Speaker Impedance with QA403 + QA461

Hallo got an Information that at the Moment no QA461 and no QA472 in Stock on Saelig so i guess i need to wait a Month to get it and test the Impedance Measurment. :frowning:

May be i can get the QA403 earlier but thats cost me extra Money to Germany. Splitting the Order.

Cant wait to get that Stuff :slight_smile:

@ Matt

I guess there is an Mistake on youre Datasheets!
Look at tne Box Size i didn’t think they only 21mm high i guess it must be around 41mm or not ??? I need the Size for Planing my 19" Enclousure Front Plate! for all Devices.
on QA403 the same.

Want to use this Enclousure for max. 4 QA Devices at once with Power USB Hub and Powersupply. (ca. 100€ @ Reichelt.de GEH SG 1-19)


It’s fine to wait and that setup makes it really easy.

But if you want to start, you can do an impedance measurement with the QA403 but will need to drive the speaker will an external amplifier. I was doing this yesterday (well sort of, driving an inductor not a speaker).

You will also need to prepare your own current sense resistor and fixture for connections to the QA403. You use one channel to measure across the speaker and another channel to measure across the sense resistor. (There is a PCB for this described in the forum with Gerber on GitHub if you prefer that route).

You then need a way of getting the data out of the application to do processing yourself, like the REST API.

I can share my scripts with you to get you started if you want to go down this route.

tl;dr the QA403 and QA461 is a great value for money! You can do what you want without it; QA403 + amp + test fixture + your own data analysis, but that a hassle.

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Plan away!


Thx Dan i have the ARTA Box so i can Use it this way.

And also have an 40Watt Amp Monacor AKB-60 and MPA-102 Mic Pre i can Use.

The Power Amp i plan also to put in my 19" Enclousure with the QA461 So i have an Alternative Posability to Drive Speaker. When needed.

So no Problem at all


This is the Easiest way to do it without Printing or Engraving the Plate :wink:

84TE 3HE Plate
Or So it will work also not sure.

With such an USB Hub, 4x 1A Current at once possible.

:heart_eyes: :kissing_heart:


Hallo Dudes, i ordered this day also the QuantAsylum QA451B for an full Analyzer Settup with all have in one Enclousure with an Intel Nuc PC too.
Also did years ago an Power Load with this Resistors (ATB RB50 8.2 Ohm 50Watts) and descend Cooling may be i could it also integrade into this 19" Enclousures, not sure yet.

May be i will also intagrade an Arduino Nano for automated Controll of this Fans with NTC Measure or so.

Has anyone an idea what kind of Relais would be best to have the Possebility to Change the Resistor Values with The Arduino also for differrent Resistor Values instead of using all the 4mm Plugs ? Dont have the place on the Front for all the Plugs :wink: Or i need to put them on the Back Side.

Printrelays with 10 or 16 Amp would may be do it (Newer switch it while Measuring thou)
But i guess an good Ron would be also nice

May be i am wrong here with this :wink:

Some more Vizual Work on the Enclousure may be anyone else would build it also :wink:

Still some free Space for Connectors on the Frontpannel and Room for Little Computer and USB Hub, Powersuppy and so on.

I ordered now that HUB capabel to drive 4Ports with 1,5A Simultaneously

Got an Mail the 451B also not in Stock :frowning:

So i get only the QA403 soon and need to wait i guess a Month to get the other 3 Devices!

Matt , hurry up get some decsend coworker, i throw my Money on you :wink:



Hi Robert, for getting T/S parameters of woofers the QA461 is perfect as is. Behold though, that T/S parameters only define the low frequency behaviour. If you need full range impedance plots you can’t use the current sense output.
When you set up your measurement system take a fixed resistor with a very well known value and adjust the value of the sense resistor in the settings until the reading in the QA software matches your test resistor. This is necessary to correct for slight unit to unit variations of sense resistor and current amplifier.

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THX i guess i will implement some extra Sense Resistors in my Enclousure Design on an smal Extra PCB (0.2 Ohm 1 Watt, 2 Ohm 5 Watt and 20Ohm 10Watt would do it i guess.

With an Selctor switch or Arduino Nanno with Relais, let see what else i need to implement :wink:

This would probably also an nice addon:

Did my Job an made an Precise Drawing of the Enclousure.

