Impious

I would just get rough measurements. Your door is not completely sealed, it's more of a leaky sealed box, so your physical Vb is going to be different than the effective Vb. Without knowing the loss factor (i.e. the amount of the leaks) you aren't going to get it 100% accurate anyways. IIRC you basically have a pod built onto the door? You might get a rough measurement of that as well.....one thing you may consider doing, depending on what mids you are looking at, is to seal the pod. If you knew the volume you could calculate how that would affect the Qtc and Fc. You might be better off using a lower Qts lower Fs driver in a sealed enclosure to bump the Qtc up to the .6-.7 range since a high Q driver is going to be harder to find, and in your situation I would probably go for a higher Q alignment to try to get some more response in the 50-100hz range.

Qtc = Qts * [ ( Vas / Vb ) + 1 ]^.5

Kevin had said the break-up was a bit higher than that, and the graphs he has posted on the site show that as well. But I honestly haven't read a single review of the actual drivers.....I sort of tracked them long enough to jump on the sale price, then forgot about them since I'm still a while from actually using them. I'm a TOOL fan....they're the only reason I even heard of Alex Grey

http://www.diycable.com/main/pdf/AnarchyDocs.pdf 3.7" Mounting Depth according to the manual, with a 4.7" wide motor. Nice drivers. I grabbed 6 of them when they were on their initial sale Plan is to use them for a 2-way MTM or TMM for HT.

Bl curve basically shows the force of the motor relative to excursion, both forward and rearward. As you can see in the below picture, Bl (motor force) is on the Y axis and excursion is on the X axis. The curve shows the change in motor force as the coil moves through the range of excursion. We can use the graph to define Xmag, which is the maximum linear operating range of the motor. This is defined by Klippel (the measuring system used to generate this graph) as the point at which the motor force (Bl) has fallen to 70.7% of it's rest value. Xmag is important because it is one of the determinants of Xmax, which defines the maximum linear excursion the driver is capable of achieving, which can be used to define the maximum usable output a driver is capable of achieving. Xmax is the lesser of Xmag and Xsus (Xsus being the linear maximum linear operating range of the suspension). The graph also shows us the linearity of the motor. There are a few schools of thought on the "ideal" curve, but generally we would like to see the motor force stay relatively constant throughout the operating range of the driver. This means the curve wouldn't be as much of a "curve" as it would be a plateau, like the one pictured below, that stays flat for a period of time then begins to roll-off at the edges. The Bl curves for some drivers look more like an upside-down "U", those are said to be "parabolic" curves (there's some of that high school geometry you swore you'd never use in real life!). The reason we would like to see the "curve" stay flat is that if the curve is moving upward or downward, this is indicating a change in motor force at those excursion levels. This is generally bad for driver performance for a few reasons, but primarily because a change in motor force will cause a change in Thiele-Small parameters which will affect the response of the driver, and because a change in motor force will create non-linearities that will manifest as distortion. So yes, generally a Bl curve will give us an idea of the performance we can expect to see from a driver and can give us a glimpse into the quality of the design of the motor. But it takes more than a Bl curve to give us a good idea as to the "SQ" of a given driver. A Bl curve alone won't do it. But a good driver starts with a good foundation......and a nice Bl curve indicates a well thought out and well executed motor design, which is a great start to having a great driver

Arc Audio, Clarion and Genesis all have/had class G/H amplifiers. Hell, Bazooka has a class H amplifier.

Yes, the voltage output with music will be significantly lower. The test tone you are using is probably 0db, essentially meaning it's recorded at the highest possible level. Music on the other hand will have an average level much lower, somewhere in the -6db to -20db range depending on the music and recording process. This means that with music, you are going to get much less average power from the amplifier than you would with that 0db test tone. Two ways to combat this; 1) Use a test tone other than 0db, for example a -3db, -6db or -10db test tone, to set the gain with the DMM, 2) Set the gain by ear with a sampling of your typical music. I would vote for the latter, unless you are incapable of noticing when your drivers are being stressed or overdriven. In which case, use a -3db or -6db test tone.

Are you using passive crossovers and if so does the crossover have tweeter protection?

Try just the mid.

