why is efficiency so critical

[T3mpest 10+ year member]

Just a question, I like phsyics but have never really researched speaker design, so if I'm missing a fundamental concept correct me, please. I have a problem relating effeciency and excursion. I have a theoretical scenario.

Ok, I am assume that if we had 2 speakers that were equal in all ways but senativity and Xmax. (IB install for simplicity) If driver A is 3db's more sensative than driver B, that means it is moving 2x as far with 1 watt of power. Since cone area's the same, the only other factor in moving air is excursion, we now have a direct correlation between effeciency, excursion, and SPL between the 2 drivers. As we continue to add power to each we'd get an increase in excursion between the 2 drivers. In this case, driver A would always be louder than driver B. Both subs would hit the RMS limit, but no matter how far driver B was moving, it coudlnt' be moving further than driver A due to effeciency being lower. Now if driver B had a higher power handling it could be louder, correct? If it had 2x the power handling it could actually hit X-max and tie with driver A, assuming it's final Xmax was indeed 2x that of A, if not it would be wasted as heat....

Seems kinda weird, I'd like to see a real world comparison between a Avalanche and a Aresenal for just this reason... Similar in power handling, but differnent effeciency's and excursion limits. However since the power handling is the same and effeciency is higher on the arsenal, it would appear the avalanche could never be louder. Assuming that RMS on the aresenal is needed to reach the 20.5mm xmax. The avalanche could never move that far being less effecient on the same power much more and you'd fry a coil... Looking at a problem in that light it seems to really show just why people say to not judge a sub by it's RMS, since that's just the thermal power handling of the VC. This simplistic view of a loudspeaker has too many flaws to be useful.

 

[audiolife 5,000+ posts]

ok im understanding that efficiency is not the only parameter that is important... so when you all are deciding on a sub what parameters are you looking most closly at? say, for an sq setup, and for an spl setup?

determin what way you are leaning towards sq/spl/sql. how much room you are willing to give up. then how much money you are willing to throw at it (sub cost, box cost, power if you already an amp or not and remembering if you go huge you need power alt and a good battery to make huge power). before anyone can say one thing vs another you as the buyer has to make a few choices. it doesnt do any good to tell you a 15" in a big ported box is what you want only to find out you drive a miata ... your system is your system its an extension of what YOU want/can do.

 

[Raven 10+ year member]

ok im understanding that efficiency is not the only parameter that is important... so when you all are deciding on a sub what parameters are you looking most closly at? say, for an sq setup, and for an spl setup?

Parameters? I don't look at them at all. More important to me are how the real world takes to them. Back in '04, after fussing for weeks over T/S parameters between the IA 187, Type R, and Adire Shiva, I finally hit the forums and just read about all of them. A few videos and threads by average guys starting with something like "OMG they kick a$$!!!" later, I picked up a pair of 187s. My simple approach rewarded me greatly. I could pimp IA187s all day. I loved those things.

This is one of the reasons I totally disapprove of the Type R thread. A few competitors installer's scores of 150 that almost noone else will ever see and suddenly it's God's gift to the hobbyist. Noone ever talks about how they fare in a less than pristine install or even with their rated power. I won't get into this too much since I haven't visited that thread in months.

 

[snoopdan 5,000+ posts]

speaking of spl comps what is tc gonna be entering in dbdrag this year >? Anything? Kyle do you all beleieve in dbdrag or are all of your subs just good on paper?

Actually, I hope im net letting the cat out of the bag so to speak, but I believe Kyle will confirm that i'll be getting a "NEW" version of one of their upcomming SPL subs based on a NEO motor to compete in the DB Drag World Finals / MECA Kentucky State event comming next month. Im sure Kyle would like to get one of the SPL monsters that TC is cooking up actually out in the lanes to show its stuff beyond how it looks on paper. In fact my Jeep is all ready for that sub to show up at my door any day, right Kyle //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

Im sure Kyle will agree this will prove the effeicency of their new drivers just fine //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[boomanchu]

funny thing is that boomanchu is actually TC Sound's biggest fan boy Supa C in disguise.....//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif
//content.invisioncic.com/y282845/emoticons/sneaky.gif.7189749b3a3f769e8815b47e8ae87f88.gif

//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

go eat a sack of dog poo

 

[mrray13 10+ year member]

the funniest thing about this thread is all the people spouting off about real world this and real world that...and 98% of this particuliar isn't about real world at all. it's bandwagon hype and nothing else....teh eDuh's, teh mags, the xxx's, the mags again, IA"s, rl-p's, the ava's...and now the FI's....1, maybe two guys test them...and bang!!! it's on. not too mention all the previous discussions of t/s parameters here...

loyd, jim, warbleed, ramos, dave and a select few others have been about real world from the get go. now, all of a sudden, this forum only cares about real world testing? wtf ever. loyd has really gone outa his way to start bringing real world testing from a respected source to the forefront and i applaud him for that. but the rest of you big mouths need to go back and reread this entire forum. because it's NEVER been about that before. only my bandwagon is bigger then yours. oh, and i've never heard, owned, or touched the bandwagon product i'm on either..but the t/s parmeters tell me it's the best!!

i guess the new bandwagon here is RWT..real world testing....and everyone is doing it...

end of my rant....

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee //content.invisioncic.com/y282845/emoticons/peace.gif.2db28b618ed8d1964ebbe2f5021d2c39.gif

whatever....

 

[cleanerupper 10+ year member]

Well I don't know why you guys are hating, but TC Sounds makes some damn good subs. Surely somebody over there must know their stuff.

