3 Way Floorstander Build - Striving for high end...

You can share the greber files to convert to CNC and let the forum experinace your great handy work first hand. Good Stuff 

Gotta say I agree with this post. Although these projects are way above my skill level I find them fascinating reading. Posts are very detailed with loads of information 

Looks front-ported to me edward .... Could be wrong though.

Either way, having this much control of a build like this will be rewarding and result in exactly what you want.

Brilliant.

I must admit I was a little apprehensive about anything that could 'muck up the project' and have a detrimental effect on the sound quality. Troels projects have a very good reputation for the end result, I just needed to ensure the cabinet was very good. I go into the technical details of the construction soon...

There is a port on the front under the bass driver. The pictures are very dark so it is difficult to see. It will become more obvious on the next posts.

Verycool.com 😎😎

Thank you!

A CNC machine would certainly make these speakers quicker to build, but they'd still be a surprising amount of work (more details on construction to follow). The design is pure indulgence and certainly not time or cost efficient to build. I was striving to build something unique and, as usual, went a bit OTT!

Are these a kit that you buy ? What’s the cost?
If so I’m also interested in them as a future project.

I'm still in the development and costing phase at the moment. I hoping to produce a prototype soon (next few months) and then I'll be testing it to see how well it performs. I know many people who would like to access the DIY speaker VFM and performance benefits, however, they don't have the skill and/or time to build the cabinets. I'd be aiming to produce a ready made version or make cabinets as required. I strongly believe a well designed and well made 'boutique' speaker with high end components will present great VFM and would be something to be proud of.

No current plans for a kit version, but it is certainly something I shall consider. There are, however, many options available. I would strongly recommend Troels Gravesen. He has an extremely good reputation and 1000s of people have built his speakers - he has many testimonials to prove it. He has plans for the cabinets, but they are completely self build (no flat pack cabinet kits) All of his kits have prices via a link on his website:

www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm

There are plenty of places that make straightforward (home assembly) cabinet kits too.

Would you be seeking a kit with flat pack cabinets?

Ah sorry, these speakers (detailed in this thread) are the Ekta MkIIs and are a Troels kit, yes. I believe the kit is around £1600—1800 depending on exchange rate. I have upgraded my crossover further too. The cabinet cost would be in addition to this. Bear in mind that my cabinets were pretty pricey as I designed something bespoke and very substantial. Something similar to the Troels cabinet would be a fair bit cheaper

DESIGN: STRUCTURAL REQUIREMENTS & AIMS

I spent quite some time pondering the construction and went through quite a few iterations and ideas.  My main requirements/aims for the cabinet were:

1. HEAVY!  I wanted a solid and heavy cabinet.  A good dense construction with a low centre of mass.  These speakers would not topple easily and I was aiming for very little cabinet movement when really cranking out the bass!
2. ELEGANT AND UNIQUE:  This is obviously very subjective, so I mostly designed what I (and my wife) really liked the look of.  I asked the opinions of a few friends and family.  I tried to aim for a relatively unique design - not easy with so many speakers out there!
3. MINIMISE INTERNAL STANDING WAVES: This is usually achieved by minimising the number of internal parallel surfaces.  The distance between any two parallel surfaces in a cabinet (or HiFi room) with have a corresponding frequency at which a standing wave will constructively interfere with itself.  This will result in a cabinet (standing wave) resonances at various frequencies corresponding to key cabinet dimensions.  This can be reduced by reducing the number of parallel surfaces.  More on this during the specifics of the design.
4. GOOD DAMPING: I had no scientific way to accurately measure this, only really by tapping with my knuckles!  However, I gave some thought to various ways in which I could increase damping within the cabinet.
5. SOLID AND WELL BRACED: The cabinet would have relatively thick, dense walls and any large wall areas would be braced.
6. CROSSOVER ACCESS: I wanted easy access to the crossover - mainly for any upgrades or tweaks.
7. FRONT PORT POSITION:  I opted to place the port on the front under the bass driver.  This should make the speaker more room friendly.  It was initially designed (we've now moved) to work in a small room and had to be 20-30cm from the wall behind.  I feared a rear port would not work well in this environment.
8. STAY WITHIN THE TROELS GRAVESEN REQUIREMENTS: Last but not least, I had to keep the front panel dimensions the same as the Troels Ekta MkII cabinet and had to keep the driver positions the same.  The volume must be consistent and the port tuning remained the same also.  Changing any of these would render the crossover inadequate.

There are quite a few Troels two way standmounts using similar drivers to these floorstanders. They range from quite compact to reasonably large standmounts.

