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Author Topic: Best way to test speakers that return from a rental?  (Read 1599 times)

Brad Gibson

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Best way to test speakers that return from a rental?
« on: March 20, 2017, 01:12:46 pm »

What is your process when a speaker comes back from a rental to make sure it is still in good condition?


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Riley Casey

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Re: Best way to test speakers that return from a rental?
« Reply #1 on: March 20, 2017, 01:25:25 pm »

Tone sweep will tell you what you most need to know - is everything working and working without mechanical damage.  Where this falls down is multiple drivers in the same passband.  An example would be something like a JBL vertec with four mid drivers in series parallel.  Any one driver out means one pair is not working.  In cases like that you need a piece of plywood to cover one pair of drivers to confirm both sets are working.  Music testing, pink noise testing don't tell you what you need to know about speaker damage.  A five dollar phone app with a sine wave generator does.

What is your process when a speaker comes back from a rental to make sure it is still in good condition?

Scott Helmke

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Re: Best way to test speakers that return from a rental?
« Reply #2 on: March 20, 2017, 01:33:03 pm »

Mostly we just use music, though it's a specific CD that we're all used to. If you test several of the same speaker in a row a bad one will be obvious.

Some speakers have a more detailed test process, like the Danley Jerichos with multiple drivers in parallel. Those get tested with a speaker impedance tester to make sure none have failed, then with music. After several uses I do a rather convoluted test with Smaart to make sure all the woofers are good.  They're all driven separately but three a side share the same cavity, so I use Smaart to drive the middle one with pink and then use the other two (one at a time) as the mic inputs for the test signal. That gets compared from an earlier known-good measurement.
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Brad Gibson

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Re: Best way to test speakers that return from a rental?
« Reply #3 on: March 20, 2017, 01:42:31 pm »

Tone sweep will tell you what you most need to know - is everything working and working without mechanical damage.  Where this falls down is multiple drivers in the same passband.  An example would be something like a JBL vertec with four mid drivers in series parallel.  Any one driver out means one pair is not working.  In cases like that you need a piece of plywood to cover one pair of drivers to confirm both sets are working.  Music testing, pink noise testing don't tell you what you need to know about speaker damage.  A five dollar phone app with a sine wave generator does.

We currently use this method and it seems to work about 90% of the time.  Do you know of a full proof tester that will take the guess work out of the equations?  Im looking to take the human error factor away. 
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Josh Millward

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Re: Best way to test speakers that return from a rental?
« Reply #4 on: March 20, 2017, 02:09:25 pm »

We currently use this method and it seems to work about 90% of the time.  Do you know of a full proof tester that will take the guess work out of the equations?  Im looking to take the human error factor away.

I would highly recommend using an impedance sweep to test the loudspeaker. This will bring to light any deviations from previously measured impedance sweeps of the same cabinet.

I would highly recommend doing a baseline sweep to start with, then using that to compare them each time they come back from rental. You can save a new sweep each time, so you can see how the sweep changes over the course of the loudspeaker's lifespan.

You can set up Smaart or TEF to do these sweeps pretty easily, but a great low cost entry into this field is the Dayton Audio DATS V2 setup available from Parts Express for less than $100. You do require your own computer, but it does provide the interface and the software.

This is a very simple test you can do to insure your loudspeakers are always doing what they should.
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Tim McCulloch

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Re: Best way to test speakers that return from a rental?
« Reply #5 on: March 20, 2017, 02:11:37 pm »

We currently use this method and it seems to work about 90% of the time.  Do you know of a full proof tester that will take the guess work out of the equations?  Im looking to take the human error factor away.

Any testing needs to be 100% repeatable.  That means the testing environment must be identical, every time & every test.

I've done acoustic measurement in our warehouse, and simply moving the inventory around was enough to change the measured results even when the DUT and measurement mic remained in the same places... try this:  if you keep the same DUT and only move around the other inventory, does the measurement remain identical?  If not, you can't depend on your test environment to give repeatable results.

This could require a combination of impedance measurements and acoustic performance verification to de-humanize the testing, too.


Edit PS - +1 to Josh's suggestion of the Dayton DATS v2.
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Riley Casey

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Re: Best way to test speakers that return from a rental?
« Reply #6 on: March 20, 2017, 02:51:41 pm »

My bet was that the OP was looking for a quick and dirty test to ensure that the weekend DJ didn't blow up the subs he rented or the wanna be rock god didn't toast the wedges he rented with constant feed back.  For this sort of thing its a tone sweep with a human doing the listening. If you think you need to be more precise then by all means establish a test regime with specified voltages at the speaker input terminals for each speaker in inventory and a specified start and end frequency but short of a very expensive set of test gear that would absolutely not provide an appropriate ROI if used simply to test rental returns the right solution is a tone sweep and a set of ears.  If you think a phone app isn't impressive enough go out on Ebay and buy an HP sig gen.

Art Welter

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Re: Best way to test speakers that return from a rental?
« Reply #7 on: March 20, 2017, 04:13:23 pm »

Any testing needs to be 100% repeatable.  That means the testing environment must be identical, every time & every test.

This could require a combination of impedance measurements and acoustic performance verification to de-humanize the testing, too.


Edit PS - +1 to Josh's suggestion of the Dayton DATS v2.
Tim,

The repeatability factor is the tough nut for most to crack, as it either requires a spot well away from movable objects outdoors, or a dedicated "test room" that does not change.

Just got off the DIY forum, where "Patrick Bateman" just mentioned he's had three DATS "blow up".

REW, a freeware program does good impedance testing, as well as dual FFT, etc., but requires a simple test jig to be made.

