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Learned some more audio truth outdoors [message #49947] Mon, 04 September 2006 18:26 Go to next message
Bill Epstein is currently offline  Bill Epstein
Messages: 1088
Registered: May 2009
Location: Smoky Mts. USA
Illuminati (2nd Degree)
We had a day-long "tailgate" behind the building today while the labor Day crowd was inside buying paint and light bulbs.

I brought the Sorta Studio 2 "patio speakers", a 15 watt receiver and CD player.

Sitting on the asphalt, away from the building, there was little bass output below about 60 Hz. Zero Low "E" on the bass.

Amazing how powerful boundary reflections and reinforcement are. An entire octave gone!

So what does an anechoic environment do to evaluate bass? Can't, right? And if there is lttle bass, how does the anechoic room offer a correct way to evaluate mids and highs so unbalanced?

Re: Learned some more audio truth outdoors [message #49950 is a reply to message #49947] Mon, 04 September 2006 21:58 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)

Yes, that's right. Boundary reinforcement does a lot.

Outdoors, things are much clearer sounding, but bass gets lost sometimes. It takes a much more powerful speaker to drive bass outdoors than it does indoors.

Anechoic chambers are attempts to make an echo-free environment. It's not too hard to do at high frequencies, but gets much more difficult down low. Most anechoic chambers are only truly anechoic down to the midrange. That's why it's better to test subwoofers outdoors - It's a truly anechoic environment.


Re: Learned some more audio truth outdoors [message #49952 is a reply to message #49947] Tue, 05 September 2006 08:29 Go to previous messageGo to next message
GarMan is currently offline  GarMan
Messages: 960
Registered: May 2009
Illuminati (2nd Degree)
The thing that surprised me about room boundaries is how much they reinforce total volume too. I took out my amp to do some outdoor testing on speakers I built earlier this year and was very disappointed by how loud I had to turn the volume knob to get decent volume. Thought it was driver inefficiency. A week later, took the speakers inside, had the volume knob set at the outdoor level and was greeted with ear-splitting volume when I pressed play.

I was also burned for not considering room-effect on bass when I built my 5 cu ft cabinets for a pair of JBL 2235. One the computer model, the port tuning was supposed to be flat down to 30Hz. But in-room, the bass was overpowering. Through trial and error, I found that a sealed cabinet worked best. I'm beginning to understand the Japanese's taste for early shallow rolloff vs late and sharp.

gar.

Re: Learned some more audio truth outdoors [message #49954 is a reply to message #49947] Tue, 05 September 2006 09:59 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
Messages: 677
Registered: May 2009
Illuminati (1st Degree)
It's been my feeling for a long time that outdoor or chamber testing is good for common ground so one manufacturer can compare to another. It makes the baseline the same. (in theory it should be no effect)

Testing in a chamber or outdoors is no good for building speakers. The speaker needs to be tested and build for room it's intended to be used. a common type of room at the very least. Ideally, custom made for the specific room.

Re: Learned some more audio truth outdoors [message #49959 is a reply to message #49954] Tue, 05 September 2006 11:24 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)

"The speaker needs to be tested and build for room it's intended to be used."

My design philosophy is to design the speaker to sound right on axis and generate a uniform reverberent field. That makes them sound good just about everywhere. Using this approach, the main thing left is boundary influence, and making speakers designed for corners pretty much sets that. Other models are generally designed to be placed near the wall or corner, for similar reasons.


Re: Learned some more audio truth outdoors [message #49964 is a reply to message #49959] Tue, 05 September 2006 12:40 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
Messages: 677
Registered: May 2009
Illuminati (1st Degree)

"My design philosophy is to design the speaker to sound right on axis and generate a uniform reverberent field"

I dont fully understand what you mean. can you give some understanding and examples?

Re: Learned some more audio truth outdoors [message #49966 is a reply to message #49964] Tue, 05 September 2006 15:04 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)

Pretty much every speaker you've ever seen me do has this as one of its main design objectives. Controlled directivity is part and parcel of the design process. That's why my loudspeakers sound consistent throughout the room, and tonal balance is good even outside the room.

A loudspeaker's directivity determines the reverberent field. Uniform directivity along with uniform response makes a uniformly charged reverberent field. If directivity fluxuates up and down, then the reverberent field won't be uniform even if on-axis response is good.

Uniform directivity is one reason why the seven π loudspeakers sound so good. Every sound that comes from them radiates in a 90° pattern. Every horn uses a 90° flare. So from the deepest bass (set by the room wall angle) to the midrange (set by its horn flare) to the treble (set by the tweeter's horn flare) - Every sound source radiates a uniform 90°.

The bass-reflex boxes use another technique that is good. They are designed for DI matching between bass and treble. This isn't contant directivity, but it is uniform. The midwoofer exhibits collapsing directivity up to the crossover point, where it is equal to the directivity of the horn. That way the transition is smooth, so the reverberent field is smooth. Uniformly collapsing directivity isn't as good as uniformly constant directivity, but it is better than directivity that narrows up to the crossover point and then abrubtly widens back up again, as is common on most direct radiating (non horn loaded) speakers.


Re: Learned some more audio truth outdoors [message #49969 is a reply to message #49966] Tue, 05 September 2006 15:42 Go to previous messageGo to next message
GarMan is currently offline  GarMan
Messages: 960
Registered: May 2009
Illuminati (2nd Degree)
Wayne, I might be saying the same thing in a different way, but I find it easier to understand in terms of off-axis response. For good overall in-room response, you're looking for a speaker with not just smooth on-axis, but also smooth off-axis response. Uniform DI would accomplish that.

I forget for the percentage is, but the large majority of what we hear in-room is reflected sound and a lot of that comes from first reflection of the speaker's off-axis response.

Re: Learned some more audio truth outdoors [message #49972 is a reply to message #49966] Tue, 05 September 2006 19:14 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
Messages: 677
Registered: May 2009
Illuminati (1st Degree)
Thanks for the explanation, your speakers sound good.
It's been my experience that what works on paper doesn't always work best once put to use. The paper is a great place to start but the difference in a venue can require some refinement for the best design. I'll make changes in the size of the box, the tuning frequency, rigidity of the cabinet and bracing. Crossover work should also be worked on too. Sometimes changing the frequency point or the slope a little bit can make very nice improvements. Attenuation of the upper frequency horn drivers is probably the first place to get improved sound.

Re: Learned some more audio truth outdoors [message #49974 is a reply to message #49972] Tue, 05 September 2006 21:39 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)

What do you use to measure your speakers to make these refinements? Do you measure at various places in the room to get a grid of points for room distribution? Or maybe do you get a polar plot?


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