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I know that measuring for speaker response indoors is probably folly but I thought I''d give it a go since I was all set up from dialing in the active Xover up for my DIY 3 way boxes ....

The three drivers were measured with the omni Dayton about one inch on axis. The cyan color trace was taken from approximately 2.5 feet , center of baffle board ( mtw configuration) . for this screen shot I set the IR window - Right window to it's smallest setting ( .5 milliseconds )frequency resolution is indicated to be 7.97 Hz with this setting .The driver traces were left at the default 500 ms setting.


dec 2 mad weekend.jpg

My question is how much of the room has been removed by this change in gating , and how low in the spectrum is " accurate " (LOL):sn:




here is what 300 ms looks like ....

dec 2 mad weekend2.jpg

The good news is it's a pretty big room ( 600-700 sq ft) and has a vaulted ceiling that 24ft high on one side then goes down to the usual roof line ( say 10 ') It's pretty live ( as it's got wood floors )

Obviously In my fantasy world the response in the first graph is accurate as hell ( I might even like the hump between 5 -7k for my old ears !!...joking...) is that hump room even at that frequency ??

needless to say more tweaking will commence , but I'm liking the sounds allot so far !!


TX for reading !
 

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... My question is how much of the room has been removed by this change in gating , and how low in the spectrum is " accurate " (LOL):sn:
The 7.97 Hz is not indicative of the lower limit of this particular measurement because the left window is 99% before the IR, probably at the default 125 ms.

Here are some comments based on my experience (non-expert).
For each driver I would recommend the left window be placed only 0.1 to 0.5 ms before the initial rise of the IR, basically as close as you can set it to the IR, but still where the IR is at the 0 %FS level. The right window should be set to where the IR starts to settle back to zero initially, maybe around 1 ms for the TW, 2.5 ms for the MR and significantly longer for the W maybe try around 50 ms. With these rough settings REW will indicate the correct lower limit of the FR that is valid and you can adjust the right window to suit your need. [Actually if REW reports 500 Hz as the lower limit for the TW the second measuring point is 2x500 (at 1 kHz) and the third at 3x500 (1.5 kHz) so the fit of the line for the first 2 or 3 points is not highly accurate and is overly smooth, but that is another story.]

I have read that it is better to measure the TW and MR around 3 to 5 ft. basically as far away as possible before the room is overly impacting the results. The further you are from the floor or nearest boundary less the room impact will be. Measuring MR and TW very close does not properly pick up the effect of the baffle, the baskets and other nearby features.

The W is measured very close to the cone indoors to estimate the anechoic response as that is the best that can be reasonably done. If the box is vented you will also need to measure the port and add them together.
 

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Immensely helpful jtalden!


next after learning.jpg

This software is amazing !!.. I found some threads W/ SAC talking about measuring speakers and how dispersion and power responses are every bit as important as a flat spectrum ( and the room itself ) ... I have some friends with a really big back yard ; I may just take these out there and drag the measuring rig along !!!

TX again for those great tips !!
 

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Because of the wide gating the cyan response shows lots of HF impact from the room. The TW only response better represents the actual anecohic HF response.

The manufactures response curves for each driver is probably usually more accurate that than we can measure indoors, even though it is probably an average or maybe a "best case" condition and doesn't include the baffle effects.

The room is a major player ultimately and the anechoic response is not the critical issue imo. It may be fun to measure it though - enjoy!
 
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