I plan to make that jig as soon as I finish approximately 125 other items on my backlog of items on the "to do" list.

I did finish wiring my water heater 3/18/17, had my first hot shower since 12/10/17, the day my credit card was hacked for the first time..

Art "Titanium Cranium" Welter

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Stu McDoniel

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Re: Best way to test speakers that return from a rental?
« Reply #8 on: March 20, 2017, 05:02:01 pm »

Tim,

The repeatability factor is the tough nut for most to crack, as it either requires a spot well away from movable objects outdoors, or a dedicated "test room" that does not change.

Just got off the DIY forum, where "Patrick Bateman" just mentioned he's had three DATS "blow up".

REW, a freeware program does good impedance testing, as well as dual FFT, etc., but requires a simple test jig to be made.

I plan to make that jig as soon as I finish approximately 125 other items on my backlog of items on the "to do" list.

I did finish wiring my water heater 3/18/17, had my first hot shower since 12/10/17, the day my credit card was hacked for the first time..

Art "Titanium Cranium" Welter
Hot shower...life is good Art!
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Ivan Beaver

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Re: Best way to test speakers that return from a rental?
« Reply #9 on: March 20, 2017, 08:37:15 pm »


REW, a freeware program does good impedance testing,
An impedance curve (assuming it has enough data points) could be the easiest thing to do.

You just need a reference curve before it goes out.

There are no mics or worrying about positions etc.

You just need to make sure there is not a lot of noise while doing an impedance measurement and the front of the speaker is reasonably free of reflections.

The impedance curve can show a lot of little things that start to be a problem.

Just be sure to not use much smoothing or those little clues will dissappear.
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Brad Gibson

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Re: Best way to test speakers that return from a rental?
« Reply #10 on: March 20, 2017, 09:46:17 pm »

What is your process when a speaker comes back from a rental to make sure it is still in good condition?

Now lets throw a powered speaker at this situation.  How are we getting an impedance curve if the speaker has an amp built in?
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Tim McCulloch

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Re: Best way to test speakers that return from a rental?
« Reply #11 on: March 20, 2017, 11:44:51 pm »

Now lets throw a powered speaker at this situation.  How are we getting an impedance curve if the speaker has an amp built in?

You can't without opening up the cabinet or modifying it.

You're back to acoustic testing.

Are you having specific issues now or it this meant to be preemptive?
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Matthew Knischewsky

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Re: Best way to test speakers that return from a rental?
« Reply #12 on: March 21, 2017, 01:10:46 am »

We currently use this method and it seems to work about 90% of the time.  Do you know of a full proof tester that will take the guess work out of the equations?  Im looking to take the human error factor away.

While not impossible to "remove" the human factor it may become cost and time prohibitive to do so. You need a

As others mentioned, tone sweep will tell you most of what you need to know. Combine with a FFT measurement will tell you if it's in the ballpark.

Establish a test procedure- This area of the warehouse, this location, this mic, etc then document it. Make initial captures of your inventory, using serial or inventory numbers to keep track. You're not going to get laboratory results but that's not what you're looking for- you're looking for the trends in magnitude response, not necessarily absolute measurements. If the speaker passes the tone test, the FFT compared to a previous trace will show any other problems fairly clearly, such as a polarity reverse, drivers lower in level or non functional, passive components damaged etc.

For lack of a better and easier test I've made this work for as long as I've been using Smaart, It's very eye opening when problems do pop up, and it's a great way to learn how to make a good measurement and use discretion when in the field.

Matt
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Chris Grimshaw

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Re: Best way to test speakers that return from a rental?
« Reply #13 on: March 21, 2017, 04:36:42 am »

I'd go for an acoustical measurement, but ignore the frequency response almost entirely. Look at distortion.

If one mid driver out of four is toast, chances are it's gonna make some nasty raspy noise at some frequency, or the other three drivers will be working harder. That'll show up quite obviously in a distortion measurement. Same for a bass driver that's had beer poured over it - the cone will end up a lot softer, and that's gonna show problems too.

Inventory moving around isn't a problem, so long as nothing rattles during the sweep.

Chris
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eytan gidron

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Re: Best way to test speakers that return from a rental?
« Reply #14 on: March 21, 2017, 05:34:23 am »

What is your process when a speaker comes back from a rental to make sure it is still in good condition?

Outline makes a nice and useful unit for testing multiway loudspeakers -

http://outline.it/outline-products/loudspeakers/browse-by-series/grand-touring-outline/fastqc-ls/

It's designed for Outline speakers bat can be used with any type of speaker as long as it is not powered and as long as it doesn't have capacitors in series. Very useful for testing line arrays.
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Brad Gibson

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Re: Best way to test speakers that return from a rental?
« Reply #15 on: March 21, 2017, 05:45:13 pm »

You can't without opening up the cabinet or modifying it.

You're back to acoustic testing.

Are you having specific issues now or it this meant to be preemptive?

Not any real problems at this point.  We are all about making processes and continually improving them.  I have learned everything I know by reading and asking questions.  Everyone has something to offer if you just shut up and listen. 

Thanks Tim, I have learned tons from you and will continue to listen. 
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Adam Daube

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Re: Best way to test speakers that return from a rental?
« Reply #16 on: March 21, 2017, 06:20:57 pm »

What is your process when a speaker comes back from a rental to make sure it is still in good condition?

I tone sweep my rig as others have stated. but at the same time I check the impedance of every driver, first with a whirlwind cabdriver (for fast checks, it only gives me an led for 4,8 or 16 ohms) and then I have a test cable jig made up to test each component with my meter with out having to open up the cabinet.

My tone sweeps are normally just ear tests. testing with Smaart in the shop has too many other interferences. 
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