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Lindelium18
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17/08/2019 8:25 pm  

@123toid

Also, in reference to the 1k - 2k hump, I’m crossing over at around 500-600hz with a 2nd order so I don’t think it’s going to be much of an issue. 


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123Toid
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18/08/2019 10:50 am  

@lindelium18

There's a few things you can check. The first is to go to whatever box program you used (ie WinISD) and check for first port resonance. This will be on the screen that informs you of port length and size. See if that is anywhere near your problem area. Second, you can line the inside of the box with an old mattress pad or closed cell foam. If it happens to be standing waves, that should help.


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Lindelium18
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18/08/2019 3:32 pm  

@123toid

Ok, I double checked winisd and my first port resonance is 1,036hz so I don’t think that’s an issue. Next, winisd shows a flat response down to about 60hz, then about a 1.5db increase to 45hz and then back to 0db at 38hz with an f3 of 33hz and an f10 of 27hz. 

So, my next step will be lining the inside of the enclosure. I have three basic options. I can go pick up poly-fil. I have enough 1” acoustic foam (the two color stuff you put on walls to trap reflections) or I have enough (probably) Safe n Sound rockwool left over to do that walls with that. Any of those better than any others?


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123Toid
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18/08/2019 3:51 pm  

@lindelium18

I would use the acoustic foam you have.  Typically for a ported enclosure you don't want to use loose polyfil, one main reason, is it coming out the ports.  Believe it or not, the main thing I use is cheap mattress toppers I pick up from Walmart.  Sounds kind of silly to some people, but it works great for this and is pretty cheap.  I haven't done any real tests, but from others that have, supposedly one of the best is recycled denim insulation. 


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Lindelium18
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19/08/2019 12:52 am  

image

 

Well @123toid , this is getting pretty frustrating...  This is both woofers, after adding the acoustic treatment. It is virtually identical to the measurement without treatment...  I’m not sure what do do at this point...


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123Toid
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19/08/2019 1:34 am  

It would appear to be a problem with the room, which you'll want to fix with you room eq of your av receiver. It's the reason the room equalizer is on your receiver. Unfortunately none of us have the perfect room. Or at least I should say not many of us. O of the ways to test if it's your room is to take measurements from different distances. First start out as close as you can to the speaker without touching it. Then keep backing it up until you see the null. If it


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Lindelium18
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19/08/2019 2:30 am  

@123toid

I’ll do that again tomorrow (forgot to save those results or take pictures) but I did about 1.5 ft, and about 6 feet. All three graphs looked almost identical...


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123Toid
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19/08/2019 2:37 am  

@lindelium18

Definitely do an up close measurement, that will give you an idea if it is the speaker.  Having said all this, I'm not sure it is as big of an issue as it looks like on the graph.  Our ears don't hear sharp dips like that.  What you may want to do is change the smoothing of your graph to ERB.  ERB is one of the measurements that will give you a more accurate representation of what the speaker will actually sound like to your ears.  It is definitely worth a look.  Of course, the final test is to listen to some material and see if you hear the loss as well. 

I should mention at 1.5 feet you are getting a lot of room in your reading from about 500hz and below. 


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Lindelium18
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19/08/2019 10:10 am  

A089C713 FC1D 4F4B 953F 25E47C497DAD
3956DDC5 DEB8 41C8 8C76 61D085017252

 

Graph is the measurement yesterday from 3 feet and then the measurement from the picture. Again, almost identical.  Normally I’d agree about the peaks and valleys being virtually inconceivable but this is a 10db swing over like 30hz within the male vocal range.  But at this point, I don’t even know what to think... for a half second, I thought maybe it was my mic but if I play the two tones at the peak and valley, it is definitely an audible difference. 


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Lindelium18
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19/08/2019 10:15 am  

@123toid

could it be the small amp I’m using to drive the test?!  That just came to me as an option that I’ve been ignoring.


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123Toid
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19/08/2019 6:17 pm  

@lindelium18

It is doubtful it's the amp, but it always could be..  One might assume it is the driver, but since I also have this driver and have finished a design with it, I know that is not the case.  So if your up close measurement still looks off (ie it is not the room), then there's only two possibilities that I can think of.  Either you do not have enough bracing or you have a small air leak.  What does your bracing look like?  If you do not want to do an up close measurement, you could always try another speaker int he same location to see if you are getting a similar dip.  If you are, then it is the room/location. 


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Lindelium18
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19/08/2019 8:22 pm  

@123toid

bracing is ok but not extensive.  Is there a good way to determine where more needs to be?  As for any possible air leaks, I’ll double check that. 


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123Toid
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19/08/2019 8:28 pm  

@lindelium18

The general rule of thumb is every 12 in needs a brace.  That is a generalization though.  You can try a knock test.  If your hear it resonate you need more bracing there.  If you get a solid thud, you may not.  Looking at your speaker, I probably would have a window brace on each inside of the woofer and three brace in between those two going the width of the center (down the middle).  I typically round over the insides of the braces as well.  You can see a version of what I do here: https://toidsdiyaudio.com/community/diy-speakers-diy-speakers/the-uglies-tower-and-surround-build-log/#post-376

I probably should have added some vertically, but I didn't this time.


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Lindelium18
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19/08/2019 10:18 pm  

@123toid

Just when I thought I could put the router away...  ok, I’m not sold on my issue being either of these problems but I’m out of ideas so what the heck, right?  I’ll get to fabricating some bracing soon but I guess I’ll check all the seals first. 


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Lindelium18
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19/08/2019 11:42 pm  

@123toid

When will the response graphs for the Esoterics and Corundum be coming out?  


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