So if anyone need this 3D Drawing i can Provide an *.dwg or *.STL
I used ProgeCad (Autocad Clone) for this.
Not sure how i can provide an File here???

Also will Provide an File for 3D Printed Sidecap Enclousure with Aluminium Heatsink 200x100x40 on the Side. Not Ready Yet :wink:


More Design work Inuc Integration :wink:

Next i need to make the CNC Details and do a bit CNC Cutting i guess :slight_smile:

Changed the Sidecaps and add some WLAN Antennas :slight_smile:
Probably good for Measuring Car Audio or for Outdoor Action :wink:


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More Eyecandy i hope you are not nerved like Hell :wink:

Sidecaps now from 4 Pieces for better Printability.

Stil some Designwork needed, I guess a bit more rounded eges would be nicier on the Sidecaps


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Looks great! I’m enjoying this thread a lot.

What is the huge heat sink for?

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Intel INUC Core I5 passive Cooled on the right Side and probably the 45Watt Poweramp (Monacor ) or and the Powersupply for all Devices on the left Side.


Don’t want to have noisy Coolingfans in this Enclousure \o/

But instead of an Heatsink i can Print an other Piece for the Midle Part of the Sidecap on the other Side, so Optional.

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Last night, while dreaming :wink: , i got an idea and need some advise from Matt or anyone who has more knowing !

What about to feed the USB Hub with an 12V/ 50 or 100 AMP Hour Akumulator instead of mains
With an integrated Supply to load the Akkumulator while not using it. With an Switch to use the Supply or Akkumulator.
May be also the Computer but it sucks lot of Power (19V 3.43A) produce lot of noise, i guess to and the QA403 is isolated.
Will that give me an advantage over Mains with Noiselevels and humm and so on???

So i could use an little switched Powersupply (MeanWell HDR-60-15 @ 18V, already tested it and it works with my INUC) for Computer and the Akkumulator for the Quant Asylum Devices from USB Hub ??? Will this help???

I have an Panasonic 12 V 7,2 AH Akkumulator i guess i need to test it. :wink: when my Devices arived.

Got my QA403 this day and did some Measurments in Compare to my earlier used Device the Terratec DMX 6 Fire (only for Speaker Measurments). Laso Comparing the Measurments with QA Software to REW measuring the Device himself.
Used Hardware:

Powersupply of USB HUB:


Terratec DMX 6Fire:

QA403 QA Software:

QA403 REW:

Terratec REW

Linearity Compare:

One Question i got:
The 6dB Gain on the QA Software, is it fixed??? Where i can set it to other Level.
Didn’t find a possibility on the Main Screen.
The Generator was set to -6dBv.
I guess need to read the Dokumention…not funny i am a Man we dont read Dokumention by default :wink:

The first USB Cable i tried had only 3.8V at QA403 Delivered :wink: from that Hub.
Then i used another one , it was abit thiker and than i got the showing Voltage and Current.
So realy get an good Usb Kabel, seems Essential for that Device.

So did the USB HUB on Battery Measuring:

So it seams it didn’t help much :wink: I guess its becaus the USB Connection to the Computer and the Isolation on QA403 already do his Job.


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Hi Frunse. The 6db gain you read in the “Gain” tile is because you are making a differential measurement of gen1. That is why you are reading a gain of +6dB (measuring the voltage of gen1 in differential mode, you are measuring twice as much voltage as measuring in single ended mode). Try making the Single Ended measurement of gen1 and you will see that 0dB will appear in the “Gain” tile.


Thank You, didn’t think about the Differential Gain add :wink:
With Terratec i only measured Single Ended :frowning: till now!

Some Information about the Costs to Germany so far:
QA403 @ Saelig 590$ (541,92 Euro)
Duties to Germany (ZOLL): 129,36€
UPS Worldwide Express®: $65.59 (60,24€)
So at all for QA403: 731,52€

For my first Non Speaker Mesurment it was an good Idea to test my Siglent SDG2042X Functiongenerator :slight_smile: and it is so easey with QA403. (1Vrms, Out 1, 1kHz Sinewave, HighZ)

Also Measured with 0dBm for Comparing the Datasheed:

@20Hz 0dBm

@20kHz 0dBm

Differential Signal fron Generator (2 Channel Out) in Tracking Mode 1 kHz:

I hope i did it right, it seems It is better than the Datasheet says?

