AudioCircle
Audio/Video Gear and Systems => Open Baffle Speakers => Topic started by: Gothover on 28 Apr 2012, 09:17 pm
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Here is my "Yeild" Open-Baffle.
I used a bandpass port design, however retuned the cavity for better bass response, I also made the cavity adjustable for use with different 15 inch drivers.
I went with a 2-way active design, using the Audio Nirvana 10 for the HF section.
I stuck with the Eminence 15A's for now, they sound great in this configuration, very natural.
I am also sticking with the Mini DSP, sounds great, very quiet, and direcly imports R.E.W. (nice feature)
Dave
(http://mysite.verizon.net/res12il11/sitebuildercontent/sitebuilderpictures/.pond/DSCF5737.JPG.w300h400.jpg)
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Front and Side
(http://mysite.verizon.net/res12il11/sitebuildercontent/sitebuilderpictures/.pond/DSCF5746.JPG.w560h747.jpg)
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Rear
(http://mysite.verizon.net/res12il11/sitebuildercontent/sitebuilderpictures/.pond/DSCF5743.JPG.w560h747.jpg)
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I am building another set, that I intend to finish in dark walnut. I will post some pics when they are ready.
I wasn't sure I was going to like open baffle designs, but they are incredibly addicting. In fact, I went to a freinds house today, and listened to his high $$$$$$ Ambiance Ref 16's, and thought the bass was boomy and overdone. Probably because the bass section is a ported design, and I am getting used to the planar type bass once again.
Dave
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Interesting project.
Where are you crossing them/what slope?
How did you determine the front chamber vol. for the Eminence woofers?
How low does this extend the bass from them?
Thanks,
John
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Hi John, I am crossing them at 200hz
18db LF rollof and 6db HF.
My design allows me to add spacers to increase chamber volume.
Dave
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How low does this extend the bass from them?
http://www.quarter-wave.com/OBs/U_and_H_Frames.pdf
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.
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Nice :thumb:
So the woofers are actually on the back of a chamber, with ports directly opposite? I wasn't aware of that.
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If you put EAR SD40AL constrained layer damping material on the woofer frames and also magnet brace both woofs and also brace the baffle with the same brace you will get much, much better bass. I cannot seem to figure out how to make a picture appear here so I will try and load it to my Gallery. The last pic in the gallery shows an alpha 15 in an h-frame with EAR damping material applied and also the magnet is epoxied to a piece of 13 ply plywood which is bolted to 26 ply plywood brace. You can use just one brace for both magnets and curve it around so it also braces the baffle between the woofs and full range. Way better sound! The Gallery also shows an open baffle speaker that also has both Alphas damped/magnet braced and the baffle braced....very crude version.
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Nice :thumb:
So the woofers are actually on the back of a chamber, with ports directly opposite? I wasn't aware of that.
Yes, I did that for several reasons, primarily for tuning and being able to service the drivers without dissassembling the entire speaker.
Dave
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If you put EAR SD40AL constrained layer damping material on the woofer frames and also magnet brace both woofs and also brace the baffle with the same brace you will get much, much better bass. I cannot seem to figure out how to make a picture appear here so I will try and load it to my Gallery. The last pic in the gallery shows an alpha 15 in an h-frame with EAR damping material applied and also the magnet is epoxied to a piece of 13 ply plywood which is bolted to 26 ply plywood brace. You can use just one brace for both magnets and curve it around so it also braces the baffle between the woofs and full range. Way better sound! The Gallery also shows an open baffle speaker that also has both Alphas damped/magnet braced and the baffle braced....very crude version.
Rick, the EAR is great dampening material, and I agree the rear brace does work great. I decided to research this due to your suggestions, and found that you were absoluely correct, the basket of the Alpha 15A does infact generate its own audible artifacts.
This was easy enought to prove using a stethoscope, or just touch the driver while its playing at moderate levels.
