@Alex dzięki za filozoficzne, a tak na prawdę specjalistyczne podejście no i propozycje spec-badań. Tylko czy one mają sens, bo: Ty masz też NC i być może z Bose, to jeśli nie wywaliłeś tego sprzętu to masz zapewne te same parametry, dane itp. Czyż nie tak? No chyba nie ma różnic miedzy jednym egzemplarzem Bose a innym? Ja nie jestem audiofilem, szczególnie nie jestem audiofilem przy top-down, a w zasadzie po to mam MX5. Chciałbym jednak ulepszyć jakość odsłuchu..ale jeśli mam na to wydać grube setki czy tysiące pln, to zrezygnuję... Przeczytałem post gościa z miata.net i pomyślałem, że mały upgrade można zrobić niewielkim kosztem... Tekst po angielsku jest poniżej (niestety sprzed paru lat i np. proponowane tweetery Infinity nie są dostępne w sprzedaży):
"Bose Speaker Upgrade
Having come across a special deal on Infinity 3.5” speakers, it was time to finally upgrade the Bose speakers in my NC. I have been unhappy with the sound but didn’t want to do a total rip and replace of the amp and speakers. So upgrading the 3.5” speakers is an economical way to improve the sound plus add Dynamat Extreme to the doors while I am replacing the speakers.
My testing setup
Audio calibration CD – you can either buy one or I created my own (I’m cheap some times) using free FLAC files from this site -
http://www.wavecor.co.uk/testdisk.html - I used the white noise and sweep files for my testing and install. If you don’t have file conversion software to burn the FLAC files to an Audio CD you can use this free one (told you I am cheap) -
http://www.burn4free.com . I also used spectrum analyzer software on my laptop PC, you can get a free one from here (Mr Cheapo).
http://www.sonicspot.com/wavetools/wavetools.html . I also used a calibrated microphone that came with my Onkyo surround sound system, you can not use the PC’s built in microphone.
What I found
Removed the door panels (won’t cover that here, other posts already show how to do that, just make sure to have some spare plastic door snaps, I broke four removing the panels). The stock Bose speakers are a 3.5” tweeter (one way) 3.6ohm with a 100uf high pass filter capacitor attached, which equates to a 430 Hz passive crossover to the tweeter. Top mounting depth of the tweeter is 1 9/16” (ok. 4cm). The Bass speaker is an 8”, 1 ohm, rear firing woofer, no low pass filter attached so it is being feed all frequencies. Since it is a back firing speaker they are running it 180 degrees out of phase by connecting the positive woofer speaker wire to the woofers negative terminal. Due to the 1 ohm woofer you can assume the Bose amp is a digital amp, but I don’t know if it is Class D or T. There are two pairs of speaker wires in each door, one pair to the tweeter and one pair to the woofer, these are wired in parallel.
Removed the speaker grill for the center dash speaker and that speaker is also a 3.5” tweeter (1 way), 3.6 ohm with no high pass filter. It is the same as the door tweeters, but minus the capacitor. So the poor sound is mainly being caused by the cheap tweeters which are paper, and lacks a high freq dome tweeter. Poor sound is also caused by no low pass filter to the woofer.
Speaker wire color codes:
Positive wire Negative wire
Left door tweeter/woofer Green Red
Right door tweeter/woofer Yellow w/red stripe White w/black stripe
Center dash tweeter Blue w/black stripe Green w/yellow stripe
Note: the positive speaker wire to the woofers is actually connected to the negative terminal on the woofer. They are running it 180 out of phase.
Also the center dash tweeter is wound in reverse of the door speakers, so if you replace it you need to connect the Blue wire to the positive terminal on the speaker.
Frequency test of stock Bose
Tested the stock Bose speakers, top up, windows up, audiopilot off, all fade balance treble bass controls set to zero. The result was just what you would expect from a one way 3.5” speaker. The high frequencies begin to steeply roll off at 13k and are gone by 15k (see chart in excel/zip file). The center dash speaker and the rear speakers are being feed a very narrow set of freq, no bass or highs, these are imaging speakers that move the center of the sound field so the driver and passenger both think they are sitting in the middle of the stereo sound field. They have minimal effect on the overall sound quality or stereo separation, the door speakers are the important ones for that. Disconnected the tweeters and ran a 20Hz-200Hz sweep test of the door woofers to look for response and door vibrations, boy did this show up multiple vibrations in both doors, mainly from the plastic sub frame that is attached to the door. You have to fix this if you want clean bass.
