Chuffed, twin flare BR part 2

Jump to Latest
Randy Bassinga

Randy Bassinga

Member
Joined 2021
#1
The bandsaw special, redraw
This will evolve a bit more as I get it ready for cutting. Here is what it looks like based in 16mm sheet material. The lines show panel buildup in some areas. At the port exit, the lines show 6x 48mm slices made up of 3x 16mm panel each plus a single 18mm slice in the centre. Braces are shown without cutout and this carving will happen with the driver cutout depth constrain

Pipe Sd had increased slightly to 50cm2 and depth is still 306mm. Mouth flare has increased to 500cm2

Vb 30L (+5.2L reserve ballast for driver chassis and space taken up by electronics and fill, total internal excluding port is 35.2L)
External width 340mm, depth 400mm, height 460

Port non flared section Sd 60 cm2, slot width 306mm, total port length including twin flares 439mm
Driver, any pro mobile subwoofer that fits a face. Currently configured for the DS18 ZXI12.4D running 1.2kwrms/2.8kw dynamic and tuned to 31.4Hz

Suggestions for a more well known driver 8 to 12" and capable of F3 33Hz and average 115dB potential that can work in 30L? Maybe
https://www.wagneronline.com.au/attachments/Audio-Speakers-PA/sbacoustics/SB34SWPL76-3-DV.pdf

The intention is to optimise a true BR rather than diverge into a line. This is the main problem with low Vas pro mobile subs. The ports end up like poor TLs due to aspect ratio. The original thread did result in a good-looking TL and TH when I optimised the long port

The graphs below are at 78.4v and 281g of polyfill in the Vb

Will she huff, puff or chuff?

1722294193349.png 1722270207971.png

1722295817698.png1722295698574.png
1722295997971.png 1722296158725.png

1722296232858.png 1722296303495.png
 
Last edited:
#2
The height of the port is very narrow, so - depending on what level you're using the sub - there will be quite audible port noises. I'd suggest you'd switch to a passive radiator which allows for lower tuning and (unlike a extended port) does not rob your subs volume.
 
  • Like
Reactions: freddi
#3
I don't have the design experience to properly translate this very spiky looking thing. I suppose this first design effort in real life will help build some context of what this spike would sound like

There is detail on dampening in the intro, 290g of poly. Below is the big spike in the graph. I read somewhere that under 25 is good? The red trace is undamped and black dampened. This is at 78.4v producing average 115dB

1722130397395.png
 
#5
Time to get serious with the flares and such on cabs like this which are too large for my CNC. I just did a click and collect on a cheap Ozito bandsaw with good reviews. In the pictured cab, the plan is to have the port area removable. The bandsaw will be used to quickly and quietly slice up a former using MDF or structural foam layers and stack it up into a former. This may visually appear like translam, but the engineering is a composite sandwich, so none of the issues of translam. A printed part can work but is inefficient in time and expense

I am now able to fashion a more fitting scoopy appearance for what will be primarily a Dub reggae renderer with a basslines based on thumb played attack with the strings........Sly and Robbie playlist plus our efforts via the studio gear
 
#8
you’re using radically fake Ts parameters which make the already exaggerated horn response graphs and info even more ‘fake’ and misleading. its all ‘lies’, theres nothing to interpret or learn from imho

i think my pea brain is thrown off most by the tight suspensions affect on the enclosure size choices (fake ideas to solve issues that don’t actually exist?) but the crazy (fake) motorforce score is fighting a 700 gram moving mass….🤷‍♂️ suggesting you need super long skinny ports /TL shapes
 
Last edited:
#11
Guys, let's forget about a specific driver. If what I see in from sims and modelling cabs is correct. Then the port tuning is a box to port function and doesn't use driver T/S. It's basically up to the driver to fill those two holes

If the driver is around 30Hz Fs then all should be fine other than the chuffing and pipe resonance issues which this shorter and narrow-minded port places over 540Hz. Am I getting this part right?

The very bandsaw friendly redraw port pipe Sd is 60 with even larger exit flare of 500 (500 Sd air piston driver?). Zero fill shows port speed below 25
 
#14
I think the programs are showing either incorrect BL due to either drivers not being broken in for measurements or someone at DS18 not configuring Qes correctly for the datasheet with all the DVC drivers. The DATsv3 will be here by Wed. Let's get a box ready to break the driver in and initial testing. Sealed is out of consideration
 
#18
Randy Bassinga said:
Then the port tuning is a box to port function and doesn't use driver T/S. It's basically up to the driver to fill those two holes

If the driver is around 30Hz Fs then all should be fine other than the chuffing and pipe resonance issues which this shorter and narrow-minded port places over 540Hz. Am I getting this part right?

The very bandsaw friendly redraw port pipe Sd is 60 with even larger exit flare of 500 (500 Sd air piston driver?). Zero fill shows port speed below 25
Click to expand...
Correct, you don't need any driver data in HR to design/tune a BR, though need the driver's specs to determine the area of the port.

Too short of time lately to continue following your threads and frankly from just reading this post have no idea what all you're referring to. :scratch1:
 
#19
GM said:
reading this post have no idea what all you're referring to
Click to expand...
All cool man. Trying to come up with a half decent cab to get a feel of these drivers as I break them in the car. The BR is a familiar system and preferred for initial auditioning

DATSv3 should be here tomorrow or day after

I think I am very close to nailing a 30L @30Hz box. It will be really really good to have it working well by 7th Aug
 
You must log in or register to reply here.
Top Bottom