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B&K sweep function generator to test speakers


Dave A

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A guy who has repaired speakers for me in the past used a frequency generator to test speakers with. Has anyone here done this and if so can you explain exactly what this does? I bought a B&K 3011B off EBay pretty cheap and can duplicate the sounds I heard when the speaker guy did it but don't know how to interpret what I hear.

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It is certainly a neat piece of equipment and apparently will allow you to generate tones of any audio frequency.  In the old days something like this, plus a lot of other equipment, like a strip recorder, calibrated microphone, distortion analyzer, and anechoic chamber  could be used to test speakers and other audio equipment.

 

There is a big “however” and it has to do with the personal computer and sound card revolution over the last decade.  The first step about 20 years ago was expensive programs and hardware like LMS and CLEO and Audio Precision.  Not inexpensive but they allowed much better measurements and analysis.

 

Now REW is a freeware program where you need a calibrated microphone and the appropriate sound card. 

 

As before it takes some study to understand the result and what to do about it.  There is a lot of on-line support. though.

 

Overall, if you want to investigate your speakers, you should study REW.  Your purchase is by many standards a dinosaur and only a small part of an assembly of equipment used long ago.  Sorry to say.

 

WMcD

 

 

 

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OK I can believe in software because I use it daily for design and machining. I looked at REW though and it appears to be for a different purpose than analyzing a single driver for things like voice coil rubbing. The guy I saw use one went from low to high Hz and back and would listen for any frequencies that caused strange noises and check ohms out to. If they had no bad noises and ohmed  OK he would say they were good. What I want to do is specifically test individual speakers for problems. How does REW allow for that? I don't care about rooms I just want to check drivers with speakers I am working on.

 

  I have the B&K manual and thanks for the link. What I want is to talk to someone who has used one of these before for speaker testing.

 

  I am open to alternatives but the speaker rebuilder used a function generator and this thing only cost me $59.00 with shipping so if it does the job I don't want to look further.

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13 hours ago, WMcD said:

There is a youtube showing how to center a voice coil to avoid buzz.  Some tone generator freeware apps for use with Apple and Android are shown.

https://www.youtube.com/watch?v=NpMYZq-qQNo

 

WMcD

 OK that has bearing on what I want to do. I specifically and only I am interested in working on a speaker or driver one at a time to verify there is no voice coil problems primarily rubbing of any sort. Again what I want is feed back from someone who has used this type of device to analyze this specific problem of voice coil rubbing which I assume this is for. I want to speak to someone who has done this with this type of equipment to learn specifically what to do. The guy who was using this type of device is considered the best speaker recone guy in Nashville now and he checks speakers this way. I assume since he does it for a living there is a reason he does it this way. He is not going to show me how to do this so I need advice from someone who will be willing. I want to know why he does it this way and not with software and IPads phones etc.

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You can use a combination of a signal generator and an AC voltmeter to determine things with drivers like free air roll-off, (approximate) along with finding out (F3?) the port tuning of a enclosure. It's old school compared to the software programs available now, but it gets reasonably close...

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Nothing wrong with a function generator. I have an HP3312A   does sweeps  am, fm sine square triangle.. Its on top of my scope so always there.  Very easy to adjust  compared to having a laptop on your bench and have to mouse all the menues.    Its also bullet proof and if i do damage it I dont have to trash an unrepairable  laptop mother board.  it is handy to use for electronic troubleshooting too..  

 

So having said that, other comments are correct,  Unless you have a calibrated mike and proper room the tests you can do are really only qualitative. 

Whatever you do, do NOT sweep full frequency at high power levels to your speakers.  The power handling of wooffer, mid and tweeter are corelated to the energy content at those frequencies.   Lots of energy in the woofer frequencies so those can handle lots of power. but a tweeter only handles like 5% of the sound energy so it can only handle a few watts.  So if you set your generator up at say 100Hz and crank it up, then sweep over the mid and tweet you will fry them.  

 

 

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