Speaker Selection
I have had good success in the past with using Infinity Reference speakers to upgrade stock auto speakers. Others on this site have upgraded just the 3.5” speakers in the doors with the Infinity Reference 3012 cf (4ohm) speaker and other similar brands (be sure to install a 100uf high pass filter to the new speakers). This is a very good solution to the high freq issues, but since I was able to pick up a pair of Infinity Kappa 32.7cf speakers (2 ohm) and Infinity Reference 3022cf (2ohm) speakers cheaply, I decided to see if I could make them work with the digital amp. Putting the 32.7’s in the doors and one of the 3022’s in the center dash and designing my own high and low pass filters for the different impedance, 2ohm versus the stock 3.6ohm.
On to the door tweeter install
I installed the 32.7 tweeters in the doors and had clearance issues, the speaker are too deep (1 11/16”) and the front has an extended baffle, I ended up having to cut notches in the plastic door panel mount to get the speakers to mount to the factory mounts and had to increase the depth of the of the metal panel recess in the door (ball peen hammer, ouch!!) to get the speakers to fit. Even then the back of the speaker touched the metal door frame so had to insulate it with Mylar so it wouldn’t short out on the door. I then installed a 250uf capacitor to the new tweeter and installed a .5mH inductor to the woofer. This set my crossover freq a little lower than the 430Hz the stock speaker had. Did some testing with different freq tones and found that this crossover freq was not ideal and too much bass was going to the 32.7cf which is also high efficiency. So after some testing came up with a crossover that worked pretty well, used a 100uf capacitor to the new tweeter crossover and a .2mH inductor to the woofer (mounted at bottom of door with 3M indoor/outdoor tape), this placed the crossover freq at about 850Hz as the woofer could handle up to 1000Hz with no problem. For a passive crossover like this the capacitor goes to the positive terminal on the tweeter and the inductor goes to the negative terminal on the woofer (because it is 180 degrees out of phase) in series with the positive wires. The other thing to note is that because the new tweeters are 2 ohm instead of 3.6ohm I was dropping the overall impedance to the amp to .66 ohm, but by adding the inductor to the woofer that raised the woofer from 1 ohm to 1.2 ohm, so my impedance to the amp ended up at .75ohm which is very close to the stock setup of .78 ohm. Anyone using 2 ohm tweeters must add the inductor to the woofer.
Center dash speaker
Pulled the center dash speaker and replaced it with one of the 3022cf’s, as soon as I tried fitting the speaker in the opening I knew I had “big time” clearance problems, I probably should of quit there and put the stock one back in. But not me, I bought the damn thing I will make it fit. I had to cut out a 1 ½ inch section of a plastic Y crossmember at the bottom of the opening, this was very difficult and one slip and I would have sliced the top of the dash or my hand. After surviving that stupid move I then had to enlarge the round opening and then install the new speaker. The sound improvement is not even noticeable as no high freq’s are going to this speaker, same for the back two. My advice, leave them all stock, you gain very little by upgrading them.
Almost done
Installed Dynamat Extreme on both door frames, the Dynamat fixed all of the rattles and vibrations in the door, so this is highly recommended. Reinstalled the door panels and ran some more frequency response tests. With the new speakers the high end now holds to between 18-19k before dropping off (see before and after chart in excel file), I would of expected better from the Kappa’s which can go to 25k but I am guessing Bose put a digital filter in the amp, so the only way to get higher would be to replace the amp and or amp/HU, whichever is limiting the high end.
Final Recommendations.
Lowest Cost, Best Choice Upgrade - Install a pair of two way 4 ohm tweeters in the doors (note: you can find the Infinity 3012cf on closeout for less than $30 a pair), make sure to install a good audio grade 100uF capacitor to the positive terminal of the tweeter (the 3012cf comes with a set of 100uF capacitors). Install a .2mH inductor to the negative terminal (positive speaker wire) on the woofer, the inductor is optional but recommended. Install Dynamat or similar and enjoy the better sound. If you don’t have a source for the capacitor and inductor you can order from where I get my stuff.
Capacitor:
http://www.madisound.com/catalog/produc ... 6c5af80d82
Inductor:
http://www.madisound.com/catalog/produc ... cts_id=966
Medium Cost, Only Slightly Better Quality – For those of you who just have to have the Kappa’s do what I did, cost of a pair runs about $70. Sound improvement is worth the investment, but you will find out the meaning of “custom fit”. If I was to do it again I would install the 3012cf just in the doors.
Install Dynamat Extreme or similar over the metal and plastic of the door frame (not the removable door panel), this is needed to clean up low freq distortion and rattles. This is HIGHLY RECOMMENDED.
Do NOT upgrade the center dash speaker or the two center back speakers, sound improvement is not worth the cost or labor effort.
For the audiophile, rip and replace all the speakers, amp, HU and add a sub.
This upgrade improved the quality of the sound enough that I can live with the Bose unit. Now the wife and I are headed out for a ride to enjoy the new speakers with the new Bon Jovi (Lost Highway) CD."