# PHD FB 4.1 Mid Bass



## ErinH (Feb 14, 2007)

I just wrapped up testing on the PHD FB 4.1 "mid bass" (I'm quoting what PHD actually calls this driver). Really, this is a midrange, but I know that the 'mid bass' will catch folks off guard.

Klippel for small and large signal. 

Dayton OmniMic for FR/HD/IMD.

*You can find the full results here:
http://medleysmusings.com/phd-fb-4-1-midbass/
*


Here's a quick rundown:










FR leaves some to be desired; the 5dB dip in response from 2khz to 5khz bothers me. Given that this dip is smack in the middle of where you'll be crossing it over to a tweeter, it makes it tougher to do so easily. (say what you want about that being nice... I'll disagree with you ). You're going to have to find a tweeter that will cross low enough to make this transition not so abrupt. Though, the typical cone breakup you see seems to be spread out over the higher octaves. 

10% THD limit for linear x-max is 1.4mm (one-way), limited by the motor which means the distortion can't easily be mitigated with a HPF crossover (like a suspension based xmax limit). My measured Fs was 113hz, verified by using both the Klippel and Dayton's DATs tool (the spec sheet says approximately 82hz). As far as distortion, the 3% THD limit is crossed at about 400hz, dominated mostly by even order and increases to ~5.5% at 200hz. Odd order distortion gets high above about 1.5khz. Overall THD rides along at about 1 to 1.5%. Which, essentially tells you not to expect to cross this very low and get clean, high output. 


- Erin


PS: I wrote all of the above having zero knowledge on what these things cost and still don't know what the going price is. Just FWIW.


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## ErinH (Feb 14, 2007)

bumping this up, since I'm not sure if anyone saw this or not (based on the lack of replies).


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## pocket5s (Jan 6, 2012)

So based on what I'm reading, it is safe to assume this is limited to a bit above 400hz and bit below 1.5k? The 400hz seems fair for a 4" (regardless of it's MB designation), but 1.5 seems a bit low doesn't it? If memory serves, it is the odd order that is the most audible correct?


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## WestCo (Aug 19, 2012)

I like the af 4.1, never heard the FB series. Ph.d. has a few nice offerings, some are better than others, but that is every company more or less.

Interesting review, thank you for sharing


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