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Pass Labs B4 crossover questions
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Old 21st April 2018, 11:18 PM   #311
planet10 is online now planet10  Canada
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Pass Labs B4 crossover questions
Quote:
Originally Posted by MEPER View Post
dB is 20 * log(Vout/Vin)
Is there a scaling factor missing? Normakized to the 1st measurement at 10Hz.

Pass Labs B4 crossover questions-tannoyhpd385-db-chart-png

dave
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Old 22nd April 2018, 02:42 AM   #312
woofertester is offline woofertester  United States
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Quote:
Originally Posted by nzlowie View Post
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.
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Old 22nd April 2018, 03:53 AM   #313
nzlowie is offline nzlowie  Australia
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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.
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Old 22nd April 2018, 08:05 AM   #314
MEPER is offline MEPER  Denmark
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Quote:
Originally Posted by planet10 View Post
Is there a scaling factor missing? Normakized to the 1st measurement at 10Hz.

Click the image to open in full size.

dave

As far as I know dB is just a way (logarithmically) to show the relation between an input and an output. Then it has been defined the way it is so 6 or 3 dB is x2 depending on if it is voltage or watt. Then the curve is compressed compared to just showing the linear relation.
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Old 22nd April 2018, 05:25 PM   #315
Nelson Pass is offline Nelson Pass  United States
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Pass Labs B4 crossover questions
Quote:
Originally Posted by nzlowie View Post
Here is the result, bigish dip in the 3500 to 500hz area.
This measurement was inside so bass is a bit over the place.
That's a good looking result, the response is flat where the drivers
meet at around -6dB. If you were to invert the phase of one driver
you should see a good null at that point.
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Old 22nd April 2018, 11:15 PM   #316
nzlowie is offline nzlowie  Australia
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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.
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Old 23rd April 2018, 01:57 PM   #317
RogerGustavsson is offline RogerGustavsson  Sweden
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You will need a more advanced crossover than the ones discussed here in order to rule out the irregularities above 2kHz.
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Old 23rd April 2018, 02:57 PM   #318
chrisb is offline chrisb
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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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Old 7th May 2018, 05:55 AM   #319
mbrennwa is online now mbrennwa  Switzerland
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Any updates on the kit arrival at the diyAudio store?
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Old 7th May 2018, 10:14 AM   #320
JOHNNYCR100 is offline JOHNNYCR100  Abu Dhabi
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Default as above

Bump!
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