Also known as Cubo HT is designed for Home Theater and low bass songs (B&B Bass Boosted). It extends into the realm of infrasound, frequencies below 20 Hz that are felt rather than heard, nothing too much just enough to justify its name. Experience (truly) scary low sound effects in movies or voice modulating bass lines in songs. Lots of amplifier headroom is advised but only a few hundred Watts is needed to get you started. Full plans and marketing talk here: freespeakerplans
The current plan for Cubo Infra is the 3th prototype, the measurements are from the first, although little has changed. An Imperial version is in the making, plans available on request.
The design allows it to be placed with the driver aimed towards its audience (or any other direction), with rubber feet of 2 cm (4/5”) height it can be used in a down-firing position. This maximizes the effective front chamber volume, creating an acoustical low pass filter that makes it sound like it drops lower and it can also mask mechanical driver noises.
The measurements below show the response in a corner*, in down-firing position, with a 24 dB/ octave Linkwitz-Riley low pass at 60 Hz or 80 Hz without a high pass. Based on hearing alone the response drops off quickly below 17 Hz. Of course measurements inside a room are very sensitive to sub placement, listening position and the dimensions of the room.
* One thick stone wall, one thin stone wall and a wooden floor
Front view:
Side view:
Down-firing:
Construction plan:
Cut Sheet:
Measurements:
Magenta: Microphone in close proximity, 24 dB/ octave low pass filter at 80 Hz
Purple: Microphone in close proximity, 24 dB/ octave low pass filter at 60 Hz
Turquoise: Microphone at 1 meter, 24 dB/ octave low pass filter at 60 Hz
Best regards Johan (a.k.a. Cubo)
The current plan for Cubo Infra is the 3th prototype, the measurements are from the first, although little has changed. An Imperial version is in the making, plans available on request.
The design allows it to be placed with the driver aimed towards its audience (or any other direction), with rubber feet of 2 cm (4/5”) height it can be used in a down-firing position. This maximizes the effective front chamber volume, creating an acoustical low pass filter that makes it sound like it drops lower and it can also mask mechanical driver noises.
The measurements below show the response in a corner*, in down-firing position, with a 24 dB/ octave Linkwitz-Riley low pass at 60 Hz or 80 Hz without a high pass. Based on hearing alone the response drops off quickly below 17 Hz. Of course measurements inside a room are very sensitive to sub placement, listening position and the dimensions of the room.
* One thick stone wall, one thin stone wall and a wooden floor
Front view:
Side view:
Down-firing:
Construction plan:
Cut Sheet:
Measurements:
Magenta: Microphone in close proximity, 24 dB/ octave low pass filter at 80 Hz
Purple: Microphone in close proximity, 24 dB/ octave low pass filter at 60 Hz
Turquoise: Microphone at 1 meter, 24 dB/ octave low pass filter at 60 Hz
Best regards Johan (a.k.a. Cubo)
I love the design And how the vent then comes and surrounds the perimeter of the driver at the exit they share.
something very similar I have but doesn’t quite have that detail Or the approach to the exit which is truly unique. I love it , Mine is actually an isobaric group so Theres going to be a motor sticking out Of that but nevertheless thanks I hope it’s OK to steal your excellent idea😂👍🏻
something very similar I have but doesn’t quite have that detail Or the approach to the exit which is truly unique. I love it , Mine is actually an isobaric group so Theres going to be a motor sticking out Of that but nevertheless thanks I hope it’s OK to steal your excellent idea😂👍🏻
How does it compare to a vented box with the same Fb and physical box dimensions?
Your praise is well received 😉
Measurements have shown that the front chamber can also be simulated as a port, where the circular driver opening is sealed and the closed end of the chamber is actually open. So just a continuous port with the driver mounted inside of it, in that sense it is a reflex cabinet, although I would simulate it as a rear loaded horn in HR. On top of that it adds a measurable acoustical low pass filter which makes it sound like it drops lower, with the plus of masking mechanical driver noises. This can also be said for down-firing reflex cabinets with an additional front chamber in my experience, however it combines these two functions into one (get one, get one free).
