The thumb drive needs to be FAT32 formatted. Most by default are formatted that way. Then the music files you put on the USB stick need to be either MP3 or WMA files. No Apple ACC or anything else besides MP3 and WMA. After you plug in the thumb drive, you should be able to then press the Menu button and then look for an option of "Load music from USB". This will then copy the music files from the USB Stick to the internal HDD. After that is complete, then you would press the Radio/Media button and select the HDD tab. This will then allow you to play the music files that got transferred to the internal Hard Disc Drive, so you can play them back.

 

To answer your questions:

1. I'm using an Apple branded USB to Dock connector cable.
2. tried all the devices I tried were on iOS 5.1 or iOS 6.
3. The test tracks i used were taken from the JL Audio Cleansweep Callibration disc and IASCA test disc. I believe these were recorded at 0dbfs. I ripped them and tried 4 different formats: .mp3 using iTunes at 320kbs, 44.1khz, then tried it at Apple Lossless, then AAC format, then .WAV
4. EQ in iPod apps were flat, no eq. Volume n/a (head unit controls volume) Bluetooth connection was only used to check the digital output and compare it to the usb (same issues).
5. Afermarket: I'm taking the output from the factory amp speaker outs into JL summing interface, then out to a JL Audio XD-700/5 amp. (cleansweep was originally installed but removed) Vehicle is kept stock up to the speaker outputs of the factory amp.
6. Battery: I tried this with the engine turned on (14.4v) and off (12.5v).
7. Factory radio (730N RHR) EQ set to FLAT (bass, mid, trebble) and fad/balance centered.

 

Bingo Bango.

Thanks. Here's what is going on here.

The Infinity 8 channel factory amp is an 8 channel digital amp. It gets fed a 2 channel stereo signal. It then breaks these 2 channels into 8 separate channels. Each of those 8 channels will have different EQ settings, gain settings and "Delay" settings. The reason for the delay on each of the amp channels is because the speakers in your vehicle are located at different distances from your ear and sound travels at 1130 feet/sec. Therefore the sound reaching your ears will not be time aligned so that it sounds good. So delay settings in a digital amp, like the Infinity amp will add small amounts of delay to better time align the audio to make it sound good.

Now when you are using that JL Audio summing device, what that is doing with your test sine waves is that all of those channels are playing that same sound, but is arriving at very slightly different timings. Then when the JL Audio device sums these audio signals together, PHASE cancellation occurs.

Pretty much the setup you have is the EXACT definition of what causes phase cancellation with audio signals. So what you are hearing is that sine wave is being combined back together by the JL Audio device and causing it to add and subtract, so you hear dips and peaks of the recombined original signal.

This will also happen with normal music audio, but not as bad so you may be unable to hear it, because the key to phase cancellation is the audio signals that are being summed together must be "similar" for them to be able cancel out. So a single sine wave combined with fits that definition of needing to be "similar".

If you want to understand this more, I would suggest reading up on audio "phase" relations and "phase cancellation". You'll then understand why you're hearing this warbling that you describe.

An explanation as to why you may be hearing this warbling sound on iPod devices and not CD is because the radio communicates with the OEM Infinity amp through the Can bus. The radio tells the amplifier what "source" is currently selected. This in turn allows the amplifier to be tuned and adjusted so that specific settings can be loaded for each "source". So it is very well possible the settings for an iPod source may be slightly different enough than a CD source where these slight setting differences add up to big differences when it comes to adding and subtracting of audio signals.

Put your system back to stock and I guarantee you, your warble bug goes away.

 

Rednroll,
Thanks for the educational thread. It has a lot of great information in it. I know a bit and have seen a lot but I am always open to learning more. I have worked with people who decided that because they have been doing their job for many years that no one can tell them anything and they know everything with no further learning. With things changing constantly, you have to be willing to be humbled at times and have an open mind to learn.
Thanks again.

 

This makes a lot of sense and would seem to explain alot of issues I have, esp with the Cleansweep. I started another thread with my Cleansweep issues but this thread seems to be answering more of my questions. Has anyone been able to confirm that the infinity amp actually does make time alignment adjustments to each channel or is it just so common among OEM systems that it's safe to assume that it does?

I'm not an expert on delay and timing so forgive my ignorance but if the timing (delay) is being adjusted with the factory amp why would the adjustments change depending on the sources? Aren't delay adjustments based on fixed distances from the listeners to the drivers more or less?

If the phase cancellation issue is happening due to the summing device could it possibly be made worse even by adding the Cleansweep + Summing device? I removed the Cleansweep because it sounded so harsh and completely sucked out the "dimension" to the sound. The sound with the cleansweep processing active could best be compared to a speaker pair being wired out of phase. No low-end output in the front stage, harsh highs, muddy output from the subwoofer and a huge gap between the sub-bass and high end.

