Zilch's AK Design Collaborative - Econowave Speaker
- Thread starter Zilch
- Start date
Geddes will sell you a chunk of it for $10, as I recall.
It may be possible to shape it with hot wire techniques.
The guys making retro Quadrex grilles for L100s know how to do it, but they're not telling....
That certainly sounds more like the Geddes we ALSO know and love....
:
skywave-rider
Slumming in Akihabara
Now that we're tracing contours, I may be skilled-out of the proceedings.
A foam bullet in a funnel seems easier to fabricate than an undulating, curvaceous waveguide filler.
We'll see.
A foam bullet in a funnel seems easier to fabricate than an undulating, curvaceous waveguide filler.
We'll see.
skywave-rider
Slumming in Akihabara
Compared to a PT Waveguide, an Altec sectoral is real easy to stuff foam into....
Edit: sorry, not disparaging Altec horns. The foam may just dampen ringing everybody complains about.
dnewma04
The Healer
That certainly sounds more like the Geddes we ALSO know and love....
I think he had to buy a gigantic chunk of foam that he would cutaway as needed. If you've priced out one of these things, you'd probably be scared to see what kind of price tag they have (thousands). A chunk big enough to fill one of his WGs is pretty significant. Still, the price was high compared to what I found, and especially with the price Ross found at 15.00 cheaper.
Bauhausler
Rational Subjectivist
Dang! I had a pair of C36 that came with LE14A (on an adapter plate) and LE20 in them. Didn't care for that tweeter at all. Long gone, though.
As an experiment I want try the Ewave on top of my friend's C38 Barons with D130.
As an experiment I want try the Ewave on top of my friend's C38 Barons with D130.
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skywave-rider
Slumming in Akihabara
Just beautiful and I'm jealous.
OK, I will preempt any stupid posts by staying quiet for a while....
...A chunk big enough to fill one of his WGs is pretty significant. Still, the price was high compared to what I found, and especially with the price Ross found at 15.00 cheaper.
Petroleum product. Good deal Ross.
The very first EconoWaves were built by AKer Mxlews in C36s:
http://audiokarma.org/forums/showthread.php?t=107477
Four or five of us have built or are building with them now. The factory cabs seem all to have permanent baffles, which must be replaced. This driver set just fits.
Plans to build them from scratch with removable baffles are here:
http://www.lansingheritage.org/images/jbl/plans/c35-c39/page2.jpg
I'm tryin' to figure an easy way to get a bit of upward tilt on the waveguide, as they do sit low, and also a CNC shop to make the legs, now that I have a drawing for those.
Another member is doing Valencias with tilted waveguides. I'm not sure what Jack's planning for his Sevilles, but they have the same issue. If anyone can come up with a clever solution, it's our own pre-eminent E'wave cab adapter Jackgiff.... :yes:
This project is really fun and these C36's are going to sound amazing!
Wayne Parham
Active Member
Measurements verses listening impressions
Every time I measure a horn that sounds bad - and I mean every time - there is an obvious anomaly, easily measured.
When you see response charts that are smoothed, they hide a world of nasties. So you can definitely hear stuff that doesn't show on a smoothed chart. But an unsmoothed chart is a different story. It shows every tiny little detail, and you can see it in either time domain or frequency domain representations.
Most horns have ripples in response, and almost all show the first couple of quarter wave resonance nodes at the bottom end. Ripples and spikes above that show reflections, diffraction and other anomalies like that. The reactive nature of the horn interacts with passive components in the crossover, sometimes that makes peaks too. All these things are very visible in high-resolution response measurements of horns, truly all speakers for that matter.
I have found that I can easily hear things that don't show up in a response chart smoothed 1/3 octave. Anomalies that are smoothed with 1/6 octave resolution are also audible. But when I look at a chart that has not been post processed at all, the machine is able to detect subtle details that are completely inaudible, way below the threshold of human detectability. I'm not sure where the threshold resolution is, but I'm guessing it is probably around 1/12th octave. That's about a one note resolution on the chromatic scale. I know I can hear anomalies that are too fine to show up in a chart made at 1/6th octave resolution, but some tiny little details that show up in an unsmoothed chart are inaudible.
