the surrounds are retarded huge on those drivers. to big IMO. i'd rather see a narrower, taller surround like used on some of the TC sounds drivers and the 18" Epik drivers.
having the surround that big robs a lot of cone area.
I can 100% see why visually this would be the case. At first glance this can be very very deceiving. In the end it increases the performance of the design.
I'll elaborate on why this design it used. I think in the end you'll find it's the best way to go from a performance standpoint for this particular subwoofer.
If your familiar with the history of our company you'll know that this design actually evolved from the other style of design your referring to in regards to the TC Sounds drivers into what it is. It is this way for good reason.
This isn't a knock to TC Sounds at all. They make great drivers! Just none really like this. We sampled a lot of speakers and in the end just decided to go our own way.
One of the most notable requirements for the suspension design here is that it needs to be linear throughout the operating range of the driver and then some. We designed the suspension (surround) this way for a lot of reasons. One of which is you don't experience a loss of efficiency the same way with this design.
When using a material like rubber as you go with higher and higher excursion drivers the material itself needs to get stronger obviously especially when using a "taller" style design. We use these styles on virtually everything else (Note : Eu-Surround on the web site) but not the Av.2 for good reason.
When the material gets thicker (read : heavier) you start to run into major mass issues. The compliance of the surround also begins to change over the excursion of the driver (even if using variable density surround designs) which essentially causes the driver to lose efficiency the further it moves from the center of the gap. Not a huge deal for most and the first renditions of the A (the driver mentioned) used these style of HT designs.
With that said. Modifications were made to fix this efficiency loss.
1. We opted to go backwards a little from our initial intentions and go with a half roll foam design with a little bit of a new twist. The SD of the design will be decreased but the overall linearity of the design actual yields more overall SPL with the same power output. (lighter and more linear is easier to move with the same voltage)
2. The overall basket diameter of the speaker is a true 13". Once you accommodate for the overall diameter change of the speaker and increase in efficiency in the suspension the SPL is easily made up (and added to).
3. This design yields less mass than many of our rubber or foam counterparts used in the development or sampling process. They were just too stiff or too heavy. In the end we had to tool our own. At this point our tooling catalog includes both.
The too stiff or too heavy thing is a big deal with especially with a underhung design. Inherently if you go too far in one direction the darn thing just gets so inefficient it's doesn't do a lot of things well.
If anyone would like us to assemble one with a "tall" surround for cosmetics and increased SD that can be done. We'll do it for you no problem. I will warn though as implemented it will come with decreases in performance and especially in this application a decrease in overall SPL.
After a few years of development this design route was selected for the following reasons.
1. We could afford to tool the frame to offset the loss in overall cone size.
2. The design yields more peak SPL.
3. The design reduces weight considerably.
4. The design is more linear.
5. The design burns less power even to it's linear limits.
6. It will extend higher in the frequency range.
7. It will be more linear at high output levels.
With other speakers with different design intentions it makes great sense. For this speaker this design and profile made the most sense for sound quality (linearity), efficiency (more SPL with the same power), and box requirements (increase mass with the same motor force = box requirements go up and put more stress on the suspension).
It's worth noting that prior to going to final production the Av.2 platform DID have the style of surround your referring to. This one just performed better for the intended applications and right before we hit final production the change was made. I'm very happy with the change.