I've gone through so many project ideas and drafts trying to figure out what I'd like to build to replace my existing system (SVS Prime 5.2) but I keep coming back to the same basic problem - I need a horizontal matching center channel at 8.25" or less of height. And I don't want to build just any old design either, I want it to be something special in some way. I figure that it's time to flip the script and start from the center design.
I'm looking for fairly wide HT coverage, not one sweet spot. Size constraints mean that I'm most likely looking at an MTM or WTMW configuration (more on that in a second). Some controlled directivity would be nice but I'm not making it a priority. And then there's the problem where horizontal speakers generally don't provide good off axis characteristics. That got me thinking, why not do a design with a coaxial or full-range center, flanked by some woofers crossed low enough to avoid combing/lobing? Then I can use the same design but larger woofers in the towers.
Alright so obviously I'm not the first person to think this and there are some existing discussions, but mine is a little different. I'm planning to make this an active speaker powered by a Hypex 2-way or 3-way DSP plate amp, and I'm willing to put some money in compared to many of the well known DSP designs. Call it...$800 flexible ballpark for amp, driver, misc non-wood parts, less is appreciated. It seems like it's hard to predict the behavior of coaxial drivers from the spec sheet charts alone, so I'm looking to drivers that are known to perform well but could really be cleaned up with some DSP.
From here I need some help putting me on the right basic track for reading/research/planning. What would be some good drivers to consider? What woofer xover point am I aiming for to avoid off-axis issues? I was thinking of using the Seas clear-cone seen in the Loki design. (Although the simplicity of the xover in the Loki calls into question whether an active biamp is really useful here.)
Any information or input is appreciated, particularly comments that get me closer to a highly performing but unique speaker.
I'm looking for fairly wide HT coverage, not one sweet spot. Size constraints mean that I'm most likely looking at an MTM or WTMW configuration (more on that in a second). Some controlled directivity would be nice but I'm not making it a priority. And then there's the problem where horizontal speakers generally don't provide good off axis characteristics. That got me thinking, why not do a design with a coaxial or full-range center, flanked by some woofers crossed low enough to avoid combing/lobing? Then I can use the same design but larger woofers in the towers.
Alright so obviously I'm not the first person to think this and there are some existing discussions, but mine is a little different. I'm planning to make this an active speaker powered by a Hypex 2-way or 3-way DSP plate amp, and I'm willing to put some money in compared to many of the well known DSP designs. Call it...$800 flexible ballpark for amp, driver, misc non-wood parts, less is appreciated. It seems like it's hard to predict the behavior of coaxial drivers from the spec sheet charts alone, so I'm looking to drivers that are known to perform well but could really be cleaned up with some DSP.
From here I need some help putting me on the right basic track for reading/research/planning. What would be some good drivers to consider? What woofer xover point am I aiming for to avoid off-axis issues? I was thinking of using the Seas clear-cone seen in the Loki design. (Although the simplicity of the xover in the Loki calls into question whether an active biamp is really useful here.)
Any information or input is appreciated, particularly comments that get me closer to a highly performing but unique speaker.
A woofer and a coaxial would be my first move. You'll be able to keep everything within 1/4-wavelength at the crossover frequencies, so dispersion will stay wide.
Your call on 2.5 or 3-way design.
I'd avoid full-range drivers, because they tend to get beamy and/or rough in the top octave.
The Kef coaxials generally have a good reputation. I played around with some of the basic (smooth metal-looking 3" cone in an egg-shaped cabinet) ones a few years back, and found they did very well when crossed around 400Hz to an 8" woofer.
Chris
Your call on 2.5 or 3-way design.
I'd avoid full-range drivers, because they tend to get beamy and/or rough in the top octave.
The Kef coaxials generally have a good reputation. I played around with some of the basic (smooth metal-looking 3" cone in an egg-shaped cabinet) ones a few years back, and found they did very well when crossed around 400Hz to an 8" woofer.
Chris
Without a doubt, the best CC speaker for home theater with multiple listeners across the horizontal plane is a curved horizontal line array. Everybody gets the the exact same FR no matter where they are sitting. Not an easy build and not inexpensive, but worth it in my mind.
I could be wrong but I think this was made by Rick Craig at Selah Audio. Currently, I don't see it on their website.
I could be wrong but I think this was made by Rick Craig at Selah Audio. Currently, I don't see it on their website.
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With some of the synergy based systems used on the mains, you don't even need a center channel. I get a solid center image no matter where I sit in my room, and some chairs are way off axis.
I made a 2 way center with a Vifa ring radiator and peerless midranges.
The off-axis performance is really not as shabby as you'd think based on measurements alone, I don't think you have to worry about this too much.
If I did this again though I'd use FaitalPro drivers for the mid-woofers. Better power, and better high frequency performance.
The off-axis performance is really not as shabby as you'd think based on measurements alone, I don't think you have to worry about this too much.
If I did this again though I'd use FaitalPro drivers for the mid-woofers. Better power, and better high frequency performance.
The configuration used in Revel C52 should address your issues.
See,
Revel C52 Speaker Review and Measurements | Audio Science Review (ASR) Forum
With a height of 8.25" for the speaker, you should be able to find some suitable drivers for this kind of design.
Kurt
See,
Revel C52 Speaker Review and Measurements | Audio Science Review (ASR) Forum
With a height of 8.25" for the speaker, you should be able to find some suitable drivers for this kind of design.
Kurt
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-coaxial's aren't great for off-axis performance either. The deeper the cone profile, the greater the pressure loss off-axis past a certain point. (..and even the "flatter" ones have some "waffle" in a 30/30 window.)
Better suggestion for excellent broad horizontal dispersion:
Tang Band W3-1878 3" Full-Range Driver
HiVi RT1.3WE Isodynamic Tweeter
Steep crossover at just about 4 kHz.
Better suggestion for excellent broad horizontal dispersion:
Tang Band W3-1878 3" Full-Range Driver
HiVi RT1.3WE Isodynamic Tweeter
Steep crossover at just about 4 kHz.
Lots of good information so far, thanks. I'm wondering now if I should stay conventional and go to a WTMW configuration for the center channel. I know some KEFs and ELACs are well loved but coaxials seem to be challenging. Then again I might just grab the Seas and roll with it.
What exactly is the challenge? I'd choose a high quality 5" mid and tweeter 2 way, covering ~120hz and above...2 way or 3 way..sure, just nothing configured on the horizontal plane.
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If the center is for HT, rather than music playback, you might be able to ease up on the need for control of frequency extremes, as often for HT most of the center channel signal is only voice range.
1. Forget the coaxial unless you are OK with some pressure deviation nearing 30 degrees or more.
..even the little one here has at least a 2db pressure drop between 4 and 8 kHz at 30 degrees (and you aren't going to do better than this):
Loudspeaker shop | Omnes Audio CX 3.0 / 3.1 | DIY
2. Pick drivers with broad stable horizontal dispersion as high as you can get for each respective driver.
3. Make sure you crossover appropriately for those drivers with respect to their dispersion patterns and non-linear distortion. This often means a steep filter, which shouldn't be a problem with a DSP active solution.
4. Generally, use a WTMW like the Revel (shown in link) does. This removes stress from the mid. driver and allows for a lot more power-handling (particularly when you consider baffle-step compensation). Remember that most of the front channel sound comes from this single speaker. Crossover should be near 350 Hz.
Shown below are the dispersion responses for the drivers I recommended (..though the tweeter is very slightly different from the one I posted):
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