# Free measurement services



## Danny Richie (Jul 12, 2009)

For years I have offered free measurement services to the DIY community and I am sure that the community here at Home Theater Shack is unaware of it. So I just wanted to make a quick post to let you guys know.

I do however like to limit the free part to mini-monitors or something easy to handle. If you send me a large speaker or something really heavy then you'll need to help me out with some handling fees. Once I get the speakers here I typically spend more time unpacking and repacking them than taking the measurements. Taking the measurements doesn't take very long. I keep my Clio system set up all the time. So dropping in a speaker to take some measured responses is a piece of cake.

Even easier for me is if you are in the area and can just bring something by. Then I don't have to handle unpacking or packing at all.

You will have to cover the return shipping cost on whatever you send me.

Here is a run down of the type of measurements I commonly take. This group of measurements was done for an on line magazine that I hosted a small speaker shoot out for.

http://www.stereomojo.com/Small Spe...omojoSmallSpeakerShootout2007Measurements.htm

You'll see some explanations on the measurements up top and some commentary on each measurement as you scroll through. Likewise I can give feedback on whatever I am sent for measuring. 

And thanks for allowing me to be a part of the community here. :T


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## Anthony (Oct 5, 2006)

That is awesome Danny! 

I'm trying to nerd-out to learn to do my own measurements -- but this would be great to independently verify designs and such. Obviously it's a lot more convenient for people near you in TX.


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## Danny Richie (Jul 12, 2009)

Anthony, 

You can always post or e-mail me your measurements and tell me how you are taking them. And then we can evaluate how you are taking the measurements and the results.


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## vann_d (Apr 7, 2009)

Sweet! Although shipping price may be a concern. I'm going to build some speakers in the near future and it would be cool to see independent measurements of them (compared to the designer).


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## Anthony (Oct 5, 2006)

Hi Danny,
Right now I'm using a mash of Speaker Workshop and REW although I keep threatening to buy SoundEasy.

I have a calibrated EMC8000 mic and a big basement. I need to get some AT fabric to make some "pillows" with Roxul Safe-n-Sound (I have a whole bat unopened) to tame my floor and ceiling reflections when testing.

So nothing advanced, but good for some quick measurements. I use impedance plots more than anything else to find problems and resonances. But I may end up taking you up on this service when I do my final wood box builds for my LCR speakers. They are small and wouldn't be expensive to ship.

Thanks.


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## Danny Richie (Jul 12, 2009)

Anthony, 

Your software should allow you to use a gated time window that will allow you to see the output prior to the ceiling and floor reflection. Typically you need to look for about a 4ms time window. See if your software will let you do that.


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## Anthony (Oct 5, 2006)

Yeah, I'm running gated, but if I can get rid of the floor and ceiling bounce, I can get data down into the midbass a bit more because my next reflection is 10 to 15 feet away.

Right now the basement is a storage disaster, so it will be the new year before I start taking any measurements again.


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## Danny Richie (Jul 12, 2009)

If you are designing a two way then 1 meter away and a gated 4ms time window will be all that you need. That will get you pretty good accuracy down to 200Hz. 

Below 200Hz can easily be calculated with box design software and port tuning. An impedance curve can also confirm the tuning of the port. And of coarse output levels below 200Hz are very room dependent.

If designing a three way then you might want to consider getting back a little further depending on driver spacing. And a longer time window will be needed. 

Below 200Hz the wavelengths start to get pretty long and it is hard to absorb them even with thick pillows. There will still be some contribution from those reflections. But on a large three way design the floor, and to some degree the ceiling reflections, must be accounted for because they will be part of the in room response. So I recommend really looking at an in room response measurement to help dial in the lower region for a large speaker.


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