The one I linked to was for flat response. There are several others on that website.

He said he doesn't plan on going active.

Is it possible to have a 2-way frontstage with an 8" mid and a tweeter? Yes, it is. There are some things that need taken into consideration, so these aren't "easy" setups to accomplish. But it's possible. Are you going to do it with an 8" subwoofer like the REx? No, you are not. Just because it's an 8" driver, it does not mean it will make a good mibass or midrange (since the driver would be playing well into the midrange). Drop the idea of trying to use the REx as a mid in a 2-way setup and just go with a pre-built comp set. Those Type-R components are actually fairly interesting; the mid uses a dual-gap motor similar to XBL.

As mentioned above, try reversing the polarity of one of the mids and see if that has any change.

Depending on his vehicle and the wire gauge he is using, the chassis may be a better conductor.

o.p. or OP stands for "original poster", i.e. the person who started the thread. I'm with Duran as far as audibility goes. That is assuming we are talking about changing frequency only and not enclosure size/etc aswell.

While I didn't completely understand your post......if you were planning to try to run the 8" REx with tweeters as your front speakers....No, not going to happen. Why not just go with the XXX comps if you were wanting to stick w/ RE?

I wouldn't go for the Daber given your intended application. Just going by inductance, the driver will have a self-induced roll-off beginning around 280hz, which is more than a half-octave below your desired bandwidth. I'm really not sure where this Qts of .35 thing came from? Qts alone isn't going to help you entirely. There is a significant difference in response between a driver with a Qts of .35 and an Fs of 70hz, and a Qts of .35 and an Fs of 35hz. The 2nd driver would have an F3 approximately one octave lower than the 1st in the same alignment. So you need to consider both the Qts and Fs to really determine the response. Really, what you're actually looking at is Qtc and Fc....in an ideal "IB" environment, Qts = Qtc and Fs = Fc. However, your door may not end up being a true IB environment. So the Qts and Fs may be different than the Qtc and Fc. You need to consider how your door is going to affect the driver, and the effect will be slightly different for every driver depending on it's Vas. The 2nd thing to consider is differences in driver behavior with different Qtc's. A lower Q is going to be more overdamped with a shallower roll-off and generally the least output above F3. Subjectively this is typically said to be a little "dry" or "sterile". A higher Q is going to be a little more underdamped with a steeper rolloff but slightly more output above F3. Subjectively this would be a little "thicker". A Qtc of .5 has optimal transient response at the cost of peak output and a higher F3. A Q of .707 has optimally flat frequency response, the lowest F3 and transient response that is still considered good. A lower Qtc typically has slightly more output at the lower frequencies (somewhere below F3) due to it's shallower rolloff even though the F3 may be slightly higher. F3 is the frequency at which the response has rolled off to a level of -3db. So, the main point of those brief paragraphs was to explain that your target Qts may or may not be ideal depending upon where you want your final Qtc to end up, and also that you can't look at Q alone you also need to consider Fs/Fc. If you were pushing the power limits to get the output you wanted in the midbass, a higher Q alignment may give you a little more output in the 60-100hz (depending on the Fc). Another thing to look at is inductance, or Le. A driver's inductance and resistance create a classic 1st order (6db/oct) lowpass crossover. You can determine the corner frequency with the formula; Frequency = Re/(2*Pi*Le) *Le in henries Ideally you would want this to be one octave above your intended crossover frequency. Additionally the response should be relatively flat within this bandwidth. If you can find some distortion and other measurements to make sure it doesn't experience any cone breakup or distortion issues within your intended bandwidth, that would be a bonus. I would also take displacement into account. The more the merrier. For example, with the Sd of that Aura, it will take 9mm of excursion to reach 100db. If you plan on listening at or above levels of 100db, you will need a driver with atleast 9mm one-way Xmax (with 346cm^2 of Sd). The louder you want to go, the more excursion you will need. Sensitivity.....meh. The only reason I ever really care about sensitivity is in regards to Hoffman's Iron Law. That's what I can think of off hand.

