# measuring DIY project freefield



## atledreier (Mar 2, 2007)

Hello.

I've been using my semi-diy system for a while now, and while very pleased, I think it's time I get them set up properly.

My room is treated decently, but still introduce a mess of the impulse and frequency response. I thought I'd haul the stuff outside in the garden and measure there.

My garden isn't very big, so at most I could get the speaker and microphone around 4m from the nearest boundary, not counting the ground. Is that enough, or do I have to drive the gear out to a football field? Any precautions or pitfalls I need to know about?

Also, while i have the stuff outside and am bothering the neighbours, what measurements do I want to take?

The setup is a Klipsch KL-650THX speaker and a midbass module with electronic crossover and DSP. I want to find the optimal crossover and phase for the transition (currently at 200Hz). I will also do compression tests while I'm out.

Will the measurements and results be viable when I put the gear back in, or will I have to get phase and timing right with the gear in situ, in the spot they are going? 

I have three of these systems, used for LCR. Can I assume they are similar enough that settings for one will apply to the other two?


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## fusseli (May 1, 2007)

Nice setup.

OK my big question is, why do you want them dialed in perfect in an open environment? As soon as you bring them back into your room, the room reflections, speaker placement, etc etc will change the response of your speakers. At that point it's really a gamble if it will actually help anything. Getting open measurements like you want would probably be more gee-whiz info than anything, it's not like you're setting up a final mass-produced product that will be used in a wide variety of locations/rooms.

I say save yourself the time and hassle and do your sweeps, experiment with different Xover points, and dial in phase in-room where it matters most. I'm assuming your active Xover has variable phase and that's what you're referring to? If so, that will depend on the Xover point and the speakers it's joining and not the environment the speakers are in. That being said, the best Xover point and phase alignment will should be nearly identical for each L/C/R. What I would do: Tweak the Xover point until voicing of your speakers sounds the best, then, play a test tone at the Xover point with an SPL meter in hand. Then adjust the variable phase control until you get the loudest reading on the meter. The 200Hz range might be getting close to being directional, so you might want to put your meter at your listening location for that test (the same procedure is used for dialing in a sub + mains).


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## atledreier (Mar 2, 2007)

My thinking is that the less cluttered the impulse, the easier I can dial in the phase and amplitude at the crossover. Besides, I'm really just curious how the system measure without the room cluttering up the measurements.

But this may be moot, as I am most likely selling the Klipsch speakers and doing a full DIY speaker system with dual Eminence 3015LF and a Beyma horn.


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## Zeitgeist (Apr 4, 2009)

atledreier said:


> My thinking is that the less cluttered the impulse, the easier I can dial in the phase and amplitude at the crossover. Besides, I'm really just curious how the system measure without the room cluttering up the measurements.


I think that there might be some benefit to coming up with crossover points in freefield - since you will have fewer "distractions" when you're not in the room and doing so. I would wonder a little bit about what would happen if you have a room mode that causes you to pick a different crossover point - if you did it all inside.

In terms of EQ though, I think that you'd be faced with making dramatic changes once you get it inside - enough so that you'd be doing everything twice. Although, it might give a good baseline to go from.

I guess I'll have to see what I come up with - when I'm in your shoes fairly soon - and coming up with crossover points and EQing a 3 way active speaker that I'm working on..


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## atledreier (Mar 2, 2007)

I won't do any EQ, of course. I will experiment a bit with crossover frequency and slope, then maximize the phase response. Then I'll do EQ in room. Usually won't be much, I have Audyssey MultEQ XT32 doing the voicing and roomcorrection.


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## Zeitgeist (Apr 4, 2009)

atledreier said:


> I won't do any EQ, of course. I will experiment a bit with crossover frequency and slope, then maximize the phase response. Then I'll do EQ in room. Usually won't be much, I have Audyssey MultEQ XT32 doing the voicing and roomcorrection.


Ahh OK. I saw "electronic crossover and DSP" so I was thinking that DSP included EQ features and you were going to use them..


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## atledreier (Mar 2, 2007)

I will probably use some EQ, but that will be tailored to the room/speaker after placement.

The main EQ job goes to Audyssey, of course.


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## Zeitgeist (Apr 4, 2009)

atledreier said:


> I will probably use some EQ, but that will be tailored to the room/speaker after placement.
> 
> The main EQ job goes to Audyssey, of course.


If you're familiar with Room EQ Wizard and plan on using it - be sure to post some graphs when you get around to it..


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## atledreier (Mar 2, 2007)

I will post measurements.

I have some in-room plots from when I first set them up. This is without EQ, but heavy smoothing.


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## fusseli (May 1, 2007)

Ya pretty sure you can find a good Xover point, slope, and dial in the phase all in-room. I'm fairly certain that a room isn't going to effect where two drivers are in phase when they are stacked close together (200Hz seems a bit high for that, no?).

I must admit though, wide-open response would be pretty curious for a DIY setup.


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