There is also a notable, though subjective, difference between front-firing and down-firing. I think front-firing gives a faster sounding bass but prefer down-firing for my purposes. There are also differences in the frequency response, in the range of 1 – 2 dB, more output here and here, less output there, etc.
Measurements have shown that the front chamber can also be simulated as a port, where the circular driver opening is sealed and the closed end of the chamber is actually open. So just a continuous port with the driver mounted inside of it, in that sense it is a reflex cabinet, although I would simulate it as a rear loaded horn in HR. On top of that it adds a measurable acoustical low pass filter which makes it sound like it drops lower, with the plus of masking mechanical driver noises. This can also be said for down-firing reflex cabinets with an additional front chamber in my experience, however it combines these two functions into one (get one, get one free).
There is also a notable, though subjective, difference between front-firing and down-firing. I think front-firing gives a faster sounding bass but prefer down-firing for my purposes. There are also differences in the frequency response, in the range of 1 – 2 dB, more output here and here, less output there, etc.
I've redesigned the plans in Imperial measurements:
Imperial Construction Plan
Imperial Cut Sheet
- Dimensions with fractions are minimized
- The smallest fraction is 1/16th instead of 1/64th of an inch
- The cabinet volume is increased to compensate for sheet thickness (3/4" instead of 18 mm as is typical in Europe)
Imperial Construction Plan
Imperial Cut Sheet
Cubo,
Nice design!
Only missed we Imperialists prefer 22.5" cubes because they are a truck box integer, 4 x 22.5" =90" 😉
How much does the Fb change between front firing and down firing?
The room response makes it difficult to determine the actual LF response, have you tested it outdoors yet?
Art
Ah, finally a glimpse into the mind of an Imperialist. I've definitely had a few questions over the years if Cubo's can be slimmed down to 57.1 centimeters.
There isn't a significant change in Fb low, there is a measurable change in output and a perceived change in attack.
I've been asked that question for over 12 years now, when one pops up I'll post it on this forum 😉
There isn't a significant change in Fb low, there is a measurable change in output and a perceived change in attack.
I've been asked that question for over 12 years now, when one pops up I'll post it on this forum 😉
Old Imperialist- though USA straight truck boxes usually can be counted on to have at least 90" interior width, 96" has become common, and most semi-trailers are now 98"-100".
gee - some reason finally to get beyond the Barbara Stanwyck era in movies.
A little tilt and triangular aperture to the front chamber and - K-ish - (probably chuffyish too)
A little tilt and triangular aperture to the front chamber and - K-ish - (probably chuffyish too)
Now nick named the Karlson Infra, all the swag of a Cubo Infra, with all the benefits of a Karlson.
Just as low, just as Karlson.
Just as low, just as Karlson.
This is really cool! I have a hacked up ugly version with a square aperture that’s not even of Carlson worthiness… from leftover junk wood /osb during Covid lockdown boredom/wood acceess… These pictures are inspiring to give it another go now that lockdowns over. It sounds really good and deserves it. Why is basically a mass loaded (dalene step initially) transmission line with the abbreviated rear chamber/exit.Now nick named the Karlson Infra, all the swag of a Cubo Infra, with all the benefits of a Karlson.
Just as low, just as Karlson.
If you get lucky you can swap the location that port entry in the main chamber and fill in the void at the top, which might smooth it over if you look at the simulation.
WoW - I was half joking with regards to your CUBO - but a way to tune low in a K if one desired.
Booger weldz: I loosely based the baffle to front opening angle on the picture below. Having the port enter at the other end of the Karlson slot will likely have worse low end performance. The extra space due to the angling won't increase performance for the infra part, that's for sure. How would you go about it?
Freddi: So was I, wouldn't mind a collab to make this work though.