I spent several hours using a magnetic accelerometer and an EVA to measure the baskets vibration, the I switched from the EVA to my osciliscope because I needed greater sensitivity. What I found is most of the vibration is caused by the "for lack of better words" oil canning that occurs at the large flat open area the magnet attaches to, and not the beams.
What I did to correct this was cut 1.5" thick 8"diameter MDF doughnuts to be epoxied to the oil canning area, then I used Max MCR black to fill and permenently attach the doughnuts to the magnet structure, and took measurements again. What I found was the doughnuts were nearly as good as the rear brace I tried, and simple to build.
Dave
(http://mysite.verizon.net/res12il11/sitebuildercontent/sitebuilderpictures/IMG_0705.JPG)
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Glad you are experimenting. I would not trust measurements. When I first damped the woofs it was just with the EAR material. Huge improvement. Then we added the first brace in the crude jobbie and then the second brace. Each time a huge increase in sound quality. We did not remove the damping material after adding the braces but I still think the baskets would still ring if you do not use the EAR as well. The only way to know if it would make more difference is to apply it and listen. Using a measurement tool only gives you so much info. Your ears are infinitely better in picking up nuances. However, not bracing the baffle is a mistake. It has to be seriously rigid. A more massive, heavy, constrained layer damped and larger base would also help. The more damped weight the better. A little piece of plexiglass is not a serious base. Of course, you need serious feet as well. The more massive, dead and rigid the baffle and drivers are the more the sound accelerates with speed and low distortion (super transparency!!!). You should only be hearing the cones vibrate....not anything else. Your dognuts....he he....are very cool. Good idea. However, I would not trust they are as good as magnet bracing.
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Thanks for your input Rick , I certainly agree, the dampening material will definately not hurt anything. I think these baffles are fairly rigid, as they are 5" thick mdf green glued and weigh in in empty at 53 lbs each. The Base is 9/16" plexiglass with 2"floor spikes.
I still like the idea of the rear brace, it's just gets a bit tricky to build, and everything is a tradeoff. I left the wiring exposed so I always have the option of wiring straight to the amp as well, and the binding posts can be used to hold wire hangers.
Thanks for all the input, certainly appreciated.
Dave
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HI Dave ,great work!
the front load look like a sort of Nelson Pass slot load ?
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Dave,
If you just want to brace the baffle then you can run trianguated braces up each side. Google the Granada G2 speaker. You could run a similar brace on each side but not all the way up.....just to below the full range. This would be plenty of brace and the full range would not have any cavity resonance to deal with if you ran it all the way up. A heavier base with the braces would add more weight and the combo would be really rock!!! and at the same time not rock. You don't want the speaker to move....just the cones. 5 inches thick......with Green glue.....yikes! This is good!
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Dave,
If you just want to brace the baffle then you can run trianguated braces up each side. Google the Granada G2 speaker. You could run a similar brace on each side but not all the way up.....just to below the full range. This would be plenty of brace and the full range would not have any cavity resonance to deal with if you ran it all the way up. A heavier base with the braces would add more weight and the combo would be really rock!!! and at the same time not rock. You don't want the speaker to move....just the cones. 5 inches thick......with Green glue.....yikes! This is good!
That brace I like alot, simple, and effective.
Dave
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Hi,
Can someone please explain the science behind this design? I'm familiar with the concept of multi-volume chambers used with a single port (single reflex bandpass); just not sure what the design objective was here and how it was achieved?
Thanks much!
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Here is a link to the discussion that got me interested in the CS2.3 clone, that led me to this build.
http://www.diyaudio.com/forums/multi-way/148303-emerald-physics-3.html
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Thanks. I remember following that thread when it first came out, but the take-away seemed to be inconclusive. There were some heavy hitters contributing like Martin King and Earl Geddes, but neither seemed to add credibility to the concept. You commented on your ability to add spacers to tune the port. In your development, have you measured this against the same drivers mounted traditionally on a flat baffle or shallow u-frame? Thanks.
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The band pass baffles signifigantly rolled of the hf, as expected, but but gained spl at lower frequencies, this gain and loading gave me the bass I was looking for, and required very little EQ.
