Cabinet for Celestion 1x12 V Type

[marcelomd]

Hi,
Sorry if this isn't the right place to post this question.

I recently got a great deal on a Celestion V Type 12". Does anyone have plans for a good sounding cabinet I can build to put it?

For reference I like the Mesa Boogie 1x12 widebody closed back.

I think I can work out the math to design something, but I have no idea about how the variables interact to make a cabinet sound good, so I would like to start with something proven.

[anotherjim]

Weight    34 Lbs.
Height    16 1/2"
Width    22 3/4"
Depth    12 3/4"

From the on-line catalogue.
No fancy port/opening complication.
It's a box.
Build it!

[j_flanders]

DIY is fun, and I love woodworking, but sometimes it's just cheaper and easier to buy something ready made.
I had a couple of 8", 10" and 12" speakers and was considering building some cabs for them.
But if you have to buy wood, tolex, grill cloth, corners, handle, feet, piping, glue, jack it's gonna cost more than these for example:

(sell the included speaker to save even more money):

60 euros for a great looking 1x12 (76 euros - 15 euros for the speaker)
https://www.thomann.de/gb/kustom_defender_112_cab.htm

Same thing, different design:
https://www.thomann.de/gb/harley_benton_g112.htm

Ugly but it's practically free
129 euros for a 1x12 including a Celestion V30  that costs 129 euros without the cab...
https://www.thomann.de/gb/harley_benton_g112_vintage.htm

Same thing, same price, equally ugly
https://www.musicstore.de/nl_BE/EUR/Fame-GN112-Vintage-30-Cabinet-/art-GIT0023239-000

1x10 cab for 60 euros (79 euros - 19euros for the included Celestion speaker)
https://www.gear4music.be/nl/Gitaar-and-Basgitaar/SubZero-G110-1-x-10-Celestion-Speaker-Cab/NE3

Eventually I bought the Kustom, the Subzero and built this 1x8 cab myself with leftover materials (old pieces of ply wood, old trousers for 'tolex' and an old mini skirt from my girlfriend for grillcloth, electric wiring for piping, toilet rubbers for feet, still no handle...)



A little more on topic: guitar cab design is nothing like designing HiFi speakers/cab. Pretty much everything goes. The purpose of the cab is little more than housing the speaker and holding it vertically...

[marcelomd]

Thanks, guys.

Weight    34 Lbs.
Height    16 1/2"
Width    22 3/4"
Depth    12 3/4"

From the on-line catalogue.
No fancy port/opening complication.
It's a box.
Build it!

Found this picture without the front cover:

Does port shape make a difference (I know size does)? I also cannot find if they use some acoustic padding inside.
I may have to find one to take a look inside.

DIY is fun, and I love woodworking, but sometimes it's just cheaper and easier to buy something ready made.
I had a couple of 8", 10" and 12" speakers and was considering building some cabs for them.
But if you have to buy wood, tolex, grill cloth, corners, handle, feet, piping, glue, jack it's gonna cost more than these for example:
...

Here in Brazil, the cheapest used no name cab on "ebay" is +- 390 BRL. For reference, a Marshall MX112 is 2200+. For 450 I can order a custom one complete with tolex.

Eventually I bought the Kustom, the Subzero and built this 1x8 cab myself with leftover materials (old pieces of ply wood, old trousers for 'tolex' and an old mini skirt from my girlfriend for grillcloth, electric wiring for piping, toilet rubbers for feet, still no handle...)

It turned out quite nice, actually. the wife was talking about donating some clothes... hmmm

[geertjacobs]

http://ax84.com/corecabinets.html
http://ax84.com/static/corecabinets/AX84_1x12_Cab_09.08.03.pdf

The AX84 site has a nice design for 1x12.
You can get two of these out of a single multiply board.
I just completed one (from 15mm multiply all around) and put a secondhand really cheap Celestion Seventy 80 in.
Sounds nice.

[marcelomd]

Eventually I bought the Kustom, the Subzero and built this 1x8 cab myself with leftover materials (old pieces of ply wood, old trousers for 'tolex' and an old mini skirt from my girlfriend for grillcloth, electric wiring for piping, toilet rubbers for feet, still no handle...)

