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HCCA
05-11-2007, 07:26 AM
I came across this a while back. I was looking into the idea of a 3-way system, up front. Most mid-bass drivers have somewhat low power handling, IMO. This one seems to be really good, by the performance numbers...though a bit pricey. Anybody use these, or have a good three way setup that would like to comment? http://criticalmassaudio.com/catalog/index.php?act=viewProd&productId=5

MiniVanMan
05-11-2007, 10:32 PM
That driver ran at 200 watts won't really be any louder than a 4 ohm driver at 100 watts, and it's expensive as hell.

The Peerless SLS 8's are great, and the Dayton RS225s can handle quite a bit of power. The Seas L18, or L22 will rock your world as well. All those options are well under $100.00 each.

Not to get too technical, but an 8 ohm driver running off of 100 watts will have roughly the same output as a 4 ohm driver running off of 200 watts. Given all other things being equal. It's a function of sensitivity, not power handling.

ARSkemp
05-11-2007, 10:45 PM
Not to get too technical, but an 8 ohm driver running off of 100 watts will have roughly the same output as a 4 ohm driver running off of 200 watts.

no

a 100w speaker @ 4ohms will be equal in loudness to a 100w speaker @ 8ohms (all else equal)

squeak9798
05-11-2007, 10:54 PM
That driver ran at 200 watts won't really be any louder than a 4 ohm driver at 100 watts, and it's expensive as hell.

The Peerless SLS 8's are great, and the Dayton RS225s can handle quite a bit of power. The Seas L18, or L22 will rock your world as well. All those options are well under $100.00 each.

Not to get too technical, but an 8 ohm driver running off of 100 watts will have roughly the same output as a 4 ohm driver running off of 200 watts. Given all other things being equal. It's a function of sensitivity, not power handling.

You are assuming the driver with the higher impedance automatically has a sensitivity 3db higher than that of the other driver, which isn't inherently true especially if we are comparing different drivers.

So no, your comparisons do not hold true.


That said I can't disagree with your speaker recommendations :) And I would agree that the speaker linked by the thread starter would have to be pretty spectacular to warrant that price. I have a hard time believing that the drivers you mentioned wouldn't offer just as good if not better performance at a much lower price.

MiniVanMan
05-11-2007, 11:15 PM
You are assuming the driver with the higher impedance automatically has a sensitivity 3db higher than that of the other driver, which isn't inherently true especially if we are comparing different drivers.

So no, your comparisons do not hold true.




I said all else being equal. I know there are variations.

Generally (key word again) speaking, an 8 inch driver with a higher overall sensitivity, will a lot of times have lower low end capability. A key difference to note when dealing with pro audio drivers. Just because it's 8" doesn't make it a low end beast. Pro Audio drivers are super sensitive, and loud as a result, but you're not going to get the same low end extension as a home audio, or car audio driver designed for low end duty.

So, when somebody asks for advice on a MIDBASS driver for a 3 way, I can assume a number of things. First is they want low end extension. Second is, they want output. Third is, they're not going to care much about top end extension (unless matching with domes). Now, the question comes as to how low the person wants this particular driver to go. Just 80 hz? I can recommend some 8" drivers that have great overall sensitivity, that will be louder at any impedance level than an 8" that digs an octave lower.

I know, when I point this stuff out, that I'm going on assumptions, and I should probably be clearer. I'm on a personal mission though to debunk this myth that to get louder you need lower impedances, and more power. What you need is more power, and higher sensitivity (at any impedance). We're pretty limited by physics though.

MiniVanMan
05-11-2007, 11:20 PM
no

a 100w speaker @ 4ohms will be equal in loudness to a 100w speaker @ 8ohms (all else equal)

Are you saying when "giving" each speaker 100 watts, the 8 ohm and 4 ohm will be equal in output? That is not correct. All else being equal.

http://www.diymobileaudio.com/forum/showthread.php?t=31

bdavies11
05-12-2007, 01:31 AM
Are you saying when "giving" each speaker 100 watts, the 8 ohm and 4 ohm will be equal in output? That is not correct. All else being equal.

http://www.diymobileaudio.com/forum/showthread.php?t=31

Um yes he is correct.

