Phase Plugs

[sreten]

Just as an addition to the above :

Some may notice that the opening to the hollow cavity in the phase guide is actually square. The interior of the cavity is round. This eliminates the standing waves that would otherwise rest between the two parallel rims and cause problems with everything else.

Translating the hyperbole I beleive he means it is simply a standard 1/2" socket and :

When the pressure is high, the tip takes on the shape of a bullet with respect to low pressure around it. This in turn sets up a wave guide for the sound that surrounds it. This means that the shape of the tip is constantly being modified in real time by the sound itself. That translates into different phase angle correction at different frequencies!

Utter crap,

sreten.

 

[Flemming J P]

It's funny how you can always make some theory about why whatever is so good.

I also thought that "socket" theory sounded wayyy too easy to be true.

But anyway I like the sound better with the "phase plug", wheter the theory holds water or not.


Why would a steel phase plug increase Qts and lower sensitivity???

I thought the opposite would be the case since the steel phase plug would act like a core, but what do I know

 

[sreten]

I've no issue it may sound better, but the
theory is extremely dubious to say the least.

The pole extension will increase leakage flux,
therefore decreasing flux in the actual gap.
Which will increase Qts and reduce sensitivity.
(As any extra coupling of the coil outside the gap
will not compensate for loss of flux in the gap)

Given the size of the magnet I'd expect the change
to be small, the real issue is the sophistication of the
magnetics design in the driver.
The extra leakage flux will either cause less or more
distortion depending on how well pole piece design
has been optimized.

As a first approximation :

The steel phase plug does form a waveguide of extremely dubious
shape, we all know what a phase plug should look like for treble.

The abrupt ending of the plug will cause frequency response ripples.
(but no worse than the ripples caused by the unterminated
"whizzer" cone. these have been addressed by interjecting
a foam ring between the "whizzer" edge and the cone proper
in other full range twin cone circles)

The phase plug contains a standard Helmholtz resonator,
which will accentuate a frequency range, but do the transient
response no favours. Tuned to a range that is lacking it may
improve apparent treble extension, but not transient quality.

I'd try MJK's full suggestions and TBH don't trust the socket phase plug.

sreten.

 

[Flemming J P]

hey hey I just asked a simpel question and you give an answer that more or less says that I have to skip the fostex and go build a full 3 way system.

So how big difference do you think there would be on a wood plug the same shape and size as the steel one and the steel one?

 

[sreten]

No no , not at all.


If you go by my first approximation (which ignored magnetic
effects so the plug could be just as easily be a plastic socket)

The differences between a wooden and steel socket are in
levels of distortion, which is better I've no idea.

The only difference btween a solid wood phase plug and a hollow
one would be the hemholtz resonator.

The differences beween a cylindrical plain plug and a shaped plug
would be some ripples due to the abrupt edge, and the effect of
the narrower "horn" formed by the cylindrical edge and the cone.

For all of these I've no idea which would sound better.

I also tried to point out there are other tweaks available, of the
ones I know trying to terminate the treble cone edge makes the
most sense, is easily removed / fitted, and looks cool.

See here for the first link I found regarding this :

http://www.10audio.com/fostex.htm

sreten.

 

[Timn8ter]

Let's try to keep this phase plug thing at a reasonable level, ok fellas?

 

[markp]

Thats what happens when you buy speakers from an adult book store!

 

[Flemming J P]

Thanks sreten. I didn't know about that tweak, is just though you pointed out a general flaw with whizercones, without a fix.

Now I something to do for tomorrow

Timn8ter:
Thoose are not phase plugs, they are coat hangers or as pointed out elsewhere d.....s

 

[bbaker6212]

Citing a tweak on a website does not mean it works in all cases and for all tastes. I suggest you try out the various tweaks and decide yourself. I know Steve (at Decware) has tried the 98 cent tweak, and also a bullet shaped phase-guide and either preferred the sound of the flat (socket) shape or didn't think the bullet shape was appreciably better to warrant the extra cost. I may try out the bullet shape on my drivers by just adding a cone of plumbers putty on top of the "socket". I have a feeling it won't sound better. Why? I have owned various products from Decware and have come to trust Steve (or his ears at least). He doesn't do things solely because they make sense theory-wise, he just does what is simple and sounds good without costing an arm/leg - that's his "Zen" way of designing. I'm down with that.

 

[bbaker6212]

Here's the link to the Decware paper on the phase guide.

http://www.decware.com/paper46.htm

 

[sreten]

Citing a tweak on a website does not mean it works in all cases and for all tastes. I suggest you try out the various tweaks and decide yourself.

Couldn't agree more, I've no idea what any of these sound like.

Personally just don't like dodgy theory.

My only caveat is cutting out the centre of the
FE206E is not in any sense reversible or a try out.

sreten.

 

[bbaker6212]

Here's someone who did the "socket" tweak on a different fostex driver (FE167E) with positive results...

http://f18.parsimony.net/forum31999/messages/62801.htm

 

[MJK]

If you are interested in different types of phase plugs, there is a link on my site that contains some measuremnts of different phase plug shapes applied to a Lowther DX3 driver. You can see the impact different phase plugs have on the high frequencies and get some ideas for different shapes you might want to consider.

 

[planet10]

Let's try to keep this phase plug thing at a reasonable level, ok fellas?

Keep in mind those phase plugs are in a 2" tweeter and are the result of a mis-interpreted drawing Haven't tried them yet, but they may end up being a happy accident.

BTW Tim, Scott, the fellow who makes those phase plugs for me really wants to make it to your DIY fest... i visited him on the WE to listen to his FE167 ML-TLs.

dave