Zilch's AK Design Collaborative - Econowave Speaker

[Wayne Parham]

You won't need top-octave compensation with the tractrix horn (or at least not as much) because it has collapsing directivity which provides acoustic EQ on-axis. In practice, I find a little electrical EQ still sounds good because the horns with collapsing DI tend to provide less acoustic EQ than needed. Then again, this depends on the driver. If you use the Selenium many people use here, I expect it would sound best with no electrical EQ at all on a tractrix horn. If you use something like the JBL 2426, I'd probably use 4-6dB.

The RRC network is really intended for constant directivity horns where the on-axis response (as well as anywhere else in the pattern) tracks the power response of the driver. The network does three things:

1. It provides SPL level matching for the woofer and tweeter
2. It provides 6dB/octave rising response at frequencies above mass rolloff
3. It allows specific damping (Q) to be set in the core splitter filter, to set the "shelf" level between crossover and the beginning of mass rolloff

Since the Econowave design approach is so similar to my own, I think a co-mingling of design ideas is natural, almost implied. I've been doing this a long, long time so maybe some of the things written over the years in my Pi Speakers forum (and/or AudioRoundTable.com) would be useful here. One can certainly do a search there but as a sort of truncated quick reference, here are a handful of posts you might find useful, in chronological order:

• Pi horn design philosophies
• Crossovers.................
• Extended High End on Compression Drivers
• JBL specifications documents and whitepapers
• Clarification of attenuation values
• Two-way system
• Matching directivity in the vertical and the horizontal planes
• Imaging, placement and orientation
• My personal opinions of various design philosophies
• Crossover optimization for DI-matched two-way speakers
• Constant directivity, compression drivers and crossovers

 

[doucanoe]

You won't need top-octave compensation with the tractrix horn (or at least not as much) because it has collapsing directivity which provides acoustic EQ on-axis. In practice, I find a little electrical EQ still sounds good because the horns with collapsing DI tend to provide less acoustic EQ than needed. Then again, this depends on the driver. If you use the Selenium many people use here, I expect it would sound best with no electrical EQ at all on a tractrix horn. If you use something like the JBL 2426, I'd probably use 4-6dB.

The RRC network is really intended for constant directivity horns where the on-axis response (as well as anywhere else in the pattern) tracks the power response of the driver. The network does three things:

1. It provides SPL level matching for the woofer and tweeter
2. It provides 6dB/octave rising response at frequencies above mass rolloff
3. It allows specific damping (Q) to be set in the core splitter filter, to set the "shelf" level between crossover and the beginning of mass rolloff

Since the Econowave design approach is so similar to my own, I think a co-mingling of design ideas is natural, almost implied. I've been doing this a long, long time so maybe some of the things written over the years in my Pi Speakers forum (and/or AudioRoundTable.com) would be useful here. One can certainly do a search there but as a sort of truncated quick reference, here are a handful of posts you might find useful, in chronological order:

• Pi horn design philosophies
• Crossovers.................
• Extended High End on Compression Drivers
• JBL specifications documents and whitepapers
• Clarification of attenuation values
• Two-way system
• Matching directivity in the vertical and the horizontal planes
• Imaging, placement and orientation
• Crossover optimization for DI-matched two-way speakers
• Constant directivity, compression drivers and crossovers

Excellent, Thanks!


I would really like to go with a pair of the 2 bolt Selenium's or B&C DE 250's but have not made the move yet. For the time being, I have a pair of 2425's that will have to do for the time being.

I guess I am going to have to follow along with your findings and try out a few things. I'm not using any EQ on my 350Hz round Tractrix/ JBL 2441 and finding that it works very well. Sounds like I might find the same to be true with the 650's and Selenium or B&C. Not sure what to make of the 2425's yet.

RC

 

[dokblues]

A little help here gentelmen, I have a nice pair of nla`s with the rounded bullnose and I would like to do the tweeter replacement. Point a speaker rebuild newbie in the right direction.

 

[Russellc]

A little help here gentelmen, I have a nice pair of nla`s with the rounded bullnose and I would like to do the tweeter replacement. Point a speaker rebuild newbie in the right direction.

Bauhausler is your man for the Advent conversion. There's been a lot of them and they are very popular. Only thing its missing is the really high efficiency aspect. Plenty efficient enough, bass is strong, and the CD HF is outstanding as well. Have fun. I think about all you have to do is shave and 1/8 of an inch off each side of the wave guide and enlarge the hole.( in the baffle, not the waveguide) Mr. B will be along soon I'm sure. He may have a seperate thread as well?

Russellc

 

[Zilch]

A little help here gentelmen, I have a nice pair of nla`s with the rounded bullnose and I would like to do the tweeter replacement. Point a speaker rebuild newbie in the right direction.

http://www.audiokarma.org/forums/showthread.php?p=2627645#post2627645

If you click on the project links from Post #1, you'll see several completed projects built from Large Advents, and there is also a tutorial by the Bauhausler linked there. It's a slam dunk using the standard crossover.

