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What is sensitivity? The sensitivity of a driver is typically defined as the sound pressure level of the loudspeaker given 1 watt of power input, measured at a distance of 1 meter, measured on-axis with the loudspeaker and measured in infinite space with the loudspeaker mounted to an infinite baffle. While the later part is typically assumed but not stated, the former part is the reason you generally see “1w/1m” or “2.83V/1m” stated along with the sensitivity specification. But wait, is 1w/1m equal to 2.83V/1m? The answer is only for an 8ohm impedance driver. We know this because of ohms law, where Power = Voltage^2/Resistance. If the load is anything other than 8ohm then the resulting sensitivity rating will not be a 1w measurement! If the driver is 4ohm and the measurement is a 2.83V measurement, we can find the amount of power input with the formula 2.83^2/4 = 2w. This means that sensitivity will be overstated by 3db compared to a true 1w measurement. I have seen many unscrupulous companies take a dual 2ohm/coil subwoofer, wire the coils in parallel and then rate sensitivity at 2.83V, overstating sensitivity by 9db! Due to these and other variations in rating methods and some manufacturers not even stating a method, it can often be difficult to directly compare one subwoofer’s sensitivity to another’s. However, if you are able to obtain the Thiele-Small parameters for the subwoofer there is one surefire way to calculate an accurate sensitivity measurement for a driver. And that is with the following formulas; Efficiency (N0) = 9.64 * 10^(-10) * Fs^3 * Vas / Qes *To express as a percent, multiply by 100 *Vas in liters Sensitivity (SPL) = 112 + 10*Log(N0) The Efficiency (N0) calculation expresses, typically as a percentage, the amount of power input that is converted to acoustic power. With the sensitivity calculation we can convert the efficiency of the driver to a 1w/1m sensitivity rating. As long as the T/S parameters are accurate, utilizing this formula will put any two drivers on a level playing field and allow you to directly and accurately compare sensitivity (or efficiency) between drivers. Okay, but higher is still better because higher means it’s louder, right? Not necessarily the case. There are a few issues here that need to be discussed to better understand why. From a driver design perspective, we can see from the above formulas that there are two ways in which to increase sensitivity for a given driver diameter; increasing Fs or decreasing Qes (or both). Adjusting either of these two parameters, however, is ultimately going to affect how the driver responds in a given enclosure. And this relationship, as it relates to enclosure size, sensitivity and low frequency extension, has been defined through a rule known as Hoffman’s Iron Law. As you can see from the link (which I highly suggest you read), it’s already been covered in relative detail elsewhere on the site. But it’s important to us here, so it’s worth touching on again. In short, Hoffmans Iron Law states that we can only have two of the following three; Low frequency extensionSmall enclosureHigh sensitivity What’s important to take away from this is that if you want high sensitivity and a small enclosure, you will necessarily sacrifice low frequency extension. Or, conversely, if you desire extended low frequency output from a small enclosure, you must necessarily sacrifice sensitivity. While a given driver may have a higher rated sensitivity, that driver may actually have less output in the subbass region once the effects of the enclosure are taken into consideration since it may begin it’s rolloff at a higher frequency. And given in car audio we typically require reasonable enclosure volumes, having a high sensitivity can actually be disadvantageous. The second factor we need to consider is how output is achieved. Sensitivity isn’t what determines maximum output. Output is a function of air displacement. The maximum amount of linear displacement (Vd) you can achieve is limited by your cone area (Sd) and linear excursion (Xmax). As you increase the amount of displacement at your disposal, you increase the potential linear output you can achieve. Even though a driver may have a higher sensitivity, if it’s maximum linear displacement (Vd) is less than that of a driver with a lower sensitivity, the lower sensitivity driver will have the potential for higher levels of output. We also have to consider the effects of Power Compression (and I again urge you to read the link). Consider the effects of power compression applied to our scenario. A higher sensitivity driver may, for example, begin to experience more power compression at a lower output level than a lower sensitivity driver. If this is the case, then as output is increased beyond that level the higher sensitivity driver would gain less output for each increase in power and experience more parameter shift. The basic summary is that after many factors are taken into consideration, it is impossible to state unilaterally that higher sensitivity drivers will better than lower sensitivity drivers. Generally choosing one driver over another based on sensitivity alone is a bad path to follow. Sensitivity is just one of a multitude of parameters that all conspire together to define the performance of a loudspeaker. And in my humble opinion, it is one of the less important factors to consider. As with anything, there are compromises to be made and it's necessary to find the best set of compromises for your particular situation.

