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...
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 Burning
iversion) 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!!
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...
An externally hosted image should be here but it was not working when we last tested it.
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 Burning
iversion) 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!!
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.
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.
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Great... now you know.
These might be helpful:
http://www.diyaudio.com/forums/multi-way/215133-box-colourations-really-17.html#post3081510
http://www.diyaudio.com/forums/mult...pletely-supressing-back-wave.html#post3101885
These might be helpful:
http://www.diyaudio.com/forums/multi-way/215133-box-colourations-really-17.html#post3081510
http://www.diyaudio.com/forums/mult...pletely-supressing-back-wave.html#post3101885
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.
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The null that you are looking at is typical of end-loaded TL's. By placing the driver some distance down the pipe, this null can be pretty much eliminated. Exactly where the driver should be depends on the taper ratio of the pipe. For a straight MLTL, it's 25%, more taper, closer to the closed end of the pipe.
Bob
Hmm! In that case, as I thought, a complete rebuild will be necessary. A few hours need to be spent with the spreadsheets. I was considering horns, as I'll soon be using an amp less powerful <5W/ch, and will need very efficient speakers - which are often full range...which often need more reinforcement lower down. Or - to use the same drivers that I have, and rely on the horn's acoustic gain (a large rear-loaded for the DC160 and front-horn, for want of a better term, for the Fostex) to make up for the electromechanical inefficiency
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Just FYI - This is the 1m plot - in the corner. An anechoic chamber would be nice! Re the low SPL levels, my WM-61A is not yet modified to >80dB. But, on a relative level, there are dips where the simulations say there ought to be...
An externally hosted image should be here but it was not working when we last tested it.
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