Agree and especially if a closed box is targeted, that is: when Qts is >=~0.29 --- <= ~0.41 ==> then Qtc is held between =0.5 to 0.7.
Look at the sensitivity spread and suggested operating BW for this driver:
This driver seems have a wide T/S spread and should IMO always be measured before any box calculation can be relied on.
Here is a suggestion(Home sub) if the TS data can be relied on that easily can be made to run in default mode = a T-TQWT or as an OD-TL(when removing the driver access lid) and in Closed box mode (removing an access lid and closing the terminus).
b
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T/S for PDW21250
Hi bjorno, and Hi Y'all,
I found some old notes on different T/S parameters for this driver which seem to make it appear quite different:
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Quotes:
"http://www.diyaudio.com/forums/showthread.php?threadid=125773&perpage=25&pagenumber=2
diyAudio Forums > Top >Loudspeakers >Loudspeakers >New Reference - SG-OB "Stargate
panomaniac, Post #37, 07-07-2008, Pyle (PDW21250) 21" T/S parameters as measured by Magnetar:
Using 250 grams "mass loading" method and LIMP this is pretty much where they all average-
FS - 31.61
RE - 5.59
RES- 59.81
QMS- 4.03
QES- 0.38
QTS- 0.34
L1- 1.88
VAS - 274.29 liters
SPL - 95.4
Magnetar, Post #48, 07-12-2008, answers to:I am curious as to your experience with the Pyle PDW21250 21"...:
I would not use them above 200 hz, they have a rising response to about 1K and a peak around 1.7K that is bad but well down is crossed over below 200 cycles with a 4th order electronic crossover. In this system they filled in below the 12. I don't know the xmax but can say when high passed at 50 cycles (3rd order) with a 275 WPC power they did not strain one bit. Now they are used down to 30 cycles with no sub and are OK. I never like to run my bass without a high pass filter, for sure if it's an open baffle.
Magnetar, Post #53, 07-14-2008:
Originally posted by BHTX: I was wondering this as well. Seems like the Madisons would have worked better for OB, but I know you don't have those anymore.
Answer: They are nearly the same thing cosmetically - I don't doubt they are made in the same factory. I never measured the Madisons but I suspect they would have fallen into the same group as these."
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The large open baffle is another possibility that could be build from these big sonotubes (I'd go with a sealed box though).
Regards,
Hi bjorno, and Hi Y'all,
I found some old notes on different T/S parameters for this driver which seem to make it appear quite different:
-----------------------
Quotes:
"http://www.diyaudio.com/forums/showthread.php?threadid=125773&perpage=25&pagenumber=2
diyAudio Forums > Top >Loudspeakers >Loudspeakers >New Reference - SG-OB "Stargate
panomaniac, Post #37, 07-07-2008, Pyle (PDW21250) 21" T/S parameters as measured by Magnetar:
Using 250 grams "mass loading" method and LIMP this is pretty much where they all average-
FS - 31.61
RE - 5.59
RES- 59.81
QMS- 4.03
QES- 0.38
QTS- 0.34
L1- 1.88
VAS - 274.29 liters
SPL - 95.4
Magnetar, Post #48, 07-12-2008, answers to:I am curious as to your experience with the Pyle PDW21250 21"...:
I would not use them above 200 hz, they have a rising response to about 1K and a peak around 1.7K that is bad but well down is crossed over below 200 cycles with a 4th order electronic crossover. In this system they filled in below the 12. I don't know the xmax but can say when high passed at 50 cycles (3rd order) with a 275 WPC power they did not strain one bit. Now they are used down to 30 cycles with no sub and are OK. I never like to run my bass without a high pass filter, for sure if it's an open baffle.
Magnetar, Post #53, 07-14-2008:
Originally posted by BHTX: I was wondering this as well. Seems like the Madisons would have worked better for OB, but I know you don't have those anymore.
Answer: They are nearly the same thing cosmetically - I don't doubt they are made in the same factory. I never measured the Madisons but I suspect they would have fallen into the same group as these."
----------------------------------
The large open baffle is another possibility that could be build from these big sonotubes (I'd go with a sealed box though).
