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milosz, thanks for the detailed analysis. I don't mean to minimize the effort you put in, but for the rest of us following along, it seems to be that an easy way to fix the bose system's response would be to apply your EQ settings on the source files that are being played. So, in essence, digitally applying the EQ on files that are burnt to DVD or on the flash drive. No physical mods needed. This is probably best for FLAC source files, which can have the transformation applied before being encoded into your preferred format for the car to play.
Likely similar to an earlier poster recommending EQ using Viper4Android, except no phone is needed.
milosz, thanks for the detailed analysis. I don't mean to minimize the effort you put in, but for the rest of us following along, it seems to be that an easy way to fix the bose system's response would be to apply your EQ settings on the source files that are being played. So, in essence, digitally applying the EQ on files that are burnt to DVD or on the flash drive. No physical mods needed. This is probably best for FLAC source files, which can have the transformation applied before being encoded into your preferred format for the car to play.
Likely similar to an earlier poster recommending EQ using Viper4Android, except no phone is needed.
Yes this would work, certainly, for music from the iPod or from DVD-ROM; obviously this would not work for FM or Satellite.
Be a bit of a drag to change the EQ for 150 GB / 6,000 tracks in order to tweak the response, like right now I want to add a little more "body" to the midrange - maybe 2 dB at 400~800 Hz. To re-eq the 6,000 tracks I have on my iPod to accomplish this would be a pain, even though you could automate this by having all the file names / original locations in a playlist-like file on the PC used for the processing, and using something like DSP in dBPowerAmp MP3 converter, converting the source FLAC files to the 320k MP3 files for the iPod wile at the same time applying the EQ. (I haven't used the DSP EQ in DBPowerAmp's converter and I don't know if it is granular enough to achieve the required curve; an alternative would be to use something like Adobe Audtion in batch mode, which would certainly work, but take quite a bit longer- still, it would be an automated process running on my PC, so it would not be too terrible a burden - not like manually EQing each of 6,000 tracks.)
So, yes, your point is absolutely valid as far as it goes. Once you got an EQ curve you were completely happy with you would be able to apply it to all the tracks you listened to from iPod / USB memory / and DVD-R- which is the bulk of "serious listening" for most drivers. No custom harnesses needed (which was to me the most complex part of my method) and ZERO EXPENSE if you already own the software.
Frankly, I never thought of this. I just charged ahead to identify why I didn't like the stock sound and then worked to remediate it in the cars audio chain.
My MiniDSP has stopped working now that the weather is cold (In Chicago it is routinely between -3° and 5° C this time of year)
Connecting a PC to the MiniDSP I see it's digital circuits are still active, but putting a 'scope on the output shows no audio coming out.
I wrote MiniDSP about this, and they said:
"Please note that this unit isn’t meant to operate below zero degree btw. ....It’s most likely that at below zero, it’s your battery that has a slower rate to achieve 12V. That rate doesn’t trigger the un-muting of the outputs."
It would have been nice if their web site mentioned that.
Right now, in order to have some music and use of the audio for bluetooth phone calls, I've just jumpered the audio lines around the Mini-DSP, effectively taking it out of the audio circuit. I've written MiniDSP to ask them if they could provide a schematic of the audio output stage of the unit showing the muting circuit, which I would then just defeat.
SO- anyone out there planning on using a MiniDSP in their car in cold climates please be aware that you may run into the issue.
They probably don't use milspec components (milspec usually just has a wider temp operating range).
You could also use a short timer circuit to delay power-on for 10 seconds, to let the engine and alternator stabilize - then you should have full voltage when the DSP initializes.
They probably don't use milspec components (milspec usually just has a wider temp operating range).
You could also use a short timer circuit to delay power-on for 10 seconds, to let the engine and alternator stabilize - then you should have full voltage when the DSP initializes.