With the bullnose NLA, the only issue is that the waveguide is a smidge wide for the baffle. There are several approaches to that, including undercutting the moulding at the waveguide location, but most have favored shaving a small amout of material off the sides of the waveguide such that it fits nicely in the available width.... :thmbsp:

340005/6813=49.9121​

 

[rage]

I have a few more questions for you guys!

I've been running my 10" dayton classics in my JBL l26 cabs with zilch plugs and the < 95db crossover. So far I'm pretty happy, they sound very nice.

I'm working on moving things over to my Barzilay cabs.

Earlier there was talk of me using 2 10" dayton classic woofers per cab. These cabs measure 4.27 cu ft, and I've been using 4.5 cu ft in my toying around with WinISD.

I noticed with a ported setup there is a large hump that seems to go wherever I tune the enclosure for. Tuning for 20hz brings that hump down to 20 hz and I have 6-7db bump there. Is this audible? What can I do to fix this? Tuning much higher puts the bump at around 30 hz, which I would think would be worse.

Lastly, I don't seem to have enough room for the 2 dayton classics and the e-wave on the baffle. I might have to mount the waveguide on top. This isn't a serious issue...but brings me to another question.

I can get about 95db effeciency if I put 4 dayton classics in each cab. Is this stupid?

How will this affect the overall sound? Will it throw off the dispersion of the mid frequencies?

Is there a diminishing point of returns when adding more woofers for higher sensitivity? I know it can increase power handling, or at least I think I know.

I may just install the 1 dayton classic + ewave in the Barzilays and fool around with that for a while, I'm really not certain.

 

[Zilch]

I can get about 95db effeciency if I put 4 dayton classics in each cab. Is this stupid?

Generally speaking, using multiple woofers is not a good idea unless you understand the tradeoffs and do it to achieve a specific design objective. Multiple drivers playing the same program material interfere with each other in a complex fashion which is difficult to manage. In most instances where that is done, the woofers are not both playing the same frequency range.

Try some other single woofers; there are plenty of worthy 12"ers others have used here, and LE14A looms large for installation in Barzilays, as well. If you want high efficiency, use high-efficiency woofers and plan on augmenting with sub(s).... :thmbsp:

 

[GordonW]

Earlier there was talk of me using 2 10" dayton classic woofers per cab. These cabs measure 4.27 cu ft, and I've been using 4.5 cu ft in my toying around with WinISD.

I noticed with a ported setup there is a large hump that seems to go wherever I tune the enclosure for. Tuning for 20hz brings that hump down to 20 hz and I have 6-7db bump there. Is this audible? What can I do to fix this? Tuning much higher puts the bump at around 30 hz, which I would think would be worse.

That doesn't make sense. Here's what I get, modeling the Dayton 10" woofers in about 2.2 ft^3 each (4.4 ft^3 for two)

:

No big hump... f3 of around 38-39 Hz. IME, it actually goes lower than that, in-room.

Regards,
Gordon.

 

[rage]

I'll recheck stuff, maybe I entered something wrong.

So being that both 10" woofers would play the same frequencies, that is also a bad idea?

When modeling with 2 drivers you don't use the multiple driver option in Winisd, you just divide the volume by the number of drivers?

Thanks guys, sorry for the dumb questions...

 

[dokblues]

Thanks for the link to the correct page Zilch! I`m on my way to being an ewaver. :wave:

 

[Zilch]

Thanks for the link to the correct page Zilch! I`m on my way to being an ewaver. :wave:

COOL! Let the fun BEGIN!

Here's the tutorial:

http://audiokarma.org/forums/showthread.php?t=196614

And the crossover video starring AK's own Wiredbecker:

http://www.youtube.com/watch?v=lw7pTwpx0K0

 

[borus]

Hi All
Did a LOGO ever get decided on for the Ewave? It was discussed but I cannot find a final version. Or am I way off here and none were proposed?

Thanks Borus

 

[GordonW]

I'll recheck stuff, maybe I entered something wrong.

So being that both 10" woofers would play the same frequencies, that is also a bad idea?

When modeling with 2 drivers you don't use the multiple driver option in Winisd, you just divide the volume by the number of drivers?

Thanks guys, sorry for the dumb questions...

Both drivers playing the same range? Maybe, maybe not. With the relatively low crossover point of the E-wave, it might work with them in parallel. The Dayton 10s do NOT have a rising response (in fact, it slightly falls with frequency), so you may need both of them playing up to the same crossover point, to make sure you don't generate a dip in the midrange frequency response.

As for modeling multiple drivers in WinISD... yes, you can just divide the cabinet volume by the number of drivers. It's absolutely equivalent. I just automatically do that out of habit... I've never used the multiple driver option.

Regards,
Gordon.

 

[Bauhausler]

A little help here gentelmen, I have a nice pair of nla`s with the rounded bullnose and I would like to do the tweeter replacement. Point a speaker rebuild newbie in the right direction.

