They are pretty stiff, so I would think a frame is not even needed. I think each panel is 3/4" thick of so. I could just stack them and wrap them in burlap.
yes, wrap them, I just always know they can be still a little brittle and I move mine a lot so a wood frame helps. >= 2" OC703 will capture 100% of the reflection from the speaker > 500Hz so there are then no issues with in room measurements, Easy to gate down to 500Hz!!
No reason to move things outside if you can remove the reflections
Sorry i was not aware he had an anechoic chamber ......
Are you saying 4" OC703 placed poperly to absorb reflections will not do that??
If there are no 1st refections, there is no worries about Gating out to even > 8ms which gives us a clear picture even down below 500Hz.
No reason to waste time moving things outside when science dictates we can do a great job inside!!
Hi Loren, for the off axis measurements it is better to turn the speaker rather than move the mic Ideally a rotating platter under the speaker (something I am yet to get). You also want the arc that the speaker turns through to have it's centre in line with the front of the baffle (down its centre line) not the centre of the speaker cabinet.
Since you have a tiled floor, get some blankets rugs or quilts etc and put them on the floor between the speaker and mic.
You can also try moving around the room a bit, try to not be exactly parallel to the walls. You may be able to take advantage of the door ways if you can open the doors and arrange the speaker and mic so that the direct reflections off the walls (to the mic) go out the doors. It may help but I suspect your floor / ceiling reflections will be the earliest. The best I get in room is down to about 300Hz.
Tony.
Ideally a rotating platter under the speaker (something I am yet to get). You also want the arc that the speaker turns through to have it's centre in line with the front of the baffle (down its centre line) not the centre of the speaker cabinet. Since you have a tiled floor, get some blankets rugs or quilts etc and put them on the floor between the speaker and mic.
You can also try moving around the room a bit, try to not be exactly parallel to the walls. You may be able to take advantage of the door ways if you can open the doors and arrange the speaker and mic so that the direct reflections off the walls (to the mic) go out the doors. It may help
but I suspect your floor / ceiling reflections will be the earliest. The best I get in room is down to about 300Hz. Tony.
Not sure, Have you done such and then taken it outside and compared ...? Is it the same ..?
regards,
Hi Loren, for the off axis measurements it is better to turn the speaker rather than move the mic
Since you have a tiled floor, get some blankets rugs or quilts etc and put them on the floor between the speaker and mic.
You can also try moving around the room a bit, try to not be exactly parallel to the walls. You may be able to take advantage of the door ways if you can open the doors and arrange the speaker and mic so that the direct reflections off the walls (to the mic) go out the doors. It may help
Tony.
Thanks!
I was debating either rotating the speaker or moving the mic. I have always moved the mic and faced the speaker oblique to the walls. Unfortunately, the room is a bit cramped with furniture and the center island in the kitchen.
I'll try the acoustic panels and rotate the speaker instead of the mic as you suggested. I'll also elevate the speaker a bit to get it off the floor.
I must say that I really like the sound of these ribbons. They have such a wide sweet spot compared to the Morel domes I had on the 3-way configuration and the sound is very clean.
Also, the new cabinets, being smaller at 5 cubic feet, seem to have much better bass than the 6 cubic foot cabinets I had.
The preamp just got a new set of tubes, too.
Its pretty easy to see where a room interacts in the impulse, also maybe you are not aware of the OC703 absorption rate. If we have properly paced panels there is NO reflection that will impact the measurement, its that simple. Comparisons are just a waste of time at that point but to answer your question, yes the comparisons have been done.
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I use this Shepherd Hardware 9548 6 Inch Lazy Sus Turntable
Just screw wood to it. Mark your zero axis, 15, 30, 45, 60, etc on it. Place the speaker center and rotate for horizontal measurements.
I picked up 16 5/8" thick 2' by 4' fiber glass ceiling tiles. I'll use these for the absorption panels after I peel the plastic off the one side.
I have some questions on technique:
1) Do you lay these panels on the floor (3 to 4" thick) in front of and beside the speaker?
