[guest60106]

Has anyone ever considered using this as a low cost dipole tweeter? The efficiency is low @ 78db but if it was an active system that would not be an issue. Cross it around 1.5K to 2K?

I am not sure. Am I missing somthing?

http://aurasound.dev.squirreldreams.com/sites/aurasound.dev.squirreldreams.com/files/NSW1-205-8A%204-12-11.pdf

[JohnR]

I think the issue as a dipole is the "tunnel" behind the cone will create a resonance. I'm not sure how much, I have one here and can try measuring it if it's of interest.

[Æ]

I am not sure. Am I missing somthing?

Are you sure it is a dipole? From what I can see in the drawing, it doesn't appear to have an open back.
The measured frequency responses are always taken from the front side. If you want true bipole or dipole, mount two tweeters, one on the front and one on the back.

[guest60106]

I think the issue as a dipole is the "tunnel" behind the cone will create a resonance. I'm not sure how much, I have one here and can try measuring it if it's of interest.

It would be of very much interest John, as well as any experience you have with this driver. I am considering it for an OB design for use from 1.5k to 2k up. I am fairly sure it is an open back design. I belive it is the same ring neo design as the NSW2-326-8AT. According to Madisound that is an open back design hence the screen covering the motor and inverted dome rear. I could be wrong. I am not sure what the ring tube would do to the rear frequency response but it would be interesting to find out.

Thanks
Matthew

[JohnR]

Yes, it's open with a screen on the back. I'll try measure it today.

[JohnR]

Heck, you got me curious. Unfortunately, it doesn't look that promising. This is just a rough measurement - I suspended it from a couple of chairs, and put the mic 20cm distance, so there are some artifacts in the measurement. Here is the on-axis (red) and 90 degree (blue) measurement:



Here is on-axis and 180 degree measurement:

[JohnR]

Now that I look, the resonance shows up even when you put it in an enclosure:



The NSW2 is better behaved (in an enclosure) but needs EQ. I'll try measuring it open.

[D OB G]

I believe Linkwitz uses the NSW2 to universal acclaim in his Pluto (equalized).
I’ve tried it: in an enclosure, open at the back, and also with the screen removed.
I didn’t have success.
-very inefficient
-needs a lot of EQ
-most importantly for me, it can’t go very loud at all before distorting (I don’t know how L gets away with it).
-poor dynamic range, both up and down.
Maybe a number of them would work in a line array.

Regards,
David

[guest60106]

Nice work John. Am I correct in thinking it may be crossable at say 4k with a 24db filter? My active is a 4th order LR. Or possibly a bit lower with a passive notch filter tacked onto the driver itself? If so would the notch filter tame the distortion at resonance as well? I need to invest in measurement software so I can gain a better understanding of what I am dealing with in all design cases. I really appreciate your work.

Matthew

[JohnR]

Hm, 4k is a long way from the original goal of 1500... you have a lot more options if you are crossing that high. What woofer (or mid) are you using?

[JohnR]

I believe Linkwitz uses the NSW2 to universal acclaim in his Pluto (equalized).
I’ve tried it: in an enclosure, open at the back, and also with the screen removed.
I didn’t have success.
-very inefficient
-needs a lot of EQ
-most importantly for me, it can’t go very loud at all before distorting (I don’t know how L gets away with it).
-poor dynamic range, both up and down.
Maybe a number of them would work in a line array.

I thought the NSW2 behaved quite well, once equalized. However that was a small system, I don't think I would use it in my main system. Also, still just a prototype 

http://www.audiocircle.com/index.php?topic=100112.0

[JohnR]

Here is the NSW2 in free air. On-axis and 90 degrees:



On axis and 180 degrees:



Pretty similar behavior to the NSW1 but the peak is lower in frequency.

[guest60106]

Hm, 4k is a long way from the original goal of 1500... you have a lot more options if you are crossing that high. What woofer (or mid) are you using?