Not the best, but good bang for the Bugs, Also Hacked to 120MHz :wink: Very Nice.


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Did some DAC Measuring (Playing around ;))
Cambridge Audio DAC Magic Plus Out Single Ended with REW Generator in to QA403 IN L:

Same with Motu UL Mk5:

And with Pioneer UO-5 Headphone Amp / DAC

Music Fidality V90-DAC, the last one :wink:

The old Dac Magic Plus still not that Bad at all.

Hallo Matt any chance to get an Expansion Board with SPDIF or Optical (or Both) Out for DSP or DAC Measuring directly with QA403???

Or an Advice what kind of DIY Board would work?

Will This work (Without that USB Modul)?

Or this (Included Bluetooth 5.1 and this is possibly useless without that USB Board!):

would be Handy! :slight_smile:

Then i need to change my Enclousure Design, so all could Fit together!:

Can’t stop Drawing ;)…Maaaaaaatttttt i need Input…Drawings please…

But now i need to get all the Other Devices or Drawings from Matt so i could made my Designing ready to go! :wink:
Rady to Rumble…if Matt could deliver the Devices ;)…



Hi Robert,

I’m really impressed with the creativity and your CAD skills. Legend has it if you want to attract Matt’s attention ~say his name three times into a mirror~ place an “@” symbol before his handle: like so @matt , good luck with the enclosure design.

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I got already e-mail Contact with him, but no reaction about the Possebillity to get Drawings from him in the Passt, so i need to wait to get the Devices before i can made my Design ready to go, but this could took some Month.

The new 462 Transducer Driver its on his way but tooks some Month to get delivered \o/.

But anyway, i work also on other Project so i have stilll something to do :wink:

Chaos, i asked Google Maps to show me the right way thrue all the Cables but he also not answered :wink:


I add an nice litte Device to my Enclousure Design!

Matt didnt has an Notchfilter anymore, so i need anything else to get.
Needs only USB Power, is small and inexpensive.
Also has an REW Calibration File!

I guess its the best buy Device in this Categorry :wink:

By Sure i will adapt the TRRS Conectors to BNC and get better Switches as well to the Panel.



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OK like i promis, i did an TS Measurment on an oder Audax HM170Z18 Midwoofer.
I used that 27,22 OHM (Measured with SDM3065X with 4 Wire probe) Senseresistor from Artabox nothing else from it.
Also RDc measured with 4 wire Probe = 6,05Ohm
I used -37,5 dBV and got 100mV rms on the Speaker like sugested on Arta Limp Datasheet.

Impedancemeasurment looks this way realy smooth:

My measuring scale was measuring 100,25g when i used an referense wight of 100g.
so i measured 4 Magnets at 18,97g and decidet to use 18,93g
But the Magnets give me some new resonances on the Impedance so i guess i use again
Playdough in the Future or other flat Magnets need to test it.

I didn’t know how to provide an File here so i made an Picture of the TS Parameter:

The QMs and VAS is far away from Datasheet 7,5 instead of 4,07 and 2,562Liter instead of 35,39Liter but it was not Burned in, so may be i need to let them play some hour with 40Hz or so.

And here the Datasheet:

SO i am realy off with my Parameter but this Speaker i have already 15 Years or so and never used them, in orig. Package :wink:

My Chaos Setup, i also need to Measure all the Wireresistances i guess.

I measured an 2.201Ohm MOX Resistor and got a Line around 2.4 Ohm on QA403
So next day i will do some Wirecompensations and do the same again :wink:

Also with REW

Now i used my old methode with Playdough (The Magic is to put the weigh close to the Voicecoil! But with Magnets i dont want to do it, because of the influence to Magnetic field of the Voicecoil) :

Less Weight also, only 7,26g

Much better!

But the VAS is still far Off :frowning:

Wire Calibration was helping a bit, here the Measured 2,201Ohm MOX Resistor:

@ 2,26 Ohm i would say :wink:
RSense with Wire is now 27,298 Ohm before 27,22 Ohm.

