just to let you people know, the Orion++

[ErikdeBest]

I have been visiting linkwitz's website a lot lately to get acquainted with the theory behind dipole loudspeakers. When I accessed the site yesterday I saw, at the first page, there was something different... soon found out it was a update on the Orion speaker, where he added an extra tweeter to make the response over 1.5kHz (look like a) dipole too. I do not know how much you access his site, but he is quite enthousiastic about the modification.

I started with the theory behind dipole woofer, and took it for granted that the middrange baffle was a true dipole, but well, since yesterday I know it is not so. I tried to find out how one can determine at what point dipole operation stops, and found that it must have to do with drivers directionality, but in Linkwitz's explanation he states that the 8" driver starts to be directional at about 558Hz (but still there is a dip at the ~800Hz, and ~1600Hz, as expected for an 8"open baffle...). I could not find a direct relation between the 558Hz point and the 1500hz transition point. So, how does one determine where the transtion occurs?

I will keep reading theory and thinking about it, but if someone wants to jump in with some explanation, or a link, be welcome!

many thanks

Erik

[janneman]

Erik,

Some interesting related stuff here (plus a pic of two of SL..):

http://home.pacbell.net/donwm/

Jan Didden

[Vikash]

http://orion.quicksytes.com/viewtopic.php?t=382

V

[ErikdeBest]

Thanks for the links!

The discussion on the Orion forum seems to be more about the tweeter one should use, and the mounting options. I understand this discussion, as it looks like everybody there already own an Orion speaker. There is one post that asks for some further explanation on the theory behind the additional tweeter, but no reply to it (actually it must be explained already, still I can't catch it). So I still do not understand how one determines where the speaker makes the transition...hmm.. and it won't be this weekend I will understand it from reading Linkwitz's site, as I have an exam on Monday.

More suggestions are welcome

I wish all a very nice weekend, in Holland we finally have some cold!

Erik

[reins]

Quite interesting, especially as SL argued for some time that a dipole tweeter is not necessary.

I checked the effect with my dipoles and a tweeter I had laying around. I feel a positive effect on the sound. Soundstage seems to be more consistent. It is at least positive enough to order another pair of Seas tweeters.

Stephan

[tktran303]

SL seems positively delirious with his latest mod.

And going by the Orion forum, I cannot believe my eyes.

It may be be a "compromise" to use the 27TDFC, but it's ok to surface mount the T25CF002 tweeters?

Can anyone spell Groupthink?

[DSP_Geek]

Originally posted by tktran303
SL seems positively delirious with his latest mod.

And going by the Orion forum, I cannot believe my eyes.

It may be be a "compromise" to use the 27TDFC, but it's ok to surface mount the T25CF002 tweeters?

It could be SL surface mounted the second tweeter as a quick hack to check out the idea before committing serious woodworking time to it. The picture on his site shows the mounting for the rear tweet looking like a jury-rigged setup, not a finished product.


Cheers,
Francois.

[Davey]

Originally posted by tktran303

And going by the Orion forum, I cannot believe my eyes.

You probably shouldn't stop by there anymore then. We group-thinkers might all move at once and run you over.

Davey.

[ErikdeBest]

Hi all

Still no specific reply on the transition between dipole and 'monopole'... I was thinking about it today, I could not concentrate much on my exams.

In theory the 8 inch unit should get directive at about 558Hz, but actual measurements by Linkwitz show that there is still a null at ~800 Hz, and some at 1600Hz, both being a direct consequence of the 8" baffle dimension (34400 / 2 * 20,3 ~850Hz). So, although theoretically directive, the baffle still performs quite 'dipole like' (what is a good thing) above the 558Hz. Point is, at 1400Hz a (steep) crossover comes in, and everything above is played through the tweeter. I was looking at pictures from the Seas millenium tweeter, and as with almost every tweeter, it's back is closed. So, a question arises: the woofer moves air both at the front and back of the baffle, both eventually cancelling each other. But, how about the tweeter, if it's back is not open? Where does the (very small amount of) air moved at the back of the diapraghm go? I would say that a closed tweeter could never achieve a dipole spread of sound So, the transition of the speaker is not completely explained by the directivity of the 8 inch unit, but happens at the crossover point on the tweeter?!

I do have 4 6,5 inch midrange (TPC 182 from Gradient) units and 4 ribbon tweeters at hand (got them very cheap), with which I want to experiment a dipole midrange baffle (woofer on extremes, ribbon in the middle, the extra ribbon mounted on the rear). The ribbons should be used above 2500Hz, so I want to use this as (minimum) crossover point. The directivity of the 6.5 inch units should start at a higher frequency than the 8 inch units, so this helps, hopefully, in preserving the dipole character.

When I am further with project (number 1245894 on my to do list) I will report back!

Erik

[tktran303]

Hi Davey,

That's for sure. That's why I posted that comment here. Wouldn't have stood a chance over at that forum.

From his "has the website been hacked" to "let's order all the Millenium tweeters from Zalytron before the price goes up", SL cetainly has the capability to stir up emotions very quickly.

Don't get me wrong, I have been interested in the Orion for a long time, and it is on my list of "Must-listen" speakers, but the latest post has me scratching my head.

I would certainly hope he provides a mod to the ASP to allow the pair of tweeters to run off a single amplifier channel. 2.5ohm is too low a load for most amplifiers, and an extra pair of channels is just wasteful.