Deco Survey :)

Which plate/logo/badge you prefer ? See pictures below :)


  • Total voters
    30

hcsterg

Friend of Fred
Feb 13, 2012
6,567
France
OK Guys : it's not about guitar or amps, but Hi-Fi loudspeakers... :)

I recently designed and built a pair of 3-ways Bass-Relfex enclosures :

I7krMb-P1120861.jpg


I7krMb-P1120862.jpg


And as you can notice it below, I have drilled a pair of holes destined to attenuators that I won't finally install, so I have to make them disappear...

LHowMb-the-holes.jpg


The easiest solution is to plug/seal these holes and cover them with a nameplate of some kind. I designed 3 different models - CIRCULAR, SCHEMATIC and MIXED - see below (you can click to zoom) :

OKnwMb-plaplakz-03-09-2021.jpg


- 375L is the code name I gave to the project (for : 3 Ways / 75 Liters).
- the plates will be from plexiglas back-painted silver, and laser back-engraved black.

If you were me, which one would you prefer ?

Up to 3 selectable responses allowed. ;)
Any comments or advices are welcome, indeed ! :cool:

Thanks !

A+!
 

DennisC

Country Gent
May 11, 2017
1,337
Germany
I like the schematic. I'm not that much into Citroen, but I love that their badge is symbolising a twoway angled gearing, for that this does neither apply axial forces, nor has the irregular transmission a straight gear has, runs silently and perfect (and is the most expensive solution, but often you can get away with cheaper bearings - hence the axial forces and lack thereof), and as Citroen made large gearboxes for industrial equipment before they got big with cars, ...

I love that Bosch's logo symbolizes an ignition generator, or generally, when companies that are in engineering and technology have their badges symbolizes something about them, something that is their USP in best case artworks.

Therefore, I'd prefer the schematic. Circuit over circular!
 

hcsterg

Friend of Fred
Feb 13, 2012
6,567
France
I finally opted for a mix version of ideas, in a smaller 70x92mm format, just enough to cover the unexploited attenuator holes :

X1vxMb-2021-09-06-222345.jpg


Very interesting. I would be curious to know what drivers you selected and how you designed the crossovers.

Here it is, @guitarfarm :

UN6vMb-FILTRE-6-12-S-P-27-08-2021.gif

With Rtw2=3.9R and Rmr1=2.7R for reaching the suitable balance level.

The crossover is an hybrid "serial-parallel , 6dB/oct with 12dB asymptote, phase and impulse coherent" design. The MR is fed by the differential signal from TW and WF, that is to say the 400-5000Hz band.

A+!
 

guitarfarm

Country Gent
Dec 29, 2008
1,339
Neither here nor there...
Properly crossing over three-ways is always a tricky proposition. Did you build the cabinets yourself? How did you minimize standing waves?

The last pair of two-ways that I built had 1-1/2" thick walls all around with Black Hole and 2" acoustical foam inside. I'm toying with the idea of building another pair, but would like to use poured concrete for the cabinets. Still working out the details for that in my head. Speakers have always been a little hobby of mine.
 

hcsterg

Friend of Fred
Feb 13, 2012
6,567
France
Properly crossing over three-ways is always a tricky proposition. Did you build the cabinets yourself? How did you minimize standing waves?

The last pair of two-ways that I built had 1-1/2" thick walls all around with Black Hole and 2" acoustical foam inside. I'm toying with the idea of building another pair, but would like to use poured concrete for the cabinets. Still working out the details for that in my head. Speakers have always been a little hobby of mine.

Fine @guitarfarm !

I posted the details of construction on this little forum :

http://diyaudioprojects.com/Forum/viewtopic.php?f=11&t=7061

Yes, 3-way Xovers can be more difficult to set-up than a 2-way one, but it largely depends - if not all - on the loudspeakers performances in linearity and bandwidth.

These two qualities will help greatly in the design of the crossover, allowing you to choose more freely the FC of the LPF and HPF sections, in the sense of the usual "distance condition" of 2x between the limit of the speaker (FS, directivity) and the FC will be easily met and overtaken if possible.

De facto, you will less be forced to use steep slopes crossovers (18 or 24dB/oct) with their numerous parts - and matching cost ! - 12dB/oct or even 6dB/oct are possible - though subject to certain conditions well documented in books such as The Loudspeaker Designer's CookBook by Vance Dickason.

In the 2-way Xovers, you only have one FC to choose (or vary around with FCH (TW) and FCB (WF)) so it may appear more simple, but not necessarily : your speakers will have to work in wider bandwidth than in 3-way and also be more linear. That's why matching a 15" with a horn (and its often tormented impedance curve) is sometimes difficult to met...

"What you earn on one side is lost on the other side", if I can say so. ;)

Yes - as you'll see on the link I posted - I designed and built the cabinets by myself, with quite basic woodworking equipment (nothing to do with some guitar builder members of the forum ! :rolleyes:).

