So I have this Cubo sub I built a while back to test out the design first hand and today I decided to literally slap an extension on it with some scrap plywood I had laying around.. because I have been reading about others using them on various designs on here... and holy smokes what a difference.. it made it noticably more directional and it produced a lot more output. Now I have the tools to do some measurements and plan to do some on this mod and make a proper extension for it, but my question is what math should I put into designing an optimal extension for it? Or does it even matter and anything is better than nothing? Any hints or suggestions of things to try are welcome, after what I heard today I'm definitely going to be using one of these where I can.
I'm sure he has. He's probably wondering where to start for inputs. My experience with barn doors is with front loaders, especially ones designed to run in stacks. I built my first two labs back in '02-ish. Output was pretty awesome compare to what else was available, but the undersized stack sounded 'bonky'. I added extensions continuing the 27 Hz cosh flare to a mouth 3x the total size. It was in 6 pieces, made out of OSB. The difference was incredible - enough to convince me to build the whole stack. I've also played with extensions on some 40 Hz KP15LF2-loaded horns that I was going to decommission. Now they're being refinished and repainted, and the flares will be built permanent (but optional). Again, the expansion continues at the same "rate" as in the horn, in this case tuned for 33 Hz. In all the cases I've looked at in Hornresp, continuing the flare at the same expansion rate (or something simpler but close) gives the best result.
I've recently (hell, maybe a year now) started "designing" new front loaders around the new B&C drivers. I can't seem to get a legitimate 30 Hz out of a stack of the 18's (but I can out of the 21's) without resorting to extensions. The extra length is needed. The other interesting thing is that the tuning changes - sometimes in good ways. With the extensions It'll hit x-mech at 26-ish Hz instead of 30. Without extensions hornresp predicts an excursion minimum right at 40 Hz - which means if the lows aren't needed, don't put them on, HPF at 38 Hz, and hit it with all the power you can muster.
Yeah, you can get equivalent SPL per volt out of smaller TH, but the input impedance is lower which really means it requires more power. A full size FLH stack can have an 8 ohm Zin per box (at the minimum!) with a 5.3 ohm driver. If you're looking to minimize power compression that's huge. Flare extensions will help you get to a "full stack" situation with fewer boxes, drivers, and amps. From simulations of TH with extensions, the impedance minimum doesn't really come up. Doesn't come up much with "8 parallel loudspeakers", either. But the output alone would be worth it for building a set for my TH18 stack.
I've recently (hell, maybe a year now) started "designing" new front loaders around the new B&C drivers. I can't seem to get a legitimate 30 Hz out of a stack of the 18's (but I can out of the 21's) without resorting to extensions. The extra length is needed. The other interesting thing is that the tuning changes - sometimes in good ways. With the extensions It'll hit x-mech at 26-ish Hz instead of 30. Without extensions hornresp predicts an excursion minimum right at 40 Hz - which means if the lows aren't needed, don't put them on, HPF at 38 Hz, and hit it with all the power you can muster.
Yeah, you can get equivalent SPL per volt out of smaller TH, but the input impedance is lower which really means it requires more power. A full size FLH stack can have an 8 ohm Zin per box (at the minimum!) with a 5.3 ohm driver. If you're looking to minimize power compression that's huge. Flare extensions will help you get to a "full stack" situation with fewer boxes, drivers, and amps. From simulations of TH with extensions, the impedance minimum doesn't really come up. Doesn't come up much with "8 parallel loudspeakers", either. But the output alone would be worth it for building a set for my TH18 stack.
Of course, if you have a target mouth area, but an extension limit, you might have to fudge the exit angle. A Cubo seems small compared to other horns; your "optimal" extension could end up being rather large. Were you trying to achieve a particular new cutoff or SPL level?
Have a look at the Richard long Bertha /Levan horn for mouth extensions. 42 inches by 8 feet mouth - I had 4 of them with 10 foot mouths in a club - double stacked 🙂
Yes, the Cubo is unnaturally small for a "horn" but it does produce more output than the same driver in a reflex box with hardly any size penalty so it is an intriguing concept.
Well that gets to the crux of the matter, I'd like to retain the portability of the box but gain as much additional SPL and extension as possible.These things already have a pretty wide bandwidth that is primarilly limited by driver excursion(surprise surprise), so the goal would be as much additional SPL while still being "portable".
My inquiry came as a result of a very simple experiment I did with some scrap plywood, I turned the box on it's side and formed a simple mouth extension with 2'x4' sections of plywood.. and that produced a very noticable increase in output. So I guess my inquiry is more about the optimal shape or flare rate of the extension and not so much the additional path length as I doubt I'd take it beyond 4 feet for portability reasons.
The Cubo 15 Extended looks like a...tapped scoop?? I imagine the throat area is the very 1st narrowed section after the driver cavity? If so, that would be the start of your flare profile. Some prefer an exponential profile with a hyperbolic finish at the mouth; some prefer a conical expansion if the horn length is long enough. I couldn't tell you what's best, maybe HornResp can help.
As I've heard from other sources (at the risk of oversimplification),
Bass extension = path length
SPL = mouth size
If you've determined a path length limit of an additional 4ft max, then all that's left is to decide upon how large you want the new mouth area to be, then connect the dots with a piece of plywood. Perhaps you could lay 2 Cubos on their sides, drivers closest together, and create a single collapsible extension for the pair of them?
I'm hoping that some horn guru will jump in & make it all clear....
As I've heard from other sources (at the risk of oversimplification),
Bass extension = path length
SPL = mouth size
If you've determined a path length limit of an additional 4ft max, then all that's left is to decide upon how large you want the new mouth area to be, then connect the dots with a piece of plywood. Perhaps you could lay 2 Cubos on their sides, drivers closest together, and create a single collapsible extension for the pair of them?
I'm hoping that some horn guru will jump in & make it all clear....
I have built three cubos 2 18in.and a half size cubo15 for an 8in. mcm driver. they have short horn characteristics probably similar to hd 15s, I have seen stacks of up to 24 singles but I think it would be used primarily for kick and not sub bass.
i know that extension works on tubas and titans, and probably will work as will corner loading. I believe someone referred to it as a bandpass hybrid. im not a pro.
i know that extension works on tubas and titans, and probably will work as will corner loading. I believe someone referred to it as a bandpass hybrid. im not a pro.
- Status
- Not open for further replies.