MakeMineVinyl
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Spkr
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Open Baffle Cone Speakers
- Thread starter MakeMineVinyl
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D
Deleted member 133
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I'm too baffled to comment!
When properly designed, tuned, and placed, I find open baffle speakers to be pretty good sounding. Because of their output characteristics, the bass is tighter and more open, similar to outdoor PA subs, and the imaging can be pretty spot on, like headphones yet with room ambience. They require large enough rooms that the rear wave travels a god distance before reflecting back at the listening position, like 6 to 10 feet out, so the length of the room needs to be pretty high, like 20 feet or more. With the bass output containing both direct and out of phase content, the room resonances are vastly reduced and it tightens the impact and reduces nulls and modes. That said, the woofer has to have a 6dB/octave slope EQ which rises as the frequency gets lower. This means the woofers have to handle a massive amount of power if the output at 240Hz (or whatever the baffle size directly forward) is to be matched at 60Hz. That's two octaves, or 12dB or a 12x increase in watts. So 100 watts at 240Hz requires 1,200 watts at 60Hz. These things need TONS of power and lots of speakers. That's why most open baffle fullrange speakers tend to have two to three 12 or 15 inch woofers which increases efficiency per watt and supports the high demand at low frequencies. It also requires electronic EQ and/or crossovers for the bass portion.
The imaging is aided with considerably less off access early reflections, or at least much more diffused off axis reflections since the rear out-of-phase waves counteract and interact with the front in the off access areas in the room. You don't need acoustic treatments, or at least you can use lots less room acoustic treatments to get pretty darn good results with seemingly faster bass (because the resonances don't form), more diffuse and extended ambience, less early reflections, and so on.
All of that is only good news if everything is done very well - the right speakers, design, setup, placement, and room environment. I've heard the Orions in a room which was close to ideal for them, and I was VERY impressed down to about 70Hz. Below that they suffered and I recommend an Infinite Baffle subwoofer to the owner. He bought a JL Lab subwoofer instead and hasn't stopped complaining about how hard it is to get the sound to blend. I've also heard large planar speakers which have the same characteristics as these open baffle speakers in the right rooms and they sounded pretty great as well. The trick is the bass below 80Hz is hard to match without huge speakers and amplifiers or mismatching to traditional subs.
It is far easier to go with standard speakers to get great sound if you don't have a very large dedicated music room.
The imaging is aided with considerably less off access early reflections, or at least much more diffused off axis reflections since the rear out-of-phase waves counteract and interact with the front in the off access areas in the room. You don't need acoustic treatments, or at least you can use lots less room acoustic treatments to get pretty darn good results with seemingly faster bass (because the resonances don't form), more diffuse and extended ambience, less early reflections, and so on.
All of that is only good news if everything is done very well - the right speakers, design, setup, placement, and room environment. I've heard the Orions in a room which was close to ideal for them, and I was VERY impressed down to about 70Hz. Below that they suffered and I recommend an Infinite Baffle subwoofer to the owner. He bought a JL Lab subwoofer instead and hasn't stopped complaining about how hard it is to get the sound to blend. I've also heard large planar speakers which have the same characteristics as these open baffle speakers in the right rooms and they sounded pretty great as well. The trick is the bass below 80Hz is hard to match without huge speakers and amplifiers or mismatching to traditional subs.
It is far easier to go with standard speakers to get great sound if you don't have a very large dedicated music room.
Dentman
Well-Known Member
Interesting.
I've never seen anyone I know have enough room to place rear radiating type speakers correctly. Well I should say they weren't willing to place them correctly in many circumstances.
I'd love to hear these in the right room. Still more orthodox designs make more sense to this laymen.
I've never seen anyone I know have enough room to place rear radiating type speakers correctly. Well I should say they weren't willing to place them correctly in many circumstances.
I'd love to hear these in the right room. Still more orthodox designs make more sense to this laymen.
My uncle had purchased the former small grocery store in the little town he lived in as the town was dying. He emptied the space and put his huge top of the line Martin Logans in the middle of the room, angled so they aimed perfectly to a single lounge chair placed 9 feet away. No other treatments of balancing was done. The nearest wall was about 15 feet away and the ceiling was about 12 feet high. The results were stunning! He kept it that way for about a year before he refurbished the space into a home.
The room I heard the Linkwitz Orions in was about 30 feet long and 22 feet wide. The speakers were placed about 1/3 of the way into the room and the seat was a little further into the room from the back. So, about 10 feet from the front wall for the speakers and about 12 feet from the back wall for the listening seat. The side walls were about 7 feet away from the speakers. The front wall was covered with a very well made built-in bookcase filled with books and a few knick-knacks, much like Linkwitz's listening room. The rear wall as bare with credenza on it. The sound down to about 60Hz was really amazing. He had a massive Krell amp driving the woofers and a Pass Labs amp on the midrange and tweeter(s). I really loved the sound, but it needed something for the low bass.
TitaniumTroy
Well-Known Member
Linkwitz's current design (LX521) uses a rear facing tweeter for increased ambience. I did hear the Orions at the first AXPONA show, I didn't think they were far enough away from the front wall. Bass was boomy to me, however I do like to read his articles and agree with a lot of what he says.