He is saying that a 4 ohm driver receiving 100 watts @ 4 ohms will have the same output as an 8 ohm driver receiving 100 watts @ 8ohms (all else equal). ;)

MiniVanMan
05-12-2007, 02:04 AM
Take an example like the RS180. It comes in both a 4 ohm and an 8 ohm version.

Take an amp that does say 100 watts at 4 ohms, and 50 watts at 8 ohms.

Take both drivers and run them subsequently on the same amp. Both drivers will have relatively the same output.

Now take the 8 ohm driver and put it on an amp that does 100 watts at 8 ohms and you will have a 3 db gain over the 4 ohm.

In order to raise the impedance you need to lengthen the wire wound around the coil. To go from 4 ohm to 8 ohm you need to double it. That causes an increase in inductance (double). Given the same magnet strength, you just doubled your BL. That will equate to an increase of 3 db sensitivity. Higher impedance, higher sensitivity. That means more output with less power. Much more efficient.

Now a real benefit, is when you go from 4 ohm to 8 ohm, the power will not be half. To say so, would be saying that you have an amp that has 100% efficiency as the load drops.

Stop thinking in terms of impedance, but rather sensitivity.

bdavies11
05-12-2007, 03:24 AM
Take an example like the RS180. It comes in both a 4 ohm and an 8 ohm version.

Take an amp that does say 100 watts at 4 ohms, and 50 watts at 8 ohms.

Take both drivers and run them subsequently on the same amp. Both drivers will have relatively the same output.

Now take the 8 ohm driver and put it on an amp that does 100 watts at 8 ohms and you will have a 3 db gain over the 4 ohm.


Um, i'm not quite sure how to put this so ill just put it...

That is incorrect. :uhoh:

bdavies11
05-12-2007, 03:40 AM
Think about it bud, Your basically saying that the higher impedance drivers are more efficient. If that were true we wouldnt need 63980938 watts to get loud.

Again, If that held true, we could simply buy a 64 ohm driver and give it 6.25 watts @ 64 ohms and it would be just as loud as the 2ohm driver getting 200watts @2 ohms. :rolleyes:

MiniVanMan
05-12-2007, 12:55 PM
Think about it bud, Your basically saying that the higher impedance drivers are more efficient.

That is EXACTLY what I'm saying!!!! I'm sorry you're stuck in your car audio dogma. It's an absolute FACT that when you increase the coil length within a magnetic field you get higher sensitivity. By increasing coil length, you get higher impedance.

I will go as far as to say, there are mechanical properties of every driver that need to be overcome before any real output is realized. That makes a 4 ohm driver fairly appealing when dealing with low power situations like using head units (especially stock) to power a speaker. You get more power to overcome the initial mechanical properties of the driver. That's why Mms is a factor of sensitivity. The stiffer your suspensions, and the heavier your cones (which comes with a lot of your ultra stiff cones like the RS series drivers from Dayton), the more power you'll need to overcome them before you realize output gains. High Qts drivers generally have stiffer suspensions. High Qts drivers are desireable in a car because of a more controlled low end in an infinite baffle situation. You lose a little low end capability, but your overall sound in the midbass region will be more controlled.

When you have a driver such as this, sensitivity can suffer. That's when we start to hear about things like, "this driver ***** up power, and wants more". Being limited by a 12 volt source, power at 8 ohms is harder to come by. This was especially true in the early days of car audio. It was a give and take situation. We don't have as much power to work with, and I can get decent output out of a 4 ohm driver, and since I'm stifled by the mechanical properties of these drivers. I'll use a 4 ohm driver and give it as much power as available.

Now that we have more advanced circuit topologies, and much more efficient amplifiers, we get more power for our initial 12 volts. So, in a high powered application, 100+ watts, it's actually better overall to use an 8 ohm driver. More efficiency, cooler amps, cooler speakers. Less loss = more efficiency all around.

Want to keep going? I can pull out the book.

bdavies11
05-12-2007, 02:20 PM
Ok then... Im going to go buy myself an amplifier that puts out .000000000000000000000015 watts @ 837,489 ohms for 14 cents (since it only puts out .000000000000000000000015 watts), hook it up to my 4" sony 837,489 ohm speaker and go shatter pioneers 180+ spl record with it. :rolleyes:

helotaxi
05-12-2007, 02:30 PM
Think about it bud, Your basically saying that the higher impedance drivers are more efficient. If that were true we wouldnt need 63980938 watts to get loud.