The Cleansweep+Summing interface is designed to be used for OEM integration. I would THINK that it would be common for these devices to encounter vehicles with factory amplified systems like the Jeep and would be designed to accommodate these sorts of situations. If the OEM integration solution from JL isn't going to work because of the nature of the factory amplified system then I would assume other summing devices would have that problem too. Would it be best to eliminate the summing interface all together and feed the aftermarket amp each filtered channel from the factory amp individually and run my components in a bi-amped setup? Is that the only way that you wouldn't mess with the output of the factory amp and run into issues w/ phase/timing/cancellation?

 

The thing is anytime you "Sum" 8 different audio signals, there is bound to be phase cancellation at some frequencies and phase addition at other frequencies. So while you are experiencing a phase cancellation at one particular frequency using your sine wave test tone, that does not mean there is a major problem with the summing device.

Read up on "comb filtering".

Here's a pretty good article that does a pretty decent job.
The Studio Files » From Theory to Practicality – Comb Filtering


Tell me if this snippet from that article seems to pertain to what the JL summing device is doing?


FYI, I have no idea what the clean sweep does to be able to explain what is going on. My guess is that it is probably some kind of auto EQ processor. If it is, then EQ can not fix phase related comb filtering problems, it actually makes it worse in most instances.

 

Yeah, i mean, it sounds like that could be happening. The description of what "comb filtering" sounds like in the article is really similar to what I'm hearing. The Cleansweep is a processor w/ an auto eq. It takes the summed full-range signals from the summing device and tries to flatten out the eq curve that factory systems implement so that you can feed a flat signal to aftermarket gear. Like i said the sound is worse w/ the cleansweep active but I have more noise and a "colored" sound without it. What I mean by "colored" is that music sounds like it's recorded at a lower bitrate and doesn't sound totally clean, as if the pitch is changing ever so slightly at a rapid pace. Alot of people report great results with the Cleansweep and cite it as a good way to get "aftermarket sound" from a OEM head unit. I got it because I wanted to keep the factory Nav/bluetooth, etc, be able to upgrade some components and get the best sound possible. I obv have to rethink how I'm going to do this now. I've been working on this since september and have debated giving up and going back to factory many times. It's been a huge PITA with very little reward because of all these issues. Seems like now i'm just struggling to get it to sound as good as factory, which puts me at square one.

 

Yeah, that's actually a pretty accurate description of what comb filtering sounds like. So that's what you have going on with your system.

I would expect the Clean Sweep to then make it sound worse, because essentially it would then be trying to boost up frequencies that got notched out by the comb filtering. Thus, you can't boost frequencies that are no longer present. Therefore in trying to do so, the clean sweep is just boosting the noise floor and adding distortion.

Instead of ditching the whole thing and trying to start over, here's what I would try. Instead of trying to SUM all 8 channels from the OEM amp, I would try summing 4 or 6 channels.

I would 1st try summing.
Left=(L/F tweet+L/F woofer + Sub1)
Right=R/F tweet + R/F woofer + Sub2).

Then without the clean sweep attached, see if you get a fuller sound.

If that doesn't sound better then try:
Left=(L/F tweet+L/R woofer + Sub1)
Right=R/F tweet + R/R woofer + Sub2).

Then as a 3rd option try:
Left= (L/R woofer+Sub1)
Right=(R/R woofer+Sub2).

The 3rd option should give you the least likely hood of comb filtering.

 

I didn't mention that in my current setup I'm only summing the Front 2 channels and the 2ch of subwoofer output. The rear channels are not being summed because I would need another summing device to do that. My current setup matches your first option:

"
Left=(L/F tweet+L/F woofer + Sub1)
Right=R/F tweet + R/F woofer + Sub2).
"

With option 1 currently setup in my jeep the sound is definitely fuller but it just sounds a little odd. Sounds not quite clear and the noise floor is pretty high. Lowering the input trim on the summing interface seems to be the only thing that will bring it down however when I lower the input trim i don't have sufficient level for summing (according to the led's on the summing device). There's 3 trim adjustments in 3-way mode, which i'm using. There's one for each pair of inputs Hi (tweeters), Mid (front woofer inputs) and Low (sub inputs). The high and low inputs were needed to be set to line level input because they were too weak on spkr level and the mid is on speaker level. I also get occasional pops and clicks, not loud but pretty consistent. And then there's the "colored" sound characteristic that's present.
If I use option 2, wouldn't I be missing information that is only present in the Left front woofer channel output like navigation voice and phone audio? I would have the high frequencies of that audio from the tweeter output but no lower end right?

 

Option 2 would still give you low end since you're still summing it with the sub.

You should still get some navi voice because the Navi voice should also be coming out from the front tweets.

You're probably getting pops and clicks due to overlapping mid-range frequencies where it sounds like the JL Audio is a digital summing processor, where you're exceeding the digital head room limit. The front tweets probably have some mid-range frequencies and the front woofers probably do also. So when these get summed together, some frequencies will double and others will cut. Thus, the bumps and dips of a typical comb filter.

You never did tell me the frequency of the sine waves. My guess would be it's a 1Khz sine, which falls right into that suspect overlapping mid-range area.