Zilch's AK Design Collaborative - Econowave Speaker
- Thread starter Zilch
- Start date
Not pretty, but sounding good. The 123A-1 woofers are in the L112's right now since the 128H's need new foam. The L100 cabinets were banished to the garage due to lack of space in the mancave.
I'll attach a sweep of just the woofer and you'll see that spike just below 2K. That's at 1/24th octave, but it's still wide enough and has enough amplitude to be audible. I ended up with a 2mH and 20uF for the low pass just by playing with different combinations, listening and running sweeps and pink noise on the RTA. I was playing with a Zobel network, but everything I tried seemed to suck out the glorious midrange. I noticed you used a 6 ohm/30uF at one point. Is the 123A-1 considered a 6 ohm woofer? Mine measures 4.4 ohms but I had assumed these were treated as 8 ohm units.
I'll attach a sweep of just the woofer and you'll see that spike just below 2K. That's at 1/24th octave, but it's still wide enough and has enough amplitude to be audible. I ended up with a 2mH and 20uF for the low pass just by playing with different combinations, listening and running sweeps and pink noise on the RTA. I was playing with a Zobel network, but everything I tried seemed to suck out the glorious midrange. I noticed you used a 6 ohm/30uF at one point. Is the 123A-1 considered a 6 ohm woofer? Mine measures 4.4 ohms but I had assumed these were treated as 8 ohm units.
Attachments
If you throw the dimensions of that enclosed area just above the woofer, where it says "12x12 opening", into a calculator you get right at 3cuft. So if that 12x12 opening wasn't there and you did cut it out then you'd add that 3cuft. Wonder if there were versions with the cutout and without.
Note: I seem to recall Dennis turning his cabs upside down so just above in the drawing would be just below in his.
Ray
Hi Ray, just to be clear, I am talking about cutting a 12" x 12" hole on the horizontal board betweet the two chambers but still leaving the 12" x 12" opening on the back sealed off. Yep they are up side down in the pic I posted, so the dead chamber is below the woof chamber. I am not sure how much good it will do, but Steve said it will dramatically lower the bass. They did not make an open or closed version. The Jensen woofer was tuned to this cab or the other way around. It is supposed to have slamming bass just as it was designed. Cheers.
You have to measure the impedance of the driver at the filter frequency to know what it actually is.
I've done impedance flattening determinations empirically with 123A-1, and came up with some outlandish values. HOWEVER, as with all filter designs, it's the ACOUSTIC response that matters, and what we know as a Zobel is, in the larger sense, a filter element of broader utility than merely impedance conjugation. It doesn't have to be textbook for optimal performance, and in fact, rarely is.
That's a fairly high-Q spike there, and you may be able to mitigate it somewhat via tweaking the lowpass and conjugate values. However, before I got too deeply into that, I believe I'd first verify it is present in all of the 123A-1s, i.e., characteristic of the driver design.
Also, you're connected to the woofer terminals directly, right? I mean the internal L112 filters are disconnected completely?
That's a nice RTA frequency response you're showing there, and your mancave HT setup certainly looks E'Wave cool! :thmbsp:
If it was built according to the linked drawing, there is no 3 cuft. dead chamber; I believe Ray has just confirmed my interpretation.
When you say "horizontal," if you're referring to the area where the horn and tweeter are normally mounted, then cutting into that would be a mistake. It's the exit, and already communicates with the rear chamber.
It's a rear-loaded folded horn, NOT a reflex, according to the description, and you're not going to get big or deep bass out of it....
Kegger
R.I.P. 1/12/1966 - 6/1/2017
Try using a much smaller cap on the Zobel, like say 10-15uf, an try resistors from
say 8-15 ohm, like Zilch says text book values rarely are where you'd end up, and
a Zobel is a filter network along with impeadance compensation, to large a cap will
kill the mids as you've found out, then the resistor sets the amount of attenuation.
This is the one area that really got my HPM woofers to perform at there best when
I finally dialed in the correct combo, and I believe impeadence had little to do with it.
Russellc
Addicted Member
Thanks, Zilch and Russellc,
I've also got a set of the bigger woofer cabinets, too - the 4508s w/dual 2225s wired for 4 ohms. Those ought to do the job as well.
Russellc, I see we also have some similar amps in the Mac stuff.
Cheers,
David
Wow, dual 2235H would be very powerful. I like the 2225H as it has great punch, two of them would be great as well. This is a great project, you'll love it!:thmbsp:
Russellc
But from what Dennis said, that compartment is sealed.
If that's the chamber is question then there may be some coincidental weirdness going on. By opening up the chamber I referenced as shown in the drawing you'd be creating an acoustic notch filter which might eat up some midrange and give the appearance of more bass.
Just guessing here of course as I wasn't privy to the original design.
Ray
Hi Ray, the hole betweet chambers needs to be large enough so the two will act as one. It is worth a try. I can also reseal the hole if indeed you are right. All I know now is that for a cab that is known for it's deep and rich bass, both high and low, it is not performing to spec. I am getting better bass out of my ESS EWG.
Hey Z, here is a pic of the cab as is and a pic of the drawing with the two chambers marked. The woofer chamber has the horizontal lines and the dead air chamber has the vertical lines. What Steve is saying is to essentially knock out the internal horizontal divider board between them. As far as stuffing is concerned, When I built foilded voights for my daughter, all the plans called for stuffing in the back chamber. The existing door on the dead air chamber always remain closed and the crossovers are mounted to it so they are inside the dead air chamber. Cheers.
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dnewma04
The Healer
Denny, is the area below the woofer open into the rest of the cabinet? It almost looks like the horizontal chunk of wood below the driver butts up against the baffle. If so, what you have is a very small sealed enclosure and the obvious reason behind the lack of bass. According to the drawing, there should be a gap which would allow the BLH concept to work. By opening up the top chamber, you'd be changing the properties of the horn. It's been a while since I've played with modeling BLHs, but I think increasing the driver chamber would give you a bit deeper bass with lower sensitivity.
If I get a chance, I'll try to figure it out.
If I get a chance, I'll try to figure it out.
The link Z posted above is a little easier to read. It shows a 2 3/4" opening between that chunk and the front baffle. I would think that would be the horn throat. By taking out the horizontal piece above (below in Dennis' world) the woofer you'd be making the compression chamber bigger by a pretty fair amount. Now if I remembered anything about horn design I could probaby make a guess at what that would do. Your guess of deeper with less efficiency sounds reasonable to me.
Ray
It certainly looks like the horn is compromised by the two openings. Does the text tell us they should be closed as apparently shown in the pics?
I can see needing the bottom one to mount the woofer, but why the smaller top one? For construction access?
Why would anything go through the throat if it had a 12" x 17" bypass path?
And the 12" x 12" one creates a resonance chamber in the bell?
[Where's Danley when we need him...?
]
I can see needing the bottom one to mount the woofer, but why the smaller top one? For construction access?
Why would anything go through the throat if it had a 12" x 17" bypass path?
And the 12" x 12" one creates a resonance chamber in the bell?
[Where's Danley when we need him...?
]
That's consistent with my present understanding of the design. You alter the size of the back chamber, and all bets are off without doing the calcs.
It's a folded rear-loaded horn. You're looking at it as if it were a reflex enclosure of equivalent dimension in defining your suppositions and expectations as to how it should perform. It's not that, and it don't play that, nope.
It has other sonic virtues, though. Use a sub, or rather, a minimum of three of them, according to those who know about the behavior of subs in rooms.... :thmbsp: