Cleaning a driver

[Silver1omo]

I found a cheap Sharp active subwoofer in a street market. Took it home and was not working. Took it apart, re attached everything and now is pumping some bass. I will try to run some test tones tomorrow and see how bad it does :P

Now for the question. The driver has a LOT of dust, very likely got wet at some point. What can be used to clean a driver without causing damage?

By the way the enclosure says cp sw7500 and the driver it is ~10" (25cm), DVC and it says to be 6 + 6 ohms at max 240w. It has printed rsp za056awzz and mt a04 4927.

This is what I got using ARTA and the audissey mic that came with my rec:

Image not available

[robfive]

I use dry microfiber coths to clean my drivers. They work well for removing dust without needing solvents. If your sub has imbedded dirt from getting wet at some point you may need something more potent. I would start with a microfiber cloth as it will not harm your sub and go on to more heavy duty products as needed.

[Silver1omo]

I used a microfiber and got a lot of dust off. It does have embedded dirt. What is a good thing to start with?

[Silver1omo]

After googling a bit it seems that is the sub of the mini component CD-G10000

[fjhuerta]

Looks as if it was ported at 38 Hz. A bit high for a sub. Maybe a new cabinet could help...

[Silver1omo]

Looks as if it was ported at 38 Hz. A bit high for a sub. Maybe a new cabinet could help...

Definitely, I want to do that, the original enclosure is fugly.
The bad part is that I don't have gear to measure the driver and when asked Sharp for info I got the brochure info :P

I'll have to wait...

[Undefinition]

This is top secret info. You can't tell anyone, but you can measure driver T/S specs for [essentially] free.

At Liberty Instruments' website, they have the program Praxis, which is like the God of measurement programs. They offer a free version, which is stripped down, but still has a number of handy features. One of the free features is the ability to measure T/S specs. You do have to build some very simple testing probes, however the parts to do this are available at your local Radio Shack for a few dollars

There's also Limp (part of ARTA). I don't know how "crippled" its free version is, however it can also measure T/S specs.

Finally, there's Speaker Workshop, which is a messy beast of a program, but it will also do it for you (you'll need one of the user guides to help you, though)

I've made it this far without ever purchasing or using a Woofer Tester. :W

[Silver1omo]

This is top secret info. You can't tell anyone, but you can measure driver T/S specs for [essentially] free.

At Liberty Instruments' website, they have the program Praxis, which is like the God of measurement programs. They offer a free version, which is stripped down, but still has a number of handy features. One of the free features is the ability to measure T/S specs. You do have to build some very simple testing probes, however the parts to do this are available at your local Radio Shack for a few dollars

There's also Limp (part of ARTA). I don't know how "crippled" its free version is, however it can also measure T/S specs.

Finally, there's Speaker Workshop, which is a messy beast of a program, but it will also do it for you (you'll need one of the user guides to help you, though)

I've made it this far without ever purchasing or using a Woofer Tester. :W

Downloading Praxis and googling for the test probes
I also have LIMP installed, will have to check how to measure...

EDIT:

The Limp manual shows an easy setup using the phone out. I'll give it a try :P

[Silver1omo]

So I tried using limp with the setup of the manual and got the zma files (1 for each VC). The impedance seems to be very big compared with the info in the driver. The driver says 6+6 and I got a minimum of 21.955...
Anyway, I will try other methods.

Ignoring that, how would you do the calculations of a DVC driver?

I'm attaching both VCs ZMA.

Edit:
Very likely is because I used the headphone out... I'll try to use the speaker leads of the laptop and see what I get.

[Undefinition]

With a DVC woofer, you'll want to hook up both terminals (run them in parallel, most likely) when you measure.

Yeah, that Zmin sounds weird. What size reference resistor are you using? (What does Limp recommend? I have no idea)

It may take a few days and a bunch of fiddling to get good measurements. That's the nature of the beast.

[Silver1omo]

LIMP's manual recommends 100 ohm, I used 98.5 and 121.6. The results were pretty much the same. I'll see if I can use the speaker lead of my laptop and see if it makes any difference.

To measure, should I mount the driver to a open "baffle"? Or sitting in a hard surface will do?

I'll try other drivers around here and see what I get.

[Silver1omo]

BTW, what do you use? and what is your setup like?

[Silver1omo]

Before performing surgery in my laptop to get the speaker lead I decided to test with another sound card. A friend has a USB Soundblaster XFi. I got pretty much the same, but the calibration of LIMP was better so I want to trust it better.

Then I decided to measure with the VC's in parallel and got something that looks a bit better. Measured with pink noise and sine. The file is the sine measurement.

The Zmin is 5.744 and max 18.869

[Undefinition]

Yeah, that looks like a woofer, all right! :B I think that's probably the real impedance. However, do you have any "normal," commercially-available drivers you could test as a control to make sure your setup is accurate?

Why did your measurement stop at 500 Hz?

Also, could you possibly do a screen capture next time (ALT+Print Screen, saved as a .GIF or .JPG?). It's faster for us than download your file, renaming it as .ZMA and load it into speaker software?

[Silver1omo]

Yeah, that looks like a woofer, all right! :B I think that's probably the real impedance. However, do you have any "normal," commercially-available drivers you could test as a control to make sure your setup is accurate?

Why did your measurement stop at 500 Hz?

Also, could you possibly do a screen capture next time (ALT+Print Screen, saved as a .GIF or .JPG?). It's faster for us than download your file, renaming it as .ZMA and load it into speaker software?

I'm waiting for a pair of w4-1337, once I have them I'll measure them.

It stopped at 500 cause that is how I configured it, I'll do a full range measure later, perhaps today. Is 10-20k ok?

I'll definitely post the graph when I get the full range measure.

I have been waiting like forever for the w4s and neocd3s. I hate the Mexican postal service...

[Silver1omo]

Here we have a new measurement from 10 to 20k using pink noise. I may try step sine later.



Also the ZMA.

I really want my w4s

[Undefinition]

Looks good. I have to admit that the Fs seems a bit high for a sub, however you said that this came out of a sort of "low end" retail unit. So maybe it was optimized to get a certain "punchy" sound around 60-80 Hz (and not so much play "sub bass")

[Silver1omo]

Very likely, I have no high hopes for this. But for the price if I can get something that provides some bottom end and learn, I will be happy :P

Now I need to get a scale to measure with added mass and get everything.

If we trust my setup I get:
Thiele-Small parameters:

Fs = 55.64 Hz
Re = 3.15 ohms[dc]
Le = 282.36 uH
L2 = 898.77 uH
R2 = 14.62 ohms
Qt = 0.93
Qes = 1.15
Qms = 4.86
Mms = 56.38 grams
Rms = 4.052354 kg/s
Cms = 0.000145 m/N
Vas = 22.20 liters
Sd= 330.06 cm^2
Bl = 7.356068 Tm
ETA = 0.32 %
Lp(2.83V/1m) = 91.21 dB

Added Mass Method:
Added mass = 20.00 grams
Diameter= 20.50 cm

[Silver1omo]

I got my pair of TB w4-1337, I will measure them and see if I get something close to spec.

How do you measure the Xmax of a driver?

[Silver1omo]

Well, this is what I got from measuring the W4-1337. I measured directly out of the box. No break in.



What you guys think? Does it look accurate?

[Silver1omo]

What you guys think of that impedance plot? Close to what you would expect of a w4-1337?