Woof woof
 

I have a couple of 12" drivers sitting around doing nothing in the loft.
They are of unknown manufacture with rubber surrounds and (from memory) are
rated at 100Watts or similar. I forget the nominal impedance but they were
fairly standard. I was wondering if it is worthwhile installing them in a
sealed (not ported) enclosure and driving them from a couple of proprietary
ss modules and lp filters as a subwoofer system. I don't especially want to
get involved in T/S parameters and volume calculations and I don't want a
'boom box'...just clean extended bass. Can I just assume the bigger the
better for the enclosure? I would probably use MDF or plywood with braced
sides.

Woof woof
 

On Fri, 6 Apr 2012 19:43:25 +0100, "TonyL"
wrote:

I have a couple of 12" drivers sitting around doing nothing in the loft.
They are of unknown manufacture with rubber surrounds and (from memory) are
rated at 100Watts or similar. I forget the nominal impedance but they were
fairly standard. I was wondering if it is worthwhile installing them in a
sealed (not ported) enclosure and driving them from a couple of proprietary
ss modules and lp filters as a subwoofer system. I don't especially want to
get involved in T/S parameters and volume calculations and I don't want a
'boom box'...just clean extended bass. Can I just assume the bigger the
better for the enclosure? I would probably use MDF or plywood with braced
sides.


Unidentified drivers? Have a good look at them first, particularly the
cone surround. If they are of corrugated paper, you are unlikely to
get any useful bass extension out of them. If they are foam or a
rubber roll, give them a go. You won't go far wrong with a large box,
although you might get better results from measuring the Thiele-Small
parameters and designing a proper box.

How involved do you want to get?

d

Woof woof
 

In article ,
TonyL wrote:
I have a couple of 12" drivers sitting around doing nothing in the loft.
They are of unknown manufacture with rubber surrounds and (from memory)
are rated at 100Watts or similar. I forget the nominal impedance but
they were fairly standard. I was wondering if it is worthwhile
installing them in a sealed (not ported) enclosure and driving them
from a couple of proprietary ss modules and lp filters as a subwoofer
system. I don't especially want to get involved in T/S parameters and
volume calculations and I don't want a 'boom box'...just clean extended
bass. Can I just assume the bigger the better for the enclosure? I
would probably use MDF or plywood with braced sides.

If you have a wood floor you could try just mounting them in that, using
it as an infinite baffle.

--
*I don't suffer from insanity, I enjoy every minute of it *

Dave Plowman London SW
To e-mail, change noise into sound.

Woof woof
 

"TonyL"

I have a couple of 12" drivers sitting around doing nothing in the loft.
They are of unknown manufacture with rubber surrounds and (from memory) are
rated at 100Watts or similar. I forget the nominal impedance but they were
fairly standard. I was wondering if it is worthwhile installing them in a
sealed (not ported) enclosure and driving them from a couple of proprietary
ss modules and lp filters as a subwoofer system. I don't especially want to
get involved in T/S parameters and volume calculations and I don't want a
'boom box'...just clean extended bass. Can I just assume the bigger the
better for the enclosure? I would probably use MDF or plywood with braced
sides.


** There is always an optimum size box for a given bass driver - too big
and you actually loose low frequency efficiency.

Using a free program call " WinISD beta " I tried a few brand name, 12 inch
roll surround, woofers ( with free air resonances between 24 and 32 Hz ) and
found that they all performed OK in a 100 litre sealed box = a cube with
45cm sides.

A nice ball park to be in.


...... Phil

Woof woof
 

Don Pearce wrote:


If they are foam or a
rubber roll, give them a go. You won't go far wrong with a large box,
although you might get better results from measuring the Thiele-Small
parameters and designing a proper box.

Rubber.


How involved do you want to get?


It is just a vague idea right now. They were bought as replacement drivers
for a very old pair of Wharfedale speakers a couple of years back and they
were fine. But then I found some replacement surrounds for the Wharfedale
units and restored them.

Would knowing T/S parameters help much in the case of a sealed enclosure?

My initial idea was just a big rigid box, stuffed with wadding. Box volume
being constrained by the fact that I want to stay married.

Woof woof
 

Dave Plowman (News) wrote:

If you have a wood floor you could try just mounting them in that,
using it as an infinite baffle.


