Fern roby raven box vs 1 : 1.618 ratios

[norman bates]

Just spit ballin here..

I'm thinking w8-2145 in either fern roby raven sized box (19.25" wide by 24.5" tall, minus stand), or similar without stand 19" wide by 29" tall.
When the raven is on its stand, it is darn near 29" tall.

Definitely need 5mH baffle srep inductor, maybe more.

My similar 1:1.618 (w8-2145) needed big bass boost for my ears when off the ground, even some when on the floor.

Not much bass beyond 7' away in my big room.

Do you think it helps to offset the driver also (vertically anyway) ?


Here are some links to the raven (using seas exotic f8).
The Ravens |
Fern & Roby
Fern & Roby Raven Loudspeakers | Review | Part-Time Audiophile
Fern & Roby Send A Raven - AXPONA 2019 | AudioHead
CAF 2018: Fern & Roby – Twittering Machines
CAF 2018: Fern & Roby – Twittering Machines
https://forum.audiogon.com/discussi...good-the-bad-and-the-ugly/post?postid=1829142

And a review of seas f8 from back in 2011
https://www.tnt-audio.com/casse/seas_exotic_e.html

My wife agrees with me, the walnut sides are gorgeous !!!!!!!!!!

 

[GM]

Not sure what the first question is, but 19 x 29 is well within the acceptable room ratios and 29" is too short for 1/4 WL vent damping, though in theory the optimal driver offset of typical speakers is L*0.42, but IME, minimal wall damping on the top, one side and back negates it. Better to offset the driver in both dimensions to average out driver/baffle reflections.

GM

 

[planet10]

Norman,

Don’t know about the rest, but ref the question raised by the title…

The only thing “magic” about the Golden Ratio is that it is an irrational number. Box dimensions (internal) are ideally a set of ratios that have irrational numbers in them. Note: do not use root(2) twice as that will give a 2:1 ratio on one set of sides. You do not want ratios that are integers.

dave

 

[norman bates]

Ty.

I've looked a little on ratios.

Saw 1 : 1.31 : 1.62 would work also.

 

[GM]

Note: do not use root(2) twice as that will give a 2:1 ratio on one set of sides. You do not want ratios that are integers.

Not sure I follow, I mean if you can find on-line graph of acceptable room ratios it shows the mean is 1.0:1.5:2.0.

GM

 

[planet10]

That it is the mean does not mean it is a useful set of ratios.

dave

 

[GM]

Hmm, according to my chart it does.

Regardless, still wondering if my commonly used [and looked 'right' acoustically in MJK's program] 0.618:1:x.618 to increase height: x = 2, 3, etc., is technically wrong.

GM

 

[planet10]

Anytime you have integer multiple ratios you have the potential for resonances to stack up on one another, instead of spreading them out evenly.

dave

 

[GM]

OK, but not seeing it with the bolt ratio, at least not at any size we would normally build, so see no reason why we shouldn't use it: amroc - THE Room Mode Calculator

GM

 

[Richard Ellis]

Cube root of Two....0.7937 : 1 : 1.2599

With the drivers on the 0.7937 wall, the drivers center-line 0.707 on the vertical axis, offset to the horizontal 0.618

Really makes for an odd looking, & nebulously "correct", thoughtful arrangement.

-----------------------------------------------------------------------Rick......

 

[planet10]

0.7937 : 1 : 1.2599 0.7937 wall=baffle, driver center 0.707up, offset to the side 0.618

Not so weird looking IMO

dave

 

[Richard Ellis]

After seeing an Infinity Qb driver arrangement...just what is it about arrangements do they know that I don't?...Somehow, this just looks, "Right", I can't put my finger on it!
This no doubt would all fall down as it were, if it was anything but a point-source full-ranger...now, if I can extend this to an Audio Nirvana 15 classic at 375 liters...
Using multiple drivers would introduce weighting of one driver over another...etc etc...what a mess that would be, stay with a FR!

-----------------------------------------------------------------------Rick.....

 

[norman bates]

Rankstranger made a clone of the raven but with seas fa22rcz.

 

[GM]

After seeing an Infinity Qb driver arrangement...just what is it about arrangements do they know that I don't?...Somehow, this just looks, "Right", I can't put my finger on it!

Hmm, apparently nothing if you at least 'sense' it.

The woofer is at a max baffle/box fundamental [max gain], the tweeter is apparently at its max external eigenmodes null in both planes [adding a virtual acoustic damping 'chamber'], so with a 'FR' driver it needs to be centered on a sufficiently large baffle of whatever shape to get the desired polar response with the rear in an end loaded TL/whatever.

Already looking forward to your solution, hopefully with comparisons to typical speaker box configurations.

GM

 

[Richard Ellis]

Looking at the likes of the venerable L-100 & its studio counterpart, there seems to be no rhyme or reason on driver placement. This random driver placements can be seen in the seventies series of loudspeakers. Newer times seem to have brought out some thought, an inkling of where drivers "should" be located. By the writings we have all read, spacing according to crossover frequencies started showing up...then we had offsets showing up, likely from baffle step mathematics.
Your notation of "...woofer at...'max gain'" I'm guessing applies to my "design" and/or the Infinity Qb...but the factory preferred Infinity option was the rather cool looking stands...which would null out any "hooking" effect by not using the floor as part of the baffle.
Myself doing some preliminary work on the baffle-step programs, the centering of a full-range had awful results, each panel being the same distances seemingly reinforced & added to the errors.

 

[GM]

My comments are based not only on the baffle's, but the cab's [room] nearly identical internal eigenmodes.

The baffle's will be lower though due to the baffle's [pipe] WxD end corrections.

GM

 

[GM]

Looking at the likes of the venerable L-100 & its studio counterpart, there seems to be no rhyme or reason on driver placement.

Your notation of "...woofer at...'max gain'" I'm guessing applies to my "design" and/or the Infinity Qb...but the factory preferred Infinity option was the rather cool looking stands...which would null out any "hooking" effect by not using the floor as part of the baffle.
Myself doing some preliminary work on the baffle-step programs, the centering of a full-range had awful results, each panel being the same distances seemingly reinforced & added to the errors.

Somewhere there was a thread that dealt with the math of these types of driver layouts, but didn't save it.

Well, I quoted your Infinity Qb quote.......

Boundary gain is a mirror image phenomenon, so totally separate from driver/box eigenmodes.

Indeed! No 'seemingly' about it.

A [super] tweeter's pass-band OTOH is high enough that combined with its sealed rear chamber this summed baffle null just adds some minor pressure to its front side.

GM

 

[norman bates]

Ok, some progress..........

W8s, acoustuff, binding posts, builder even.

Wife likes this dark mocha with black baffle (see below as an example).

33" tall x 20" wide x 13" deep (driver center 20" off floor".

Sealed but qtc below .6, f3 probably 65hz

Too big, i know, but gets driver firing high enough to see over furniture arm.
Not ported, i could, but usually i hear junk coming out of the port, so sealed only.

 

[Richard Ellis]

The numbers on the Visaton B200 eight-inch FR sound nice...if you can get some 12.9 cubic feet worth, to get an f3 of twenty hertz.
Just for s' & giggles using the 2001 Monolith ratios, one, four, nine...
There, I can go up 0.707 and to one side 0.618
Roughly 8 1/2" deep, 34" wide, 76.5 tall...


-------------------------------------------------------------------------Rick.........

 

[GM]

Not ported, i could, but usually i hear junk coming out of the port, so sealed only.

Critically damping the vent solves it and one reason why the pioneers used fairly dense grill cloth.

GM