Non-linearity of air?

sedate wrote: What does bl have to do with output? I thought bl was a measure of motor force.. like.. it translates into cleaner sound and more woofer control.. not necessarily more output? What is the connection between bl and output?

It effects frequency response.  Here's a quote by my boss explaining how the parameters effect one another.  The last part of the quote will answer your question above:

"Vb is proportional to Vas (double Vas, double Vb). Vb is proportional to Qes squared (halve Qes, quarter Vb). This is for the same Qtc/alignment... And since Qes is inversely proportional to BL squared, if you double BL you cut Qes by a factor of 4, meaning the box volume for a given alignment is cut by a factor of 8.

Now, that is all well and good, but consider what Fb does in relation to Qts/Qes... Fb is inversely proportional to Qts, thus as you raise the BL, and lower the Qts, you raise the Fb accordingly. Double BL, cut Qts by a factor of 4, meaning Fb just jumped up 2 octaves!"

Steven Kephart

Adire Audio

haemphyst wrote: the "transient response" of the woofer. (I still hate using that phrase - it, IMO, relates to something completely different)

Don't tell me you were down town again with a stop watch and a dollar bill on a string, timing the response of the homeless people to your money.

Sorry for the tasteless joke.

 

haemphyst wrote: Steven I was assuming EQUIVALENT ALIGNMENTS. All drivers in a sealed, and say Qtc of .707 enclosure. The enclosure size and alignment DOES ABSOLUTELY affect the output, but my statement should have put all of the drivers on a level playing field, even if it does not say it.

I think you missed my point.  But it could have been because I didn't explain it well enough.  I was merely saying that they were designed around Hoffmans Iron Law, just like ours was.  They chose efficiency at the cost of enclosure size.  We chose enclosure size at the cost of efficiency.  The excursion of the subs has nothing to do with it as it isn't a physical parameter of the driver.  You can design a high excursion sub that is very efficient.  However it will require a large enclosure, or be a large midbass driver.

haemphyst wrote: No. Inefficiency is NOT a symptom of excursion, but it is completely a by-product of excursion. The trade-offs are manifest!

Again, I don't think so.  It all depends on the engineering of the driver.  If you want high excursion with high efficiency, it can be done without a problem.  The reason you don't see it is because there is no market for them. 

haemphyst wrote: Another thing I just thought of: Longer excursion almost necessarily maens more stress on a diaphragm, this mandates heavier, stiffer cones to minimize distortions... (exotic materials not completely included, but not completely excluded either - this IS a GROSS generalization) I was looking at an Eminence guitar woofer, and it has an Sd of 95 inches square, a Vd of a MERE 125cc, a MMS of 33g, but an efficiency of 96dB! (this is a guestimate, as the efficiency guide for these drivers actually specifies X efficiency at Y frequency - the sign of a GOOD loudspeaker manufacturer. These actually spec as high as 101.8dB at 3K! (Alpha-12)) Check here for the way Eminence specs their drivers.

Keep in mind that the guitar speaker you mention had to have a response up pretty high, probably covering most of the midrange territory.  This means it couldn't have a heavy cone.  However it probably didn't have much of a response below 40 Hz.  It had to give up low end extention for high end extention and efficiency.  But then you are talking about two completely different markets with two completely different requirements from their speakers. 

haemphyst wrote: Poormanq45 Yes the CV and JBL drivers DO have a larger Sd, but not enough to equal the kind of efficiency gains one sees between them and an Eclipse or Adire. My SW9122, for example, spec'd on the Klippel Machine at the Harman Labs, acheived an ABYSMAL 84dB! The old-school (1st gen) 10 inch Ti?, 78dB!!!

Out of curiousity, are you allowed to share the reports for those drivers?  I would love to see how they fare.  If you don't want to share it publically, you can send it to skephart@adireaudio.com.

Steven Kephart

Adire Audio

Let me see if I can dig them up... I am certain I have the 10 inch printouts, but the 12?   mmmmmm I think those were thrown away accidentally by the spousal unit. I'll search for the 10, if I DO locate them, I'll scan 'em, and get them to you...It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

Poormanq45 wrote: Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it

Naw, it's cool... gives me (and others, too, I'm sure) a chance to "flex my (our) mental muscle" so to speak... Bring 'em on! Discussions like this require me to do further research and thought into what I already understand about the subject... I quite enjoy it.

