getting to test many speakers for FR

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I am going to be testing a bunch of different speakers with the following equipment
virtins spectrum analyzer 3.1
Dell notebook computer
Soundblaster audigy nx
Tek DMM252
precision potientometer 10k
17 watt mono amp
audio resource eq100 electrotet microphone
high density pink noise
high density white noise


So now what other things would help in getting good results with out a lot of expense :idea:

I will be saving the result from my testing and testing conditions
to be shared onced I get started.
:D
plus I will later show my tmtm design and results later
 
What are the goals of your testing? Are you measuring the drivers for crossover design work?

You mention using pink noise and a spectrum analyzer, but this will give you the frequency response of the driver combined with the room response. Normally you would want to measure using a signal like MLS, a gated sine, chirp etc so that you can gate out reflections from the room. Software such as Arta, SoundEasy, Praxis etc will let you do this.

Also if you are tryng to measure the driver including impedance for crossover design, you shouldn't be using a zoble during the measurement. If you amp can't drive the driver without one, I would find another amp.

Regards,

Dennis
 
Hi,

To backup your FR measurements: IMO, I recommend you to determine driver T/S parameters too:

http://www.sound.westhost.com./tsp.htm

In addition while your driver under test is placed in a box, you could measure the FR and from it determine the Q of the box i.e. Otc and do simple calculation to test if FR measurement is complying with some of the previous found T/S data.

1.Measure the driver in box FR at about ½ ” microphone distance at the box system resonance (impedance peak and no stuffing’s).

2.Compare SPL at a frequency where the driver shows to be ‘mass controlled’ i.e. where the FR flattens out:
Then the difference in dB SPL is = 20 x log (Q) or Q = 10^((+ or -) dB difference/20).

If the driver is peaking, the difference must be positive but if negative the FR is gently sloping towards lower frequencies (happens when Qtc lower than 0.707).

3.From the equation Qtc =Qts x sqrt (1+Vas/Vb) where Qts, Vas and Vb is previously calculated, check if the former FR determined Q is close enough to Qtc.


b
 
testing

My testing procdures are: testing will be done outside at night so there will be little air disturbance and little to none reflection. Plus air density will be good for get good results. I am doing this for I have many speakers that I can not find a FR graph, and of course without knowing where the best frequency response characteristic are you cant build the best speaker combination.
My main focus is the lower midrange and up. Anyone have schematics for a good 10 to 15 mono amp that has ideal testing characteristics with integrated power supply I have lm317 and lm327 voltage regulators:scratch:
 
If you want the measurements to be useful to anyone other than you, you might want to measure with Speaker Workshop or ARTA instead of all that other gear. With Speaker Workshop you can get usable frequency (and phase) response and Thiele Small by recording the impedance.

Presumably you will mount the speakers on some sort of baffle, you should record the size and the speakers' position on it, also record the temperature of measurement and any other conditions.

I don't know what that software system you have can measure, they are rather cryptic about it. Maybe you can do a sample measurement and we can lead you in the right direction.
 
I have made some contributions to:
http://en.wikipedia.org/wiki/Thiele/Small
...most notably the equations you seek.

I believe Ro is Zmax/Re, not very useful.
Z'reduced ? ;)

F3 is not measurable unless you build a box suitable for each driver.
Xmax is not measurable with simple equipment. Maybe you could make a DC displacement vs voltage curve ;)

Sd is most easily measured as the diameter to the peak of the surround on each side, the diameter of the cone plus half of the surround. Some might say this is a bit large, saying you should use the diameter of the cone plus 1/3 of the surround.

Cms and Bl can be measured directly but it is easier to infer them from other measurements.

Le is a useless measurement other than giving an order of magnitude for advertising purposes. An impedance curve is far more valuable.
 
Ron E said:
Le is a useless measurement other than giving an order of magnitude for advertising purposes. An impedance curve is far more valuable.

With respect to high end drivers with underhung coils yes, but many speakers have Le that varies with excursion. This is a big distortion generating mechanism and can mess with your crossover actual vs designed response. I suspect it can introduce phase errors as well (phase shift vs excursion :eek: )

edit: it can be asymmetrical as well meaning the harmonics generated are odd.

I would propose that the dynamic properties of Le for a particular design should be understood before being dismissed.:)
 
So Iain, where do we disagree and how does your post follow from mine? He doesn't have equipment to measure varied Le vs excursion and the existence of varied Le with excursion (and frequency - see the wikipedia link above ;) ) merely further underlines my statement that an Le "spec" is essentially useless.
 
Sorry, I have a habit of reading threads backwards.:clown:
I took exception to your bold generalization without reading the context.

In the grand pareto of things to be worried about when building speakers, Le vs excursion is way down there. As you say, it's almost impossible to measure without a Klippel system and as long as you aren't running your speakers at the power limit, it won't ever be an issue.

But in the quest for the best, it should be considered. THD vs frequency vs output level captures all these 2nd order effects and suggests a maximum listening level for quality reproduction.

BTW, nice work on the T/S wikipedia entry - one of the better texts!
 
further information before getting started

I am working on getting the wiring set and learning speakerworks
will be using speakerworks
12" x 12" baffle speaker mounted in the middle and raises about 30 inches
will be starting with tweeters since I can gradually increase the cut on the baffle
will be doing 2 tests on speakers that have a Qts<.4
first test without fiberglass batting
Second test with
nest will be enclosed midranges should a midrange fit in the same cutout as a tweeter it will be tested at the same time
The results will be T/S parameters will be in excel format
You will have to ask for a file transfer by email to see what file goes with what speaker for some I have no idea who the manufacturer is or what model :smash: Why wont that capacitor fit there :smash: This will make the speaker fit :smash: Hitting this tweeter with a hammer will flatten that frequency response :smash:
 
Hello mcmahon48,

I am having trouble installing Speaker Workshop on a laptop, all fine on my big grey box PC though.

As you mentioned earlier, it hangs during setup on the laptop. Just wondered if you found a solution - or whether it just decided to instal for you after a while.

regards,
Simon
 
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