Home High Efficiency Speaker Asylum

Need speakers that can rock with just one watt? You found da place.

[ Follow Ups ] Thread: [ Display  All  Email ] [ High Efficiency Speaker Asylum ]
[ Alert Moderator ]

Re: Horn stuff and a post back for Tom

Hi Tom!

You wrote:

> > What your saying is correct then that the speaker, especially a
> > point source direct radiator "moves around in time", it in effect
> > moves front to back depending on frequency.

And, it is non-linear around system resonance too.

> > Use a laser velocimeter to monitor the cone's motion (because
> > light has no delay here to speak of) and apply a signal, complex
> > in frequency to the driver. What one finds is at first, nothing
> > happens, there is no motion. One finds the speaker has a delay
> > equal to some distance in time and from that delay, the acoustic
> > phase cannot deviate more than the + -90 degrees as dictated by
> > the equivalent circuit.

Quite a broad range of distances over the course of a few octaves.

> > A highly loaded horn is resistance dominated and so one finds that
> > by the time one has a 50% efficient horn, that the acoustic phase
> > is around zero degrees mid band. Over the region the acoustic
> > phase is zero degrees, the driver does not move in time with a
> > change in frequency.

But the horn in the Unity is nowhere near as efficient as this, wouldn't you agree? The midrange drivers aren't even loaded at the apex; The horn is, as you say, a "lossy" horn or what I have called a "mal-formed" horn. It does not meet the conditions of the Webster equation.

> > Flat amplitude AND zero degrees phase are the conditions needed to
> > preserve the waveshape of the input signal, no wonder so many like
> > horns.

This is true, and it is simultaneously impossible for any filter to accomplish.

> > See the response and phase of the BT-7's for example (4 are around
> > 45% efficient)

I thought the BT-7 was a bass horn that was not a Unity device, true?

> > In the Unity, I can't do anything about the phase response of the
> > woofer, one is stuck with that and in that case the closest one
> > can come is to match the time /phase at and around crossover.

I see, yes. You make no attempt to time align the woofer subsystem, finding it impossible. That brings you and I much closer to agreement. Around crossover, the distances are smaller. Actually, the distances we're talking about in the woofer/midrange transition point are what would be easiest to work with. They aren't so large as to require a huge cabinet and they aren't so small that you can't physically fit components in the space needed. The 300Hz to 600Hz range isn't terribly difficult to "play with."

> > One last thing, the conical horn above some frequency (set by the
> > wall angle and mouth size) has a constant directivity.

Yes, I know. That's what CD horns usually are - conical horns.

> > The acoustic power of ALL compression drivers rolls off above a
> > few KHz, Plane wave tube measurements show this and so does the
> > response when on a CD horn.

I didn't say that I felt your design reduced efficiency of a particular driver in the 200Hz to 20Khz range. I said that it didn't provide impedance matching over this whole range. It does so only over a fairly limited band - roughly the vocal range, I suspect.

> > Understand, the conical horn has nothing to do with the roll off,
> > it simply does not concentrate the sound into a smaller angle like
> > curved wall horns do.

Many manufacturers install secondary devices such as diffraction slits to reduce beaming. As an example, the throat of the JBL 2370 has a secondary function, acting as a diffraction slit at higher frequencies.

> > The roll off on the low frequency side IS due to the rapid
> > expansion rate of the horn at the apex where the driver is
> > coupled to the acoustic system. It is the expansion rate which
> > governs the "high pass" part of the horn.

Conical horns become peaky at their low end, this is true. They act like a series of resonators combined with a high pass filter.

Wayne

This post is made possible by the generous support of people like you and our sponsors:
  Sonic Craft  

Follow Ups Full Thread
Follow Ups
You can not post to an archived thread.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]