Hey Everyone,

I'm planning on upgrading my soundsystem in my '10 MCS. I've been doing some online research (as I'm new to the scene) and I think I've got a lot of the basics. I have some more specific questions though that I'm hoping you might be able to help me with.

So ideally I'd like to upgrade all 6 of my speakers, according to another thread that would be these:

6 loudspeakers
• 2 mid-range loudspeakers in front, 100 mm [~4 inch]
• 2 bass loudspeakers in front, 150 mm [~6 inch]
• 2 bass loudspeakers in rear, 6 x 9"

And I'd like to add a 10" sub in the trunk. I'be been looking at amps and am leaning toward a 5 channel amp to take care of the speakers and sub. It sounds like it's definitely possible to drive those 6 speakers off of 4 channels, but I'm wondering how feasible it is (in terms of audio quality, how much strain it will put on my car, how easy it will be to setup for a noob, etc.).

I remember reading about the integral audio setup and I think the soundstage system actually leaves the rear 6x9's alone, claiming that the affect upgrading them would have on the system would be minimal - is this really the case? If so, would it be an OK idea (sound wise) to run my 4 front speakers (in the doors) off of the amp (1 channel per speaker), leave the 6x9's powered by the head unit, and power the sub with the 5th channel of the amp? If this sounds like a good idea I might be leaning towards it just to keep all the wiring as simple as possible. Or, is running all 6 off of 4 channels a trivial task and I should just do that?

One other thing, can you mix impedances? Like if I have 4 speakers that are 4 ohms each (each with own channel) and a sub that is 2 ohms, and an amp that can handle 2 ohms, will they all play well together?

Thanks in advance!

Brian

 

Brian,


Some thoughts:


You'll want to source your signal from the factory head unit (on the non HK system) from the front outputs. The front channels do not have the severe 70 hertz notch filter in place like the rear output channels do.


Check with the manufacturer of the power amp that you wish to use to insure the 5th channel will operate with a 2 ohm load. Your thoughts of running the 4 channels with a 4 ohm load and the 5th mono channel with a 2 ohm load is not unusual and I would suspect most modern, decent quality amplifiers will handle this load arrangement with ease.


Many systems are set up for front stage with rear fill. Hence some system designers not putting much effort (i.e. power and/or speaker quality) in the rear stage since it's just used to fill or add presence. The front stage typically gets the good components and high power since many people wish to listen to their system with a solid front stage similar to how you would listen to music in a home system or at a live concert with the music in front of you.


Depending on what components you choose, it may not make much sense to use 4 channels of amplification on the four drivers in the front door unless you are running some very high end components that allow for bi-amping. As we know, low frequencies take the most power to reproduce. High frequencies take quite a bit less at similar output levels. The two channels from a typical 4 channel amp that would run the mid/high frequency drivers in the doors would basically idle as compared to the two channels that would be assigned to the front door woofers. Better to run all four door speakers with two channels and the associated crossovers and save the other two channels of your amp for rear fill or even bridged to run a mono sub (and maybe only have the need for a 4 channel amp vs. a 5 channel).


I've pondered the following: There is a decent amount of cone area in the stock Mini setup with the ~160mm (about 6.5") front drivers in the lower doors and the 6x9 set in the rear. It would be interesting to use the 6x9's as subs with them crossed over low and with big power behind them (and of course feeding the front stage with good power as well). I've done this in several other German cars with the stock drivers (meaning I've re-powered the entire system and changed some of the low frequency crossover points to clean up the low frequency drivers) with surprising results. I have a feeling the Germans have speakers decently designed into their housings (i.e. air volumes, driver orientation, etc.), but as it sits, it's lacking in power. With all that cone area, one may find themselves with decent bass output without having to take up valuable trunk space in these small cars with a sub cabinet. A nice high power 4 channel amp repowering the entire system with the rear 6x9's crossed over very low might be surprising...and relatively easy to accomplish. Others should feel free to shoot holes in my theory...


Good luck,


Jay

 

Hey Jay, Thanks a lot for the reply and the info.

So the channel assignment issue I think is my main concern. I think it may be reasonable to do the front 4 speakers off of two channels, and the sub on the remaininag two, but then should I just leave the 6x9's alone? Or upgrade them and just run them off the head unit?

What I was thinking with the 5 channel system is that I might do the 4 front door speakers off of 2 channels, the two 6x9's in the back seat off of another two channels, and finally the sub off of the fifth channel.

But in the case of a more powerful 4 channel amp, it would be nice to bridge two channels and control the sub with that. And maybe I only choose 4 of the 6 existing speakers to run off of the remaining two channels. But then the question is, are the 6x9's really the best of the three types to sacrifice? And if I choose to run them off the head unit, should I even bother upgrading them at all?

I've been looking at crutchfield and I notice they say that the 4" speakers wont fit in my car. I've heard others say this as well. Is there a certain type I can find that will fit? Preferably without modification (making a simple adapter would be fine, just no alterations to the door).

Edit: Also, I've noticed that when other people do these installs, they usually have to make some sort of adapter to fit these aftermarket speakers on the mounts in the door. I'm curious, has anyone uploaded specs on this adapter? If I'm going to need them I'd like to do it cleanly and lasercut them. Or just purchase some online. Are there places that sell these specifically for the r56?

Thanks again for your help.

Brian Harms

 

Jay,

There are no holes in the theory - that part is totally sound (pun intended!). I've posted re: this before; the issue is in the practical implementation. For proper subwoofer performance you need to consider or control three primary things: the internal volume of the vehicle (determines corner frequency and slope), the internal volume of the enclosure, and the parameters of the speaker itself. Each one has a direct impact on the finished system. In this case, the first two are fixed, and unless you have the ability to build your own speakers like we do, you have very limited selection on the third. Because the first two (vehicle volume and enclosure volume) are fixed, you need a specific speaker, and it doesn't exist commercially. You could use DSP to correct the response, but with any of the commercially available suitable 6x9's (a shrinking list, b/c the physics make it hard relative to a larger driver) you start burning up a lot of amp headroom and bumping into both thermal and displacement limits of the driver**. There are other considerations as well, but the picture doesn't get any better.

At the end of the day, with the two 6x9 setup you're always playing catch-up with a 10" sub in a proper enclosure. If you can come up with an elegant solution to the enclosure (I believe we did, but of course I'm biased!), you get better results while keeping overall cost and installation time much lower.

We're working on a DSP box and 7/9/11 channel amp now, and even with that capability already going into the vehicle I'd still chose the 10" in the separate enclosure.

**Think about the relatively high Qtc response curve of a typcial 6x9 in a something like the OEM space. You could easily have a response that is down 10dB or more at 50Hz (where you still aren't getting much cabin gain). The boost required to get to flat response would be 10 times the amp power at 50Hz (at 10dB down), or 100 times if it were down 20dB. You can quickly see how you can run out of amplifier voltage or cook a voice coil.

 

Roll windows down...