Baffles compensés RJ or Carlsson RJ in my living room

[vincula]

Hi there guys,

I decided to enter 2016 building a new pair of boxes. These are LITERALLY TWO BOXES, a couple of "West Westinghouse washing machines from the 50's-boxes". I have always wanted to try a Carlsson RJ enclosure:

Supravox Kits - DIY

I went for a couple of slightly modified 8" Monacor SP 205 de 8" drivers to keep budget sensible, though swapping drivers is a piece of cake, as you can see.

An externally hosted image should be here but it was not working when we last tested it.

These drivers are fairly inexpensive, but they sound pretty good hooked to my Audio Note P2 valve amplifier. Don't get me wrong, they are no Supravox 215 Signature and still... you'd be baffled by the sound. I have used acoustic egg-shaped foam (rear and side walls only) and 0.5 kg pure sheep wool per box to damp the enclosure. That's it. I chose 15 mm plywood for the box.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

They're in a raw version now. I use a couple of chair as improvised stands.

An externally hosted image should be here but it was not working when we last tested it.

They simply sound stunning. I suspected that removable front baffle had some real potential. They sound totally free from box-sound, very balanced in mids and highs (surprisingly so), good bass output and very very fast and life-like. I really love them. Just don't ask the missus. Well, she already thinks I'm nuts. I do admit she's absolutely right.

These are staying though. They are good. Very very good. If you're considering building a pair, just go for it!

Regards,

Vincula

 

[GM]

Greets!

Very nice and very similar to this old RS driver that was 'dirt' cheap and performed way better than it should have, especially once the $0.98 tweak was applied to the whizzer:
Radio Shack 40-1271 Fullrange Speaker Driver
https://web.archive.org/web/20020213114931/http://www.mindspring.com/~darmah/lowther/mods.htm

Which cab size did you build? These specs indicate the larger one: Monacor Breitbandlautsprecher SP-205/8

Any idea what it is tuned to? ~66 Hz seems the best overall.

Regardless, thanks for sharing! Wish these were available over here at that price.

GM

 

[xrk971]

Can you draw a sketch of the driver and box layout? The vent goes past the backside of the cone out through the thin gap between the front baffle and the main rear enclosure front wall? A normal RJ that I am used to seeing has the vent going out through a thin gap and past the front surface of the cone then out coaxilaly with the direct radiation from the front of the cone. Interesting to use the rear side of the cone.

 

[GM]

From post #1, then click on 'download': Supravox Kits - DIY
http://www.supravox.fr/kits/bafflescompenses.pdf

GM

 

[richardthusted]

Hello. You can buy them here: Alto-Højtaler | Færdigsyede designs og løse enheder. It is in Danish, but send us an email.

greeting Richardt.

 

[xrk971]

Thanks GM.

 

[vincula]

It's really a simple, cheap and rewarding project.

I've used this to damp the enclosure:

An externally hosted image should be here but it was not working when we last tested it.

And these are the drivers they sport right now:

ALTO SP 205 | Alto-Højtaler

Future -and my wallet- will tell whether I jump over to a pair of Supravox 215 rtf or not.

Regards,

Vincula

 

[xrk971]

It is interesting and I will have to model this in Akabak and try with other drivers. Maybe even make something smaller using a Dayton RS100 or an FF105WK.

 

[GM]

Yeah, these were something I'd plan to try out of curiosity if I ever get around to learning AkAbak as I couldn't figure out any sort of viable vent design routine from the one's I long ago built/tuned empirically/measured.

I queried the inventor's son for some hints, if not the full formula, when he was on the basslist, but he politely declined.

GM

 

[EddieT]

The socket wrench in the whizzer cone is interesting.

 

[Squeak]

Weird as hell. So it's a small open baffle lifted a few centimetres off a hole in a stuffed box?
Have you tested how much difference the box actually makes?
Maybe the RJ construction would make more sense?
I'd had a pair of these drivers kicking around looking for a good cap for some time now. They're dirt cheap unmodded but has a good rep. Very very high Qts though. Allegedly above 2.

