"Stewart Pinkerton" wrote in message
...
Besides, SWMBO doesn't want a hole in the ceiling!

You do raise an interesting point, however, as I'm having
trouble
running the numbers as tpo how small the hole in the ceiling
can be
before it causes problems with either port noise or turning the
manifold into a reflex cabinet. Any advice on that mattter from
your
own experience?

There are two things to consider. Manifold cross sectional area
and opening size.

In a nutshell, if the manifold's cross sectional area and opening
is less than the driver's summed Sd, then it becomes a bandpass
design with a fairly low tuned low pass filter. Once the Sd/area
rises above about 3:1 you can start getting harmonic distortion.
The opening L:W ratio should be less than about 1.3:1 to keep
slit diffraction from nonlinear loading of the drivers and to
average out internal standing waves.

However, my opening is 16"x16" or only 1/2 the total Sd. It's a
huge hole but my ceiling is 12 feet up and painted black (front
projection theater) so the hole is essentially invisible even
with the lights on. Even at obscene levels I hear no port noise
and it doesn't seem to affect the frequency response or add
harmonics (ECM8000 measurement mic).

One IB forum member is using two 4"x10" HVAC floor vents with two
Dayton 15" drivers due to wife factors. Even without considering
the grill obstruction this is less than 1/3 Sd so would seem bad.
However, he won't stop gushing about how great it is. He has
some pictures of his manifold/vents he
http://users.rcn.com/mjrjunk/

Do you have Thiele Small numbers for the AV15? I might take you
up on
that if I can't source them any other way. As you say,
displacement is
everything at LF.

The AV15s were going for $165 USD during preorder but that's over
and they're now $205. Still a great bargain for IB but a little
more pricey.

http://www.stryke.com/AVseries.html
Fs: 22.39 Hz
Qms: 5.293
Qes: .517
Qts: .471
Vas: 140.1L
2.95 ohm
Z: 4 ohm
(dual 2ohm)
BL: 16.84 Tm
Cms: .143 mm/N
Mms: 353g
Rms: 9.391kg/s
Le: 3.5mH
Pe: 500W cont.
2.83V: 91.15dB
Xmax: 23 mm
Xsus: 30 mm
Sd: 830 sq cm
Vd: 3.8 L

On Fri, 26 Dec 2003 02:47:23 -0600, "Rusty Boudreaux"
wrote:

"Stewart Pinkerton" wrote in message
...
Besides, SWMBO doesn't want a hole in the ceiling!

You do raise an interesting point, however, as I'm having trouble
running the numbers as tpo how small the hole in the ceiling can be
before it causes problems with either port noise or turning the
manifold into a reflex cabinet. Any advice on that mattter from your
own experience?

There are two things to consider. Manifold cross sectional area
and opening size.

In a nutshell, if the manifold's cross sectional area and opening
is less than the driver's summed Sd, then it becomes a bandpass
design with a fairly low tuned low pass filter.

Aah! Of course. I'd completely forgotten bandpass principles! Doh!

Once the Sd/area
rises above about 3:1 you can start getting harmonic distortion.
The opening L:W ratio should be less than about 1.3:1 to keep
slit diffraction from nonlinear loading of the drivers and to
average out internal standing waves.

Hmmmm. Not so sure about this one, as there won't be any standing
waves in the 150Hz passband, but I take your point about possible
distortion from pressure loading - that was my main concern.

However, my opening is 16"x16" or only 1/2 the total Sd. It's a
huge hole but my ceiling is 12 feet up and painted black (front
projection theater) so the hole is essentially invisible even
with the lights on. Even at obscene levels I hear no port noise
and it doesn't seem to affect the frequency response or add
harmonics (ECM8000 measurement mic).

Ah, OK. I'd be using a an 11" x 11" hole for that ratio, but it's a
white ceiling 9 feet up, so rather more visible!

One IB forum member is using two 4"x10" HVAC floor vents with two
Dayton 15" drivers due to wife factors. Even without considering
the grill obstruction this is less than 1/3 Sd so would seem bad.
However, he won't stop gushing about how great it is. He has
some pictures of his manifold/vents he
http://users.rcn.com/mjrjunk/

Thanks, that's exactly the kind of thing I was looking for. I'll start
running the numbers again for a 'semi-bandpass' design, but like you
say, that looks like an effective ratio of around 4:1 with the grilles
on. I probably could get away with a couple of large ventilation
grilles, Anne could claim that we've installed air-con! :-)

It does strike me that I'd need to be careful about turbulence noise,
but that's a problem for another day......

Do you have Thiele Small numbers for the AV15? I might take you up on
that if I can't source them any other way. As you say, displacement is
everything at LF.