Freddi: So was I, wouldn't mind a collab to make this work though.
With a port of that length, the impulse response is going to be horrendous. For home cinema rumble and car audio-like one-note farts it might suit your needs, but you should never, ever consider a design like this for music if you have any interest whatsoever in fidelity...
The response is frequency and SPL dependent. Are you sure that SPL for SPL, it is that horrendous? It often is not. In that case, for good fast sound you just HPF it higher when needed.
IMO the original Karlson (aka "K15") is an excellent sounding cabinet when used with appropriate drivers. Its tuning is around 48Hz or so with the 260 sq.cm port shown in the 1954 plan above. The front shelf does some correction - shift for a dip. To remove the front shelf may deepen the dip unless the front cavity is made more shallow. (which would increase height from 33" to say 36" to maintain low excursion in the 10-120Hz area.
K15 makes a wonderful sounding subwoofer when used like John Tucker did with the "Exemplar" project and low fs Altec 15. This doesn't make much sense to me as it would seem the front chamber would be contributing very little with crossover at 80-100Hz. Perhaps its the linearity and low mass of 515 or 416 which makes it sound "adept" ? The Exemplar mod needs no modification to existing K15 whose port width is 3.5"-4.5" as is accomplished with two right-angle pvc elbow. Boost is applied like that for 6th order reflex at ~30Hz. A 15" Eminence/Dayton 295-070 in 6th order reflex measured close to my K15/Altec but sounded crude in comparison.
@CUBO - I'm too stupid to make out the width and approximate chamber volume of your Infrasub but did do a rough guess as a BP6. There's probably another way to enter it into hornresp so impulse can be calculated.
I don't have skills to figure out much and would like to do a little Karlson 2-way of merit - I've apnea - reflux - heart failure - diabetes - cancer - obesity and old age working against time plus stay with my son who can't tolerate the clutter of my audio toys.
K15 makes a wonderful sounding subwoofer when used like John Tucker did with the "Exemplar" project and low fs Altec 15. This doesn't make much sense to me as it would seem the front chamber would be contributing very little with crossover at 80-100Hz. Perhaps its the linearity and low mass of 515 or 416 which makes it sound "adept" ? The Exemplar mod needs no modification to existing K15 whose port width is 3.5"-4.5" as is accomplished with two right-angle pvc elbow. Boost is applied like that for 6th order reflex at ~30Hz. A 15" Eminence/Dayton 295-070 in 6th order reflex measured close to my K15/Altec but sounded crude in comparison.
@CUBO - I'm too stupid to make out the width and approximate chamber volume of your Infrasub but did do a rough guess as a BP6. There's probably another way to enter it into hornresp so impulse can be calculated.
I don't have skills to figure out much and would like to do a little Karlson 2-way of merit - I've apnea - reflux - heart failure - diabetes - cancer - obesity and old age working against time plus stay with my son who can't tolerate the clutter of my audio toys.
Attachments
I thought that’s why he said ‘infra’ From the start. . Put that at the very bottom. Then put ‘regular’ subwoofers above it and you’re setting up steps in the right direction which is everything hiFidelity requires and likeky ‘more’?? .. on the path up as 16 to 48, 32-96, 86.4-432…. Kinda how they end up as individual speakers if you were shooting for something like that while using the same architecture essentially in quarter wave shapes (folded) three times in each.. and they all used driver entry location and folding to break it all up in 12 parts of a circle as phase degrees 30 60 90 etc.. They’re all overlapping and using (0.3492)1/3 of the length of the prior to do so perfectly with respect to TS parameters as the needed cross-sectional area used you can’t really lose. everything falls into place wonderfully at that point using the idea of ‘TqwT or TL’. At odd harmonic intervals inside(fold and driver entry location specifically) and out(spacing in cabinets as low - high subwoofer freqs ).
Kind of an unusual scenario. But It doesn’t have to be?