Ceramica. A three way loudspeaker.

[Norm]

Bukem,

Major kudos and thanks for sharing. These advanced projects are a real draw to this forum. I am curious about the wonderful looking paint job. Were the panels disassembled for paint or left assembled as shown in the pics? Has the paint been color sanded and polished or did your painter achieve that finish straight out of his gun?

[Bukem]

Hi, thanks for the kind words. Tolerances would not allow painting of the individual panels before assembly hence I chose to assemble first and then paint. During the design phase I purposely created a recessed seam.

There are several layers of (wash)primers, lacquer and clearcoat. The lot is then wetsanded and polished. There are a few details which still require some further polishing. Not quite there yet...but getting there!

[Bukem]

A few more bits and pieces posted in my photo blog amongst which a completed midrange enclosure.
URL: https://imgur.com/a/oVPRa9f

I did not do a 360 of the bitumen adhesive sheets because this would interfere with the brackets for the bass drivers.

[5th element]

Well they look awesome

[Bukem]

Big moment.

Speaker meeting the stand for the first time!

[Bukem]

Mounting the tweeter + grille (epoxy) + tweeter cap:

[Dave Bullet]

Absolutely beautiful! Do you have any idea on various panel resonance frequencies?

[Bukem]

No idea yet what the resonance frequency of the various panels is. Knock test is encouraging.

Unfortunately, bracing was not feasible due to the tight layout. However, the woofers are a force cancelling pair and suspended in elastomeric o-rings. The midrange is also suspended in an o-ring.

Given the panel thickness/stiffness and the abovementioned design choices I think that panel resonance (amplitude) will be acceptable.

If not, I can try to increase stiffness or add mass depending on the issues which might arise.

Tks for the kind words.
Richard

[BobEllis]

Beautiful work. I admire those of you that can resist the urge to rush to completion.

It might be worth an experiment with hard gaskets at least on the midrange. That’s based on Jon’s comments about front panel stiffness and creating a hard driver launch point giving lower distortion. (He mentioned this in one of the Ardent threads, IIRC). By soft mounting you create another resonant system, which interacts with other cabinet resonances. Even if well damped by the elastomer it’s still another bit of movement not commanded by the signal.

[Bukem]

Hi Bob,

Very good point. I have not thought this through apparently. Since the Cell driver can only be fixed via a compression fit using an o-ring I suppose what I can do is look for an o-ring with a higher ‘Shore’ rating, i.e. a stiffer compound.

I will give this some further consideration. Again many thanks for thinking along with me.

[Matt M]

What I remember from the Ardent investigations, that Jon experienced a distortion spike around 500 Hz, assuming the frame of middriver to be responsible. Another C90-6-079 user (Christoph Gebhard on diy-hifi-forum.eu) mounted the driver on damping rings like these:

http://gummipuffer-wagner.de/Gummipuffer-Typ-C-O10x10-M4-4-NR-55-GRAD-Shore-Stahl-verzinkt::801.html

Initially I had my reservations similar to what Bob stated. I had expected the system to become more lossy and expected a lowering of QMSc from the application of those damping rings, i.e. an increase of mechanical losses. Surprisingly, the opposite happened: QMSc increased even further. More important, the distortion spike Jon measured, and C. Gebhard as well, was significantly reduced. He also did not report a subjective loss of clarity or otherwise detrimental effect.

Another way to look at it: cabinet resonance appears to be excited by structure rather than air. So, decoupling the driver from the cabinet will have its own merits. Which effect is more important in the end? Hard to say.

Intuitively, I still favor Jon's approach, for the reasons bob mentioned, but it is not a really a straightforward thing IMO.

Bukem, to say "this build looks incredibly professional" would be a massive understatement. Just wow!

Where did you source the Tecnocell wall liner from?

[Bukem]

https://www.akoestiekwinkel.nl/catalog/product/view/id/719/s/tecnocell-akoestische-platen/

[Juhazi]

I cant stop wondering, what is the real advantage of rubber rings between driver and cabinet. The driver will be screwed on the baffle anyway. Rings may attenuate mechanical vibration conduction a bit, but have their own elastic modulus and resonance added....

[Bukem]

No driver is screwed. C90 cell is a compression fit and the Wavecors are held in place by their magnets.

[Dave Bullet]

No driver is screwed. C90 cell is a compression fit and the Wavecors are held in place by their magnets.

It's a sealed box design right? I meant resonance not from mechanical transfer but pressure waves inside the box caused by cone excursion.

[Juhazi]

..And I meant in general, this Ceramica is an extraordinarily well thought out project! I don't remember if I've ever seen compression-fixed drivers!

Also generally speaking, resonances and internal standing waves should be either below or above passband. Somehow manageable in 3-ways speakers?

[Bukem]

It's a sealed box design right?

Yep.

[Bukem]

..And I meant in general, this Ceramica is an extraordinarily well thought out project! I don't remember if I've ever seen compression-fixed drivers!

Here you see the detail:

[Bukem]

Also generally speaking, resonances and internal standing waves should be either below or above passband. Somehow manageable in 3-ways speakers?

Woofer Enclosure first mode based on dimensions is 476Hz

[Bukem]

I meant resonance not from mechanical transfer but pressure waves inside the box caused by cone excursion.

I guess this could only be due the frontpanel flexing. Given the dimensions of the frontpanel (284.56 x 30.00 x 410.00 mm) I think it will be stiff enough to withstand the pressure waves generated. Time will tell...

[BobEllis]

Are the silver bits in slots cams to hold the driver in place? If so, the o-ring looks like an air seal only and the driver is hard mounted.

[Bukem]

Are the silver bits in slots cams to hold the driver in place? If so, the o-ring looks like an air seal only and the driver is hard mounted.

Nope. Picture this.

The grille is a separate part as is the basket. Both edges are chamfered and at the intersection of both parts you have the o-ring. The silver bits are M3 screws which secure the grille to the basket. When you tighten these the o-ring is pushed outwards against the enclosure opening, hence it compresses.

[wolf_teeth]

That's how I thought it worked but was uncertain. Thanks for the clarity!
Wolf

[Bukem]

Absolutely beautiful! Do you have any idea on various panel resonance frequencies?

Do you guys have any suggestions for an accelerometer? Or any other suggestions on how to best measure panel resonances?

[Steve Manning]

Do you guys have any suggestions for an accelerometer? Or any other suggestions on how to best measure panel resonances?

Typically this is done with a laser vibrometer. I know they are not cheap. Don't know if they can be rented or someone local can provide the service of one?

[ergo]

Bukem,
Check out the thread here

George Ntanavaras is a guy in Greece who builds preamps (ready to go or as a kit) for a ACH-01 accelerometer. I've bought one from him and it works well. It's reasonable price package all is all and can be used with CLIO or ARTA or ...

[Bukem]

Tks, I will investigate ;-)

[Matt M]

https://www.akoestiekwinkel.nl/catal...tische-platen/

Thanks! Was your choice based on manufacturers specifications, aesthestics, or a subjective preference in testing? Looking nice for sure...

[HTDT89]

@Bukem

What happened??? You were knocking this project out of the park!

[Bukem]

Tks. I've had some bad luck with one of the tweeters which meant I had to disassemble one of the speakers and return the tweeter for repair to Denmark. No worries. I expect to be back with new updates pretty soon.