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Zilch's AK Design Collaborative - Econowave Speaker

Zilch said:
BB6P recommends tuning to 27 Hz w/ 1 x 3" x 12" for maximally flat alignment, green, but 30 Hz doubles the power handling in the low frequencies, 1 x 3" x 9", blue. Use an elbow to achieve these duct lengths. Shorten to 7" (33 Hz) for more punch, if desired, violet.

Yellow is closed box:

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Thanks Zilch, good info on a good "Econo" woofer! several have used it as such, maybe now we can see a few more. That Dayton 12 inch looks good to
for only a little more.....

Russellc:thmbsp:
 
Bauhausler said:
The difference in DCRs between 2 different gauges of inductors is likely to be swamped by the differences between two 'identical' woofers. DCRs of VCs, for instance, can easily be different by .5 Ohm. Unless high power operation is a concern, just get two of the same inductor of either gauge and use them together.
On the caps, however, I'm a little fussy. I have hundreds of crossover caps and resistors on hand for repair work. I'll test and hand pick to match caps to 3% or better between boards when repairing a high quality speaker. The drivers may have significant variation but eliminating additional variables from the crossover helps keep errors from 'stacking up' and causing audible differences. Just me being fussy from my days when I worked in steel and aluminum instead of wire and solder. When a tiny misalignment means an hour at a Bridgeport to make a new part you measure twice...
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Its an argument you just have to get comfortable with, some worry about stray resistance adding up, some capacitance matching is the big bugga bu. There's enough driver difference to swamp the minor capacitance matching issues as well. I still do it, cant just knowingly leave THAT like that, and so on.
Just so one can sleep at night. Funny how the smallest things just dont sit right until its just so. Part of the DIY charm!:D

russellc
 
Russellc said:
Its an argument you just have to get comfortable with, some worry about stray resistance adding up, some capacitance matching is the big bugga bu. There's enough driver difference to swamp the minor capacitance matching issues as well. I still do it, cant just knowingly leave THAT like that, and so on.
Just so one can sleep at night. Funny how the smallest things just dont sit right until its just so. Part of the DIY charm!:D

russellc
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When you can't control what you want to (driver matching) you control what you can (crossover components.

I know of two speakers which have crossover components matched to compensate for the actual drivers in the unit.
The original BBC LS3/5A used a tapped inductor and selected capacitance to set the HF level. The tolerances of the Kef T27 tweeters were outside the requirements of the speaker's response so this was necessary.
The Spica TC60 did the same thing but I'm unsure of the details. A dealer told me they had 6 different crossover versions and would select the one to match the actual drivers' response. Not sure of the details there.

Gotta pack a pair of Boston A200s and get them to Fed Ex, then I'm off to the hardware store for lumber for the next Econowave project.
 
Russellc said:
Thanks Zilch, good info on a good "Econo" woofer! several have used it as such, maybe now we can see a few more. That Dayton 12 inch looks good tofor only a little more....
Click to expand...
Augerpro just posted this map of the vertical nulls with an 8.44" center-to-center spacing, at 1.6 kHz crossover frequency, i.e., E'Wave with a 10" woofer, over on AVS Forum. If I'm reading it right, they're at +/- 28.8°, just outside our vertical beamwidth window, much as Wayne Parham recommended earlier in this thread:

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81/2" spacing with a 10" woofer is probably as tight as you can get, I'm guessing. Looks to be about 50 degrees? A beautiful graph.
 
The context of the nulls in the vertical beamwidth:

1) if you have a higher crossover frequency the angle of the nulls closes up and they begin to move into the window of usable beamwidth.

2) the same thing occurs if the center to center distance of the drivers increases.

The takeaway: keep your woofer and WG as close together as possible.

Note that the graph shown does not take into account time alignment of the signals. If the acoustic centers of the drivers are at significantly different depths the graph tips up or down, in the direction of the most delayed signal. In most cases for us, the compression driver is 'behind' the woofer's acoustic center, making the pattern tip 'upward'. This is useful for floor standing speakers and may keep the upper null out of the upper part of the window when the acoustic centers are farther than 8.44" apart.

Please correct me if I'm wrong on this...
 
On my new OLA conversion I'm angling to get the C-to-C distance down to 7" by back mounting the woofer and overlapping the frames. I just bought 3'4" Baltic birch to make the new baffles. I haven't touched a router in 10 years so the learning curve could be pretty comical.
 
Bauhausler said:
The context of the nulls in the vertical beamwidth:


Note that the graph shown does not take into account time alignment of the signals. If the acoustic centers of the drivers are at significantly different depths the graph tips up or down, in the direction of the most delayed signal. In most cases for us, the compression driver is 'behind' the woofer's acoustic center, making the pattern tip 'upward'. This is useful for floor standing speakers and may keep the upper null out of the upper part of the window when the acoustic centers are farther than 8.44" apart.

Please correct me if I'm wrong on this...
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I think your right, though the crossover induced phase delay affects this as well.

I don't know how that graph was made, but if it is accurate in terms of being a measurement, the forward axis looks straight ahead. It does look very tidy for being measured, though.... Gonna go over to the other site and get background on how it was done.
 
skywave-rider said:
I think your right, though the crossover induced phase delay affects this as well.