For minimizing the standing waves, I fill (or stuff) completely the cab with cotton wool insulation mattress (available for home insulation at moderate cost), the enclosure being sealed or bass-reflex, no matter.

lm6rMb-P1120871.jpg

mm6rMb-P1120872.jpg


Here are the details of the stuffing of my 375L cabs :

mm6rMb-P1120876.jpg

mm6rMb-P1120877.jpg

nm6rMb-P1120878.jpg

nm6rMb-P1120879.jpg

IGNrMb-Filling-stuffing-position-21-08-2021.jpg


Of course, the midrange "Recycled Plastic Flowerpot" sealed cavity makes no exception :

mm6rMb-P1120869.jpg


I found this technique to be very advantageaous :

1 - the distribution of the dimensions of the cabinet are largely secondary for standing waves counteracting, considering the efficiency of the stuffing in that field. No need to hassle with Gold Number proportions, you satisfy your eyes proportions... :D

2 - the full stuffing offers an increase in acoustical volume of the cabinet of currently 15 to 20%. Stuffing increases CAB, the acoustical compliance of the box. That means that for reaching the same F3 as the fully stuffed box, you will need a cab which will require a 15-20% larger physical volume if you intend to left it empty or lightly damped.

3 - By physical laws, a damping material is more efficient against satnding waves if it is placed at (and around) the center of the volume (where there is acoustical speed) rather than on the faces (where there is acoustical pressure).

4 - I know that it is rather subjective, but due to the taming of the internal (and often uneven) resonances, the tone is more neutral with full damping, because these ionternal resonances do not go out from the inside to the outside through the port or the woofer / woofer-midrange cone.

Of course, you must not "plug" the ports if it is a BR cab and not put the stuff directly against the speaker in any case : full stuffing doesn't mean compressed, crammed stuffing, right ? The goal is to reduce and even the speed of the acoustical waves, not to "clog" them !

I invent nothing here : among others, A. L. Thuras (WE engineer, from the 30s) along with Vance Dickason, Martin Colloms (Monitor Audio) are in favor of this solution. And I must confess that, by my personal experience, I really noticed the benefits of this full-stuffing method.

OK, not everybody agree with that procedure, that have huge detractors ! :D

Beside that, I don't know what you call by Black Hole, but I suppose that is is some kind of damping tar sealant or coating ? o_O

A friend of mine used this, and beside the always more or less remaining petrol odor, the slow solvent emanations ended to harm the louspeaker suspensions :mad:... So I don't use that kind of product, which is moreover rather unpleasant to handle ! :rolleyes:

Bulding a speaker cab using concrete or staff is another story, not to say a courageous enterprise ! Are the benefits worth the work and the untransportability ? o_O You decide for yourself.

With friends, we made some attempts, and the worthiness as mentioned before was judged rather questionable... We had better and more practical results in that field using hollow panels that we filled afterwards with dry sand, though.

That said : why not ? Like in the Great Guitars, Effects and Amps World, the truth is never written once for all, and for everyone ! :)

A+!
 
Last edited:

guitarfarm

Country Gent
Dec 29, 2008
1,339
Neither here nor there...
Blackhole mat is a heavy damping material that once was used exclusively for high end audio loudspeakers, but then was pretty much taken over by auto sound enthusiasts. Their product line has changed considerably over the years until now it is nearly all aimed at the auto market. I had a large roll of it in a closet leftover from when I built a pair of Seas Thor transmission line towers 20 years ago. Reminds me of those heavy lead blankets they put on you when you get your teeth x-rayed. I'm not sure if they even make the mat any longer.

The last two-ways I built employ Scan-Speak 15W8530K00 mid-woofers and the incomparable Hiquphon OW1 tweeters. Crossovers are tuned for just under 2,500 Hz. Tweeter filter is third order electrical, woofer filter second order electrical. Enclosure is 15 liters internally and employs a 2" rear port that is 7" long. This tunes the enclosure to roughly 43 Hz with an F3 of 39 Hz. Aside from being 1.5" thick all around (void free plywood), the cabinets are nothing fancy, although they look a bit strange because they are deeper than they are tall. The speakers work their best resting on heavy, solid stands. Despite their diminutive size, these are not bookshelf speakers because they require 2 feet of space between them and the wall behind them. The bass is startling out of such a small package. One of my friends asked me to turn off the sub so he could hear just the two-ways. I had to explain to him that there was no sub. The tweeters are everything you would expect from a Hiquphon product. Cymbals are clearly resolved and bells actually "shimmer". Comparable systems on the market would be the SCM19 from ATC Loudspeakers or the C7ES-3 from Harbeth.

I cannot explain my fascination with two-way loudspeakers. I have had it for more than thirty years, despite owning large tower systems for most of that time. I am in my 60's now and I feel that I have one last set in me. If I build them, they will be what I think of as an "ultimate" set of two-ways. No expense spared. Which is what has me laying in bed at night thinking about how to pour cement enclosures. :confused:

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