As Gedde's noted in the thread, this design has alot in common with a conventional vented monopole subwoofer. I consider it a hybrid.
Dave
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L.B.A.T. "Loaded Baffle Acoustic Transducer"
Dipole or Monopole?
Using the Eminence 15A as a reference:
The Eminence driver requires a sealed box at 5.3cuft to have an F3 of 47hz,
and a ported enclosure of 88cuft to have an F3 of 22hz, which tells me there
is definately more to this design, than a simply referring to is a conventional
monopole bass generator.
The bandpass open baffle is basically a loaded open baffle design, similar to the
loading of a horn driver but without the flair.
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Can someone please explain the science behind this design?
Think of it as the front chamber of a ripole. The added airload in front of the cone will increase Mms, thereby reducing Fs and raising Qts. You will get a "hump" in the response curve around (the lowered) Fs. While this can be desirable, you will lose efficiency - massively. Since there is no rear chamber, the construction will tend towards a cardioid radiation pattern.
Added to that the front chamber will act as a Helmholtz resonator which can be tuned to some frequency. This will superimpose the above effect.
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Think of it as the front chamber of a ripole. The added airload in front of the cone will increase Mms, thereby reducing Fs and raising Qts. You will get a "hump" in the response curve around (the lowered) Fs. While this can be desirable, you will lose efficiency - massively. Since there is no rear chamber, the construction will tend towards a cardioid radiation pattern.
Added to that the front chamber will act as a Helmholtz resonator which can be tuned to some frequency. This will superimpose the above effect.
Thanks for the additional insight, it would certainly be nice to be able run sims on the LBAT design, rather than have to build and test, then modify and retest etc. Then again, I only learn the hard way.
Dave
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love it.
what is the volume of the front chamber?
are the two woofers both sharing the front chamber or is there and internal panel separating two smaller chambers?
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love it.
what is the volume of the front chamber?
are the two woofers both sharing the front chamber or is there and internal panel separating two smaller chambers?
The woofers have independant chambers. I don't remember the chamber size, I would have to look at my notes.
Dave
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The Loaded Baffle Acoustic Transducer.
The L.B.A.T. has an orfice in the front and open baffle to the rear.
As the woofer attempts to move forward, the port creates a high pressure area which causes the wave to compress.
When the woofer changes direction , rarefaction occurs.
Dave Harris
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Air waves are not air jets. Above picture shows a rather static and naive understanding of sound waves. You don't want to move air through your room, but to move waves through the air. Any "acceleration" of a wave through air would result in a change of frequency. It is called "doppler effect". I don't think that such an effect is intended here.
Rudolf
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Thank you Rudolf.
This crued drawing was merely and attempt to visually understand what is physically
taking place in the bass chamber.
Dave
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Dave,
Very interesting speaker.
Interesting enough for me to get sucked into modifying a MathCad worksheet to simulate the geometry to try and understand how it works. After a couple of hours I found that the port adds a sharp Helmholtz resonance in the 100 to 300 Hz range, depending on the cavity dimensions, where the crossover is being made. It was tough to get a smooth transition between the woofer and the full range driver in my model, some pretty severe wiggles were generated.
I have not modeled your eact configuration, it could be done with some more effort, but I do not see much of an advantage of this concept over a basic U frame. Definitely a more challanging design and your speaker looks great. Not sure I am ready to make the extra effort.
Martin
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Delete
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Dave,
Very interesting speaker.
Interesting enough for me to get sucked into modifying a MathCad worksheet to simulate the geometry to try and understand how it works. After a couple of hours I found that the port adds a sharp Helmholtz resonance in the 100 to 300 Hz range, depending on the cavity dimensions, where the crossover is being made. It was tough to get a smooth transition between the woofer and the full range driver in my model, some pretty severe wiggles were generated.
I have not modeled your eact configuration, it could be done with some more effort, but I do not see much of an advantage of this concept over a basic U frame. Definitely a more challanging design and your speaker looks great. Not sure I am ready to make the extra effort.
