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Modding an amp?

post #1 of 5
7/25/10 at 11:05am
Thread Starter 

Hi, I am considering getting a very knowledgable friend to try to introduce some kind of notch filter into my Voyager portable amp to reduce the 100Hz midbass hump in the IE8's. Anyone got any thoughts?

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post #2 of 5
7/25/10 at 3:34pm

I think a simple notch filter is not going to give good results.  In fact a notch filter is not what you should use at all.  For this type of application I'd suggest a linear phase band reject filter.  The TI Filter Pro tool (it's free) is great for designing these types of filters, but be warned you're looking at 5 op-amps in this case and a pretty complex circuit.  Unless you or you friend are doing this for fun, buying different headphones makes a lot more sense.

Regardless of what filter you use, it should be linear phase for audio imo.

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post #3 of 5
7/25/10 at 4:11pm

Why not just get other headphones? What you describe as the "100hz midbass hump" starts at 600Khz and ends at ~7hz (extrapolating from the graph)...

 

graphCompare.php?graphType=0&graphID[]=603&graphID[]=743

 

You need a filter 4 octaves wide (at least!) to achieve a reasonably flat response with those headphones.

 

You may be better off with a shelving filter and simply saying forget the lowest of the low bass. Which puts you right back there with other IEMs but no complicated EQ networks.

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post #4 of 5
7/25/10 at 4:18pm

Or simply use an equalizer. For example, the rockbox equalizer is very capable and will do exactly what you want. This is what equalizers are made for.

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post #5 of 5
7/27/10 at 3:33pm
Thread Starter 

Thank you for the replies. I am kind of looking for a cheap fix I guess. I like everything about the IE8's, fit, form, cable etc. Except the fact that they are no where near accurate IMHO.

I would Rock box but my iPod is 6th gen. Like everything about that except no custom EQ.

It really does sound as if different 'phones are the way forward. That will have to wait. Thanks again.

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