Looks like I'll be finishing the amp head before the cabinet. How did you do the corners on that box? Cut and glue or did you sew them?

Thanks!

[j_flanders]

How did you do the corners on that box? Cut and glue or did you sew them?

Cut and glued. Once cut, the rather thin fabric frayed terribly. I had to be really careful.

[Rob Strand]

Found this picture without the front cover:

Does port shape make a difference (I know size does)? I also cannot find if they use some acoustic padding inside.
I may have to find one to take a look inside.

Copying a ported enclosure and putting a different speaker in the box is very hit and miss, and probably won't achieve your goal.  The response of ported enclosures depends very much on the speaker parameters (the Thiele-Small parameters), the box volume, the port tuning frequency and the amount of stuffing.

For low frequencies the port shape has virtually no effect provided the port tuning frequency is the same.
As for high frequencies, there maybe some subtle acoustic reason for tapering the port; but I'd have my doubts how strong an effect that would be.

For guita,r the size of the front panel does have an effect on the sound.  So if you like the sound of that enclosure maybe make something which has similar frontal dimensions.

[edvard]

I may be wrong, but I've heard from more than one source that guitar cabs as we know them were not originally built with Thiele-Small or any other parameters in mind, just made big enough to fit the speakers and match more-or-less the width of the head, so I wouldn't worry too much about "working out the math".  In fact, copying another cab is probably the easiest way to do it from scratch, so go for it.  But if you really want to DIY it you got a couple of options...

For the absolute cheapest option, buy a Bee box kit and an appropriate-sized board for the speaker baffle:

If you really want to work out a design, here's a good way to ball-park an appropriate size sealed cab that I pulled from another forum:

Multiply nominal (frame) diameter by 1.1. Cube that number. That's a happy sealed-box volume for a 1% efficient driver. Double that volume will also be fine.

So basically, take 12" x 1.1 and cube it; that gives you 2299.968 cubic inches but you can round that up to 2300 (I won't tell anybody).  Figure how wide and tall you want the front, and divide the volume by those dimensions multiplied, to get the depth. 
For example: let's say you'd like it 18 inches wide, and leave at least one inch of room on any given side for mounting comfortably, so 14" (12 plus 1 inch top and bottom) by 18".  Divide 2300 by 252 (that is, 14x18) and that leaves you with the depth, 9.12369blahblah; just round down to 9.
Remember, the larger the box, the more bass response, and ports will add bass as well.  Looks like that Mesa Boogie cab has a volume of 4786 cubic inches, which is roughly double the 2300 figure, so it'll work fine according to the ball-park wisdom I quoted.

If you're going for an open back cab, throw all that out and just mount it on whatever size will fit.  Remember, you're building a guitar cab, not a hi-fi box, so don't sweat it too much.

(Edited to add "x 1.1" to the example as pointed out by PRR below)

[PRR]

> take 12" and cube it; that gives you 2299

You left out the "1.1".

Also: this is for "sealed" boxes. Classic g-amps are open-back. Then you want as much front-area as you can stand, and still have enough depth so it won't fall over.

[Rob Strand]

I may be wrong, but I've heard from more than one source that guitar cabs as we know them were not originally built with Thiele-Small or any other parameters in mind, just made big enough to fit the speakers and match more-or-less the width of the head,

That's what was done.   Sealed boxes are somewhat more forgiving than vented boxes.   Also a good deal of guitar speakers have similar-ish cone masses and coil designs.

Designs using Thiele-Small are about the low frequencies.   Low frequencies play a part in the tone but it's not the only part.   The baffle size affects the mids.   Stuffing affects the mids.   Highs comes from the speaker itself.

[edvard]

> take 12" and cube it; that gives you 2299

You left out the "1.1".

Also: this is for "sealed" boxes. Classic g-amps are open-back. Then you want as much front-area as you can stand, and still have enough depth so it won't fall over.

