Why am I getting these numbers is WinISD for atlas high Q

Just wondering why I keep getting Qes aroun .734 and Qts around .660 for high Q, mid Q is off also, but not as much. Either way I'm also getting larger, and in some cases much larger, enclosures for sealed alignments compared with ascendants site. Example, low Q, which is closest in T/S to published specs,WinISD gives 5+ cubic feet for .7 Q box. Mid Q boxes are even bigger than spec. However, I tend to trust ascendants box specs more. Just wondering why ISD is off so much, or if atlas published specs are off?
 
WinISD is meant to let you simulate, not to calculate everything for you!

So whatever result WinISD is giving you, it is nothing other than just a possible tuning/boxsize like there are so many (infinite actually).

The boxsize given by AA is what they consider to be a good boxsize for their products for general or specific applications.

WinISD gives you the opportunity to decide what you think is best for yourself.

Btw use the WinISD Pro versions not WinISD 0.44

Mvg Johan
 
hello,
thanks for the reply, I have been using the latest version ISD pro that is available, the one that has to autocalculate some of the T/S figures in order to work with uploaded drivers, which I thought was accurate. Just wondering why they are coming out different than published specs. I have 2 atlas 15's, and for now looks like I'm going with 8 ft3 ported at 19 hz for just 1. Trying to model some smaller sealed with mid or high q to use with mild linkwitz transform or just some low end eq. I could call Chad, but I like being able to replicate manufactures designs with a program so I can trust further designs with that program. Thanks again,

Giyan
 

Ron E

Member
2002-06-27 10:41 pm
USA, MN
I don't own one of these woofers, but I understand resistively damped drivers fairly well. If I understand the published parameters correctly, these are the parameters you should use:

Fs 23.200 23.200 23.200 Hz
Qts 0.520 0.428 0.359
Qes 0.581 0.581 0.581
Vas 128.500 128.500 128.500 liters
Re 2.800 2.800 2.800 Ohms
Dia 24.750 24.750 24.750 cm
Xmax 18.000 18.000 18.000 mm
Pe_max 300.000 300.000 300.000 Watts
Le 0.001 0.001 0.001 Henrys

Qms 4.953 1.620 0.941
Sd 0.048 0.048 0.048 m^2
Mmd 0.119 0.119 0.119 kg
Cms 0.000 0.000 0.000 m/N
Bl 9.145 9.145 9.145 Tesla*m
Rms 3.504 10.714 18.440 kg/s
no 90.818 90.818 90.818 dB/2.83V
no 86.259 86.259 86.259 dB/1W

These are for High, Medium and Low Q, respectively. That meaning open coil, 1.5 ohms and shorted terminals, respectively.

Notice that Qes stays the same for all configurations and Qms varies depending on what resistance is across the damping coil. BL should stay constant as well as the sensitivity/efficiency.

It would be interesting to know how these parameters compare with what people have measured.
 
wow!

nice answer, AA must have there specs off. They say qms stays the same, while qes and qts change. I'll try to talk with chad about it if he's not to busy. This would make sense with the numbers winisd is kicking out, I'll try pluging in again and see what happens. I'll post back tonight maybe, thanks.
 
Hi,

I recalculated the T/S parameters of the Atlas subwoofers in resistively damped operation, please comment.

These calculations are based on the Qts value Chad stated on each configuration. (Assuming it was correctly measured...)

Don't worry too much, the boxes needed are now a little bit smaller but the efficiency is a little bit lower in lowQ configuration. (I didn't check the others)

Atlas 15 (HighQ) :
Qts=0,57
Znom=4 ohms
Fs=21,5858613219458 Hz
Pe=300 W
SPL=89,7175159835353 dB
Re=2,8 ohms
Le=0,86 mH
BL=9,19747776183505 N/A
Xmax=18 mm
Cms=0,391098993059234 mm/N
Qms=6,58666666666666
Qes=0,624
Rms=2,86218937825208 Ns/m
Mms=139 g
Sd=810 cm^3
Vas=364 L
Vd=1,458 L
no=0,570566510517391 %
Dd=32,1142340907499 cm

Atlas 15 (MidQ) :
Qts=0,45
Znom=4
Fs=21,5858613219458
Pe=300
SPL=89,7175159835353
Re=2,8
Le=0,86
BL=9,19747776183505
Xmax=18
Cms=0,391098993059234
Qms=1,61379310344828
Qes=0,624
Rms=11,6819729438289
Mms=139
Sd=810
Vas=364
Vd=1,458
no=0,570566510517391
Dd=32,1142340907499

Atlas 15 (LowQ) :
Qts=0,37
Znom=4
Fs=21,5858613219458
Pe=300
SPL=89,7175159835353
Re=2,8
Le=0,86
BL=9,19747776183505
Xmax=18
Cms=0,391098993059234
Qms=0,908976377952756
Qes=0,624
Rms=20,740129038205
Mms=139
Sd=810
Vas=364
Vd=1,458
no=0,570566510517391
Dd=32,1142340907499

Atlas 12 (HighQ) :
Qts=0,52
Znom=4
Fs=23,3164531707879
Pe=300
SPL=86,5104111441438
Re=2,8
Le=0,86
BL=9,16612146732648
Xmax=18
Cms=0,391532959231332
Qms=4,95278688524591
Qes=0,581
Rms=3,51997578844834
Mms=119
Sd=481
Vas=128,5
Vd=0,8658
no=0,272643904841654
Dd=24,7472871446066

Atlas 12 (MidQ) :
Qts=0,415
Znom=4
Fs=23,3164531707879
Pe=300
SPL=86,5104111441438
Re=2,8
Le=0,86
BL=9,16612146732648
Xmax=18
Cms=0,391532959231332
Qms=1,4525
Qes=0,581
Rms=12,0025403933976
Mms=119
Sd=481
Vas=128,5
Vd=0,8658
no=0,272643904841654
Dd=24,7472871446066

Atlas 12 (LowQ) :
Qts=0,33
Znom=4
Fs=23,3164531707879
Pe=300
SPL=86,5104111441438
Re=2,8
Le=0,86
BL=9,16612146732648
Xmax=18
Cms=0,391532959231332
Qms=0,763864541832669
Qes=0,581
Rms=22,8230124147182
Mms=119
Sd=481
Vas=128,5
Vd=0,8658
no=0,272643904841654
Dd=24,7472871446066
 
I may have an idea

Entering numbers into winisd as directed by the help guide gave me this.

qes=.734
qms=6.56
qts=.660
fs=21.67
vd= 1.46( this is with xmax at 18mm, 36mm gives full spec)
vas=361.12
spl=89.03
uspl=93.6

entering while trying to keep close to spec'd #s

qes=.642
qms 5.082
qts.570
fs 21.5
no.5480 was a little off
the rest was pretty close

I think that the second coil being 2 ohm, and very different from the main coil is throwing things off, and may be acting different than standard resistive damping modeling, I could be wrong, as i don't have alot of experience modeling this.

For now, I'll do a 8 ft3 19 hz. The ported boxes and low q specs match up pretty close. Later on I might try two smaller sealed with the q adjusted to my liking, if I can figure out how to model.

cheers,
Giyan