Here is my version of an easy to build highly efficient speaker.
Estimated at 96 db @4 ohm. The woofers are Klipsch 1089-av from the RF-7 mated with the new Heil AMT. 1st order series crossover - coil and cap. The woofers are in Push - Push or Bipolar. They fill in the baffle step very well and integrate the bass in my room better than anything else I've had. I'm running them with a modified 300B Ming-Da PP but my meter says I'm using only 2W@4ohm for eye-wincing volume.
THE SOUND IS AWESOME IMHO!
I would compare it with the Tannoy Churchill if anyone knows of these.
Estimated at 96 db @4 ohm. The woofers are Klipsch 1089-av from the RF-7 mated with the new Heil AMT. 1st order series crossover - coil and cap. The woofers are in Push - Push or Bipolar. They fill in the baffle step very well and integrate the bass in my room better than anything else I've had. I'm running them with a modified 300B Ming-Da PP but my meter says I'm using only 2W@4ohm for eye-wincing volume.
THE SOUND IS AWESOME IMHO!
I would compare it with the Tannoy Churchill if anyone knows of these.
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It's just a 12' x 44 ' x 17" bass reflex ported box with bipolar disorder. 2 speakers - one on the front and back - but it takes care of the baffle step better than I thought it would, and without help in the crossover that could muck up the signal. Mid woofs wired in parallel. 2 x 4" x 6" ports. The Heil tweeter beats the Klipsch's use of the Tractrix horn and the mid-woofs are fast enough to keep up with a ribbon. Very few 10 inchers will do that. I crossed over about 1750hz - lower than the Klipsch design and this takes out some harshness from the mids as the cones approach breakup. VTV ran an article on the RF-7's but I have not seen it yet. Will be interesting when I get the issue. I don't know why people are so reluctant to use bipolars, after all most instruments radiate omnidiretionally. Most people say the musicians are right in the room with them when they hear these.
I would have made that speaker a 2.5-way. I don't remember at all if the AMT is a dipole, but if it is, I would wonder if there wasn't some sort of phasing weirdness between the rear woofer and the front of the AMT that could be causing frequency response irregularities. The baffle step frequency for those speakers should be low enough that the wavelengths would be long enough not to cause weirdnesses. Though I am not sure if efficiency would be badly impacted.
Al M. I found the woofers on e-bay. Put them on an automatic watch for you. They pop up from time to time. Or call Klipsch and see what they will do for you. Or find some RF-7 with shipping damage - again contact the dealers. BTW these have shamed my beloved Clonac 2.5's - oh well, they have served me well for years.
JohnL. I built them and they came. This is why I placed the tweeters on top, so I could move them back and forth. Placement does not seem to be too critical. The Heils are actually Bipolar also. The element is a vertically pleated accordian shape that delivers the same phase signal on both sides. The element placed in the vertical plane of the front woofer coil seems to work well. Transients are reproduced very well, unlike the horn that klipsch uses.
BAM A 2.5 design would have large inductors/capacitors somewhere in series with 1 or both woofers. This causes phase shift between and/or low damping of the woofs, IMHO introducing many problems. I think part of the reason my design works is that only a .39mh inductor and 20uf cap is used. This is why the bass is so tight and articulate. At 1750 hz there is very little coming from the rear woofer to interact with the AMT. Also, due to room placement any highs from the rear woofer have a long way to travel and many boundaries to bounce/absorb sound before hitting the listener.
JohnL. I built them and they came. This is why I placed the tweeters on top, so I could move them back and forth. Placement does not seem to be too critical. The Heils are actually Bipolar also. The element is a vertically pleated accordian shape that delivers the same phase signal on both sides. The element placed in the vertical plane of the front woofer coil seems to work well. Transients are reproduced very well, unlike the horn that klipsch uses.
BAM A 2.5 design would have large inductors/capacitors somewhere in series with 1 or both woofers. This causes phase shift between and/or low damping of the woofs, IMHO introducing many problems. I think part of the reason my design works is that only a .39mh inductor and 20uf cap is used. This is why the bass is so tight and articulate. At 1750 hz there is very little coming from the rear woofer to interact with the AMT. Also, due to room placement any highs from the rear woofer have a long way to travel and many boundaries to bounce/absorb sound before hitting the listener.
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