Crap, I did leave that out, didn't I?  That's OK though, because (12*1.1)^3 is actually 2299.968 so the final numbers are good. Hopefully I can edit it for posterity...
I did mention it was for sealed boxes, so I got that going for me... 

I may be wrong, but I've heard from more than one source that guitar cabs as we know them were not originally built with Thiele-Small or any other parameters in mind, just made big enough to fit the speakers and match more-or-less the width of the head,

That's what was done.   Sealed boxes are somewhat more forgiving than vented boxes.   Also a good deal of guitar speakers have similar-ish cone masses and coil designs.

Designs using Thiele-Small are about the low frequencies.   Low frequencies play a part in the tone but it's not the only part.   The baffle size affects the mids.   Stuffing affects the mids.   Highs comes from the speaker itself.

I always thought sealed boxes made for a "tighter" bass sound generally, and that's why many bass cabs are ported.  I didn't know stuffing affected mids.  Good to know. 

[marcelomd]

From everything I read so far, it seems that open backs are pretty much just something to keep the speaker upright. So really hard to screw up.

My friend has that Mesa wide body. I'll try to make some measurements, see if there is something special about that port. If it all fails, I'll close the port and just leave the back open. His has a Celestion Greenback, which is more or less similar to my V Type.


Bass cabinets look a lot more complicated. Last week I was watching some videos from the guy from Barefaced Audio. He seems like he knows his stuff. He goes on and on for hours talking about the trade offs for a good bass cabinet. Math and graphs and all that.

Then he gets to the conclusion that a simple ported design is the best...

[j_flanders]

The Celestion website has a page on this subject:
https://celestion.com/speakerworld/guitartech/1/194/Thinking_of_using_Thiele_Small_parameters_to_design_a_guitar_speaker_cab?_Think_again.../

It specifically warns against using a ported design:

Vented / tuned / ported boxes are not recommended for lead guitar, as they can damage guitar speakers.
Guitar speakers are not recommended for use in ported cabinets (as the increase in cone excursion below the tuning frequency can cause the thin paper edge of the cone to tear).

Another:
https://celestion.com/speakerworld/guitartech/9/7/Build_Your_Own_Guitar_Cab/

As for open back, Teemuk's post covers most of it (of the little there is to it).
https://www.thegearpage.net/board/index.php?posts/20896954/
The text is in French but the little drawing explain it all (the difference between wider and deeper).
One of the things he omits is that when the back opening is too small it becomes a ported/vented design.

[Rob Strand]

It specifically warns against using a ported design:

That's been around a while and it's pretty much the only place it appears in the literature.  The problem is it is never explained why.  It's also not true in general.

Here's a comparison of displacement curves for for the same speaker in different enclosures.

QTS is one of the Thiele-Small speaker parameters.   It is sometime published and sometimes not.   It can be measured with crude equipment.   Low QTS speakers are used in HiFi and for Bass.  However they are also used for guitars (eg. EV 12").   The typical light cone guitar speakers have high-ish QTS's.

This case is for low a QTS speaker.


This case is for high a QTS speaker.


The main message is:
- At low frequencies the displacement of a vented enclosure isn't *that much* different to an open back enclosure.
- The case for high Qts is different to low Qts.   You shouldn't generalized you really need to know what Qts is.
- If you see a peak in the displacement it doesn't mean it's a problem.  For guitar a peak in the displacement at 20Hz is far less risky than one at 80Hz.

More general is:
- In a broad sense sealed enclosures win on displacement, but,
- The vented enclosure has a region where the displacement is much lower than a sealed enclosure.  If you tune the port to around the same frequency as the lower bass strings then you *can* get lower displacement with a vented enclosure.
- The high-pass filtering in an amplifier helps remove low frequencies and can reduce displacement.   This is done in many bass amplifiers.

So you can see the story depends on the specifics of the speaker,  the specifics of the cabinet, and the specifics of the signal you are putting in (in terms of where the problem frequencies are).

Just be be clear, the thing to look at is the different shapes of the curves not the frequencies or the displacement values.  Different speakers will slide the curves left and right.  The actual displacement values depend on the speaker and the amount of power driven into the speaker - don't go comparing the 2mm on the low Qts curves with the 0.7mm on the high Qts curves, they are different scenarios altogether.

