Speaker Bench Test

[evilorange]

I'm rebuilding a set of Bose 901's, series V speakers.

Before you Bose haters start razing me about the type of speakers I’m working with, let me state that the speakers and most of the materials are hand-me-downs and the goal of my project is to enjoy a speaker rebuild and learn more about the mechanics of speaker fabrication. Don’t worry; I’m planning to build a set of speakers from scratch, down the road.

My question to the experienced is what is a good method for bench testing each of the (18) speakers. I removed all of the speakers from the two cabinets for inspection and to replace the surrounds. After the surrounds are replaced what are my options to test each speaker before I install them back into the cabinets?

The speakers were stored in a garage where they were exposed to a lot of moisture and dust. What other parts of the speakers should I inspect for problems while I have them out of the cabinets? Also, can the magnets weaken in strength, and is there a way to test them?

Let the craziness begin!!!

 

[ocool_15]

moisture may not be the best thing for a assumed paper cone. There mechanical Q would have changed with use but youll have to measure that anyhow.

 

[evilorange]

The cones seem to be intact but a few of the magnets have some corrosion on the bottom side.

 

[pinkmouse]

For a quick and dirty check, you need an amp, 10W is plenty, and a signal generator.

Start off with a sine wave at about 10 Hz, with enough level just to get the cone visibly moving. If the driver is ok, you should hear absolutely nothing. Run your fingers lightly around the surround, and make sure nothing is moving that shouldn't. Slowly increase the frequency, making sure the driver doesn't exceed Xmax, and if you hear any change from the pure tones of the sine wave then you have problems.

If all sounds good, then stick them in the boxes and fire them up. A little surface corrosion on the hidden parts won't hurt a thing.

 

[evilorange]

Thanks PinkMouse.

Can you suggest a good, bare-bones, signal generator I can purchase or build?

I'm assuming I need an audio oscillator.

I have an nad power amp.

 

[ocool_15]

Might I suggest True RTA free 1 octave Link before shelling out some money. But they do have ones up to 1/24 octave for $99.
I have been very happy with their software. If you only need <100Hz look for bass cd's at car audio shops. The one USACi dB drag cd did 20-80Hz in 1Hz increments. Drive By Bass has 10hz -100hz in 10hz increments.

 

[pinkmouse]

Yes, you could use a free software based signal generator to get going, there are many to choose from and they all do much the same thing.

As for building, there are many projects out on the web, I myself, built one based on the Maxim Max038 chip that works fine for me.

As for buying, have a look round eBay, S/H test equipment over in the US seems to be really cheap and redily available.

 

[evilorange]

Hi PinkMouse.

Unfortunately my computer notebook is very old and does not have an audio out jack. I will need to build or buy a signal generator.

Please explain what you mean by “S/H test equipment”. Can you suggest any models specifically? I might try to build one. Is there a diy kit available that a novice could handle?

Thanks

 

[evilorange]

Can anyone give me some more feedback?

 

[Skitch72]

I have always thought this looked interesting:

Function Generator Kit

Tim