Requesting help with Single driver speakers

[Type 1]

KGreetings!

I’ve been playing with single driver speakers recently.

Probably some of you have been down similar paths so I’m hoping to get some insight.

I’ve settled on a 8 inch driver from SB Acoustics.. ( SB20FRPC30-8 )

Because I have a large room and was worried that a smaller driver might struggle.

I’m following the basic outline that many people use… a folded Voigt Pipe.

I’m on my second version which is very similar in dimensions to the first but built from 28.5mm hardwood ply, instead of 18mm hardwood plywood.

Evidently the cabinet vibration on the first one was degrading the sound.. I could feel the box vibrating on all sides, especially on the top.

So the second one sounds much more direct and punchy ( the first was a warm and fluffy).

But the top of the box still has some vibration on the outside and the knock test seems louder than the rest of the box.

So I’m on to version 3.

The goal is to have a rounded inside surface inside the top of the box… 

To me, It seems that the fold is the weakness in the design.

So my question to those that know is … on the normal design, the sloping mid panel ends half way up the driver ( see drawing.. red lines)

But with a the inside top piece following a radius the inside sloping panel must end pretty much equal to the top of the driver. Do you see a problem? In theory ending the sloping panel 1/2 way up the driver mimics the straight pipe.

Also the baffle at the front might be slightly higher than the original design…. Would that be a problem? ( See drawing.. green lines)

I can curve it back so the flat surface is shorter.

Thanks for reading this far! If you know or have tried these ideas before, please point me in the right direction!

Thanks, John D

 

 

 

 

 

[Deepthought]

This might be a good resource: https://www.diyaudio.com/community/threads/sb-acoustics-sb20frpc30-8-8-fullrange-cheap-monster-ii.385062/page-2

 

Edited September 10 by Deepthought

[Deepthought]

I would suggest having a curve or chamfer on each side of the front of the baffle will smooth sound. A baffle step response adjustment would also help if the driver sounds too bright. I'd look at putting multiple cross braces down middle of the larger rear pipe is cabinet flexing is an issue. 

Edited September 10 by Deepthought

[LogicprObe]

 

A lot of people have tried most things before.........but you are the listener.

You have to build it and decide if it's any good or not..............and keep doing it until you are satisfied.

(else buy someone else's experiment where they say they have 'cracked it')

OR!...........try some KEF LS50's and see/hear what you reckon?

[Type 1]

Thanks Gentlemen!

[Powerglide]

These work well with 8’’ drivers, imaging is super deep.

 

https://stereonomono.blogspot.com/2015/02/lowther-acousta-1960.html

 

Differs from yours with an extra fold in the horn, and someone else has put in the R&D 

[Type 1]

Thanks for the link powerglide!

As the SB driver has reasonable efficiency 92+ db and I’m using a powerful amp, I didn’t see the need to go to a backloaded horn.

But might be a good choice for some set ups.

[Type 1]

Sooo, maybe I haven’t explained myself very well..

I have access to a CNC machine and cheap plywood, so I’m open to options.  I’m planning this time to use layers of plywood to make up the body of the box and a piece of plywood on the sides, 25mm plus.

     So I’m able to curve the front surface ( baffle ) slightly in the hope of better sound. ( see drawing ).

What do you think… are there benefits of having a curved front surface?

Thanks…..

[BRS]

Can't say if seen this but if it's not costing you much to do then why not give it go and share your findings.