Doing some measurements comparing a .32 Qts woofer ( Dayton PA310) VS a 2.0 Qts woofer (Goldwood GW-215/8) and I see what I would expect to see at the low end. The .32 Q unit starts rolling off below about 150hz and the 2 Qts woofer has a rising response below about 150hz ( see attached)
My question is about the the specs for the Eminence Alpha 15A . They claim a Qts of 1.26, HOWEVER the published freq response curve shows a roll off below 150 hz thats looks like the roll off in the .32 Qts woofer I measured above.
https://www.parts-express.com/pedocs/specs/290-407--eminence-alpha-15a-spec-sheet.pdf
How can a Qts of 1.26 give a freq response like the one Eminance publishes? I wouldnt expect it to have quite the rise is the 2.0 Qts Goldwood BUT I wouldnt expect it to roll off the low end the way the .32 Qts Dayton does.
What gives here? And is it even possible for a 94db sensitivity cone ( Alpha 15A) to have a Qts as high as they have published?
My question is about the the specs for the Eminence Alpha 15A . They claim a Qts of 1.26, HOWEVER the published freq response curve shows a roll off below 150 hz thats looks like the roll off in the .32 Qts woofer I measured above.
https://www.parts-express.com/pedocs/specs/290-407--eminence-alpha-15a-spec-sheet.pdf
How can a Qts of 1.26 give a freq response like the one Eminance publishes? I wouldnt expect it to have quite the rise is the 2.0 Qts Goldwood BUT I wouldnt expect it to roll off the low end the way the .32 Qts Dayton does.
What gives here? And is it even possible for a 94db sensitivity cone ( Alpha 15A) to have a Qts as high as they have published?
Attachments
Bummer and just now noticed the link that has all the info/math is a dead one, though thankfully is in the Archives: https://www.xlrtechs.com/dbkeele.com/PDF/Keele (1977-05 AES Preprint) - LF Horn Design Using TS Paras.pdf
Bottom line, if seriously interested in designing speakers, horns beyond doodling with design programs till you get what seems suits the needs of your app, then you must understand these fundamentals of acoustics.
Bottom line, if seriously interested in designing speakers, horns beyond doodling with design programs till you get what seems suits the needs of your app, then you must understand these fundamentals of acoustics.
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Dead link! Sorry, in my haste I forgot to copy the header 
http://web.archive.org/web/20240415222624/https://www.xlrtechs.com/dbkeele.com/PDF/Keele (1977-05 AES Preprint) - LF Horn Design Using TS Paras.pdf
http://web.archive.org/web/20240415222624/https://www.xlrtechs.com/dbkeele.com/PDF/Keele (1977-05 AES Preprint) - LF Horn Design Using TS Paras.pdf
Eminence is measuring frequency response for their woofers while mounted in a very big enclosure volume (1000 liters AFAIK). When mounted in enclosure with appropriate volume it will exhibit expected rise because of high Qts.
Yes, it is possible.
It can if you did some manipulation. It does not matter how extremely large a test enclosure was, Qtc would be close to Qts.
It is quite possible with a magnet like that. I have checked the Impedance peak at Fs, published Q factors are real.
if the woofer is mounted in a "very big" enclosure, I did see that btw itis huge! THEN shouldnt the FR be similar to just a huge baffle? In other words with a Qts at 1.26 we should see some rise in spl level below 150 hz. Just seems to me something is missing here
This Eminence driver is supposedly used by a lot of open baffle guys I assume for its rise in level at the low end to augment the baffle cut off and the high Qts would fit here BUT the roll off published looks much more like a low Q woofer
ok
so why then does Eminence show a freq response that looks very much like a low Qts woofer
seems to me something is wrong with the published data?
so why then does Eminence show a freq response that looks very much like a low Qts woofer
seems to me something is wrong with the published data?
A bit more specific:
T/S Explained
T/S Equations and how each one affects the others
Using eff/n0 to compare drivers note the formula n0 = (9.7822 * 10-10 * Vas * Fs3) / Qes with Fs dominant and Vas too if a large differential such as the 15A has, so 'run the numbers' for the various drivers to see how close they match ratio wise
thanks GM
btw all in listening tests between the high Q Goldwood 15 inch and the low Q 12 inch Dayton in an open baffle both crossed and taylored to a close FR through the crossover region at 18db 300 hz, the higher Q woofers FR certainly goes deeper and looks "better" on paper
HOWEVER there is absolutely no comparison in sound quality. The low Q Dayton stomps the high Q Goldwood in every way except the added 20 hz in the low end that the Goldwood does AND while I can hear this difference it in no way makes up for the high Q woofers ponderous slow polite and undynamic personality compared to the low Q woofer.
