!2" PE Buyout woofer measurements

[dlneubec]

I picked up 4 of the 12" deal of the week from a couple weeks ago @ $15 each and finally got around to doing some measurements of them. I'm pleaseantly surprised at the FR and impedance plots. Attached is a near and far field merged plot of the FR, and an impedance plot.

I have never used the CSD plot or distortion plot section of SoundEasy and never read how to, so take the plots I'm also attaching of a CSD and distortion plot of this driver with a huge grain of salt. However, I had it hooked up and decided to give it a shot, FWIW. Obviously something is amiss, since I have no F2 showing up!

I wonder how they'd do for a low cost, high bang for the buck WMTMW, wired parallel and crossed to something like the Tangband w704s 5" at around 200hz and maybe a neo tweeter at 3500-4000hz or so. The drivers for each speaker would be less than $100!

[dlneubec]

Here is a link to them.12" buyouts

[Dennis H]

It looks like the green F2 line is there buried in among the others. I don't know what the heavy green line at the bottom is.

[augerpro]

Hi Dan. I thought I'd share a couple tips regarding these measurements since I had a hell of time getting good information.

Re CSD: The number of samples changes how far in time the grapph displays. I use 4 samples which is 3.0 ms. Zaph also uses this setting. Occasionally with bigger drivers, especially big PA drivers I'll also do at at 7 samples (5 or 6 ms I think) to see farther out in time since these drivers tend to take longer to settle down. The window size is the same (or slightly smaller) than whatever you use for a gate for the SPL measurement to avoid reflections. For example I often use a 6.7 ms gate which is a 326 window width for MLS measurements. Just to make sure I don't include any reflections in the CSD I may cut the window down to 300 or so. Reflections really mess up the CSD. Also whatever level you plot the response at in the MLS screen that is the level the first "slice" will be in the CSD screen. Zaph plots his response so that the "usable" area of the response is roughly at 75 dB. This will enable to you to see the the decay in response over 35 dB in the CSD screen. Occasionally I plot at 85dB in the MLS screen so I can see the decay over 45 dB. I really don't know at what level the decaying response is still audible but I figure 45 dB down is probably close enough to inaudible.

The first "slice" should be the actual driver response and starts wherever you place the marker in the MLS screen. I place mine as you would if you took an SPL measurement, i.e., at a distance reflecting the distance from baffle face to the mic. Zaph gets in a little closer to the impulse peak. Try both and see which you like. I saved my impulses so I may go back and change mine to how Zaph does it. We'll see.


Re THD Make sure the mic preamp output uses a Y splitter to run to BOTH the left and right input on the soundcard. I use a radio shack SPL meter to roughly set the volume of the DUT and then use the mic gain on the preamp so that the usable portion of the response plots around the 0 dB level. This is pretty approximate and reflections make it kind of a guess. Just make sure that any peaks in response don't get up to around +10 dB because the mic input will clip and cause everything to spike. Take a look at my M8N measurement adn you'll see what I mean. The cone breakup causes the SPL level to hit around +10dB and everything spikes.

The green line on the bottom is %THD. You can change the scale to 0-10% to make it more usable. It seems to be a generic computation which I don't rely on much. It doesn't seem to give much weight to higher orders, which are more offensive. Biggest thing you can do here for accuracy is the environment. I have foam baffles at the first reflection areas on the floor, ceiling, and to the sides of the baffle. I also use big, thick Coleman sleeping bags behind the mic. I had a lot of reflections off the back wall bouncing back off the baffle and to the mic without them. I also covered the back of my baffle with that asphalt sound deadening sheets. Mic distance is a more complicated. You'll have to figure that otu on your own! Let me know if you find some good guidelines.

Hope that helps,
Brandon

[dlneubec]

Thanks, Brandon. That's great information! I'll save this post to refer to when I decide to give it a go again.

I was encouraging John Kreskovsky to write one of his users guides for the distortion testing sections of SE. That would be helpful for us new users.

[augerpro]

I was encouraging John Kreskovsky to write one of his users guides for the distortion testing sections of SE. That would be helpful for us new users.

I'd love to see it! In fact Zaph mentioned maybe doing a tutorial on Bl(x) extraction which I'd love to start doing. I read the manual on it, but haven't tried it since my free time is pretty much filled with speaker building projects along that thing called "life". Hopefully some insight on do's and particularily don'ts would be very helpful. So Zaph if you are reading, please ;x( :rofl:

[Jed]

I just downloaded ARTA and will try doing some distortion measuring with this software. Looks promising too, for us LSPcad 6 users that don't have distortion measuring capabilities built in.