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3wayaddict 14th May 2019 09:44 AM

Redesigning my cabinets. Thoughts?
 
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Hello,

Not an ultimate concept this time (even though it's quite close).

A while ago (December) I built my active tower speakers. Because didn't setup the crossovers properly they now get quite harsh and overly bright with anything that isn't superiorly recorded "audiophile" music. Obviously I could mostly fix all of this by just resetting the crossovers, which I will eventually, but I'm in my finals right now, almost done with school and I'll have about 4 months of vacation. 2 of which I'm at home. So I have lots of time to do whatever I want and earn quite a bit of money.
My current cabinets I have worked my a s s of to design and built and it's not a bad design by any means but it's far from perfect. It's all square both for the outside and inside (except for the midrange chamber). There's some pretty bad diffraction going on with the current baffles and even though they weigh over 60 kg each, are constructed out of 1" thick high-density MDF and have lots of bracing in them, the cabinets aren't as stiff as I would wan't. The sides, despite the bracing, are vibrating quite a bit, and the entirety of the cabinet of course.

So I'm rebuilding my cabinets. They will have curved sides for extra stiffness, eliminating standing waves and minimal diffraction consequences. And it will be modular. The tweeter, midrange and woofers will each have their own separate little box which are then stacked on top of each other. This again reduces standing waves and resonances in the cabinet and the separate enclosures can be decoupled by putting soft felt in-between the separate boxes. This way the midrange and tweeter don't pick up any vibrations of the woofers. This should greatly increase clarity and spaciousness. And also, I don't have to rebuild the entire cabinet when for example I want to change tweeters.

Because of the curved edges, the cabinets will be constructed by stacking layers of 1" MDF. This also allows for easier and stronger bracing. And instead of 1", the walls of the woofer enclosure will be a little over 1-1/3" thick for extra stiffness. There will also be a small beam of an additional 1" thick walking over the middle of the sides from top to bottom. So the woofer enclosures should be a lot heavier and stiffer.

The for the midrange chamber. The thing that IS great about my current enclosures and that pretty much makes the entire speaker as good as it is, is the internal design of the midrange chamber. It has these big defusing shapes in it. With the current design it's made by stacking MDF plates with bigger and bigger diameter holes in them. Because of the oval shape of the wall with this design, that's a lot harder to do. So instead I've come up with this. amongst the walls there's cubes that get bigger and bigger towards the top and bottom of the box and with every layer the cubes on the left sides stick out a little further than on the right side, and then the cubes on the right side stick out a little further than on the left side on the next layer. This should make for a GREAT diffuser, probably even better than in my current enclosures, especially in combination with the curved walls.

3wayaddict 14th May 2019 09:51 AM

This design should make for extremely minimal cabinet coloration. With the crossovers properly setup using the nice new laptop which I'm gonna buy instead of having to borrow my parent's all the time and being time restricted, this should make for something truly phenomenal.

cspieker 14th May 2019 11:13 AM

1" mdf is a great start to a very solid cabinet, can't you reach in the driver holes and add some bracing?

You may be overestimating the sonic gains you will achieve by decoupling cabinet sections and reducing diffraction. Compared to the crossover being right, thats small fish. I'd set up the crossover perfectly before making such a heroic box. You may decide during that process that you want a different driver somewhere.

celef 14th May 2019 12:35 PM

I agree, put all effort on getting the crossover right, and this can take a long time

Sure, building overkill boxes might feel good but the heart, the brain and the soul of the loudspeaker lies in the crossover

ICG 14th May 2019 01:01 PM

Indeed, build a test enclosure first.

The mid-high enclosures got a different size and there are flat surfaces sticking out - not a good idea! That will give you reflections (-> unlinear response) and uneven dispersion. either round it off greatly or use the same size and shape there. You didn't plan for avoiding length standing waves.

The assembly/gluing of the layers will be a PITA. To improve that, make 2 bores in each layer, at the same location on each one, from top to bottom and stick metal rods into it, that way they will always line up perfectly. You can remove the rods later. You should probably make the straight baffle boards removable, that way you can swap for a different board for other drivers.

The speakers will be very heavy. Did you plan for any feet? To get the speakers off of the ground will help a lot regarding the room impression.

Mario Pankov 14th May 2019 01:28 PM

You`re getting closer to a very good enclosure. The planes below and above the offset tweeter will create frequency response irregularities. A better way to offset it would be to either have these chamfered/rounded to a large radius (if the design allows it), or to put the tweeter in a waveguide which offsets it and saves all the trouble with the complex box design. Some, like the Visaton WG148R and the Monacor WG300 will offset it just right for a typical 6-7" woofer (small adjustment may be required, like a slight tilt but will be really small).

The sharp internal diffusors will be hard to machine, unless its laser cut and will have worse effect than round pattern (wave-like) which allso happens easier to machine. It can even be done at home with a router template and a quality router.

3wayaddict 14th May 2019 04:49 PM

What do you mean exactly with bracing in the driver holes?

I know it's al about the crossover. But I'll be rebuilding them anyway. Because yes the crossover is the most important, but that doesn't mean a better enclosure isn't better. And I know the difference won't be like going from the Focal Chorus 716 to the Grand Utopia EVO but I know for a fact that the cabinet will make an improvement, and I now I'll have the time and money to do so, I want to make every improvement I can to the speakers physically as well.

Yes the speakers will be very heavy. I'm just guessing around 80 kg each looking at the what my current speakers weigh and the amount of wood used to construct them. But I don't worry about weight. In fact, from a sonic perspective, the heavier, the better. And for moving them around they also won't be that much more difficult because of the modular design. I will be putting them on feet. I've got spikes that should be able to hold them just fine.

Putting rods through the sides might indeed make thing easier. I'm gonna try to do that.

The tweeter won't be offset. The modular design is not meant for time alignment like with Wilson Audio speakers. The modular design is purely meant for decoupling and not having to rebuild the entire cabinets would I want to change drivers. Time alignment is handled in the DSP.

I already had another design of the midrange diffuser. Similar but just smooth curves instead of cubes but I thought it might not be effective enough. I'll look back at that design and might come up with something different. The proper diffusing in the midrange chamber really is from upmost importance. You keep bragging about the crossover which is definitely also very important but to my experience the treatment of the midrange chamber seriously is just as important, and I'm not over exaggerating. Seriously, I've done some experimenting with different shapes of the midrange chamber and amount of damping and it seriously makes the entire speaker.

3wayaddict 14th May 2019 07:52 PM

Wait, I red one of your replies wrong. Forget about the last part of my last post.

How do you think the shape of the midrange chamber will work as diffuser?

cspieker 15th May 2019 02:15 AM

"What do you mean exactly with bracing in the driver holes?"

In the cabinet you are using now. If you can reach inside, and place braces. Pieces of wooden curtain rod can be used as braces. Difficult to place and secure, but possible. 2 months doesn't sound like long to optimize a crossover, let alone build and finish a cabinet that complex. Remember to multiply your estimate of how long it will take you by 3. (that's just how it seems to go).

studiophone 15th May 2019 04:15 AM

So it’s an active xo with separate amps for each frequency? If it’s a passive 3 way I’d say you will need more room than the black box. How are you wiring all the drivers? Can you go into a little more about the system please.


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