Typo_Knig

Nice little read, Fi dude (it's Scott, right?). Sometimes I wonder why I don't just throw a pro sound woofer into my car. What I notice about his thread, and discussions about measuring efficiency in general, is that no one mentions that a lot of manufacturers seem to get their number outside of their product's useable bandwidth. Don't even get me going on companies that state "in-car SPL". Any thoughts?

I'm just a lowly engineer wasting time thinking about how to defeat the Laws of Thermodynamics.

Actually, fs and Qes are what you are looking for. fs divided by Qes gives you efficiency bandwidth product (EBP). If EBP is greater than 50, then ported enclosure it is.

Great write-up. I am especially intrigued by TC's LMT. It is my understanding that even some folks at JL have given this a serious look. That alone tells me that it will be around for a while and is a worthy solution to Bl non-linearity caused distortion. Now if only someone would come up with a reactive, computer controlled electromagnet instead of ferites and neos. Sounds futuristic and expensive, but I think it would be cool just to see someone do it and then combine it with other technologies like LMT and Velodyne's accelerometer based servo control.

SIR is on the southeast side of Tucson. Here's the website: http://www.sirace.com/, and directions. I think they will have Streetbeat and SPL only. No SQ.

Just thought I'd hit this thread again..... There is a USACi SPL comp goin' down at Southwest International Raceway on June 23rd, this coming Sat. It should be really lame unless some Phoenix area people come down to drop some numbers. I might go and watch since my car is empty at the moment. Anyone?

It will screw up the tuning in an unpredictable way I would imagine. The port area should remain the same throughout the port length for the results you desire. The best way to make your adjustable port would to not have a 'L' bend in it. IMO, tune it to 37ish Hz and call it done like dinner.

I live in Tucson and would very much like to see this.

Titanium alloys fall somewhere in between aluminum and steel alloys as far as weight and stiffness. TC is experiencing a lower failure rate with Ti cones mainly because it an extrememly faftique resistant metal. It has a very high modulus of elasticity and strong memory making it an ideal material for springs. It has a more than acceptable strength to weight ratio and is corrosion resistant, this is why aerospace industries like it so. When compared to aluminum, Ti's stength to weight ratio and modulus of elasticity make it a more ideal material for a subwoofer cone than aluminum. Because it is stronger than aluminum, a thinner cone can be made. Cost in material, tooling and manufacturablity are the things holding it back. Coming from a bicycle frame building background, I have seen frames made from Ti, steel and Al alloys. The ones that are on the road the longest are the ones made from Ti.

I would only do this if my subs were getting power from two different sources (i.e. 2 amps) or receiving a stereo signal (instead mono or summed). Otherwise you will not notice a difference.

I've dealt with eD several times and never had problem once, all of the guys there have been super helpful. The 13av.2 is going to be a sick sub for sure, but it is geared toward LSQ (leaning towards SQ). You would be better off with a 19ov.2 if you want to get really loud. Any of the mentioned subs would be fine though.

Given the typical T/S specs on SS's site, both the d2 and d4 would be better sealed than vented. The d4 prefers a larger box than the d2 but both should do fine in 7.2 cubes. By my calculations a pair of d2's in 7.2 will have a -3db of ~35hz and a Q of ~.88, d4 = -3db of ~34hz and a Q of ~.95. You should see a slight gain in efficiency and power handling but with slightly peakier response. IMO, polyfill will probably not make a noticeable difference.

That box looks fantastic. What's going in it?

I would go sealed, with as large of volume as you can build. The high Qts (d1=.57, d2=.52) indicates that this woofer will favor a sealed alignment. Surprisingly, Fi recommends a ported box even though the T/S parameters are counterintuitive to this.

There, I said it. But I am not a forum Newb.