I don't know how that graph was made, but if it is accurate in terms of being a measurement, the forward axis looks straight ahead. It does look very tidy for being measured, though.... Gonna go over to the other site and get background on how it was done.
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The graph is undoubtedly generated mathematically.

It's good to have a graphical representation of this that's more comprehensible than the Arcsin calculation Wayne gave us. I don't think it's something to obsess over as long as the drivers are as close as possible.

Note also that the big 'lobe' at the left is actually the useful window of the WG at this frequency. (physically) above and below the lobe the WG's response falls off and the full level shown on the graph is not present.
 
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skywave-rider said:
81/2" spacing with a 10" woofer is probably as tight as you can get, I'm guessing. Looks to be about 50 degrees? A beautiful graph.
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"Squircle" 10" will get closer, and spread the nulls a bit further.

skywave-rider said:
I don't know how that graph was made, but if it is accurate in terms of being a measurement, the forward axis looks straight ahead. It does look very tidy for being measured, though....
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It's a sim, mostly useful for illustrating the concept.

skywave-rider said:
Where is this happening?
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It isn't yet. I'm thinking Dynaco A25 maybe, but haven't checked. It'll probably fit in Control 1, but those are new, and I'm not messing with 'em.

Folks jokingly suggest I have an E'Wave for everything. Well, no, but it's getting closer. Presidians have just moved onto the list, maybe.... ;)
 
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Zilch said:
It's a sim, mostly useful for illustrating the concept.

It isn't yet. I'm thinking Dynaco A25 maybe, but haven't checked. It'll probably fit in Control 1, but those are new, and I'm not messing with 'em.

Folks jokingly suggest I have an E'Wave for everything. Well, no, but it's getting closer. Presidians have just moved onto the list, maybe.... ;)
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I have a pair of kinda whipped Control 1s from a pawn shop...
 
The Control 1 looks a lot like the proIII, I have one orphan example of the 'III. A not-bad nearfield monitor but I think the AR wedges are better.
YMMV
 
Zilch said:
It isn't yet. I'm thinking Dynaco A25 maybe, but haven't checked. It'll probably fit in Control 1, but those are new, and I'm not messing with 'em.

Folks jokingly suggest I have an E'Wave for everything. Well, no, but it's getting closer. Presidians have just moved onto the list, maybe.... ;)
Click to expand...

When I saw those I immediately thought, "E'Wave supertweeter."
15k and above, whether audible or not.
:p:
 
Zilch said:
"Squircle" 10" will get closer, and spread the nulls a bit further.

It's a sim, mostly useful for illustrating the concept.

It isn't yet. I'm thinking Dynaco A25 maybe, but haven't checked. It'll probably fit in Control 1, but those are new, and I'm not messing with 'em.

Folks jokingly suggest I have an E'Wave for everything. Well, no, but it's getting closer. Presidians have just moved onto the list, maybe.... ;)
Click to expand...

That just reminded me that I have A25s in the closet as well. I don't have to be listening to these HPM100s that happened to be sitting here when I took the main system apart for a minute.
Actually I've sorta been collecting mini speakers lately. The Control 1s, Minimus 7s, Minimus 77s, some kind of nice Nakamichi 2-ways and most interestingly, Fried Model R's. These are LS3/5A sized cabinets with T27 and B110 in them. I like the B110 but not the T27. The cab is too small to jam a conventional compression driver inside, so I'd love to find a different WG and driver for these. Mind you, that's 9th or 10th on my projects list, but I am curious about that little tweeter thingy Zilch shows on the Minimus in the pic. Quit teasing!

BTW, My PH612 WGs from Pants Excess were delivered today, so they're filling back orders on those now.
 
Bauhausler said:
When you can't control what you want to (driver matching) you control what you can (crossover components.

I know of two speakers which have crossover components matched to compensate for the actual drivers in the unit.
The original BBC LS3/5A used a tapped inductor and selected capacitance to set the HF level. The tolerances of the Kef T27 tweeters were outside the requirements of the speaker's response so this was necessary.
The Spica TC60 did the same thing but I'm unsure of the details. A dealer told me they had 6 different crossover versions and would select the one to match the actual drivers' response. Not sure of the details there.

Gotta pack a pair of Boston A200s and get them to Fed Ex, then I'm off to the hardware store for lumber for the next Econowave project.
Click to expand...

The LS35A, I always wanted a pair of those back when mini monitors were first big. Havent heard one in over 10 years!

russellc
 
Zilch said:
Augerpro just posted this map of the vertical nulls with an 8.44" center-to-center spacing, at 1.6 kHz crossover frequency, i.e., E'Wave with a 10" woofer, over on AVS Forum. If I'm reading it right, they're at +/- 28.8°, just outside our vertical beamwidth window, much as Wayne Parham recommended earlier in this thread:

attachment.php
Click to expand...

Another valueable graph demonstrating great performance from a truely "econo" woofer. Thanks for showing this, I dont get over to that forum, at least not yet.

russellc
 
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