Waveguides and multiple subwoofers are very popular these days, thanks to Earl Geddes for sharing his knowledge with the community. So after playing around with fullrange dipoles and dipole satellites with 4 subwoofers I decided, back in October 2010, to build an active cardioid / waveguide system with four subwoofers: El Cuerno. For the cardioid part I was inspired by the work of MKB (http://www.diyaudio.com/forums/multi-way/142691-adventures-cardioid.html).
Signal processing is done on an old computer running Linux/BruteFIR for filtering and MPD (Music Player Daemon) for music playback. El Cuerno is actually a complete system, but I believe that the rightful place on this forum is in 'multiway speakers' because the DSP and amplifiers eventually ‘serve’ the multiple electro-acoustical transducers (obviously the point of view of a loudspeaker designer
)
Satellites
The drivers used are the 18Sound XT1086 waveguide with a NSD1095N compression driver and a B&C 10PS26 midwoofer. The mid plays between 200 and 1000 Hz and the waveguide above that. The satellites are active, mid and high are each driven by a Hypex UcD180.
The baffles are made of 20 mm thick pinewood, 32 cm wide and 90 cm high. The waveguides are damped with 25 PPI open cell foam (not shown here).
Using some containerboard and foam it is possible to create a supercardioid radiation pattern for the mid. I’m still looking for a solution to upgrade the looks
The gated directivity sonogram of the horizontal plane (1/12 octave smoothing) shows a very smooth transition between mid and high. The directivity is fairly CD, a slight increase in directivity towards higher frequencies can be observed. The filter is currently a very steep FIR filter, it is expected that vertical directivity measurements will show less lobing than a standard LR4 or LR8.
The satellites are toed-in at an angle of 45 degrees, so the listening axis will be approximately 20 degrees off-axis.
Subwoofers
The four subwoofers each have a Peerless SLS12 in a 25 liter closed cabinet. Two of them play in a corner-woofer stereo configuration between 120 and 200 Hz. The range of 20 to 120 Hz is mixed down to mono and sent to all four subwoofers. A room-correction curve is based on a spatial average.
Listening position
The satellites are placed along the long wall of the room (3.8 x 9 m).
And this is how it sounds at the listening position (spatial average of left, right and left+right combined).
El Cuerno has more precise imaging than the dipoles and they can play much louder (> 105 dB at listening position). One reason is the higher than normal efficiency (less thermal compression, lower excursion). Another, perhaps more important reason, is that the narrow directivity provides a much higher direct/indirect ratio of sound at my listening position compared to the dipoles or normal-directivity speakers. There is a tendency to play 5 to 10 dB louder, which I attribute to the higher ratio of direct sound and which is only apparent after measurement with a SPL meter (or an attempt to have a conversation).
Signal processing is done on an old computer running Linux/BruteFIR for filtering and MPD (Music Player Daemon) for music playback. El Cuerno is actually a complete system, but I believe that the rightful place on this forum is in 'multiway speakers' because the DSP and amplifiers eventually ‘serve’ the multiple electro-acoustical transducers (obviously the point of view of a loudspeaker designer
)Satellites
The drivers used are the 18Sound XT1086 waveguide with a NSD1095N compression driver and a B&C 10PS26 midwoofer. The mid plays between 200 and 1000 Hz and the waveguide above that. The satellites are active, mid and high are each driven by a Hypex UcD180.
The baffles are made of 20 mm thick pinewood, 32 cm wide and 90 cm high. The waveguides are damped with 25 PPI open cell foam (not shown here).
Using some containerboard and foam it is possible to create a supercardioid radiation pattern for the mid. I’m still looking for a solution to upgrade the looks
The gated directivity sonogram of the horizontal plane (1/12 octave smoothing) shows a very smooth transition between mid and high. The directivity is fairly CD, a slight increase in directivity towards higher frequencies can be observed. The filter is currently a very steep FIR filter, it is expected that vertical directivity measurements will show less lobing than a standard LR4 or LR8.
The satellites are toed-in at an angle of 45 degrees, so the listening axis will be approximately 20 degrees off-axis.
Subwoofers
The four subwoofers each have a Peerless SLS12 in a 25 liter closed cabinet. Two of them play in a corner-woofer stereo configuration between 120 and 200 Hz. The range of 20 to 120 Hz is mixed down to mono and sent to all four subwoofers. A room-correction curve is based on a spatial average.
Listening position
The satellites are placed along the long wall of the room (3.8 x 9 m).
And this is how it sounds at the listening position
(spatial average of left, right and left+right combined).
El Cuerno has more precise imaging than the dipoles and they can play much louder (> 105 dB at listening position). One reason is the higher than normal efficiency (less thermal compression, lower excursion). Another, perhaps more important reason, is that the narrow directivity provides a much higher direct/indirect ratio of sound at my listening position compared to the dipoles or normal-directivity speakers. There is a tendency to play 5 to 10 dB louder, which I attribute to the higher ratio of direct sound and which is only apparent after measurement with a SPL meter (or an attempt to have a conversation
).
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Erjee, nice of you to show your system here as well. It was your system that inspired me to design my latest speakers.
You are most welcome!
The measurement was done inside, at a distance of 1 meter, so gating is applied. Outside would be better, maybe I can take them to Keyser (again
You are most welcome!
Thanks, I am planning to redo the containerboard with something more substantial and get the response right using gated measurements and a spatial average at the listening position. Then it would be nice to confirm te response with outdoor measurement, hopefully it does not rain in your 'anechoic chamber'
I think we were both surprised by the sound quality and dynamics of the waveguides.
I think we were both surprised by the sound quality and dynamics of the waveguides.
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Thanks!
There is a solid and tight foundation, for sure, but it is not too much (from my perspective as a bass player
)Thanks! Whenever you are in the netherlands, come by for a listen
Yes, in combination with a lot of ducktape (and a couple of screws now), that's all
Combined with the large magnet of the midwoofer this creates a fairly narrow, well damped slit. The lightgrey foam is Visaton NG42 (Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories) and the dark grey stuf is some unbranded acoustic foam to fill-up the remaining gap.
As far as I know it is not fire-retardant. The foam is not positioned close to the voicecoil, it only covers the ribs of the 10PS26 so there is some volume of air.
But I won't expect problems for normal home-use. My Hypex amplifier can only deliver 100W/8Ohm, which is just enough to deliver peaks at 200 Hz of 105 dB at listening position, and I never felt a change in temperature of the magnet after playing loud. I estimate that the average power in such a situation would be much lower, maybe 10 W, because the sensitivity at 500 Hz is 5 dB better and the average power level for music is much lower than the peak level.
Hi SumacSK,
Thanks! I found a measurement of the mid alone:
This is the raw response without any eq.
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Thanks!
I have no access now to a high resolution photo of the back now, but the construction is as simple as you can see in the photo. The 10" midwoofer has a large magnet, the volume between the magnet/frame and cardboard cylinder is filled with foam. I think the cardboard construction is somewhat lossy so this might contribute in a positive way.
If the construction is still unclear to you, please say so, I can make a drawing for you.