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Multi-Way Conventional loudspeakers with crossovers

How to find/determine Qts
How to find/determine Qts
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Old 21st October 2017, 04:10 PM   #1
viktor1601 is offline viktor1601
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Default How to find/determine Qts

I have bought Pioneer TS-G1731I speakers, and want to build a ported design with it. To define the dimensions of the port and the enclosure i will use this calculator:
mh-audio.nl - Vented System
However, I can't seem to find the Qts and Vab of the speaker. I have found some formulas to calculate them but in those formulas I only found more variables I can not find/calculate/determine/...
Hope someone can help me out cause I really need this info to finish my diyspeaker project.

Thanks in advance
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Old 21st October 2017, 04:29 PM   #2
CharlieLaub is offline CharlieLaub  United States
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By a Woofer Tester 2. It's very well worth the investment.
woofertester.com
Another good system for measuring driver and other parameters is the DATS system from Parts-Express:
Dayton Audio DATS V2 Computer Based Audio Component Test System
DATS is probably more capable, but I don't have any personal experience with it.

There are manual ways to measure driver parameters with some other tools like a voltmeter and scope, but the are not reliable for a novice.
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Old 21st October 2017, 05:37 PM   #3
Lojzek is online now Lojzek  Croatia
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Very easy to measure with free ARTA measuremenet software using a sound card and a 100R resistor. Get LIMP user manual.

ARTA Download
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File Type: png IMP Jig.png (25.6 KB, 184 views)
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Old 21st October 2017, 06:28 PM   #4
infinia is offline infinia  United States
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the best way is to measure it. b/c even if you found the specs, it's not the most reliable data.

Q= BW/Fs
BW= -3db points (-0.707 Vp ) on either side of the resonance peak (Fp) by name Fl and fh
(BW) bandwidth may NOT be symmetrical.

Support the driver in free air by hanging it up away from objects.

Use DMM on AC mV along with sine wave function generator use a ~500 ohm to 1K series resistor. Sweep the freq while watching for a voltage peak or a current minima.
Some mid range DMMs have accurate freq counters if you don't have good resolution.
Can use a PC computer headphone jack for a function generator. but don't blow-up your soundcard

Qts = (Fh-Fl)/Fp solved by your data
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Last edited by infinia; 21st October 2017 at 06:56 PM.
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Old 7th December 2017, 01:45 PM   #5
bjorno is offline bjorno  Sweden
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Hi All,

Sorry to be late to this tread. Forgot to Post my investigation of this Driver:

b
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File Type: jpg Pioneer_TS-G1731I.JPG (753.2 KB, 123 views)
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Old 7th December 2017, 03:56 PM   #6
GM is offline GM  United States
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Greets!

Thanks for the tutorial , though I believe you mean: *104 L sealed...no lining.

Business must be booming, any cool new [raw] speakers on the way?

GM
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Old 7th December 2017, 10:00 PM   #7
Ron E is offline Ron E  United States
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Quote:
Originally Posted by bjorno View Post
Hi All,

Sorry to be late to this tread. Forgot to Post my investigation of this Driver:

b
From the info you have provided in that image, you can't possibly know any of the T/S parameters other than Fs to even one significant figure, let alone 8.
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Old 22nd December 2017, 10:02 PM   #8
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by GM View Post
Greets!

Thanks for the tutorial , though I believe you mean: *104 L sealed...no lining.

Business must be booming, any cool new [raw] speakers on the way?

GM
Hi GM,ALL

A Tutorial it is!
Thank you for correcting me! You found despite my messy Cut and Paste Picture a flaw...I must had a Brain F..t when I wrote 104 L BR as it should be a Sealed Box. I found another a Cut and Paste error: see Picture.
The Sealed Box: Vas/Vb=0.094 low enough to qualify for a Speaker IB performance hence my choice to Label the estimated calculation of *Qtc = Qt =~Qts= O.6216 to be a Base for further calc. of underlying Parameters; fc=~ 80.5 Hz, f-3dB= ~88.2 Hz that is ~20 dB down at 30 Hz, not if a Ported one(Max 10 dB down(from ~400Hz to 30 Hz) if slightly PEQ'd and stuffed to a smooth shelving FR end.

*I have no idea what conditions and how the driver fs is measured, but Iím confident that fs=77Hz +- any insignificant Decimal is a good estimation and can be used as ~fc when taking a reading from the given FR curve that is not more than a ~% off.

I Mailed this Swedish Retailer of Pioneer TS-G1731I (449 SEK= ~53 USD):

Pioneer TS-G1731i 6,5''

asking for more info of the Driver, i.e. the Re value..for one test Specimen was measured to be ~3.7 Ohm.

All European Retailers state the Sensitivity to be = 89 dB not 90 dB that will in case with Re= 3.7 Ohm (not 3.2) make the Driver less Sensitive and less lossy (BL down ~0.2 N/A but Rms up ~1.4 kg/s; Qes=0.689 ==> 0.864 and Qms=6.32 ==>2.21).

In additional I assumed the Driver fs was measured an IEC Baffle i.e. a ~0.5% error at Max , hence fc/fs=sqrt(1+Vas/Vb) can be used when calculating a sealed IB Box.

b
Attached Images
File Type: jpg Pioneer_TS-G1731I_Re-3.7Ohm.JPG (767.9 KB, 56 views)
File Type: jpg Pioneer_TS-G1731I_104L Sealed+~37L_ML-TL.JPG (494.5 KB, 56 views)
File Type: jpg Pioneer_TS-G1731I_ML-TL_MJK.JPG (761.5 KB, 58 views)
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Old 23rd December 2017, 01:52 PM   #9
Ron E is offline Ron E  United States
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You know Fs is 77, you know this to perhaps +/- 20%
You know sensitivity within ~3dB
You make a bunch of other assumptions, then suddenly you know Q to 8 places?
The margin of error in this calculation is surely quite large, probably at least 30%, as in you might estimate Q is 0.6 +/- 0.2, so somewhere between 0.4 and 0.8 perhaps 60% of the time and between 0.2 and 1 maybe 90% of the time...

It would be instructive to do an uncertainty analysis.
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