Are you interested in a standmount with this sort (pictured above) of cabinet styling? This cabinet design is very costly to make but could certainly be done as a similar style standmount.

I am currently developing a standmount and floorstander cabinet with a similar and more simplified styling feel, and it would be much more time efficient to construct.

The performance/SQ gains from a DIY/Bespoke design certainly attracted me. I love a project and making things too. There are obvious risks, as a poorly designed/built cabinet could have a very detrimental effect on performance. The other big challenge is to choose the right speakers for your system and room. The synergy with everything else is extremely important and it's difficult/impossible to try before you buy with DIY.

I am pretty sure my speakers perform at a level well above their cost (more on this later), but haven't done many A-B comparisons.

Are you planning to make cabinets yourself?

THE DESIGN: CABINET STRUCTURE

The following diagram shows a partially exploded view of the cabinet:



The front baffle compromises two mdf panels bonded together: the rear panel is 18mm thick mdf and the front 22mm.  This created a 40mm thick laminated front baffle which should be heavy, rigid (especially when braced) and pretty well damped.  {NOTE: some will note that the tweeter/mid horizontal offset will not be 20mm - this is addressed later on} As explained previously the lower (main) side cheeks will be constructed from 40mm bamboo ply:



This is a stunning material and very dense.  It is generally denser than Birch ply and should be reasonably well damped with it's laminated structure.  Technically it's a grass too, so my speakers are mainly constructed from grass!    It is certainly heavy, as each cheek was around 10kg when finished.  I have heard it is extremely stable and this has been my experience so far - very little movement and negligible expansion/contraction with humidity variations.  It proved reasonably easy to work with - more on that later.



Each cheek will be sculpted (painstakingly!!!) into a curve on the outside.  This results in a panel which is 20mm thick towards the front, 30mm at the rear and 40mm at its thickest.  The variation in thickness over the panel surface should help with the reduction of panel resonances.  This is mainly hypothesis, and something I'd like to experiment on more scientifically in the future.

The rear spine of the speaker is a lamination of three (40mm thick) layers of bamboo.  Each layer is cut into a wedge shape before bonding into the complete spine.  The wedge shapes are mainly to create an extremely rigid and stiff spine without too much reduction in internal volume.  The maximum depth of the spine is 60mm from wedge tips to the rear.  I was aiming for an incredibly stiff spine - this would help to stiffen the entire cabinet.  The 40mm front baffle and very stiff (rear) spine would be braced in multiple places from top to bottom - once the cheeks are bonded on the structure would be extremely stiff and rigid.  

The sides are non parallel and this will help to minimise side to side standing wave resonance.  The rear spine is reasonably narrow which should help to minimise the reflections from front to back.  The spine wedge shapes may help a little with reflections, however, in reality the problem wavelengths are generally much longer, so not really affected by the wedge structure.  Still, it looks cool and adds stiffness!



The crossover is at the base of the speaker and completely separate from the main bass driver chamber.  This keeps the sensitive crossover well away from any magnets and provides some isolation from airborne vibrational energy.  The panel which separates the crossover chamber is 25mm thick and slanted from front to back.  This was done to remove any (internal) parallel faces from top to bottom.  The largest and (usually) most problematic standing wave in a floorstander is from top to bottom - this relatively long dimension will result in a resonant frequency usually around 150-200Hz and was a frequency I was keen not to reinforce too much.  The mid/tweeter chamber at the top will assist further at alleviating the top-bottom standing wave - this chamber effectively shortens the distance in the front half of the cabinet.
 


The midrange driver and tweeter are completely independent in their own sealed chamber.  This creates a suitable cabinet volume for the mid driver and helps to isolate it from the high energy pressure waves leaving the rear of the bass driver.  In addition, the tweeter has it's own tiny chamber to further enhance any isolation - perhaps overkill as it is fully sealed anyway.

The bracing can be seen in the above images and the speaker will sit on a heavy (40mm thick) granite plinth.  All braces are rebated for extra strength and stiffness.  The top panel is a lamination of 18mm plywood and 12mm mdf - this creates a 30mm thick lamination of two different materials.  This should be very well damped also.  All internal walls will be further damped with 4mm thick bitumen panels.  In addition, there will be heavy felt on all internal surfaces, and finally some further acoustic damping (more details later).

OK, I went to town on the design!!!   It won't be perfect, but I have certainly tried to address potential speaker cabinet issues.  I certainly haven't addressed everything, as there's only so much one can do with limited tooling and experience.   I had no means of testing the design implementations, so a lot of the design is based on what I thought would work.  I am hoping to gather more test equipment and one day design a cabinet based on more rigorous testing.