Yes, tho maybe less with U-frame. The common mistake is to put them too close to the wall. I gave a big pair of OBees to a buddy and he liked them, but thought they were a little bass shy. I told him to move them out for the wall and he said "Wow! These do have bass!"
First time we visited John at this house, he did a great demo. He had a few pairs of speakers lined up in his garage. The wall behind the speakers was the garage door. At the push of a button, we could remove or replace the wall behind the speakers.
What a difference! With the "wall" in place, mid-bass energy was fat and full, remove the wall, low mids gone. But the image did extend 15' out into the driveway. A very educational demonstration. Wall or no wall. Mid-bass or none.
The effect was still there on box speakers, same changes, but not nearly as pronounced. U-fame might be between the two.
First time we visited John at this house, he did a great demo. He had a few pairs of speakers lined up in his garage. The wall behind the speakers was the garage door. At the push of a button, we could remove or replace the wall behind the speakers.
What a difference! With the "wall" in place, mid-bass energy was fat and full, remove the wall, low mids gone. But the image did extend 15' out into the driveway. A very educational demonstration. Wall or no wall. Mid-bass or none.The effect was still there on box speakers, same changes, but not nearly as pronounced. U-fame might be between the two.
Yes, U frame does seem to cause a bit of argument and confusion though I'm inclined to think they are very similar to H frame especially at lower frequencies. I was interested that you said they could be too far from wall, I wasn't aware of that, I thought farther away the better. So, am I reading the demonstration right, the wall was supporting the mid bass but had a negative effect on the low bass? Oh, the demo in the garage was with box speakers?
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The demo was in a typical American 2 car garage - with no cars in it. The "wall" behind the speakers was the garage door, 16 feet wide, 7 feet high. We were standing in the garage looking out. That garage door lifts out of the way at the push of a button. 3 or 4 pairs of speakers were on display and were tested, open baffle and closed box.
The change in the mid-bass was the most profound, so it was the most noticeable and memorable. I've thought for years about the possible change to the low bass, and wondered why I don't remember it. Removing the wall behind the speakers should change the low bass, but it might have been masked by the big mid-bass change. The room did feel different with one wall missing. More open, of course. That seems obvious, but we rarely get to hear acoustics changes so quickly.
The "wall" behind the speakers was the garage door, 16 feet wide, 7 feet high. We were standing in the garage looking out. That garage door lifts out of the way at the push of a button. 3 or 4 pairs of speakers were on display and were tested, open baffle and closed box.The change in the mid-bass was the most profound, so it was the most noticeable and memorable. I've thought for years about the possible change to the low bass, and wondered why I don't remember it. Removing the wall behind the speakers should change the low bass, but it might have been masked by the big mid-bass change. The room did feel different with one wall missing. More open, of course. That seems obvious, but we rarely get to hear acoustics changes so quickly.
Pano - that is a really interesting: Recently I have been working a bit with the Quad ESL57 and when reading about your observations it struck me that Peter Walker actually dampened the rear of the electrostatic panel with some burlap (or whatever it is called: some very rough brown fibres which is much loved by dust!) and the rear of the treblepanel is completely covered by felt. The contention is that removing the felt also removes the "sparkle" of the treble and that the dampening of the bass-panels' rear radiation makes it easier to place speakers in the room. Considering your experience in the garage it might be worth a try to follow in Walker's footsteps and dampen the rear radiation of the Manzanitas. Few listnening rooms have garage doors! (I'll certainly have a go at it later but so far the Quads must remain in place for a while.)
Hmmmm... Yes, I can see the damping on the rear of the ESL57 making it more of a cardioid pattern. I remember playing the 57s close to the wall, and it didn't seem to hurt them.
With an open baffle the pattern is dipole, or figure 8. The nulls are to the sides. The wall behind the speaker is necessary to reflect the back wave around to the listener. Without that wall the low end disappears - goes out the window, so to speak. That's what happened when we opened the garage door behind the speakers. Getting too close to the wall also hurts bass. The wall needs to be there, but not too close. It's not hard to find a good balance by moving the speakers back and forth.
With an open baffle the pattern is dipole, or figure 8. The nulls are to the sides. The wall behind the speaker is necessary to reflect the back wave around to the listener. Without that wall the low end disappears - goes out the window, so to speak. That's what happened when we opened the garage door behind the speakers. Getting too close to the wall also hurts bass. The wall needs to be there, but not too close. It's not hard to find a good balance by moving the speakers back and forth.