Or, you know, move south
...or I could plumb coolant lines from the engine to the trunk-deck area and use a thermostatic switch to power up the DSP once the coolant warmed up - HAHAHAHAHAHA
**Yeah a time delay makes sense. A relay and a 555. Thanks for the suggestion!**
I can test that idea by disconnecting the MiniDSP from power (pull the power input plug) starting the car then manually plugging the power into the MiniDSP. If the slow-to-rise 13.6 voltage of the car is the issue, this would show it. But I'm wondering if maybe the cold weather makes the output muting circuit of the MiniDSP completely inoperative."
There's a JL audio DSP that I could use in place of the MiniDSP, my wiring wouldn't have to change much I already have extracted the left and right balanced audio lines from the Bose harness. But that thing is like $500, on top of the ~$150 I've already spent. There are other commercial DSP EQ type things being sold, but few of them use balanced lines. JL seems to be a high-quality brand as far as I can tell. And I bet their gear will work below 0° C.
Here's the tweeter mounted in the measurement rig from the previous post.
Here's the frequency response - not a great graph, I saved this at the wrong size, but you get the overall idea. Good response up to about 15 kHz, at which time there's some raggedness which also shows up a little in the waterfall plot as an energy storage thing. The way this tweeter is "aimed" from the sail, I don't think much of this above-15 kHz sound reaches the driver, except maybe as reflections from sound bouncing around in the cabin. This is not a bad tweeter, though I would say that since it has just a 4.7 uF capacitor as a series crossover from the signal driving the midrange, I am guessing that the output of this driver overlaps and adds to the output of the 3.5" midrange, adding to the sense to "too much treble" in this system. I think that with a 2nd order- or even 3rd order- high-pass crossover at about 5 kHz, this driver might make a decent tweeter to compliment the 3.5 inch midrange. But as I said in the previous post, that midrange has GOT to have a 5 kHz low-pass in series with it, it should NOT be used full range.
Miloz,
Thanks again for all of your hard work on this!
I'm getting ready to add passive crossovers before a sub woofer and would like your insight.
My plan is to remove the in-line capacitor for the tweeters and install a custom 12db Linkwitz–Riley for both mid and tweet at 5KHz - I may not be able to find the 3.8 mfd cap so may lower the frequency a touch based on available caps.
Questions:
Any issues using a LR crossover? This flat at the crossover frequency and based on your testing I wouldn't want a bump.
Would it be worth it to create a 12db low pass for the center channel? As it's the same driver as the doors it would exhibit the same performance, however the volume of the driver is fairly low so I don't know of the low pass would make a difference - however the driver is reflecting directly off the windshield so that might be a factor.
I hadn't thought about the center channel. If you put a 5 kHz low pass on that driver, I would think you'd need to add a tweeter as well. Try it and see. You might not feel like a tweeter is needed.
If you want to experiment try something small like Parts Express 5/8" soft dome Part # 275-025 would work well I would think. You could just try it out at first... then if you like it, you might even be able to mount it right in the center of the front speaker grille- maybe behind the grill or mounted flush with the grille by cutting a hole in the grille for the tweeter...
12 dB L-R xover at 5 kHz is a good choice for the door midrange-to-tweeter xover I think. I don't think you'll have any freq. resp. bumps from that.
I'd be curious to know how it sounds when you are done.
Installed crossovers on Wednesday, however only installed the low pass on the squawker. The 4.7 mfd cap for the tweeter is attached to the housing and I didn’t have time to remove and bypass so I left it in for now, if 4 ohm would be 9KHz 6db high pass using electrolytic capacitor.
Ordered components from Madison Sound – 3.9 mfd Mylar caps with 0.25 mh 20 gauge air coils. I prefer Mylar (or anything) to electrolytic for sound quality and ordered the same caps for consistency – for the low pass the cap doesn’t matter as it’s connected to speaker return.
Crossover significantly reduced the output from the mids and reduced the harshness, system sounds more balanced now. Highs are still slightly harsh and I don’t know if the cause is tweeter quality, output, or if the Bose amp is clipping and lacks headroom at higher volume. The waterfall plot indicates the tweeters break up above 15 KHz, however I’m 50 so probably can’t hear much above 12-14 KHz so might not be audible for me.
