In the last few days, my internet pages have been inundated with adverts for "Bandpas Speaker Boxes". These are new to me and I had to look up what they are. Apparently they are bass speakers with a very narrow frequency response.
Are these really a new fad or are they just a new gimmick that the industry is pushing on the uneducated listeners?
I know that there are all different ways people prefer to hear their music. My preference is to hear music as close to the original recording a reasonably possible. I can only assume that these devices would appeal to people who listen to rap and modern "boom-boom" music where they can exaggerate a booming narrow band of bass frequencies.
Does anyone have more information or opinion on the subject?

 

You nailed it .........
Except for the fact that this design has been around for many decades.

It's not particularly "efficient" but it tends to not sound quite
so "flabby" and "loose" like the usual Vented-Box designs.

It's a one-Octave "Resonator", and is a completely useless design as far as I'm concerned.

A Sealed Cabinet, even though its not very efficient,
will provide the best fidelity, including excellent "Transient-Response" which
no supposedly "tuned" Cabinet can achieve.

A "Horn-Loaded" Cabinet creates a closer "Impedance-Match" between
the surrounding Air and the Driver-Cone and has close to perfect "Transient-Response"

Transient-Response is equally, if not more important than, Frequency-Response.

The whole game depends upon whether You are willing to sacrifice
a hard-edged, clean, "hit" from a Kick-Drum,
for an additional increase in supposed "Low-Frequency-Content",
( which doesn't necessarily resemble the original Recording ).

If You have a Full-Sized SUV/Truck/Van
there are compact Horn-Loaded designs that work really well,
but you'll have to build it yourself from online-plans available for a small Fee.
https://billfitzmaurice.info/AutoTruckTuba.html
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This is the first I have heard of them. It is probably something like having a really great cross-over network. It would avoid doppler shift caused by bass and lower mid-frequencies and whatever else cross-over networks are suppose to do. I anticipate more information from Canada.

 

Maybe Dick says I am the person in Canada? There are few more audio guys here.
A one-octave bandpass will resonate and continue ringing when it should stop playing. Then it is a "boom box".
Many cheap speaker systems resonate like mad producing "one note booming bass".

I have 8" woofers in large sealed boxes and have 6.5" woofers in smaller ported boxes. Both sound the same.

I simulated a bandpass filter with a second-order highpass and a second-order lowpass Butterworth filters.
The -3dB bandwidth is much more than an octave but there is no flat level section because the high-cutoff and low cutoff are too close together. It would make boomy 45Hz noises.
Because the high-cutoff and low cutoff frequencies are so close together they combine to reduce the peake level to less than half!
Here is the simulation:

 

LowQCab nailed it. Although I think the transient response of bandpass cabinets is usually even worse than vented boxes (4/5/6th order), since there are more energy storage elements (mass of air in the port(s), springy air in the chamber(s)). The big benefit is that they can be tuned for a loud kick drum to make people dance (or impress potential customers). But they have to be designed to work with a particular woofer's electro-mechanical characteristics (described by the Thiele-Small parameters). If you throw a random woofer in a random "bandpass" box, you're liable to end up with something like the sub in my friend's truck. It sounds flabby/boomy on almost all music, except one particular track that hits just the right bass note. Contrast that with a properly designed sealed box subwoofer, which will sound good with all music and also do justice to movie soundtracks.

I'm skeptical about the effectiveness of low frequency horns in-car. I don't think they work any better than a sealed box, since "cabin gain" already guarantees a bass boost. Maybe in a very large vehicle like a bus or van. I believe cabin gain is also problematic for ported and bandpass cabinets, particularly if you're designing an SPL system with a tiny "cabin".