TS Measuring now:

and the Data:

Stil VAS is far off!

Simulation with orig Data from Datasheet:

Volume 25L looks good.

And with the Measured TS Parameter :frowning:

Volume 2,8 Liter and an Bassreflex Tube 170cm long thats absolutly crap something is wrong with the VAS Value Calculation
Also the Inductance is more than twice high instead of the orig. Datasheet.
I guess because of all the used Wire.

Need to rethink this Setup, all Wire need to be short as possible i guess.
May be the Rsense Resistor is to high need to try an 1 Ohm 5Watt next day or anything like this.

Or i do something totaly wrong.
Next day i try another speaker that i bought this Year, let see :wink:
And of course using REW and may be ARTA for Comparing.

Last for today with Rsense 2,2Ohm and short wire to Rsense, but not much difference.

Again 100mV RMS at Speaker (@-47,5dBV)

OK Guys cant believe this but the Problem is the Speaker :wink: absolutly to old, i guess i can throw them away …

Measured now my new bought ScanSpeak 18W/8434G00 with the same Setup and Weight!

And here the Datasheet:

FS=50Hz (54,7Hz QA403)
RE=5,6Ohm(5,54 SDM3065X)
Qts=0,43 (0,49 QA403)
Qes=0,46 (0,54 QA403)
Qms=7,58 (4,86 QA403)
VAS=19,5L (18,897L QA403)
Le=0,55mH (0,727mH QA403)
BI=7,2Tm (6,41Tm QA403)

So for an not Burnt in Speaker not far from Datasheet :wink:
Simulation with Datasheet Parameter:

Simulation with Measured TS Parameter:

Next day i will Burn it in and measure again , let see how it will Change :wink:
Did an 3 hour Burn In prucedur with 30Hz and around 6mm p-p Cone Movement.

FS=50Hz (54,7Hz QA403) (54,93Hz BurnIn)
RE=5,6Ohm(5,54 SDM3065X)
Qts=0,43 (0,49 QA403) (0,47 BurnIn)
Qes=0,46 (0,54 QA403) (0,53 BurnIn)
Qms=7,58 (4,86 QA403) (4,08 BurnIn)
VAS=19,5L (18,897L QA403) (20,82L BurnIn)
Le=0,55mH (0,727mH QA403) (0,746mH BurnIn)
BI=7,2Tm (6,41Tm QA403) (7,12Tm BurnIn)

So an smal change in Values but nothing much different on Simulation.
May be 3 Hour isn’t enough.
Some say its enough for an hour some say at least 24hour needet i am not sure may be an Expert could say something abaut that Burn In Time.

Stil Simulation say 7 Liter more (35,6L for 42Hz -3dB) than the Datasheet says (29L for 42Hz -3dB)

Anyway i bought 4 of them for an MTM Configuration in a closed Box, and use of 2 Ripole Subwoofer’s with 2 12" Chassis in each Subwoofer

So i will use 15Liter for one Cassis in a closed Box. :wink:

Same procedure this day with REW using this Connection and an 100Ohm (99,82Ohm) Rsense without an Amp:
impedancesetup REW

One Qote here to say: on that QA403 both Inputs Single Endet at + Connection has an Phasshift of 180 degre!! so this measuring was’nt working until i go to left IN “+” and Right In “-”
Measured Resistor 2,20 Ohm MOX after Calibration:

Speaker Measuring:

Calculatet Data:

and here the Simulation:

Not much change in Volume for Bassreflex but 38Hz @ -3dB instead of 42Hz
FS=(54,7Hz QA403) (54,7Hz REW)
RE=(5,54 SDM3065X)
Qts=(0,49 QA403) (0,5 REW)
Qes=(0,54 QA403) (0.554 REW)
Qms=(4,86 QA403) (5.169 REW)
VAS=(18,897L QA403) (16.66L REW)
Le=(0,727mH QA403) (0.346mH REW)
BI=(6,41Tm QA403) (6.862Tm REW)

Is there an Calibration option for the Impedance Measuring on QA403???
The Resistor 2,20Ohm was a bit off (2,26Ohm) there without Cal. \o/
REW was 100% Spot on with QA403 :wink: