New planar drivers at Parts Express

[OllBoll]

Originally Posted by emailtim

The only off-axis SLIM-8 results (that I have seen) appear to be from covering up the outside slots on a wool/felt baffle. Wouldn't this have the same effect on the normal 8's ???

I can verify that the same trick works on a normal Neo8, it does extend the high end a bit. I have gotten more smooth results with a less wide baffle though, on the order of 10 cm or less. This 30 cm baffle is a bit extreme but I wanted to specifically test the extreme case in that measurement.

With a smaller baffle that covers ~ 10 cm and that covers the outermost two holes we get the following on a Sounderlink Neo8 which is basically the GRS wide 8" but more expensive, more distortion and less consistency*. (*My guess based on the consistency of the slims, probably similar for the other planar drivers from GRS)

Note that even with those tricks the top end at 10 khz and above is still worse than the slim. Not by a huge amount sure but a bit worse.

There is also the fact that the wide 8" is well, more wide Probably not an issue for most but I'm building a dipole and in this case it is very advantageous to have the slim design. A dipole with a hard baffle will create a null on the other side, as can be seen in the measurements. The bigger the baffle relative to the radiating area the bigger the null. It's not a huge null but it is there from 4-7 khz and no amount of wool I have thrown at it has eliminated it.

The slim driver has a lot less baffle but the same radiating area, so this null is pushed higher in frequency which is a good thing. I believe with some tweaking of the wool baffle (mostly reducing width or curving it to create a mini-waveguide) and with more drivers I can eliminate the null with the slim driver.

[mlee]

Originally Posted by bwaslo

Has anyone measured the little 3.5" tweeter?
Dayton Audio PTMini-6 Planar Tweeter 6 Ohm
Sensitivity doesn't look great, no idea about distortion. But I'm wondering how a couple of these would do with 8" planar slim on either side?

I measured them and even in a full line array your looking at around 4.5khz at best distortion wise. Horizontal dispersion is excellent though.

[mlee]

Originally Posted by ErikdeBest

Spoke to the OH yesterday and just placed my order for enough Slims to make a stereo pair of floor to ceiling array. Since seeing StigErik's succes with the RD75, years ago, I have been willing to do something similar, and i think that currently it is only these Slim units that can actually come close to the RD75.

This is gonna be cool!!

[ltlee]

Its great to find this thread. I'm think of getting the GRS PT6816-8 with 4 per side hopefully to get a low cut off around 400-500Hz so most vocals will be on the planar and coupled with 2 Dayton Audio RS225P 8 inch. This is my first planar experience/built so I have a few questions if you can help me with.
1) I picked the GRS slims as both lower and upper FR seems more even than the wider versions. Would this planar sound more like a metal or textile dome? I tend towards textile as they seem to sound more realistic/natural.
2) Related would be if AL or paper cone woofer be better tonal match.
3) I was thinking of using 2x 8 inch in a slim enclosure but to get low bass would have to be enclosed. Would the transition between enclosed bass to open planar have audible tonal change? Should I go OB with 2 10 or 12 inch instead for best tonal consistency?
Thanks in advance for your help!

[mattstat]

You're asking for opinions, and that's what I'm giving, along with some generalities and assumptions going from limited information in your post. My thoughts may be different than yours on various goals, so none of this is set in stone or applies to all speakers.

I think that cross point may be stretching things a bit. While frequency response is relatively smooth down there, the distortion plot in post 97 of this thread shows rapidly increasing distortion below 800 Hz (below about 600 Hz it exceeds the values seen across the rest of the driver's range). How much distortion you're willing to live with will help make the decision on the crossover point. Some people see increasing distortion at the bottom of a tweeter's range as tolerable because they value some other performance aspect more. A very steep crossover should help if you want to push it.

Many people like aluminum cone drivers for their increased detail retrieval. That aspect would likely be a better fit with the planar. Most aluminum cones have pretty nasty breakup regions that must be avoided though. These are typically in the 2.5-5 kHz range depending on size and design. Probably won't be much of an issue for what you're planning unless you use a shallow crossover and pick the wrong midrange/woofer. Paper cones tend to have smoother frequency response, but a more mellow presentation. If that's what you value more, that may sway your choice.

You didn't say what kind of enclosure you're planning. Two 8's in a sealed enclosure typically won't go that low (depending on your definition of low). Open baffle can get complicated pretty fast - many choices and trade-offs have to be made there. They aren't as simple as they first appear if you're going for high performance and/or high output. It's not so much the tonality that's the problem in this scenario, it's the polar response/dipole response on top vs. monopole bottom end. The lower your crossover, the better from this standpoint.

[drjlo]

Originally Posted by ltlee

Would this planar sound more like a metal or textile dome?

Haven't heard the GRS but Neo planars sound far more like textile than metal domes to my ears.

I would also try to stick with open baffle for bass, and it so happens SB Acoustic is now selling 12" and 15" paper woofers designed for open baffle. At least their graphs look pretty good on top-end response.

SB Audience :: BIANCO-12OB150

Audience Open Baffle Woofers: Madisound Speaker Components

[ltlee]

Originally Posted by mattstat

You're asking for opinions, and that's what I'm giving, along with some generalities and assumptions going from limited information in your post.

Thanks for your thoughts. I had build 2 15in RSS390HF in a sealed 3 cf bass box for use as sub in my HT. I'll use that in conjunction with the planars to experiment with crossover point and transient from bipolar to unipolar. Part of my reason to try crossover at 400-500hz is to minimize the transition in voice range.

[mattstat]

That'll make things easier. For my own projects, I also like to prototype early to get a feel for what works in reality vs. what looks good on "paper". Having extra drivers and amps around makes things go a lot faster. I hope your project goes well.