I find this surprising. I would have thought that without a reflection from the back wall, the bass would be stronger from a dipole source since the anti-phase component would be missing.
I'd like to experiment with this myself.
I have generally enjoyed the sound of most good speakers I have heard when outside more than inside, but then I don't like the sound of most rooms!
I seem to understand it the way Russell explained it. The bass reflecting from the rear wall actually is out of phase with the front and is the cause of the early low bass roll off in an OB. Low Mids will not be so affected. In fact it can increase them due to addition depending on the reflected phase. At very low frequencies the wavelength is so long that there is no time for the phase to come back again in phase. At higher frequencies this is possible due to a much shorter wavelength though the returning wave will be at a lower level due to losses.
So removing the rear wall will cause it to sound 'lighter' in the mids , though low bass should get better !
Another thing is that between a H and U frame of similar depth the 'bass null' is in the cabinet middle for the H frame and at the rear end for the U baffle.
Any kind of absorbent at the back will decrease the reflected rear signal . Hence the loss will be decreased compared to plain OB.But losses depends on the type of absorbent used. Most simple types usually aren't so good at lower frequencies ! Should make a difference in the lower mid ! Maybe slow down the velocity of the rear wave with absorbents ?
But generally speaking I like speakers playing in the open ! Had the luxury of being able to do this for a few years !
So removing the rear wall will cause it to sound 'lighter' in the mids , though low bass should get better !
Another thing is that between a H and U frame of similar depth the 'bass null' is in the cabinet middle for the H frame and at the rear end for the U baffle.
Any kind of absorbent at the back will decrease the reflected rear signal . Hence the loss will be decreased compared to plain OB.But losses depends on the type of absorbent used. Most simple types usually aren't so good at lower frequencies ! Should make a difference in the lower mid ! Maybe slow down the velocity of the rear wave with absorbents ?
But generally speaking I like speakers playing in the open ! Had the luxury of being able to do this for a few years !
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I don't like the sound of most rooms, either - but a good listening room is a joy.
I didn't want to get to technical on this, but yes, it has to do with the back wave. As you and Ashok mention, it is the phase cancellation and wrap around. Get close to the wall and much of the reflected bandwidth will be in phase, thus canceling out. Remove the reflecting wall and there is no cancellation, because no reflection. In between the two you can find a sweet spot. Far enough from the wall to keep much of the reflected sound from being phase cancelled - but still loud enough to flesh out the tonal balance.
An extreme example of this was the troglodyte version of the Manzanitas in my lava cave. Plenty of reflection from behind the speakers, but highly scattered and at distances ranging from about 4 feet to 35 feet.
Manzi set up distances
The Manzi is like any other speaker... it does mater where it is in the room relative to large reflective surfaces. I have always thought the best compromise for most rooms was 36"-48" from a rear wall and up 18" off the floor via support stand. Listening distance 8' or more, slight toe in to the center.
With a relatively small baffle and short wing depth the Manzi's bass balance will change if you are out father from the rear wall... a bit less mid bass and a bit more upper end. Depends of course upon the reflective nature of the wall behind the speaker.
When you get to the much larger Ultra, farther from the wall is better overall if you want to exploit the deep bass potential. With the larger baffle the Ultra's tonal balance is not as distance sensitive.
And of course for either speaker you do get into the area of listener preference.
Both of these speakers are easy to move around and experiment with... all part of the intended fun... learning experience!
John
The Manzi is like any other speaker... it does mater where it is in the room relative to large reflective surfaces. I have always thought the best compromise for most rooms was 36"-48" from a rear wall and up 18" off the floor via support stand. Listening distance 8' or more, slight toe in to the center.
With a relatively small baffle and short wing depth the Manzi's bass balance will change if you are out father from the rear wall... a bit less mid bass and a bit more upper end. Depends of course upon the reflective nature of the wall behind the speaker.
When you get to the much larger Ultra, farther from the wall is better overall if you want to exploit the deep bass potential. With the larger baffle the Ultra's tonal balance is not as distance sensitive.
And of course for either speaker you do get into the area of listener preference.
Both of these speakers are easy to move around and experiment with... all part of the intended fun... learning experience!
John
Another way to explain is room mode excitation. A monopole is a pressure source and excites modes maximally when placed at wall. A dipole is a velocity source and excites modes maximally when placed at the center of the room.
A cardioid is the sum of a monopole and a dipole. It excites modes more alike no matter where you put it.