That really depends. Many amps that put out maximum power at 4 ohms bridged are class A/B amps, which are definitely not easier on the car's electrical than a 1 ohm stable class D amp. A class D amp that would put out max power at 4 ohms would likely have a regulated power supply, which is arguably also worse on the electrical system.

Yes that right, finally a skin you can load the forum ultra fast on your pda phone! Here's a few screen shots from my iPhone. Automatically senses what phone your on, and switches your skin if you're on the any of those popular phones in the title. Enjoy Palm-Pre users must select the skin manually.

Actually I must commend you on ACTUALLY EXPERIMENTING. 9 out of 10 times people are asked to try something they simply whine and ask on another forum and get bogus information. It's good to see someone trying so hard to figure out for themselves how/why/what really helps or hurts. While the methods left a little to be desired it still did what it needed to do and you learned from it. I think that you deserve a pat on the back for that.

It's not "worse for SQ," you're just running the amp harder. Your amp loves you more if you run it at 8 Ohms, than 1 Ohm for example. Imagine that your car would make 400HP throughout the power band. Imagine another car that only makes the same 400HP at 8000 RPM. Hypothetically speaking, which engine would be more efficient? Remember: engines are extremely inefficient and most energy converted turns to heat (waste). Electronics' enemy is also heat, making them less efficient. This is epically simplified and hypothetical, but I hope I relayed my thoughts effectively I've had an Epicenter in my car for 4 or 5 years. It does make the bass "muddy" when turned up. I keep it because some artists and songs don't have the bass recorded at the same level as the rest of the song (think: The Doors, Bob Dylan). The problem with the Epicenter is that is does one thing: it "adds" bass around a certain frequency or "Q." If you've ever seen an amp with a "Q" setting, that's what it is. The Epicenter's Q is 69Hz and adds bass around that frequency depending where the knob is. SO...it doesn't add bass "evenly" through the sub frequency response range. It sounds sloppy when cranked for that reason. Damping factor is randomly tested...there is no standard, and therefore a pointless spec. Regulated vs unregulated power supplies...the regulated PS pulls the same amount of current and creates the same amount of output at all input voltages. Unregulated does the opposite. Want full output at ~12.8V @ rest? Regulated. Be prepared with your battery/batteries without the car running. Unregulated means the amp will make, say, 200 watts @ 12V and 400 watts at 14V. Feed it more juice, make more power There may be a formula, but I'll leave that to the experts since I hate math Wowwwwwwwww...sorry for the walls of words

Get rid of the Epicenter, it will do you zero benefit and actually make things worse. Completely inaudible difference. An amplifier for 1ohm will be cheaper to get the same power though. As long as it is a quality brand an amplifier is an amplifier IMO. I'd rather buy a well made piece used than a new budget brand though. As for best choice of SQ, that is more box, install, and setup related than driver. Having a sub that is optimized for a sealed enclosure would do you better, but with enough experimenting you can get that to work in a ported and still blend with your fronts.

I agree with BASSmaster (everytime I see that handle this week in particular I picture Kevin VanDam). I have never had a system where I ran the stock phasing on all drivers. You may have an anomaly that could easily be resolved by switching the phase on one of your mids. That being said, I also think your path is fine. If you are truly wanting more in the midrange a dedicated 3" driver will be "enough" although if you really want to wang you may have to have a second setting on your eq to roll it off higher in the passband to allow it to play louder. Of course you can compensate by rolling the midbass up a bit, but if you are going to really optimize the system for output mostly it would require a midbass than can extend a bit more than some. Glad you see the madness in my questioning...and the reason that the T&C's are so specific. It is WAY easier to help someone when they really let you know what they have and what they want to do. That being said, try switching the phase on a midrange and let us know what happens. In reality I would try every combination of phase with the front comps and see what sounds best. Before doing it I'd flatten any eq you have applied and start flat. Re-adjust after testing phase and report back

Amusingly this topic is about a sub amp and that is absurd if you truly are so psycho-acoustically challenged that you think you can hear a difference. Of course I'd say the same about a highs amp in your car as well.

