Dumb question
Is an MLTL not the resonant column of the old days, hence a BR for the purposes of this discussion?
Is an MLTL not the resonant column of the old days, hence a BR for the purposes of this discussion?
The line length primarily tunes the line (minor impact with dampening), port does not change tuning only system Q.
Thanks for the visualisation, that makes things clearer in my head! 🙂
Thanks for the comments on the sound of PP subs, I'm interested to hear what mine will sound like when they are built! Although the 'fullness' (bloated sound?) of a normal setup can be fun, super-clean output is something that I think I might like 🙂 I'm going for sub-20Hz output myself, for home theatre use, so I'm going for as much air moved as possible!
The question is more what they don't sound like 😉 But I'm not suprised you want to try yourself 😀
My impression was that below 30 hz there is almost no sound unless you crank up the volume , what you have is feeling. Which is especially what caused my huh moment, 25 hz is basically silent when compared to 40 hz. Which when you think about it makes sense as that's what the equal loudness contour plots ( when you don't have lots of 2nd 50 hz distortion that is ).
haha Yes, good point 😉 😀
I love the room-shaking stuff in movies so, effectively silent it may be (when done properly!) but fun it is 😛 (IMHO!)
I will post up my impressions when I have them up and running 🙂
I love the room-shaking stuff in movies so, effectively silent it may be (when done properly!) but fun it is 😛 (IMHO!)
I will post up my impressions when I have them up and running 🙂
This is where the supposedly benign effect of 2nd harmonic distortion is exposed for what it is: doubling. Not too good down low
"Doubling", even order distortion, is always octaves apart from the fundamental, and mimics the natural harmonic order in most instruments, making it difficult to detect with most sources. Push-pull mounting reduces even order distortion, but has no effect on odd-order distortion, which is often musically non-harmonic.
The rapid onset of odd-order distortion without the early warning of the normally louder even order distortion can be disturbing.
"The rapid onset of odd-order distortion without the early warning of the normally louder even order distortion can be disturbing. "
Yes, the rapid increase in 3rd and 5th harmonics when the amplifier clips is quite objectionable (is not objectionable otherwise).
Yes, the rapid increase in 3rd and 5th harmonics when the amplifier clips is quite objectionable (is not objectionable otherwise).
I did not read Welter's comment as amplifier clipping distortion.
He was, in my view, referring to the relative proportions of even order and odd order harmonics of the speaker generated distortion.
But are there significant odd order speaker distortions?
Cone breakup would be higher orders, but below cone break up is second the dominant distortion from the speaker?
Does Push Pull cancel ALL second harmonic distortion?
Or does Push Pull only cancel the second harmonic that results from varying gap flux on the moving voice coil?
He was, in my view, referring to the relative proportions of even order and odd order harmonics of the speaker generated distortion.
But are there significant odd order speaker distortions?
Cone breakup would be higher orders, but below cone break up is second the dominant distortion from the speaker?
Does Push Pull cancel ALL second harmonic distortion?
Or does Push Pull only cancel the second harmonic that results from varying gap flux on the moving voice coil?
Andrew,
You are correct, I was talking about speaker odd order harmonics being objectionable, though odd order amp distortion sounds bad too.
I did some PP/normal A/B testing in this thread:
http://www.diyaudio.com/forums/subwoofers/191833-push-pull-vs-normal-distortion-compared.html
The interesting thing about the front loaded PP measurements is they show it reduces even order harmonic distortion at some frequencies by large amounts, other frequencies by little.
At some frequencies PP added non-harmonic components (not related to the fundamental), and others it increased the level of the third harmonic over what the second was.
The net result was though the speaker averaged lower distortion with PP, it did not sound cleaner when pushed hard.
It may be that the relationship of the port location (a phase inversion device), to the PP may partially cancel each other out at some frequencies.
We only listened to the ported versions, I regret not having done an A/B listening test between the sealed PP compared to normal, as it “looks” better as a PP than the ported cabinet.
Dennis’ (djk) reports PP works well in his ported designs using a plenum (slot), though as far as I know he has never reported any actual A/B distortion measurements of PP plenum loaded speakers compared to normal plenum loaded speakers.
From my tests, it is apparent with the Lab 12 that PP needs to be combined with other design features and some careful attention to detail to get a net improvement in sound quality.
In other words, flipping a speaker and reversing it’s polarity won’t necessarily have a net positive effect.
Art
Hi AndrewT,
It lifts more or less all second harmonics generated by mechanical differences of parameter curves between forward and backward cone motions (inductance, suspension, Q's and flux)
Many thank for your distortion graphs, Art, they are much appreciated!
I would be interested to see some measurements for Sealed - mine will be sealed but I don't think I have the ability / tools to measure like that!
🙂
Many thank for your distortion graphs, Art, they are much appreciated!
I would be interested to see some measurements for Sealed - mine will be sealed but I don't think I have the ability / tools to measure like that!
UMIK-1, EMM6, EC8000 mics are quite affordable, REW is free. 🙂
My Hi-Fi Bass bins are horn loaded AND vented! How's that for throwing you a curve?
My experience has been that the ported/vented enclosure yields an evenness to the response down to a certain point, then rolls of quite quickly. A similar designed sealed cab will begin a much more gradual roll off at a higher frequency than the ported, but will ultimately wind up ending at a lower frequency than the ported, albeit that lower frequency will be at such a significant drop in dB response, it may be difficult to detect in some situations.
As in all cases, YMMV*
*your mileage may vary
My experience has been that the ported/vented enclosure yields an evenness to the response down to a certain point, then rolls of quite quickly. A similar designed sealed cab will begin a much more gradual roll off at a higher frequency than the ported, but will ultimately wind up ending at a lower frequency than the ported, albeit that lower frequency will be at such a significant drop in dB response, it may be difficult to detect in some situations.
As in all cases, YMMV*
*your mileage may vary
Thank you for the mic advice! 🙂
The other half has apparently bought a laptop off a friend so hopefully I can do some measuring soon 😉 😀
If you experience distortion, couldn't you just go bigger and badder and have your cake and eat it too? Get a system that you can raise your spl's without having to push it that close to its boundaries where distortion will be most evident. I'm listening to sealed boxes I just got yesterday and I'm loving the hell out of them. I might add 2 more for a total of 4 if I can find more the same.
The right combination of speaker/cabinet design/port resonance can yield a system that has a very low -6db point , basically you can tune this as low as need be. There is no bandwidth advantage in going sealed, there might be other design reasons for going sealed , bass extension is not one of them...
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