Martin
Martin, thank you for your input.
This design may or may not have any advantages over a basic U frame, I have never ever heard one so cant even form an opinion about it.
I appreciate that you took the time to look over the design, your input is always welcome.
Dave
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Nice work Dave.
I'm interested in your impression of the AN drivers response mounted as you have it .. (U frame basically)
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I really could not be happier with the Audio Nirvana 10, it sounds very natural.
This driver works far better o-b than it ever did in a sealed or ported enclosure.
Dave
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So the shrouding at the rear is of no consequence? Good to know.
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So the shrouding at the rear is of no consequence? Good to know.
The deep shroud actually made the drivers sound quite a bit smoother at higher levels. My original design only had 2 layers of mdf, the newest version has 6 layers.
When I built the prototypes I simply added rings to the rear until I got the sound I was looking for, each ring changed the sound and in-room response just a little bit.
Dave
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Do you have a way to measure the AN driver? I expect it to have ragged, peaky response up high.
Greg
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Do you have a way to measure the AN driver? I expect it to have ragged, peaky response up high.
Greg
What kind of measurements are you looking for? I posted some FR measeurments earlier in this thread.
Dave
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Sorry, I guess I didn't post it.
I have and in room plot without EQ, the AN is running crossed at 200hz 1st order.
http://mysite.verizon.net/res12il11/sitebuildercontent/sitebuilderpictures/IMG_0692.JPG
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The deep shroud actually made the drivers sound quite a bit smoother at higher levels. My original design only had 2 layers of mdf, the newest version has 6 layers.
When I built the prototypes I simply added rings to the rear until I got the sound I was looking for, each ring changed the sound and in-room response just a little bit.
Dave
Of course. I've noticed this with a U frame build working here (woofer). From a design standpoint my mid range would need a degree of shrouding as well. I'll have to check this as well. Thanks.
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Yesterday I built passive crosssovers as an option for the Yield, and have to say sounds damn near as good as the active network. The active network obviously has the advantage of room correction and time alignment but the passive has a few advantages of its own, like analog domain, and a single amplifier to drive them.
Yeild build Video http://www.youtube.com/watch?v=TXgLNbAdDTg&feature=youtu.be
(http://forums.klipsch.com/forums/storage/4/1747678/IMG_0777.JPG)
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Here is a comparison graph between the active and passive networks, the passive is in green.
This was just a quick measurment taken with my Ipod, notice the lf response appears to be nonexistant due the the mic.
(http://forums.klipsch.com/forums/storage/4/1747676/IMG_0776.jpg)
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This was just a quick measurment taken with my Ipod
Looks great !
(I must check how this measurement is done with an iPod)
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You could use active on the woofs and a simple cap on the fullrange.....if you hardwire your speaker wire to the cap and the cap directly to the driver you will get much better sound than using any connector. All speaker wire hardware ruins the sound. Hardwire.....please....you will love it. Please bypass the large value film caps with a great sounding .1 to .33uf. Make sure you orient the outside foil of all the caps toward the driver.
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Been so busy lately, I have not had alot of time to work on my projects.
Recently I finished a set of Yields for a customer, and I have 2 more sets going out for demo. One pair is scheduled to make an appearance at AK-Fest, I hope that works out.
(http://forums.klipsch.com/forums/storage/4/1754794/DSCF5798.JPG)
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New crossovers, I still need to get the labeling done.
(http://forums.klipsch.com/forums/storage/4/1793812/DSCF5834.JPG)
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Inside
(http://forums.klipsch.com/forums/storage/4/1793811/DSCF5836.JPG)
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This latest set of Yields are currently out for paint.
(http://forums.klipsch.com/forums/storage/4/1793809/IMG_0922.JPG)
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Well I picked up the Yield cabs from paint shop today, and they did a horrible job.
Guess I will have to find a better painter.
(http://forums.klipsch.com/forums/storage/4/1804144/IMG_0960.JPG)