ErichH and I had great weather today for doing outdoor measurements of some waveguides and other stuff. Weather was great for people running their leaf-blowers and lawnmowers, too, but we managed to work around them.
First, a shot of our 21st century test setup. That's ErichH trying to hide behind the SEOS18. If you look close, you can see the chalk marks on the concrete indicating the measuring angles. The control console is a laptop computer sitting on an upturned rubbish can. We used an old Advent speaker sitting on a folding table to raise the test subjects well above ground.
Here are some curves of SEOS12, using a DE250 driver. Measured at 2m distance, about 5' off the ground.
Horizontal patterns (measured in 7.5 degree steps, 0 to 90 degree range, curves unsmoothed):
Vertical patterns:
Harmonic distortion (at around 90dBSPL, 2m):
red is 2nd Harmonic, pink is 3rd, green is 4th, light blue is 5th, dark blue is total. Ripple is from ground reflection (since measuring at 2m distance)
I'm asking out of genuine interest. Why measure outside? Inside would be quiter, and you were only 5' off the ground. When I measure outside I usually hike it up over 8'. And usually only bother for sub-500hz interest. Is there still an advantage doing it outside like you've done? Thanks.
Quote:
Originally Posted by tuxedocivic /forum/post/21144037
Very nice.
I'm asking out of genuine interest. Why measure outside? Inside would be quoted, and you were only 5' off the ground. When I measure outside I usually hike it up over 8'. And usually only bother for sub-500hz interest. Is there still an advantage doing it outside like you've done? Thanks.
Measuring outside so as to get data down to around 500Hz (my living area is too cluttered for getting really clean data down there). Need a lot of area to deal well with getting polars. It can be done inside, but not as easily.
Also because distortion testing is annoyingly loud and others are indoors (and not terribly appreciative of the sweeps... like my neighbors are
That's great, Bill asks me to get things lined up.......then goes at tries to take a photo while I'm moving it around! You know that's a big waveguide if it can hide my meat head!
It looks like we're right in line with the house, but it's actually moved up more than the photo shows.
By the way, I think that's over 5' off the ground.....or I'm shrinking!
Are you using a version of Omni not available to the public as of yet? I just upgraded to the latest version from PE's site and see no mention of the polar information, either from a new tab or from the help information. Thanks.
Quote:
Originally Posted by exojam /forum/post/21144389
Bill,
Are you using a version of Omni not available to the public as of yet? I just upgraded to the latest version from PE's site and see no mention of the polar information, either from a new tab or from the help information. Thanks.
Parts Express has the newer version and should be putting it up on their website shortly. Till then, you can get it here: OmniMicInstall.exe
If you are doing polars, it would be a good idea to look at the Help. There is an auto-filenaming feature now, which makes it easier to generate a set of frd files to form polars from. Essentially, you set up for measurements and then right-click in the freq graph and choose the "Configure Auto-increment" function with a dedicated directory for each set, a basic file name (or use the default), a starting angle, and an increment value. Then to save successive measurements at each angle, you only have to right-click in the graph again, then hit enter twice, it will save the file with the angle embedded in the file name, for a successive series of files. To show the polar graph all together, use the "Curves Add" menu and select all the files in the set, which will show the fanout of all the curves. Then click on the "polar" button (an "advanced function") and you get to the polar maps and radar plots -- for those you probably want to normalize the curve to the default curve where it would be EQ'd flat. Unless you are measuring an already-equalized and crossed-over speaker, that is. Anyway, it's pretty easy after you finally get how to do it.
Even the first horizontal polar graph, which doesn't seem to agree with the second.
The former shows that directivity, as evidenced by equal spacing between the curves, is held down to ~1200 Hz, where they start to converge, but the latter (sonogram?) doesn't seem to start to expand significantly until ~800 Hz.
If I'm not misunderstanding how to read these, which one is right?
It does, when you get down to where it loses control (below 800Hz). Or in the vertical curves, where the directivity drops gradually all the way through...
As for how it worked out that way, you'll have to ask the guys who really designed it (I only participated to vote on size and outside shape issues). Head back into the early pages of the "Hey guys..." thread here on AVS. Of course, following in the footsteps of Geddes and Keele.
"Am I mistaken that the first horizontal plot shows directivity decreasing at 1200 Hz?"
you kind of have to pick an off-axis spl where you want to call it at. most choose something between -6db and -12db. in this case that gives you a result of 750-850hz in the horizontal.
the off-axis at 90 degrees does begin to collapse around 1200hz, but that sound is down around 25db or more vs. the on-axis, so it really doesn't matter.
Quote:
Originally Posted by LTD02 /forum/post/21144662
you kind of have to pick an off-axis spl where you want to call it at. most choose something between -6db and -12db. in this case that gives you a result of 750-850hz in the horizontal.
Great work guys. Thanks for the effort. Nobody's time is free and setting up for polars takes time.
These measurements look great. They are smooth out past 45 which is nice and they will be even smoother on an wide baffle or rounded over baffle.
These will cross great to a 15 but better to a 12. It isn't doing much in the vertical below about 1500hz. That is hardly a deal breaker when crossing to a 15 around 1100-1200hz, but not as good as the SEOS-15.
If a cheaper version is made available, I'd be comfortable with it being the SEOS-12. It wouldn't be the uber-performer that the SEOS-15 or 18 will be, but it will be pretty damn close and allow for a more normal sized box. I would guess that the actual audible differences will be small.
I was thinking that their might be some differences in the relative dimensions of the 10, 12, 15 and 18 thereby influencing the pattern and control of the sound wave. If there isn't then it follows that the measurements should be exactly the same above 2k or so.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
AVS Forum
34M posts
1.5M members
Since 1999
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, TVs, projectors, screens, receivers, speakers, projects, DIY’s, product reviews, accessories, classifieds, and more!