For anyone that's interested in waveguides, I've added a new page on my site that looks in detail at their performance.
Lots of experimental results and discussion. I think you'll find it interesting. Please check it out!
http://www.aeronet.com.au/waveguide.htm
Cheers, Ralph
Lots of experimental results and discussion. I think you'll find it interesting. Please check it out!
http://www.aeronet.com.au/waveguide.htm
Cheers, Ralph
I am seeing two tweeters suitable for experimentation, from pictures it looks like the Seas Millenium has a conical faceplate cutout that would couple well to a waveguide, can owners confirm? The other tweeter would be the Vifa XT25. Also, it looks like Scan-speak has some 20mm tweeters that look like they may have been designed for this. Thanks again for your research, I'm really hoping my friend can make me some waveguides to play with.
Excel/TDFC and probably others using that diaphragm don't really perform that well on waveguides (and I have tried a couple, including ones starting at the surround and with slight compression over the surround). The velocity profile above 6khz is seemingly just too variable to get results one could really call good.
One last question for you helpful people, how about a shallow, wide angle waveguide over a dome tweeter. For example, a 120 degree dispersion waveguide with only 0.5" to 0.75" depth. Would this shallow, wide dispersion waveguide be less likely to have horn coupling problems?
I am asking because I require minimal crossover modification if I use the same drivers (I left a space in the active crossover board for horn equalization), but would have to wait quite a while to experiment with ring radiators because of the cost of reprinting the crossover or buying a dcx.
I am asking because I require minimal crossover modification if I use the same drivers (I left a space in the active crossover board for horn equalization), but would have to wait quite a while to experiment with ring radiators because of the cost of reprinting the crossover or buying a dcx.
Ralph - good work! Nicely presented on your site, too.
I was doing a "horn survey" recently to see how the given cutoff frequency of known commercial horns compares to the width of the mouth opening. There seems to be a lot of variation, even among horns of the same brand.
My Altec 811 horns are said to be usable down to 800Hz - about 1 wavelength/mouth width. Just as you found with your waveguides. A lot of horns and wavegiudes give a much lower usable frequency. Wonder why the difference?
I suppose you have looked at the waveguides over on the DDS Site?
I was doing a "horn survey" recently to see how the given cutoff frequency of known commercial horns compares to the width of the mouth opening. There seems to be a lot of variation, even among horns of the same brand.
My Altec 811 horns are said to be usable down to 800Hz - about 1 wavelength/mouth width. Just as you found with your waveguides. A lot of horns and wavegiudes give a much lower usable frequency. Wonder why the difference?
I suppose you have looked at the waveguides over on the DDS Site?
Thanks for the support everyone!
-Mazurek,
The depth of a waveguide is determined by the other design parameters. The low frequency limit of pattern control sets the approximate mouth size, the driver diaphragm sets the mouth size, and the included angle determines the angle of radiation. The depth simply falls out of the geometric calculations. In gerneral waveguides are often very shallow, 15-30mm is common.
The issues due to throat termination persist no matter what the depth of the waveguide. Whether its 10mm deep or 50mm makes little or no difference at the throat.
Waveguide equalisation isn't difficult. The general characteristic of a waveguide loaded tweeter that has a flat response on a plain baffle is that the power response drops at approximately 6dB/oct over its range of waveguide operation. Correction is pretty well approximated with a single pole HPF network. Have a look at the paragraph called 'equalisation'.
-Panomaniac
I think there is a difference between cut-off frequency and the low frequency limit of pattern control. Horns are peculiar in that below their cut-off frequency no sound comes out! Waveguides on the other hand don't seem to take part in any acoustic impedance matching like a horn. Below its 'cut-off frequency' a waveguide ceases to exist, and the driver simply sees the baffle.
So in my statement of the limit of low frequency operation I meant the limit of pattern control.