Try the stuff I said

Look through the cooling vents where the cast frame meets the motor structure. The coil configuration and any options such as copper coil and BP will be written on the coil former.

I apologize, I shouldn't have used Loud or Definition. Been on a tear today on the phone and shouldn't type while I am on the phone, but I am super ADD and have to do two things at once. Sorry. Meant to say description of said output from your previous post. IE, was trying to refer to your half the output statement. Some background on the comps, the install, the power, the frequencies where "half" is, how you determined it was half and so on, what happens when you turn them up to compensate and so on. Last thing I want to do is recommend something and have it not do what you want.

HA HA speaker recommendations??? Was waiting to try and understand your definition of loud.

What wasn't clear?

could you post up some pictures of how you made your doors ? and how did you cross the 2 way ? have you tried playing with the righthand kick/mid out of phase ? quite possibly you're lacking output because the kick/mids are not playing at full potential .

ORLY???? Your an asswipe.

This is a very busy weekend for all, Im sure. Wait a hot minute. We'll get there.

hey i don't know if you have seen this chart before but here you go! I seen this chart maybe a year ago and when nathan mensioned something about a chart i though of this one! and here is the original link! http://www.4xspower.com/downloadables/xspower_flyer-left.jpg

Opinions may differ, the laws of physics however do not. And ultimately that's what we are discussing; the laws of physics, not opinions. It doesn't matter how fancy the equipment connected to each end of the cable is. It doesn't matter how golden eared someone thinks they may be. The laws of physics dictates that the LCR properties of a cable will determine how that cable affects the signal. If there LCR properties of two cables are close enough as to not audibly alter the response, they will sound identical. The likelyhood of a non-damaged RCA cable having a significant enough difference in the LCR properties to affect the signal is remote unless an electric circuit is added to the wire to intentionally alter the response as some extremely high priced speaker wire manufacturers do. But at that point you are no longer comparing the wire itself and instead comparing wire to a passive equalizer.....that could be accomplished with cheap wire and the same passive elements. Although I'm not sure why anyone would ever want to purchase a wire that intentionally alters the signal, but they do. And you do realize directional is only directional if there's a drain wire used for noise reduction, right? If directional cable is claimed to be directional because of "how the crystals in the wire are oriented" or "how the wire is drawn" or some other marketing bullshit it's exactly that; bullshit. There is a saying I like from a pretty smart fella on another forum...... There are 3 great mysteries scientists are facing in modern physics; 1. A unified theory of gravity and sub-atomic particles, that finally comprehends and unites quantum mechanics and general relativity. 2. Dark matter and dark energy, that seem to be causing the rate of expansion of the universe to be increasing. 3. How the hell to pass a 20kHz audio signal through a cable.

It's not true, because "better grade" (i.e. fancy and expensive) RCA's are unnecessary anywhere in the system. I agree, but i know people who would object that opinion lol. As long as you keep your RCA's away from your power wires you should be just fine. They can object all they want.....they would still be wrong And there's nothing wrong with RCA's next to the power wire. That's an old myth.

nah idk about that with my old setup i disconnected the ground first many times and never had a problem with the t2k Very unwise, i've smoked an amp this way. my ground rocked undone and my amp arced on my chassis.

nah idk about that with my old setup i disconnected the ground first many times and never had a problem with the t2k Wow. Smart bub.

You should never unhook the ground with the power wire still attached, let alone then hook the ground back up to the amp. If it wasn't smoked before, it most likely is now.

i could ask you the same??

Sold my btl18 looking into getting 4 15 Havocs here or my dimensions. Can I get 4 15's in these dimensions 35Wx38Lx35H thanks for the help ahead of time

The metal the coil is made of does not determine the enclosure it will work in.

Actually the boxes on ebay from sonix whatever, are tuned at a decent frequency. I would just be more worried them about having enough port area.

Thats funny. Are you trying to tell me that a higher priced amp will improve my SQ? Let's say I replace my MB Quart with a very popular Sundown.....will it sound any better?

Yeah i have removed the ground wire before and it wasnt a problem and hasnt been for years that I know of, never damaged an amp or anything else by removing the ground first and then putting it back.

Section's been her for 3 days and no intros. For Shame. I'd like to see intro's and stats on your members.