..... at least for me. Not a TL this time.
(Trivia question : What TV show did that line come from? You will show your age with the answer.)
Thought I would share my latest project, my son and I wired it up last weekend and it has been tweaked several times during the past few days.
http://www.quarter-wave.com/OB_Wings_Back.jpg
http://www.quarter-wave.com/OB_Wings_Out.jpg
This is an OB system (48" tall x 60" wide with the wings out) using either the Lowther PM2C, PM2A, or DX4 driver and two Dayton 15" high efficiency woofers (JBL 2226 clones) per side. I am using a DBX DriveRack PA digital crossover, the woofers roll off at 120 Hz 12 dB/octave and the Lowthers roll in at 120 Hz 24 dB/octave, and two Rotel RB-1080 200 watt amps.
All solid state and no passive BSC filter required. My calculations indicate the efficiency is about 98 dB/w/m and reasonably flat above 50 Hz. Decent bass into the 30 Hz range but no measurements yet to prove any of these numbers.
This is a very efficient system and even at fairly loud volumes the drivers barely move, you have to touch them to convince yourself they are connected. Great dynamics and bass. Best reproduction of a kick drum that I have heard from any of my own speaker designs, they can move a lot of air. Very similar sound to my Lowther ML TL design but with better bottom end, no big surprise I guess.
More details to come on my web site when I am done tweaking and find time to documented the project,
(Trivia question : What TV show did that line come from? You will show your age with the answer.)
Thought I would share my latest project, my son and I wired it up last weekend and it has been tweaked several times during the past few days.
http://www.quarter-wave.com/OB_Wings_Back.jpg
http://www.quarter-wave.com/OB_Wings_Out.jpg
This is an OB system (48" tall x 60" wide with the wings out) using either the Lowther PM2C, PM2A, or DX4 driver and two Dayton 15" high efficiency woofers (JBL 2226 clones) per side. I am using a DBX DriveRack PA digital crossover, the woofers roll off at 120 Hz 12 dB/octave and the Lowthers roll in at 120 Hz 24 dB/octave, and two Rotel RB-1080 200 watt amps.
All solid state and no passive BSC filter required. My calculations indicate the efficiency is about 98 dB/w/m and reasonably flat above 50 Hz. Decent bass into the 30 Hz range but no measurements yet to prove any of these numbers.
This is a very efficient system and even at fairly loud volumes the drivers barely move, you have to touch them to convince yourself they are connected. Great dynamics and bass. Best reproduction of a kick drum that I have heard from any of my own speaker designs, they can move a lot of air. Very similar sound to my Lowther ML TL design but with better bottom end, no big surprise I guess.
More details to come on my web site when I am done tweaking and find time to documented the project,
I have not given up on TLs but I don't want to be totally one dimensional. I wrote an OB worksheet and just wanted to try it out, easy and quick project with drivers I had lying around. My wife hates them so I am not sure how long they will be allowed in the house.
Uploaded some less compressed pictures, hope they look a little better.
MJK,
the pictures don´t show as much OB as their title promised. What about the "open boxes" behind the drivers? Was that what you meant by "OB"?
Nevertheless ... it´s good to see another expert of loudspeaker theory engaging in dipoles. There still is´nt an exhaustive tool for OB design under room conditions
Rudolf
the pictures don´t show as much OB as their title promised. What about the "open boxes" behind the drivers? Was that what you meant by "OB"?
Nevertheless ... it´s good to see another expert of loudspeaker theory engaging in dipoles. There still is´nt an exhaustive tool for OB design under room conditions
Rudolf
Are those high Qts drivers or you are using active EQ? JBL2226 won't work in OB, but I suppose those Dayton are high Qts drivers.
I've been planning a similar project for a quite some time, but using two 15 inch 4 ohm car drivers per channel. Monacor has very nice 0,9-1,2 Qts, high power and long excurtion 12 and 15 inch car drivers.
Is your open baffle calculator avaiable for free?
Great project!!!
Bartek
Cal gets the correct answer, vintage 1970's English humor which I watched regularly in college ..... usually with a beer or two.
