I didn't use quasi anechoic and I'm not sorry

I agree with tktran303 ^

It can work, if you have a 2-way design with a crossover frequency above ~ 1 kHz... and if you have a good room with well-behaved bass response... and if you have the experience and technical judgement to make the right assumptions and interpret the low frequency free-field measurements.

j.
 

eriksquires

Member
2013-05-10 4:11 pm
You simply have to open the freq response file you made, open REW (or your app), click to display THD, and post it.

You seem to not like that idea?
Hi Ben,

I take requests that are polite and that I can fulfill within my own time and energy and may get to them. As it turns out I saved the FRD but not the impulse response for these charts so re-running the tests will require some effort on my part right now. I'm sure the bass has much higher distortion than with a sub, but it doesn't matter since it sounds really good for my listening levels.

If I get back to setting up for measurement again I'll be sure to measure and post the distortion charts.

Best,

E
 

eriksquires

Member
2013-05-10 4:11 pm
I think it’s good practice to do it properly, if for no reason other than you taking your speaker for a demo to a friends place who doesn’t live in an apartment; or group listening demo room in a large space well away from walls, well that could be embarrassing…

Call me a misanthrope then. :) I really did have a specific placement set up in mind during design, and I'm certainly not carting these speakers anywhere. :)

I should point out that I avoided 2 other design issues with quasi anechoic: Baffle step compensation and port summing.

Had I attempted quasi anechoic measurements I would have also had to compensate for the baffle step mathematically. I found the summing of the rear port to the front quite complicated and at least for my lack of experience had no way of telling if I was doing it right.

In the end by using 1m distance measurements in room I solved all of that with high accuracy. The chances of me getting either the baffle step math or the port summing math wrong was high.
 
Hi Ben,

I take requests that are polite and that I can fulfill within my own time and energy and may get to them. As it turns out I saved the FRD but not the impulse response for these charts so re-running the tests will require some effort on my part right now. I'm sure the bass has much higher distortion than with a sub, but it doesn't matter since it sounds really good for my listening levels.

If I get back to setting up for measurement again I'll be sure to measure and post the distortion charts.

Best,

E
Can you quote that part of my post you felt was" impolite"? Granted, providing the forum with THD may prove highly flattering or possibly embarrassing to you. But that doesn't make my request impolite or improper in a public forum. Your title and OP state your choice to be provocative compared to generally accepted POV. So fair enough to ask you to clarify further with distortion data.

For some apps (including REW), there is no need to re-run tests. Just a matter of pressing the THD ("Distortion") button.

B.
 

eriksquires

Member
2013-05-10 4:11 pm
I didn't say it was impolite. I said that's what I accepted and that I'd get to them when I get to them.

Yes, the point of this post was about measurement technique, and balancing speaker output to the room. I did not mean to say you could get impossibly deep bass without distortion, but that question is interesting and I will eventually get to that data.
 
I believe you have have answered my question: "impossibly deep bass" is not likely "without distortion". From what you say, I gather the distortion was high and possibly even high enough to make your low frequency plot invalid.

Lots of speakers have high bass distortion that is quite astonishing. And impressions by ear are not reliable standards in the bass (or anywhere else).

B.
 
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celef

Member
2012-11-26 7:40 pm
i find truerta to be helpfull when measuring inroom responses, first i measure the noise floor of the room, store that curve as overlay, and then measure the inroom system frequency responses at levels well above the noise floor. i find it a bit hard to believe that a simple 6.5" midwoofer can achieve this low freq extension as in your plot by some room gain. still, a measurement does not tell much about how we percieve sounds, increase driver size and the change is a night and day difference even though this will not be seen in the measurement, i would like to see measurements came with some sensoric scale instead
 

eriksquires

Member
2013-05-10 4:11 pm
Hi all, I have added distortion measurements from OmniMic to the original post:

The blue line is the combined 2nd through 5th harmonic. At 20% if I hover over it reads about 2%. Honestly I think that seems very low. Comments?

1642704129048.png
 
Thanks for posting distortion (I assume that is THD+N).

If you mean "at 20 Hz", then you are correct, 35 dB down ("2%") is simply far-fetched for any speaker I know of. Of course, I'd say that about the FR for a small-size wide-range driver delivering essentially flat response 17 to 15 kHz. But I may be reading this all wrong or you may be due for international acclaim.

B.
 

eriksquires

Member
2013-05-10 4:11 pm
If it helps, I just started using Anthem's Automatic Room Correction, and their measurements of the L and R speakers are not far off from what I posted. So far I've used OmniMic, Room EQ Wizard and now ARC and they all agree that there's a lot more bass here than we'd normally expect.
 
Still awaiting clarification of the THD+N figure, but at very low volumes and with lotsa EQ, I suppose you can get great FR and great THD. In practice, no way to perform such tests because the noise in your system (which includes noise in your room) makes the testing unfeasible. But at any level that is more than barely audible, in my estimation, not possible to get great results like that.

Have you assessed how loud was your test - even just testing with your smartphone at what you recall is the level and - I hope - the level at your chair?
 

eriksquires

Member
2013-05-10 4:11 pm
I am afraid I have a raft of other projects, bentoronto, and I will have to dig into exactly what OmniMic is doing, but I posted the dynamic range tests on the blog as well as the nominal distortion measurements were taken at 75 dB @ 1 kHz at the microphone, which was at the couch.
 
With ‘echoic’ measurements the level relation between a frequency and it’s harmonics becomes quite compromised because you are measuring the room response, not the speaker. So any relations you think you see in your measurement are invalid. This makes the resulting ’THD’ figure pretty useless, even when it’s smoothed out in Omnimic, such as the example. In other words: forget it.
 
Unless your only interest is the speaker rather than the sound in your room, then:

1. THD plots aren't read by frequency since you can't "adjust" distortion at say 85 Hz. So not important if there's a bit of an extra bump at 85 Hz due to the room.

2. The sound at your seat ("echoic") is the reference I'm interested in. There's reason to believe you don't hear the room in the way a mic does because your hearing kind of corrects the room sound so Uncle Harry always sounds like Uncle Harry in all rooms.

3. Up-close mic testing is not influenced by the room so much.

As Geddes has shown, THD comes a lot closer to your perceptual experience of annoyance due to distortion if you correct distortion for audibility (good ol' Fletch-Munson).