I don't have the chart's math anymore to calculate the efficiency, though the net Vb (dm^3 = liters) has near enough octave spacing to suit me, so @ ~20 Hz Fb @ 0.5 % eff. (89 dB*) it must be at least 160 L ((4 ft x 8 ft)^0.5 = 5.657 ft^3) (160 x 0.03531467 = 5.650347 actual conversion)
* efficiency/dB conversion
* efficiency/dB conversion
The graph is from "Vented-Box Loudspeaker Systems Part 1: Small-Signal Analysis"
by Richard H. Small (the Small in Thiele/Small T.S. parameters)
https://sdlabo.jp/archives/Vented_Box_Loudspeaker Systems_Part_1-4.pdf
The paper explains the graph..
Because of driver mechanical losses, enclosure losses, and the use of alignments other than that which gives maximum efficiency for a given value of QL ( enclosure Q at Fb resulting from leakage losses) are typically 40-50% (2-3 dB) lower than the theoretical maximums.
Hey guys its been awhile. After careful research and judgement of what my drivers are capable, I decided to go with the cubo 15 and my oh my....I heard they make some serious spl but its a whole different thing experiencing, so far I've broken 2 pictures and a few plates with the amount of bass these things produce. (I think I'm also the first one in my country with cubo 15s also hehe). Thank you guys for your suggestions and help I really appreciate it. Build pics coming up
Still thinking if I'm gonna paint them or wrap them but there they are for now hehe, I'm pretty satisfied honestly. These actually lived up to the hype.
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They look great, and super simple… is that 15mm ply? Whats the weight of the cabs without drivers? My thing is portable party speakers, and I’m considering where to go next. Was thinking of making a small cardioid setup with 3 Tham 15 (I have a Tham 12 already and it’s a pocket rocket!) so we can party on the beach without annoying the neighbours! But the Cubo looks like it could be even lighter. Why did you decide on the Cubo over Tham?
@weltersys I always appreciative your objective narratives / comparison of box types… the cubo looks to me closer to an extreme BR than a tapped horn like the Tham, how would you compare / contrast those designs? I’m thinking of putting a high power sub like B&C 15ds100 inside with approx 1kw 🤔(and at risk of igniting passions… building with well braced 12mm ply 😱)
There are too many variants of the cubo for me to make any generalized objective comparisons.
Tonskulus wrote:
"Just punished my tham15 @ 1kW of power, oh my.. it slams hard! And it has much better cone load compared to cubo. P540 was not happy in cubo (over excursion and flapping etc) but no problems in tham."
https://forum.speakerplans.com/cubo15-vs-tham15-measured_topic104372.html
@k3rry yeah its 15mm ply, weight without drivers is about 35 pounds, with drivers its closer to 50 pounds. i decided to use cubo over tham because i wasnt really confident that my drivers would perform well in the tham, as they are more bass reflex based drivers. So I did some more research and found the cubo which is somewhat like a hybrid between the two. Plus I heard pretty good things about them. But oh my...after I built them. 1 cubo made my previous bass reflex boxes sound like toys. They really put out some really good spl and goes low enough...atleast for me. By ear they seem to be between 4db - 6db down at 40hz. With my drivers they play flat from 45 to around 95hz, after 95hz they start to sound a bit honky, which is fine seeing I normally set my highpass at 90hz.
@weltersys Well my observation with the version i built which is the standard version, there is not bottoming out whatsoever with the settings I use, 24db octave rolloff at 38hz, highpass at 90hz. Both subs running of a bridged qsc rmx 1450 at 4ohms, trust me they pound hard, they even decent with rap music😂
RickTM,
Being almost double the enclosed volume and a much higher tuning than your previous bass reflex boxes, no doubt the cubo would be way louder.
Fb (box tuning frequency) is the low frequency point where the cone moves the least, either side the excursion increases, below Fb the output drops off rapidly.
Easy to see the excursion using a sine wave generator.
What is the Fb of your cubo cabinets?
Art
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@weltersys I don't have any measuring equipment but judging from using sine waves, looking at the excursion and seeing when the output starts to drop off, the fb seems to be around 40hz - 42hz, almost no movement at those frequencies
If you had the 38Hz 24dB high pass filter engaged, you won't see much cone movement at 40-42Hz or below.
I'd expect the Fb to be closer to 50Hz.
At any rate, if you take out the high pass filter, you should be able to see the cone excursion go from fairly high about 1/3 octave above Fb, say 60Hz (50Hz if the Fb actually is 40Hz), drop to minimum, then go back up higher below Fb.
@weltersys I tested it without the highpass, I did a frequency sweep from 200hz to 30hz, cone movement was fairly high at around 50hz -55hz then cone movement reduced at 40hz to 42hz, then cone movement starting getting high fast below 40hz, almost free airing (if free airing is even a term lol) at 30hz
That's why they are BASS BINS and not SUBwoofers. Folks kill me calling a 50hz bass bin a SUBwoofer. If the enclosure cannot play A0 or needs a high pass filter above 27.5hz, then it's not a SUBwoofer.
@BP1Fanatic , Yeah I get what youre saying, they're not true subwoofers but I dont need subsonic bass for my application so its ok. I just need down to 40hz (for now) so i'm alr.