While in the doors I also added additional peel and stick along with fiberglass insulation to tame the metal cavity. Bass and mid bass sounds better and fuller. More to come as I continue to listen to various tracks but I have noticed that saxophones aren’t as harsh, along with cymbals, and certain music isn’t so piercing. For example, the beginning to Love is Gone (David Guetta, Joachim Garraud & Chris Willis) was previously so harsh I needed to turn down the volume for the intro – it’s now better but still harsh. Tech music (i.e. dubstep) is much easier to listen to as well.
Milosz,
Thank you for taking all the time to document your experiments. Very interesting and informative. I have a couple of questions.
Just curious if you are still using the miniDSP?
Also do you have any pictures of your DIY adapter harness?
And lastly, did you ever get a 10" door woofer to test?
Milosz,
Thank you for taking all the time to document your experiments. Very interesting and informative. I have a couple of questions.
Just curious if you are still using the miniDSP?
Also do you have any pictures of your DIY adapter harness?
And lastly, did you ever get a 10" door woofer to test?
The MiniDSP stopped working (no audio output -) below about 35° F, so I took it out of the circuit. I posted questions on the MiniDSP forum and some people said theirs worked down below 0° F, while one or two others said theirs did not. MiniDSP said "it's not made with mil-spec parts so we do not guarantee it will work in the cold." I bought another MiniDSP Balanced which I will be testing at 0° F (using a freezer) but I have not gotten around to that. I am hopeful that the new MiniDSP will work in the cold, maybe the one I got eriler is bad.
I never got a 10 inch Bose door woofer to test.
The harness I made is not pretty, but it works. First picture shows the plugs / sockets I started with, second shows the finished harness.
FYI - i've been using the Jet Audio music player app (Android).
it has a 20-band EQ that makes the Bose sound decent (along with a powered sub). it also has paid add-on DSP plug-ins (bought a few of them), but the EQ alone can pretty much get the audio where i want it.
To convert from the Bose balanced signal pair to the single-ended RCA inputs of the Alpine MRV-M500, I used an RDL TX-1A
Milosz, thanks for sharing your expertise. After an extensive search for how to add a sub to my '09 G37, your post is by far the most credible, informative, and helpful.
It is my understanding that the Alpine MRV-M500 can accept a balanced signal into its RCA jacks. Does this eliminate the need for the balanced to unbalanced converter?
In any case, can you walk us through your process to properly set the level on the RDL TX-1A?
Milosz, thanks for sharing your expertise. After an extensive search for how to add a sub to my '09 G37, your post is by far the most credible, informative, and helpful.
It is my understanding that the Alpine MRV-M500 can accept a balanced signal into its RCA jacks. Does this eliminate the need for the balanced to unbalanced converter?
In any case, can you walk us through your process to properly set the level on the RDL TX-1A?
Cheers,
-R
Are you positive that the Alpine MRV-M500 can accept balanced differential inputs? I just looked over the owners manual and don't see anything that would suggest it does. There definitely are amps that will accept balanced differential inputs and alleviate the need for the RDL TX-1A.
I saw the RCA jacks on the Alpine amp and just assumed it was a single-ended and not a balanced input, so I found the RDL TX-1A balanced-to-single ended part and used that to convert. It never occurred to me that Alpine might have isolated the outer shield of their RCA input jack, and that the Alpine input circuit could be balanced differential. When I see an RCA jack, I think single ended, but it IS possible to use the shield of the jack - isolated from signal ground- as the minus input and the center pin as plus input. This would work with either single ended or balanced signals.
