Raal Omni Discussion

[JonMarsh]

Thank you Aleksandar for your detailed post and reply! It gives me much to think about!

And I wish you the best of luck solving your development issues!

Warm regards,

Jon

[dlneubec]

Hi Aleksandar,

Thanks for clarifying what it is you are doing. I thought the ribbon was between the two cylinders firing forward and/or a dipole. But now I see how it works as a side firing tweeter mounted inside one of the cylinders, firing toward the other cylinder, while maintaining time alignment with the midrange drivers. I think this is a brilliant idea and one I intend to experiment with.

That said, the tweeter is not really omnidirectional, since the horn is certianly going to have much more directity toward the front and rear and increasingly less to the sides. Doesn't it behave more like a bipole tweeter setup than an omni?

[Deward Hastings]

Doesn't it behave more like a bipole tweeter setup than an omni?

That may be good enough, eh? since it would take a couple bounces for the lateral radiation to get to the listener anyway. Depends on the room geometry, of course, but I'd rather *not* have that bounce sometimes . . .

[dlneubec]

That may be good enough, eh? since it would take a couple bounces for the lateral radiation to get to the listener anyway. Depends on the room geometry, of course, but I'd rather *not* have that bounce sometimes . . .

Yes, it may be good enough, however, he also said he didn't favor omni's that reflected sound, and it seems to me that is just what this tweeter mount does. I would think that a Duevel-like solution, with a dome or compression driver in a waveguide or horn, firing up (or down) into a concave cone that forms a 360º horn would give you a truer omni presentation and not have any more reflection invlolved. Of course, that solution presents a whole other set of issues in terms of integrating it with the omni mids, which is one reason I'd like to try this RAAL concept.

You would not have to use 4 mids. You could use two mids and the other tube could be cut in half and used only to form the other side of the horn. I also wonder how this solution would work with a inexpensive neo dome tweeter. I would assume that the horn should boost and extend the lower end performance much like a waveguide, potentially allowing a lower crossover point and perhaps more midrange driver flexibility. Might be worth experimenting with.

[CraigJ]

Hello gentlemen! Greetings from frosty Serbia!

please see the picture attached.

Thanks, everyone!
All the best,
Aleksandar Radisavljevic

Did I miss the picture? Jon, has the "package" arrived from Serbia for the April project?

I kind of thought this would be a fun project to play with and I've never heard an omni speaker (that I'm aware of). Bose?

[ThomasW]

Did I miss the picture?

Don't think one ended up being attached.

[fjhuerta]

Ah, I see. I did an MTM about a year ago using the Neo3pdrw, with the flat square flange that Meniscus (I think) sells. It turned out quite well, but the low end peak was significant. Here is what I measured on about a 10" baffle, IIRC, at 0 and 15º off axis.




I was in the middle of my BaSSlines project when this MTM design was done and I had just finished testing the Peerless HDS in shallow DIY waveguides. It got me to thinking about how the Neo3 might work in one, helping to fill in the 2-8khz area. I figured I would try it that way at some point, but the opportunity hasn't arrived so far. The FR plots that Mige0 posted in his thread don't look too impressive to me, for all that effort.

I know that Dennis Murphy was recently trying to use the Neo3pdrw in a project recently and could not get rid of a big dip in the 2.8khz range. I think he gave up on it and went with an LCY ribbon instead.

Those were my findings, too. I could never get the Neo3 to be completely flat.. it had the strange hump in the lower end and a dip around 3 KHz. I also gave up and got rid of the hump - kept the dip. It wasn't noticeable, unless you knew what to listen for.

[fjhuerta]

By the way, I had a problem when I built my open baffle speakers - in room, I had nasty resonances at around 2 or 3 KHz, IIRC when measuring them using an RTA. When I used them in the middle of the room, the resonance was gone, suggesting that the issue had a lot to do with wall reflections.

Does anyone else has had this same issue?

[Kevin P]

The discussion on the Contrappeso Project has been split into a new thread, here:

https://www.htguide.com/forum/showthread.php?t=39403

[CraigJ]

Hi Dan,

Thanks for being a pioneer with your Raal inspired design. While the family was vacationing in Tucson, I ran out to Madisound and picked up a few of the 3.5" Fountek drivers. Next it was on to Menards for PVC, then home for a very easy build;




Do you have any advice on where to put them in the room for optimal performance? Also, sorry for the silly question, but how do you measure an omni speaker?

I appreciate the assistance and I'm a little shocked at how good these sound "out of the box" (couldn't resist the pun).

Craig

[dlneubec]

Hi Craig,

Cool. I look forward to seeing your results. What are the drivers?

I have found that you can generally measure and optimize pretty much on the listening axis and get to where you want to go. Of course, you will want to look at off axis horizontally and vertically to get a more complete picture.

[CraigJ]

Dan,

Thanks for the assistance. The drivers used are Fountek FE85s and BG Neo 3pdrws (back removed and covered). My original plans were to use the Fountek FR88EX, but the price increase x 8 put the dampers on that experiment. It worked out nicely that the diameter of the pvc exactly matches the diameter of the FR88; cut, stuff and go. Hope there is enough space to breath.

Dr. Linkwitz has a nice diagram on positioning the Pluto, which greatly helped figure out where to place these speakers. I tried measuring 1 meter perpendicular from the mids at tweeter level, but HolmImpulse kept giving me different measurements every other time I tested. I'll try Arta or FuzzMeasure and see if I get more consistent results. Three dogs roaming the room and a neighbor mowing while measuring probably didn't help much. Current xo's are 325hz and 3kz, no eq yet, astonished at how good they sound.

Craig
p.s. I know Aleksandar says to keep the tweeter throat <1/8", so I plan to reduce the number of "slots" in the Neo3 and see if I can measure the differences.