Again, If that held true, we could simply buy a 64 ohm driver and give it 6.25 watts @ 64 ohms and it would be just as loud as the 2ohm driver getting 200watts @2 ohms. :rolleyes:

That's exactly what he's saying. Things to consider: the sensitivity rating that you normally see is db @ 1m @ 2.83v. 2.83V equals 1 W into an 8 ohm load. It equals 2W into a 4 ohm load and 4W into 2 ohms. If 3 speakers all have the same sensitivity rating of 93dB @ 2.83V/1m and one is 8ohm, one is 4 ohm and one is 2 ohm, which is more sensitive? The 8ohm driver is only getting 1W and is creating the same amount of sound as the other two getting 2x and 4x the power respectively. It takes power to make power and as impedance decreases and current increases, resistive losses in the amp increase. Running an 8 ohm driver would allow the amp to run cooler and draw less power from the electrical system of the car compared to the same amp trying to get the same output from a 2 ohm driver with the same rated efficiency. Factor in that the amp will probably be able to produce more voltage into the higher load and the 8ohm driver will probably get louder overall as well.

This is all true for mid/high freq drivers. If you want the driver to play lower, it gets a lot more complicated because cone excursion away from the rest position where Bl is strongest changes Bl and all the other driver parameters. The larger the excursion, the larger the change. Mid/high freq drivers barely move at all and their motor strength remains nearly constant across its power and freq range.


Ok then... Im going to go buy myself an amplifier that puts out .000000000000000000000015 watts @ 837,489 ohms for 14 cents (since it only puts out .000000000000000000000015 watts), hook it up to my 4" sony 837,489 ohm speaker and go shatter pioneers 180+ spl record with it.

You are grossly over simplifying a very complex situation that you clearly don't understand. Let me know how that works out for you.

bdavies11
05-12-2007, 02:30 PM
http://www.epanorama.net/documents/audio/speaker_impedance.html

Impedance and effiency

Let's look at the following situation: Take an 8 ohm speaker and wind twice the length of wire onto the voice coil. The resistance woul go up, for sure, but because there is no more wire in thegap, the electromagnetic couping coefficient, the Bl product, would also go up. And you would have, as a result, a 16 ohm speaker with essentially the same efficiency as the 8 ohm speaker, all other things being equal.

Or you could design a speaker with both a higher impedance (longer wire in the voice coil) AND a larger magnet assembly with higher flux density in the gap and get a higher impedance driver with higher electro-acoustic efficiency.

Or you could design a higher impedance driver with a stronger magnet and a lighter cone and get even more efficiency.

The point is, the rated impedance IS NOT the same as the efficiency, nor is there any direct correlation between the two. Efficiency of a given direct readiator driver is determined by the folowing relationship: l

MiniVanMan
05-12-2007, 03:12 PM
http://www.epanorama.net/documents/audio/speaker_impedance.html

Impedance and effiency

Let's look at the following situation: Take an 8 ohm speaker and wind twice the length of wire onto the voice coil. The resistance woul go up, for sure, but because there is no more wire in thegap, the electromagnetic couping coefficient, the Bl product, would also go up. And you would have, as a result, a 16 ohm speaker with essentially the same efficiency as the 8 ohm speaker, all other things being equal.

Or you could design a speaker with both a higher impedance (longer wire in the voice coil) AND a larger magnet assembly with higher flux density in the gap and get a higher impedance driver with higher electro-acoustic efficiency.

Or you could design a higher impedance driver with a stronger magnet and a lighter cone and get even more efficiency.

The point is, the rated impedance IS NOT the same as the efficiency, nor is there any direct correlation between the two. Efficiency of a given direct readiator driver is determined by the folowing relationship: l

That's what I've been trying to tell you. But all other things equal, a 4 ohm driver still has to have a cone, suspension, magnet, etc. All other physical properties are still there. So, when increasing efficiency as detailed in your link, a byproduct of that is an increase in impedance. It is a byproduct.

