Pass Labs B4 crossover questions

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frugal-phile™
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How do i convert voltage to dB?

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dave
 

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Here is the result, bigish dip in the 3500 to 500hz area.
This measurement was inside so bass is a bit over the place.

Thanks

The ripple of the low frequency driver seems notable. It reminds me of the ripple that occurs with an unstuffed transmission line for the octaves immediately above the 1/4 wave length tuning frequency. I have never seen a room do this to a speaker. I have seen this when you attach a driver to a long PVC pipe.
 
Yea the bass is a bit wobbly but those are room nodes as the measurements were taken inside. The dip that concerns me is the top of the mid drivers range which when summed makes the dip from 3500 to 5000hz. (Not 3500-500 as first mentioned.)
Trouble the natural roll off of these drivers is virtually identical to the cross over, the crossover really only appears to provide protection.
 
I tried inverting one of the drivers but that just made things worse... I was thinking that your new xover might be able to provide compensation for the early drop off on the mid range as shown in the individual plots.

Or...... should I not worry about this dip? Just that I thought a fair bit of music detail would be contained in this 3500-5000hz range.
 
There are several pages describing extensive upgrades to the HPD 385’s crossover

tannoy hpd 385 crossover upgrade - Google Search

But I think that much of the aberrations on these puppies above 2000 - 2500Hz would be require more correction along the lines of multiple parametric EQ to arrive close to “flat”response

Measured FR curves from Tannoy, and a couple of independent sources:
tannoy hpd 385 frequency response measurements - Google Search

Not a fan of the couple of factory builds that I’ve heard - Westminsters and Ardens, plus a custom built pair of 12” in “small” stand mounted, and 15” in fridge sized Churchill knock-offs. To each his own
 
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