Looking around the Internet I find this=> https://forum.e46fanatics.com/showth...=528285&page=3 reference to someone who has contacted Alpine and Alpine tells them "all Alpine amps, past abs present, accept balanced inputs"
Probably best to contact Alpine directly to confirm this, but an easy way to tell if it's likely to be true is to use an ohm meter and measure between the outer shield on the Alpine amp RCA input and the Alpine amp's chassis, and also try the same between the shield on the RCA and the negative DC power input on the amp, just in case the chassis is floating or something. NOTE: ONLY DO THIS WITH THE AMPLIFIER OFF, UNPOWERED. If you see a very low resistance between RCA shield and ground, well then it's single ended. But if it's not close to a dead short then, yah, it could well be a differential balanced input. In which case you would not need the RDL TX-1A. The + subwoofer signal line from the Bose "main amp" chassis - yellow wire in the harness - goes to center pin and purple ( the - subwoofer signal line) goes to the outer shield of the Alpine amp input.
I set the RDL TX-1A by adjusting the level control on the Alpine MRV-500 to about "50%" and then tried adjusting the level control on the RDL TX-1A to be about the right subwoofer level, by ear, but it was always too high. Turns out the subwoofer line signal from the Bose main chassis must be pretty hot. So I turned the Alpine level control down to about 25% of it's rotary travel, and then I set the control on the RDL TX-1A. Your mileage may vary. I hung a scope on the output of the RDL TX-1A and looked at both a 20 Hz sine wave and also some music just to make sure I didn't see any clipping or other things that would tell me that something was wrong, and it looked fine.
These subwoofer level adjustments will vary a lot from my case because your subwoofer driver / box combination may be more efficient or less efficient than mine. Between the heavy-cone Dayton sub driver and the sealed box my setup is not efficient at converting electrical power into acoustic power- but that's what 500 watt amps are for. I get all the subwoofer level I want with this setup, I can crank the overall volume up to the point where the front speakers start to sound distorted and the subwoofer is still clean. I think the front 10-inch woofers are OK drivers and the Bose amp has 50 watts a side for them, but there ARE limits to just how loud this Bose system can play. I have to say that it is PRETTY LOUD, though head-bangers and hiphop listeners would probably want more, which I think would require a total re-working of the front speakers, amps and so on. I have taken some distortion measurements at just over 100 dB SPL as measured in the front seat and things are still fairly clean so I'd say that augmented by a sub the Bose system can get to 102~105 dB in the drivers' seat and still sound pretty clean. One can always do better with the application of large amounts of money and effort, of course.
To speculate on what **MIGHT** be done to really upgrade the sound, starting with speakers in the doors - I think there might be 6 or 6.5 inch mid-woofers that could work, but you'd need all new electronics too- you'd want to keep most of the deep bass out of these door woofers and rely on trunk mounted subs; then you'd need new midranges and why not tweeters too in the doors, and DSP crossovers adjusted for driver EQ and steep crossover slopes. And POWER. Lots of power. Probably have to modify the door to fit the new midrange drivers, and you'd want to work on the "enclosure" for the door mounted woofers. It would be a lot of work but it could be done. A lot of work and a lot of money. I have not heard them in an automotive setup, but I really like Focal HiFi speakers, and have designed some 2-way home speakers using their Utopia drivers and they are high quality drivers- for some reason, in my imagination, I think that a set of Focal Utopia drivers, properly mounted and with good electronics and good subwoofers, might give excellent results. There are lots of other good hi-end automotive drivers out there - Dynaudio Esotar, Scanspeak, etc.- if you have the $$ to spend on this and want to go "all out" the sky is the limit.
But I have to say, with some appropriate EQ and a good sub, the Bose system sounds pretty darn good. (HAHAHA though as someone who suffers from audiophila, I always want to try one more tweak: I'd like to hear what the Bose system would sound like with a proper crossover between the Bose 3,5 inch midrange and the Bose tweeter- to see what difference spending $10 on inductors and capacitors would make- and I would try it, too, if I wasn't too lazy to remove the door cards. Too lazy and also afraid I'd get impatient and break some plastic mounting clip and never be able to get my door back together properly.)
10-22-2018, 02:09 PM
