Bigalfromfl

This is seriously great info!!!! Great thread!

chuck911

A couple points regarding impedance and power. Impedance with regard to speakers represents the load the speakers put on the amp. A low impedance load will take more current (which calls for the big fat wire mentioned earlier) and in general amps have a hard time delivering current. So if for example a Bose 2 ohm driver is replaced with an 8 ohm Burmester, the Bose amp will have an easier time driving that load. Other things being equal (which they never are, we're talking in principle here) this will be heard as an improvement in ease or dynamics, a clearer, less fatiguing (hard on the ears) sound. Because the amp draws less current it will also run cooler. This is much more a concern with woofers, as thats where all the power is anyway.

Bottom line, if the Bose drivers are low impedance you'll be fine. The amp is already designed for that load and will only sound better given an easier to drive higher impedance speaker. Going the other way, watch out.

Another thing, power. People buy amps the way they buy cameras, thinking more watts or megapixels is what matters. Well then we may as well admit defeat now, the corvette has more horsepower. In all three cases there's a lot more going on than a number. Take speaker sensitivity (dB output per watt) run the numbers, turns out even at high volume levels average power is very low. One measly watt in a car probably gets you a very satisfying 95 dB or more. An amp that sounds bad almost never does so for lack of power. One reason why Robert Harley famously said, "if the first watt isn't any good, why would you want 200 more of them?"

MJBird993

Like yourself Tony, I've had a Corvette or two (most recently, a C6 coupe). In that car, which was my DD at the time, I pulled out all of the carpet and put in two layers of CC foam, which did knock out a lot of resonance that you get with that big hatch area, and a bit of the tire noise. I really should do the same with the Porsche. Maybe when it gets warmer outside. No, I don't have a heated garage. I live in near poverty.

A few thoughts that I've had over all of these "Bose sucks" threads.

First, in the case of most cars but especially the Porsche, weight savings is a big deal. Would this not partly explain a lot of the cheap (lightweight) components that we see? Instead of a proper die-cast speaker frame firmly mounted in a particle board cabinet, we get plastic snapped into plastic. Instead of a massive amplifier with 10 lb. heat sinks, we have a small IC board that runs at 16 ohms. Not because they want to save money and want crappy sound, but to save weight.

Now, me personally, I'd pay the 50 lb. weight penalty for a decent stereo system, but I didn't see that option in the configurator.

Second, I concur that it only takes a fraction of a watt of power to drive typical speakers at decent sound levels. I was told that the extra 200 watts is for the peaks. That's where a decent amplifier outshines a cheap one - in the ability to quickly respond to peaks in the music. Otherwise, you end up with an FM radio-sounding compressed sound, or worse, the amp clips.

I remember back in high school when I bought a booster for my incredible aftermarket stereo system for my Pontiac. The booster had 10% THD (Total Harmonic Distortion). A typical amp in those days had 0.1% THD or better. I thought it was hilarious, mostly because, really, most people can't discern 10 or even 20% THD, or don't care. Hey, it was loud, and I was a teenager.

I think I digressed somewhere...

mtony

There are no rear fender liners!!!

wanderfalke

The big question is who will be the first to do a quick and dirty replacement of the speakers behind the door card without swapping out amps. ect? Chuck 911 seems to be saying it could be done without causing harm because of a different impedance .

lunarx

I think that would sound worse.
Bose speakers are efficient and optimized to their amps.
Any other speakers would be at a disadvantage.
In another car I tried aftermarket door speakers and wound up putting the bose door speakers back in.

The only speaker in the 991 door that looked a little more expensive was the Burmester Mid. Hard to say if it could net a gain, if swapped. Since its small and possibly efficient, it might.

We got lucky on the Tweeters, because the original was clearly sub-standard, so almost anything would be better. In addition the amp power was adequate, for an efficient AMT Driver. Perhaps other efficient high end tweeters would work just as well too.

As for the sub, I think just an amp could help, as the sloppy bass may be due to high THD in the amp.
If I can get the Burmester Sub fitted (with a new amp) I would expect huge gains in bass.

I think that is the only low hanging fruit. Other speaker swaps would require lots of electronics to supplement.

When I get home Ill post the pic of the Burmester center channel vs the bose.
I decided to leave the bose center in, because it is not doing anything wrong.

Here are pics of the Bose & Burmester Center Channel.
The Burmester is a lot heartier looking but guess which one has a plastic frame and which has the steel frame?
Burmester has a plastic frame, perhaps that is why its only $58 vs the $52 Bose speaker.

chuck911

Actually, pretty much all the same stuff happens in home gear where weight is not a factor. These things are all built to a price point, period. In the case of the car the only real factor is installation/assembly. That's why it's so easy to swap out drivers like lunarx did.

