Two Ribbon tweeters to improve horizontal dispersion?

[goldyrathore]

Hi,

I was wondering whether we can vertically stack two ribbon tweeters to improve the horizontal dispersion. One tweeter can fire straight whereas the other can fire little to the inside (turned towards the listener). Will this always translate to a wider soundstage and better imaging? Has anyone tried this or is the idea too silly.

Thanks in advance,
Goldy

[sreten]

The problem with ribbons is usually vertical dispersion, and
stacking them is an expensive way of making this worse.

sreten.

[goldyrathore]

Hi,

a> If the vertical stacking limits the vertical dispersion then how do other planars manage to produce vertical dispersion. I m talking about electrostats and Magneplanars. They are so huge.

b> If I am willing to sacrifice vertical dispersion by stacking then does all the advantages of my original question hold good.

Thanks in advance.
Goldy

[tiroth]

a) Planars are a planar source. Ribbons are a line source approximation. Also, when your driver is 4'+ tall, you don't really need the vertical dispersion, do you?

b) Horizontal dispersion is already excessive in most designs. How do you hope to improve it by doing this?

[Lusso5]

Originally posted by goldyrathore
Hi,

a> If the vertical stacking limits the vertical dispersion then how do other planars manage to produce vertical dispersion. I m talking about electrostats and Magneplanars. They are so huge.

b> If I am willing to sacrifice vertical dispersion by stacking then does all the advantages of my original question hold good.

Thanks in advance.
Goldy

A - you answered you're own question - they are huge.

Instead of stacking two planars, which will cause interference cancellation, just buy a longer single planar.

B - As Sreten said, the problem with planars is the vertical dispersion. You wouldn't want to sacrifice any more. Just buy a longer planar.

You might want to puruse these:

B&G DIY Planar Forum

B&G DIY Resource Page

[Sjef]

The vertical dispersion of a ribbon, especially the larger ones, can be a problem for the in room response of a speaker system. If the difference in dispersion between the midrange and the tweeter is too big in the crossover range (and one or two octaves above that, depending on the crossover slope) you will get the feeling that there's something wrong, because you are missing some ambient information.

A possible solution for this is to add another tweeter on top or on the back of the speaker. In case you use a ribbon also for this second tweeter it is best to put the ribbon horizontally instead of vertically. Try it with a cheap dome tweeter and a L-pad and try various positions and crossover points, it helps. I have done it with a Jordanow horn ribbon combined with a 25mm eton dome tweeter I had lying around at the back and a friend of mine has done it with a Raven R2 and a very cheap Visaton 15mm polycarbonate on top of the speaker. Combining two tweeters in the same radiating direction didn't work for obvious reasons.

[qi]

How about a waveguide like the one that the Alcon RBN601 uses?

[sreten]

Originally posted by goldyrathore
Hi,

b> If I am willing to sacrifice vertical dispersion by stacking then does all the advantages of my original question hold good.

Thanks in advance.
Goldy

IMO you will barely improve horizontal dispersion, and as I
alluded to likely cause more problems than the non-problem
you are trying to improve.

The horizontal dispersion of ribbons is usually excellent.

A longer ribbon is not an improvement either, unless its very long.

The use of off axis filler tweeters is a different can of worms IMO.

sreten.

[goldyrathore]

But I read that ribbons had a poor horizontal dispersion as compared to their dome counterparts and this fact was responsible for its small sweet spot and inability to portray a wide soundstage.
Pls explain. This is contradictory and confusing.

Thanks,
Goldy

[sreten]

Originally posted by goldyrathore
But I read that ribbons had a poor horizontal dispersion
as compared to their dome counterparts and this fact was
responsible for its small sweet spot and inability to portray
a wide soundstage.
Pls explain. This is contradictory and confusing.

Thanks,
Goldy

They have excellent horizontal dispersion as they are
usually narrower than the size of a dome.

The vertical dispersion is poorer than a dome as they
are usually several time the size of a dome in length.

"Inability to portray a wide soundstage", simply not true.

"Small sweet spot", not true either.

But the longer the ribbon the more you lose when you
stand up unless the ribbons are extremely long.
You lose a lot standing up with 2ft ribbons c/o at 700Hz.

Would help if you said the type of ribbons we are discussing,
e.g. a 4" treble unit ribbon, or a 4ft midrange/ treble unit.

The units that might have the problems you describe would be
a wide flat planar driver, e.g. 6"x4", but these are not ribbons.

sreten.