Rockbox Technical Forums
Support and General Use => Audio Playback, Database and Playlists => Topic started by: eric14 on August 05, 2008, 12:03:36 AM
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Newbie Newbie Newbie here.. I promised I searched the forum over and over for this, couldn't seem to find the topic. I'm running my 60gig Ipod as a head unit in my car's sound system. I'm shocked at the capability of Rockbox! :o It would give my Ipod every feature of a high end head unit!
There's just one thing I'm wondering about.. Since there seems to be a time alignment in the crossfeed feature, I'm wondering if Rockbox can do a simple left or right channel time delay so I can delay my driver side speakers to 'center' me in the sound stage?
I hope I didn't miss this in another thread, making the classic newbie mistake..
Thanks for your time.. Eric.
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No, the closest you can get is to alter the left-right balance. As usual, the maual is your friend (link) (http://download.rockbox.org/manual/rockbox-ipodvideo/rockbox-buildch6.html#x9-1080006.6)
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Crossfeed introduces symmetric delays to the left and right channels before "crossing and feeding". So it won't change your position on the soundstage. A configurable time delay for only one channel would be a new feature.
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Edit: I also want to point out that it applies a frequency filter in addition to the delay.
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Thanks guys. From reading the manual, it seemed anything was possible! I just had the center section of my dashboard cutout for two 3.5" Peerless fiberglass cone speakers. If I can get this center channel right, I'll barely know what I'm missing.
I'm crossing it over low, somewhere around 1000Hz, and I'll have full volume control over it independent of anything else in the system.
Still gonna try crossfeed though.. I'll let everyone know what I find.
Thanks again.. Eric.
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Crossfeed helps simulate speaker listening while wearing headphones by (in part) diminishing stereo separation. You don't want to use it in your situation.
I agree, though, adjustable channel delay would be a very nice feature.
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Yea, well, I have to see how it would sound.. It's probably going to come through something like Hypno-Frog from Futurama! Hope I can make it to the main switch before it's too late :-\!
I had an idea of modifying crossfeed to completely attenuate the "crossed" signals, while applying the time delay only to the left signal.
Or even dropping the normal left side signal entirely, and replacing it with the left delayed signal heading for the crossfeeding right side, at full frequency response. Not that I personally would know how to do this..
Thanks again.. Eric.
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I have read that the high end car manufacturers (the companies they hire to setup the audio) do take this in to consideration.
I haven't done the sums but how big a time difference would you need to add to the left channel (I'm in the UK, we drive on the left) for an impulse to arrive at the diver's ears perfectly synchronised?
And what about the passanger?
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The radio I had in my old car had a button for just this purpose. I could target the stereo for the driver, the passenger, or both.
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Nowadays the circuitry is found in the head unit of the system. I have a lot of friends who think using an Ipod as a head unit is just silly. This was going to be a system comprised of what I have lying around. Stuff I was going to sell, or just throw out. So I don't care what they think ::)..
There are a few head units out there now that come with a microphone that you suspend where your head (and or passenger's head) would be while driving. It will send out a signal to "learn" it's placement to correct for time alignment and some will adjust equalization to flatten response at the same time.
These head units typically need a three amp system, or a six way amplifier to use their built in three way active crossover. In this case, sub, mids and highs can all be aligned independently, including left to right.
All I was hoping for was a left to right time alignment since I'm coming out of the Ipod into a standard three way crossover. My other option in this design would be to buy a high end electronic crossover like something from Beringer. I would need to run an inverter to get 120v from 12v, but every option I could want is in there.
But, I'm a left right time alignment away from being able to say,"Oh, look what you can do with just an Ipod as the source nowadays.."
Thanks for all the effort to create the Rockbox, and the support! Eric.
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It looks like you have some agreement that this would be a nice feature. You can post this in the Feature Ideas forum if you like. Maybe a developer will take interest and implement it.
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Thank you. I wouldn't really be this hopeful if there wasn't a time delay feature already written in. It should really be nothing more than an established feature of Crossfeed with an adjustment in milliseconds. I'm just having a hard time justifying such an interest for the reason that most people are using Rockbox for headphones only.
Maybe it can be pitched as an asymmetrical earwax compensator..?
I'll head over to Feature Ideas and plead my case. Eric.