DrWho how does this combination sound ?

[dtel]

I've been useing it for a couple years and got used to it. How does it rate considering it only cost about $350, would I be better off building something new or could I inprove this one with a bigger amp or different speaker ? Or just add another, sub for movies. 50 / 50 music / movies

5 CF cabinet ported, 4" port 12" long. Tuned to 18.1

Shiva Classic 12" DVC Displacement: 3 liters

Specs taken with voice coils in parallel.
Re 2.9 ohms

Le 2.12 mH

Qms 6.5

Mms 124 grams

Qes .40

Cms .47 mm/N

Qts .38

Fs 21 Hz

Sd 481 cm^2

Vas 151 liters

BL 10.9 N/A

Xmax 16.6 mm one way

EBP 51.2

SPL 87.3 dB @ 1W/1m

VC Dia. 2"

Power Rating 650W Total

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Amp is AVA 250

Power 8 ohms, 180W - 4 ohms, 270W

Crossover Frequency 40 Hz to 160 Hz, second order Butterworth

Frequency Response 16 Hz to 160 Hz, +1/-3 dB

Phase Rotation 0 to 180 degrees

Gain Range 30 dB

EQ Filter Q 0.96

EQ Filter Frequency 18Hz

THD Less than 0.1% THD at rated power

S/N Greater than 103 dB at rated power

Weight 12 pounds

Overall Size10.5" wide by 10.5" high

Mounting Cutout 9.25" wide by 9.25" high

Mounting/Front Depth 3.5"/1"

Input Voltage 115/230V switchable, 50/60 Hz

High Pass Outputs First order Butterworth, 125 Hz (on speaker level outputs only)

[colterphoto1]

I've heard this monster- it sounds GREAT in your room. And it weighs a TON- when Dtel builds something, believe me- it STAYS BUILT!

Why worry about specs? You like it right?

[DrWho]

Crap, the forum being down last night lost me my post.... []

Did
you design this sub yourself or work off manufacturer's recommended
enclosures? Overall the design looks very solid, covering all the
bases. For what it's worth, the tuning point with that port and cabinet
volume is actually 21Hz. The Q=0.96 high-pass filter at 20Hz built into
your amplifier works well to control the cone-excursion of the driver.
At first I thought the filter was set at too low of a frequency, but
once you start predicting non-linear behavior (when excursion limits
are important) the filter becomes a perfect match. In fact, I was
rather surprised as I didn't make the non-linear predictions to make
the system look better - I worked off general trends I've read about
elsewhere. Assuming the design came from somewhere it shows that my
predictions that I pull outta my butt are somewhat close and that the
person designing the system had these variables in mind. If I were to
complain about anything, it'd be the peak port velocity of around
40m/s. Of course, this happens when the sub is blasting at its peak
output of 118dB (when measured at 1m in a corner) - I wonder how often
that occurs [] The port compression also helps to damp a peak that
starts to rise around 40Hz and depending on the acoustics of your room
might even be beneficial to the nature of the room gain.

Just for kicks, here is the plot with the linear and nonlinear behavior predictions:

Both
are showing peak output achieved with 230W of power. Add 6dB to get an
idea for the in-room response. Here's a list of non-linear variables I
manually entered:

The voice coil increases in temperature when
you pump more power through it, which effectively raises the resistance
in the wire. A normal vented system has two impedance peaks about an
octave above and below the tuning point, which means those frequencies
are going to be attenuated less. This is realized in the frequency
response as peaks at those frequencies - which we mostly see at 35Hz.
The above is predicted with 150 degrees F of temp rise.

As we start pumping more air through the port, its resistance goes
up (kinda like trying to blow more air through a small straw).
Eventually the port will get to a point where more air cannot go
through and the frequency response will look identical to a normal
sealed enclosure...basically as if the tuning point was moving lower in
frequency. At 40m/s, I chose a port compression that was half-way
between the linear ported and sealed enclosure systems. I think it
would equate to about 3dB of port compression which is inline with
numbers I've been quoted from other engineers that get to actually
measure this stuff. I know the port nonlinearity isn't conducive to low
frequency extension, but moving to a different port with less
compression is going to throw off the balance of the system - requiring
a slightly smaller enclosure and a higher frequency for the filter on
the amp - effectively accomplishing the same thing, but sacrificing a
little more extension at lower signal levels...