'Hello darling, how did the shopping go? By the way I just cut a couple of
holes in the floor. Mind you don't step in them. The lounge carpet needed
replacing anyway'

Woof woof
 

On Sat, 7 Apr 2012 08:50:33 +0100, "TonyL"
wrote:

Don Pearce wrote:


If they are foam or a
rubber roll, give them a go. You won't go far wrong with a large box,
although you might get better results from measuring the Thiele-Small
parameters and designing a proper box.

Rubber.


How involved do you want to get?


It is just a vague idea right now. They were bought as replacement drivers
for a very old pair of Wharfedale speakers a couple of years back and they
were fine. But then I found some replacement surrounds for the Wharfedale
units and restored them.

Would knowing T/S parameters help much in the case of a sealed enclosure?

My initial idea was just a big rigid box, stuffed with wadding. Box volume
being constrained by the fact that I want to stay married.

For a sealed box, no you don't need to know the T/S parameters. The
question is really one of diminishing returns as you make the box
bigger. This is determined by the stiffness of the speaker suspension
which is specified in T/S as an equivalent box size (smaller box =
stiffer suspension). There is no point making the box much bigger than
this, as the suspension stiffness will take over control.

The advantage of doing the measurements and making a ported box is
that it makes use of the speaker's resonance, coupled to the box/port
resonance to prop up the natural low frequency roll-off for a while,
extending the bass response. The cost is that once roll-off inevitably
sets in, it is much steeper, and the residue of the resonances can
make the bass a bit flabby unless it is all configured just right.
That can always be a future project, of course.

d

Woof woof
 

Don Pearce wrote:

which is specified in T/S as an equivalent box size (smaller box =
stiffer suspension). There is no point making the box much bigger than
this, as the suspension stiffness will take over control.


Understood, thanks.

I do have the basic kit to do T/S so I may have a dabble just to give me a
rough idea of optimum box volume.

Woof woof
 

In article ,
TonyL wrote:
Dave Plowman (News) wrote:

If you have a wood floor you could try just mounting them in that,
using it as an infinite baffle.


'Hello darling, how did the shopping go? By the way I just cut a couple
of holes in the floor. Mind you don't step in them. The lounge carpet
needed replacing anyway'

Your room is totally bare of furniture?

--
*If you must choose between two evils, pick the one you've never tried before

Dave Plowman London SW
To e-mail, change noise into sound.

Woof woof
 

On 07/04/2012 08:53, TonyL wrote:
Dave Plowman (News) wrote:

If you have a wood floor you could try just mounting them in that,
using it as an infinite baffle.


'Hello darling, how did the shopping go? By the way I just cut a couple of
holes in the floor. Mind you don't step in them. The lounge carpet needed
replacing anyway'

"Don't use the downstairs toilet. I've converted it into a transmission line
and the pipe is stuffed with optimally-damped wadding."

--
Eiron.

Woof woof
 

Dave Plowman (News) wrote:
In article ,
TonyL wrote:
Dave Plowman (News) wrote:

If you have a wood floor you could try just mounting them in that,
using it as an infinite baffle.


'Hello darling, how did the shopping go? By the way I just cut a
couple of holes in the floor. Mind you don't step in them. The
lounge carpet needed replacing anyway'

Your room is totally bare of furniture?


'Don't worry, the two 12 inch holes are under the settee. You won't even
know they are there....hello, hello....anyone there?' fx:slam of door, car
engine starts up.

Woof woof
 

In article ,
TonyL wrote:
Dave Plowman (News) wrote:
In article ,
TonyL wrote:
Dave Plowman (News) wrote:

If you have a wood floor you could try just mounting them in that,
using it as an infinite baffle.


'Hello darling, how did the shopping go? By the way I just cut a
couple of holes in the floor. Mind you don't step in them. The
lounge carpet needed replacing anyway'

Your room is totally bare of furniture?


'Don't worry, the two 12 inch holes are under the settee. You won't even
know they are there....hello, hello....anyone there?' fx:slam of door,
car engine starts up.

You could put them under those massive cabinets you're going to build. And
use the cabinets for something useful.

--
*Procrastinate now

Dave Plowman London SW
To e-mail, change noise into sound.

Woof woof
 

"TonyL" wrote in message
...
I have a couple of 12" drivers sitting around doing nothing in the loft.
They are of unknown manufacture with rubber surrounds and (from memory) are
rated at 100Watts or similar. I forget the nominal impedance but they were
fairly standard. I was wondering if it is worthwhile installing them in a
sealed (not ported) enclosure and driving them from a couple of proprietary
ss modules and lp filters as a subwoofer system. I don't especially want to
get involved in T/S parameters and volume calculations and I don't want a
'boom box'...just clean extended bass. Can I just assume the bigger the
better for the enclosure? I would probably use MDF or plywood with braced
sides.