Or, do you stand these panels up vertically beside the speaker? What is the best way to do that?
2) When you begin a sweep with Holm, what starting frequency should I use?
Right now I use 10 Hz, but I think that may be one of the reasons the gate time is so high. Low frequencies really are hard to trap and they wrap around everything. Will the low frequencies cause Holm to set the gate time higher?
I should try sweeping at a start frequency of 400 Hz to see if the gate time changes.
Hmmm.
I'm aware of what an OC703 panel will do, but i have never used holm but do have LMS/Leap and DRA labs MLSAA and i believe the physics are the same....
Many moons ago spent a lot of time doing gated, groundplane and anechoic measurements, so I'm aware of how each is different and was never able to get accurate gated responses indoor below 800 hz and this is with panels and the speaker 16ft from it's nearest reflection path in a pretty big room.
Interesting that you can do so now with your current setup and see no difference with ground plane measurements ( which is pretty good way to measure IMO), hence my questions as it never worked for me below 800 hz..
I guess if he was to cover every wall with OC703, 400 hz maybe possible again i would suggest dragging the thing outside and do the measurements ground plane and save the OC703 money .....
just saying ....
Doug20,
The problem and or the downside of time-windowed measurement is that there is a built in restriction in frequency resolution, making indoor domestic measurements a problem.
Now if the maximum time window that can be achieved, from the beginning of the speaker's response to the arrival of the first reflection, is 6 milliseconds (6ms, or 0.006s—a typical figure in a domestic room), then the frequency resolution of the resulting measurement will be 1/0.006 = 167Hz. This makes accurate measurements at bass and lower-midrange frequencies impossible to achieve IMO well without resorting to subterfuge....
Groundplane measurements away from your house has no such restrictions , just make sure you are at least 20ft from the house facing away ....
Regards,
The problem and or the downside of time-windowed measurement is that there is a built in restriction in frequency resolution, making indoor domestic measurements a problem.
Now if the maximum time window that can be achieved, from the beginning of the speaker's response to the arrival of the first reflection, is 6 milliseconds (6ms, or 0.006s—a typical figure in a domestic room), then the frequency resolution of the resulting measurement will be 1/0.006 = 167Hz. This makes accurate measurements at bass and lower-midrange frequencies impossible to achieve IMO well without resorting to subterfuge....
Groundplane measurements away from your house has no such restrictions , just make sure you are at least 20ft from the house facing away ....
Regards,
I would not expect ground plane to work very well in Saint Augustine lawn.
My drive way is almost 20 feet wide, but it comes up to the side of the house and the garage is a side entrance to the right.
So, getting the speaker 20 feet away from anything (trees, fences, building) is going to be a problem.
Okay. I'll try it at the end of the driveway and I have a pair of 2' by 8' sheets of plywood that I could lay down in front of the speaker.
Would that work for a ground plane test?
Also, I think I want to angle the speaker forward, right?
Correct, upside down with tweeter tilted and pointed over towards the mic ..or on it's side tilted over towards the mic ..
you can also sit on a bench typically 4 ft high and do gated measurements
( mic usually 7-9 ft off the ground, speaker dependent ) outside if you want for comparison sake this will net you better accuracy than the indoor measurements ...but GP is still better ...
regards,
you can also sit on a bench typically 4 ft high and do gated measurements
( mic usually 7-9 ft off the ground, speaker dependent ) outside if you want for comparison sake this will net you better accuracy than the indoor measurements ...but GP is still better ...
regards,
6ms measurements are easily completed if the setup is done properly. No arguement with doing things outside but its not that easy for some people. Easpecially those unfortunate to live in areas with nasty weather.
He can choose the best solution but you can not say he can not get accurate measurements for XO design. < 200Hz is meaningless anyways since the room dominates those frequencies anyone thinking they are doing anything special that low from outside are just fooling themselves! You and I disagree already on in-room EQing so no need to discuss that topic (other then Im right)
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