[Bob in St. Louis]

"Room Treatments"

If you pick the perfect girl to begin with, you won't have to worry about fixing her shortcomings later.

It just makes things easier to do it right the first time. And yes.... I did it backwards.

Bob

[twitch54]

"Room Treatments"

I totaly agree with Bob, EQ, while it can be beneficial is a final tweak when and where needed.

[JRace]

Your poll asks one question,
what to do First

But it sounds tonme like your really asking
If you could only do one, which would it be

Yes eq is cheaper and easier, and yes eq in the bass is very acceptable.
However if you first eq, then add room treatements then you will need to redo your eq, then your room tretamens may need adjustemnets, then you have to re-eq again.
Instead do the room treatments then eq after for best results.

[JohnR]

If only one chair, if you only want to address frequency (not time) and if you only want to address peaks and not modal nulls, sure.

Bryan, did you ever get those plots that demonstrate how "room treatment" removes nulls? I don't recall seeing you post them.

Thanks

[JLM]

"Room Treatments"

If you pick the perfect girl to begin with, you won't have to worry about fixing her shortcomings later.

It just makes things easier to do it right the first time. And yes.... I did it backwards.

Bob

Room/system or the girl?   

[medium jim]

Your poll asks one question,
what to do First

But it sounds tonme like your really asking
If you could only do one, which would it be

Yes eq is cheaper and easier, and yes eq in the bass is very acceptable.
However if you first eq, then add room treatements then you will need to redo your eq, then your room tretamens may need adjustemnets, then you have to re-eq again.
Instead do the room treatments then eq after for best results.

No, the thinking was to do what is required, but what comes first and why?

Jim

[JRace]

Well if your planning to do both, then you must do room first.

If you do eq first then treatments you will need to re-eq. So why even eq in the first place?
Its not like you will negate any need for room treatments just because you have eq'd.
However once you have done treatments the amount of eq needed will be must less, and you will have addresses issus that you just cannot with eq. And you will need less electronic correction and reduce the amount of problems that can arise from using eq.

[Bob in St. Louis]

Room/system or the girl?   

The room. 

[*Scotty*]

For those still unfamiliar with the CABS approach to bass response optimization. Real world testing shows that one can achieve a minimally non-resonant condition below the rooms Schroeder frequency with four woofers and digital delay. The published experimental data substantiates that in square to rectangular rooms non-resonant behavior of the room below the Schroeder frequency and the resulting flat response can be obtained without the use of equalization or room treatments.
 In many instances rooms that were formerly considered problematic to terrible because of their dimensional ratios are in fact, the very rooms that will give the best results with CABS. This makes a very strong case for trying this technique first. Financial resources that could have been committed purchasing room treatments or equalization, might be better spent or saved up, until enough money is accrued to buy another sub or subs. Depending on the rooms dimensional ratios, even the use of only two subs with delay could perhaps give you sixty to seventy percent of the results possible from the use of the full monty.
Scotty
http://vbn.aau.dk/files/12831869/AC-phd.pdf
 

[JohnR]

*Scotty*, I'm having some trouble understanding something and hoping you can shed some light. For example, consider Figure 11:



At the rear of the room, I would have thought that the SPL there would be zero (roughly). The rear subwoofers are out of phase with the signal arriving from the front subwoofers, thus cancelling them at the rear wall. They would therefore be creating a null at the rear wall. So why is the SPL not zero at the rear wall?

On the other hand, if the rear subwoofers are acting to "remove the rear wall" then you would expect SPL levels to simply drop off gradually from the front to rear wall and still have significant levels at the rear wall. As the graphs show.

Any thoughts on this - what am I missing? What are you measuring at the rear wall?

[bpape]

Bryan, did you ever get those plots that demonstrate how "room treatment" removes nulls? I don't recall seeing you post them.

Thanks

Been swamped lately. I'll look for a good example where it's very clear. We have several sets where it's happening but can be clouded by other things happening. 

Bryan

[*Scotty*]

Hi John, the graphics show the pressure distribution in the room with the rear sub-woofer delay set to generate a counter wave 180 degrees out of phase with the front planer wavefront at a time just before the wave from the front reaches the cones of the subs on the rear wall. The pressure in the room is constant virtually everywhere in the room. The delay added to the rear subs output is at the heart of CABS and what makes flat bass response at more than just one point in the room possible.
 
If no delay was used, the two planer wavefronts would meet in the middle of room 180 degrees out of phase and the amount pressure/bass would start to decrease as you approached the rear wall of the room until the position of peak nullification was reached at the subwoofers locations on the rear wall.
 I have experienced the second condition in the listening room of my friend, Rick Reimer, 7 years ago. His room measured 12ft.x8ft.x26ft. with a concrete slab floor and cinder block walls. The speakers at the front of room were the same as mine, Reimer Speakers TETON GS, which has an WMTMW design. There was a single 12in. sub-woofer operating 180 degrees out of phase located on the floor in the center of wall at the rear of the room.
The listening position was 12 feet away from the front wall and about 2ft. ahead of point of the onset of cancellation. As you walked toward the rear wall the bass progressively decreased until at the location immediately in front of the woofer the bass was at zero.
The woofer at the rear of the room was operated at level far lower than the volume of the speakers at the front and you could not tell it was even on until you were right on top of it. As long as the listening position is forward of the point where the onset of cancellation occurs you get to hear the full bass SPL properly integrated with the rest of the music spectrum and with zero room resonance in the bass frequencies.
 Obviously my friend had the nearly perfect room dimensional ratios necessary to pull off this trick with only one out of phase woofer at the rear of the room. He was also the designer and builder of the main speakers as well as the sub-woofer which duplicated the bass alignment and extension of the speakers in the front of the room. The sub was effectively one half of the one of main loudspeakers as far as the bass output was concerned.
Scotty