Given the unknown nature of these drivers, there is very little that you can
reasonably assume if your goal is *not* a boom box.

Well, you could build 3 boxes with a 3:1 range of sizes and see which one
sounds best.

At some point, measuring T/S parameters starts looking good.

I don't know about the UK, but in the states you can get a USB gizmo with
software that does full relevant set of driver tests using your PC for under
$100.

Woof woof
 

Arny Krueger wrote:

Given the unknown nature of these drivers, there is very little that
you can reasonably assume if your goal is *not* a boom box.


Fair enough...which is why this project is not so serious and might not even
happen. I am just looking for opinions at this stage.

Are there any clues from a physical inspection that might indicate what I
can expect?

Well, you could build 3 boxes with a 3:1 range of sizes and see
which one sounds best.

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB gizmo
with software that does full relevant set of driver tests using your
PC for under $100.


OK, but that would be somewhat more than I paid for the drivers. I do have
an amp module that goes down to DC as well as other bits of audio gear so I
might have a go at T/S parameters to give me a ballpark figure for the box
volume.

If I started this project would there be any benefit in placing two drivers
in one enclosure and on opposite sides? I know that KEF have done that in
the past.

Woof woof
 

"TonyL"

If I started this project would there be any benefit in placing two
drivers in one enclosure and on opposite sides?


** The same outcome as any other arrangement using two drivers in the one
box - means the box has to have twice the volume.

There * IS * a benefit to be had using two, low cost woofers by mounting
them face to face and connecting the terminals out of phase. The combined
unit has the same resonant frequency but twice the cone mass with the same
cone area, twice the power handling and usually much better linearity that
one woofer does. The box can be half the volume too.

This idea is known as " push pull" or "Isobaric".


..... Phil

Woof woof
 

In article , Phil Allison
scribeth thus

"TonyL"

If I started this project would there be any benefit in placing two
drivers in one enclosure and on opposite sides?


** The same outcome as any other arrangement using two drivers in the one
box - means the box has to have twice the volume.

There * IS * a benefit to be had using two, low cost woofers by mounting
them face to face and connecting the terminals out of phase. The combined
unit has the same resonant frequency but twice the cone mass with the same
cone area, twice the power handling and usually much better linearity that
one woofer does. The box can be half the volume too.

This idea is known as " push pull" or "Isobaric".


.... Phil





Presume that was where the Linn Isobarik was derived from?..
--
Tony Sayer

Woof woof
 

In article , TonyL
wrote:
Arny Krueger wrote:

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB gizmo
with software that does full relevant set of driver tests using your
PC for under $100.


OK, but that would be somewhat more than I paid for the drivers. I do
have an amp module that goes down to DC as well as other bits of audio
gear so I might have a go at T/S parameters to give me a ballpark
figure for the box volume.

Someone else will know the details rather better than myself. But I think
you can estimate some of the basic parameters for a large bass speaker from
some quite simple measurements.

e.g. By using a ruler to measure the displacement of the speaker cone when
you apply a fixed dc voltage. And - with the speaker pointing upwards - how
much displacement a small weight produces. (Rotating from vertical to
horizontal and measuring the displacement will also let you estimate the
mass of the cone, etc.) None of that may be very accurate, but may still be
close enough.

IIRC The "Loudspeaker Design Cookbook" by Vance Dickason explains this in
an appendix. But I may have actually read the details somewhere else. Not
really my topic.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Woof woof
 

On Sun, 08 Apr 2012 16:46:17 +0100, Jim Lesurf
wrote:

In article , TonyL
wrote:
Arny Krueger wrote:

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB gizmo
with software that does full relevant set of driver tests using your
PC for under $100.


OK, but that would be somewhat more than I paid for the drivers. I do
have an amp module that goes down to DC as well as other bits of audio
gear so I might have a go at T/S parameters to give me a ballpark
figure for the box volume.

Someone else will know the details rather better than myself. But I think
you can estimate some of the basic parameters for a large bass speaker from
some quite simple measurements.

e.g. By using a ruler to measure the displacement of the speaker cone when
you apply a fixed dc voltage. And - with the speaker pointing upwards - how
much displacement a small weight produces. (Rotating from vertical to
horizontal and measuring the displacement will also let you estimate the
mass of the cone, etc.) None of that may be very accurate, but may still be
close enough.