You have a flux field in the center of your magnet. It's a fixed diameter, so you only have a fixed amount of room to work with. Take that magnet, and put a 4 ohm coil in there. Depending on the winding of the coil will dictate the inductance of the coil. The inductance will determine how it interacts with the flux field. The impedance is just a product.

I'll quote this next part.

If you take a given driver, and simply swap out voice coils, you end up with more efficiency as you increase the impedance. Take a voice coil, say 2" diameter, 1" winding length, 24AWG 4 layer, and swap it with a 2" diameter, 1" winding length, 27AWG 4 layer, and you double the impedance, but the efficiency also goes up - less mass and better packing density."

It's because the moving mass has dropped, and if desired - because of the thinner wire diameter which packs in tighter - you can put more layers in the voice coil and potentially raise the BL."

You didn't do anything to debunk anything I said, or Helotaxi said. You proved it. Now tell me, how do you increase the efficiency, or even keep it the same, of a speaker by lowering it's impedance, knowing that in order to do so, you have to unwind the coil?

What don't you get?


http://www.epanorama.net/documents/audio/speaker_impedance.html


Or you could design a higher impedance driver with a stronger magnet and a lighter cone and get even more efficiency.



Hmmmm, sounds like a 16 ohm pro-audio driver. Gee, I wonder why they would do that?

bdavies11
05-12-2007, 03:48 PM
I understand what your saying but your also implying that anytime you double the impedance for any driver your also increasing the sensitivity by 3db's which doesn't always hold true.

helotaxi
05-12-2007, 04:24 PM
All I've ever said is that if two drivers have the same sensitivity rating @ 2.83V/m, the driver with the higher impedance is actually more sensitive watt for watt. As a result it will usually get louder than the lower impedanc driver off the same amp and the amp will place less of a strain on the car's electrical.

MiniVanMan
05-12-2007, 04:41 PM
It's a generalization, and no different than saying you get double the power going from 4 ohm to 2 ohm with an amplifier. There are variables in every situation, but they're exactly that, variables. Variables affect everything. There's no magic product that takes all variables out of the equation. The same variables that affect an 8 ohm driver, will affect a 4 ohm driver. There are certain constants though, and they can be planned for. With those constants we can come to some fairly valid conclusions. It's an exercise in compromise when dealing with audio drivers. So while it may not be always true that a 3 db gain in efficiency will be realized, there will be a gain. If only 2 db, or whatever.

Unfortunately, marketing departments have too much say in how a speaker will be presented to the public, and how it should be engineered. An 8 ohm speaker will not sell on the general market because of the fallacies, and myths surrounding car audio. Even though it has definite advantages.

It's much more lucrative to put a girl in a bikini in front of a car holding a speaker and have a caption saying "MORE POWER", than having a fat, sweaty engineer holding a speaker and a tube of KY saying, "MORE EFFICIENCY".

There are advantages to 4 ohm drivers, they're just not the advantages that car audio marketing departments really care if you know. Nor do they want to explain them.

So, the argument, is, and what started this, was not to look at power, and impedance, but rather efficiency. That just because it would take 200 watts at 2 ohms wouldn't make it louder than a 4 ohm driver at 100 watts, or 8 ohm at 50 watts. That is doing the basic math. Yes there are assumptions in there, and I've explained those assumptions, but the basic point is to get away from thinking in the terms of more power, less impedance.

squeak9798
05-13-2007, 05:49 PM
So, the argument, is, and what started this, was not to look at power, and impedance, but rather efficiency.

You keep saying that....but so far all I've ever seen you mention is impedance....

Let's go back to some of your first comment;



That driver ran at 200 watts won't really be any louder than a 4 ohm driver at 100 watts,

YOU DO NOT KNOW THIS.

Where is your reference to efficiency? All I see is assumptions based solely on impedance.

You are assuming that another 4ohm driver will have a higher sensitivity....THIS WILL NOT INHERENTLY BE TRUE.

You can't say "well I meant if all else was equal" because that driver is not available in 4ohms, so you WILL NOT have the opportunity to compare the two different drivers "with all things equal".

