Hi, what I wanted to say is that bigger driver does not always equal less distortion. That comes from personal experience and meaurement data, which can be looked upon online. There are a lot of variations in built quality, motor design, suspension design and so on. So your statement "In my humble opinion, it is about the size. With the size comes lower distortion." contradicts this.
Regards
For any given driver, lower excursion always equals lower THD. You can get very clean bass from cheaper large cone drivers, even if the motor isn't designed as well, but the cone's acoustical qualities will matter the most under these conditions.
The amplifier has to have very tight control of the VC and needs to deal with phase shifts very well, so it can soak up the back EMF from the driver and not let it negatively affect VC dampening.
Many speaker guys claim the dampening effect of Alu VC formers hurt low level detail retrieval. This simply isn't true, as some of the best driver's have Alu VC formers. This affects the midrange far more than the bass and tends to lower THD caused by electro-mechanical, magnetic flux and self inductance non linearities in the motor. At low output and excursion levels, these things have more affect on SQ than the driver's mechanical non-linearity attributes. These come into play and take over at higher SPLs.
The amplifier has to have very tight control of the VC and needs to deal with phase shifts very well, so it can soak up the back EMF from the driver and not let it negatively affect VC dampening.
Many speaker guys claim the dampening effect of Alu VC formers hurt low level detail retrieval. This simply isn't true, as some of the best driver's have Alu VC formers. This affects the midrange far more than the bass and tends to lower THD caused by electro-mechanical, magnetic flux and self inductance non linearities in the motor. At low output and excursion levels, these things have more affect on SQ than the driver's mechanical non-linearity attributes. These come into play and take over at higher SPLs.
its a simple matter of total Sd and Xmax, no complications. Only at the extremes of its excursions can you hear the driver for the most part.
Since we are talking the whole lower spectrum, if you are consider 96db/1m to be max average then we must add another 15db for headroom as the sub bass is a spectrum where rms and true peak can be the same level.
Yeah, but I think you're building up a strawman here (figure of speech). No one is saying you can't find an example where a large crappy woofer performs worse than even a single high-quality woofer. But the ranges of performance do not totally overlap, even when normalizing for volume displacement.
Here's the KEF LS60, with a quad of 5.25" woofers.
Reference:
https://www.erinsaudiocorner.com/loudspeakers/kef_ls60/
Reference:
https://www.erinsaudiocorner.com/loudspeakers/kef_ls60/
Hi, I also thought in this way until tested cheap drivers from different brands, in the price category of about 100 euros a piece. Four 12" were used for evaluation. One brand drivers distorted about in 2-4% range from 40 Hz to 300 Hz, for another it was less than 1% for the same level. That's 3-4x times the difference at least, while drivers being very similar in parameters like Fs/Qtc , same diameter etc.
I think there is a wide spread assumption that distortion is mostly related to excursion only. This assumption is false, and current flowing through the voice coil has a big influence too. Otherwise, why would one see high distortion in some mid range tests where excursion is very low ?
Anyone interested - there is a good read :
https://www.rmsacoustics.nl/papers/whitepaperdistortion.pdf
Regards
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yes that's a good read indeed, i like the part in the conclusion where there talking about low frequency distortion and mention excursion/displacement.
5 Low Frequency Distortion
When measuring the distortion of loudspeakers, generally figures of around 0.1-1%
are shown over the mid and high frequency audio band with a steep increase to
levels of even sometimes 100% towards very low frequencies.
Two factors are responsible for this phenomenon.
• High stiffness of loudspeaker cone suspension including enclosure.
• Large cone excursions.
5 Low Frequency Distortion
When measuring the distortion of loudspeakers, generally figures of around 0.1-1%
are shown over the mid and high frequency audio band with a steep increase to
levels of even sometimes 100% towards very low frequencies.
Two factors are responsible for this phenomenon.
• High stiffness of loudspeaker cone suspension including enclosure.
• Large cone excursions.
It's a bit of infotainment.
But it's not a really a study, is it?