I suppose its not a great compare as there are other things to consider and sure enough in other measurements the cheap Goldwood seems to have a trully crappy cone behavior,
However the low Q Daytons have been completely beaten up by unorthodox experiments gluing foil skinned wedges on there cones and ripping them off making rips and creases in the cones that have been crudely patch up with paper strips and contact cement. You would never think that they would be any good after the patch jobs BUT they still exhibit the same basic measurements in FR and waterfall plots and again they absolutely stomp the Goldwoods and sound the same as when they were new.
A very limited sample here BUT the results are consistent with reports I hear from others about the sound of low Q woofers VS high Q woofers in similar setups. Ya loose some low end ( the low Q woofer reaches to about 50 hz but the high Q reaches to about 30 hz) BUT so far I find that is a small price to pay for solid dynamics of the low Q woofer. The system with the high Q woofer installed is pleasant sounding ho hum. With the low Q woofer my head starts bobbing to an exciting dynamic quality that simply isnt there in the other unit.
btw all in listening tests between the high Q Goldwood 15 inch and the low Q 12 inch Dayton in an open baffle both crossed and taylored to a close FR through the crossover region at 18db 300 hz, the higher Q woofers FR certainly goes deeper and looks "better" on paper
HOWEVER there is absolutely no comparison in sound quality. The low Q Dayton stomps the high Q Goldwood in every way except the added 20 hz in the low end that the Goldwood does AND while I can hear this difference it in no way makes up for the high Q woofers ponderous slow polite and undynamic personality compared to the low Q woofer.
I suppose its not a great compare as there are other things to consider and sure enough in other measurements the cheap Goldwood seems to have a trully crappy cone behavior,
However the low Q Daytons have been completely beaten up by unorthodox experiments gluing foil skinned wedges on there cones and ripping them off making rips and creases in the cones that have been crudely patch up with paper strips and contact cement. You would never think that they would be any good after the patch jobs BUT they still exhibit the same basic measurements in FR and waterfall plots and again they absolutely stomp the Goldwoods and sound the same as when they were new.
A very limited sample here BUT the results are consistent with reports I hear from others about the sound of low Q woofers VS high Q woofers in similar setups. Ya loose some low end ( the low Q woofer reaches to about 50 hz but the high Q reaches to about 30 hz) BUT so far I find that is a small price to pay for solid dynamics of the low Q woofer. The system with the high Q woofer installed is pleasant sounding ho hum. With the low Q woofer my head starts bobbing to an exciting dynamic quality that simply isnt there in the other unit.
So bottom line for those of us (me) that demand perfectly tracking music's transient response requires a 0.577 system Qt IIRC, so sealed or backed into it via adding series resistance to low Qt drivers and/or 'critically' damping it with < ~0.577 Qt drivers once any series R is included.
yea I wonder about the series resistance Ive added to the .3 Qt woofer in the crossovers inductors
they measure about 1 ohm total
whats the formula for Qt change with added R?
never mind I see 2X Re doubles Qes work back from ther lloks like I need to about double Re to go from .3 to .57 Qt I assume about what 2-3 db loss in sensitivity
hmmm very tunable
lets see how big a hole I can melt in the floor 😉
they measure about 1 ohm total
whats the formula for Qt change with added R?
never mind I see 2X Re doubles Qes work back from ther lloks like I need to about double Re to go from .3 to .57 Qt I assume about what 2-3 db loss in sensitivity
hmmm very tunable
lets see how big a hole I can melt in the floor 😉
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High Qts speakers just have the same old typical suspension and cone design.
Rather heavy or light cones or stiff or loose suspension for the application.
Qts just goes to junk or very high because the magnet is weak and cheap.
No control. Needs a bigger box.
Low Qts speakers have rather powerful magnets.
Fast lots of control. Easy to move, box can be smaller
The " roll off" in simulation is misleading. In a normal enclosure
They have a nice snap and good transient in real life. Will actually take EQ when applied and be accurate.
Not a smear of bass.
Open baffle means no bass and no control regardless. The trick would be underhung coils for more control.
Nobody really makes those with high excursion. Guitar speakers and Old radio speakers are underhung but Fs is high.