You CAN NOT make an assumption of efficiency or output level of driver A vs driver B based solely on impedance, as you are obviously attempting to do.

Carrying on;


Not to get too technical, but an 8 ohm driver running off of 100 watts will have roughly the same output as a 4 ohm driver running off of 200 watts. Given all other things being equal.

You are again making the HUGE assumption that "all else will be equal". This will happen....hmmm......hardly ever. Especially when comparing two completely different drivers.


Generally (key word again) speaking, an 8 inch driver with a higher overall sensitivity, will a lot of times have lower low end capability.

Hoffman's Law dictates that in order to increase efficiency while reducing low frequency extension, the driver would require a substantially larger enclosure.....not practical in most applications. Most times a higher efficiency driver will lack in low end compared to a driver with lower efficiency.


I'm on a personal mission though to debunk this myth that to get louder you need lower impedances, and more power.

Great!

But you need to provide more thorough information and stop making so many assumptions, especially when they are based solely off of impedance.



Take an example like the RS180. It comes in both a 4 ohm and an 8 ohm version.


Lets.

Using the T/S parameters listed on PE's product page;

4ohm:
SPL = 112+10*LOG(9.64*10^(-10)*40^3*22.9/.48) = 86.69db

8ohm:
SPL = 112+10*LOG(9.64*10^(-10)*38^3*24.9/.47) = 86.48db

Only .2db difference, and that's actually in favor of the 4ohm driver.

If you use the T/S parameters listed on the "Exported CLIO" page;

4ohm:
SPL = 112+10*LOG(9.64*10^(-10)*38.32^3*22.59/.49) = 85.98db

8ohm:
SPL = 112+10*LOG(9.64*10^(-10)*40.26^3*24.35/.49) = 86.95db

Only 1db difference in favor of the 8ohm driver.

And if you use the T/S Params Zaph measured for the 8ohm driver;
SPL = 112+10*LOG(9.64*10^(-10)*40^3*20.06/.5153) = 85.8db


Take an amp that does say 100 watts at 4 ohms, and 50 watts at 8 ohms.

Take both drivers and run them subsequently on the same amp. Both drivers will have relatively the same output.

Looking at the above, I fail to see any sign that the 8ohm driver is actually 3db more sensitive than the 4ohm version. At best, so far, it has a sensitivity that's 1db greater......and that's only if we use the parameters that best suit the point you are trying to make.

Just a few more examples, lets check out madisound a little bit here too....

Vifa MG18WK09 using manufacturer stated parameters.

4ohm;
SPL = 112+10*LOG(9.64*10^(-10)*36^3*41/.32) = 89.61db

8ohm;
SPL = 112+10*LOG(9.64*10^(-10)*34^3*45/.41) = 88.19db


Scanspeak 7" Revs using manufacturer stated parameters.

4ohm;
SPL = 112+10*LOG(9.64*10^(-10)*33^3*42/.38) = 87.83db

8ohm;
SPL = 112+10*LOG(9.64*10^(-10)*28^3*59/.44) = 86.53db


Vifa PL18W using manufacturer stated parameters.

4ohm;
SPL = 112+10*LOG(9.64*10^(-10)*37^3*25/.33) = 87.68db

8ohm;
SPL = 112+10*LOG(9.64*10^(-10)*38^3*25/.4) = 87.19db


First three I could find that were offered in both 4ohm and 8ohm, chosen at complete random.



Stop thinking in terms of impedance, but rather sensitivity.

Practice what you preach ?


That just because it would take 200 watts at 2 ohms wouldn't make it louder than a 4 ohm driver at 100 watts, or 8 ohm at 50 watts. That is doing the basic math. Yes there are assumptions in there,


Very large assumptions, especially when comparing two completely different drivers and even apparently when comparing the same model driver in both coil configurations looking at the figures I calculated above. So many assumptions that the statement alone doesn't really hold true at all in reality. You must compare the two drivers in question and NOT be making assumptions based off of theory, impedance and/or generalizations.

The units above would need some pretty large (and I would say unacceptably large) variances in stated vs actual T/S parameters to come even close to having 3db higher sensitivity.