While I do love the sound of some planer speakers, I have yet to hear an open baffle cone woofer system I truly like. However I have only heard them at audio shows, never in a audio dealer or a home setting.
While I do love the sound of some planer speakers, I have yet to hear an open baffle cone woofer system I truly like. However I have only heard them at audio shows, never in a audio dealer or a home setting.
It is difficult to setup a system in a large room effectively, so showrooms and more trade show settings are not ideal.
That said, there a ton of really poorly designed open baffle speakers out there to make the entire concept seem terrible. For instance, based on physics it makes no sense not to make the baffle as wide as reasonably possible, yet many products cut the baffle as narrow as possible, even shaping it to be narrower than the woofers where they can. That is foolish and really impacts the bass performance. Even the Linkwitz Orions have added "width" in the form of a u-shaped baffle to ensure the baffle reinforcement is reaches a low as is reasonable.
That said, there a ton of really poorly designed open baffle speakers out there to make the entire concept seem terrible. For instance, based on physics it makes no sense not to make the baffle as wide as reasonably possible, yet many products cut the baffle as narrow as possible, even shaping it to be narrower than the woofers where they can. That is foolish and really impacts the bass performance. Even the Linkwitz Orions have added "width" in the form of a u-shaped baffle to ensure the baffle reinforcement is reaches a low as is reasonable.
I built a dozen of the VOTT cabinets as well as the smaller version which I used in my PA system for nearly a decade. When I started designing my own horns, I discussed the principles with many brilliant people, including Paul Klipsch, and it was made abundantly clear to me that an ideal horn would have the exact same acoustical impedance on both sides of the compression driver - making it more like an infinite baffle load.
With the short throw low compression load on a woofer in the A7 enclosure, the rear enclosure is a standard bass reflex design, tuned via the port blocks sometimes seen in installations in the 1960s and 1970s. Even the versions with the 811 horns in the port lowered the "vent" tuning, but then decreased the enclosure volume resulting in a lower resonance, but lower efficiency.
The low compression on the 15" woofer is limited in its pressure on the acoustic output, but it balances well with the bass output and acts to somewhat match the dynamic performance from the 15" woofer with the high dynamics of the 811 horn and driver. That's why it is such a legendary design - it blends well which most horn mid/tweeter mated to direct radiator woofers failed to do.
Anyway, if you can keep the subwoofer crossover high enough to compensate for the backwave interaction of the A7 woofer with an open back, you should be fine. It should be more dynamic this way, but the bass could have a 6dB per octave drop off below the frequency defined by the baffle and side wall distance from the back wave to the front wave. I don't have the A7 schematics, but I estimate that distance is about 3.5 feet, which translates to a begin of the slope starting at 130Hz. But that is a guess at this point.
As for the compression/horn loading, it should make any difference. The loading on the front horn and compression area is not very low in frequency - it stops acting like a horn at about 300Hz.
With the short throw low compression load on a woofer in the A7 enclosure, the rear enclosure is a standard bass reflex design, tuned via the port blocks sometimes seen in installations in the 1960s and 1970s. Even the versions with the 811 horns in the port lowered the "vent" tuning, but then decreased the enclosure volume resulting in a lower resonance, but lower efficiency.
The low compression on the 15" woofer is limited in its pressure on the acoustic output, but it balances well with the bass output and acts to somewhat match the dynamic performance from the 15" woofer with the high dynamics of the 811 horn and driver. That's why it is such a legendary design - it blends well which most horn mid/tweeter mated to direct radiator woofers failed to do.
Anyway, if you can keep the subwoofer crossover high enough to compensate for the backwave interaction of the A7 woofer with an open back, you should be fine. It should be more dynamic this way, but the bass could have a 6dB per octave drop off below the frequency defined by the baffle and side wall distance from the back wave to the front wave. I don't have the A7 schematics, but I estimate that distance is about 3.5 feet, which translates to a begin of the slope starting at 130Hz. But that is a guess at this point.
As for the compression/horn loading, it should make any difference. The loading on the front horn and compression area is not very low in frequency - it stops acting like a horn at about 300Hz.
D
Deleted member 133
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I frequently can't remember where I put my cell phone. Or what I had for breakfast. Or where I was going with this thread...
You, my friend, amaze me with the amount of "stuff" that you remember (and know).
Jeff
TitaniumTroy
Well-Known Member
Yeah but Jeff, you can remember the Four Floors of Whore's story. I think that is what it was called, I can't even remember where the remote is.
You, my friend, can stand up for every obscure Canadian who ever existed. That's a talent in itself.
I love a handful of things: music, speakers, tech, etc. I don't know sports, cars, women, or any of the millions of common things most men are experts at.
Oh... and if you have the backs open, I'd close off the front ports.
malsackj
Well-Known Member
So by closing the ports your reaching back to the infinite baffle. The larger the baffle and the correct tuning on the speaker and were back on the infinite baffle. Next time your out this way with a large group and GTG I should let you run the outside rig. explaining what we are hearing and what adjustments. I have the 4530 jbl scoops and the EV TL15-1 with 2226 inside. 4.9 cu ported and by closing one port on the EV we can take them down to 30 hz.