The art to speaker cabinet construction - a box or an acoustic instrument?

lukedlb

With the amount of cork sniffing that goes into tone wood, NOS pedal parts and valves, I am surprised by how little I've seen regarding speaker cab construction.
I had my 4x12 snobbery smashed by a Zilla 1x12 fat boy and a Brad Burt 2x12. I've had many 4x12s including Sound City new and vintage, Marshall new and vintage, 70s Carlsbro, Simms-Watts, not to mention the combos including twin reverb, marshall artiste, bassman, etc. Moreover, I have the good fortune of access to a good 30 Marshall 4x12 cabs from 67-75 and seen and heard first hand the differences between each.
I can't help thinking that a lot of cab construction came from convenience and economics whether by design or retail price or indeed mistaken (?) application of hifi speaker build to eliminate sound interference/degradation from the cabinet itself.
Innovation coming from Bartel amps or Bare faced audio has led me to ask if speaker cab construction has more to offer. Or has a degradation in wood selection and carpenter work damaged what was already a perfect product?

I really would like to invite some of the builders and sellers of speaker cabs on the forum to pitch in their thoughts. Most on the forum see little beyond the tolex and grill cloth.

lukedlb

Here’s an example of the work that goes into a Bartel cab:
https://secureservercdn.net/166.62.112.219/34e.08c.myftpupload.com/wp-content/uploads/2017/12/collage2-710x1024.jpg

lukedlb

Here’s barefaced audio’s explanation of their system:

https://youtu.be/jMp0GxTKSNQ

lukedlb

An interesting customisation from a recent thread from @RyanNoisyHammer ;
https://www.thefretboard.co.uk/discussion/173425/fs-marshall-4x12-2x12-1970s-pink-celestion-1970s-speakers-t1281-t1692-t1417-greenback#latest

lukedlb

Does anyone have a picture that names all the parts of a speaker cabinet? A decent nomenclature should help this thread and educate us all. Please stand up all ye carpenters. 

pintspiller

You're probably more likely to see discussion or plans for bass or PA to be honest. 

lukedlb

pintspiller said:

You're probably more likely to see discussion or plans for bass or PA to be honest. 

Would that be due to projection and definition? Or weight issues?

Does that mean reducing a guitar speaker to a convenient support system for a speaker? A convenient stand for the amp head? Are issues related to bass or P.A systems unnecessary for guitar cabs?

lukedlb

I copied this from the barefaced audio website:

There are basically two sorts - closed-back and open-backed. Open-backed because they were combos and needed to keep the valves cool and accessible for servicing, closed-back and sealed because that’s how most speakers were made in the 1960s.

How does that affect using them?

The closed-back cabs have narrowing dispersion as frequency increases (a hi-fi speaker uses smaller speakers for higher frequencies to reduce this problem). The open-backed cabs fire sound out of the back as well as the front, so although the dispersion narrows from both front and back in much the same way as the closed-back cab, the sound coming out of the back helps fill the room with mids and highs - but that sound out of the back cancels out most of the lows (due to the inverted phase as the back of the speaker pulls when the front pushes and vice versa). In other words, open-back cabs are easier to hear around the room but the lows are thinner.

How is are the Barefaced Audio guitar cabs different?

From the front it behaves much like a closed or open-backed cab. But the mids and highs coming out of the AVD at the back are amplified and dispersed around the room whilst the lows are inverted to match the lows from the front, giving lots more bottom. Basically you get twice the output of a closed back cab with an identical speaker AND even better dispersion and audibility (and far far greater output) than an open-backed cab

What is AVD?

You see it when you look at the back of the cab - it’s the Augmented Vent Diffractor. It’s a unique Patent Pending technology that we started developing back in 2013. At low frequencies it acts as a tuned vent or Helmholtz resonator, improving efficiency, power handling and output. At mid and high frequencies it acts to diffract, disperse and couple the sound with the room for improved audibility and output especially in rooms with poor acoustics.

What is the Lo Cut filter for?

The increased low frequency output from the AVD may be too much for some guitarists’ tastes - so you can flick this switch and remove lows at the cab. Doing so not only changes the bass response but also increases the power handling of the cab, lowers the distortion due to motor excursion and reduces the load on your amp’s output stage. This can give you two different sweet-spots of optimum speaker overdrive or break-up and two different sweet-spots of power valve overdrive. If your sound is perfect in rehearsal but too dirty at a louder gig then engaging the Lo Cut filer will clean it up.

ICBM

In my opinion they are an acoustic instrument - part of the chain that creates the sound you want to hear - a sound producer not a sound reproducer. There are definitely ways of applying science to that, although it has to be said that most traditional designs that sound good are happy accidents.

The most important thing to realise is that although the science can be applied to both and you can use the same physics to explain what is happening, the *goal* is totally different - in fact almost the exact opposite - from what it is for hi-fi or monitor-type cabinets, where you are trying to *remove* colouration.

