[R]

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I know there are some speaker experts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

[Phil Allison]

"R"

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.


** That is a very small cabinet - less than 2 cubic feet.

The way to "port" it is to make a shelf under the speaker.

The front opening is full width, maybe 2 or 3 inches high with an internal
partition about 10 inches deep.

Adjust depth for best sound.





......... Phil

[Patrick Turner]

R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I know there are some speaker experts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

Having a 12" speaker in a 1.1 cu.ft box is like having an elephant in
the loungeroom;
If it ****s, you ARE in trouble.

I fear you are asking for solution which is impossible to
easily provide.

The speaker should be left alone. Perhaps placing a couple of
polyester wool bats inside may tame reflections from inside the box the
outside through the cone.
A port may make things sound worse.
Perhaps you should consider buying another to give a good reflex
box match, or if you want a ported box with that driver you have, then
you'd need to apply the speaker program WINisd which is a free download
to find out ideal ported box design for that driver.

I recently re-engineered a pair of AR12 with 10" bass drivers in 2
cu.ft.sealed boxes.
Bass became more extended when i added a plinth of 3" under the exising
box, and
a port under the box of about 14" long.
This way the port volume didn't make the internal box volume any
smaller.
Even the guy's wife thought the result was a marvel.

The box volume was barely big enough for the driver to get a good match.

Many makers used closed boxes because reflexed sounded worse, and
besides, it was easy to
lie to the public about bass performance, and save on
construction costs, transport costs by keeping the box undersize, and
not boring the
extra port hole and fixing in a cardboard tube for the port.

Speaker mass production is about marketting, not an application of very
best practices
at all times; best practices are something likely to send a maker broke,
or most certainly likely to make the shareholders very unhappy.

Patrick Turner.

[Mogens V.]

R wrote:
What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

If the driver is good, why not build a larger box for it?
If you _must_ modify it, try a slotted back approach, and provide some
dampening across the slots. No matter what you do, you'll most likely
end up with either a bumpy upper-bass ride or other artefects.
As already mentioned here, the box is rather small for any changes.

--
Kind regards,
Mogens V.

[[email protected]]

On Mon, 05 Mar 2007 04:50:13 -0500, R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I know there are some speaker experts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

If this is a guitar amp speaker - just take the back off... replace it with a
partial plate to hold the jacks...

If it's for a synth or something - you need a bigger box!

Of course, it also depends on the speaker... telling us the make and model and
exact intended purpose would help...

[R]

On Mon, 05 Mar 2007 11:28:51 GMT, Patrick Turner
wrote:

R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I fear you are asking for solution which is impossible to
easily provide.

Yeah, I knew that. I'm looking for any possible improvement.

The speaker should be left alone. Perhaps placing a couple of
polyester wool bats inside may tame reflections from inside the box the
outside through the cone.
A port may make things sound worse.

The existing cabinets are closed, with internal polywool padding. They
don't sound very good at all. Could be the particular speakers (I've
tried Altec 417s and EV SRO's ...see below).

I was considering just sawing out the entire back to let the speaker
at least breathe, though the baffle size would not lend to spectacular
sound.

That's a drastic measure, and of course could have its own set of
problems. So I'm looking more for any interim compromises before doing
that. The ports, as suggested elsewhere,

Perhaps you should consider buying another to give a good reflex
box match

That would be ideal, but unfortunately there is not enough space. That
was the reason that these cabs exist in the first place.

The two speakers mentioned (Altec 417, EV SRO) are/were not available
in smaller sizes, so 12" is it. Again, the purpose is for nonlinear
musical instrument monitoring, mostly guitar, so exact linearity is
not imperative. Fender Deluxe Reverb amps get by with open-back cabs
with just a bit more baffle area than these. But again, I thought
there may be a better way than completely opening the backs.

, or if you want a ported box with that driver you have, then
you'd need to apply the speaker program WINisd which is a free download
to find out ideal ported box design for that driver.

There's a good lead, thanks! I just tried the program. Strange
results (unexpected linearity!), so I'm probably doing something
wrong.

I started with the ALtec 417, as they did not have Theile-Small
presets for EV SRO speakers (old alnicos with large white 'coffee can'
magnet...anyone know the T-S params?).

Entered approx 15" x 15" x 14" for size, using both ported and
unported models. In all plots, the response is surprisingly UNpeaky,
with an expected bass cutoff at around 80hz to 100hz. Bass for guitar
doesn't really need to extend below 80hz, so that is not a concern.

I don't understand why the program indicates reasonable response in
other respects though. I had expected drastic resonant peaks in low
mids. That's what the closed cab sounds like anyway.

Also, vent lengths show as a fraction of an inch, no matter what size
vent I specify.

Thanks, Patrick

[R]

On Mon, 05 Mar 2007 18:01:59 +0100, "Mogens V."
wrote:

R wrote:
What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

If the driver is good, why not build a larger box for it?

The speakers themselves are great for what I want to do.
Unfortunately, there is limited space for the cabinets in this
particular case.

