fading away.........................
Well, not... exactly, but there certainly hasn't been much action on this. It' would seem fair to provide an updated blog. Some of these snippets are positive, and some are not.
First, TC Sounds has promised me a prototype woofer 3-5 times over the past 2 years, but hasn't delivered anything. I have given up calling them. I believe TC sounds is able to build a very good product, but getting one of them is almost impossible. I heard via good rumor-mill that TC sounds also lost their largest commercial customer about 1 year ago. My guess is this happened because TC Sounds was slow to deliver, but this is only a guess. Subsequent to the loss of the large customer, TC sounds started openly selling their products for survival. I am sure they are good drivers, but they are intended for small-box/Low-sensitivity applications. The key T/S parameter in determining the relative sensitivity and design intent of a driver is the VAS. Specifically, anything larger than @ 160 liters in a 12" is desirable. There is nothing suitable in the current production drivers.
However, I still have some hope with regard to TC Sounds. They appear to be making an aluminum cone 15" driver with a really sweet motor assembly. It will use the cloth surround which should be very light/durable, and support high VAS
. I have been very patient in this regard, and my patience might pay off
. There is certainly a possibility that the T/S parameter set might favor a pro-sound application in the extreme. Fortunately, there are methods to raise the Qes and lower the F3 to an appropriate level.
Can you give us your opinion on what T/S parameters values of woofers give more chances to get good bass, whatever loading type you use?
This is a huge issue that really should take 10+ pages of text to complete. I will present a summary, but there will certainly be many gaps in my comments do to the large breadth of information present.
My general opinion on the matter is the very best set of compromises (not all things are a compromise) happens when the VAS is VERY high and the woofer can obtain 35-40hz f3 in a sealed enclosure. This will necessitate a large cabinet.
For a 12" driver, the SCC300 is darn near perfect, but the QMS is perhaps a bit high. BUT, there was a very reputable commercial manufacturer who conveyed that a high QMS woofer is actually superior. Candidly, I am not sure about this. There are compromises in the amplifier realm when considering the impedance peak presented. The steep phase angle created by a high impedance peak MAY cause undue reluctance issues in the amplifer and may be slightly detrimental. I have not tested "the same woofer" with a different QMS to verify this phenomena using various amplifiers.
There is also the issue of linearity and inductance. Given the SCC300 at normal listening levels the cone movement is VERY small and the linearity is not an issue. When driven with a good 100wpc my pair of SCC300 drivers might move @6mm peak to peak. And these woofers are quite sensitive. Hence, my believe is that among woofers, the issue of linearity is very small. The issue of inductance might more significant, but only as the frequency rises considerably. A staunch German and industry expert once coneyed that having shorting rings in a motor is only important at very high frequencies that approximate when inductance would cause the motor/driver frequency response to roll off.
Another snippet... A very knowledgeable "little bird" once told me the TC2 (2" voice coil) driver provided less distortion and better sound than the TC2+ (3" voice coil). This was verified by, hm, another "industry guy". The reason wasn't conveyed, but the spider length seemed to be important. This seems counter intuitive, but I am in no postion to disagree.
If I could have my ideal woofer, I suppose it would have a VAS of about 250 liters and a combination of QTS and Fs necessary to obtain a sealed F3 of 40hz. The dcr would not drop below 6 ohms, and the X-Max would be @ 15mm. The Qms would not rise higher than 4. The net result would be slightly more than 90db sensitivity in about 4 cubic feet.
The cabinet grows commensurate with sensitivity for every 3db of sensitivity (all other factors being equal), the cabinet size necessary will double. This means that my target bass system would be @ 2 cubic feet if the sensitivity were 87db@2.83 volts. This also means that my target bass system would be 8 cubic feet if the sensitivity were 93db@2.83 volts.
I will digress somewhat herein and rant. There is no magic way to sneak around the rules of physics with regard to sensitivity, dynamics, thermal compression, bass depth and cabinet size. The following are true.