Edit: well, it seems like an inside out RJ enclosure, without the HF slot loading in front of the driver. It could be said to have it on the back. It seems very inefficient though.

 

[EddieT]

Caisson means large box, but the RJ apparently does not refer to R-J as we know it.

 

[freddi]

i think its related though the use of a gapped baffle to form the vent. In a traditional R-J the sub-baffle is inside forming a type of series BP.

perhaps the idea predates the R-J ?

on page 209 of G.A. Briggs "LOUDSPEAKERS" 5TH eDITION, Fig. 18/22 , there's a one cubic foot R-J type bookshelf cabinet for 8 inch speakers using a simple inner gapped baffle and no constriction of the aperture. Briggs also gave examples of the technique with a rectangular slot aperture in front of the cone.

8 inch R-J cabinet inner baffle

"second" R-J aperture - a rare Slimline 12" R-J - the first aperture was a lopsided parallelogram - then came the "lemon"

15" RJ cabinet's lemon aperture

RJ-vented 6.2 cubic foot reflex

R-J ad

 

[vincula]

It´s easy to find inspiration surfin' around. I know in the end it's just a box -aren't they all?- but this implementation seems quite appealing to me:

An externally hosted image should be here but it was not working when we last tested it.

I always fllow the crowded Crowe very closely too:

Joseph Crowe's DIY Speaker Building Blog: Summer Rain -- Part One -- Initial Design Stage -- Altec VOT Inspiration

An externally hosted image should be here but it was not working when we last tested it.

Regards,

Vincula

 

[slmnklyc]

supravox baffles compenses RJ math equeations

Yeah, these were something I'd plan to try out of curiosity if I ever get around to learning AkAbak as I couldn't figure out any sort of viable vent design routine from the one's I long ago built/tuned empirically/measured.

I queried the inventor's son for some hints, if not the full formula, when he was on the basslist, but he politely declined.

GM

Hi.
I found a little Math on a page(end of the page) about this Design:
5.6 Comment calculer une enceinte bass-reflex? - francis.audio
Do you think that these Math can be useful to build these cabinets?

 

[freddi]

my 4-18" RJ style (non restrictive aperture) boxes went pretty much by alignment, and like a lot of shelf vent boxes, tuned maybe 10-15% below target. It would be easy to provide for some tuning. It seems like a good method. The only fault I have for the original R-J would be too thin panels.

I also have the "Eliptoflex" variant sold by Lafayette Radio

 

[slmnklyc]

It was a little diffucult to think,but I think I understand The concept:
It is basically "disc shaped vent"!!
I will try some box dimensions(in The equations) to Reach to desired tuning frequency,I think that's it!!

 

[slmnklyc]

Cab acoustic compliance of the enclosure = Vb / (ro * c ^ 2 * Se ^ 2)
Does The "c" represent The speed of Sound?

 

[slmnklyc]

What are The units of The Cab and Ma in this?:
the tuning frequency Fb of a bass reflex is defined by:
Fb = 1 / (2 * pi) * 1 / root (Cab * Ma)

When I assume c is speed of Sound,
I tried to calculate The Fb For 215 baffle compenses enclosure and I found:
Fb= 1,668.439.633.004.973
And Unit is sqrt(second/meter)..

Is this Unit meaningful??

 

[GM]

Hi.
I found a little Math on a page(end of the page) about this Design:
5.6 Comment calculer une enceinte bass-reflex? - francis.audio
Do you think that these Math can be useful to build these cabinets?

Looks like it; thanks, but without Excel installed and the time to program it, no clue if it's [accurate] enough. Maybe someone will give it a try.

The one with the driver/baffle in front can be simmed as a slot vent reflex and after a bit of thought, the other is basically a 6th order bandpass [BP6], so any program that can do these should be able to at least get us close enough to figure out what sort of end correction is 'good enough':

GM