Jim,
Looks like normal (but gross, over 100%) distortion at multiples of the fundamental, 80, 120, 160, 200, and 240 Hz.
Pretty much what you would expect from any speaker driven below Fb.
That distortion makes a speaker sound loud ;^)!
I'd expect distortion to be pretty high with the speaker you use in the SS15.
What does it look like above Fb (the low frequency cone movement minima frequency) ?
Art Welter
very interesting, thanks all.
there must be a way to get more then 15-20 amps from a wall outlet when a 12v car can provide 100s of amps !!!???
there must be a way to get more then 15-20 amps from a wall outlet when a 12v car can provide 100s of amps !!!???
why does the 'power handling' of a driver change when you put it in a horn?
is it thermal? because it requires the full power rating of the driver to make it move half the x max because of air restriction ??
or summink ?😕
Well, at least we have shed some light on the subject. We clearly are talking different things here. You're talking only about second harmonics. I think if we were using the same measurement procedures and gathering the same kind of data, the scale of the numbers would probably jive better.
I can see in your measurements that the third harmonic is nearly as loud as the second, which is not uncommon. Sometimes the third harmonic is actually louder than the second. I think for completeness sake, it might be best to mention the fact that your value is second harmonic only. You are quoting second harmonics, not third, and certainly not total.
Personally, I am interested in second and third harmonics, because those are usually the highest. When looking at tapped horns, I think it might be important to go higher, since they regularly have a lot of high frequency spikes. But of course, if you're comparing tapped horns with other configurations, it would only be fair to examine the higher harmonics of every other system under test too. Apples and apples.
I might suggest that one way to make your data less confusing and perhaps more presentable would be to list each of the harmonics you can see with their decibel (and percentage, if you wish) relationship to the fundamental. For example, instead of saying the "distortion" is 6.25%, which might lead people to think it is THD, make a list of the harmonics like this:
2H = -24dB (6%)
3H = -28dB (4%)
and so on.
By the way, did you happen to look at any of the measurements on the Home Theater site I referenced earlier? They do something like that, showing stepped sine graphs for each harmonic separately. They plot each as a percentage, with separate charts for sweeps done at 5dB increments. So instead of measuring the distorton at specific power levels, they measure at specific (fundamental) SPL levels. An interesting approach, useful, in my opinion.
Many of the subs they've measured appear to be vented boxes of a few cubic feet, tuned to run from 20Hz or 30Hz up. From the size/bandwidth, one can reasonably estimate their sensitivity. Lots of subs in the ~90dB/W/M range. That then would make their 110dB charts be roughly equivalent to a 100 watt sweep.
I can see in your measurements that the third harmonic is nearly as loud as the second, which is not uncommon. Sometimes the third harmonic is actually louder than the second. I think for completeness sake, it might be best to mention the fact that your value is second harmonic only. You are quoting second harmonics, not third, and certainly not total.
Personally, I am interested in second and third harmonics, because those are usually the highest. When looking at tapped horns, I think it might be important to go higher, since they regularly have a lot of high frequency spikes. But of course, if you're comparing tapped horns with other configurations, it would only be fair to examine the higher harmonics of every other system under test too. Apples and apples.
I might suggest that one way to make your data less confusing and perhaps more presentable would be to list each of the harmonics you can see with their decibel (and percentage, if you wish) relationship to the fundamental. For example, instead of saying the "distortion" is 6.25%, which might lead people to think it is THD, make a list of the harmonics like this:
2H = -24dB (6%)
3H = -28dB (4%)
and so on.
By the way, did you happen to look at any of the measurements on the Home Theater site I referenced earlier? They do something like that, showing stepped sine graphs for each harmonic separately. They plot each as a percentage, with separate charts for sweeps done at 5dB increments. So instead of measuring the distorton at specific power levels, they measure at specific (fundamental) SPL levels. An interesting approach, useful, in my opinion.
Many of the subs they've measured appear to be vented boxes of a few cubic feet, tuned to run from 20Hz or 30Hz up. From the size/bandwidth, one can reasonably estimate their sensitivity. Lots of subs in the ~90dB/W/M range. That then would make their 110dB charts be roughly equivalent to a 100 watt sweep.
my brain hurts even trying to read all those posts, but im crazy for quality bass.
anyone want to break down the last 2 pages into small simple bites (do-s and donts) a layman might be able to use for his next subwoofer build?
PLEASE 🙂
anyone want to break down the last 2 pages into small simple bites (do-s and donts) a layman might be able to use for his next subwoofer build?