If you _must_ modify it, try a slotted back approach, and provide some
dampening across the slots. No matter what you do, you'll most likely
end up with either a bumpy upper-bass ride or other artefects.

I'm not familiar with slotted back. Are there examples somewhere?
As mentioned in a previous post, I tried WinISD at the suggestion of
Patrick. It shows surprisingly smooth rolloff curves for some reason.
Again, I must be entering some wrong params, as the actual sound is
about what you indicated, with peaky sounding low-mid/upper bass.

[R]

On Mon, 05 Mar 2007 22:32:26 -0500,
wrote:

On Mon, 05 Mar 2007 04:50:13 -0500, R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I know there are some speaker experts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

If this is a guitar amp speaker - just take the back off... replace it with a
partial plate to hold the jacks...

Yes, primarily for guitar, and I was just going to saw the backs of
the cabinets out (they are one piece. Speakers are front-mounted).

The cabinets are actually hooked into a stereo tube amp with
relay-switched preamp circuits. I'd like to keep it as versatile as
possible, considering that it could be useful for keyboards, etc.
Still I'd sacrifice some low-end response to keep sharp resonance
minimized.

It would be great if I could get a handle on things via computer
modelling, but I don't think the response curves that I've got from
WinISD so far are representative of what's actually happening.

If it's for a synth or something - you need a bigger box!

Of course, it also depends on the speaker... telling us the make and model and
exact intended purpose would help...

I originally tried Altec 417-C's. Changed to EV SRO speakers. Both are
old huge-magnet alnicos that are long obsolete. I believe the Altecs
were sometimes used in hifi gear at one time. Not sure about SROs.
Both are great speakers, and both weigh close to 25 lbs (Altec a bit
lighter I think).

I'm sure you've seen the SROs. Similar to the ones from this Ebay
auction:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=160085867944

There was a preset in WinISD for an Altec 417 model, though I believe
it may have been one of the later ceramic models. No luck with the EV
SRO (it did have later ceramic EV models). You'd think that would have
been there, given the legendary status of SRO speakers.

[Patrick Turner]

R wrote:

On Mon, 05 Mar 2007 11:28:51 GMT, Patrick Turner
wrote:

R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I fear you are asking for solution which is impossible to
easily provide.

Yeah, I knew that. I'm looking for any possible improvement.

The speaker should be left alone. Perhaps placing a couple of
polyester wool bats inside may tame reflections from inside the box the
outside through the cone.
A port may make things sound worse.

The existing cabinets are closed, with internal polywool padding. They
don't sound very good at all. Could be the particular speakers (I've
tried Altec 417s and EV SRO's ...see below).

I was considering just sawing out the entire back to let the speaker
at least breathe, though the baffle size would not lend to spectacular
sound.

That's a drastic measure, and of course could have its own set of
problems. So I'm looking more for any interim compromises before doing
that. The ports, as suggested elsewhere,

Perhaps you should consider buying another to give a good reflex
box match

That would be ideal, but unfortunately there is not enough space. That
was the reason that these cabs exist in the first place.

The two speakers mentioned (Altec 417, EV SRO) are/were not available
in smaller sizes, so 12" is it. Again, the purpose is for nonlinear
musical instrument monitoring, mostly guitar, so exact linearity is
not imperative. Fender Deluxe Reverb amps get by with open-back cabs
with just a bit more baffle area than these. But again, I thought
there may be a better way than completely opening the backs.

, or if you want a ported box with that driver you have, then
you'd need to apply the speaker program WINisd which is a free download
to find out ideal ported box design for that driver.

There's a good lead, thanks! I just tried the program. Strange
results (unexpected linearity!), so I'm probably doing something
wrong.

I started with the ALtec 417, as they did not have Theile-Small
presets for EV SRO speakers (old alnicos with large white 'coffee can'
magnet...anyone know the T-S params?).

If you don't have the TS parameters, or know the fiddly way to measure
them using a known volume sealed box of about 2cu ft, you are stuck.


Entered approx 15" x 15" x 14" for size, using both ported and
unported models. In all plots, the response is surprisingly UNpeaky,
with an expected bass cutoff at around 80hz to 100hz. Bass for guitar
doesn't really need to extend below 80hz, so that is not a concern.

Just what real world response you might get is anyone's guess all the
same.
The subjective "constricted tone" is probably due
to the harmonics and tones well above the bass F where the box size s
important.

I don't understand why the program indicates reasonable response in
other respects though. I had expected drastic resonant peaks in low
mids. That's what the closed cab sounds like anyway.

The WINISD only really gives some idea for box matching in the critical
area below 100Hz. The makers response plots for real world F response
are never factored in to the driver data.



Also, vent lengths show as a fraction of an inch, no matter what size
vent I specify.

The program says you don't need more than a hole in the cabinet wall.

Not every speaker needs a long port, but if one is added,
the box resonant F goes lower as the port L reduuces.
I am surprised with the results you have got, and that there isn't a
peaky response
indicated between 100 and 50Hz, and that a long port isn't needed.

You can select different port lengths and box sizes, or show sealed or
vented
for the same driver.

Patrick Turner.


