Metlako: A Small, Affordable Two-Way Unity Waveguide - Page 2

Patrick Bateman · 3rd September 2019, 09:44 PM

Oh, one more thing:

See that dip at 1800Hz? That's a crossover problem, not a waveguide problem. Basically that dip indicates that the midrange and the tweeter are about 45 degrees out of phase at the xover point. This can be fixed. I just didn't have time to get too obsessive about it. I spent all of twenty minutes making this crossover.

Sheldon · 4th September 2019, 01:05 AM

Very nice work!

Sheldon

pelanj · 4th September 2019, 08:08 AM

Patrick Bateman, I would love to have the STL file for printing the horn adaptors for the Vifa tweeter so that I could experiment with these. Would you be so kind to share/sell the file? Thanks.

Patrick Bateman · 6th September 2019, 07:18 AM

Quote:

Originally Posted by pelanj

Patrick Bateman, I would love to have the STL file for printing the horn adaptors for the Vifa tweeter so that I could experiment with these. Would you be so kind to share/sell the file? Thanks.

Hi Pelanj,

I'm going to start putting my waveguides in a repo, so anyone who wants the latest version can get them.

Stay tuned.

Patrick Bateman · 6th September 2019, 07:19 AM

Quote:

Originally Posted by Sheldon

Very nice work!

Sheldon

Thanks. You gotta come over and hear them!

Patrick Bateman · 6th September 2019, 08:08 PM

I made a new revision to Metlako. It features the following improvements:

1) The main reason I did it, was because the first Metlako has a seam that runs right through the throat. I wasn't thrilled about that because the throat must be PERFECT. Metlako V2 has *two* seams not one, but both are over an inch from the throat.

2) By going with three pieces, I was able to make it wider vertically.

3) I basically made the waveguide as wide as I could get away with, while still horn loading the tweeter. It's JUST narrow enough to load the tweeter, and no more.

4) I did some fairly outlandish things to make the midbasses fit. It's crazy looking, two of the midbasses are actually *behind* the tweeter. I literally spent hours shaving off a millimeter here and a millimeter there.

Pics:

zobsky · 7th September 2019, 03:19 AM

What is the efficiency of this design?
How low does it maintain pattern control
How large / small is it ?

Apologies if I overlooked the answers elsewhere in this thread

Thanks

kipman725 · 7th September 2019, 06:25 AM

I got 1.28kHz -3dB out of FaitalPRO 3FE25 (Qes=0.8) with a very small rear chamber and front volume reducers. Without reducing the front volume the -3dB was ~100Hz lower.

My understanding is that the upper frequency limit is set by a number of factors:
Mass corner frequency
Distance of taps from horn throat (for which a compression driver adds extra length so the dome tweeter has an advantage)
Front chamber/port volume low pass filter

Patrick Bateman · 7th September 2019, 06:41 AM

Quote:

Originally Posted by zobsky

What is the efficiency of this design?

Hornresp says 92.5dB

Quote:

Originally Posted by zobsky

How low does it maintain pattern control

With a waveguide that's 13" in diameter, I would expect it to lose pattern control at 1038.4Hz. But based on this measurement of the Metlako v1 polars, it maintains control to 800Hz.

Quote:

Originally Posted by zobsky

How large / small is it ?

The waveguide is approximately 13" x 9" x 3.5". It's literally the widest waveguide I could make that would load the tweeter down to the crossover frequency. See : The Preference for Direct Radiators

The enclosure is approximately 20" tall x 15" wide x 9" deep. That's 1.56 cubic feet. I'm using a QB5 vented enclosure maximize the power handling.

It should be good for 110dB maximum.

Quote:

Originally Posted by zobsky

Apologies if I overlooked the answers elsewhere in this thread

Thanks

No worries!

Sixto · 7th September 2019, 02:50 PM

Hi Patrick, I'm curious about the orientation of the midbass ports, comparing the black and orange waveguides on post 1. It seems to me that you can get the slots physically closer to the tweeter and more symmetrical in the X and Y direction if they are oriented radially like the black waveguide as opposed to concentrically like the orange waveguide.

Also I wonder of the sharp edges of the slots on the orange waveguide will cause some diffraction since they are perpendicular to the direction of the tweeter sound waves.

Maybe this is all a result of the new printing configuration, or the larger midbass drivers being used?
Thanks, Sixto

7th September 2019, 03:19 AM	#17
zobsky diyAudio Member Join Date: Mar 2002 Location: Dallas, Tx, USA	What is the efficiency of this design? How low does it maintain pattern control How large / small is it ? Apologies if I overlooked the answers elsewhere in this thread Thanks __________________ "Not everything that can be counted counts, and not everything that counts can be counted." - Albert Einstein

7th September 2019, 06:25 AM	#18
kipman725 diyAudio Member Join Date: Jun 2007 Location: Warrington	I got 1.28kHz -3dB out of FaitalPRO 3FE25 (Qes=0.8) with a very small rear chamber and front volume reducers. Without reducing the front volume the -3dB was ~100Hz lower. My understanding is that the upper frequency limit is set by a number of factors: Mass corner frequency Distance of taps from horn throat (for which a compression driver adds extra length so the dome tweeter has an advantage) Front chamber/port volume low pass filter __________________ CHR-70+Subs (2011?). ART CLEANBox Pro Low freq modification

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3rd September 2019, 09:44 PM	#11
Patrick Bateman diyAudio Member Join Date: Oct 2006 Location: San Diego	Oh, one more thing: See that dip at 1800Hz? That's a crossover problem, not a waveguide problem. Basically that dip indicates that the midrange and the tweeter are about 45 degrees out of phase at the xover point. This can be fixed. I just didn't have time to get too obsessive about it. I spent all of twenty minutes making this crossover.

4th September 2019, 01:05 AM	#12
Sheldon diyAudio Member Join Date: Dec 2003 Location: San Diego	Very nice work! Sheldon

4th September 2019, 08:08 AM	#13
pelanj diyAudio Member Join Date: Jul 2008	Patrick Bateman, I would love to have the STL file for printing the horn adaptors for the Vifa tweeter so that I could experiment with these. Would you be so kind to share/sell the file? Thanks.

6th September 2019, 08:08 PM	#16
Patrick Bateman diyAudio Member Join Date: Oct 2006 Location: San Diego	I made a new revision to Metlako. It features the following improvements: 1) The main reason I did it, was because the first Metlako has a seam that runs right through the throat. I wasn't thrilled about that because the throat must be PERFECT. Metlako V2 has two seams not one, but both are over an inch from the throat. 2) By going with three pieces, I was able to make it wider vertically. 3) I basically made the waveguide as wide as I could get away with, while still horn loading the tweeter. It's JUST narrow enough to load the tweeter, and no more. 4) I did some fairly outlandish things to make the midbasses fit. It's crazy looking, two of the midbasses are actually behind the tweeter. I literally spent hours shaving off a millimeter here and a millimeter there. Pics:

7th September 2019, 02:50 PM	#20
Sixto diyAudio Member Join Date: Dec 2014 Location: Minneapolis, MN	Hi Patrick, I'm curious about the orientation of the midbass ports, comparing the black and orange waveguides on post 1. It seems to me that you can get the slots physically closer to the tweeter and more symmetrical in the X and Y direction if they are oriented radially like the black waveguide as opposed to concentrically like the orange waveguide. Also I wonder of the sharp edges of the slots on the orange waveguide will cause some diffraction since they are perpendicular to the direction of the tweeter sound waves. Maybe this is all a result of the new printing configuration, or the larger midbass drivers being used? Thanks, Sixto