Looking at the plot on my wavguide page of the exponential horn coupled to a compression driver, I would call the cutoff frequency to be 1.5kHz, but the limit of pattern control to be 3kHz. Conventional wisdom says that a horn shouldn't be used below one octave above its cut-off frequency, so two limits seem to be co-incident - at least in this case.
Cheers, Ralph
-Mazurek,
The depth of a waveguide is determined by the other design parameters. The low frequency limit of pattern control sets the approximate mouth size, the driver diaphragm sets the mouth size, and the included angle determines the angle of radiation. The depth simply falls out of the geometric calculations. In gerneral waveguides are often very shallow, 15-30mm is common.
The issues due to throat termination persist no matter what the depth of the waveguide. Whether its 10mm deep or 50mm makes little or no difference at the throat.
Waveguide equalisation isn't difficult. The general characteristic of a waveguide loaded tweeter that has a flat response on a plain baffle is that the power response drops at approximately 6dB/oct over its range of waveguide operation. Correction is pretty well approximated with a single pole HPF network. Have a look at the paragraph called 'equalisation'.
-Panomaniac
I think there is a difference between cut-off frequency and the low frequency limit of pattern control. Horns are peculiar in that below their cut-off frequency no sound comes out! Waveguides on the other hand don't seem to take part in any acoustic impedance matching like a horn. Below its 'cut-off frequency' a waveguide ceases to exist, and the driver simply sees the baffle.
So in my statement of the limit of low frequency operation I meant the limit of pattern control.
Looking at the plot on my wavguide page of the exponential horn coupled to a compression driver, I would call the cutoff frequency to be 1.5kHz, but the limit of pattern control to be 3kHz. Conventional wisdom says that a horn shouldn't be used below one octave above its cut-off frequency, so two limits seem to be co-incident - at least in this case.
Cheers, Ralph
FYI, Troels has put together an mtm using Vifa mids and a Monacor DT 300 tweeter. Of interest is the made-to fit waveguide Monacor provides for the DT 300.
http://www.troelsgravesen.dk/C17_II.htm
http://www.audiophonics.fr/monacor-....html?osCsid=355b96595552af7f5f9762615273291f
I'm not affiliated, just very interested.
http://www.troelsgravesen.dk/C17_II.htm
http://www.audiophonics.fr/monacor-....html?osCsid=355b96595552af7f5f9762615273291f
I'm not affiliated, just very interested.
Hi Ralph,
My brief search has not turned up a US source for Monacor. I'd like to try them also...but the wish list is a long one.
I admire the work Troels does...and his presentation.
Research? My physical plant does not include the tools to proof waveguides. Someday it will. In the meantime I must rely upon the interest of others better equipped than I.
I do believe waveguides work. I'm out on a limb with this because my belief is mostly a hunch, intuition, if you will.
Geddes says the throat should be normal to the axis of the tweeter. Then he admits his waveguides are slightly open. He is also using compression drivers which, although not perfect, produce something closer to a plane wave than a dome. In that we pursue mounting a dome tweeter to a guide, maybe the best we can come up with is the "sweet spot". I think it too constricting, a shame really, that we focus too much on the number, THE number, that is the answer to a search. I would be more comfortable, and just as satisfied to work within confidence limits...and probably spend more time enjoying music.
Regards
My brief search has not turned up a US source for Monacor. I'd like to try them also...but the wish list is a long one.
I admire the work Troels does...and his presentation.
Research? My physical plant does not include the tools to proof waveguides. Someday it will. In the meantime I must rely upon the interest of others better equipped than I.
I do believe waveguides work. I'm out on a limb with this because my belief is mostly a hunch, intuition, if you will.
Geddes says the throat should be normal to the axis of the tweeter. Then he admits his waveguides are slightly open. He is also using compression drivers which, although not perfect, produce something closer to a plane wave than a dome. In that we pursue mounting a dome tweeter to a guide, maybe the best we can come up with is the "sweet spot". I think it too constricting, a shame really, that we focus too much on the number, THE number, that is the answer to a search. I would be more comfortable, and just as satisfied to work within confidence limits...and probably spend more time enjoying music.