John,
I have narrowed the mid/woof down to 3 options. All have their advantages and disadvantages. I will get to that in a moment. I like the use of a dipole tweeter, however I am still in the design/ testing stages so I am limiting the tweeter budget as much as I can until I define a direction. Most dipole tweeters are out of the budget for this build so far. Also, the size constraints of the panel design (read height) are limited so a large area tweeter plate (larger than a couple of inches in diameter) will upset the panel layout and I would have to make it taller. Not out of the question but I would rather not. Using 2 tweets back to back (180 out of phase) does offer the advantage of separate volume controls on each using a 4- way active system as long as the 4th crossover point is independent. This is what I use now with great success. I can set the front and rear tweeters to identical crossover points and slopes, then by attenuating the volumes independently, move the sound stage forward or backward as needed. The disadvantage is a complex system with lots of wires and amps.
The mid/woof options are as follows.
Anarchy 6.5 - This woofer is compact, will by far move the most air, has the force factor, Qts, Qms and excursion I am most comfortable with for OB use and is the most cost effective. The drawbacks are the need of a low crossover point for the tweeter and limited information on the Anarchy’s use. (This is the reason for this thread on the Aura.)

http://www.diycable.com/main/product_info.php?products_id=538

Seas U18RNX/P – Although this drivers specs are not ideal (IMO) for OB, they are fairly good. The driver does have a really nice response all the way to 4000 and I think would be really easy to work with as far as a tweeter. The lower BL and excursion (than the Anarchy 6.5) would limit the power handling and high pass point. Crossing it at 200-400 would likely help power handling quite a bit. But, I want to be careful not to limit myself too much with the integration of the bass to mid just like I am trying to avoid with the mid to tweet.

http://www.madisoundspeakerstore.com/seas-woofers-6-7/seas-prestige-u18rnx/p-h1571-7-curv-cone-woofer/

Alpair 10 – This driver need no introduction. I can ditch the tweeter altogether, the complexity of the system goes way down and the baffle height is no longer an issue. If you could see what I have in my living room now for components, you would understand why I haven’t shown this option to my wife because if I did she wouldn’t let me go any other way.

http://www.madisoundspeakerstore.com/approx-6-fullrange/markaudio-alpair-10-grey-6-full-range-gen-2/

There are other considerations. I will cross them when I get to them. Right now, since I am new to OB design, I am getting very close to committing to a design that I can build, test and play around with to learn more. This is the reason to keep the cost low is I will surly make design changes based on what I learn from this experience.
Matthew

[guest60106]

I just noticed that this just went on sale @ Madisound so this is also a viable option.

http://www.madisoundspeakerstore.com/seas-woofers-6-7/seas-prestige-p18rnx/p-h1350-7-poly-cone-woofer/

MLC

[JohnR]

All very interesting. I also am interested in reducing the "ways." To that end I bought a pair of Seas FA22RCZ, perhaps that is a driver you may want to look at - ?

I'm wondering if you can use the back to back tweeters you have now without the independent channels - ? Honestly I'd skip the Auras. The Neo3 is another option but the price is getting a bit silly, they are nearly twice the price from two years ago. I'm much happier with mine since I made a baffle for them but others disagree and prefer them "naked." I have yet to find out how going to a FR changes things.

[guest60106]

All very interesting. I also am interested in reducing the "ways." To that end I bought a pair of Seas FA22RCZ, perhaps that is a driver you may want to look at - ?

I'm wondering if you can use the back to back tweeters you have now without the independent channels - ? Honestly I'd skip the Auras. The Neo3 is another option but the price is getting a bit silly, they are nearly twice the price from two years ago. I'm much happier with mine since I made a baffle for them but others disagree and prefer them "naked." I have yet to find out how going to a FR changes things.

Interesting you should mention that driver. I would like to know your take on the sound as that was the driver that got me interested in this particular design to begin with. I originally designed the panel utilizing the FA22RCZ for more than one reason not the least being the absence of a tweeter. I later dropped it from the design because of the size. Where I am at now with the complexity I should probably go back and re-visit this option. I will take a look at the panel I have done in CAD and see. Right now I have the panel down to 25” wide by 33” tall and angled back by 5 degrees. The bass section utilizes 4 10” woofers in a “pseudo” u frame (meaning the side wings are triangular shape getting narrower towards the top).

MLC