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Metlako: A Small, Affordable Two-Way Unity Waveguide
Metlako: A Small, Affordable Two-Way Unity Waveguide
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Old 14th September 2019, 08:10 PM   #41
Patrick Bateman is offline Patrick Bateman  United States
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I use these : Sure Electronics AA-AB33184 4x100W TDA7498 Class-D Amplifier Board
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Old 16th September 2019, 03:35 AM   #42
454Casull is offline 454Casull  Canada
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Quote:
Originally Posted by Patrick Bateman View Post
I think it will be difficult for Kef to "catch up" to Genelec without DSP; to me, it looks like Genelec is using FIR filters on their speaker to get those crazy-good polars.
In order from best to worst off-axis response:

Kef R300 Midrange Drive Unit Testing | Medley's Musings

Kef LS50 Drive Unit | Medley's Musings (results flawed due to non-flush-mounting)

Kef Q100 Speaker Drive Unit Testing | Medley's Musings

None of the off-axis tweeter responses shown can be fixed with FIR to the point that their polars would be similar to Genelec's; they're just too inconsistent. The R300 really isn't bad, though.
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Old 16th September 2019, 01:49 PM   #43
jzagaja is offline jzagaja  Poland
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Metlako: A Small, Affordable Two-Way Unity Waveguide
Quote:
Originally Posted by Patrick Bateman View Post
Metlako has been reliably printing in PETG but I really want to print most of them in ABS+, if possible. ABS is a nightmare to print, but the finished print just looks so much better.
Take a look on PP copolymers. Regular PP has strong shrinkage but copolymer can be good and part strong. My first printed horn, Iwata 600 in white pearl.

Next task - experiment with printed composites.
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Old 16th September 2019, 10:43 PM   #44
natehansen66 is offline natehansen66  United States
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Patrick I'm starting to have good luck with ABS. No enclosure yet, and it's counter-intuitive but in areas where the print gets thin or is being supported I'm running my fan at 15%. I've settled on 245 for a print temp as well. First layer bed at 100 and ramp up to 110 after that - my Prusa has no issues with the heat. Dry filament is necessary as well with ABS. I feel your pain about getting things to fit. I'm in the modeling stage of a near full range 3 way Synergy that I hope to print in ABS and it's looking pretty crazy getting all the drivers stuck on
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Old 22nd September 2019, 05:10 PM   #45
Patrick Bateman is offline Patrick Bateman  United States
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Ramping up the temperature seems to be essential for ABS.

For instance, I've been able to eliminate cracking almost 100% by increasing the bed temperature from 80C to 100C.

I'd go even higher if I could, but one of the fundamental challenges with my Monoprice printer seems to be that it's power supply is incapable of heating the bed beyond about 90C. I've been able to get up to 100C by adding two incandescent heat lamps to the enclosure.

PETG would definitely be less hassle, but ABS just looks so darn good when I print. Plus it's sandable.
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Old 22nd September 2019, 06:22 PM   #46
Patrick Bateman is offline Patrick Bateman  United States
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Here's some pics of Metlako V1 (orange PETG), Metlako V2 (black ABS+), my Waslo Cosynes (black plywood) and my Unitized Image Control Waveguide (black ABS+)

Click the image to open in full size.

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Old 22nd September 2019, 07:54 PM   #47
Zvu is offline Zvu  Serbia
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Quote:
Originally Posted by 454Casull View Post
In order from best to worst off-axis response:

Kef R300 Midrange Drive Unit Testing | Medley's Musings

Kef LS50 Drive Unit | Medley's Musings (results flawed due to non-flush-mounting)

Kef Q100 Speaker Drive Unit Testing | Medley's Musings

None of the off-axis tweeter responses shown can be fixed with FIR to the point that their polars would be similar to Genelec's; they're just too inconsistent. The R300 really isn't bad, though.
Here is Kef LS50 with revised passive crossover.