 

[newusername 10+ year member]

Ok, I am assume that if we had 2 speakers that were equal in all ways but senativity and Xmax. (IB install for simplicity) If driver A is 3db's more sensative than driver B, that means it is moving 2x as far with 1 watt of power. Since cone area's the same, the only other factor in moving air is excursion, we now have a direct correlation between effeciency, excursion, and SPL between the 2 drivers. As we continue to add power to each we'd get an increase in excursion between the 2 drivers. In this case, driver A would always be louder than driver B. Both subs would hit the RMS limit, but no matter how far driver B was moving, it coudlnt' be moving further than driver A due to effeciency being lower. Now if driver B had a higher power handling it could be louder, correct? If it had 2x the power handling it could actually hit X-max and tie with driver A, assuming it's final Xmax was indeed 2x that of A, if not it would be wasted as heat....

Here's a wrench for ya....

Driver A may be 3 dB more "sensitive" or "efficient" at a particular frequency than Driver B with 1W or 2.83V or however you wish to rate it.

But what happens at 100W as excursion increases? What happens when Driver A suffers from thermal power compression, Re doubles causing Qes and Qts to double with it? What happens when driver A starts to move out of the gap and BL drops, causing further changes to Qes/Qts and causing BL based distortion? What happens when Cms changes? Power compression (be it Re, BL, or Cms based) is a real problem and throws these efficiency ratings out the window.

Keep in mind that the only parameters that truly matter are Re, BL, Cms, Mms, and Sd. Every other parameter is drawn from these 5 basic parameters. The big issue with the use of t/s parameters (whether it is with people online or through simulation) is that there is a wide spread lack of understanding how these interact in a real world application with large signal applications.

Sensitivity and efficiency tell you very, very little other than what happens at whatever power level they rate it at, and includes absolutely NOTHING about the enclosure; for EVERY subwoofer, the enclosure plays a larger factor in efficiency and any excursion at a given frequency.

Loyd and Jim could not be more correct.

Cheers,

Neil

 

[Freakshow 10+ year member]

//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gifgo eat a sack of dog poo

sorry for blowing your cover //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[Johnny Drama 5,000+ posts]

My view on the matter...(Someone correct me if I am wrong)

Efficiency is the measure of 1w/1m not 2.83v or whatever(that would be sensitivity IIRC). Now with that laid down, efficiency will also change with the note measured at.

If Sub A has an 89db efficiency with 1w/1m at 50hz

Sub B has an 87db efficiency with 1w/1m at 40hz

If you take the IB situation as talked about in this thread. At 50hz sub A "should" be louder. At 40hz however, sub B "may" be louder depending on the actual efficiency of A at that note. Therefor you can not say that A will "always" be louder.

During a competition or even on music you wont be able to say that sub A will always be louder at every level or note. If your car and/or box peaks where sub B has the highest efficiency over sub A, again you can not say that A will "Always" be louder.

Finally, As with anything in the audio world. Actual power, efficiency, and all other parameters of any equipment will change in car, in house, in the box, power, and with any change to the environment such as, but not limited to heat or voltage.

 

[CBFryman2 5,000+ posts]

My view on the matter...(Someone correct me if I am wrong)
Efficiency is the measure of 1w/1m not 2.83v or whatever(that would be sensitivity IIRC). Now with that laid down, efficiency will also change with the note measured at.

If Sub A has an 89db efficiency with 1w/1m at 50hz

Sub B has an 87db efficiency with 1w/1m at 40hz

If you take the IB situation as talked about in this thread. At 50hz sub A "should" be louder. At 40hz however, sub B "may" be louder depending on the actual efficiency of A at that note. Therefor you can not say that A will "always" be louder.

Which is the main problem with SPL ratings. If there was a standard frequincy for each type of driver and they did a real world anecho testing 1w/1m then it would be a far greater judge. Drivers that are rated at 89dB 1w/1m correctly could prove to be 70dB 1w/1m at 40Hz... in a range where it actually will play.

Prime example would be audiobahn. Not only do these drivers have a 98dB 8w/1m but they also have this uncanny ability to play louder above 100Hz as well, where less displacement and power is needed to get equally loud.

And jsut choosing one frequincy would be unfair for some drivers. Average for a frequincy range would be better.

But in the end a higher efficency will yeild a higher SPL number at some point as it should be the loudest it can get...no particualr range or frequincy (IIRC). But that doesnt matter once you put it in a box in a car with more than one watt and most importantly, in a given frequincy range.

So what am I saying in my rableing? Both points of viewing the issue are correct. Which is more correct is another issue to be discussed.

 

[bigbassman Premium Member]

now the thread is getting hot!

Loyd L.

 

[newusername 10+ year member]

My view on the matter...(Someone correct me if I am wrong)
Efficiency is the measure of 1w/1m not 2.83v or whatever(that would be sensitivity IIRC). Now with that laid down, efficiency will also change with the note measured at.

If Sub A has an 89db efficiency with 1w/1m at 50hz

Sub B has an 87db efficiency with 1w/1m at 40hz

If you take the IB situation as talked about in this thread. At 50hz sub A "should" be louder. At 40hz however, sub B "may" be louder depending on the actual efficiency of A at that note. Therefor you can not say that A will "always" be louder.

During a competition or even on music you wont be able to say that sub A will always be louder at every level or note. If your car and/or box peaks where sub B has the highest efficiency over sub A, again you can not say that A will "Always" be louder.

Finally, As with anything in the audio world. Actual power, efficiency, and all other parameters of any equipment will change in car, in house, in the box, power, and with any change to the environment such as, but not limited to heat or voltage.

If calculating efficiency using the t/s published formula, it is relatively easy to see efficiency at a given frequency. If efficiency is increased (through a decrease in Mms or an increase in BL), then Fs is also raised. Theoretically, Sub B with a lower efficiency rating will actually be more efficient at lower frequencies.

But still, all that is meaningless in a powered, in enclosure application.

Neil