IIRC The "Loudspeaker Design Cookbook" by Vance Dickason explains this in
an appendix. But I may have actually read the details somewhere else. Not
really my topic.

Slainte,

Jim

I've found a very good explanatory web page which describes in fair
detail how to measure the T/S parameters. There is a downloadable
spread sheet to put the measurements in and produce a full T/S
parameter set.

http://sound.westhost.com/tsp.htm

I've fed some dummy data in, and the answers are very believable.

d

Woof woof
 

Phil Allison wrote

There * IS * a benefit to be had using two, low cost woofers by
mounting them face to face and connecting the terminals out of
phase. The combined unit has the same resonant frequency but twice
the cone mass with the same cone area, twice the power handling and
usually much better linearity that one woofer does. The box can be
half the volume too.

This idea is known as " push pull" or "Isobaric".


.... Phil


Thanks Phil, just looked it up. Seems like a good way to 'use up' my two
drivers.

Woof woof
 

Don Pearce wrote:
On Sun, 08 Apr 2012 16:46:17 +0100, Jim Lesurf
wrote:

In article , TonyL
wrote:
Arny Krueger wrote:

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB
gizmo with software that does full relevant set of driver tests
using your PC for under $100.


OK, but that would be somewhat more than I paid for the drivers. I
do have an amp module that goes down to DC as well as other bits of
audio gear so I might have a go at T/S parameters to give me a
ballpark figure for the box volume.

Someone else will know the details rather better than myself. But I
think you can estimate some of the basic parameters for a large bass
speaker from some quite simple measurements.

e.g. By using a ruler to measure the displacement of the speaker
cone when you apply a fixed dc voltage. And - with the speaker
pointing upwards - how much displacement a small weight produces.
(Rotating from vertical to horizontal and measuring the displacement
will also let you estimate the mass of the cone, etc.) None of that
may be very accurate, but may still be close enough.

IIRC The "Loudspeaker Design Cookbook" by Vance Dickason explains
this in an appendix. But I may have actually read the details
somewhere else. Not really my topic.

Slainte,

Jim

I've found a very good explanatory web page which describes in fair
detail how to measure the T/S parameters. There is a downloadable
spread sheet to put the measurements in and produce a full T/S
parameter set.

http://sound.westhost.com/tsp.htm

I've fed some dummy data in, and the answers are very believable.


Thanks all. I'll drag one of the units from the loft and try the T/S 'added
mass' measurement method, not having a ready made box yet.

Great site, BTW.

Anybody like to comment on how T/S params translate to box volume if I tried
an isobaric design as mentioned by Phil? Just divide enclosure volume by 2?

Woof woof
 

"TonyL"
Phil Allison

There * IS * a benefit to be had using two, low cost woofers by
mounting them face to face and connecting the terminals out of
phase. The combined unit has the same resonant frequency but twice
the cone mass with the same cone area, twice the power handling and
usually much better linearity that one woofer does. The box can be
half the volume too.

This idea is known as " push pull" or "Isobaric".


Thanks Phil, just looked it up. Seems like a good way to 'use up' my two
drivers.


** You should download WinISD and try it - it is just sooooooo simple to
use.

http://www.linearteam.dk/default.aspx?pageid=winisd

There is a large library of various brand woofers included so you can
immediately use the supplied TS data.

Also, and most importantly, you can vary box volumes and tuning points at
whim and instantly see what the effect is.

In most cases, major reductions in box volume are possible with only small
penalties in flatness and LF cut off points.



...... Phil

Woof woof
 

In message , TonyL
writes
Don Pearce wrote:
On Sun, 08 Apr 2012 16:46:17 +0100, Jim Lesurf
wrote:

In article , TonyL
wrote:
Arny Krueger wrote:

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB
gizmo with software that does full relevant set of driver tests
using your PC for under $100.


OK, but that would be somewhat more than I paid for the drivers. I
do have an amp module that goes down to DC as well as other bits of
audio gear so I might have a go at T/S parameters to give me a
ballpark figure for the box volume.

Someone else will know the details rather better than myself. But I
think you can estimate some of the basic parameters for a large bass
speaker from some quite simple measurements.

e.g. By using a ruler to measure the displacement of the speaker
cone when you apply a fixed dc voltage. And - with the speaker
pointing upwards - how much displacement a small weight produces.
(Rotating from vertical to horizontal and measuring the displacement
will also let you estimate the mass of the cone, etc.) None of that
may be very accurate, but may still be close enough.

