effect of back/porting, material and size on cabinet

[gwEm]

I must say i'm completely sold on 1x12s for portability.

At the moment i'm using a Marshall 1912 cabinent, which has been modified to be open back. I've run it with various speakers - for example a Celestion G12H100. Its made of 15mm ply. Though happy, recently I've been thinking that I might be able to improve on this cab, without increasing the number of speakers, but I don't really understand the effect of everything that goes into a cab. And anyway, maybe my Marshall cab isn't all that bad after all.

I understand that an open back cab is louder, but the bass response is more wooly. As I often play at home, a closed back cab is more tempting then. However, I also understand closed back 1x12s can be beamy and boxy sounding. Another option might be a closed back, but ported, cabinent - the Mesa Thiele or certain Ear Candy cabinets for example.

With the material itself, it seems like some sort of resonant material is the way to go.. pine is often suggested. But also, many high end cabs boast they are made of some sort of quality ply. Is it better to have thicker or thinner materials? Options seem to range from 12mm-18mm... would an 18mm cab sound more punchy than a 12mm cab do you think?

My Marshall 1912 seems to be of slightly below average size for a 1x12. The Orange 1x12 is a bit wider, but less high. Some 1x12s go to the full width of a head (Framus for example), and some are less wide, but much deeper. Do larger dimensions = larger sound? Presumably if its an open back cab then it makes less of a difference... but does it still make some difference?

So options I'm looking at are (in order of approximate cost):

Keep my 1912 as it
Keep my 1912 and make it closed back again
Framus 1x12 (large, open back, 17mm ply, hot100 speaker - looks alright!)
Orange 1x12 (18mm, bit larger, but closed back, V30 :( )
TT 1x12 (tom style)
Martamp 1x12 (twinfan style)
Earcandy 1x12 (philking style)
Mesa Thiele 1x12 (shaman style)

Obviously, I want to avoid spending an absolute fortune. The Mesa cabs are damn expensive!
Its a shame that nowhere really exists to A-B these options

[sambo]

I remember Nick (Dakine forum name) had a lot of praise for his dual-ported Bogner 1x12.


http://www.guitarguitar.co.uk/amplification_detail.asp?stock=06020317583229&guitars=


Not cheap but supposed to be very very good.

[PhilKing]

You know my preference, but if you are over here again soon you could A/B my Earcandy, open back 1x12, closed back 1x12 and a Matamp open back.  With a little soldering we can put the same speaker in each one (I have 2 extra Sidewinders - the Ear Candy already has one).

[gwEm]

I remember Nick (Dakine forum name) had a lot of praise for his dual-ported Bogner 1x12.


http://www.guitarguitar.co.uk/amplification_detail.asp?stock=06020317583229&guitars=


Not cheap but supposed to be very very good.

very interesting sambo.. a google search reveal that a custom audio cab is basically a clone of it.. and its available unloaded, for a reasonable price. something else to think about

[jpfamps]

Many companies claim a pine cabinet sounds better than a ply cabinet, neglecting to mention than pine is cheaper than ply wood (and easier to work).......

For durability ply is the way to go — that's why you don't see many 4 x 12 pine cabinets. Thicker ply will be stronger but heavier. I suspect there is no point using more than 15 mm for a 1 x12 cab and 12 mm will be fine. Another consideration is the baffle. Generally thinner 12 mm ply wood is used here. This is where you need to use ply for strength, pine would not last long. You have the option of fixing the baffle on all four sides, or having the baffle floating by only fixing it down two sides as in older Fender combos.

The open/closed backed ported issue is really down personal preference. Closed-back will be more directional and have better damped bass due to the cone excursion being damped by the air pressure in the cabinet. Open backed, which I prefer for clean sounds, gives a more "airy" sound, slight reduced bass due to some phase cancellation, and more spread due to the sound waves coming from the back of the cab. Regardless, a 1 x 12 cab is going to be fairly directional however it is constructed.

Porting cabs is generally used to tune the bass response and allow a flatter and more efficient bass response down to the tuned frequency, although the bass response falls off very quickly below the tuned frequency and driving speakers below the tuned frequency can cause real problems with excessive cone excursion. In fact Celestion advise against using ported cabs for this very reason.