Thanks, Patrick

[Mogens V.]

R wrote:
On Mon, 05 Mar 2007 18:01:59 +0100, "Mogens V."
wrote:


R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

If you _must_ modify it, try a slotted back approach, and provide some
dampening across the slots. No matter what you do, you'll most likely
end up with either a bumpy upper-bass ride or other artefects.


I'm not familiar with slotted back. Are there examples somewhere?
As mentioned in a previous post, I tried WinISD at the suggestion of
Patrick. It shows surprisingly smooth rolloff curves for some reason.
Again, I must be entering some wrong params, as the actual sound is
about what you indicated, with peaky sounding low-mid/upper bass.

Slotted back is fairly non-critical. Just drill a series of half inch
holes or so at the length of, say, 4-5 inches, and cut the wood between
them to have a slot. Doesn't have to be a perfect slot.
Repeat to have 4-5 slots.
You can dampen the slots with some mineral wool or such to tune the
effect domewhat.

Since you've already mostly made up your mind to cut off the back, maybe
try the slots first. If you do cut cut off the back, do note that an
open baffle box require a speaker with a somewhat stiff suspension and a
not too weak magnet (I do't know your Altec driver), else you may have
excessive cone movements - especially if you crank up the bass and play
staccato bass strings notes while dampening strings with the hand.
This technique can produce sound somewhat below the E6 80hz string.

--
Kind regards,
Mogens V.

[[email protected]]

On Tue, 06 Mar 2007 01:40:53 -0500, R wrote:

On Mon, 05 Mar 2007 22:32:26 -0500,
wrote:

On Mon, 05 Mar 2007 04:50:13 -0500, R wrote:

What is the best way to port a -very- small cabinet? It is about
16"x16" across the baffle side. 14" deep. The speaker itself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
the speaker from sounding constricted, as it does with a closed
cabinet.

I know there are some speaker experts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

If this is a guitar amp speaker - just take the back off... replace it with a
partial plate to hold the jacks...

Yes, primarily for guitar, and I was just going to saw the backs of
the cabinets out (they are one piece. Speakers are front-mounted).

The cabinets are actually hooked into a stereo tube amp with
relay-switched preamp circuits. I'd like to keep it as versatile as
possible, considering that it could be useful for keyboards, etc.
Still I'd sacrifice some low-end response to keep sharp resonance
minimized.

It would be great if I could get a handle on things via computer
modelling, but I don't think the response curves that I've got from
WinISD so far are representative of what's actually happening.

If it's for a synth or something - you need a bigger box!

Of course, it also depends on the speaker... telling us the make and model and
exact intended purpose would help...

I originally tried Altec 417-C's. Changed to EV SRO speakers. Both are
old huge-magnet alnicos that are long obsolete. I believe the Altecs
were sometimes used in hifi gear at one time. Not sure about SROs.
Both are great speakers, and both weigh close to 25 lbs (Altec a bit
lighter I think).

I have speakers like that, and believe me, they are only good for guitar! The
only box you could use them in to get bass would be a 10 cubic foot bin, a total
waste of time I think, since the bass wouldn't be very impressive. Those
speakers are resonant up around 50 or 60 Hz, you could beat them with a modern
8".

I'm sure you've seen the SROs. Similar to the ones from this Ebay
auction:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=160085867944

There was a preset in WinISD for an Altec 417 model, though I believe
it may have been one of the later ceramic models. No luck with the EV
SRO (it did have later ceramic EV models). You'd think that would have
been there, given the legendary status of SRO speakers.

Win ISD won't be of much help, you need different speakers if you want a full
range small box. I'd suggest you sell them to a guitarist and then get
something full range. Or keep tham for your guitar and get a sub for other uses.

[g]

On Mar 5, 6:28 am, Patrick Turner wrote:
R wrote:

What is the best way to port a -very-smallcabinet? It is about
16"x16" across the baffle side. 14" deep. Thespeakeritself is 12".

This is intended for use with musical instruments, so absolute flat
response is not necessary. I'm primarily looking for any way to keep
thespeakerfrom sounding constricted, as it does with a closed
cabinet.

I know there are somespeakerexperts here, but if there are other
groups that deal with this type of thing, please advise.

Thanks

Having a 12"speakerin a 1.1 cu.ft box is like having an elephant in
the loungeroom;
If it ****s, you ARE in trouble.

I fear you are asking for solution which is impossible to
easily provide.

Thespeakershould be left alone. Perhaps placing a couple of
polyester wool bats inside may tame reflections from inside the box the
outside through the cone.
A port may make things sound worse.
Perhaps you should consider buying another to give a good reflex
box match, or if you want a ported box with that driver you have, then
you'd need to apply thespeakerprogram WINisd which is a free download
to find out ideal ported box design for that driver.

Of course, the driver must be tunned with proper box size and port
dimensions, if the driver is suitable for ported boxes. Adding
stuffing is most always done, otherwise it sounds like hell.
Fiberglass and foam have the most impact on internal damping.
Polyester is not as effective. Open boxes relieves the need to damp
interior surfaces.

greg