IIRC The "Loudspeaker Design Cookbook" by Vance Dickason explains
this in an appendix. But I may have actually read the details
somewhere else. Not really my topic.

Slainte,

Jim

I've found a very good explanatory web page which describes in fair
detail how to measure the T/S parameters. There is a downloadable
spread sheet to put the measurements in and produce a full T/S
parameter set.

http://sound.westhost.com/tsp.htm

I've fed some dummy data in, and the answers are very believable.


Thanks all. I'll drag one of the units from the loft and try the T/S 'added
mass' measurement method, not having a ready made box yet.

Great site, BTW.

Anybody like to comment on how T/S params translate to box volume if I tried
an isobaric design as mentioned by Phil? Just divide enclosure volume by 2?





If you are using the 'added mass' method to measure the TS parameters,
make sure that the mass itself can't move about on the speaker cone. If
this happens you can get a very noisy measurement and poor accuracy. I
have one of those small digital scales which I use to weigh out a
quantity of Blu-Tak (or whatever the equivalent is where you are). I
then form this into a ring which I (carefully!) press into place around
the boundary of the dust cap and the cone. This works well and allow
the measurement to be performed with the L/S vertically aligned,
although I think that the alternative method of measuring in free air
and then in a box of known volume is more accurate. The added mass
method should work well enough for your needs though. Perform the
measurements a few times to act as a 'sanity check'! (I use the 'LIMP'
program from the 'ARTA' suite to measure L/S parameters and get adequate
results).
--
Chris Morriss

Woof woof
 

"TonyL" wrote in message
...
Arny Krueger wrote:

Given the unknown nature of these drivers, there is very little that
you can reasonably assume if your goal is *not* a boom box.


Fair enough...which is why this project is not so serious and might not
even happen. I am just looking for opinions at this stage.

Are there any clues from a physical inspection that might indicate what I
can expect?

Well, you could build 3 boxes with a 3:1 range of sizes and see
which one sounds best.

At some point, measuring T/S parameters starts looking good.


Better than building 3 boxes, certainly.

I don't know about the UK, but in the states you can get a USB gizmo
with software that does full relevant set of driver tests using your
PC for under $100.

OK, but that would be somewhat more than I paid for the drivers. I do have
an amp module that goes down to DC as well as other bits of audio gear so
I might have a go at T/S parameters to give me a ballpark figure for the
box volume.

I think your economic analysis could be improved upon. ;-)

The whole purpose of this project appears to be to create something with
significant value.

The economic justification for project expenses should be based on the value
of the expected result, not the materials cost.

Also, economics probably does not actually have a lot to do with this
project. The greatest value to you would be pride from creating of something
with significant value.

Same argument, two different approaches that probably lead to the same
actions... ;-)

Woof woof
 

Phil Allison wrote:
"TonyL"
Phil Allison

There * IS * a benefit to be had using two, low cost woofers by
mounting them face to face and connecting the terminals out of
phase. The combined unit has the same resonant frequency but twice
the cone mass with the same cone area, twice the power handling and
usually much better linearity that one woofer does. The box can be
half the volume too.

This idea is known as " push pull" or "Isobaric".


Thanks Phil, just looked it up. Seems like a good way to 'use up' my
two drivers.


** You should download WinISD and try it - it is just sooooooo
simple to use.

http://www.linearteam.dk/default.aspx?pageid=winisd

There is a large library of various brand woofers included so you can
immediately use the supplied TS data.

Also, and most importantly, you can vary box volumes and tuning
points at whim and instantly see what the effect is.

In most cases, major reductions in box volume are possible with only
small penalties in flatness and LF cut off points.



..... Phil

Just a heads up....I did find the TS data for my pair of Skytronic bass
drivers online and am looking at various WinISD box designs. According to
WinISD an 'optimum' isobaric+vented design is a mere 122.5 l which is
smaller than I expected.

Woof woof
 

On 28/04/2012 19:01, TonyL wrote:


Just a heads up....I did find the TS data for my pair of Skytronic bass
drivers online and am looking at various WinISD box designs. According to
WinISD an 'optimum' isobaric+vented design is a mere 122.5 l which is
smaller than I expected.

That seems quite high. Do you get 225l for a single driver?
An isobarik box should be half the volume of that for a single driver.

--
Eiron.

Woof woof
 

On 01/05/2012 11:23, Eiron wrote:
On 28/04/2012 19:01, TonyL wrote:


Just a heads up....I did find the TS data for my pair of Skytronic bass
drivers online and am looking at various WinISD box designs. According to
WinISD an 'optimum' isobaric+vented design is a mere 122.5 l which is
smaller than I expected.

