| Re: Tim's 4Pi Speaker Build [message #81033 is a reply to message #81032] |
Sun, 25 January 2015 19:16   |
timkur
Messages: 13
Registered: November 2012
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Cutting the rounded corners for the waveform.
I really like the look of the recessed waveform, but I didn't really know how to cut the rounded corners to fit it in.
This is the approach I took.
First, I traced the outline of the waveform onto the baffle. The distance from the edge of my router to the bit is 2 5/16", so I created another large rectangle around the waveform trace. I needed to clamp pieces of scrap around the baffle to get the guide lines to fit, since 2 5/16" went off the piece on 3 of the edges.
Once I did that, I clamped down straight edges on the outer rectangle to create myself a temporary jig.
Then I ran my router all around the jig, and cut out a rectangle. This was easy, as the jig prevented me from cutting something I wasn't supposed to cut.
I thought long and hard about how to cut these corners. That was really the tough part of this cutout. Ultimately I ended up using a dremel. The rounded sanding bit made it pretty simple to cut the rounded corners. I would have preferred a method that didn't require a steady hand, but I was stumped.
Overall, it was a nice fit. I'm sure a real woodworker would have been able to do it better, but I'm happy with it.
Tim
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| Re: Tim's 4Pi Speaker Build [message #81034 is a reply to message #81033] |
Sun, 25 January 2015 19:32 |
timkur
Messages: 13
Registered: November 2012
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Chancellor |
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First impressions... uh-oh.
Once everything was cut out, I decided to do some quick sanding and put all the pieces in and try it out before painting it.
I plugged it all in, set it up to do an easy A/B testing with my M&Ks, and started playing some music, expecting to hear pure awesomeness. The bass was definitely more full, but something seemed to be missing on the higher end. My wife said something along the lines of "you probably don't want to hear this, but this sounds muffled compared to your existing speakers." And she was right.
I'm in the process of building 3 of these, so I swapped out the tweeter, midwoofer, and crossover one at a time, and there wasn't any effect.
I was wondering if this was just the case of "different types of speakers sound different", but I wanted to do some measurements anyways to make sure things were ok.
I grabbed a copy of HOLMImpulse (folks seemed to like it and it is free), pulled out the calibration mic that came with my receiver, and stacked my M&K on top of the 4pi... I wanted to make sure the speakers were super close to rule out any room effects. The mic was about 9 feet away.
The results were pretty clear... I did something wrong with the construction of my 4pi.  M&K's are blue, 4pis are red.
Any suggestions what I did wrong?
I purchased the B&C DE250 8ohm driver... was that the correct one?
Also, as a reminder, I purchased used JBL 2226H's from eBay, which were originally 4 ohm versions but according to the seller were reconed to be 8 ohms.
Any suggestions?
Thanks!
Tim
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| Re: Tim's 4Pi Speaker Build [message #81039 is a reply to message #81037] |
Tue, 27 January 2015 01:04 |
timkur
Messages: 13
Registered: November 2012
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Chancellor |
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Thanks Wayne. You definitely had me worried.
I started by swapping out the one 2226H for the other 2 that I had. The other 2 were phase wired correctly (not reversed like the first one... now I know what to look for).
The speaker/mic was in a slightly different place compared to yesterday, but both of them had similar curves.
I was pretty frustrated at that, and so I looked at your response charts on the website, and something caught my eye. They were very similar to the vertical off-axis response (down) chart that you have. So I played around a bit, put the original speaker back in (that had the bad curve in the previous reply) and raised my microphone 2 feet up.
From what I can tell, this was a measuring error and not a speaker issue. Is that how you would interpret this?
Apparently these are pretty finicky when it comes to vertical placement. I'm guessing you've got a post somewhere that describes the best way to align the speakers. When I get a chance, I'll look for it and if I can find it, I'll post a link here.
Thanks!
Tim
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