HF10AK + 12P80ND + custom WG

limacon

Member
2019-10-19 10:09 am
The distortion peak coincides with the great dip of HF10AK. Could you measure distortion per driver?

Both drivers measured at 50cm on axis. No EQ, just Xovers.

12P80NDv2
700Hz LR4

12p80nd2 50cm axis dist - 700LR4.jpg



HK10AK
200Hz LR4

hf10ak 50cm axis dist - 200LR4.jpg
 
Cool, it looks like the HF10AK is source for the distortion although here the distortion is quite low +40dB down. On the previous distortion measurement your levels were ~99dB and here ~87dB, according to the legend, and the distortion is was more.

If the distortion doesn't sound bad with usual listening levels then I wouldn't be worried about it. If it sounds bad, honky/grainy/hard/whatever sound that catches the ear occasionally then you could try slide the xo higher up.

On my system/xo variations with HF10AK during past few years I've always gravitated towards higher xo because it sounded better, but it might be due to any reason. I've got smaller of the shelf waveguide, different woofer etc. might be anything. Just an observation that higher xo frequency yield better sound it might we worth a try, especially since you have a DSP. It's been fun observation, I always want to push the xo as low as possible, but end up much higher after a while :D

edit. just checked current system simulation and seems to be ~20db down around 500Hz, your latest shows around 400Hz. I'm 6db down at 1kHz, so it is a bit higher xo and more gradual slope I think, didn't check what the name of the slope is :)
 

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limacon

Member
2019-10-19 10:09 am
Cool, it looks like the HF10AK is source for the distortion although here the distortion is quite low +40dB down. On the previous distortion measurement your levels were ~99dB and here ~87dB, according to the legend, and the distortion is was more.

I've been trying to stay with two test levels

1). 86dB
2). 96dB

So I can compare with some of the speaker reviews over at AS.
 

limacon

Member
2019-10-19 10:09 am
That is reasonable thing to do!:) However, it is notable how the distortion is roughly 10db worse at the 10db higher output level! Might get into audible territory? Have you compared to the AS reviews, how it compares?

AKC360, nice tip! sensitive devices.

I’ve located the source of the distortion.

The HF10AK adaptor plate was 0.6mm too thick. When bolted up it was not actually sealing well (at all) to the location face at the back of the waveguide.
 

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What's on the other side of the cabinet your mic is on? You will be getting a lot of interferece from the proximity of the mic to any surface. Can you get a cheap mic stand a extend the boom as far out as possible a la:

1642467433325.png


This is how I do it which is the best I can do in a small british house:
https://www.diyaudio.com/forums/attachment.php?attachmentid=998193&stc=1&d=1637099038
I'd bet the ripples in your noise floor and spectogram are from speaker and mic boundary proximity. Getting the speaker away from walls and up in to the air will help a lot too.


I just bagged a pair of HF10AK so I am reading your thread with great interest. Mine have very minor variation from one unit to the next around the 2k mark. Have you compared yours? Here are mine on STH100 horn at 35cm just for a test run. Distortions:

hf10ak fr.JPG


hf10ak dist 1.JPG


hf10ak dist 2.JPG


I hope this helps :)
 
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Are you EQ'ing up or down? I tend to EQ everything down rather than EQ one thing up. Choose a low point and aim to level everything down to that to avoid any chance of clipping from the output of the DSP. You can adjust gain afterwards (tho I doubt you will be anywhere near clipping owing to the tiny signal needed to drive these drivers)
 

limacon

Member
2019-10-19 10:09 am
Are you EQ'ing up or down? I tend to EQ everything down rather than EQ one thing up. Choose a low point and aim to level everything down to that to avoid any chance of clipping from the output of the DSP. You can adjust gain afterwards (tho I doubt you will be anywhere near clipping owing to the tiny signal needed to drive these drivers)

PC -> Topping D10s SPDIF -> DC-One -> MC2 T4-250 (CD set +6dB above W)

The DC-One crossover levels are both set to -10dB - no lights are on DC-One outputs at 106dB levels. No lights on the MC2 yet.

I dont use pre-EQ - just use the output PEQs +/- where needed.
 

limacon

Member
2019-10-19 10:09 am
A small lesson from the M2.

I’ve installed a high pass 16uF ClarityCap CSA and a 7.8ohm -9dB pad (Jantzen SuperRes).

The horn loading plus a 1070Hz 6dB BW DSP filter creates a 36dB slope with a 700Hz corner.

Added benefit is that a small amount noise / hum has been all but eliminated. These waveguides are a microscope!

Relative distorition plot attached.


1642646192680.png
 

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