Particle board is super cheap. Most speakers use MDF. Which by the way is really not all that good a material. It does however have a very benign affect on sound, is easy to work, inexpensive, and veneers into anything. But all your really high end speakers are other materials. Anyway, MDF would never work in a car, where it would be exposed to and quickly ruined by moisture.

I first thought the tweeter mounted into the frame. But looking at lunarx's photo's again it looks like it screws into dash plastic. Vibration control in audio is huge. What you're really trying to do is precisely recreate sound waves using a driver to move the air. How's that supposed to work when the driver itself is moving around? Not well, that's how!

High power and low distortion are vastly overrated. Even my very good quality 200 watt McCormack DNA amp was easily outperformed by two different 60-watt tube amps with much higher distortion ratings. A lot of this has to do with the fact that just as all watts are not created equal, nor are all THD numbers.

There are for example even and odd order harmonics. Musical instruments naturally produce lots of even order harmonics. As do tube amps. Solid state components on the other hand produce more odd order harmonics. Guess what? People are FAR more sensitive to odd order harmonics. Makes sense, as basically the even order harmonics just blend in with the same harmonics naturally produced by instruments. THD numbers lump them all together. This is one reason why so many of the high power low THD amps of the past sound so awful.

77tony

Like yourself Tony, I've had a Corvette or two (most recently, a C6 coupe). In that car, which was my DD at the time, I pulled out all of the carpet and put in two layers of CC foam, which did knock out a lot of resonance that you get with that big hatch area, and a bit of the tire noise. I really should do the same with the Porsche. Maybe when it gets warmer outside. No, I don't have a heated garage. I live in near poverty.

Great info. Poverty eh

Good to know and in that case, need to have a better look both in & out. Maybe some insulated floor & tunnel wrap in the wheel wells and/or some closed cell foam in the interior is in order. This would add minimal weight and along with a new set of Michelins (when it's time) should quiet things down. Really like what lunarx has done here. Sounds like a winning combination without spending a lot of $$ T

lunarx

Nice to have this great commentary from the Audio Gurus, who posted here.

To answer some questions;

I updated the post w/ the new Grill Pics.I measured the DC Resistance (not impedance) of these speakers:
Regarding the Sub..More interesting is if GT3 owners can also install a sub.
If they chose to go further and put in all the Burmester speakers, they have plenty of space in the back seat area for an amp rack.

mtony

Could you verify the part # for the Burmester grills? Thanks! Great info!

LexVan

Great job! Wish I had the skilz and balz to attempt this. Maybe someday???

Probably one of the very first true "mods" done to a 991 on this board. Clear amber LED corner lights excluded.

Sent from my iPhone using Rennlist

lunarx

The part numbers above are right.
I attached a pic (below) of the grilles, that I ordered, with the Black Trim Code.
If you have a turbo or something, that might have other trim codes, than I showed, I can look it up for you.

The grilles came in from Germany, but with a very small fee they express shipped them.

Well, it's perhaps as "mandatory" as clear side markers

I don't think one can get a dealer to install the tweeters, with the connector being wrong and clips needing to be shaved.
However, perhaps asking them to remove the grills, and put them in a box for you, because you want to test some different tweeters may fly with them.
Another excuse is you want to upgrade to the leather wrapped grills

I suppose they would charge an hour of labor, if you did it at the same time as another paid service, like an oil change.

chuck911

Long as you're getting into this, a couple things about these drivers.

Metal is nice. But there are plastics, and there are plastics. Considering how much better Burmester sounds than Bose my bet is they're using something a lot better than it looks.

The rest of the driver sure looks like it. The cone is a composite, probably kevlar or carbon, where the Bose is paper. The dustcap also is better than used on the Bose. Ditto the surround. Bose looks like the same crappy foam used since like forever, that breaks up after 10-20 years. The voice coils seem to be about the same diameter, but you can tell from the side view the Burmester has greater throw length. The magnet is larger too. My bet is it sounds a LOT better than you'd guess based only on the difference in price.

Porsche_nuts

Great post lunarx. Thanks.

Question - wouldn't you be able to use the old grills. Seems as if you can with some modifications - i.e. removing the speaker and grinding some plastic off?

lunarx

Porsche_nuts,
The grilles are only $60 each and they have a bigger opening.
Plus, chuck911 would give you an earfull (refer to his earlier comments).

Chuck,
I would bet that the other Burmester drivers are similarly upgraded.
However, I suspect they need more power, to realize their potential, than the bose amp can deliver.
I have found that those hot types of speakers loose detail, when underpowered.

If someone wants to try this center, I am happy to send it to them.
It will need a little creativity to deal with the incompatible connectors.

I am targeting the sub as my next area of concern.