High order modes are non-axial sounds that reflect off a boundary, making an early reflection that is delayed in time. Reflections of this sort show up directly in the time domain and they cause self-interference that manifest themselves in the frequency domain. You can see delayed signals in the step and impulse response, self-interference from the same cause blips in the frequency response. But these are pretty small anomalies, seen only the unsmoothed charts of a system measured with relatively high resolution.
Why then, would anyone seeking to show performance improvements in these areas use smoothed response charts as evidence? Smoothing removes all the details one would hope to see. I'm not saying smoothed response charts are necessarily bad - they show an average sound distribution, a spectral balance. That's meaningful. It reduces noise and shows an overall trend. But if you're trying to demonstrate subtle details, reduction of non-axial reflections and edge diffraction, the best way to see them is with a high resolution chart. In truth, probably the only way to see these things is with high resolution measurements.
So that brings me back to the point. I don't think it is difficult to hear anomalies that are completely invisible in a measurement that has been smoothed to 1/3 or even 1/6 octave resolution. But that doesn't mean you can hear things you can't measure. Maybe you can, maybe you can't. The first thing to do is to measure with high enough resolution, to examine the DUT with adequately high resolution rather than smoothed to 1/3 octave. Comparison with other devices should also be done at equally high resolution. I know for me, there has never been an audible anomaly I couldn't easily find with a good measurement system. The key is to look at the details rather than to mask them out with smoothing.
Every time I measure a horn that sounds bad - and I mean every time - there is an obvious anomaly, easily measured.
When you see response charts that are smoothed, they hide a world of nasties. So you can definitely hear stuff that doesn't show on a smoothed chart. But an unsmoothed chart is a different story. It shows every tiny little detail, and you can see it in either time domain or frequency domain representations.
Most horns have ripples in response, and almost all show the first couple of quarter wave resonance nodes at the bottom end. Ripples and spikes above that show reflections, diffraction and other anomalies like that. The reactive nature of the horn interacts with passive components in the crossover, sometimes that makes peaks too. All these things are very visible in high-resolution response measurements of horns, truly all speakers for that matter.
I have found that I can easily hear things that don't show up in a response chart smoothed 1/3 octave. Anomalies that are smoothed with 1/6 octave resolution are also audible. But when I look at a chart that has not been post processed at all, the machine is able to detect subtle details that are completely inaudible, way below the threshold of human detectability. I'm not sure where the threshold resolution is, but I'm guessing it is probably around 1/12th octave. That's about a one note resolution on the chromatic scale. I know I can hear anomalies that are too fine to show up in a chart made at 1/6th octave resolution, but some tiny little details that show up in an unsmoothed chart are inaudible.
High order modes are non-axial sounds that reflect off a boundary, making an early reflection that is delayed in time. Reflections of this sort show up directly in the time domain and they cause self-interference that manifest themselves in the frequency domain. You can see delayed signals in the step and impulse response, self-interference from the same cause blips in the frequency response. But these are pretty small anomalies, seen only the unsmoothed charts of a system measured with relatively high resolution.
Why then, would anyone seeking to show performance improvements in these areas use smoothed response charts as evidence? Smoothing removes all the details one would hope to see. I'm not saying smoothed response charts are necessarily bad - they show an average sound distribution, a spectral balance. That's meaningful. It reduces noise and shows an overall trend. But if you're trying to demonstrate subtle details, reduction of non-axial reflections and edge diffraction, the best way to see them is with a high resolution chart. In truth, probably the only way to see these things is with high resolution measurements.
So that brings me back to the point. I don't think it is difficult to hear anomalies that are completely invisible in a measurement that has been smoothed to 1/3 or even 1/6 octave resolution. But that doesn't mean you can hear things you can't measure. Maybe you can, maybe you can't. The first thing to do is to measure with high enough resolution, to examine the DUT with adequately high resolution rather than smoothed to 1/3 octave. Comparison with other devices should also be done at equally high resolution. I know for me, there has never been an audible anomaly I couldn't easily find with a good measurement system. The key is to look at the details rather than to mask them out with smoothing.