MiniVanMan
05-13-2007, 06:33 PM
I keep mentioning impedance in context of the argument. If you're going to base your opinion on which driver to choose, and you choose a 4 ohm driver, or lesser impedance driver because it has a lower impedance, and you can deliver more power to it, that is not making an educated choice, and you're making that choice for the wrong reasons.

Doing the math helps, and I appreciate that. At least you're making valid arguments, and they're pretty hard to argue with. You've also taken many of my statements out of context. If I don't mention impedance, then people don't know what the argument is.

Hoffman's Law states basically what I said, but you seem to quote me to refute me. You just wrote it in the inverse of how I stated it.

I don't care what driver you choose. I'm just tired of hearing the same comments about 8 ohm drivers.

I can do the math, and I can get the same sensitivity numbers you get. They're irrefutable. However, I know, when I put both the RS180-4 and -8 into my vehicle running off the same amp, the audible difference is negligible. Even metered, the difference is only around .5 db on average (I've done a couple of vehicles). I did that because I had a hard time in the beginning believing that an 8 ohm driver would do that. Now that's while delivering a good amount of power though, 150x2 @ 4 ohms. If it were just a 75 x 2 @ 4 ohms, I'd be hesitant to suggest an 8 ohm driver for reasons I stated before.

So, while, I have been overgeneralizing, I've been trying to debunk myths. Oversimplifying is also saying that a 4 ohm driver running off of double the power of an 8 ohm driver will be 3 db more sensitive. That's the argument I'm debunking.

So, yes, I have been making references to impedance, but that was in the context of the argument that for some reason the lower impedance will create a louder driver. It very well might. But YOU DO NOT KNOW THIS!! I can make the exact same argument the other way for every time somebody says I'm generalizing. Why is it okay to generalize with a lower impedance driver and not a higher one?

Maybe I should not have said, "will not". I should have taken the road of "not necessarily".

Even sensitivity numbers don't tell the whole story. They're a bit more accurate than impedance numbers. Zaph consistently shows T/S parameters to be quite a bit different than advertised in his testing.

So, you're right, I'm wrong. I should have just kept my mouth shut, and not even brought up the argument. I should just accept that those that don't want to know don't need to know. Making argument against generalizations with generalizations is not very scientific I admit. I am wrong on that. However, I find that when trying to reverse a line of thinking, throwing out equations, and a bunch of facts, figures, and technical data is not the best way to do that.

To show that generalizations, and arguments can be made for both sides promotes curiosity and critical thinking.

I can go on and on about various "gross" generalizations in car audio, and misinformation. Baby steps though.

Thank you for the equations, but even you must admit that they don't tell the whole story. It's car audio. It's very hard to predict how anything will react from car to car. We have to go on generalizations at times.

In other words, I don't know why we're arguing. Unless you have stock in 4 ohm drivers.

squeak9798
05-13-2007, 07:00 PM
I keep mentioning impedance in context of the argument. If you're going to base your opinion on which driver to choose, and you choose a 4 ohm driver, or lesser impedance driver because it has a lower impedance, and you can deliver more power to it, that is not making an educated choice, and you're making that choice for the wrong reasons.

Doing the math helps, and I appreciate that. At least you're making valid arguments, and they're pretty hard to argue with. You've also taken many of my statements out of context. If I don't mention impedance, then people don't know what the argument is.

It's not hard to state it properly.

Such as;

"Using a 4ohm w/ a sensitivity of 87db w/ 100w is the same as using an 8ohm driver w/ a sensitivity of 90db w/ 50w"

Had it been stated in that manor, I probably wouldn't have even responded in the first place :)


Hoffman's Law states basically what I said, but you seem to quote me to refute me. You just wrote it in the inverse of how I stated it.

Mmmm...then I must have misread what you typed.

After reading this comment, I have come to realize that by "lower low end capability" that you may have meant "less low end capability".

When I originally read the statement, I read it as "lower low end" referring to the driver extending "lower" (deeper, etc) in frequency and not "lower" as in decreased low end capabilities.


However, I know, when I put both the RS180-4 and -8 into my vehicle running off the same amp, the audible difference is negligible. Even metered, the difference is only around .5 db on average (I've done a couple of vehicles). I did that because I had a hard time in the beginning believing that an 8 ohm driver would do that. Now that's while delivering a good amount of power though, 150x2 @ 4 ohms. If it were just a 75 x 2 @ 4 ohms, I'd be hesitant to suggest an 8 ohm driver for reasons I stated before.

