Autotuba measurements, plus shiva

[simon5]

Wow, some people not believing me here. You can be skeptical if you want to, but this is actual SPL measurements. The room is small so keep that in mind. I can give you room size if you need it, I can ask the owner.

The design is a EBS ported subwoofer following exactly Adire Audio design. It's 142.5 liters or 5.032 cu.ft internal net. It's tuned to 18.34 Hz with a 18 inches long (17 inches effective) 4 inches diameter pipe, flared on both ends.

It was done with a Shiva Mark IV.
It's powered by a Rythmik Audio A250 250W amplifier into 4 ohms.
This amplifier have a rumble filter set at 12 Hz, second order, Q=0.707.

If you look in WinISD, you'll see that the subwoofer achieve 103 dB anechoic at 16 Hz, so I hope you'll agree with me that 4 dB of room gain at 16 Hz is not exagerated at all.

This subwoofer was designed to beat easily the SVS PB10-ISD sold at 470$ USD shipping included. We wanted to beat it with something which would cost less money to build. I can say mission accomplished.

Pictures are following shortly.

Here's all the parameters :

[Driver]
Brand=Adire Audio
Model=Shiva MKIV
Manufacturer=Adire Audio
ProvidedBy=Simon Arsenault
Comment=
DateAdded=20041124
DateModified=20041124
Qts=0,35041267334714
Znom=4
Fs=20,7642474688133
Pe=650
SPL=87,7486071535912
Re=2,9
Le=0,00212
fLe=0
KLe=0
BL=11,3
Xmax=0,0166
Cms=0,00047
Qms=6,5
Qes=0,370379710990481
Rms=2,50895412712862
Mms=0,125
Sd=0,0481
Vas=0,154252658878499
Dia=0
Vd=0,00079846
no=0,00362589642446061
Dd=0,247472871446066
EBP=56,0620542990458
numVC=2
Hc=0
Hg=0
SPLmax=112,87774072002
SPLmaxLF=98,6094748881186
USPL=92,1603558850874
alfaVC=0
Rt=0
Ct=0
gamma=90,4
Rme=44,0310344827586
Mpow=6,63558848051615
Mcost=0
Gloss=0,0347072703313253
VCCon=1
c=343,684120962152
roo=1,20095217714682
Thick=0,01905
Depth=0,130175
MagDepth=0,0381
Magnet=0,136525
Basket=0,2794
Outer=0,3112
Vcd=0,0508
DVol=0,00239926669428466
ParState=CCECEENNEENEECCCEECCNCCENNCCCNNNCCCCNCEEE EEEECNCC

[simon5]

Some pics...

Here's a 4' x 8' sheet of 3/4" plywood, as you can see, you must do some planning to prevent using a second sheet. The design fits very tightly on a sheet. Left is used wood, right is wasted wood.



Here's the box from several angles when finished (or almost) and ready to be painted.







Here's the box with a 2nd layer of stain. (It took 4 layers to achieve the darkness the owner wanted)

[simon5]

Some more pictures... (smaller ones heh!)

Here's the finished product, compared with the mighty Klipsch Promedia 5.1 Ultra subwoofer, which looks like a bug compared to this DIY subwoofer.







And finally here's the simulated Anechoic SPL curve without room gain. This curve shows a small rolloff to account for room gain which is around 3-4 dB per octave the lower you go according to Adire Audio. This means ideally the subwoofer would exhibit around 112 dB from 18 Hz to 100 Hz or 118 dB in the same range corner loaded.

[rcw]

Those are certainly impressive numbers Simon, I just wonder how much of the signal coming out is that which goes in. In its literature on the shival Adire is noticeably coiy about the matter of distortion, a driver with no flux modulation control or d.c. offset compensation making those kind of excursions with that type of input power must have consideralble distortion, and that 20Hz. output may be mostly 60Hz.

[simon5]

I don't have the appropriate material to measure it, but by the ear it can reproduce these frequencies way louder than harmonics. Everything rattles. Your ears are pressurizing, you feel the room pressurizing and your vision is slightly blurred.

It's the best subwoofer I've ever heard and the owner say the same thing. Deep, accurate, loud bass. I'm curious as how this subwoofer would rate against commercial offers. If someone with alot audio knowledge live near or in NY, maybe you could audition it for me and tell me hehe!

Next time, I'll step up to a more serious driver with better SQ, like the AV series from Acoustic Elegance. It'll need a smaller box, too.

[kornmong]

That is one impressive sub you built, those pis are huge

you should be proud of it I would

[simon5]

Yeah, the only problem is I can't afford it, so I built it for someone else who can afford it hehe!

[johninCR]

RCW,

Are you saying you can hear distortion at 16hz, other than the extra room rattles that distortion in the low frequencies that significant distortion creates? A more valid point is the EBS ported subs are, IMHO, terrible for music, but great for HT due to the extension. Then for music just stuff the port.

[simon5]

Why IYHO EBS ported subwoofers are terrible for music?

[johninCR]

Originally posted by simon5
Why IYHO EBS ported subwoofers are terrible for music?

For lack of a more technical description, they are too loose and sloppy sounding. I have an EBS maelstrom 18. I have it front firing, so I can easily stuff a chunk of foam rubber in the ports for music giving me a great best of both worlds subwoofer.