The AV15s were going for $165 USD during preorder but that's over
and they're now $205. Still a great bargain for IB but a little
more pricey.

http://www.stryke.com/AVseries.html
Fs: 22.39 Hz
Qms: 5.293
Qes: .517
Qts: .471
Vas: 140.1L
2.95 ohm
Z: 4 ohm
(dual 2ohm)
BL: 16.84 Tm
Cms: .143 mm/N
Mms: 353g
Rms: 9.391kg/s
Le: 3.5mH
Pe: 500W cont.
2.83V: 91.15dB
Xmax: 23 mm
Xsus: 30 mm
Sd: 830 sq cm
Vd: 3.8 L

Thanks Rusty, I did find them after trawling the Stryke site. I've
e-mailed them for a quote, as their on-line store implies world-wide
shipping, so we'll see what transpires. I must say that they are the
coolest *looking* drivers around, with those big alloy cones!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
Thanks Rusty, I did find them after trawling the Stryke site.
I've
e-mailed them for a quote, as their on-line store implies
world-wide
shipping, so we'll see what transpires. I must say that they
are the
coolest *looking* drivers around, with those big alloy cones!

I think the Tumults are more impressive but the AV15s are
certainly awe inspiring! During the first preorder (over a year
ago) the drivers came with a logo on the cone by default. You
may have to specify no logo. Stryke is essentially a one man
shop (John E. Janowitz). I think his wife just had a baby so he
may be somewhat tied up. His phone is 920-469-9198 if all else
fails. There's also a Stryke web forum.
http://forum.stryke.com/

On Fri, 26 Dec 2003 16:35:18 -0600, "Rusty Boudreaux"
wrote:

"Stewart Pinkerton" wrote in message
...
Thanks Rusty, I did find them after trawling the Stryke site.
I've
e-mailed them for a quote, as their on-line store implies
world-wide
shipping, so we'll see what transpires. I must say that they
are the
coolest *looking* drivers around, with those big alloy cones!

I think the Tumults are more impressive but the AV15s are
certainly awe inspiring! During the first preorder (over a year
ago) the drivers came with a logo on the cone by default. You
may have to specify no logo. Stryke is essentially a one man
shop (John E. Janowitz). I think his wife just had a baby so he
may be somewhat tied up. His phone is 920-469-9198 if all else
fails. There's also a Stryke web forum.
http://forum.stryke.com/

Thanks for that, Rusty. I must say, the recent discussions on the
Stryke forum are *not* encouraging to a potential purchaser!

I appreciate the problems if he's a 'one man band' and a new dad, but
at the end of the day I'll need products, not promises............
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
On Fri, 26 Dec 2003 16:35:18 -0600, "Rusty Boudreaux"
wrote:

"Stewart Pinkerton" wrote in message
...
Thanks Rusty, I did find them after trawling the Stryke site.
I've
e-mailed them for a quote, as their on-line store implies
world-wide
shipping, so we'll see what transpires. I must say that they
are the
coolest *looking* drivers around, with those big alloy cones!

I think the Tumults are more impressive but the AV15s are
certainly awe inspiring! During the first preorder (over a year
ago) the drivers came with a logo on the cone by default. You
may have to specify no logo. Stryke is essentially a one man
shop (John E. Janowitz). I think his wife just had a baby so he
may be somewhat tied up. His phone is 920-469-9198 if all else
fails. There's also a Stryke web forum.
http://forum.stryke.com/

Thanks for that, Rusty. I must say, the recent discussions on the
Stryke forum are *not* encouraging to a potential purchaser!

I appreciate the problems if he's a 'one man band' and a new dad, but
at the end of the day I'll need products, not promises............
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Keep us informed on the project and it's results.

I'm planning a project with a single Shiva in a ported box of either 3.6 or
4.8 cu ft. f3 predictions are 25 and 21 Hz, respectively.

Leaning towards the smaller box for WAF nad with room gain it should get to
at least 20 Hz in the room it will be used in.

"Stewart Pinkerton" wrote in message
...
I appreciate the problems if he's a 'one man band' and a new
dad, but
at the end of the day I'll need products, not
promises............

I've been absent from the forum for awhile. It does seem like
John's backed up right now but trying to work out the backlog.
Apparently Stryke will be changing it's name Jan 1st due to
trademark issues. Looks like Acoustic Elegance is the leading
candidate.

FYI, I ordered my AV15s during the first preorder back in Oct
'02. I believe John ordered 500 AV15s from TC Sounds with the
intent to have several hundred left over to keep in stock. TC
Sounds messed up the voice coils (single 4 ohm instead of dual 2
ohm) which delayed shipments until Jan '03. By the time they
shipped John had sold out of all the drivers! Since then Kyle at
www.acoustic-visions.com has been keeping drivers in stock but
they're currently out due to waiting on the new design (dual
spider) but Kyle won't ship outside USA.

If you can handle the wait and get the UK shipping worked out the
AV15 are certainly worth it. If not, go for the Tempest. A 3x2
array of Tempests will be as good as four AV15s or three Tumults


I previously had a Velodyne F1800R and thought it was king. The
IB wipes the floor with it in every way...including cost. I had
planned on performing a level matched DBT but there was no need.
The F1800 now sits behind the computer.