I'm interested to know whether anyone here finds pressure source speakers physically uncomfortable on their ears as opposed to velocity source. When I first tried OB bass I found it quite a relief on my ears, my room is quite small though 15'*12'*8'. I'm a little surprised no one seems to mention it
finished (for now) Ultras
It took me much longer to finish these than I thought initially. Much of it was my own fault being a novice woodworker (and lacking some tools -had to a fair bit by hand)
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The only baltic birch plywood I found at a reasonable price locally wasn't thick enough (only 3/8ths). I got through Craigslist a free supply of 5/8ths particle board and previously asked on this forum about constrained layer damping eg a sandwich of plywood/tar paper/particle board. Pano gave me the idea of doing a sand filled baffle and after thinking about it for awhile I decided to go ahead...
The baffle has three layers, the front is baltic birch ply, the back is solid particle board with a fake grain laminate/surface, and the middle layer of particle board encloses the perimeter with a hole in the top to pour sand and a ring around each driver cutout (used a router for those). It was tricky getting them all cut to size just using a circular saw and a straight edge. I used a flush trim bit as well. After gluing/clamping the main baffle, I made the wings out of some secondhand oak boards. They are tapered and asymmetrical. They were glued and anchored to the main baffle using screws and right angle braces and the edges chamfered with a router bit.
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I had a tricky time getting a good fit for the top board that conceals the hole for the sand, and eventually settled on using biscuits to line up the edges. I filled it with fine sand (the image shows the hole stuffed with a paper towel to prevent sand dust escaping). I will wait a while and let the sand settle then add more before the final gluing of the top piece. The baffle doesn't resonate at all when I knock it and it is quite heavy. I worry a little about it falling over on a kid. It's stable on the wings unless someone pushes it.
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I assembled the cross-over on a piece of hardboard with the default pad and trap resistors (8 and 15 ohms respectively) with the only modificiation being a 0.1mcf "bypass capacitor" with the 5.6mcf high pass capacitor (C1). I skipped the woofer trap for now but left room on my board in case I want to add it later. I attached the crossover with angle brackets and some thick felt padding.
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I had some small gaps around one of the Vifa drivers where the back plastic flange/bracket on the driver itself wasn't flat against the baffle front. I ended up using a small amount of clear RTV silicone to make a "gasket" of sorts and there seems now to be an airtight seal.
I don't have audiophile ears by any stretch but I am a musician and so far have really enjoyed organ and classical music from these. I'm still fiddling with the exact placement in the room. I'm powering them with a Harmon Kardon AVR for now (I know less than ideal) but it works and was inexpensive secondhand and can deliver 150W plus to each supposedly. The speakers aren't terribly loud but the sound is clean. I can hear the 32 and possibly even the 64 foot organ pedal stops which is new to me from any speakers I've had at home. As expected, they also add considerable sound depth to movies when compared to the built in TV speakers. I've been testing out the "imaging" qualities only a little. I'm not that experienced but certainly can perceive a "soundstage" with some jazz recordings.
I wanted to thank John and Pano first for sharing their design and also answering questions for so many of us. This has been my first speaker project in a long time and has been very rewarding so far. Thanks!
It took me much longer to finish these than I thought initially. Much of it was my own fault being a novice woodworker (and lacking some tools -had to a fair bit by hand)
The only baltic birch plywood I found at a reasonable price locally wasn't thick enough (only 3/8ths). I got through Craigslist a free supply of 5/8ths particle board and previously asked on this forum about constrained layer damping eg a sandwich of plywood/tar paper/particle board. Pano gave me the idea of doing a sand filled baffle and after thinking about it for awhile I decided to go ahead...
The baffle has three layers, the front is baltic birch ply, the back is solid particle board with a fake grain laminate/surface, and the middle layer of particle board encloses the perimeter with a hole in the top to pour sand and a ring around each driver cutout (used a router for those). It was tricky getting them all cut to size just using a circular saw and a straight edge. I used a flush trim bit as well. After gluing/clamping the main baffle, I made the wings out of some secondhand oak boards. They are tapered and asymmetrical. They were glued and anchored to the main baffle using screws and right angle braces and the edges chamfered with a router bit.
I had a tricky time getting a good fit for the top board that conceals the hole for the sand, and eventually settled on using biscuits to line up the edges. I filled it with fine sand (the image shows the hole stuffed with a paper towel to prevent sand dust escaping). I will wait a while and let the sand settle then add more before the final gluing of the top piece. The baffle doesn't resonate at all when I knock it and it is quite heavy. I worry a little about it falling over on a kid. It's stable on the wings unless someone pushes it.
