Fender's Tone Ring speaker cabinet vs. standard bass reflex

[Rhodesplyr]

A friend of mine is building his own copy of a Fender Tone Ring speaker cabinet, something I didn't know much about, so I started investigating.

It seems to me that the Tone Ring design is just a bass reflex cabinet, the unusual part being the configuration of the port such that the driver and the port share the same cabinet opening.

Or is there more to it? I ask because it seems like it's a lot of trouble to build a cabinet this way compared to a standard bass reflex cabinet. I've never encountered one in real life. I've seen this same question posted on other forums, but no one seemed to know if there were specific advantages to the tone ring design.

[Old Tele man]

Tone Ring = lots of Mojo but little musical improvement.

[Malcolm Irving]

....
It seems to me that the Tone Ring design is just a bass reflex cabinet, the unusual part being the configuration of the port such that the driver and the port share the same cabinet opening.
...

Yes, that seems to be it really. I suppose the reflex port surrounding the speaker ought to have some effect on directionality, but only for low frequencies (which are not very directional anyway). High treble frequencies, where we would probably like to reduced the beaming effect, won't make it round to the port very well.

At some low and mid frequencies SPL will be increased by the reflexing, while at others it will be reduced.

[J M Fahey]

A friend of mine is building his own copy of a Fender Tone Ring speaker cabinet, something I didn't know much about, so I started investigating.

It seems to me that the Tone Ring design is just a bass reflex cabinet, the unusual part being the configuration of the port such that the driver and the port share the same cabinet opening.

Or is there more to it? I ask because it seems like it's a lot of trouble to build a cabinet this way compared to a standard bass reflex cabinet. I've never encountered one in real life. I've seen this same question posted on other forums, but no one seemed to know if there were specific advantages to the tone ring design.

Oh yes you have.



I mean ... you have seen one or more Ampeg Portaflex B15N, havenīt you?





Showing internal vented/slotted baffle, still missing the outer ionbe with the larger-than-speaker hole which would be what Fender call "Tone Ring".

Of course, you need the whole 2 baffle assembly to work, the front one provides the exit slot around speaker edge, but does not hold it (since there is no physical contact between them), the inner one both holds the speaker (in Fender with a custom made part, in Ampeg with a plywood ring) and vents around it, slots in Ampeg, slots or round holes in Fender.

In any case, they are invisible from the outside even if you remove grill cloth.

Tone Ring = lots of Mojo but little musical improvement.

Oh, in THIS particular case they are functional: they provide an "invisible" but doubtlessly working bass vent with a long tuning tube yet nobodyīs the wiser.

Personally for long years I had believed Portaflex cabinets too be plain closed back ones, period, since I could find no tuning port whatsoever, only in recent years I found they were actually deep tuned Bass Reflex cabinets.
Hats off to Mr Oliver who invented the concept.

Fender version:



Adapter:



Assembled :



The real (Fender) thing:

[loudthud]

Keep in mind that these designs were, for the most part, done before Thiele and Small published their paper on how to do the math for a maximally flat 6th order high pass alignment. So alignment was done by the WAG system. Wild Ass Guess. They didn't even have very good measurement tools. At one point they would measure bare speakers in a vacuum to remove the influence of air on the cone. Actually, that part was pretty smart.

[J M Fahey]

Yes.
There were 2 ways (besides wild guessing that is)

* One was the grand dad of TS and quite accurate:
a) measure free air speaker resonance
b) same in a small but controlled size closed cabinet, think 2 cu Ft cube (I still have my original one since the early 70's and use it as shop speaker, go figure) and notice how much resonant frequency rises.
c) check a graph which with those 2 values suggests a cabinet volume
d) another graph gives you port diameter/length pairs vs. *cabinet* resonant frequency and and cabinet volume.
A somewhat crude approach and gives you *one* alignment out of possible 6 or 8, but is not bad at all for Hi Fi.

* Plan B and what most MI cabinet designers did: use just the simpler graph (which was published in countless "Build your Reflex Cabinet" book chapters and magazine articles) , make a large box (think Sunn/Ampeg and similar cabinets) and tune it to 40/45Hz.
It basically works.
In general boomy underdamped Bass but thatīs not wrong at all in a live Band situation, where a deep bass peak is a bonus.
Low damping Tube amps would increase the Bass peak ... again an asset.

* Plan C and I have seen it endorsed in books, go figure: make whatever prototype cabinet you can, cut a rectangular slot in the bottom, partly cover it with a piece of plywood held by a couple C clamps and try different port sizes until you find one you like best.
Once you found it, make production cabinets with those measurements.

[Zozobra]

Unless he really has his heart set on that particular cab I'd point him to some of the flatpacks here:
https://www.speakerhardware.com/diy-...-cabinet-kits/

The designs are very well regarded.