Put a wire everywhere you see a black line in the picture

It's been out all of a few weeks, there aren't a whole lot of of people who've heard them. From the reviews I've read, it performs as advertised when the proper methods are used when taking the auto-measurements. By all appearances, it seems to be more advanced than the Imprint system Alpine uses, it has 8-channels of routable outputs compared to Imprint's 6 channels, and to my understanding it's user adjustable after the auto-measurements are taken which Imprint isn't. All-in-all, it seems to be the best auto-tune system on the market and given it's advanced algorithms and internal tuning capabilities, it should be capable of achieving better performance with a couple minutes of measurements than an individual could get themselves given several days or weeks (or months) of tuning time with standard measurement equipment. It simply has more access to more features with the auto-tuning than most processors allow a user to adjust. From what I've heard, it can be finicky if the proper steps aren't taken prior to taking the measurements. For example, the speakers need to be relatively level-matched and the system can not be too loud or it'll throw off the measurements, turning your head too far or not far enough will throw off the measurements. So it's not completely idiot-proof. I've been debating whether or not I want to ditch my H701 in favor of the MS-8. From the initial reports, the tuning is very good and it's incredibly quick and easy. To me, the time savings and end results may be worth the premium. To others, it may not be. Or someone may be happy enough with their current system that the added cost isn't worth it. However, to get comparable results for less money expect to at minimum need a decent audio processor (H701, Audison Bit1, etc), access to measurement equipment and a whole lot of time.....it's not something you will accomplish on your own in a weekend tuning the system yourself. But usually, there are minor bugs that get worked out or minor improvements made after the initial release; so I may wait a year, let the street price come down some (or find a used one) and see if any changes get made before I spring for one. There are several hundred pages of info on DIYMA as well as several reviews.

Yes, if you set the switch to "full" then the filter is not effective. This is bad. You want to highpass your speakers.

Indeed, sounds like you need to decrease the frequency for the highpass crossover.

I reversed the polarity on one side of the components at the amp ( with the subs off) there was minimal difference, to me at least. When i open a door and stand outside of the truck there is no real midbass sound. You can hear the bassline in the music of course, but it sounds like a 6x9 with "bass blockers" on it. The supplied crossover doesnt have any adjustments on the mid side. According to the spec sheet the frequency response for the mid is "55Hz - 22kHz". There is nothing that ive found showing what the frequency of the crossover is. I have the filter on the 4channel amp set to "All Pass", and the Deck EQ Bass level maxed at 6 (mids at 5, Hi's at 6.) It won't tell you what the frequency of the highpass crossover for the midwoofer is because it doesn't have one. You need to highpass the midwoofer either via the amplifier's crossover or the HU's crossover. Set the crossover on the amplifier to "highpass" instead of "allpass" and set the crossover frequency unless if you are using a highpass crossover in your headunit. The headunit might not have one, but if it does then you need to look and see what it is set to. What headunit do you have?

Not necessarily. Anyways..."optimal" is a matter of opinion. There are advantages, disadvantages and trade-offs involved with all of the various alignments and a single formula is not going to be comprehensive enough to encompass all of these various factors. What's optimal for one driver or one goal may not be optimal for a different driver or a different goal. This is one of the main reasons you hear things like "you can't model a Fi BTL". You can, the physics are the same. The problem is that when you run the driver's parameters through the formulas for "optimal" enclosures meeting certain target curves such as flat frequency response, the results are nonsensical simply because the driver's parameters don't allow it to meet those target curves. Or if the formula you are using is the formula for optimally flat frequency response, you may be trading off low end extension or end up with too much low end extension for the environment, in which case that "optimally flat frequency response" won't be optimally flat in the actual environment. If you really want to know formulas, DIY Subwoofers has a lot of various formulas to sift through. Being a big proponent of empirical analysis, I find formulas extremely useful. However, when dealing with things like ported enclosures it's best to not focus or limit yourself by the formulas themselves but instead use an accurate analysis tool, such as an enclosure modeling program, to design boxes based on the given set of goals you are trying to achieve.

Good luck man. With any luck this will be an inspiration for me to finally get off my duff and actually start exercising for first time since high school.

And what would you reccomend in a $200 budget for both tweeters and midbasses It would be better to have this conversation in another thread of your own making