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Old 14th August 2012, 05:31 PM   #1
VA2GXB is offline VA2GXB  Canada
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Default Go FR? Keep what I have? Improvements?

Hi all,

A few years ago, I built a 2-way system with Fostex FE83Es and Dayton DC-160s. I plotted the tapered quarter wave TL I wanted, and favoured 'bass' over the midbass...
Click the image to open in full size.

And after two years of listening, and some recent measurements, that dip is there! It's there and it's very noticeable. Orbital's Impact USA(The World is Burningiversion) lacks what it should have. Actually, anything Orbital for that matter doesn't sound right!

Thus, I wonder... Plus, my valve amp will be on the way from Ireland in the next few weeks (Immigration...don't start) and I'm wondering if 88dB will cut it. That's on paper, and I have not yet modded my measurement mic (WM-61A) to check the real-world efficiency.

Rear-loaded horns for the DC-160s? Space and WAF are not really an issue.

I have zilch complaints for for the FE83Es. I'd be sad to retire them in face of a fullrange - I'd like to keep them and fill out the <300Hz area properly. Right now, as you see, it's lumpy. I'm at work on lunch and cannot post my sweeps, but suffice to say, the dip is there!!
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Old 14th August 2012, 05:41 PM   #2
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A Cookson place for that dip. What is you xo frequency and how are the drivers laid out? You may want to put the woofer near the floor.
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Old 14th August 2012, 06:14 PM   #3
VA2GXB is offline VA2GXB  Canada
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Click the image to open in full size.

XO'd originally at 300Hz each, first order.
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Old 14th August 2012, 08:09 PM   #4
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Stupid auto correct Cooksen = common.

You could try and place the woofer near the floor. Or use two woofers. One near the floor, the other near the fostex.
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Old 14th August 2012, 08:36 PM   #5
ra7 is offline ra7  United States
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Does MJK's spreadsheet model floor bounce? It looks like midrange ripple from the TL, not floor bounce.

You can check whether its floor bounce by modeling the speaker and its floor reflection in Edge. Make the mic distance and location the same as that used for actual measurements. Results are pretty accurate.

A woofer close to the floor will have its first dip from floor bounce pushed higher in frequency. It should be crossed to the mid/full range driver, which is at ear level, before the first dip, and the mid/full range drive should be crossed above its first dip.

Last edited by ra7; 14th August 2012 at 08:40 PM.
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Old 14th August 2012, 08:52 PM   #6
VA2GXB is offline VA2GXB  Canada
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I thought as much, Ra7. That dip disappears if you model the line stuffed to hell. I think it's destructive interference from a standing wave established in the TL. Also, measured dip is there at 50cm, 1m and listening position (~4m). It's from the TL, definitely.

Last edited by VA2GXB; 14th August 2012 at 08:56 PM.
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Old 14th August 2012, 10:02 PM   #7
ra7 is offline ra7  United States
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Great... now you know.

These might be helpful:
Box colourations - really ?
Best sealed enclosure for completely supressing back wave
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Old 14th August 2012, 10:05 PM   #8
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Oh ok. I didn't understand that it was showing up from the box. Good luck.
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Old 14th August 2012, 10:30 PM   #9
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I reckon if you moved that Fostex off-centre things would improve quite a bit.
Try taking it out of the box and putting it on a baffle (cardboard will do) and have it offset.

I would also consider dual woofers purely for the fun factor with one close to the floor.
2.5 way
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Old 15th August 2012, 01:21 AM   #10
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Sound bounces off all room boundaries. Usually there's a ceiling too, hence my move to dual woofers one at the floor and another up by the midtweet. I think I'll do another of my early (1980 or so) successes that had two 8s and four peerless cone tweets. I didn't know anything but I was young and I was improving, like J Mellencamp says. It made music.

Last edited by phivates; 15th August 2012 at 01:26 AM. Reason: "cone"
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