Then state it more closely to those statements.



So, yes, I have been making references to impedance, but that was in the context of the argument that for some reason the lower impedance will create a louder driver. It very well might. But YOU DO NOT KNOW THIS!! I can make the exact same argument the other way for every time somebody says I'm generalizing. Why is it okay to generalize with a lower impedance driver and not a higher one?

I don't recall anybody doing so in this thread :confused:

Original poster commented about the decent power handling of the driver...which 200w is a pretty high rating for any midbass driver regardless of impedance. That's when you came in with the "200w to that driver = 100w to a 4ohm driver"....which isn't necessarily true and is the statement or theory I think most of the people responding took issue with. You hadn't used the driver to make the same comparison you did above, and you made no reference to efficiency (which it's realistically around 87db, no more or less efficient than the drivers I listed previously).

So, I guess I'm not sure of how "that myth" was even an issue until you brought it up?

MiniVanMan
05-13-2007, 07:26 PM
So, I guess I'm not sure of how "that myth" was even an issue until you brought it up?

Because I'm overly sensitive (or my impedance is too high, and my coils are wound just a bit too tight) :hide:

This has been a good thread. Like I said, it's promoted critical thinking, and very much so on my part. Knowing something, and articulating it, in a manner that is understandable and correct can be difficult. Especially in a situation that has SOOOO many variables to begin with.

I'm reluctant to use hard data, as it doesn't tell a whole story. I'm reluctant to use personal experience, because it may not apply. I'm reluctant to use personal opinion, because as with anybody your opinion does not dictate truth. So, basically, you're screwed. It also leaves the subject WIDE open for the perpetuation of myths, that are, in the end, extremely difficult to debunk. Generalizations become the rule, especially in a forum that leaves communication as an exercise in patience. However, I'm not reluctant to jump right in, and throw myself to the wolves.

I guess the initial argument was that throwing more power into a 2 ohm load doesn't necessarily mean you'll get more output than a similar 4 ohm driver ran off of 100 watts. There are much cheaper options.

Oh and the reference to impedance was based, once again, on an assumption due to the OP posting a driver with a 2 ohm coil. The OP never stated that, but if he didn't see that to begin with, it's definitely something he should be made aware of.

HCCA
05-14-2007, 12:14 AM
Okaaaay....not what I was looking for, but good info, none the less. BTW, is minivanman also known as Jim Fultz? If not, nevermind. :rolleyes: I just made a guess by the vehicle listed.
OK, in reference to my original post. I will be running about 275w to my mid comps B/A Pro 60's. I will be running about 900w to a single B/A SPG555 sub. I was considering a midbass that would bridge the gap, and play down to 60hz. What power would you guys recommend I put to this driver, and what driver? Thanks to minivanman for your recommendations for drivers. (I have room for an 8" driver, with depth to 3 1/2". Well, sort of...I would have to make a baffle plate of 1" MDF to bush it out away from the door card.

One more thing, I had trouble with phasing on my last system running 3-ways up front. I used an Audio Control 24xs crossover (18db slopes). The midbass was in the factory door location, and the mid/tweets were mounted in the kicks. 50w/ea channel to all front drivers. I tried switching phasing of the wires in every conceivable way, but I had a major null in the 125-250 hz region. I couldn't equalize it out. It makes me worried about trying a 3way system up front, when a mid/ tweet combo did great in an earlier system. I know I F*ed up something in the installation, but could not figure it out before I sold the car. Still, I want good midbass in this install. :suicide:

MiniVanMan
05-14-2007, 11:19 AM
Nah, Minivanman is not named Jim.

Anyway, not really sure what your problem was last time. It could be any number of things. If your midwoofers were wired out of phase, that may have been the problem. That or they just didn't have enough power. Phasing between 2 woofers wouldn't normally account for a 1 octave loss, but stranger things have happened.

