RTA and the speakers ability to “throw� the sound

Fanman20

When auto eq’ing using the outdoor method you state that we should place the mic 8 – 10 feet away. This will “flatteren� the amp and the speakers response to the pink noise created by the Driverack .
In the garage you used the near /far response the far response was also only a few feet away.
Have you done any testing on the speakers ability to “throw� the sound. The difference between horn loaded and cone loaded speakers.?
When I do an outdoor gig I am generally around 100 feet away from stage. What would the difference be in the driveracks RTA response at 100 feet apposed to 8 – 10 feet away??? (on a still day)
So, Question
When we auto eq we take in the amps response , the speakers response but not the ability of the speak to “throw� all frequency at the same level any distance. Why is that.? Not all speakers have the same throw ability.
We want the best sound we can have at 100 feet not 8 feet.

Dra

Gadget?

Gadget

I'll have to address that question later I don't have time right now, but we do nearfield measurement to get a non reflective enviornment base system flattening for the system. This system(RTA based ) is not capable of measuring phase, time, or coherence so there isn't much sense in taking farfield measurements. It may be of some use to do so and use the baseline we got using this method as a comparison, but with only 28 reference points and little else to go by but frequency based volumetrics it's a little much to expect from this system. That should be left to systems that are FFT based and those that possess the skills to utilize the information they provide.

Gadget

Fanman20

I am wondering why 8 foot away, why not 20 feet, 40 feet, 90 feet.???

Is the only element that \"should\" change / decrease when moving further away be the SPL?? (in an open field)

Interesting!

Mark

Fanman20

Some more info

I have found out that at \"25C and 50% RH you have about 8dB per 30m of excess attenuation at 8kHz. So HF rolls off with increasing distance because the air absorbs it.\"

So would that indicate that we should eq at 30m or where ever the largest crowd is? (out doors)

This system(RTA based ) is not capable of measuring phase, time, or coherence so there isn't much sense in taking farfield measurements.

I dont understand. Please explain.
Why do these things matter?
speakers in or out of phase, (you can check visually and/or use 9-volt battery)
Time / delay can be measured

Mark

Dra

I think that if you look at polar plots by frequency the amount of \"throw\" is going to be different at all frequencies. So you are fighting a loosing battle to get flat response for every seat in the house (field). Best is to shoot for no \"pain\" zones. Also to consider is how multiple speakers are interacting. How many horns are you using? Good luck.

DRA

Gadget

Speakers that throw long are made to do so... propagation can also be affected by moisture, wind temperature, altitude... not the speed of propagation, but the sounds propagations characteristics...That is why we use delay towers in long throw applications. Your primary focus is going to have to be to cover the primary coverage area, Killing the peoples ears in the front rows to BLAST the frequencies to the back is of little real usefulness. In HF propagation the type of horn and it's coverage pattern affect the distance it is capable of covering. Most MID grade speakers and below use CD horn technology which makes it better for close proximity use at the detriment of long throw capabilities.

Our focus here has been and will be to go to any given performance with a properly tuned system the hallmarks of which are, proper component phase, which means:

1. That with a positive building wave form all components react in the same direction be it away from, or toward the baffles that form the front of the cabinet. (most speakers exhibit an outward motion for a positive pulse, JBL however has reverse wound some components) Phase coherence however is beyond the scope of the Driverack, or it's measurement systems...

other mitigating factors include:

2. Components are delayed properly by either physical relation to each other or delay in the crossover or processor. Note here also that digital artifacts exist in the form of delay through the crossover...those can be measured, but again are beyond the scope of this forum. Mike Kovach has measured the delay of the LR 24 and found it to be about 7.5 ms, other processors have also been measured in the 5-7 ms area, so that is a real factor here.

3. That they reproduce all frequencies within the abilities of the drivers with equal \"LOUDNESS\" limited by the accuracy of the 28 band RTA or the ears of the system tech.

The throw characteristics of the speakers and the limitations of the propagation characteristics are beyond the scope of these discussions and should be addressed on a forum such as SMAART where those characteristics can be accurately and cogently measured and dealt with.

Gadget

Fanman20

Thanks Gadget

Gadget

You are entirely welcome, we lke questions that make us think a little... Good to have you aboard...So how are things there.. we seem to be mired in a recession, and in the throws of another nauseating presidency campaign...looks to be a bleak year...

Gadget

Fanman20

Perfect one day
superb the next
I keep well out of politics and steer clear of the news (all doom and gloom)
I live on 200 acres of land in the bush on a conference centre site.
Similar to your summer camps but we average 200 people a day
I’m approaching 50 and unashamedly chasing life style

Can give you web site in a PM if you would like

Keep up your good work.
Mark