Cheap 12" woofer on clearance

[Mazeroth]

Elemental Designs is closing out their entry level EHQS 12" subwoofers for $13.50 each. I purchased a 4 pack of them a few months back when they sold for $25 each and was pretty impressed for the price. At $13.50 each it's a great deal if you want to dabble with a cheap dipole speaker or some other fun project. Shipping for 4 is the best deal because they fit four in a box and the rate doesn't drop much if you go to 2 or 3.

http://www.edesignaudio.com/edv2/product_info.php?t=1&products_id=183

2 ohm and 4 ohm versions available.

[bikedave]

Ib?

Anyone know, would this work at all as an IB? Thinking like 8 of them?

[ThomasW]

The Qts is too low so the system would be overdamped. And the Xmax is way to low unless you plan on buying several dozen.

In the long run it would be better to buy the bargain Fi IB-15"s with their 22mm of Xmax. They'll be sold for $129ea or $119 ea in lots of 4. Both prices include shipping.

[bikedave]

Gotcha, appreciate the response!

[Mazeroth]

Now, for some measurements of this beast...

I went to Mazurek's house the other night to measure the distortion of these 12s (curiosity got to me) since my measurement setup is giving me crap lately, plus I wanted to see Arta do its thing. I left the subs in their test dipole enclosure (see pic below) and only wired up the top driver. Neither of us are experienced in measurements, yet, so we calibrated the output at 1m and placed the mic at 1 ft from the driver dust cap. This was just a quick way to try to see its distortion profile. I knew under 50hz it wasn't great so I'll let you be the judge of that. I'm sure there was some dipole cancellation happening as well but we didn't want to get super close in case we damaged his calibrated microphone. We played a 100 hz. tone and used his Radio Shack meter to calibrate the level.

Drivers in enclosure



80 dB @ 1 meter; Microphone @ 1 foot



90 dB @ 1 meter; Microphone @ 1 foot



100 dB @ 1 meter; Microphone @ 1 foot (Definitely reached xmax on this one! We also had to stop a bit past 100 hz. because it started to hurt our ears.)

[mazurek]

I went to Mazurek's house the other night to measure the distortion of these 12s (curiosity got to me) since my measurement setup is giving me crap lately, plus I wanted to see Arta do its thing. I left the subs in their test dipole enclosure (see pic below) and only wired up the top driver. Neither of us are experienced in measurements, yet, so we calibrated the output at 1m and placed the mic at 1 ft from the driver dust cap. This was just a quick way to try to see its distortion profile. I knew under 50hz it wasn't great so I'll let you be the judge of that. I'm sure there was some dipole cancellation happening as well but we didn't want to get super close in case we damaged his calibrated microphone. We played a 100 hz. tone and used his Radio Shack meter to calibrate the level.

Haha, let me qualify a couple of those things. I'm not sure what the best measurement distance is for in room distortion measurements for a dipole. I think 1 foot might be a good compromise to minimize intrusion of room effects, but still get a picture of the fundamental level. I'm also a believer in measurement conditions not being very critical as long as comparisons are done within a family using similar measurements.

The distance was also set to avoid overdriving the signals at higher test levels, not necessarily to avoid microphone damage. I'm thinking about getting a much better calibrated microphone so I always know the absolute SPL level at microphone so it does not go near spec'ed levels.

[Dennis H]

Yeah, mic distortion is a factor at higher SPL levels. You don't know if the distortion you are measuring is the mic or the speaker. Looking at the Girardin mics on the Liberty Instruments page, you can hit 3% distortion as low as 116dB or as high as 140dB depending on which mic model and which preamp you use.

http://www.libinst.com/hispl.htm

[Mazeroth]

The distance was also set to avoid overdriving the signals at higher test levels, not necessarily to avoid microphone damage.

Nah, I wasn't worried about blowing one of the drivers. In fact, I think it would have been pretty funny!

My intention is to build a pair of inexpensive dipole line arrays with 6 drivers in each, in my basement, in 7' towers (floor to ceiling). Looking at the distortion in picture one the levels aren't too bad above 40 hz., which should be pretty good for music. Here's the actual distortion at 40 hz.:

THD 2.65%
Dist2 2.47%
Dist3 0.93%
Dist4 0.68%
Dist5 0.27%

That's for one driver at 80 dB @ 1 meter. If we raise that to 12 drivers and increase the wattage by 12 as well it should yield the same distortion at 101 dB (if my math is correct). Now, we would also get the benefit of the line array so the distortion should drop even more. It should make for a neat experiment and at only $162 for the 12 drivers a cheap one as well. :T