Anyway on to the future. That is an AWFUL lot of power you plan on sending those Boston comps. I'd say do the 275 watts to a midbass driver, and send 150-200 to your comps. That's still a ton of headroom. Especially considering the frequencies you're going to ask them to play. The less you ask them to dig deep, the less power you'll need to get good dynamics out of them. Bass takes power. At about 250 hz on up your power requirements dramatically decrease to get good dynamic sound.

What kind of vehicle is this going in?

A couple of ideas that come to mind for midbasses have been stated before. The L18RNX by Seas is a 7" driver totally capable of that given your doors are properly treated.

Nobody has anything bad, or even neutral to say about the Peerless SLS 8". They are some of the best midbass drivers available. They're not overly expensive, but they are deep, coming in at a little under 4".

The Dayton RS225 is wonderful midbass, and cost effective too. Comes in either a 4 ohm or 8 ohm version. The 4 ohm comes in at 3 1/2" deep. So that may be your best solution. They're under $50.00 a piece, and are really a nice detailed, and dynamic midbass.

Usher makes some fantastic extremely low distortion drivers. They're 8" 8955A would do very well, but has a HUGE magnet and is about $120.00 a piece. It's hard to say that you'll hear the distortion differences in a car, but I thought I'd throw it out there.

Personally, I think the RS225 will be fine for what you're asking them to do. For a few dollars more, if you can get the Peerless SLS to fit, then rock on with that bad boy.

HCCA
05-14-2007, 04:08 PM
Thanks for the reply. I forgot to mention that I tried crossing them at 250, 325 & 500. I settled on 250. As I said, I tried every conceivable combination of phasing, to no avail. (On the old system)
I am installing my new system in a 2002 Explorer. Actually, the power rating that I WAS going to be sending the comps was from a B/A GT28 amp, but I am going to use that for the subs. I am going to use a GT 24 amp for the mids. That should be closer to 200-250w/channel. They are rated to 150W, but I was told that they will handle 250W, all day long. We'll see. I can run a either of the two amps for the midbass, but it sounds like another GT28 should handle those. At 4 ohm (MB driver not yet known, I should be able to send it 200-250W, to match the mids. I can keep the gains down on the mids if needed to balance the system.
I will be adding ensolite to the whole vehicle, and some egg crate foam to the back of the speaker location as well. Just wondering how the MB's will work in freeair, at thhat power level.

helotaxi
05-14-2007, 07:18 PM
You had a pathlength suckout or a standing wave in the car in that freq range. That's pretty common and most every car will have a spot like that. Only real fix is to start playing around in the time domain.

HCCA
05-14-2007, 11:36 PM
Heliotaxi, I was suspecting a standing wave, but did not know what to do about it. I will be using an Apline 7909 for the head unit. I don't have much control over the time domain without getting into a whole other source unit, that incorperates a time alignment feature. Any suggestions?

MiniVanMan
05-15-2007, 12:00 AM
It's hard to do, but just angling the speakers as little as 15 degrees towards you can help dramatically. Some cars have nothing in between the two door mounting locations.

It's just another option, if you can make it work.

helotaxi
05-16-2007, 09:20 AM
It's hard to do, but just angling the speakers as little as 15 degrees towards you can help dramatically. Some cars have nothing in between the two door mounting locations.

It's just another option, if you can make it work.

If ii's a phase suckout rather than a standing wave though, aiming doesn't do anything to address the arrival time difference that cause the issue.

HCCA- try moving your head round a bit. If the sound changes noticably and fills in that void, you have an arrival time issue.

envengineer
05-16-2007, 10:00 AM
Not to fuel the fire in this debate, but often you do not need an 8 ohm driver to be 3db more sensitive in order to achieve the same output as a 4 ohm driver. This is because many (most?) amplifiers produce greater than 50% of their rated 4 ohm power at 8 ohms. (I'm not making an driver argument, rather an amplifier argument)

An example just to clarify my point: Take an amp rated at 200w @ 4 ohm, hook it up to an 8 ohm load, it may very well make 140w rather than 100.

You can see this in many amplifier ratings when comparing the 2 ohm and 4 ohm rating. Again using a 200w @ 4 ohm rating, often the 2 ohm rating is around 300w, not 400.

The doubling of impedance does not neccessarily mean halving of power.

BTW, I went with the SLS8s myself.