1. Obtaining good bass dynamics requires high sensitivity. Less heat dissipation in the voice coil will result in a more consistent dcr for the voice coil and more snap in the woofer. If the voice coil heat rises after the first few pulses, the subsequent pulses will be encountering a high resistance voice coil. Hence, the initial wave encounters a cool voice coil and subsequent waves encounter a hot voice coil. The distortion is bad bad bad. It happens with ALL drivers. However, for every 3db increase in sensitivity, the heat generation is halved aa .
2. 4 ohm sensitivity loudspeaker drivers generate twice the heat of 8 ohm drivers. This is because while the voltage remains constant the amperage (and electrical friction) is doubled. Hence a 87db 8 ohm speaker will produce the same amount of voice coil heat as a 84db 4 ohm speaker.
3. Given the normal state of hifi, it seems that most speakers are @ 84db at 4 ohms. The result is a nice small cabinet and/or a very low F3. However there are compromises. Relatively speaking, a 90db at 8 ohm speaker will be 8 times better with regard to heat dissipation/thermal compression. This is because the 84db at 4 ohm speaker obtains this rating using an industry standard 2.83 VOLTS (not watts). The 84db at 4 ohm speaker will use 8 times MORE current than a 90db at 8 ohm speaker. The 84db at 4 ohm speaker will also generate 8 time more HEAT
.
4. A small cabinet sealed woofer having a bass boost augmentation circuit is NOT a solution to the problem of thermal compression. The circuit is simply taking the low sensitivity response of a woofer at low frequency and applying more "heat" to the system.
It should be obvious that I DO think sensitivity matters - significantly. However, most folks aren't willing to spend the necessary money commercially for the big cabinet necessary to obtain the high sensitivity. Shipping methods, shipping damage, and cabinet cost are certainly contributing factors.
There are other issues too. Certainly muliple woofers will double the voice coil area. Underhung woofers offer something mysteriously good and favorable. The woofers from Adire seem to market well, and their XBL2 motor appears special, but I have heard this is a reincarnation of an old idea. Foam surrounds often provide better dampening and more favorable compliance. There are differences in spider quality. Voice Coil lead wires can impact the spider/cone during operation. Some drivers have steel terminals.
I would also like to convey some sentiments regarding my youth impressions and their validity today. In my youth, any decent/cool speaker was a 3 way. The old Cerwin Vega's and big JBL speakers sounded really great. The midrange was tolerable at best, but the bass was really cool. The music was mostly "nose", but this noise was garbled through the speakers and good bass was the goal. Today I continue to have a desire for that thump, thump, and will occasionally listen to Emotions/EWF "Boogie Wonderland" and similar music on my 3-way speakers. However, the other 99% of my music is conveyed much better on the 1801 (a 2-way). And, while there is some sound quality improvement when implementing a good woofer under the 1801 and unloading the midrange, the impact is NOT monumental. I think adding a woofer and unloading the 1801 midrange had about the same impact as replacing the BB2134 opamp with the BB2111 opamp in my CD player. Both certainly were improvements, but on par.
While you were in the middle of the R&D for a good woofer did you give this one a look?
It seems like it meets your criteria for sensitivity and VC diameter, so I'm curious to know what your impressions were.
Thanks!
Eton
11-581 11” HEXACONE Woofer
Yes - definitely. I heard this woofer in a big $$ Kharma speaker a few years ago. The bass was good, but inferior to the SCC300. There are many variables herein. The cones are equally stiff. The Eton was ported. The SCC300 was sealed. The T/S parameter sets are slightly different. The SCC300 has considerably more X-Max. The source gear and rooms were completely different too (different but roughly equal). Nonetheless, I feel very safe in my assertion that the SCC300 is a better sounding woofer - by a good margin.
//
Soooo, back on track with the 3-way blog... I still wish to eventually do attempt some flavor of fully underhung speaker. This will have to wait until TC Sounds finishes their pro-sound 15" woofer with the underhung radial motor. Hopefully the T/S set is amicable for a larger sealed speaker.
For now, I just purchased a pair of C79 midrange drivers. They arrived @ 1 week ago. The intent is OW1/C79/SCC300.
I still have to finish 1 more pair of customer speakers before I can begin this project. I am getting close.
Dave
