why can't we can test our loudspeaker and crossover in rooms which will be used there ?

[dipankar.rout]

Since, we don't have the facilities of anehoic chamber to test diy speakers. I doubt the accuracy of Quasi-anechoic theory of measurement. But why we can't test in the rooms in which it is going to be placed. We know that frequency response of speakers in anechoic chamber will vary in real room environment but we can't test the speakers in the room in which it is to remain. And with this we can really so how this speakers is going to behave in that room.

 

[slipperybidness]

Since, we don't have the facilities of anehoic chamber to test diy speakers. I doubt the accuracy of Quasi-anechoic theory of measurement. But why we can't test in the rooms in which it is going to be placed. We know that frequency response of speakers in anechoic chamber will vary in real room environment but we can't test the speakers in the room in which it is to remain. And with this we can really so how this speakers is going to behave in that room.

Why can't you measure your speakers in your room?

Just spend the $ for the measurement gear, then measure your speakers in your room.

 

[herbu]

But why we can't test in the rooms in which it is going to be placed.

We can. That's why we regularly recommend trying speakers in your home before you buy them, if possible. And it's one reason why a number of speaker manufacturers, especially internet direct, have a 30-day return policy.

 

[shadyJ]

Since, we don't have the facilities of anehoic chamber to test diy speakers. I doubt the accuracy of Quasi-anechoic theory of measurement. But why we can't test in the rooms in which it is going to be placed. We know that frequency response of speakers in anechoic chamber will vary in real room environment but we can't test the speakers in the room in which it is to remain. And with this we can really so how this speakers is going to behave in that room.

Quasi-anechoic measurements can match anechoic measurements. This has been shown countless times, and I have seen it myself.

 

[KenM10759]

I enjoy looking at test measurements. It's entertaining, but in my experience does absolutely nothing to indicate how any speaker is going to sound in my room and in that position.

If I were building speakers it might be fun to know how they measured, but I'd be building them for myself and they're going to sound great to me whether I use Raal tweeters, Scanspeaker mids and Seas woofers, or an apple crate, some plastic wrap, some bell wire and a cheap magnet.

 

[shadyJ]

I enjoy looking at test measurements. It's entertaining, but in my experience does absolutely nothing to indicate how any speaker is going to sound in my room and in that position.

Good measurements should make the sound of a speaker be predictable in your room at your listening position by allowing you to correlate the test measurements with your own measurements or the overall sound. If measurements do nothing to indicate how the speaker is going to sound at your listening position, you are either using them incorrectly or are listening in a very bizarre room.

 

[KenM10759]

I can't make my own measurements so I depend upon my ears to tell me if tweeters are too bright, midrange too dull, low frequencies dull or flatulent.

I've never actually heard specific deficiencies seen in measurements sound quite as bad as they look "on paper."

 

[shadyJ]

I've never actually heard specific deficiencies seen in measurements sound quite as bad as they look "on paper."

Agreed, it's easy to see flaws in many measurements, but you always have to put them in context of audibility. And even then sometimes certain room acoustics can mask flaws that would otherwise be audible.

 

[Swerd]

Quasi-anechoic measurements can match anechoic measurements. This has been shown countless times, and I have seen it myself.

shadyj is right.

Since, we don't have the facilities of anehoic chamber to test diy speakers. I doubt the accuracy of Quasi-anechoic theory of measurement. But why we can't test in the rooms in which it is going to be placed. We know that frequency response of speakers in anechoic chamber will vary in real room environment but we can't test the speakers in the room in which it is to remain. And with this we can really so how this speakers is going to behave in that room.

Why do you doubt the accuracy of Quasi-anechoic measurements? I could be wrong, but I get the impression that you have no direct experience doing this.

First, it is important to place the speaker and the microphone far away from walls (see why below). For a speaker, this location is likely to be quite different from locations in a room where speakers are normally kept. That doesn't matter if you want to know how the speaker itself performs. Placing the microphone is also important. Usually tweeter height, about 1 meter away, is a good starting point, but this has to be determined with a lot of trial and error for each speaker. Obviously, this can vary by a lot depending on whether you are measuring a woofer, tweeter, or mid range as unfiltered drivers, or all drivers with a test crossover.

With software meant to be used for crossover design and speaker measurement, there is a 'time gate' feature that allows the user to select a narrow range of time when the test microphone is open. For a quasi-anechoic measurement, this would be from a fraction of a millisecond (msec) to about 4 msecs (if I remember correctly). This time frame allows the microphone to hear the speaker's response to a pink wave pulse, but not most reflections from room walls, as they take longer to arrive at the microphone. Usually this cannot avoid a subtractive null in the frequency response somewhere between 100 and 200 Hz caused by floor bounce. But these are easy to identify by seeing how the center of the null varies as you move the microphone closer or farther away. If you only show a frequency response from 200 Hz and up, it should be quite similar to that done in a genuine anechoic chamber.

 

[herbu]

an apple crate, some plastic wrap, some bell wire and a cheap magnet.

That sounds about right for Spencer, (MA or NC).
BTW, for some reason I looked up the population of Spencer, MA. Here's what I found on suburbanstats.org...

Interesting.

 

[KenM10759]

That's not even close to reality! This town is now over 12,000 people, not 5700. And I can assure you we're a lot more diverse than those numbers would suggest. We have new schools, a master plan, stable government and relatively low tax rate.

We do have economic diversity too, with a few dozen multi-million dollar homes, most within 2 miles of depressed farm properties. Very little urban blight, limited to a couple streets in the center of town and even that's not nearly as bad as I left from the nearby city (Worcester) some 28 years ago.

This is however a desert of audio interest, or at least access to it. The closest good hi-fi shop was about 15 miles away and closed about 5 years ago. So now we have a couple of Best Buy box stores within a 30 minute drive, a BB Magnolia about 40 minutes away. I drive a touch over an hour to hit a great shop in NH.