Russellc
Addicted Member
Its a bit over my head, but how do we know if its "smoothed response or not? I have been planning on getting one of the Behringer DEQ 2496 soon, it has been used successfully here by several. Is it a "smoothing" type?
What measuring equipment (if any exists) would you recommend that is average guy affordable? I and others would certainly appreciate your input here!
Thanks for your time,
Russellc
The way I read Wayne's discussion, he's sorta intermixing the concepts of "resolution" and "averaging". My definition of resolution: The smallest increment of the variable bring measured that can be reliably "displayed". In the case of RTA measurements under discussion, the resolution in the frequency domain would be 1/3rd octave, 1/6th octave etc. In the amplitude domain it would typically be dB.
To me at least, "smoothing" would be the process of "averaging" over time, multiple measurements of a variable that can vary somewhat over time to produce a more repeatable "display".
Overall, I think Wayne's saying that the typical 1/3 or 1/6 octave RTA lacks the frequency domain resolution to show the sharp or high Q resonances that the ear readily detects. He also seems to be saying that 1/12th octave resolution is necessary to match the sensitivity of the ear. The DEQ2496 is 1/6 octave at best so I assume it doesn't meet his criteria for reliable correlation betw measurement and audibility.
Be interesting to get further insights on this from the man himself.
Wayne Parham
Active Member
Resolution
I have mentioned averaging and resolution somewhat interchangeably. They're not the same thing, but they are similar. If you measure with high resolution, both in sampling rate and in amplitude, and then post-process down to 1/3 octave resolution, the data you see is averaged down enough you can't see details. That's the point, if you can't view the data in sufficient detail, naturally you can hear things you can't see.
Part of the reason I wasn't more specific about pre-processing verses post-processing resolution is there are times when high sampling rates yield low data resolution. It depends on the measurement process, sampling method and signal type. The other part is it wasn't really germane, the whole point is data resolution, not sampling resolution.
Most times, response charts are published with the sampling rates and post-processed smoothing listed. So look for that information accompanying the chart. If it isn't shown, assume 1/3 octave or more smoothing has been applied. That is not unusual.
Again, smoothing isn't necessarily bad. It removes noise, showing spectral balance and overall trends. But be careful when comparing charts because one that has been smoothed more than another will naturally look better. And if you're looking for small details, especially things like diffraction effects and high-order modes, I think smoothed charts are probably worthless because they remove all detail from the graphs.
I have mentioned averaging and resolution somewhat interchangeably. They're not the same thing, but they are similar. If you measure with high resolution, both in sampling rate and in amplitude, and then post-process down to 1/3 octave resolution, the data you see is averaged down enough you can't see details. That's the point, if you can't view the data in sufficient detail, naturally you can hear things you can't see.
Part of the reason I wasn't more specific about pre-processing verses post-processing resolution is there are times when high sampling rates yield low data resolution. It depends on the measurement process, sampling method and signal type. The other part is it wasn't really germane, the whole point is data resolution, not sampling resolution.
Most times, response charts are published with the sampling rates and post-processed smoothing listed. So look for that information accompanying the chart. If it isn't shown, assume 1/3 octave or more smoothing has been applied. That is not unusual.
Again, smoothing isn't necessarily bad. It removes noise, showing spectral balance and overall trends. But be careful when comparing charts because one that has been smoothed more than another will naturally look better. And if you're looking for small details, especially things like diffraction effects and high-order modes, I think smoothed charts are probably worthless because they remove all detail from the graphs.
skywave-rider
Slumming in Akihabara
Steve, Using the DEQ2496, I've never been able to see the 19kHz spike produced by the BMS drivers we have. Being a DEQ owner I assume you have the same experience. I've relied on Zilch's measurements to see that. I never thought I'd be able to see HOMs or horn resonances with that unit. Having said that, for me, it's been a great piece of gear and very useful.
Planning to move up to SoundEasy when I can, and I hope it can measure with appropriate data resolution.
Thanks, Wayne.
