I have been on the hunt for some good woofers. In the range of 30-500 hz. I keep coming across something called "symmetrical drive".
Maybe someone can answer these questions:
The dampers in your car affect handling and comfort. You want more handling? You go stiffer, then you lose comfort. You want better comfort? You go softer, you lose handling. That is unless you have better technology like a digressive shock. Better comfort with basically no drawback in handling. The trade is higher cost. Is symmetrical drive this same concept?
As far as I can tell tell, there are only 3 companies that use symmetrical drive. This first is Scanspeak with their revelator and illuminator lines. The other two, allegedly, employ designers that left Scanspeak. SB acoustics with their Satori line and Wavecor with their higher end lineup of woofers.
The final question becomes: Is it worth it?
Lets compare two drivers:
This Wavecor has a regular drive and is $120
For $51 more you can get a symmetrical drive.
Clearly this isn't a one to one. But I am wondering how much more you get. Is it a huge difference? Or is it just a "nice to have"
Maybe someone can answer these questions:
- What exactly is it?
- How does it work?
- What is its benefit?
- What brands/lineups use it?
- Is it more advantageous in one octave over some others? Or is just just plain better?
The dampers in your car affect handling and comfort. You want more handling? You go stiffer, then you lose comfort. You want better comfort? You go softer, you lose handling. That is unless you have better technology like a digressive shock. Better comfort with basically no drawback in handling. The trade is higher cost. Is symmetrical drive this same concept?
As far as I can tell tell, there are only 3 companies that use symmetrical drive. This first is Scanspeak with their revelator and illuminator lines. The other two, allegedly, employ designers that left Scanspeak. SB acoustics with their Satori line and Wavecor with their higher end lineup of woofers.
The final question becomes: Is it worth it?
Lets compare two drivers:
This Wavecor has a regular drive and is $120
For $51 more you can get a symmetrical drive.
Clearly this isn't a one to one. But I am wondering how much more you get. Is it a huge difference? Or is it just a "nice to have"
The SD system is explained in this PDF: https://www.scan-speak.dk/datasheet/tech/Scan-Speak_Technote06_SD-System.pdf
For a wide band woofer it may be "worth it", but the difference is certainly not "huge".
In automotive terms, more like comparing a V12 of the same displacement to a V6, rather than linear, progressive or digressive suspension dampers.
Various names have been used for "symmetrical drive", JBL called it "Differential drive", 18sound calls theirs "Tetracoil".
Some discussion here:
For the differential drive to "win", it should produce less distortion than single coil woofers, which it does not.
According to figure 7 on page 6, the 2268H driver has 10% third harmonic distortion at 33Hz at ~7.4mm excursion (estimated), and 10% second harmonic distortion at ~25Hz at ~7.3mm excursion.
The drivers impedance is over 20 ohms between 25 to 45Hz.
That distortion was at 23.7 volts...
Since the "symmetrical drive" costs considerably more for an equivalent (real) Xmax, a less expensive conventional driver with more Xmax could outperform it.
Shorting rings are effective at reducing distortion and modern drivers tend to have them. Symmetry isn't really the point, but rather consistency of coil inductance.
Even if it were the point, the concept of favouring symmetric distortions at the expense of asymmetric distortions is something we could share with amplifier design. If such information were available you'd want to consider whether the driver can maintain a monotonically decreasing set of harmonics consistently over a range of levels.
Even if it were the point, the concept of favouring symmetric distortions at the expense of asymmetric distortions is something we could share with amplifier design. If such information were available you'd want to consider whether the driver can maintain a monotonically decreasing set of harmonics consistently over a range of levels.
"symmetrical drive" in this context is just a marketing buzzword for their motor configuration that just yields symmetric BL and Le(x) curves. Nothing more.
Understood. Thanks for engine cylinder explanation. Automotive comparisons are most helpful to me. I compare everything to cars.