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Old 12th September 2012, 03:00 AM   #41
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Nice work on the measurements Goran.

Quote:
Originally Posted by 5th element View Post
It's also interesting to see how the 2nd harmonic shoots up below 800Hz at the higher drive levels, this could possibly be due to the non symmetrical aspect of the surround, clearly an xover at around 500Hz would suit the driver well, but subjectively it might sound better with a little bit more 2nd order in the mix crossed over lower - of course this is only a problem if you listen loud!. It'll be interesting to see how high up the woofer can be used.
I've got the 10F 77 25 10 KAP here and it will easily handle crossing at 500hz 2nd order. There's a cone break up at 2.4Khz but distortion is well behaved around here. Goran has the 10C model which has a smaller motor but I expect that would only really affect low end performance significantly so he should see similar results. My testing shows you could use this up to around 800hz as a sensible max if using 2nd order. I've got them crossing in a 4 way to an 8" at 120hz and then the 8's hand over to the same 5.5" AT mids Goran is using at 650hz and this works extremely well.

The AT drivers really are excellent and always very predictable. I can't say the same for the Accutons I've been playing with lately, they're excellent of course but without work they lack texture and body.
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Old 12th September 2012, 06:45 AM   #42
gornir is offline gornir  Sweden
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Quote:
Originally Posted by ShinOBIWAN View Post
Nice work on the measurements Goran.



Goran has the 10C model which has a smaller motor
Thanks!

It's funny when you say I have the smaller motor, because it's freaking "huge". I can only imagine how massive your 10F model must be

Click the image to open in full size.

I've haven't decided a cross-over point between the 15H and 10C yet, because I need more measurements and simulations first, but I will most likely take the baffle step and flour bounce in consideration.

That would mean something like 300-500Hz as a starting point for the cross-over point. I also want to, if its possible do a 2nd order topology for the whole design, but that depends if the RAAL can work with a 2nd order @ approximately 3kHz.

As soon as the cabs are finished I will hook up the loudspeaker to my DEQX and play around with different cross-over point in order to get the feel how the drivers behave before I build the passive version.

I got the feeling this will be a long build....

At the same time I'm building two new versions of the Revelation Two – Monitor, using my favorite ScanSpeak tweeters D3004/6600 and D3004/6640.

Essentially it's the full ScanSpeak version of the Sequence Two – Monitor using the same cross-over topology and technique.

Regards

/Göran
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Old 12th September 2012, 06:55 AM   #43
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Quote:
Originally Posted by 5th element View Post
The peak at 1.8kHz is a bit more of a concern though. I'd suggest putting the driver on an open baffle, putting the mic in front of it, then swap to the spectrum analyser in ARTA. If you test the driver at 1.8kHz, you can then watch the 2nd harmonic level whilst altering the drive level, you'll then be able to see how and when the peak appears. If it does appear you could then try touching the various parts of the basket etc to see if the peak changes at all.
Yes, I will investigate this further. The cabs where heavily stuffed with sheep wool and perhaps not fully air-tightened when measured or perhaps a loudspeaker cable rattled or something (happened before for me )

It could also be a built in behavior for the driver itself. Look at the mid-woofer version of the 15H, which has a three times higher 2nd order harmonic peak @ 1.25kHz for the same SPL level.


Regards

/Göran
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Old 12th September 2012, 03:07 PM   #44
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Yes, except that the peak in the 15H is there because of a resonance, it corresponds to a large dip in the frequency response and a wiggle in the impedance plot too, this is nothing unusual, some SEAS, Scan and SB acoustics drivers have this too and I think I read somewhere that that is due to a surround resonance. Again this shows up at all drive levels, as you'd expect.

Looking at the other driver though, one has a peak at 3kHz and one does not. Again, this is strange. If the soft parts are all the same, which they should be, then you'd expect resonances to occur in similar places. You wouldn't have one driver showing a peak at x frequency and then one not. If one didn't then as the driver designer you'd want to figure out why one doesn't and make sure that they all don't. Maybe it's not supposed to be there and during shipping something got bumped or knocked out of alignment. I know that the Skaanings' are supposed to be very approachable when it comes to discussing their products, perhaps they might be helpful in saying where the problem is likely to be coming from. Maybe you're not as interested in this as I am, but at the price level and level of quality we're talking about here, I would not expect there to be driver to driver consistency issues.
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Old 12th September 2012, 03:16 PM   #45
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I thought I'd just add that it might be worth doing some sweeps at 48 steps per octave. I know this takes forever, but when you've got peaks appearing in places it might help shed some additional light on the situation. 12 points per octave is usually great, but if there are small trouble zones, it can make things appear worse then they are, or sometimes miss them entirely!

Usually, if doing a 48/octave, I'll increase the duration of each tone burst too to help increase the accuracy and average out anything random that could be cropping up. Again this takes a while, but I'll set it going then go watch a TV program or something Come back and it's done. Of course, you could just limit the bandwidth to say 800-2500Hz etc to look at one area in greater detail.
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Old 12th September 2012, 04:18 PM   #46
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Quote:
Originally Posted by 5th element View Post
Usually, if doing a 48/octave, I'll increase the duration of each tone burst too to help increase the accuracy and average out anything random that could be cropping up. Again this takes a while, but I'll set it going then go watch a TV program or something Come back and it's done. Of course, you could just limit the bandwidth to say 800-2500Hz etc to look at one area in greater detail.
Yes, I will redo the distortion measurements when they are in place in the real enclosure with proper damping and cable mounting etc. I will also do some sweeps with greater detail in the troublesome area.

I don't think this is a show stopper by any means, but it never harms to be thorough when you discover odd behaviors.

Regards

/Göran
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Old 12th September 2012, 06:08 PM   #47
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Well indeed it's my curiosity more then anything and then if you do find the cause perhaps you could fix it.

I mean with XT25s that measure to spec, at least with the ones I've got, I could lower the distortion by gently pushing the phase-plug to the side. Obviously once I Iet go the performance returned to normal and this wasn't a design fault as per say, it's just how they are.
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Old 23rd September 2012, 09:27 PM   #48
gornir is offline gornir  Sweden
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Default Sequence Three – Grand Reference Construction Update3!

Here's a small update of the build progress!

The enclosure build is progressing as planned and the first box is finished. Some minor adjustments remain, but the build slowly beginning to nearing its final stage.

The next series of measurements I will publish is for the 10C 77 25 10 KAP woofer, thereafter followed by DEQX measurements and some listening evaluation of the driver's capabilities.

For further details and pictures see:

Sequence Three – Grand Reference Construction Update3!
RAAL 140-15D Measurements!
AudioTechnology 15H521206SDKM Measurements!


Regards

/Göran
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File Type: jpg ST-GR_EB_Picture40.jpg (77.8 KB, 177 views)
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Old 24th September 2012, 10:29 PM   #49
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Those are coming along very nicely
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Old 25th September 2012, 04:04 AM   #50
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Stunning work Goran. Your blog is an enjoyable read. Have you compared the 15H midrange vs midbass side by side(listening test)?
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