cubo 12

@Martin: That's a pretty decent try. The main problem I see is that you've got an F3 of 63 Hz. The benefit of AkAbak is that it allows you to be more accurate than Hornresp can be. If you take that advantage and take care of every little detail you can think of, you can drop the F3 considerably lower. Output wise you're pretty spot on. After that you could look how to best approximate that in Hornresp again.

@Wannabass: With an 24 dB/octave high pass set at 40 - 45 Hz, you're way more likely to overheat the driver than to see it run out of excursion any day soon. Personally I prefer to give a driver about 1.5 times the AES-power rating. Before most brands jumped to the AES power rating, average power handling values were 1.25 - 1.4 times lower as today. Meaning that the 2 times rms-rating of the past correlates to ~1.5 times AES today.

I'll try to advise in that way that it will keep your Cubo 12 safe and solid. In most situations Cubo 12 (loaded with the 12SB30) will survive on a 25 Hz high pass and still take the power from your current amplifier. Till that one day that you supply plenty of power and the turn tables put in a massive 25 Hz feed back loop. That's why I won't advise it, even though sometimes I'll use a 25 Hz high pass myself

Nice build, really like that double thickness look around the horn mouth.

Best regards

Cubo

Cubo15 wrote: @Wannabass: With an 24 dB/octave high pass set at 40 - 45 Hz, you're way more likely to overheat the driver than to see it run out of excursion any day soon. Personally I prefer to give a driver about 1.5 times the AES-power rating. Before most brands jumped to the AES power rating, average power handling values were 1.25 - 1.4 times lower as today. Meaning that the 2 times rms-rating of the past correlates to ~1.5 times AES today.

I'll try to advise in that way that it will keep your Cubo 12 safe and solid. In most situations Cubo 12 (loaded with the 12SB30) will survive on a 25 Hz high pass and still take the power from your current amplifier. Till that one day that you supply plenty of power and the turn tables put in a massive 25 Hz feed back loop. That's why I won't advise it, even though sometimes I'll use a 25 Hz high pass myself

Nice build, really like that double thickness look around the horn mouth.

Best regards

Cubo

:oops: thanks you smiley1 (isn't that "double thickness" what's on your plan? smiley22 )

...I can't find AES ratings for my amp, only RMS, but your power and filter explanation left me confused :crazy: :

I assume that PD12SB30 rated 400w rms will be ok with my 500w rms rated amp ... even without ANY high pass filter, as long as I don't feedback loop it hard? (I don't have a filter now, total newbie style!)



here is another pic of my Cubo12, with a top :

A driver has an electrical and mechanical power limit. The electrical a.k.a thermal power limit, tells how much power it can handle before burning up. The mechanical power handling is denoted by the Xmax, Xmech and the driver/ cabinet combo.

If you feed the 12SB30 in Cubo 12 (or about any other design) a 10 Hz sinewave at ~400 W, without high pass, it will mechanically destroy itself, even though the electrical power limit wasn't breached.
If you feed it a 500 W, 1 kHz sinewave, it will likely burn up even tho mechanically it wasn't anywere near Xmax.

Sometimes songs contain massive low frequency doses, either intentionally or un-intentionally. Those low frequencies will eat up excursion and consume a lot of power. However, as you can not hear those low frequencies, overall output will be lower then could be and output levels are likely cranked up on the mixer.. It's entirely possible to destroy a 400 W AES, driver with less then 400 W AES.

In short, PA-use without any high pass filter is asking for trouble. Using a 25 Hz high pass is not-asking-for-trouble. Using a 40 Hz high pass is avoiding (most) trouble.

Best regards

Cubo

ok, thanks a lot for this newbie friendly explainations smiley20 !

Mr Cubo, do u think that if i will make Cubo12 as narrow as i can ( a lit bit narrow than MTH30 - 1 cm less) will it sound as good as now ?
Can u tell me how much i must increase the height or depth so that it should sound as good as now.
Thanx a lot !!

Practically a 33 cm wide cabinet made from 15 mm material, often means the 12" driver won't fit unless extra space is created "into the walls" (i.e. with a router).

Other then that, I will look into it more closely, perhaps I will be able to make it mutually beneficial.

Best regards

Cubo

Hi Guys, I don't know if anyone has tried to build these using 18mm thick ply. So I have changed the sizes of some of the panels on thedrawing can you have a look MR Cubo and see if they are correct.

It's been ages since i loadded a pic but here goes.

Hi Jim,

If I understand correctly, you want to build Cubo 12 with a minimum change to both the horn and chamber volume, utilising 18 mm material?

In that case the overall height should increase 3 mm for every panel it meets from bottom to top (5 panels) = 46.5 cm.
The overall depth (3 panels) = 48.9 cm. The overall width (2 panels, ignoring the bracing) = 45.6 cm

Top panel/ground panel; 48.9 x 42 cm (I usually make these panels a few mm longer and router them to size after the build)
Side panel left/right; 48.9 x 45.6 cm (I usually make these panels a few mm longer and router them to size after the build)
Rear panel; 42 x 42 cm
Front panel; 18.4 x 42 cm
Baffle; 32.45 x 42 cm
First horn panel; 30.7 x 42 cm
Second (angled) horn panel; 13.95 cm (same)
All Bracing: + 3 mm or the same

Tell me, if i have made a mistake.

@Kentech: Could you send an e-mail to questionsaboutcuboatgmaildotcom ?
Perhaps I’ve an interesting design-mod for you.

Best regards

Cubo

i've send an email there. Waiting for your reply with that draw... thanx

hi everybody,
I noticed that in some of the bigger cubo's (but not the 12), the designer offers a choice of mounting the driver with magnet inside the mouth or in the chamber.

Do you think "magnet in mouth driver mounting" in my Cubo 12 is worth trying? would make it play lower ? (I haven't check the dimensions yet to see if the driver would fit smiley36 )