring. The Bose tweeter and the smaller add-on have to play in phase at the crossover point.
If 180 degrees out of phase, they will eliminate each other in the crossover frequency range!
The additonal parallel cap in the Bose tweeter wire is to improve sound/the low quality big 22 uF cap.



Additional information about frequency response in cars:

As I told you, the reference spl curve in cars in not just a flat line.
Smaller cars maybe upto 14 dB.
And when driving you may even need some more bassboost because of the drivimg noise, depending on the volume you are hearing.
To be still clear, the bass needs to be 10..20 dB louder than the surrounding driving noise.
Please see here how it should be.



Chart above shows a car audio installation (not mine!) with some peaks.
Bottom one is after I used the simple headunit EQ after some measurement/setting procedures. Maybe 20 minutes.
It's not perfect, but it sounded galaxies better than before.

How the car affects the bass reproduction.



This shows the spl of same woofer at 1 watt/1 meter. In free field measure room and in car trunk.
See what happens in the car. The woofer will sound much louder at low frequencies and more soft at highs in the car (bottom grafic).
That's the main reason why we need the +10...14 bass boost.
It plays much louder, but we don't feel it that much louder.
Smaller cars add more bass in general, that is why we need more bass here (+14dB).
Bigger cars (e.g. vans) add less and what is bad, the curve usually is more "twisting".


@ Bulldog6670: Thank you for the Bose handout.

@ Kev: The footweel is a damn bad place for tweeters. Was usual about 15 year ago cos we had no time delay.
With the installation you get the smallest way difference between the left/right side cos thex are so far away. But that is the only advantage.
Today we do use time delay or center speaker not to make the sound "glue" on the nearest speaker.
With the footwell tweeter you get very strange frequency response. And what is worse, sound changes extremly with or without passenger.
And with tweeters down there and the Bose tweeters in the "mirror triangle" (how do you us boys call that place?) you fail very badly the theoretical optimum of one-point sound source.


rgds
Tobi

 

Sorry guys, I am getting older...

Here is one way how you could install the extra tweeters:



Sorry, only Photoshop fake! :P

Tobi

 

CAN NOT FIND THE 2 INCH MID HIGH RANGE SPEAKERS

 

Nice Photoshop but make sure you state it.

-Mr. Wigggles

 

Hi guys!

Holy ****, that's one damn old thread. ;-)

Sorry for my bad English, but what does "state" mean in the sentence above?

Here you can see some baby coaxial speakers. I am sure lots of you boys would like to have for your RX-8s. ;-)


Surrounded by a Matchbox-size RX-8 to see dimensions.

Sorry, I do not know much about it. I once got the chance to get them for free and I thought: why not, you never now.
They have about 2 inch diameter, the tweeter has its own wiring! So it could be powered totally active. Maybe the "big" one from 500 Hz and then the tweeter from 5k.

If anyone might be interested, maybe he can find further information anyhow in the internet.

rgds
Tobi