Don Pearce wrote:

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.

Flat? How does that work then?
For a closed box you want about 4 cubic feet for a Tempest.
With a very large box you want some first-order low-boost to equalise
the response.

On Sat, 17 Jul 2004 18:45:54 +0100, Eiron wrote:

Don Pearce wrote:

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.

Flat? How does that work then?
For a closed box you want about 4 cubic feet for a Tempest.
With a very large box you want some first-order low-boost to equalise
the response.

Not really - that assumes a very big room. With my room, I was happy
that room gain below about 35Hz would flatten out the slowly drooping
response you get when you just use a big cabinet. It won't be exactly
flat, but it will be a heap better than most subs which artificially
prop up one band of frequencies and forget that there is a room in the
equation as well. My system doesn't actually sound as if it has a sub
at all - simply a well-extended frequency response.

d
Pearce Consulting
http://www.pearce.uk.com

Don Pearce wrote:

On Sat, 17 Jul 2004 18:45:54 +0100, Eiron wrote:


Don Pearce wrote:


The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.

Flat? How does that work then?
For a closed box you want about 4 cubic feet for a Tempest.
With a very large box you want some first-order low-boost to equalise
the response.


Not really - that assumes a very big room. With my room, I was happy
that room gain below about 35Hz would flatten out the slowly drooping
response you get when you just use a big cabinet. It won't be exactly
flat, but it will be a heap better than most subs which artificially
prop up one band of frequencies and forget that there is a room in the
equation as well. My system doesn't actually sound as if it has a sub
at all - simply a well-extended frequency response.

Do you have any data to show the effect of opening the doors and
windows on the room gain?
Do you have a sign ooutside:
"Please shut the door to keep the bass in"?

In message , Eiron
writes
Don Pearce wrote:

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.
The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.

Flat? How does that work then?
For a closed box you want about 4 cubic feet for a Tempest.
With a very large box you want some first-order low-boost to equalise
the response.

Maybe the low-rate roll-off of such a low-Q system matches the rise in
LF output due to room effects quite nicely.
--
Chris Morriss

On Sat, 17 Jul 2004 18:56:42 +0100, Chris Morriss
wrote:

In message , Eiron
writes
Don Pearce wrote:

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.
The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.


Stewart screwed up:
According to LSPCad as available from the Adire website, that has an f3 of
about 75 Hz, so you'll need some heavy EQ to get a flat response.
OTOH, if you ceiling mount a Tempest with one voice coil shorted, it's
ruler-flat to 20Hz..................

OOOOOOPS! I misread cu ft for litres!

Should be pretty flat to 30-35Hz, especially if you short one of the
voice coils to optimise the Qts.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 18 Jul 2004 12:35:36 +0000 (UTC), Stewart Pinkerton
wrote:

On Sat, 17 Jul 2004 18:56:42 +0100, Chris Morriss
wrote:

In message , Eiron
writes
Don Pearce wrote:

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.
The whole thing tunes pretty nicely with the room to make an almost
flat response down to something very low indeed.


Stewart screwed up:
According to LSPCad as available from the Adire website, that has an f3 of
about 75 Hz, so you'll need some heavy EQ to get a flat response.
OTOH, if you ceiling mount a Tempest with one voice coil shorted, it's
ruler-flat to 20Hz..................

OOOOOOPS! I misread cu ft for litres!

Should be pretty flat to 30-35Hz, especially if you short one of the
voice coils to optimise the Qts.

The nice thing is that being an IB, it doesn't fall over in a heap
below resonance - it just keeps dropping away smoothly. This itself is
nicely compensated for by the room rising at the same rate.

d
Pearce Consulting
http://www.pearce.uk.com

On Sat, 17 Jul 2004 15:00:06 +0100, Don Pearce
wrote:

As promised here is a picture of my subwoofer. I have pushed a settee
out of the way so it can be seen, and also removed a white cloth
screen that normally covers it. So in use it is totally invisible.

http://www.donepearce.plus.com/odds/sub.jpg

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

Call that a subwoofer? Try this: http://www.klone-audio.com/

And check out '12 Shivas dancing'..................

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 18 Jul 2004 12:22:34 +0000 (UTC), Stewart Pinkerton
wrote:

On Sat, 17 Jul 2004 15:00:06 +0100, Don Pearce
wrote:

As promised here is a picture of my subwoofer. I have pushed a settee
out of the way so it can be seen, and also removed a white cloth
screen that normally covers it. So in use it is totally invisible.

http://www.donepearce.plus.com/odds/sub.jpg

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

Call that a subwoofer? Try this: http://www.klone-audio.com/

And check out '12 Shivas dancing'..................

My goodness. But how is he holding them onto the baffle? Four weedy
little spring clips... they'll be bouncing.

d
Pearce Consulting
http://www.pearce.uk.com

On Sun, 18 Jul 2004 14:54:44 +0100, Don Pearce
wrote:

On Sun, 18 Jul 2004 12:22:34 +0000 (UTC), Stewart Pinkerton
wrote:

On Sat, 17 Jul 2004 15:00:06 +0100, Don Pearce
wrote:

As promised here is a picture of my subwoofer. I have pushed a settee
out of the way so it can be seen, and also removed a white cloth
screen that normally covers it. So in use it is totally invisible.

http://www.donepearce.plus.com/odds/sub.jpg

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

Call that a subwoofer? Try this: http://www.klone-audio.com/

And check out '12 Shivas dancing'..................

My goodness. But how is he holding them onto the baffle? Four weedy
little spring clips... they'll be bouncing.

Nope - basic engineering. With a dipole system, there's little or no
back pressure, so there's only a very small force on the clips.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 18 Jul 2004 16:19:08 +0000 (UTC), Stewart Pinkerton
wrote:

On Sun, 18 Jul 2004 14:54:44 +0100, Don Pearce
wrote:

On Sun, 18 Jul 2004 12:22:34 +0000 (UTC), Stewart Pinkerton
wrote:

On Sat, 17 Jul 2004 15:00:06 +0100, Don Pearce
wrote:

As promised here is a picture of my subwoofer. I have pushed a settee
out of the way so it can be seen, and also removed a white cloth
screen that normally covers it. So in use it is totally invisible.

http://www.donepearce.plus.com/odds/sub.jpg

The driver is a 15 inch Adire Tempest mounted in an 80 cubic foot
concrete cupboard, which extends under a staircase on the other side
of the wall. The mounting board, which replaces the cupboard door, is
18mm MDF, braced extensively with scaffolding board, screwed and glued
edgewise onto it. It is very solid.

Call that a subwoofer? Try this: http://www.klone-audio.com/

And check out '12 Shivas dancing'..................

My goodness. But how is he holding them onto the baffle? Four weedy
little spring clips... they'll be bouncing.

Nope - basic engineering. With a dipole system, there's little or no
back pressure, so there's only a very small force on the clips.

There is still Newtonian reaction from the mass of the cone, plus the
equivalent mass of air. I really think that Brunel would have designed
a fine subwoofer.

d
Pearce Consulting
http://www.pearce.uk.com