and no one measures speakers at their listening position, the room interactions will add to the graph no matter how much gating you applied.
as you know i dont have anechoic chamber, but if anyone interested for further measurements ill be glad to do some again this weekend or the next.
I measure back from the mouth because you don't listen at the mouth and the mouth measurement is kinda phony in the real world. Try Holm response or Arta for gated measurement. Isn't it summer down there? Maybe take one outside to see what I'm talking about. Measure at the mouth and then at the distance you normally listen at.
i think u still dont get what i wrote earlier
.u want to prove something that isnt there, and yes i agree in the sense that showing 0cm wont do much good, and i showed u the 130 and 160cm distance, wher its exactly the same give or take with room added reflections for 0.5-1db here and there (even though u said that there are differences)
I'm not following you, you said they measure the same at different distances then you posted picture that shows they don't at 30 cm difference - What don't i get about what you said earlier? Have I insulted you like Olson claims? My point don't buy horns based soley on "at the mouth" or "in the mouth" measurements and expect them to perform that way in the real world listening distance
It's amazing to me that people get so attached to their subconscious that they ignore their conscious. For one, if you had to redraw the graph to match the two curves then that in itself shows they don't measure the same. Secondly, If they measured the same you would only see one line. I'll ignore you though because you don't really care if your horn measure differently at different distances or not. If you did you'd do what I suggested and measure outside at the mouth and at your normal listening distance.
i suggest you read more on fundamentals of speaker design and i would suggest that you reread my posts above.
Hi All.
I'm also about to follow with similar (GPA416 in undersized sealed box).
Can you share with me the box parameters (series R, Qa, Ql) which you used for your sim !?
Of course, a link back to the relevant posts where such discussion has happened would be even better. Apologies if I'm being a bit dim in not being able to find it myself. (I've just been a casual lurker, and lot of discussion has passed me by over the eons)
Let's not go on a 'witch-hunt'... the theory is clearly documented, and if people are measuring things which don't agree, then we should start another thread to discuss why that might be.
At the risk of prolonging this.
People 'measure things' all the time which 'don't agree with theory'... but there is always a reason why. When that reason is discovered someone almost always learns something.
Back to GPA 416 midbass talk now ?!
I think it depends on definition of "don't change". Lip diffraction will always cancel differently at the mouth and further away.Can anybody point me to a reference book that shows a study where midrange horns don't change their response from the mouth to farfield (outside of a vacuum
Are you able to do a harmonic distortion sweep with your measurement system ? Would be interesting to see.
.
Regarding measuring at the mouth versus further away, there are a lot of reasons why this could be different, but no proof that I know of that says that they have to be different. Far field measurements will always stay the same with distance, that's the point. A horn with a very sharp mouth lip will certainly measure different near and far. One with no mouth diffraction may not.
As the speaker measurement tools were already set up in the basement for another project I did a series of measurements on one of the 600Hz JMLC profile horns I turned on the lathe a couple of months ago.
Gating is 1.5ms, smoothing is 1/24th octave. I would have presented the data without smoothing but ARTA won't do a series of overlays from the DFT frequency measurement tool.
The distances are flush at mouth of horn, 6", 1', 2', 4', 6', 8', and 10'. Would have done the distance in meters but could not find the metric tape measure and was too lazy to do the math...
Gary
Gating is 1.5ms, smoothing is 1/24th octave. I would have presented the data without smoothing but ARTA won't do a series of overlays from the DFT frequency measurement tool.
The distances are flush at mouth of horn, 6", 1', 2', 4', 6', 8', and 10'. Would have done the distance in meters but could not find the metric tape measure and was too lazy to do the math...
An externally hosted image should be here but it was not working when we last tested it.
Gary
Hmm quite interesting. How does the lip mate with the baffle? I assume this is not the full lip work in JLMC type horns.