KEF LS50 playground - measurements of raw drivers in factory cabinets and simulations

And here is Kef R300 with also my revised passive crossover

Kef R300 playground - measurements of raw drivers
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Old 24th September 2019, 03:48 PM   #48
metzb1 is offline metzb1  United States
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Default ABS print temperatures

FWIW, I've settled on 95C bed temperature and 232C hot end temp for ABS. I have a delta-style sprinter and wrap a Harbor Freight moving blanket around the open perimeter to keep the heat in. I print on glass with a thin coating of Wolfbite. If I get the first layer right, I have no issues with cracking, warping, or lifting.
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Old 28th September 2019, 09:43 PM   #49
Patrick Bateman is offline Patrick Bateman  United States
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Over here, someone was asking about mounting a coaxial speaker on a Synergy horn : Synergy horn with coaxial speaker unit

There's quite a few Synergy Horns from Danley Sound Labs that use coaxials. I've done it a couple of times.

I think the "trick" to making it work is to understand how we can 'bend the rules' when building a Unity horn.

The Big Kahuna of Unity horn threads is here: Suitable midrange cone, for bandpass mid in Unity horn.

If you read the original Unity horn thread, listed above, you might assume that it will be impossible to mount a coax to a Unity horn. This is because 95% of the coaxial speakers out there don't have the "correct specs" for a Unity horn.

I think there's a few "tricks" that can be used to make it work. This "metlako" thread is definitely influenced by these tricks. Five or ten years ago, I wouldn't have tried this "Metlako" project, because making it work is theoretically impossible.

Click the image to open in full size.

The first "trick" is to understand how MTM speakers work. For instance, if you have two drivers seperated by half a wavelength, it will produce a beamwidth of about seventy degrees.

In a Unity horn, you can take advantage of how an MTM works, and space the midrange taps by a distance that will produce that beamwidth that you're looking for.

For example, if you have two midrange taps seperated by five inches, they'll generate a beamwidth of about 70 degrees at 1,350Hz. Here's the math:

speed of sound / distance / 2 =

13500 / 5" / 2 =

1,350Hz

Okay, so hold that thought, this is your first variable: where are the midrange taps going to go?

Click the image to open in full size.
The next variable is how far are the midrange taps from the throat? This variable has been discussed ad nauseum; basically you get a reflection off of the throat, and that reflection produces a notch in your midrange response. That notch sets the upper limit on how high the midranges can play.

Click the image to open in full size.

If I was going to put a coax on a Unity horn, it might look like this.

Click the image to open in full size.

The depth is 3.5". The depth is largely dictated by where we want the midrange taps to be. (See the beginning of this post.)

Click the image to open in full size.

Here's where your coax would go. The tweeter fires through the throat of the horn, and the output of the midrange fires through that ring shape.

Click the image to open in full size.

Okay, this diagram is super important.

It is *critical* that the area of the midrange tap is expanding.

Here's a few reasons why we want that midrange tap to expand:

1) this is still a horn. If the area of the midrange tap is constant, we're going to get a resonance. In the original Unity horns, from 20 years ago, the area of the tap was constant. The reason that it worked was because the taps were short. For instance, if your midrange taps are only one inch deep, it's ok if they're straight. But if your midrange taps are three inches long, or six inches long, or TWELVE inches long, you want the area to expand. If not, you're going to get a big ol' resonant peak and that's going to ruin your speaker. Long story short: you want those midrange taps to be expanding. If you're a complete madman, you can mass load the ends of those taps. That's a story for another day.

2) If the area of the midrange taps are expanding, the horn behaves a lot more like a horn. If the area of the midrange taps are NOT expanding, you're going to maximize diffraction off of the slots, and you'll probably get some reflections off of the transition from the midrange taps to the rest of the horn. Also known as "higher order modes."

If it's not clear from this post, the reason that the AREA of the midrange taps is growing, is because the diameter of the midrange taps at the throat and at the exit of the taps is higher.

For instance, at the entrance of the midrange taps, the diameter of the midrange taps is 2". At the exit, the diameter is something like 4". This means that the *area* at the exit of the midrange taps is 4X higher.

Click the image to open in full size.

Here's a cutaway giving a better idea of how the area of the midrange taps is constantly expanding.

Click the image to open in full size.
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Old 28th September 2019, 10:21 PM   #50
454Casull is offline 454Casull  Canada
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Is there any tweeter/mid combo available that can stack tightly enough to minimize the volume of the compression chamber in front of the mid?

Also, wouldn't the annular opening create a significant amount of diffraction from the HF?

Last edited by 454Casull; 28th September 2019 at 10:30 PM.
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