Hi

I'm building a 1x12" speaker cabinet to use with my guitar amp head. I have
all the thiele/small parameters for my speaker, and have used a program
called BandBox Pro to design the speaker cabinet. I have also used a program
called WinIsd to check and both programs give me similiar results.

I already have built a 150 litre cabinet to use with my speaker. I want to
tune my bassreflex box to 65Hz. The program says that with my rear baffle
thickness of 18mm, and 2 flush ends (I'm using a hole in the rear baffle for
port) I need to make a hole 300mm in diameter, to tune the box to 65Hz.

The port would be larger in diameter than my speaker, which is 279mm. Will
this kind of design work?
The program says that if I use 4 ports, 100mm each is sufficient, will this
work either? Is there any difference?

Thanks for answers!

TT

"TT"

I'm building a 1x12" speaker cabinet to use with my guitar amp head. I
have all the thiele/small parameters for my speaker, and have used a
program called BandBox Pro to design the speaker cabinet. I have also used
a program called WinIsd to check and both programs give me similiar
results.

I already have built a 150 litre cabinet to use with my speaker. I want to
tune my bassreflex box to 65Hz. The program says that with my rear baffle
thickness of 18mm, and 2 flush ends (I'm using a hole in the rear baffle
for port) I need to make a hole 300mm in diameter, to tune the box to
65Hz.

The port would be larger in diameter than my speaker, which is 279mm. Will
this kind of design work?


** Yes.

I built two such tuned cabinets 30 years ago - with 3 x 12 inch, low cost,
16 ohm guitar speakers in a 250 litre box.

With a horn tweeter on top and driven by a Rotel 1210 amplifier, they were
used for a " disco' system by a church social group.

The only complaint I had was there was actually so much bass the tone
controls were turned back to tame it a bit.


The program says that if I use 4 ports, 100mm each is sufficient, will
this work either? Is there any difference?


** Yes it also works and there is very little difference.



..... Phil

"Phil Allison" wrote in message
...

"TT"

I'm building a 1x12" speaker cabinet to use with my guitar amp head. I
have all the thiele/small parameters for my speaker, and have used a
program called BandBox Pro to design the speaker cabinet. I have also
used a program called WinIsd to check and both programs give me similiar
results.

I already have built a 150 litre cabinet to use with my speaker. I want
to tune my bassreflex box to 65Hz. The program says that with my rear
baffle thickness of 18mm, and 2 flush ends (I'm using a hole in the rear
baffle for port) I need to make a hole 300mm in diameter, to tune the box
to 65Hz.

The port would be larger in diameter than my speaker, which is 279mm.
Will this kind of design work?


** Yes.

I built two such tuned cabinets 30 years ago - with 3 x 12 inch, low
cost, 16 ohm guitar speakers in a 250 litre box.

With a horn tweeter on top and driven by a Rotel 1210 amplifier, they were
used for a " disco' system by a church social group.

The only complaint I had was there was actually so much bass the tone
controls were turned back to tame it a bit.


The program says that if I use 4 ports, 100mm each is sufficient, will
this work either? Is there any difference?


** Yes it also works and there is very little difference.



.... Phil

Hi Phil,

Many thanks for your answer! I'll give my speaker cab a try then.

Cheers!

TT

TT wrote:
Hi

I'm building a 1x12" speaker cabinet to use with my guitar amp head. I have
all the thiele/small parameters for my speaker, and have used a program
called BandBox Pro to design the speaker cabinet. I have also used a program
called WinIsd to check and both programs give me similiar results.

I already have built a 150 litre cabinet to use with my speaker. I want to
tune my bassreflex box to 65Hz. The program says that with my rear baffle
thickness of 18mm, and 2 flush ends (I'm using a hole in the rear baffle for
port) I need to make a hole 300mm in diameter, to tune the box to 65Hz.

The port would be larger in diameter than my speaker, which is 279mm. Will
this kind of design work?
The program says that if I use 4 ports, 100mm each is sufficient, will this
work either? Is there any difference?

Thanks for answers!

TT



This is not how guitar speakers are designed. Reflex speakers are
generally poor guitar designs, which should be dropping fairly fast from
about 100Hz, and with some nice hefty peaks up at a few kHz. Go for a
fully sealed box if it is fairly big, or for a smaller cabinet, have
about half of the back panel open.

High fidelity and flat response are NOT what you need for this job.

d

Don Pearce wrote:


This is not how guitar speakers are designed. Reflex speakers are
generally poor guitar designs, which should be dropping fairly fast from
about 100Hz, and with some nice hefty peaks up at a few kHz. Go for a
fully sealed box if it is fairly big, or for a smaller cabinet, have
about half of the back panel open.

High fidelity and flat response are NOT what you need for this job.


This is true. Also, 150 litres is ridiculously large for a 1x 12 guitar speaker. I have a 12" JBL in a 40-litre cabinet for my bass!

The problem with using WinIsd and similar programs is that you must know the target respons of your planned system, i.e. the frequency response you are aiming to achieve. Otherwise, it will often suggest an over-large box that is useless. Which, if I am not very much mistaken, is what you are going to end up with.

Use a speaker designed for guitar and get the manufacturer's cabinet recommendations. Easy.

Stephen

Stephen McLuckie wrote:
Don Pearce wrote:


This is not how guitar speakers are designed. Reflex speakers are
generally poor guitar designs, which should be dropping fairly fast
from about 100Hz, and with some nice hefty peaks up at a few kHz. Go
for a fully sealed box if it is fairly big, or for a smaller cabinet,
have about half of the back panel open.

High fidelity and flat response are NOT what you need for this job.


This is true. Also, 150 litres is ridiculously large for a 1x 12 guitar
speaker. I have a 12" JBL in a 40-litre cabinet for my bass!

The problem with using WinIsd and similar programs is that you must know
the target respons of your planned system, i.e. the frequency response
you are aiming to achieve. Otherwise, it will often suggest an
over-large box that is useless.

WinISD will allow you to tweak the box and port size, and show the
frequency response graph.
So there's no problem.

--
Eiron.

"Eiron"

WinISD will allow you to tweak the box and port size, and show the
frequency response graph.
So there's no problem.


** Exactly.

The default (ideal) response curve and box volume / tuning frequency
supplied by WinISD are only a starting point.

One can usually almost halve the box volume and fiddle with the tuning
frequency and still get an perfectly acceptable result with most modern LF
drivers.

Play the same game with 4th order BP boxes and you will have lots of fun.




...... Phil

Eiron wrote:


WinISD will allow you to tweak the box and port size, and show the
frequency response graph.
So there's no problem.


It is a problem if you end up putting a 12" driver in a 150 litre cabinet.

"Stephen McLuckie" wrote in message
et...
Eiron wrote:


WinISD will allow you to tweak the box and port size, and show the
frequency response graph.
So there's no problem.


It is a problem if you end up putting a 12" driver in a 150 litre cabinet.

I agree the box is big, but I don't have a problem with the size, 150 litres
is fine to me. It's all very experimental. If I don't like the big box, I
can throw it away and make a smaller one.

TTT

"Eiron"

WinISD will allow you to tweak the box and port size, and show the
frequency response graph.
So there's no problem.


** There IS one trap though - you must have an amplifier with low output
impedance( ie good damping factor) or the response graph model used by
simulators like WinISD are gonna be hopelessly wrong.

Most SS bass guitar and guitar amps have low output impedance - but some
are deliberately made to have a high one. Which is which is not east to
tell as makers very rarely spec it.

With valve guitar amps, the vast majority have high output impedance (
anywhere from 5 to 100 ohms) though again exceptions exist there too.



...... Phil