It's more of a "Proposals why active feedback control is used"
A real study should show some empirical data.
on page 16 "Assume a system with a 200 mm diameter subwoofer in a 15 litre enclosure with f0 = 45 Hz, which should produce a frequency of 20 Hz at 90 dB. This requires a large excursion of 10 mm" .... Due to the fact that the second harmonic of 2·20 = 40 Hz is on the +2 slope of the frequency response, the sound pressure of this distortion will be a factor 2 2 = 4 higher relative to the sound pressure by the first harmonic at 20 Hz. This means that the relative second harmonic distortion becomes 4 · 15 = 60%. The third harmonic at 3·20 = 60 Hz will “only” get an increase of (4.5/2)2 = 5, due to f0 = 45 Hz, above which the frequency response is flat, giving a relative distortion of 5·5 = 25%. It is clear that such levels of distortion can only be solved by active control."
The "White paper" references the SEAS L25RO4Y (10" subwoofer) on multiple occasions.
This is a simulation of what happens when you put a SEAS L26ROY4Y subwoofer into a 15L sealed box, and try to reach 20Hz @90dB:
Why not build it and measure the distortion?
Suppose there was no simulator to work with back in 2017, when his was published. Well, then, at least do it empirically. Here's what the the late Sigfried Linkwitz did when he went looking for woofers to put into a 1/2 cu ft sealed box:
"Two drivers were considered, the Peerless 12" SLS 830669 and the 10" 830668 since they are relatively low cost, are available worldwide and have adequate volume displacement. The 12" driver is capable of 4 dB higher excursion limited SPL because of its larger piston area. The closed-box1.xls spreadsheet was used to investigate how these two drivers would behave in a small 14 liter box when driven from a 120W amplifier. Alister Sibbald added a driver data base to the rearranged spreadsheet. Being able to see the graph change as you change the variables gives better insight into the way the variables interact: Closed-Box-WithDriverDb.xls
Italicized by this author for emphasis.
Reference:
https://linkwitzlab.com/Pluto/subwoofer.htm
Here is a 10" woofer in a 1 cu foot sealed box playing 20Hz at 90dB:
this author's SUMMARY:
Choose the right woofer for the right box (or vice versa)
But it's not a really a study, is it?
It's more of a "Proposals why active feedback control is used"
A real study should show some empirical data.
on page 16 "Assume a system with a 200 mm diameter subwoofer in a 15 litre enclosure with f0 = 45 Hz, which should produce a frequency of 20 Hz at 90 dB. This requires a large excursion of 10 mm" .... Due to the fact that the second harmonic of 2·20 = 40 Hz is on the +2 slope of the frequency response, the sound pressure of this distortion will be a factor 2 2 = 4 higher relative to the sound pressure by the first harmonic at 20 Hz. This means that the relative second harmonic distortion becomes 4 · 15 = 60%. The third harmonic at 3·20 = 60 Hz will “only” get an increase of (4.5/2)2 = 5, due to f0 = 45 Hz, above which the frequency response is flat, giving a relative distortion of 5·5 = 25%. It is clear that such levels of distortion can only be solved by active control."
The "White paper" references the SEAS L25RO4Y (10" subwoofer) on multiple occasions.
This is a simulation of what happens when you put a SEAS L26ROY4Y subwoofer into a 15L sealed box, and try to reach 20Hz @90dB:
Why not build it and measure the distortion?
Suppose there was no simulator to work with back in 2017, when his was published. Well, then, at least do it empirically. Here's what the the late Sigfried Linkwitz did when he went looking for woofers to put into a 1/2 cu ft sealed box:
"Two drivers were considered, the Peerless 12" SLS 830669 and the 10" 830668 since they are relatively low cost, are available worldwide and have adequate volume displacement. The 12" driver is capable of 4 dB higher excursion limited SPL because of its larger piston area. The closed-box1.xls spreadsheet was used to investigate how these two drivers would behave in a small 14 liter box when driven from a 120W amplifier. Alister Sibbald added a driver data base to the rearranged spreadsheet. Being able to see the graph change as you change the variables gives better insight into the way the variables interact: Closed-Box-WithDriverDb.xls
|
The free-air resonance at 28 Hz of the 12" driver is pushed up to 103 Hz due to its relatively high equivalent compliance of 172.4 liters compared to the 14 liter box. The high combined stiffness means that the power amplifier is not adequate to obtain Xmax. It would have to be a 1.2 kW amplifier to get the maximum 94 dB SPL at 30 Hz. pluto-sub12.xls |
The 10" driver has a stiffer suspension with VAS = 69.3 liter. The in-box resonance is not quite as high and better use is made of the available amplifier power. The higher stiffness also reduces the static displacement of the down firing cone to a mere 0.23 mm. Thus the 10" driver was chosen. pluto-sub10.xls |
Italicized by this author for emphasis.
