Fast, fun, Inexpensive OB project

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That's a very interesting idea, Mr. T

Effectively you are giving the inductor a lower impedance to work into, as well as a smoother one.

That will have 2 advantages:
  1. Lower impedance means smaller inductor for the same crossover point. (That's why 4 ohm drivers are good - or 2x 8)
  2. The parallel resistor acts like a Zobel on the top end of the impedance curve, flattening it out.

However, that 3 ohm resistor in your schematic will pull the impedance way down, to about 2 ohms.
So I simulated an 8 Ohm parallel and 3.5mH series on the SLS woofer - in place of the single 13mH that was there.

Not bad, not bad! Impedance never drops below 4 Ohms, and the overall sensitivity is much better. I did have to change the HP on the tweeter to get it to work, but no big deal.

I'll see if I can find a 3.5mH coil and give it a try. Hope that reality mirrors the sims :)
 
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I tried the parallel resistor/smaller inductor trick. It worked.

In place of the 13mH on the woofer I did 4mH + 9.2R parallel (cause it's what I had). Then used 10uF on the tweeter instead of 5uF+5.5R.

Overall the midrange came up, but the sims said it would. Not too bad, just need about 2~3R series with the tweeter to balance it out.

Will play and report further.....
 
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Hi Peter - yes, those woofers look like they should do the trick. Qts and Fs are similar to the Peerless 12.
We can hope that they play up to 2K with no big problems.

Which tweeter will you use?

BTW, you can use an 8ohm resistor in parallel with the woofer and a smaller coil if you want to. Something around 5 or 6 mH. Then tune the tweeter crossover a bit to meet it.
 
Hi,
We can hope that they play up to 2K with no big problems.

I have used them before and do not think it will be a problem if those Peerless functions. For the moment I have not decided if I'm going to order a new pair or buy four used 16 ohm version.

Tweeter will be Dynaudio Esotec D260, they should be able to handle a low second order filter or maybe even first order.

Peter
 
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Very cool.

At the moment I'm running mine with the old ScanSpeak 3806 mid/tweeter. Crossover is 100Hz low pass (1st order) on the woofer - 1100Hz L/R (2nd order) hi pass on the tweeter with about 9dB attenuation.

This basically makes a LP shelving filter for the woofer that fits the baffle size nicely.

Keep us up to date on the project!
 
MrTwister,

Gosh, at that CHEAP price, 4 ohm, 90dB, Qts >!, maybe 4 per side in series / parallel would still give 6dB gain (total 96dB?) at total 4ohms? Is that right Pano?

Anyone have SPL graph of it on an infinite baffle? Any subsequent response irregularities in an OB could then be smoothed by a DCX2496? maybe?
 
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It's an interesting looking driver, and cheap for sure! The thing does actually calculate out to the same SPL @ 2.83V as the Peerless. But it should give more low end, with that high Qts. (4 ohm load)

My guess is that it would play down to about 30Hz on the same size baffle. And yes, 4 of them should give you ~96dB at 4 ohms. That's good, as you will always end up trading away that SPL to make up for open baffle loss. And 4 ohms means a smaller inductor, too.

The trouble is - how does it sound? Being that cheap it's hard to imagine its upper range could be very pretty. That's where the Peerless shines. It's a great sounding driver.

Also tried the Eminance Acoustinator 12" neo on the rig with pretty good results. A little louder and lower than the Peerless, even tho it specs almost the same. More crossover work, tho.

I ran this rig for awhile with the SS3806 mid-tweet and loved it. JB also built one and came up with a great 4 element crossover. 4 elements! Alas the SS3806 is no longer made. Maybe a nice 2~3" fullrange driver could takes its place.

Thanks for posting the 12. Worth playing with at that price.
 
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Hi Ian - the x-over was for the Peerless woofer with the SS3806. It is as follows.

12 MH on woofer (iron core type)
12R series on Tweeter
2.7 - 4.0 MH Tweet shunt
5 to 6 MFD Tweet cap (Flavor to suit taste).

So 2 coils a cap and a resistor. That's all. Feel free to tune a bit to your ear and your room+amp.

This was very popular at the recent LSAF.

Hope you enjoy it.


Just FWIW, I covered the face and wings of mine with felt and then a layer of faux suede. It helped a lot. Maybe only the sharp edges need it, I don't know.

These are best palced on stands with thewoofer about 40cm (15") off the floor. On the floor they can get too heavy in the lower midrange. This also puts the tweeter near ear hight.
 
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No, there will not be a 2 woofer version, unless someone else builds it.

I spoke with John about it, he says it not worth the trouble. Because fo the baffle size you don't really gain much with a second woofer - and you start to run into polar response problems when trying to combine it with the tweeter.

And any way, the tweeter always runs out of steam before the Peerless woofer, so why worry?