To tune a cab accurately needs a set of parameters called Thiele/Small parameters. These are available for PA speakers, but not for guitar speakers. I suspect that most ported guitar cabs are not critically tuned and are attempting to approach a "best of both worlds" regarding open and closed backed cabs. 

[Twinfan]

...
Martamp 1x12 (twinfan style)
...

I've got a standard Matamp 1x12, with the open section in the back.  Sounds bob-on to me!

[martinw]

...
Martamp 1x12 (twinfan style)
...

I've got a standard Matamp 1x12, with the open section in the back.  Sounds bob-on to me!

The Martamp one, Matt F style, is the same but 12mm instead of 18mm ply.

[shaman]

I own 4 Thiele Boogie cabs and HAVE owned a few 4x12's...I use the Thieles because they sound HUGE and are easy on the back-my Thiele cabs use EV speakers, which are mammoth and very efficient(PA like..) I have 2 cabs with C-90's as well for a little different flavor-However, when I gig, its always 1 Thiele-does the job, and NO  ONE can belive how huge they sound(yes, its rock gigs, but I play a mean Strat ..always clean and lots of headroom available-the 200 watt ev Thiele is a perfect mate for my AMP-a mammoth Mesa Boogie MArk II C+..I have , however, used the Thiele with a DR Z Class A 38 WATT AMP and it was the tone I was looking for as well)...the bass is incredible, and the EV is very efficient and bright-that is why it works in the Thiele setup

[gwEm]

The Mesa Thiele cab sounds almost unbelieveably good from your description! If only there was some way to A-B it with the Bogner and my existing cab...  :(

[shaman]

...they are very popular in the Boogie scene because of the efficiency/power...boogies are extremely loud and benefit,IMO, from this setup-mileage may vary from amp to amp-for me, I do not like a lot of color from my speakers-I want them to be brutally honest-some don't like it because they sound"clinical"..."cold"...but, to me, it allows my other instruments in the tone chain to sound like they were designed to sound-with my BK's in the mix, it sounds anything but clinical and cold 8)

[jibidy]

I would say closed back and try to port it like those bogner cabinets. It'll give you lots off tight bass!!

[gwEm]

I would say closed back and try to port it like those bogner cabinets. It'll give you lots off tight bass!!

the thought had crossed my mind as well. i wonder if their port are finely tuned in any way, or if something approximately the same size might do as well.

thanks jpf by the way, very useful reply.

[FELINEGUITARS]

The 1912 is already ported at the front as far as I know
Hidden behind the grille cloth are two openings

[jpfamps]

The ports are tuned by varying the size of the hole and the depth of the port. The idea is that the port is tuned to the lowest bass frequency require and that the sound wave from the back of the speaker exits the port and contributes to the sound coming from the front of the speaker. Obviously the cabinet needs to be designed so that the reflected sound wave exiting the port is in phase with the sound wave coming from the front of the driver.

To calculate the tuning of the port accurately requires the Thiele-Small parameters of the speaker and some very heavy calculations. I've never seen any Thiele-Small parameters published for guitar speakers, so I expect the porting used by most manufacturers is a product of some educated guess work + trial and error.

Dr Z make a Thiele-Small ported cab tuned to 30 Hz, well below the low E on a bass guitar (!). I haven't used one of their cabs so can't comment on their sound. THD make a rear slot ported cab, which sounds great. A slotted port has less potential problems with whistling in the port. Additionally Kevin O'Connor (author of the Ultimate Tone series of books) recommends using what he calls "de-tuned" cabs, which as far as I can tell involves only putting one 12" speaker in a 2x12 cabinet so the empty hole in the baffle for the missing speaker acts like a port. Again I haven't tried this (although probably should as I could do this very easily), so can't comment on its effectiveness. I also haven't read any theory behind this, but I suspect it will be in Kevin O'Connor's book "DIY Speaker Cabinets For Musical Instrument Applications", which you can get from Bob Pearman Books for £10.50. I've got most of Kevin's other books so should get around to reading this at some stage. Bear in mind that Kevin O'Connor seems to revel in taking a contrarian view point, so whilst there is always some very useful information in his books, I would not take anything he says as gospel...........

[ToneMonkey]

I'd say make a cab with a back you can take off.  You could also make some extra backs with various ports until you get what you want....... More stuff to play with YAY  :D

This is on the long list of stuff that I really must do one day........ I was going to make a mini marshall stack using this sort of cab (and the inards of my AD30VT)