Also, I went ahead and used 75% of the Bl and VAS which correspond
to how these factors are rated (peak excursion is usually around the
75% range). The curve looks like a table top and drops like a rock
above the excursion limits so this number is a bit conservative. It's
basically responsible for most of the power compression losses. I
didn't go as heavy on the power compression in the above prediction,
but I would expect the green output to require at least 400W to achieve
(meaning that it can only happen in transients). I also modeled a slight
decrease in the effective piston diameter (80%) which again brings the
efficiency down a bit.

I know them's a lot of words to say something looks very good
- and it's almost pointless if your ears are satisfied. The "science"
(more like magic) is there to fix things that your ears don't like -
and it usually works well because the science was built off what our
ears told us in the first place. To be honest, I was hoping to come up
with a small little thing to change, but I'd argue your system is far
beyond the capabilities of simplified prediction algorithms and my
"ability" to guess real behavior. But at the same time, it's always
comforting to know when the predictions look good, and it's fair to
assume that the predictions are somewhat accurate (or else they
wouldn't be getting used so much).

But only $350?!? You must have scored some killer deals. [Y]

[DrWho]

Why worry about specs? You like it right?

Exactly [Y][Y]

[Arky]

Why worry about specs? You like it right?

Exactly [Y][Y]

And he said it in 8 words! HeeHee ya know I luv ya Who.[{]

[DrWho]

And to think I wrote all that out twice!
*bows head in shame*

[dtel]

Sorry to ask a question then not come back but I got sick.

DrWho it was one of their plans at Adire Audio. Before when you would pick a driver from them, there were 3 different plans for tuning. I picked the one that was for HT ?

As for as a good deal they are even cheaper right now, The driver is on sale for $99 and the amp Adire Audio AVA250 is $ 179.

The plans for the whole thing were over 3 years old so I guess it doing OK.

Thanks

[DrWho]

Hey no worries - glad to see you back. Hope all is going well with the recovery.

Btw, were you looking to improve upon your existing situation or just wondering about your config? At those prices you might consider building another one for stereo subwoofage. I'm not sure if I asked already, but is your port flared?

[dtel]

Yes DrWho it's flared, it's the the black plastic ones like you see on different sites, the ends are slid on and glued after you cut the tube to the correct length.

[colterphoto1]

I told ya it sounded good- thanks for the chuckle Arky and Who!

Yes Dtel, what are you hoping to achieve? I think your room sounds good, it' certainly broken up enough. The side windows and the double door to the bedroom might be acoustical anomalies and that concrete floor could use a thicker rug. If I did anything in your system it would be acoustics. uh dude, it ROCKS, c'mon 6x Fortes? And those CWIII's - how can you go wrong? Ok, maybe a more modern HT receiver (I just got the 2600, will let you know)

And Christy might like a nice fluffy rug to keep her tootsies warm. []

[colterphoto1]

btw Doc, thaks for the confirmation. I was sticking my neck out saying how good it sounded. If your curves would have been trash, my reputation would have been ruined here! LOL

[DrWho]

lol!

Don't forget the possibility that I have no clue what I'm doing with the curves. I would have just chalked it up as a limitation of the model if it didn't agree [] How's that for faith in the model?

[dtel's wife]

I just read this thread. You guys never cease to make me laugh. Dr. Who is the straight man, Michael is the comedian and dtel rides the middle. With input from Arky and a few others here and there....you are all too funny.

And, yes it does sound good, and yes I would like a huge rug to keep my tootsies warm and yes, when dtel builds something it is built to last...

[colterphoto1]

I just read this thread. You guys never cease to make me laugh. Dr. Who is the straight man, Michael is the comedian and dtel rides the middle. With input from Arky and a few others here and there....you are all too funny.

And, yes it does sound good, and yes I would like a huge rug to keep my tootsies warm and yes, when dtel builds something it is built to last...

yup, that's me alright- in the words of Jim Morrison "always a playground instructor, never a killer"