I've built 2 finished pairs of ewaved Advents and done a number of experiments. The standard low efficiency crossover with teh PH612/D220Ti works beautifully.
The NLA cabinet is pretty narrow for the waveguide. You either have to cut a relief under the rim for the edge of the waveguide or trim about 3/8" off the waveguide to get it to fit. Trimming the waveguide is easiest.
If your woofers need re-foaming make sure you use the right foam. The standard cheap foam sold for Advents is too stiff and will alter the performance. You could buy a correct kit and do it yourself or send them to a pro. Audio Atlanta comes to mind.
You'll love the sound with the waveguide. It completely transforms the speaker. The last pair that I built replaced a pair of JBL Barons and the owner is very pleased.

A related thread:
http://audiokarma.org/forums/showthread.php?t=196614

 

[Russellc]

Here 'tis:

• Compensation component values

Might be useful to link my Crossover Document too, because that's what the E-Wave crossover is based on. It shows various network topologies used in speakers like these and compares them using Spice. I've seen it posted in this thread too, way back when Jack and Zilch were first ironing out the E-Wave crossover. But it's probably pretty much lost in the archives.

I think my Crossover Document is useful not only as a study in various network arrangements but also for historical perspective, because it shows how and why I came up with the RRC approach for constant directivity horns. Prior to that, passive crossovers for CD horns were much more complex, using transformers, peaking coils and/or other LRC approaches to obtain the desired transfer function. I pioneered the RRC approach that's now used in the E-Wave crossover and other similar designs (including my own, of course).

Thanks Wayne, you popped out just like Bat Man! Thanks for the link!:yes:

Russellc

 

[Russellc]

Zilch , or anyone, looking at the comp filter values, could you say that R1- 20 ohms, R2- 16 ohms and C - 0.47uf is equal to 11db.

Yes according to Wayne's chart, you are somewhere between 10 and 12 db, so I'd say 11 would be a fair accessment of the circuit you suggest.

Russellc

 

[Russellc]

Hi All
Did a LOGO ever get decided on for the Ewave? It was discussed but I cannot find a final version. Or am I way off here and none were proposed?

Thanks Borus

I remember some talk here and on the Indignia thread, or was it all there? Not a bad Idea, with official E'waver number of the project.

Russellc

 

[rlee777]

My first Econowave project -- Q on Zobel

This amazing thread inspired me to try this project. Using a pair of Selenium 12" woofers, I am considering adding Zobel imp compensation to the base crossover to help counteract the rising response from 1Khz to 2.5Khz and help the crossover become more effective on the woofer end.

Any thoughts? Has someone tried Zobels with pro woofers in this type of application?

 

[Bauhausler]

This amazing thread inspired me to try this project. Using a pair of Selenium 12" woofers, I am considering adding Zobel imp compensation to the base crossover to help counteract the rising response from 1Khz to 2.5Khz and help the crossover become more effective on the woofer end.

Any thoughts? Has someone tried Zobels with pro woofers in this type of application?

The Zobel might not be necessary if using the Econowave crossover specified. The Econowave electrical lowpass is 1200 hz, which could keep your woofer out of trouble at the top end of its range.
The standard answer is to try it and see. It's easy enough to connect leads to the woofer terminals, run them outside the cabinet and experimentally connect and disconnect the Zobel to see if it's helpful.

 

[Wayne Parham]

Not to be a contrarian, but I would always use a Zobel on a woofer fed from a passive low-pass filter of second-order or higher. There are some weird exceptions, like when using one of those AE woofers that are nearly resistive. Or maybe if the woofer doesn't reach high enough and you're trying to eek out some top end from a driver that is sagging up high using filter peaking (not recommended). But in general, you'll want a Zobel. Without one, the low-pass filter usually "sees" too high an impedance because of voice coil inductance. This causes it to be underdamped around crossover, resulting in a peak, sometimes a pretty big one.

I know it sounds somewhat counterintuitive, but the truth is the higher frequency crossovers usually suffer this problem more than lower frequency ones do. It seems like if you crossover real high, you're moving out of the passband, like you said "keeping out of trouble." But in reality what is happening is the voice coil inductance is rising higher and higher as frequency goes up. Each woofer is different, but a typical woofer may be 8Ω at 200Hz, at 500Hz it is probably closer to 10Ω and by the crossover frequency, it has risen to probably 16Ω. So the low-pass filter is probably underdamped without a Zobel. You could design the woofer crossover for a 16Ω load, I suppose, but that will alter the transfer function (amplitude and phase) in other ways. The point is that the load impedance changes with frequency, so an impedance conjugate filter (Zobel) makes sense.

• Crossover Electronics 101
• Speaker Crossover Document

Check out the handouts from the "Crossover Electronics 101" seminar, which is like a condensed form of the Speaker Crossover Document. The handouts and the crossover document both show various passive networks along with Spice models and their associated transfer functions. At the seminar I do each year, we discuss these and then connect a speaker through an actual physical circuit for each network shown. You can really hear the peaking shown in the Spice models, making it possible to identify what various response curve features actually sound like.