My attempts to interpret the formula Geddes offers for this gets me hung up in the units. Could you shed some light on this?
Regards
Ralph,
Good stuff, makes it a bit easier for us cloth-heads (me!)
I'd be very interested in anything you find re ribbons. Horizontal dispersion is pretty good with a 4", but vertical is almost non-existant. I'd be interested in seeing how you would design a wave guide for this - my brain gives up fairly quickly...
N.B. it does on most things nowadays - not enough booze I reckon!
Good stuff, makes it a bit easier for us cloth-heads (me!)
I'd be very interested in anything you find re ribbons. Horizontal dispersion is pretty good with a 4", but vertical is almost non-existant. I'd be interested in seeing how you would design a wave guide for this - my brain gives up fairly quickly...
N.B. it does on most things nowadays - not enough booze I reckon!
Hi Ed,
Waveguides definitely work! They will undoubtedly become more and more popular in the years to come. As more people gain an understanding of the operation and the audible benefits they bring, more manufacturers will introduce waveguide loaded speakers and so more people will be listening to them. Their sphere of influence will slowly expand.
The great benefit that waveguides offer is in minimising the sweet-spot. The speakers sound the same off-axis as on-axis. Stereo imaging is also vastly improved because the spectral content doesn't change as the listener moves off axis.
I've been listening to horn loaded systems for many years. I have a love-hate relationship with them. I love the directional control that horns offer (like waveguides) but don't love the colouration much. The sound of horn systems is so punchy and dynamic. Direct radiator systems often sound lifeless and flat to me.
Wave guides offer all of the benefits of horn loading, except efficiency, with none of the drawbacks. A chance to get the dynamics of horns and the smoothness of direct radiators!
I've empirically determined that the mouth diameter needs to be about the same as the lowest wavelength of interest. But it's not exact. Waveguides lose pattern control very gradually. It's up to the designer to decide the crossover frequency based on how directional the bass/ midrange driver is becoming.
Looking at the last graph of my waveguide page
http://www.aeronet.com.au/waveguide.htm
shows directivity remaining constant from 4kHz up to the point where the ring radiator starts beaming. Below 4kHz the off-axis plots gradually start to converge with the on-axis response. This means that the sound is starting spill out of the waveguide. By 2kHz the spill is becoming significant and the sound radiated by the waveguide is no longer contained to a 120 degree cone as set by the included angle of the waveguide. It may now be spreading out to 150 degrees or more. So I would call the useful low frequency limit of pattern control for this particular waveguide to be about 2.5kHz. Given that the waveguide has a diameter of about 120mm, this is about the same as the wavelength at 2.5kHz.
Cheers, Ralph
Waveguides definitely work! They will undoubtedly become more and more popular in the years to come. As more people gain an understanding of the operation and the audible benefits they bring, more manufacturers will introduce waveguide loaded speakers and so more people will be listening to them. Their sphere of influence will slowly expand.
The great benefit that waveguides offer is in minimising the sweet-spot. The speakers sound the same off-axis as on-axis. Stereo imaging is also vastly improved because the spectral content doesn't change as the listener moves off axis.
I've been listening to horn loaded systems for many years. I have a love-hate relationship with them. I love the directional control that horns offer (like waveguides) but don't love the colouration much. The sound of horn systems is so punchy and dynamic. Direct radiator systems often sound lifeless and flat to me.
Wave guides offer all of the benefits of horn loading, except efficiency, with none of the drawbacks. A chance to get the dynamics of horns and the smoothness of direct radiators!
I've empirically determined that the mouth diameter needs to be about the same as the lowest wavelength of interest. But it's not exact. Waveguides lose pattern control very gradually. It's up to the designer to decide the crossover frequency based on how directional the bass/ midrange driver is becoming.