Same thing they have High Qts because the suspension is very stiff and usually a weak magnet to control it.
But has better control since the coil stays in the gap. As opposed to overhung where it leaves the gap and relies
on a box for control.
If a magnet is weak it has a hard time moving things in the first place. So it needs a bigger box for less restriction.
Or no box works, just the baffle needs to be large, since the out of phase signal cancels everything.
No box has no control, so like guitar speakers or old radio speakers they stay in the gap for slightly better control.
And often stiff suspension, M roll type paper of cloth. Hence why they need more magnet and often dont, hence = High Qts
Ideal open baffle would be underhung, with M roll suspension. Cone would be heavy for good bass
so to get a Average Qts the magnet would need some ooophhh.
Closet thing would be a few " Bass guitar" live sound drivers. But they are still not underhung. But Mroll suspension.
You need a massive massive magnet to get stiff suspension in low Qts. Most wont do better than .4 or .5 Qts
Something affordable in .3 zone would be huge huge ferrite magnet to keep cost down.
To get a neo that works and actually has motor force. it is a rather expensive neo magnet
Rather heavy or light cones or stiff or loose suspension for the application.
Qts just goes to junk or very high because the magnet is weak and cheap.
No control. Needs a bigger box.
Low Qts speakers have rather powerful magnets.
Fast lots of control. Easy to move, box can be smaller
The " roll off" in simulation is misleading. In a normal enclosure
They have a nice snap and good transient in real life. Will actually take EQ when applied and be accurate.
Not a smear of bass.
Open baffle means no bass and no control regardless. The trick would be underhung coils for more control.
Nobody really makes those with high excursion. Guitar speakers and Old radio speakers are underhung but Fs is high.
Same thing they have High Qts because the suspension is very stiff and usually a weak magnet to control it.
But has better control since the coil stays in the gap. As opposed to overhung where it leaves the gap and relies
on a box for control.
If a magnet is weak it has a hard time moving things in the first place. So it needs a bigger box for less restriction.
Or no box works, just the baffle needs to be large, since the out of phase signal cancels everything.
No box has no control, so like guitar speakers or old radio speakers they stay in the gap for slightly better control.
And often stiff suspension, M roll type paper of cloth. Hence why they need more magnet and often dont, hence = High Qts
Ideal open baffle would be underhung, with M roll suspension. Cone would be heavy for good bass
so to get a Average Qts the magnet would need some ooophhh.
Closet thing would be a few " Bass guitar" live sound drivers. But they are still not underhung. But Mroll suspension.
You need a massive massive magnet to get stiff suspension in low Qts. Most wont do better than .4 or .5 Qts
Something affordable in .3 zone would be huge huge ferrite magnet to keep cost down.
To get a neo that works and actually has motor force. it is a rather expensive neo magnet
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Most the Eminence " Alpha" series is cheapo depot. Stamp basket and small magnets.
To "make up" for that the cones seem light and very stiff so the SPL is higher for a small magnet.
They are live sound speakers.
Light cone = lots of distortion and stiff suspension with small magnet = High Qts
For the same price bracket usually Lavoce and Dayton will beat them.
They will actually pack a better cone and bigger magnet and often better coil design for same price.
Actually GRS will offer more for even less price.
Eminence got their cost down, but the sale price is not competitive.
Other brands offer more quality and often same price or lower for a better unit.
Way too much markup. PRV will offer same cheapos but actually sell them cheap.
Actually some PRV are not too bad and even better or same as eminence" budget" lines
Eminence uses gracious amounts of smoothing in the data sheets to hide high cone breakup.
PRV will show the cone breakup, so dont let it be misleading.
To "make up" for that the cones seem light and very stiff so the SPL is higher for a small magnet.
They are live sound speakers.
Light cone = lots of distortion and stiff suspension with small magnet = High Qts
For the same price bracket usually Lavoce and Dayton will beat them.
They will actually pack a better cone and bigger magnet and often better coil design for same price.
Actually GRS will offer more for even less price.
Eminence got their cost down, but the sale price is not competitive.
Other brands offer more quality and often same price or lower for a better unit.
Way too much markup. PRV will offer same cheapos but actually sell them cheap.
Actually some PRV are not too bad and even better or same as eminence" budget" lines
Eminence uses gracious amounts of smoothing in the data sheets to hide high cone breakup.
PRV will show the cone breakup, so dont let it be misleading.