That seems quite high. Do you get 225l for a single driver?
An isobarik box should be half the volume of that for a single driver.

Oops That should be 245l. Must be going senile!

--
Eiron.

Woof woof
 

Eiron wrote:
On 01/05/2012 11:23, Eiron wrote:
On 28/04/2012 19:01, TonyL wrote:


Just a heads up....I did find the TS data for my pair of Skytronic
bass drivers online and am looking at various WinISD box designs.
According to WinISD an 'optimum' isobaric+vented design is a mere
122.5 l which is smaller than I expected.

That seems quite high. Do you get 225l for a single driver?
An isobarik box should be half the volume of that for a single
driver.

Oops That should be 245l. Must be going senile!

Yes, 122.5 for isobaric and 245 for single driver.

Here's the TS data I used, culled from some online source:

Driver : Skytronic 902.222
Vas : 129.0
Qts : 0.49
Fs : 29.00
SPL : 88.50
-------------------------------------
Number of drivers : 2 (used as isobarik installation)
Box type : Vented
Box size : 122.5 l
Tuning frequency : 23.77 Hz
Vent : 1 vent(s)
0.273 m length for each
0.102 m round
---------------------------------------

This translates to a box of approximately W0.5m x H0.8m x D0.3m internal
dimensions. Seems not that huge to me considering the SPL -3dB level is at
about 22Hz. But my experience with enclosure design is zero (although I've
built a few from kits).

Woof woof
 

"TonyL"
Eiron wrote:

Just a heads up....I did find the TS data for my pair of Skytronic
bass drivers online and am looking at various WinISD box designs.
According to WinISD an 'optimum' isobaric+vented design is a mere
122.5 l which is smaller than I expected.

That seems quite high. Do you get 225l for a single driver?
An isobarik box should be half the volume of that for a single
driver.

Oops That should be 245l. Must be going senile!

Yes, 122.5 for isobaric and 245 for single driver.

Here's the TS data I used, culled from some online source:

Driver : Skytronic 902.222
Vas : 129.0
Qts : 0.49
Fs : 29.00
SPL : 88.50
-------------------------------------
Number of drivers : 2 (used as isobarik installation)
Box type : Vented
Box size : 122.5 l
Tuning frequency : 23.77 Hz
Vent : 1 vent(s)
0.273 m length for each
0.102 m round
---------------------------------------


** The TS numbers are typical for a budget woofer intended for
sealed box operation - so the " Isobarick" arrangement is ideal,
when you have two on hand.

Tuning a ported box to 24Hz is not advantageous as there is so
little program energy at that frequency. Box tuning corresponds
with a * large minimum* in the excursion of a cone for a given
SPL - so it is good to have that happen at a useful frequency.

Be better use a 75 litre box and tune it to 32 Hz - response is
then +/- 1dB from 105Hz to 32 Hz and down by 3dB at 28Hz.
A pair of 82mm x 345mm ports does the job.



.... Phil

Woof woof
 

Phil Allison wrote:

Be better use a 75 litre box and tune it to 32 Hz - response is
then +/- 1dB from 105Hz to 32 Hz and down by 3dB at 28Hz.
A pair of 82mm x 345mm ports does the job.


Thanks Phil...got the idea.

This is more of a fun/interest project for me. Not sure if I really need
more extended bass since my existing studio monitors came with individual
'calibration certificates' showing almost flat responses down to 50Hz. Might
be good for rattling the windows I guess.

Woof woof
 

"TonyL"
Phil Allison wrote:

Be better use a 75 litre box and tune it to 32 Hz - response is
then +/- 1dB from 105Hz to 32 Hz and down by 3dB at 28Hz.
A pair of 82mm x 345mm ports does the job.


Thanks Phil...got the idea.

This is more of a fun/interest project for me. Not sure if I really need
more extended bass since my existing studio monitors came with individual
'calibration certificates' showing almost flat responses down to 50Hz.
Might be good for rattling the windows I guess.


** Response curves alone prove nothing about a speaker's ability to produce
high SPLs at low frequencies. The latter game depends entirely on effective
moving cone areas and the use of tuned vents as sound producers.

Even in a typical domestic loungeroom, anything less than a 10 inch driver
in a ported box is a joke.

For use with action movies on DVDs, 15 inches is the minimum.

Size does matter.



..... Phil