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Discussion Starter #1
Equipment:

- NAB Broadcast and Audio System Test CD
- Tektronix TDS5104B Oscilloscope

Setup
- Test CD in Bose System CD changer, both swept and white noise tracks evaluated
- Scope FFT enabled with 1 Hz resolution, 250 Ksamples/s, capture length of 200 ms (1/5 of a second)

Observations
- From below 20 Hz to above 20 KHz, the head unit in the Bose labelled Clarion system is pretty flat.

- Using this high bit range CD, distortion products start to quickly emerge at volume levels labelled "20" and above. This means high level sources will start to produce distortion products that could be detectable to trained ears, probably around "24" for most sources. This is assuming good quality speakers and amps after the head unit.

Conclusion
- Upgrading the Murano's sound system should be focused on amplifiers and speakers, do not invest in changing the head unit. It's fine...

Here's a picture of an FFT from White Noise. I could optimise this, but hey, I saw enough to satisfy myself, so it is what it is.

You can see it roll off after 20 kHz, but my dog doesn't seem to care.
 

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Discussion Starter #3
One day I'll get around to sweeping the Sat radio inputs and we'll see how much of the roll off was the CD changer... But since I can't hear it, I'm not worried.

Also, I didn't really spell it out, but the test CD generates tones at the full bit range. So the peaks of the sine waves are the absolute highest you can get out of a CD. Normal CD's average audio levels are much less, so the test CD's volume is much higher than normal. This is why distortion products start to emerge at a fairly low volume level.

Normally the volume can be turned up a lot higher before you'll run into distortion.

I was quite surprised, I never expected it to be this good.

I'm looking forward to testing the output from the amp...
 

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That is quite impressive. I'd also be curious to see about amplifier output - I'm guessing it isn't going to be quite as flat.
 

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This is about what I can "hear" with my amp. It sounds pretty darned smooth up until about 20dB, even if the source is louder (ie. CD vs FM). After 20 distortion comes quick. And I have no problems with highs or lows from the head unit.
 

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It is very likely the Amp will not be flat.
Or even close.
By design.

The actual desired result here is reasonably flat response of the system in Free Air.

Once you decide to build the system to a price, and that price only allows cheap speakers, the die is cast.


For example the speaker "system" may have a rolloff at <>10K that is reasonably linear to 16K (say roughly -2 DB per 1K.) where it takes a dive.

The thought process uaually runs like this;

The stuff over 16K will be ignored at a low price range. Sorry, but that's the way it is. What you get is what you get.

The Amp will be "tuned" to have an inceasing response of <>+2 db at 1K above 10K.

The -2 DB of the speakers and the +2 DB of the amp will cancel each other out and result in an essentially flat free air response.


They will also boost the low end of the amps to make up for lack of real woofer/sub woofer response .

Call it the poor mans "equalizer".


The first "system" I ever saw this done to was the old Sony HP series.
I personally bought an HP501 because it was such a compact smooth system.

It was noted that these self contained systems had rather poor speakers that broke the rule of the day for speakers (Half your money on Speakers the other half on the other things).
So people would change out the speakers....... and then wonder why it didn't sound right.
The reason of course was that the amp was not flat by design, but was roughly tuned to the speakers.

That could easily be the situation here.

In any event sweeping the output of the amp will be interesting to say the least.
Especially if it is essentially flat.
How about taking IM amd HD readings while you are at?
Do you have a source capable of this?

Getting pretty much at the limit of your capability I should think.
Unless you also happen to have some studio standard, calibrated microphones
laying around............:p

Homer
 

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Discussion Starter #7
Well, I was really tired and limited for time, so I thought, if I was to measure at any point, and only pick one, where should I measure.

Knowing that the best mod would be to toss everything after the head unit, if it was good enough, that's where I went.

Effectively, I can make some pretty good measurements, but for the really good ones, I'll set the scope aside and use a real time spectrum analyser that's got a much higer bit range on the A/D.

Yes, I have a real time S/A that's flat from DC to whatever I choose.

At this stage, I'm just making a quick glance at flatness, not trying for accurate measurements, as I feel most road noise would make high sensitivity, low signal measurements meaningless anyway.

Took some arm twisting to get myself to do this one!

As far as IM, never mind taking readings, I can display the products!

No calibrated microphones, but if I was going to go that far, then I'd be throwing out the stock speakers anyway.

It would be possible to characterise what I have in mics, but I have other things I'd rather do.

I'll see if I can measure the amp on the weekend. That will be interesting. And also at the tweeters in the dash.
 

