driver sensitivity vs system sensitivity

[bvan]

I've got a pair of Hawthorne Audio Sterling coaxials on order, rated at 98db/w and good down to probably 40hz.

What I'm wondering is, if I add powered subwoofers to the coaxial drivers and thereby extend FR to 20hz, what effect would this have on total system sensitivity? Would it touch 100db?

I'm looking at a 2W 45 based SET to drive them is why I'm wondering.

Cheers

B.

[planet10]

Originally posted by bvan
What I'm wondering is, if I add powered subwoofers to the coaxial drivers and thereby extend FR to 20hz, what effect would this have on total system sensitivity? Would it touch 100db?

No.

I'm looking at a 2W 45 based SET to drive them is why I'm wondering.

I wouldn't be worried about the efficiency.

I would be somewhat careful with matching a small set to something with a crossover. What does the Stirling impedance curve look like?

What is the output impedance of the SET?

dave

[tinitus]

Hawthornes own sub driver augie is only 88.7db ... I suppose that personally I would use 2 of them pr side
But I think that Fs=27hz is a bit on the high side with that low SPL, but with its high Qts its probably very linear all the way and may even be crossed a bit higher than normal fore a sub
But I doubt that the coax driver will reach 40hz in OB, or at least it may be down quite a few db
Would be nice to see some measurements

This article is nice with some measurements and explains quite good what is to be expected from the augie subs

http://www.enjoythemusic.com/magazin...er_project.htm

If you want punch and slam I dont see any reason not to use a closed sub with active low xo

[tinitus]

BTW ... its possible to use an amp/filter with exstra 6db gain

[bvan]

thanks for the replies.

Cant answer you Dave, but it's a good question and has given me something to think about.

Tinitus, I have active dipole subs using Peerless drivers so wont be looking at the Augies. I'm still curious how much adding the subs will increase each speakers measured sensitivity as I will be mounting the Peerless drivers on the same baffle as the Hawthorne coaxial. It could well be that the Coaxials only get down to 60hz, but then adding a sub drivers will add more than the one octave I had guessed at earlier, and so would raise the system sensitivity by even more over the published 98db.

cheers

b.

[AndrewT]

Planet has already told you, No, it won't increase the sensitivity.

[Scottmoose]

Adding a bass driver to boost the LF SPLs will not increase the overall system sensitivity above this point. All adding the extra woofer would do, if it's crossed over right, is increase the useful bass extension of the system before it rolls off by improving sensitivity in these bass regions, where the SI has rolled off. It won't boost the sensitivity of the system as a whole.

[bvan]

Sorry Anderew, I assumed by Dave's response it might add something less than the 2db I was hoping for.

Sorry to tax your patience, but I still dont see how adding a whole octave or two courtesy of an addition 12 inches of driver with 340W behind it, which wasnt present when the measurement was taken, wouldnt increase the speakers sensitivity rating by any appreciable amount. I'm guessing the measurement is taken with some kind of full frequency noise and not a 1khz tone but perhaps I'm wrong about this, or is my reasoning a bit off?

Patient replies appreciated, Cheers

b.


fwiw, reading around now I found a Stereophile article explaining how measurements are taken

"The bandwidth of a loudspeaker will also affect the measured sensitivity if wide-band noise is used as a test signal. Two speakers may sound equally loud on music, but on noise, the model with better extension at the frequency extremes will measure as having a higher sensitivity. What is needed, therefore, is a means of producing a measured sensitivity that correlates with perceived loudness." "Critical-band analyzers not being easy to come by, at Stereophile, I feed the loudspeaker with 20kHz-bandwidth noise at a standard level"

[Cal Weldon]

Do the Sterling's publish the frequency at which the sensitivity ratings are measured? Some are very deceptive.

[bvan]

Not yet Cal, not as far as I'm aware of.

These drivers are being made up by Eminence and I dont think even Mr Hawthorn has seen more than the prototype. What little info there is on them on the Hawthorne website has just been received from Eminence in the last week or so. Hopefully more numbers will follow.

cheers

B.