[anotherjim]

A glance at some of old Vox cabs from the 1960s shows that, traditionally, being strong enough and matching and supporting the amp were major design aims.
https://www.voxac100.org.uk/index_ac100_cabs.htm
Bass cab ports? What's a port? In small venues (back room of a British pub) a ported bass cab is terribly boomy if the amp only has rudimentary EQ.
Horn tweeters in a guitar cab? 
The success of Marshall sealed 4x12 cabs meant that in the UK, generally, open back was only used in combo amps.

[marcelomd]

The Celestion website has a page on this subject:
https://celestion.com/speakerworld/guitartech/1/194/Thinking_of_using_Thiele_Small_parameters_to_design_a_guitar_speaker_cab?_Think_again.../

It specifically warns against using a ported design:

Vented / tuned / ported boxes are not recommended for lead guitar, as they can damage guitar speakers.
Guitar speakers are not recommended for use in ported cabinets (as the increase in cone excursion below the tuning frequency can cause the thin paper edge of the cone to tear).

Another:
https://celestion.com/speakerworld/guitartech/9/7/Build_Your_Own_Guitar_Cab/

As for open back, Teemuk's post covers most of it (of the little there is to it).
https://www.thegearpage.net/board/index.php?posts/20896954/
The text is in French but the little drawing explain it all (the difference between wider and deeper).
One of the things he omits is that when the back opening is too small it becomes a ported/vented design.

Out of curiosity I sent an email to Celestion about the "no guitar speakers on ported cabs" policy.

I wouldn't ever recommend putting a paper edged guitar speaker in a ported cabinet. There's too much risk of damaging the speaker due to over-excursion at the low end

Yet, there are Mesas, Marshalls and others doing exactly that. I guess this is just a legal safeguard.

[Rob Strand]

Yet, there are Mesas, Marshalls and others doing exactly that. I guess this is just a legal safeguard.

The speaker on the Mesa speaker has a beefy magnet and is quite efficient.  My guess is it has a lowish QTS making it useable in a vented enclosure.   The problem with ported speakers is final result depends on the specifics of the speaker.  You can't just put a different speaker into the same enclosure and expect the same results.  Tweaking the box volume and port tuning for a different speaker is unlikely to mimic a different design.

You would be better off using the same dimensions for the front panel as the Mesa and building a sealed enclosure.   Tweak the stuffing to suit your taste.   

Here's my estimates of the internal volume. 
The published heights include about 3/4" for the rubber feet.

mesa wide body – closed         
         
   outside w/feet [in]   internal est [in]   
H   16.5                          14.25   
W   22.5                           21   
D   11.25                        9   
         
   Internal Volume   
      2693   cu in
      1.56   cu ft
      44.1   litres
         
mesa wide body – thiele (w/port)         
         
   outside w/feet [in]   internal est [in]   
H   15.75                  13.5   
W   18.75                  17.25   
D   12.75                  10.5   
         
   Internal Volume   
      2445   cu in
      1.42   cu ft
      40.0   litres

If you use a different speaker the upper mids and highs are going to be different and that's a major difference in sound from the outset!

If you believe the reported dimension/specs, the ported enclosure is smaller but 2lbs heavier than the closed enclosure.  More often ported enclosures are larger than the sealed enclosures.   Maybe you can check the dimensions on your friend's box.

[Rob Strand]

Something that occurred to me about the ambiguous dimensions is there were Mesa wide and narrow heads at some point.   I think Mesa speakers are dimensioned to fit under these heads.   The wide heads were about 22.5" wide and the narrow ones were 18.75".  So that makes me think a width of 18.75" doesn't corresponds to a "wide" configuration.

Oh, the other thing is Mesa seems to have started using vented enclosures back in the days of EV12's.   These are typical low Qts drivers and will not suffer from damage in a vented enclosure.   From what I can see the Celestion C90 was built replace the EV12.

Maybe someone who knows their Mesa stuff can fill in the finer points.