Poormanq45 wrote: Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

Me? I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume...It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

ham wrote: Me? I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume...

I don't know. Considering that current technology is less efficient then older technology THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range! People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

Poormanq45 wrote: haemphyst wrote: Me? I'd be curious to know if such a beast could even exist with today's technology. You'll notice I specifically DID NOT say ever. I know it could be done with a horn enclosure, but a horn is going to be FAR beyond 4 to 10 cubic feet of occupied volume... I don't know. Considering that current technology is less efficient then older technology THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range!

You're preaching to the choir, man... I have been disgusted with the ever PLUMMETING efficiency number for as long as I can remember. My engineer buddy at Harman (just so you don't all think I am blowing smoke about my "engineer friend", Steven met him at the CES this year, and he and Dan Wiggins spoke with him at great length, so Steven knows I am not BS'ing...) has been also researching this same issue. I am not really at liberty to speak of what specifically he is working on, let's just say it's being addressed.

Poormanq45 wrote: People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

Amen, brother. YEAH!!! I expect though, that a long throw, high efficiency woofer would be a cash cow for the company that comes up with it on a mass market scale. (are you listening Steven? ) I don't expect anybody is really in a hurry to produce such an animal yet - especially the companies that produce multi-kilowatt amplifiers, what would be the purpose of defeating that market angle? More money in electronics than speakers, I expect... Especially HIGH POWER electronics... Why would a company that had a 4000 watt amplifier in their line-up want to produce a high efficiency woofer, so the consumer would only NEED a 200 watt amplifier to drive it? A bit self-defeating, wouldn't you agree?It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Poormanq45 wrote: Question: Do guys not like it when I start these technical discussions? I noticed that everytime I do someone makes a comment about it

One thing I like about this forum is that everyone is more mature, and respectful to one another.  They don't allow their ego's to get in the way, causing these things to escelate into a flaming war.  But instead, this allows for calm, detailed discussion that hopefully everyone learns from.  I'll be the first to admit that I don't know it all.

Poormanq45 wrote: Steven: Are/do you guys make a high efiiciency driver that also goes really low in the frequency range AND has a high excursion? Of course the enclosure would have to be larger, but I personally would sacrifice 4~10ft^3 of my trunk to be able to drive a sub to ~120dB with only 50~100watts.

Well like I said earlier, there is just no market for that type of sub.  And as a manufacturer, you have to offer what will sell if you want to stay in business.

Steven Kephart

Adire Audio

Poormanq45 wrote: I don't know. Considering that current technology is less efficient then older technology THat's one thing I can't understand. With such "great" improvements in technology how is it that we are digressing? I mean we have lighter cones(increased stiffness lowered mass), which should increase efficiency by itself, neo magnets has become more common(higher flux density). With just these two things sensitivity should be into the high 90dBs or low 100dBs. But somehow we digressed to the 80dB range! People say that power is cheap(wwhich it is), but why not apply that cheap power to an extremely efficient driver? I mean instead of starting at 86dB at 1w wouldn't you like to start at 98dB at 1 watts?

Well, you have to understand why efficiency is digressing.  It isn't because newer technology is worse or anything.  It is simply because the market demands speakers that use smaller enclosures, but doesn't give up output or low end extension.  Because of Hoffman's Iron Law (something that NO technology will ever be able to beat) efficiency MUST suffer.  And considering that power is cheap, that isn't a bad thing. 

Steven Kephart

Adire Audio

steven wrote: Well like I said earlier, there is just no market for that type of sub. And as a manufacturer, you have to offer what will sell if you want to stay in business.

I think a little market called the Home theater market would be very interested in a sub like that.

steven wrote: Well, you have to understand why efficiency is digressing. It isn't because newer technology is worse or anything. It is simply because the market demands speakers that use smaller enclosures, but doesn't give up output or low end extension. Because of Hoffman's Iron Law (something that NO technology will ever be able to beat) efficiency MUST suffer. And considering that power is cheap, that isn't a bad thing.

Yep, I completely understand that. Unfortunately women have become the dominant party in a relationship and dictate such things as how large the speakers can be.