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

lukedlb

This company makes them too:
https://cutthroataudio.com/product/sfz-prism112-guitar-speaker-cabinet/

lukedlb

Diffusors mounted in front of the speaker for better sound radiation and beaming reduction.
Do any of the forum's builders employ diffusors or other techniques to avoid beaming?

lukedlb

And this company too make them and they're in europe:
http://www.tt-cabs.com/engl/?Cabs/Signature_Series/TTC_112_Raptor

These FAQs are interesting:
http://www.tt-cabs.com/engl/?Tech/FAQ

lukedlb

Here's an example of a baffle diffuser. This company also makes baffle adapter to change from 15" to 12" and so on. Interestingly, they include this information:
"The advantage of the Ice Breaker (baffle diffuser) over other diffusers is that by design, the speaker is recessed further back into the cabinet interior which adds slightly more low end to the tone projection.  This benefits the player and the audience by further balancing the overall sound."

lukedlb

I wonder if the baffle diffuser doesn't actually reduce beaming and instead reduces the harsh ice pick highs in the centre of the cone. SRV simply put some masking tape on his grill cloths to deal with this issue.

lukedlb

Ted Weber has a beam blocker:
https://www.tedweber.com/wbb12-4
and a video about sound dispersion:

lukedlb

The photo of SRV's cab with the duck tape in the aforementioned video is, I believe, a Leslie 16 with its long diagonal port. Rest assured that he did put duck tape on his cabs.

lukedlb

Here's another solution for beaming, except it's external:
https://www.hoovi.at/deeflexx/

lukedlb

And the tonebra:
http://dbinstrumentamp.com/products/tonebra-by-la-custom-electric/

lukedlb

And I've heard mention of the Jay Mitchell Donut.

hywelg

Jay Mitchells description of why beam blockers don't work is backed up by anecdotal reports that physical beam blockers create significant artefacts to the sound waves. He does explain at length why and how the foam donut  does work. It is an interesting read. 

I also find the Clearsonic screen to be effective too but some report artefacts with those too, but I do wonder if that's because some of the screens are U shape with three panels whilst what I have is modelled on what Matt Schofield regularly uses,  a 4 panel in a W shape. I can imagine reflections off a screen panel parallel with the baffle would be problematic. 

I also have a cab I built  with ports, a 4x10 closed back with 4 4" circular ports installed into the baffle. I can't confirm what it does to the sound as I don't have another without ports to compare it to but it is decent in the bass department for a 10's cab anyway, but not as good as the oversize Dumble style open back 2x12 that I have built a few of. 

pintspiller

I built a 212 using MDF. I had a strap handle initially. Side handles added soon.

Danny1969

 Jim Marshall said the size of the original 4 X 12" was based on the dimensions of the 8 x 4 sheets he could buy, as in minimum waste per sheet. No acoustic science in it, just a costing exercise . I've built a new things over the years, guitar cabs, PA cabs and wedge monitors. I've always found denser, heavier cabs to be better in the low end due to the lack of flexing ...

ICBM

Danny1969 said:

 Jim Marshall said the size of the original 4 X 12" was based on the dimensions of the 8 x 4 sheets he could buy, as in minimum waste per sheet. No acoustic science in it, just a costing exercise .

And the angled cab was designed purely because a head looked better sitting on it than a straight cab.

Danny1969 said:

I've always found denser, heavier cabs to be better in the low end due to the lack of flexing ...

Barefaced mention that too, but they say it's the rigidity that matters more than the density - it's just a coincidence that dense materials also tend to be rigid. Having heard a couple of their bass cabs I would say they're right - they achieve rigidity by complex bracing rather than density.

lukedlb

So here's a thought on 'beaming', beam blockers and the like:
Earlier I mentioned the difference Grill Cloth makes. The basket weave I had on a 4x12 was dense enough to tame the highs the amp was putting out, highs which were difficult on the ears in another cab. What if the Grill cloth did the diffracting/diffusing, or what if the grill cloth had a denser weave around the centre position? It could be as simple as two layers of grill cloth at the centre.
I planned to substitute the basketweave grill cloth with a black and tan. What if I simply put it on top? I assume if it's sufficiently stretched, there shouldn't be any flapping.

lukedlb

hywelg said:

Jay Mitchells description of why beam blockers don't work is backed up by anecdotal reports that physical beam blockers create significant artefacts to the sound waves. He does explain at length why and how the foam donut  does work. It is an interesting read. 

I also find the Clearsonic screen to be effective too but some report artefacts with those too, but I do wonder if that's because some of the screens are U shape with three panels whilst what I have is modelled on what Matt Schofield regularly uses,  a 4 panel in a W shape. I can imagine reflections off a screen panel parallel with the baffle would be problematic. 

I also have a cab I built  with ports, a 4x10 closed back with 4 4" circular ports installed into the baffle. I can't confirm what it does to the sound as I don't have another without ports to compare it to but it is decent in the bass department for a 10's cab anyway, but not as good as the oversize Dumble style open back 2x12 that I have built a few of. 

I believe this is the page @hywelg was referring to about the foam donut:
https://www.thegearpage.net/board/index.php?threads/speaker-directivity.470956/

While the Clearsonic screen is indeed interesting, I'm going to keep the thread focused on cabinet construction.

Is the Dumble 'oval' style open back very different to a traditional open back combo?

lukedlb

ICBM said:

Danny1969 said:

 Jim Marshall said the size of the original 4 X 12" was based on the dimensions of the 8 x 4 sheets he could buy, as in minimum waste per sheet. No acoustic science in it, just a costing exercise .

And the angled cab was designed purely because a head looked better sitting on it than a straight cab.

Danny1969 said:

I've always found denser, heavier cabs to be better in the low end due to the lack of flexing ...

Barefaced mention that too, but they say it's the rigidity that matters more than the density - it's just a coincidence that dense materials also tend to be rigid. Having heard a couple of their bass cabs I would say they're right - they achieve rigidity by complex bracing rather than density.

Could bracing be a way to incorporate acoustic guitar chamber construction into a speaker cabinet? The cuboid is a practical design for transportation, supporting an amp head and for resting your guitar against. I can't think of a popular alternative shape, such as a 2x12 pointing towards or away from each other (except perhaps in bass cabinets). That said, there are still many internal possibilities for transforming the way sound pushes and reflects, such as a divided 2x12 cab.

lukedlb

Who says the baffle has to be made of wood:
https://robrobinette.com/images/Guitar/AB763_Models/RR763_BLACKVIBE/IaIn_Moncrieff/Front.jpg

hywelg

lukedlb said:

Is the Dumble 'oval' style open back very different to a traditional open back combo?

I couldnt say because I've never come across a combo the size of a Dumble cab. Its 300mm deep about 800mm tall and 600 wide. It is very full sounding, lots of bass and the equal of a Marshal 4x12 for sound given the right speakers (and construction - mine are 18mm birch ply and dovetail joints)

BarefacedAudio

I'm a lot late to to this but very happy to answer specific questions about what's going on with different cab designs. Obviously you may assume that my answers are biased but I'll try not to be - Barefaced has been built on chasing truth, engineering trumps marketing, physics trumps snake oil, music trumps commerce (to the detriment of my bank balance)...