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Help! Look at this smart traces...

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Jo bg View Drop Down
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    Posted: 15 December 2017 at 9:23am
Hi
Measuring the rig inside yesterday, i found out two compression drivers have different magnitude and phase response.
I had troubles with the tops until I noticed this... Same processing, same amp,no passive crossover, I even tried to swap speaker on amp outs but the result is the same so it is either the driver or the horn or the assembly, a compression driver has this large peak between 2 and 4k and the other i flatter (both aftyer same eq), but I think the one with problems is the flatter one that shows coherency issues in that range.
Phase is different too. Drivers are 18sound nd1460 with xilica processing and labgruppen amps.


Edited by Jo bg - 15 December 2017 at 2:12pm
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Young Croc
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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 December 2017 at 9:31am
Will have to open them up but what would you guess looking at the measurement?
I discovered this late so we didn't have the time to investigate further, but even playing music that peak is very clear.
Could try to eq it out but seems to big to be sample variation and too localized between 2k and 4k to be reflections..
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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 December 2017 at 3:52pm

opened up the one midtop with Ragged response and less coherence but the horn and CD are firmly attached as the first day.
Opened the CD and looks good, could it be a centering problem? I am scared of removing the diaphragm
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Teunos View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Teunos Quote  Post ReplyReply Direct Link To This Post Posted: 15 December 2017 at 4:04pm
It could be a centering issue (but it doesn't have to be).
Seen these kind of issues before on off-center diaphragms replaced by inexperienced people.
Best way to center them is to use a constant sine signal running through it. Then move around and tighten while keeping it sounding good (you'll notice instantly if it's off).

I always use my capacitance meter as signal source, works a charm. Re-did quite a few diaphgragms for several friends who tried to do it themselves and failed.

The even better way of doing it is to do this while simultaneously measuring the impedance of the coil, but that gets kind of complex.

EDIT: BTW, what driver is that, looks like an 18sound one (ND1460?). They have a filler ring below the diaphragm. They usually come supplied with two or three from the factory, depending on the exact alignment of the diaphragm this can help.


Edited by Teunos - 15 December 2017 at 4:07pm
Best regards,
Teun.
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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 December 2017 at 6:21pm
thanks
yes 18 sound nd 1460. as i am one of those inexperienced peolple i think i am going to take some more measurements  before attempting at reallingning something that could be allready aligned...
I was the first owner so chances are someone more experienced did this the first time at 18sound...
 
what else could it be ? dirt inside? coil that starts burning or detaching?
do you agree that it goes over "sample variation"?
 
 
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Timo Beckman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timo Beckman Quote  Post ReplyReply Direct Link To This Post Posted: 16 December 2017 at 9:56am
Could you make the transfer files available?
The sound will be as good as the band play's
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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: 16 December 2017 at 10:59am
hi Timo
i measured the suspected driver and posted the tf in another topic here in advanced discussion, i felt this was a little confusing... thanks for chiming in!
By the way i started using your 2nd order allpass teachings to straighten the sub phase and get a better alignment with the midbass. now need to sort out the cd problem and then start to play with them on the mid highs...
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 17 December 2017 at 10:54am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 17 December 2017 at 6:28pm
Originally posted by Jo bg Jo bg wrote:

Measuring the rig inside yesterday

I have seen this type thing before so I'm going to throw this out there. The only way to measure indoors and make any kind of reliable comparison between different cabs/drivers is to setup the test system and a speaker, measure, then move that box out of the way and place the second box in the exact same spot. Absolutely nothing else can change. If that is what you did then great you can consider the comparison valid, just be aware you are measuring the speaker and the room.. not just the speaker.
If you simply setup the two speakers in a room and are comparing left to right traces without moving  anything the test is invalid, if the mic was moved the test is invalid, if somebody else came into or left the room the test is invalid,  if a door was open for the first sweep and closed for the next the test is invalid. Get the idea?


Edited by Conanski - 17 December 2017 at 6:29pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote concept-10 Quote  Post ReplyReply Direct Link To This Post Posted: 17 December 2017 at 6:33pm
Originally posted by Conanski Conanski wrote:

Originally posted by Jo bg Jo bg wrote:

Measuring the rig inside yesterday

I have seen this type thing before so I'm going to throw this out there. The only way to measure indoors and make any kind of reliable comparison between different cabs/drivers is to setup the test system and a speaker, measure, then move that box out of the way and place the second box in the exact same spot. Absolutely nothing else can change. If that is what you did then great you can consider the comparison valid, just be aware you are measuring the speaker and the room.. not just the speaker.
If you simply setup the two speakers in a room and are comparing left to right traces without moving  anything the test is invalid, if the mic was moved the test is invalid, if somebody else came into or left the room the test is invalid,  if a door was open for the first sweep and closed for the next the test is invalid. Get the idea?

Perfectly put 
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