S17 - Constant directivity dipoles part II - diyAudio
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Old 22nd February 2011, 10:52 AM   #1
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Default S17 - Constant directivity dipoles part II

Continuing the saga... the S16 which utilise waveguides provides great directivity, but the problem being lack of uniform rear radiation. I have decided that it is not a good compromise. There is something missing.

So here I want real dipole radiation front and back, and uniform to very high frequencies. This can only be done with extemely short front-to-back distance.

Click the image to open in full size.


The "tweeter" used is TB 3". It allows low crossover frequency.

The directivity plot was measured indoor so there is room for improvement when I take it for outside measurement later.

indoor, 1m, normalised
Click the image to open in full size.

same graph, contour format
Click the image to open in full size.

I think this is very acceptable. Minor widening of directivity at 1.8khz, but smooth out.
To put things in perspective, a sample of typical back to back dome implementation:

My own s9, outdoor, 1.9m, back to back dome, normalised
Click the image to open in full size.


Obviously the fullrange do not have a resolution like 1" dome can give. Currently this is not bothersome but we'll see over time.
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Old 22nd February 2011, 01:29 PM   #2
6.283 is offline 6.283  Germany
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Ah, there it is again: The "klingon battleship" polar spesponse of the 1". I really had to laugh the other day
The front of the 3" looks good but the back radiation will suffer I guess.
Where do you cross over and what filter ?
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Old 22nd February 2011, 09:29 PM   #3
cuibono is offline cuibono  United States
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A little more EQ, and it would be perfect. Looks like it could use a super tweeter though...

Ditto, what is you're XO frequency? And what size driver are you crossing it to?
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Old 22nd February 2011, 10:49 PM   #4
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Hi OP,

The rear chamber of the TB is actually very open due to small Neo magnet. I did not measure it this time, but in the past I did that and measures well:

My S13 OB. Uniform polar response to tweeters at last!

The XO is 1khz, LR4 electrical (it produces 1.1khz LR4 acoustics due to rolloff of the Seas L21)

The next experiment is to lower the xo even more gradually, perhaps 900, 800 etc.
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Old 22nd February 2011, 10:52 PM   #5
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Quote:
Originally Posted by cuibono View Post
A little more EQ, and it would be perfect. Looks like it could use a super tweeter though...

Ditto, what is you're XO frequency? And what size driver are you crossing it to?
The widening at 1.8khz really cannot be EQ'd because it is physical. I'm actually a bit puzzled why that is the case because it should be well in the dipole range. It could be due to the interaction with that minimal baffle.

The midrange is 8", and crossed at 1khz at the moment.


Anyway, I'm going to listen to a pair of ORIONS tomorrow. Very excited !!
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Old 23rd February 2011, 05:16 AM   #6
cuibono is offline cuibono  United States
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Nice! Always good to hear. I think you will be pleasantly surprised by your own work.

The widening polar pattern is a little unpredictable, but so are small dipole drivers. What I would do is EQ it for something closer to a constant power response, rather than prioritizing the on-axis response. I would put a shallow 1 or 2dB dip between 1.1kHz and 2kHz, just to smooth things out a little. Give it a listen, I bet it will be subtle but nice.
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Old 24th February 2011, 09:11 PM   #7
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I listened to a pair of Orions last night. This is a very rare chance in Australia. In fact the owner is an American who brought them over.

I love them and love how they look. So correct and appealing.

Surprisingly the bass was not their best performer. It's the midrange, so natural.

As someone said before "Why do we bother ...."
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Old 24th February 2011, 09:30 PM   #8
SAC is offline SAC  United Kingdom
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Any comparisons you would like to make to your own work? An 8" crossed high to a tweeter on a relatively wide baffle goes against some of your recent design philosophy after all, or are we splitting hairs here?

I am experimenting with the baffleless route myself so would be interested to hear examples of its value.
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Old 24th February 2011, 09:46 PM   #9
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Generally I don't like to comment on "products" but like to discuss approach and topologies. But I'll make an exception on this one

Tweeters
Due to recent experiments with high frequency directivity I paid great attention. Yet there's nothing wrong with Orion's tweeters. They are smooth and coherent to the midrange. They sounded dull at times but I'm 100% sure this is the effect of DSS filter. Perhaps 3.2db is too much, but this is a matter of taste and preference.

Midrange
Nothing wrong. Very natural and clear. No hints of that 5khz metal cone breakup. Reproduced great dynamics on certain material. Pure awesomeness.

Bass
I was expecting much better from Dipole bass and expensive woofers. Did not go low enough, and might be related to the room (floating floor, speaker locations, etc.).

Looks/construction
Simply amazing to look at. Very balanced. Truly beautiful.
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Old 24th February 2011, 10:08 PM   #10
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Which Orions did you hear? The latest model with rear tweeters?

P.S. I have not been able to get on to the Linkwitz pages with my Mac on Safari for about a year now because "the server is unavailable", yet on the Windows computer at work I have no problem. However, I can get cached pages where the pictures are missing!
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