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Old 31st March 2009, 07:35 PM   #21
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JBL2020H 80Hz hypex in the garden.
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Old 31st March 2009, 07:36 PM   #22
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Same horn in room at seating position.
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Old 31st March 2009, 08:10 PM   #23
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Quote:
Originally posted by bentoronto
But the music room performance is all that counts in DIY.

If the music room performance is all that counts why do you need a measurement 'without room' ?

Nor am I optimistic about "... well, you just subtract out the room response." Is there a way of doing so?

Yes - you physically remove the room by placing the speaker out in open space and measure there....

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Old 31st March 2009, 09:55 PM   #24
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I appreciate both you's posts and I hope all this is being taken in the right scientific-inquiring way.

First, if I may quote my very first post in this thread:

"On good theoretical and practical grounds, I like pink noise or frequency sweeps using 1/3 octave bands - I have some signals off an old CBS-labs test record. The ear and the SPL meter show some agreement and the measurement experience makes seems coherent."

Yes, you have a fightin' chance of meaningful measurements in your living room with noise. Moreover, the 1/3 octave stuff I grew up with is crude and not great help in fine-tuning. Now I see you can do really fine work at 1/24 octave bands that produces a reliable (consistent, repeatable, fine-enough) trace. I am in your debt for that knowledge.

What I'd like to see now, is the relation of the indoors and out of doors "racquetball court" curves on the same chart in order to assess the value of collecting out of doors data. Does in-room variation swamp out of doors curves?

To operationalize a criterion, could you usefully set a bass equalizer from the racquetball curve?
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Old 31st March 2009, 10:21 PM   #25
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So basically all you want to do is EQ your klipsch to a 'flat before room modes' condition ?, but cannot as it needs the corners to function as a 'proper' horn, meaning the outdoor measurements are useless as the speaker will not work without the floor / walls to complete its horn flare ?

I understand your position now and why you was so 'put out' by Tom D's suggestions.......(and why you spoke about raising the walls with the speaker)

In your case I think you need to find 2 very high buildings that join at right angles. Get an in car amp and a laptop adapter / inverter so you can power the laptop and preamp / mic combo. This gives you a mobile testing station so you can drive out, stick the horn in a good test corner, and measure it. A standard mic stand should hold the mic in the right position (equidistant from all surfaces)

Hopefully that will get you the info you're searching for, although maybe the cost of the equipment will be the deciding factor.

Rob.
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Old 31st March 2009, 10:26 PM   #26
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Maybe 2 pieces of 8' x 4' 25mm mdf could be screwed together and placed on the ground to approximate the corner ?

Love my paintshop skills

Rob.
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Old 31st March 2009, 11:26 PM   #27
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Quote:
Originally posted by RobWells
So basically all you want to do is EQ your klipsch to a 'flat before room modes' condition ?, but cannot as it needs the corners to function as a 'proper' horn, meaning the outdoor measurements are useless as the speaker will not work without the floor / walls to complete its horn flare ?

I understand your position now and why you was so 'put out' by Tom D's suggestions.......(and why you spoke about raising the walls with the speaker)

In your case I think you need to find 2 very high buildings that join at right angles. Get an in car amp and a laptop adapter / inverter so you can power the laptop and preamp / mic combo. This gives you a mobile testing station so you can drive out, stick the horn in a good test corner, and measure it. A standard mic stand should hold the mic in the right position (equidistant from all surfaces)

Hopefully that will get you the info you're searching for, although maybe the cost of the equipment will be the deciding factor.

Rob.
Wait. Not my thread. Sorry to hijack. But I am very interested in the question.

No, my purpose isn't to use out of doors measures. On the contrary, I am skeptical that they can be useful with a woofer and esp. with a corner horn (and hope to be proven wrong).

As a kind of conceptual test case, I am asking if equalizing based on an out of doors curve would be adequate. If yes, then I guess out of doors is useful. If not, then, not. To start with, what do the indoors and out of doors curves look like when on the same chart? I am just trying to formulate a test case to represent the words "Gee, the two curves are kinda' alike."

Earlier, and esp. in connection with Tom's posts, the question of economic feasibility (and structural feasibility) were raised. These are of the greatest practical importance and I'd like to learn more about the price for a 1/24 octave filter, time window, and whatever else is needed too.

But first, the conceptual test case.
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Old 31st March 2009, 11:54 PM   #28
jbell is offline jbell  United States
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In the PA world... the best thing you can do is take your system to a big open field, and eq it to the sound you are looking for. Once you do that, then you find out that your eq sounds pretty good in all rooms, and only needs small adjustments.

BEFORE that outdoors eq is accomplished, you find that you are constantly fighting the eq from place to place.

I believe the same applies to your situation. Take it out to a tricorner, measure, and eq it to what you really want, and then... and only then, bring it back indoors.

My analogy is trying to find the best tomato in a BLT. When the tomato is in the sandwich, it's much more difficult to identify a great tomato from a good one, because of the competition of all of the other tastes. However once by itself, it's much easier. Once you take that great tomato and put it back in the BLT, the BLT is just that much better.

The same is also true in the speaker design phase. (Tom's comments) You can't tell the strong and weak points of a design, indoors... you need to take it outdoors to measure.

BTW -- I'm acutely aware of the issues that happen when dealing with bass horns and indoor measurements. I based a stadium system on published SPL charts... only to find out that the published charts were measured indoors. Obviously the design did NOT perform as advertised....

hope that helps.
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Old 1st April 2009, 01:51 AM   #29
Mark Kravchenko --- www.kravchenko-audio.com
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Default There are bits a pieces of good info in every post.

To the point of sharpening the pencil a bit more.

I think we all know how to measure the response. We all agree that measuring a horn at distance outside gives an accurate result.

Most of us have this evil thing called winter. I have been working on a couple of horns all winter and I never seem to get them to measure the same inside as outside.

What has been posted is pointing to the direction of measure outside and then figure out what is not going right inside.

Unfortunately that is what we all do with horns. After it is actually nice here in Ottawa I'm going to try some experiments to see if I can really relate a close mic response to a 10 meter ground plane response.

If it works to some degree I'll post it and see what you guys come up with. Because if there is some way to accurately predict an in room response by a little jugling of the db's down a bit then I can produce better results in the winter to!

Mark



"On this half of the planet we are going into spring." Sorry Rob I thought you lived down under. I should look more closely sometimes!
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