I assembled the cross-over on a piece of hardboard with the default pad and trap resistors (8 and 15 ohms respectively) with the only modificiation being a 0.1mcf "bypass capacitor" with the 5.6mcf high pass capacitor (C1). I skipped the woofer trap for now but left room on my board in case I want to add it later. I attached the crossover with angle brackets and some thick felt padding.
I had some small gaps around one of the Vifa drivers where the back plastic flange/bracket on the driver itself wasn't flat against the baffle front. I ended up using a small amount of clear RTV silicone to make a "gasket" of sorts and there seems now to be an airtight seal.
I don't have audiophile ears by any stretch but I am a musician and so far have really enjoyed organ and classical music from these. I'm still fiddling with the exact placement in the room. I'm powering them with a Harmon Kardon AVR for now (I know less than ideal) but it works and was inexpensive secondhand and can deliver 150W plus to each supposedly. The speakers aren't terribly loud but the sound is clean. I can hear the 32 and possibly even the 64 foot organ pedal stops which is new to me from any speakers I've had at home. As expected, they also add considerable sound depth to movies when compared to the built in TV speakers. I've been testing out the "imaging" qualities only a little. I'm not that experienced but certainly can perceive a "soundstage" with some jazz recordings.
I wanted to thank John and Pano first for sharing their design and also answering questions for so many of us. This has been my first speaker project in a long time and has been very rewarding so far. Thanks!
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Well damn! Not a woodworker, you say? Sure fooled me. And what an ambitious project, doing sand filled baffles. You are a woodworker and speaker builder now. 
Glad to read that your Manzanita build is giving you good music. It is surprising what a such a simple speaker can do, and do well. As you've found, room placement makes a difference. They should sound good placed anywhere, but there will be some placements that are better than others. You'll find the sweet spot.
How is the tonal balance? Is any part of the audio range too prominent or lacking? If so, John and I can probably help with some tweaks to the crossovers.
Bravo on the build. They look nice and the sand filled baffles is a first for this speaker.
Glad to read that your Manzanita build is giving you good music. It is surprising what a such a simple speaker can do, and do well. As you've found, room placement makes a difference. They should sound good placed anywhere, but there will be some placements that are better than others. You'll find the sweet spot.
How is the tonal balance? Is any part of the audio range too prominent or lacking? If so, John and I can probably help with some tweaks to the crossovers.
Bravo on the build. They look nice and the sand filled baffles is a first for this speaker.
The highs and lows seem fine to me. The upper mids are quieter than I'm used to. This is most apparent when listening to choral music (the tenors are there but a little soft). Most of my listening in recent years has been with either built in TV speakers or desktop/computer speakers without much bass so perhaps the midrange just seems quiet in comparison now that I'm getting a whole lot more from the low end. Anyone have any suggestion for doing frequency response testing/SPL measurements without buying expensive software and calibrated mics etc?
Thanks for the info. The Manzanita usually has a slightly recessed midrange, which gives it some space. If you are used to speakers with nothing but midrange, it's certainly going to sound different!
Measuring speakers inside a room is never easy. But you can do some decent measurements with your phone. I have a number of audio measurement apps on my iPhone and they are very handy. Parts Express even sells a little calibrated mic for the phone that works well - and is easy to lose.
Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android
Measuring speakers inside a room is never easy. But you can do some decent measurements with your phone. I have a number of audio measurement apps on my iPhone and they are very handy. Parts Express even sells a little calibrated mic for the phone that works well - and is easy to lose.
Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android
Ultra plans
The drawing for the Ultras is on this link (towards the bottom of the page). The drawing is fine but the crossover on the link is very old and outdated.
The best affordable DIY open baffle loudspeaker I've listened to so far.
The newer version of the crossover and the bill of materials is here.
http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project-86.html#post3438681
There are additional upgrades like the extra trap on the woofer and using the tiny bypass caps. Those are scattered through this (very long) thread.
Hope this helps.
Barry
The drawing for the Ultras is on this link (towards the bottom of the page). The drawing is fine but the crossover on the link is very old and outdated.
The best affordable DIY open baffle loudspeaker I've listened to so far.
The newer version of the crossover and the bill of materials is here.
http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project-86.html#post3438681
There are additional upgrades like the extra trap on the woofer and using the tiny bypass caps. Those are scattered through this (very long) thread.
Hope this helps.
Barry