Reference:
https://linkwitzlab.com/Pluto/subwoofer.htm
Here is a 10" woofer in a 1 cu foot sealed box playing 20Hz at 90dB:
this author's SUMMARY:
Choose the right woofer for the right box (or vice versa)
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The worst thing about the woofer distortion is harmonics generated by woofer distortion polute the midrange frequencies. No matter how clean and advanced your midrange is, it can be all ruined by crappy woofer (big or small does not matter, if it distorts).
I try to attend as many live music concerts, especially classical music, with acoustic instruments. While i am very happy with sound of my system/s, i feel like bass is not completely matching the live performance. There are obviously many reasons, concert hall being way bigger than my listening space, recorded music being compressed/manipulated in comparison...to start with.
Bass in concert hall is just so effortless, while even if i use four 15" woofers, they still sound constipated. Perhaps some gentle sound expander could be applied (old pioneer will do) just to bass, not affecting mids and highs.
While my ht is using only two 15" in big closed boxes, i am ok there, since its just for movies. Other system has two 15" car woofers which boom a lot...but its ok for spare room. When it comes to garage/party system, two 15" PA woofers are great, who cares about distortion, right?
There is still plenty of work to be done in woofer distortion...
I try to attend as many live music concerts, especially classical music, with acoustic instruments. While i am very happy with sound of my system/s, i feel like bass is not completely matching the live performance. There are obviously many reasons, concert hall being way bigger than my listening space, recorded music being compressed/manipulated in comparison...to start with.
Bass in concert hall is just so effortless, while even if i use four 15" woofers, they still sound constipated. Perhaps some gentle sound expander could be applied (old pioneer will do) just to bass, not affecting mids and highs.
While my ht is using only two 15" in big closed boxes, i am ok there, since its just for movies. Other system has two 15" car woofers which boom a lot...but its ok for spare room. When it comes to garage/party system, two 15" PA woofers are great, who cares about distortion, right?
There is still plenty of work to be done in woofer distortion...
Do you have measurements of your lf response at a few points inthe room?
There are plenty things influencing this experience. I would bet the most important one is you are sitting in a very small room (acoustically) compared to an orchestra performance. You have strong modes at low frequencies but a lot of influence up to about 250Hz - and this area can mask a lot!
Lambda/4 dips (SBIR) are removing an important frequency range and can give the impression of a "disconnected" bass.
You need a good concept for speaker + room to get precise reproduction in the 20-250Hz area. But when it works ... it's amazing to detect what's really to hear at low frequencies on recorded music.
Your experience is interesting to read about. I am wondering what mechanism might be causing this, since many acoustic instruments don't have much output down very-low (e.g. 41.2 Hz being open string on double bass), and electric/electronic instruments are amplified and played with subs anyway.
Hi, having experimented with both sealed/ported/dipole ESL systems I would say that IMO most likely reason for poor bass is either woofer with high distortion or standing waves in the room, which decay slow, add huge peaks in FR and make sound mushier.
Regards
Do you use the 31band EQ? Do a REW measurement and have a look what's really happening ...
The normal 31band is not precise enough to do room corrections - it's handy to do a quick correction in a live situation.
.... do you use the old version with big display? This is not a very famous piece of equipment in terms of sound (I owned one) ... maybe try to switch to the new version which also has parametric EQ (which I owned too - way better!).