SR-2x Surround Speaker
A new surround speaker based on the S1.2 is now developed.
The S1.2 showed surround speakers indeed has a huge impact on quality of surround sound, and that requirements for surrounds are different from main speakers. Now a new surround, the SR-2x is being developed, with performance characteristics similar to the S1.2.
SR-2x is smaller, it only has one radiation configuration, much simpler in design and construction, same output capacity, same holographic and immersive surround sound. Smaller size is possible due to limited frequency range from 100Hz and up.
Preliminary specifications:
Dimensions width/depth/height: 361mm/130mm/408mm
Frequency range: 100Hz - 20KHz
Sensitivity: 92dB/2.83V/1m
Development is now completed, one set of SR-2x har been built and already delivered, picked up by the customer today. As usual, already miss them.
Measuring SR-2x in Room2, on stand to simulate placement away from rear wall:
Development of the SR-2x ended with a listening session in Room2, I placed the SR-2x above the F205 main speakers, allowing for direct comparison of the 2, now using SR-2x as main speaker, which it was never intended for.
So I got to listen to them at last. But doesn't speaker development involve lots of listening? Not really. It is more about working on simulations, and then measure to verify that the actual speaker performs as predicted. Since SR-2x is based on the S1.2, there was already a solid foundation with listening for surround use, involving the different configuration options for the S1.2.
And they work quite good as main speakers too. The first thing that is striking, is that the images appear at a similar height as from the F205, not elevated, and completely separate from the location of the speakers.
Tonality appears quite neutral, with some less energy at high frequencies.
There is depth, and a soundstage where instruments are placed in a sort of 3D landscape.
Switching to the F205 reveals that there is indeed a difference, and this is not due to preference or that one speaker does different things better. The F205 does everything better. There is this solidity of the images of instruments, and a dynamic contrast, that very few other speakers manage to reproduce.
I had them connected like this when the customer arrived, so he could hear them. Carla Bruni for vocal, then Brazz Brothers. And he liked them very much. Then I switched over to the F205, not speaking so much about what he was supposed to hear. From his comments, I conclude he had a similar experience to mine.
But surround use is different from main speakers, and those SR-2x with the wide and unique radiation pattern is much better suited for this purpose. The are not meant to be used as main speaker.
Performance
This speaker is a little different from ordinary speakers intended for mains use. It is designed for surround service, with a unique radiation pattern tailored for that purpose. So it will not measure similar to other typical speakers, nor is it intended to do so.
Frequency response on-axis should be reasonably smooth and flat, though, and it is:
This is measured in-room, so the graph is affected by room reflections and thus not smooth. Speaker is placed on a 2pi boundary, simulating on-wall mounted.
Free mounted 4pi is very close to on-wall, which means the speaker is not much affected by how it is mounted, it can also be placed away from the wall:
Used as surround, the speaker is usually placed above the listeners, and the response at -15 degrees vertical is more flat and smooth, to give the best response when used as intended:
(brown=on-axis, blue/pink=down -15 degrees vertical)
Performance - Frequency response
On-axis 4pi and -15 degrees vertical 4pi:
Individual responses from each driver:
Individual responses measured near-field with all drivers operating, including port output:
The filter design is based on technology used in the F205 speakers, with a very steep low-pass cut-off for the low frequency drivers.
Performance - on-wall and free mounted
Frequency response comparing on-wall mounted and free-field 4pi shows only smaller differences, with on-wall getting a small boost at lowest frequencies below 200hz:
(orange=on-wall, green=4pi)
Performance: Time..
Decay 4pi:
Rather clean.
Step response:
IR, it is the interval up to around 1-2 ms that is interesting here, since later reflected energy comes from room and mic stand:
This show controlled phase and timing, and there are no resonances. Nice.
Performance: Radiation pattern
Radiation pattern is of course the most important for this speaker, and where it is different from other speakers. It has a very wide, but still controlled radiation, and is even across the frequency range across a very wide radiation angle.
Horizontal 0 to 90 degrees, no smoothing:
1/12 smoothing, so it is possible to see what is going on:
1/3 smoothing, now you can read the graph and get an idea for how the speaker radiates:
It is this radiation pattern that gives the unique, immersive surround sound, and you no longer need 12 surround speakers to get good surround.
Performance: Capacity
For movies, the surround speaker must have sufficient output capacity, without excessive distortion or compression. The SR-2x has just enough capacity for typical home theater rooms. If the room is large, just add more surround speakers.
Designed for 100hz-up only, SR-2x was born with an advantage over speakers of similar size, that tries to reproduce low bass. The two horn-loaded tweeters have decent sensitivity, and since there are two of them, there is sufficient capacity also at high frequencies, it is often seen with traditional hifi-speakers that they start to compress at high frequencies at quite modest volume.
Compression measured at 1.m distance, 2pi mounted (on-wall):
Normalized compression chart, referenced to 70dB output, for 80 - 90 - 100 - 105dB. Note that level for 1m is around +1.5 dB. Above 3KHz the noise in the measurements are larger than the compression of the SR-2x speaker:
Performance: Capacity and distortion
Distortion measured at 1.2m. Note the dips at 250Hz, 350Hz and 450Hz, see compression frequency response in previous post, those dips mean the distortion will show a much higher number than the actual distortion from the speaker, and this is marked in the graphs with a masking rectangle.
Distortion 90dB:
Distortion 95dB:
Distortion 100dB:
Distortion 105dB:
Still reasonably low distortion at 105dB plot level, and dominated by 2. and 3. harmonics, higher harmonics are very low on the SR-2x. In fact, it is better than many amplifiers.