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DJ Monitor using B&C 12HCX76

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SteveAATW View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveAATW Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 12:06am
Ah, thank you! Will change and re-test
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 9:38am
Another approach to setting the filters is as follows:

Measure the raw response of each driver on axis
Measure the raw response off axis to check if there is an area where the attenuation off axis matches
Measure the response of a filter on the DCX - this will be your acoustic target response (HF first your case as filter will be near lower limit of HF driver) Pay attention too phase versus target response.
Use low 'Q' filters to flatten response of HF driver
Overlay target response of DCX filter (eg LR24)
Attempt to use EQ and filters to match the HF response to the target.
If not possible to match to given target then adjust target to make it achievable by iteration.
Follow same process with LF to match ideal HF filter response.
Pay attention to the phase response of the drivers compared to the DCX target response.
Use delay in DCX to get phase response of LF and HF to overlap neatly through crossover region

Remember that it is the combined acoustic response of filters and drivers that matters - not the filters alone.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 11:42am
try using a second or third order slope - might smooth out that dip at 2.4kHz. and better transient response.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 2:07pm
Your measurements look a bit wiggly, I presume your not using time domain gating.  Try getting the speaker up on a tall pole and away from surrounding objects along with gating to get quasi ancoic results:

This won't cover bass measurements unless you have a very big pole.  The usual way to get those is to perform them on a ground plane or near field and then splice with the gated response.

The best way to see the box tuning frequency is to measure the box impedance minimum frequency which can be done using a power amp, a resistor and a multi-meter. 
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SteveAATW View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveAATW Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 9:20pm
So I can't get it up on a pole at the mo, but the software (LARSA) apparently does have a method of compensating for room dynamics and reflections.

New measurement attached with that enabled and LR24 filters on the crossover.

Will take it a fairly dead studio in a few weeks and get it on a pole.

If you could explain/link me to the method of measuring minimum impedance it would be appreciated


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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 12 October 2020 at 10:55pm

if you look at the impedance curve in the above link your aiming to find the minimum between two peaks.
1) connect speaker in series with resistor (8 ohm for example)
2) connect multi meter in AC volts mode across resistor
2) connect to power amplifier output
3) drive amplifier with sine tone generator (EG from pc software)
4) adjust the frequency until you find the first peak in impedance (local maximum volts reading)
5) adjust the frequency until you find the 2nd peak
6) between those two points find the minimum impedance (minimum volts) this is your tuning frequency.

You can confirm this by observing the cone when driven to visible excursion it should stop moving at the tuning frequency.  Be careful not to run at significant power for long in this condition as the coil is not moving so poorly cooled.
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SteveAATW View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveAATW Quote  Post ReplyReply Direct Link To This Post Posted: 13 October 2020 at 10:48am
Appreciate the explanation Smile Will test and report back
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 October 2020 at 5:53pm
Whats with the HF rolloff?

Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
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Jo bg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2020 at 7:33am
There is some even in his genelec measuring, so probably mic or measuring...
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SteveAATW View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveAATW Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2020 at 10:58pm
I did notice that, was one of the reasons I got the Genelec side by side with it. The measurement situation isn't exactly optimal here LOL Will get it in a very dead studio in as free space a config as possible in a few weeks.

Listening test wise no noticeable HF issues, it isn't quite as bright as the Genelec, but then they do have their characteristic sound. The B&C has an impressive amount of clarity and detail for a PA speaker and the coax arrangement works brilliantly for a monitor.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 16 October 2020 at 3:28pm
Are you applying eq to the hf?
While the genelecs should sound good with no processing, some lifting of the highs is usually done to compression drivers on most horns.
Consider applying a shelving eq, might get some brightness back, just test also at higher volumes, bright at low volumes could result harsh at high levels, as hearing sensitivity to highs increases with level.
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