Looking at the last graph of my waveguide page
http://www.aeronet.com.au/waveguide.htm
shows directivity remaining constant from 4kHz up to the point where the ring radiator starts beaming. Below 4kHz the off-axis plots gradually start to converge with the on-axis response. This means that the sound is starting spill out of the waveguide. By 2kHz the spill is becoming significant and the sound radiated by the waveguide is no longer contained to a 120 degree cone as set by the included angle of the waveguide. It may now be spreading out to 150 degrees or more. So I would call the useful low frequency limit of pattern control for this particular waveguide to be about 2.5kHz. Given that the waveguide has a diameter of about 120mm, this is about the same as the wavelength at 2.5kHz.
Cheers, Ralph
Hi Jon,
Nice to hear from a local enthusiast!
Yeah I know what you mean about the limited vertical dispersion of long ribbons. I've got a pair of Ravens and the sound almost disappears completely at large off-axis angles!
Unfortunately there's nothing that can be done about it, at least not with a waveguide. All a waveguide can do is to contain wide dispersion to the included angle of the waveguide.
Because of the radical changes in directivity of a ribbon with frequency, waveguides are especially well suited to ribbons. I have a great fondness of the ribbon sound and I think a well designed waveguide makes them sound even better.
The limited vertical dispersion isn't such a big liability in some ways. They are well suited to being integrated in a d'Appolito style systems where vertical directivity is deliberately increased near the crossover frequency. Combining d'Appolito mids with a ribbon and waveguide sounds very promising.
The same principles apply to a waveguide for a ribbon as to a dome or ring-radiator. Just that the throat will be rectangular. The top and bottom flanges of the waveguide won't being doing very much as the vertical dispersion is already so limited. Check out the Genelec S30D for inspiration. http://www.genelec.com/products/s30d/s30d.php
Cheers, Ralph
Nice to hear from a local enthusiast!
Yeah I know what you mean about the limited vertical dispersion of long ribbons. I've got a pair of Ravens and the sound almost disappears completely at large off-axis angles!
Unfortunately there's nothing that can be done about it, at least not with a waveguide. All a waveguide can do is to contain wide dispersion to the included angle of the waveguide.
Because of the radical changes in directivity of a ribbon with frequency, waveguides are especially well suited to ribbons. I have a great fondness of the ribbon sound and I think a well designed waveguide makes them sound even better.
The limited vertical dispersion isn't such a big liability in some ways. They are well suited to being integrated in a d'Appolito style systems where vertical directivity is deliberately increased near the crossover frequency. Combining d'Appolito mids with a ribbon and waveguide sounds very promising.
The same principles apply to a waveguide for a ribbon as to a dome or ring-radiator. Just that the throat will be rectangular. The top and bottom flanges of the waveguide won't being doing very much as the vertical dispersion is already so limited. Check out the Genelec S30D for inspiration. http://www.genelec.com/products/s30d/s30d.php
Cheers, Ralph
Hi Sjef,
JBL make a series of suitable waveguides called the "Progressive Transition Waveguides"
http://www.jblpro.com/PD5000/PDF/PT_WaveGuide.pdf#search="pt waveguides"
Design Direct Sound make a series of horns/waveguides that work well.
http://www.ddshorns.com/catalog.php?page=products
The MCM horn is also suitable.
There's plenty to choose from, but I'm not sure exactly what is available in the Netherlands.
Cheers, Ralph
JBL make a series of suitable waveguides called the "Progressive Transition Waveguides"
http://www.jblpro.com/PD5000/PDF/PT_WaveGuide.pdf#search="pt waveguides"
Design Direct Sound make a series of horns/waveguides that work well.
http://www.ddshorns.com/catalog.php?page=products
The MCM horn is also suitable.
There's plenty to choose from, but I'm not sure exactly what is available in the Netherlands.
Cheers, Ralph
"Does someone know of any waveguide for the use with a 1" compression driver from 2.5 ~ 3kHz upwards. "
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=178
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=179
I believe there's an online Dutch distributor
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=178
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=179
I believe there's an online Dutch distributor
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