Regards,
The argument from flat curves is a case of engineers' eyeballs looking at visual graphs, as I've said earlier in different words.
Whether of not some output curve (auditory flat or acoustically flat in music rooms etc) is superior to visual flat or simply nobody today can get as much super low bass as an earthquake or organ music fan demands, there may be other more important considerations. For example, just like many of us want subsomething filters (I don't know what to call a filter at 5 Hz??), we might like having a box that (a) adds linear air compression to linearize the spider (is that believed to be true?) and (b) something to hold back the cone from excess looseness at frequencies below which it isn't really radiating much.
Whether of not some output curve (auditory flat or acoustically flat in music rooms etc) is superior to visual flat or simply nobody today can get as much super low bass as an earthquake or organ music fan demands, there may be other more important considerations. For example, just like many of us want subsomething filters (I don't know what to call a filter at 5 Hz??), we might like having a box that (a) adds linear air compression to linearize the spider (is that believed to be true?) and (b) something to hold back the cone from excess looseness at frequencies below which it isn't really radiating much.
Hi,
No it doesn't, you need to start off with a lower Qts than for sealed.
rgds, sreten.
Yes i know , usually anything with a qts higher than .40 it's better to go sealed....
Hi Oliver,All
Thank you for Magnetar’s T/S of the Pyle PDW21250 driver.
The data seems to be consistent, but in fact very different ( a stronger Motor- Voice-coil assembly) when compared to the recent T/S data : See the picture:
b
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You are talking about what looks prettier on a simulation print-out, are you not? That's an abstract, engineering criterion, not a listener-centered criterion.
In practice (considering human hearing and real rooms), I say few of us can achieve satisfaction in the below-35 Hz region, analogous to the old quip that "you can't be too thin or too rich."
So it makes more sense to aim for bass-full sound instead of simulation-pretty.
I don't understand the earlier conclusions reached in this post.
Focusing on this last.
I find that spoken voice both male and female is a good test for upper bass balance with the remainder of the frequency band.
A speaker that has a Q>0.7 has some upper bass boost that makes spoken voice sound quite un-natural. When this same flawed speaker is used with music I find that the bass emphasis shows as constant thrum when ever a note near that high Q frequency comes on and it gets exaggerated. I do not like that. I have moved speakers around, away from walls, up off the floor etc, to try to remove that artificial bass effect.
I have slowly come to the conclusion that for my ears, I need Qbox <=0.8 and I have recently discovered that Qbox~0.5 sounds very acceptable with most sound sources.
How does that equate to "simulation-pretty"?
Yes, exactly.
It would seem to suggest that simulation can lead to faulty solutions and/or that the premises held as to what are "pretty" or otherwise desirable outputs are faulty.
I am sorry if my writing isn't good this morning. What I meant to convey was:
1. software is a "black box" and it may not being working right
2. software is a "black box" and may be trying to tell you how to cook the perfect hamburger, thinking (a) you value ultimate security from salmonella when in fact you value being rare or (b) it's well-meant advice doesn't apply to your BBQ device or anybody's BBQ device.
Whatever the case, it is clear that your Qts notions are not the same as the simulation and that, in your view, Qts has to change with the source.
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I have been around the education/industry scene since computers started to become a tool rather than a research topic.
I have been told more than a few times:
Never rely on the results from a computer until you are able to check by hand calculation that the the reported answer/s about that model are actually correct.
If you cannot do the long winded calculation, or if you have asked the wrong question, or you have entered the wrong model data, then you MUST NEVER accept computer predictions as gospel.
I have been told more than a few times:
Never rely on the results from a computer until you are able to check by hand calculation that the the reported answer/s about that model are actually correct.
If you cannot do the long winded calculation, or if you have asked the wrong question, or you have entered the wrong model data, then you MUST NEVER accept computer predictions as gospel.
Do you have any idea what your room gain is?? Use a smaller box and when you do your simulations take into account your room gain. In most cases you end up what looks like a rolled off curve but it actually works quite well in a typical room. Think sealed box as an example of what room gain can do.
Rob
Rob
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