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With everything after the HU tossed out, I could hear distortion starting at about the 24 or 25 volume setting. One thing I really noticed after installing my aftermarket cd player is that the stereo separation has increased drastically.
 

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Discussion Starter #9
Good, that confirms what I saw in the way of products appearing.

Homer, I was actually watching the IM products appear with tone sources on the CD, by varying the volume control. Around 20, they're detectable but I'd say a good 60-70 dB below the signal level. I'm going by memory, but they were getting up to 40 dBc at around 24, if I recall correctly. I guessed that was the point where someone paying attention, would notice. Thanks Tyler!

Worth measuring for fun, if I can squeeze out the time. If I do, I'll post more images.
 

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jaak said:
Equipment:

Conclusion
- Upgrading the Murano's sound system should be focused on amplifiers and speakers, do not invest in changing the head unit. It's fine...
Maybe if you like having a cassette deck and audio CD only playback, not to mention a whopping 2 equalization controls :rolleyes: .....

Geez....it's '05 and our $33k cars come with a freakin' tape deck in the so-called 'premium' sound system.

I think probably what I've done is the shortest route to high quality sound with multiple media options......all controlled from this single display.
 

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SDS1, Sent you a PM
 

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Discussion Starter #12
That's the best one I've seen yet. But it's still not as integrated as as the stock system and looks like you cut a hole in the dash to put it in, which is what I'd desparately want to avoid.

It would be possible to put in an outboard equaliser, between the head and PA's that would give you more control than any dash radio. If you want media, buy a phatnoise product and you have tons of it, integrated into the Murano's controls. If you want fidelity, you have to run CD's. CDR's with MP3's are already old, as you can put on an iPod or the Phatnoise box that just smokes the capabilities of a loaded cd changer with mp3's. I'm looking forward to Nissan's interface for the iPod, as that will give nice integration.

Your steering wheel controls and the integrated display no longer work for audio functions.

But it's one of the best attempts at integration, I've seen so far. I just hate what it does to the dash. It's great you're happy with it! Good work!:29:
 

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Re: Re: Just how flat is the Bose?

SDS1 said:
Geez....it's '05 and our $33k cars come with a freakin' tape deck in the so-called 'premium' sound system.
Hey now, I needed that tape deck to use a tape adapter and portable cd player with after my Blose cd player died... I just couldn't survive on radio for a week!
 

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jaak said:
That's the best one I've seen yet. But it's still not as integrated as as the stock system and looks like you cut a hole in the dash to put it in, which is what I'd desparately want to avoid.

It would be possible to put in an outboard equaliser, between the head and PA's that would give you more control than any dash radio. If you want media, buy a phatnoise product and you have tons of it, integrated into the Murano's controls. If you want fidelity, you have to run CD's. CDR's with MP3's are already old, as you can put on an iPod or the Phatnoise box that just smokes the capabilities of a loaded cd changer with mp3's. I'm looking forward to Nissan's interface for the iPod, as that will give nice integration.

Your steering wheel controls and the integrated display no longer work for audio functions.

But it's one of the best attempts at integration, I've seen so far. I just hate what it does to the dash. It's great you're happy with it! Good work!:29:
Not sure what you mean by not looking integrated......I certainly think it looks better than hanging an equalizer somewhere, and hanging an iPod somewhere, and no, there's no hole in the IC board........as far as media is concerned, I've got the Excelon Keg which is a Phatnoise product......10GB drive in the back which docks to a PC via USB for uploading. It's controlled from the Kenwood HU, as is the satt. radio. I don't burn CD's anymore. To me it's very clean and simple. I guess someone could get more elaborate with the panel the face plate mounts to for a more factory look or whatever.....if that's what you're after.
Audio functions at the steering wheel could most likely be retained with my setup if you wanted to.....I didn't see the need. Kenwood HU has a remote which works fine. And the integrated display......another gripe of mine, again, $33k car and we get an orange LED readout that looks like the Star Wars watch I had in kindergarten. Would it be such a big deal to get at least 32 colors on a simple dot-matrix screen?......I keep it set on avg. mpg now. Don't see the big deal about getting to see 'FM107.7' displayed across the top.....
 

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Discussion Starter #15
Ahh, so you've just covered it up and put the face plate on... Cool...

Have you seen the face of the UK Murano? Don't know if it's possible, but it would be cool if it's actually configured to allow aftermarket head units.

Anyway, the point of the thread is, if you're looking for audio quality, you don't have to dump the OEM head unit, it's fine.

If you're looking for other things, yeah, sure, change it!
 

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I wonder why the UK cars have a different setup?. Of course it's only speculation, but I'd bet there's a similar IC board back there.
 
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