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Old 10th September 2012, 08:17 PM   #31
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Hello Göran,

That's a nice speaker project that you're doing, I'm busy with a similar project.
For the last two months I'm busy with designing the crossover at a very slowly pace: change a little, listen a lot, now I'm at version 30-something of the crossover
The mid and the tweeter are crossed at 3K, the accuton mid is 2nd order electrical and the Raal ribbon 3rd order electrical. This gives 4th order LR acoustic for both and perfect phase, nice
I hope to have them finished soon...

Grts,
Danny
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Old 10th September 2012, 08:32 PM   #32
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Superb Danny. Maybe you could create your own thread about the build?

Greg
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Old 10th September 2012, 08:35 PM   #33
gornir is offline gornir  Sweden
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Quote:
Originally Posted by danny_66 View Post
Hello Göran,

That's a nice speaker project that you're doing, I'm busy with a similar project.
For the last two months I'm busy with designing the crossover at a very slowly pace: change a little, listen a lot, now I'm at version 30-something of the crossover
The mid and the tweeter are crossed at 3K, the accuton mid is 2nd order electrical and the Raal ribbon 3rd order electrical. This gives 4th order LR acoustic for both and perfect phase, nice
I hope to have them finished soon...

Grts,
Danny
Congrats!

Very nice looking speakers you have there.

Regards

/Göran
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Old 10th September 2012, 08:37 PM   #34
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Thx Göran!

Hi Greg,
Yes, I'll start a new thread is soon the crossover design is stabilized
Grts,
Danny
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Old 11th September 2012, 01:50 PM   #35
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Originally Posted by Silent Screamer View Post
As I say the results are far from being conclusive... They aren't even based on any kind of measurement. Once I have them properly set up I can then give them the serious consideration the deserve, but for now they seem to sound better at the low end of town, but who knows once they are facing in the right direction. Yes they are the same pads as the ones I got.
Tonight I added a second 10" in parallel and stood the RAAL up right and put on the pads. Been listening between 2500-3000. No where near as much detail as set lower, but much easier on the ears, also reduces the audible hall echo massively (listening to Hell Freezes Over).
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Old 11th September 2012, 03:19 PM   #36
gornir is offline gornir  Sweden
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Default AudioTechnology 15H 52 12 06 SDKM Measurements!

Hi,

New mid-range measurements!

Sequence Three – Grand Reference -- Construction Blog
AudioTechnology 15H 52 12 06 SDKM


The next driver measurements for the Sequence Three – Grand Reference design is the AudioTechnology 15H 52 12 06 SDKM. This is the pure mid-range version of the 15cm AT driver.

The mid-range is an over-hung version with a special mid-range surround for optimized frequency response. Measurements for the under-hung mid-woofer can be found here:

AudioTechnology 15H 52 06 13 SDK

If we compare the two different versions we can see that the mid-range version both have a more linear frequency response as well as lower distortion throughout the mid-range drivers usable frequency range.

Frequency response comparison:

Picture 1:

Blue = 15H 52 12 06 SDKM (mid-range)
Red = 15H 52 06 13 SDK (mid-woofer)

Note! The SPL is normalized. They don’t have the same sensitivity.

The dip in the frequency response at 1.25kHz for the mid-woofer version caused by the cone-edge resonance is completely eliminated with the specially constructed surround of the mid-range driver.

To be honest, this dip in the frequency response is more of a cosmetical nature rather than technical, since it doesn’t have a large impact on the sonic performance of the mid-woofer.

The mid-range is perfectly usable up to about 3-3.5kHz and my goal is to use it up to 3kHz +/- 200Hz, where it’s crossed-over to the RAAL 140-15D ribbon tweeter.

Simulations, measurements and listening test will determin which cross-over point and filter topology to use, LR2 or LR4? If it works I would like use a shallower sloped filter e.g. a second-order LR, since I often think such filter topology sounds better if it can be done properly.

Time will tell what’s possible and feasible.

Distortion:

Picture 2: = 15H 52 12 06 SDKM (mid-range) @ 1m 90dB
Picture 3: = 15H 52 06 13 SDK (mid-woofer) @ 1m 90dB

As can been seen the distortion is higher for the mid-woofer version when tested at medium-high levels.

Summing up!

This mid-range driver from AudioTechnology delivers top notch measurement performance without any surprises as nasty cone break-ups, odd frequency response or distortion problems.

I think the mid-range will complement the RAAL 140-15D perfectly!

For further detailed measurements see: AudioTechnology 15H 52 12 06 SDKM

Regards

/Göran
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Old 11th September 2012, 03:57 PM   #37
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Interesting driver, it's interesting that that peak at 4k in the 2nd harmonic is completely absent at 85dB, but shoots up at 90 and 95 and then one of them with a peak @ 2k @ 95dB. It's like something is starting to resonate somewhere that was otherwise static at lower SPLs. Was anything audible happening when the peaks appeared? I suppose it could be something in the room/set up, resonating, I have had that happen in the past.
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Old 11th September 2012, 06:02 PM   #38
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Originally Posted by 5th element View Post
Interesting driver, it's interesting that that peak at 4k in the 2nd harmonic is completely absent at 85dB, but shoots up at 90 and 95 and then one of them with a peak @ 2k @ 95dB. It's like something is starting to resonate somewhere that was otherwise static at lower SPLs. Was anything audible happening when the peaks appeared? I suppose it could be something in the room/set up, resonating, I have had that happen in the past.
Yes, I was a bit surprised myself by the rise of 2nd order harmonics at higher SPL:s. Subjectively I couldn't hear any strange when the sweep where performed.

The first peak at 4.2kHz corresponds to the first peak in the frequency response, but the rise of 2nd harmonics @ 1.8kHz for 95dB I cannot explain right away.

I you look at the much higher AT 15H mid-woofers 2nd order peak @ 1.25kHz and its still a very nice sounding driver.

This is something I will follow up when it's mounted in the final enclosure and not in the test enclosure. I wouldn't worry to much though, because the 2nd order harmonics usually isn't that bad sonically.

Regards

/Göran
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Old 11th September 2012, 08:01 PM   #39
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Hi Göran,
Those AT mid drivers measure very nice
They'll make a nice match with the Raal, both very low distortion.
With my accuton mid I noticed that the inside of the box needed an irregular shape to avoid resonant peaks or standing waves.
So the back side is made of wooden panels in 45degree angles, in the middle of the picture you can see the back panel.
A useful utility that I used for calculating the box dimensions is boxnotes, it helps you with getting golden ratio dimensions.
Grts,
Danny
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Old 11th September 2012, 11:28 PM   #40
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I'm not really worried about it, the peak at 4kHz only shows up in the 90dB measurement, so even with a 2nd order LW slope @ 3kHz you'd need something like a nominal level of around 93dB for it to even show up and this is quite loud.

Yes the peak does correspond to the small peak in the poly cone, but cone issues usually show up whatever the drive level.

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.

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.
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