Many people try to apply the 'rules' for one to the other, and then they're almost always wrong. A basic example is that MDF is a very good material for hi-fi or monitor speakers because it's acoustically 'dead' compared to ply. That - for exactly the same reason, but the opposite goal - makes it a bad choice for a guitar or bass cab.

In fact it's a fairly good rule of thumb that anything you do which makes the amp and speaker system better for hi-fi makes it worse for guitar, and vice versa. Bass and PA are somewhere in the middle, with bass being closer to guitar and PA being closer to hi-fi.

Barefaced Audio understand this very well - they know the physics behind what they're doing, but they're not making hi-fi cabinets.

lukedlb

Taking further @ICBM 's 'happy accidents' and 'applied science' for the creation of an acoustic instrument as the final link in the chain of a traditional electric guitarist, what aspects contribute to its sound? I'll make a start on the nomenclature:

Baffle
Back panel
Finger joint
Grill cloth (yes, this does make a difference - think basketweave vs silver thread cloth)
Tolex (to tolex or not to tolex)
Handle (leather as opposed to metal inserts like a Marshall 4x12)

lukedlb

I wrote traditional electric guitarist as opposed to the direct to P.A approach.

pintspiller

@lukedlb the bass/PA thing is to do with porting and whatnot. The people who are really into this sort of thing share this stuff openly.

I'm sure there are schools of thought on guitar cabs too. Aren't there people who swear by certain Mesa cabs due to size/design over other Mesa cabs with same speakers?

lukedlb

Baffle

Back/rear panel

Finger joint

Grill cloth

Tolex

Handle

open/closed back

framing

top, bottom and sides

Removeable Grill frame

Corner protectors

cabinet shell

Front / rear port

Vertical or Horizontal

lukedlb

Does the internal volume of the cabinet have to be proportionate to the speaker? 10", 12", 15"? Number of speakers? Output?

I don't mean the obvious that the cab has to be large enough to house a speaker/s; rather there is something about the cab's internal volume that supports the speaker. For example, my Zilla Fatboy, a large cab for a 1x12 has much more strength than I expected. If Zilla made a heavily overweight Fatboy, would it have excessive bass? What would be the perfect balance?

lukedlb

As for the choice of wood: Soft wood, Hard wood, Engineered wood (MDF, ply, composite).

Most of my speakers are built from ply. What type of wood is used and what makes them preferable?

For example, I selected okume for a baffle. It's expensive. Is that why I've never seen a whole cab made from okume?

ICBM

lukedlb said:

Does the internal volume of the cabinet have to be proportionate to the speaker? 10", 12", 15"? Number of speakers? Output?

I don't mean the obvious that the cab has to be large enough to house a speaker/s; rather there is something about the cab's internal volume that supports the speaker. For example, my Zilla Fatboy, a large cab for a 1x12 has much more strength than I expected. If Zilla made a heavily overweight Fatboy, would it have excessive bass? What would be the perfect balance?

It is generally true that a larger cab gives more bottom-end, but without doing a huge amount of research so you can work out the formulae it's going to be just a matter of trial and error.

lukedlb

ICBM said:

lukedlb said:

Does the internal volume of the cabinet have to be proportionate to the speaker? 10", 12", 15"? Number of speakers? Output?

I don't mean the obvious that the cab has to be large enough to house a speaker/s; rather there is something about the cab's internal volume that supports the speaker. For example, my Zilla Fatboy, a large cab for a 1x12 has much more strength than I expected. If Zilla made a heavily overweight Fatboy, would it have excessive bass? What would be the perfect balance?

It is generally true that a larger cab gives more bottom-end, but without doing a huge amount of research so you can work out the formulae it's going to be just a matter of trial and error.

Science must have the solution. Saying that, I am playing my hammond clone through Logitech PC speakers and it sounds fantastic. The woofer is the size of a shoe box and the pair of tweeters no bigger than a shoe. 

guitargeek62

I don’t think you’re wrong, I just feel you’re overthinking it.

lukedlb

guitargeek62 said:

I don’t think you’re wrong, I just feel you’re overthinking it.

well, yes, that's what my zilla proved to me. I've opened it up: there's nothing particularly special inside and it does the job incredibly well. However, I looked at the exceptional carpentry on my Bob Burt, the thinness of the wood on the Artiste cabs, the carpentry design that went into my 68 marshall 4x12, and there's no doubting how much better they are at projecting the sound.
So what are the elements that make those cabs superior? The wood? The carpentry skill? Because it's time for a change with speaker cab production in terms of weight and projection shown in the barefaced cabs or the Bartel.

LastMantra

This is all very interesting. I was trying a few different valves in my amp the other night and decided that I might prefer leaving the (normally closed) back off. Going to try it for a bit anyway. 

lukedlb

LastMantra said:

This is all very interesting. I was trying a few different valves in my amp the other night and decided that I might prefer leaving the (normally closed) back off. Going to try it for a bit anyway. 

Exactly: ports! I have a rear port on the Zilla. A front port on the Sound City. What about side ports? Could eliminating the side handles actually improve sound dispersion instead of the beaming phenomena?