What's the purpose of the recessed midrange some manufacturers do?
Small waveguide?
Only for looks?
Anyone tried it?
Small waveguide?
Only for looks?
Anyone tried it?
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Long story short...The primary reasons usually revolve around time and phase alignment, as well as improving the overall frequency response and directivity, also help with smoothing edge diffraction... IMHO
Most of the speakers I've seen have only the midrange or both midrange and the tweeter recessed.
To get the tweeter time and phase alignment isn't it a bad thing to only move the midrange further back?
It would be very interesting to see measurements, anyone who wants to share?
To get the tweeter time and phase alignment isn't it a bad thing to only move the midrange further back?
It would be very interesting to see measurements, anyone who wants to share?
Progressively muted with increasing frequency in comparison and in retrospect have to keep in mind I only used 1st order XOs with RLC frequency shaping networks (AKA CD horn EQ), zobels.
if anyone is interested i made my own measurement, made a baffle out of cardboard, 17mm thick.
Red is flat baffle and green is with the cardboard.
0
30
45
60
Red is flat baffle and green is with the cardboard.
0
30
45
60
That is the most important aspect of it. The cones and dome are ceramic, very hard and stiff but also very thin and very fragile, even a slight light push can shatter them. They are recessed further than the acoustic advantage of a small WG would require. While sounding very precise and having an excellent resolution, that's why I will never buy some of these. Several models went already out of production and you can't get a replacement anymore. There are several reports and photos especially of the bass drivers which shattered just by playing music.
I remember reading a diffraction study that showed all the possible 3D shapes, starting with a square, rounded corners, etc. the least diffraction was from a sphere with an inset driver. I’ve seen other studies where tear drop prisms with depressed drivers had great dispersion. I don’t know who did the studies but they float around the forums. Probably over in full range?
Well looks like the cardboard smooths the response or damps the response. Interesting result, but cardboard may not be the best material for this experiment.
The Advent A-4 had a recessed woofer. The frame itself was dished in. Some had felt or fiberglass around the woofer and tweeter to help with diffraction.
Nice to see a picture of classic Advents.
The foam surrounds appear intact > how is that possible ???
The foam surrounds appear intact > how is that possible ???
I have tried it several years ago and didn't find any particular reason to use it other than estetics.
Diffraction plagues my designs too, but basically only for the tweeter, but with a very shallow waveguide of just 4 mm thickness and the outer diameter of the mounting plate of 100-110 mm the diffraction basically disappeared.
Edges of cabinet rounded with a radius of 22 mm. Baffle width 250 mm.
That shallow wave guide helped a lot to get all parts of the dome, even the tip below the surface of the baffle.
An annoying -2,5 dB dip in 2-4 kHz region vanished completely.
A bit similar to Rockports tweeter recession but a mm or two less deep, and a cm or so less in diameter.
Very effective at preventing diffraction.
Diffraction plagues my designs too, but basically only for the tweeter, but with a very shallow waveguide of just 4 mm thickness and the outer diameter of the mounting plate of 100-110 mm the diffraction basically disappeared.
Edges of cabinet rounded with a radius of 22 mm. Baffle width 250 mm.
That shallow wave guide helped a lot to get all parts of the dome, even the tip below the surface of the baffle.
An annoying -2,5 dB dip in 2-4 kHz region vanished completely.
A bit similar to Rockports tweeter recession but a mm or two less deep, and a cm or so less in diameter.
Very effective at preventing diffraction.
As mentioned above, there can be reasons such as time-alignment and diffraction. More often useful for the tweeter, especially if combined with a waveguide.
But a it is especially common with rear-mounted drivers, which inevitably have some thickness of baffle in front of them. Chamfering or rounding the corners of the baffle's hole reduces the diffraction that they would cause. Mostly effective on the higher frequencies, and can again include waveguide shapes. But there is a lot of variation; rear mounting is often just a kind of aesthetic thing, to hide screws and ugly driver frames, not always thought through from an acoustic angle.
In some cases a similar effect can be caused even on a flush mounted driver. If a grill-frame is then added to the front of the baffle, not dissimilar to Shure's cardboard tests above.
But a it is especially common with rear-mounted drivers, which inevitably have some thickness of baffle in front of them. Chamfering or rounding the corners of the baffle's hole reduces the diffraction that they would cause. Mostly effective on the higher frequencies, and can again include waveguide shapes. But there is a lot of variation; rear mounting is often just a kind of aesthetic thing, to hide screws and ugly driver frames, not always thought through from an acoustic angle.
In some cases a similar effect can be caused even on a flush mounted driver. If a grill-frame is then added to the front of the baffle, not dissimilar to Shure's cardboard tests above.
My buddy pulled his set out of the garage and we decided to try them out with some classic rock. We blew out the foam surrounds with the first note of Back in Black. 🤣🤣🤣 These however, must have been re-foamed.