The front baffle is 48" tall by 24" wide. There are "sides" that extend 12" back and a pair of braces at the top and bottom to stuffen the structure. Then there are 18" wide wings mounted on hinges that can swing out to make the total front 60" wide. The assembly is open along the back and at the top, is that something other then an OB design? Maybe I am missing something or using a definition incorrectly.
The Dayton drivers have the same T/S parameters as the JBL 2226 drivers, these are low Qts drivers. This is why I am using two in parallel, I get the SPL up at low frequencies using two drivers and a boost and then roll them off with the crossover. I like low Qts drivers and there is no EQ other then the volume boost.
It will be one of my new worksheets planned for release starting in March, unfortunately the new worksheets will not be free. The OB worksheet takes into account the driver positions on the baffle, the crossover and boost, the baffle geometry, and the floor reflections.
The back is completely open with the exception of two narrow (I think 4" wide) pieces at the very top and bottom to provide some reinforcement and square things up a little. I also have a small shelf at the very top to provide some protection to the back of the Lowther cone and allow me the option of adding a suoer-tweeter later if I desire.
MJK,MJK said:
sorry if I´m a bit inquisitive about that: Are those 12" sides running all the way from top to bottom or am I just interpreting the pictures wrongly?
If they are real sides, do you account for any TML effects that may occur between them?
It´s certainly my fault if I equated OB with flat front face and flat back face. Thought my smilie (
) did care for that.Your interpretation is correct.
No I have not, I am not sure that a standing wave is possible in this type of geometry. Can you describe where a standing wave might exist? I have seen this mentioned before but have not understood how it can occur.
No blame required, nothing is your fault. I understand that some people like a more rigid definition and a flat baffle is clearly an OB in everybody's book. I guess things get a little fizzy when you move away from one particular geometry and try to apply tightly defined naming conventions.
Yes, Monty Python's Flying Circus, My father in law bought the whole collection. Man, did I marry into the right family.
I just built a pair of OB's using Visaton B200. With only 50 hrs on them , well lets just say it's a revalation.
My baffles are 11" center with fixed wings of 7" and 9". Both at 60 degrees. 48" tall with about a 10 degree tilt back.
If you get a chance you may want to try the OB experiment again with higher Qts drivers like the B200
Chris
I just built a pair of OB's using Visaton B200. With only 50 hrs on them , well lets just say it's a revalation.
My baffles are 11" center with fixed wings of 7" and 9". Both at 60 degrees. 48" tall with about a 10 degree tilt back.
If you get a chance you may want to try the OB experiment again with higher Qts drivers like the B200
Chris
bzdang said:
Thanks, that's an excellentr target date for my new HT setup. I should understand how to program and record with the Panasonic ES20 recorder by then also,lol.
On topic; MJK's OB efforts look exceedingly good. That OB sound is hard to get away from. Maybe I should look into an OB mains for the HT setup? What would one do to match the side and rear speakers in a 5.1 or 6.1 setup? I wouldn't want to destroy the OB image with a poor implementation of the satelites.
MJK said:
May be "standing wave" is not the proper name. With "TML effects" I meant a lambda/4 resonance. Let me explain:
You´ve got the "sides" at the back of your OB and the floor as a third side.
That forms an open box, albeit with a missing fourth side at the top. Doesn´t that work like a U baffle with a lambda/4 resonance to the open back of the "box"?
I remember increasing "boxiness" with my winged open baffles, when I folded the wings back until the angle between them became less than 60°.
Attachments
I'm just parroting what I've read, but the Qts of the driver in OB is kind of like the Qtc of a closed box. .707 would be criticly dampended. The highed the Qts the fatter the bottem end.
Two good threads:
http://www.audiocircle.com/circles/...&postorder=asc&highlight=visaton+b200&start=0
http://fullrangedriver.com/forum/viewtopic.php?id=336
Johnincr seem to have a couple of years of hand on experance with ob design.
Chris
Two good threads:
http://www.audiocircle.com/circles/...&postorder=asc&highlight=visaton+b200&start=0
http://fullrangedriver.com/forum/viewtopic.php?id=336
Johnincr seem to have a couple of years of hand on experance with ob design.
Chris
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