PLEASE 🙂
Power handling doesn't change per se... but the excursion at a given frequency decreases due to the horn loading. (above 1/4 wave length of horn)
So if a driver has a 30mm xmax, and in a reflex cabinet you use all 30mm xmax within the power handling of the driver -- that's a good thing.
You put the same driver in a horn that only allows it to use 10mm xmax (hypothetical) for the same power -- that's a bad thing. you are heating up part of the coil that never does you any good.
So... balance balance balance. That's why some drivers work better in horns than others.
And your 12v question is as easy as PIE (P=I*E)
Power equal voltage * current. AKA 1200 watts = 120v * 10 amps OR 1200 watts = 12v * 100 amps
Perhaps you don't mean to be close minded, but you certainly sound like you are.
Why don't you post your distortion figures of the Lab 12 in a ported cabinet here for comparison?
As far as my figures, just to satisfy you,(and any one else doubting my figures) I did the math on the 35 Hz dual Lab 12 screen shot.
I had called it 6% distortion, adding all the harmonics makes the figure 6.25%.
The Lab 12 speaker works quite well in the right ported cabinet.
An Albuquerque company put their eight Meyers 650P up for sale after an outdoor show where four of my dual Lab 12s, powered by two crest CA-9, put out more level at 40 Hz.
That said, my four dual Lab 12 are for sale, as the Keystone cabinets loaded with BC18SW125 outperform them.
Art Welter
Attachments
Yea... Kinda what I was figuring, and why it seems that the SS15 plays 'flatter to 40hz' by ear than the hornresp would suggest. But since the main spike is 2nd order harmonic at 80hz... it sure sounds good to the ear.
I really need to do sine waves at every 10hz -- but haven't done that yet.
Paraphrased: Don't compare apples with oranges. If you have one number in inches, and another number in centimeters, you have to convert between the two to compare actual distance. Or if you measure one with a calibrated micrometer and the other with an yardstick, don't be surprised if the numbers don't quite match. And finally, if you can't take the time to add up a handful of numbers, don't be surprised when others don't take you very seriously.
No problemo:
Don’t compare measuring results one-on-one if you don’t measure with the same setup, environmental circumstances and measuring standards and/or types of loadings even if you both use the same type of drivers. The chance is bigger you end up in a jungle of differences then related results. Nevertheless, it is a very interesting read.
I'll add my experience here:
As a reader of the Ed Dell publications since 1970 - I've read everything that Bill Fitzmaurice has had published.
Like other speaker builders he has his "philosophy" and opinions about design decisions and approach to implementation. In his articles he has detailed what he considers important and what he considers acceptable compromise.
For instance: he is adamant in stating that his bass horns are to used in multiples - because of the small horn mouths.
He also feels that flat response is NOT an essential issue, relying on EQ and/or Room gain.
I built 2 of his designs based upon his published articles - a T18 and a T24.
While the T18 does fairly well with a single 8 in an 18" cube - it could not realistically replace a 15" B/R. Neither could a T24 with a 10.
On occasion Bill drops "obsolete" designs - I would not be surprised if the T30 will go the way of the T36.
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Sure.
Don't push your speaker past Xmax and the distortion will generally be less than 10% with a good quality woofer.
Horn loading and tapped horns can increase output level over bass reflex designs, but also increases distortion.
Push pull designs may reduce distortion, but I have not seen a comparison of the same drivers used in the same cabinet, so hard to say by how much.
Art Welter
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Did you bother reading post #86 ?
Why take hours of time doing math for a difference that amounts to .25% ?
If anyone wants to take that time, they are welcome to do it.
Judging by the lack of response to threads about distortion, I don't think that will happen.
By the way, I always used the highest distortion harmonic, whether second or third.
Art Welter
cool thanks 🙂
1.no surprise there.
2.I'm surprised here, I thought horns had lower distortion.
3.easy enough to test with a couple of drivers and a box.(if you have the correct equipment and knowledge.)
Jim,
The third harmonic of 40 Hz is also at 100% distortion level.
Did you happen to measure the excursion when you did that test?
I'd be very interested in seeing the SS15 distortion vs. excursion in the rest of the sub range.
If you want to do an "apples to apples" comparison to other subs Phil Lewandowski and I tested, use 5 Hz increments up to 60 Hz, then 10 Hz increments as far up as you care to go.
Art
Attachments
Jim,
The higher Xmax driver will play louder given the power.
Bass drivers have a lot of thermal mass, as long as the average power is not too high, they don't burn up.
Hornresp shows power as what a continuous sine wave would deliver, which is nothing like normal music.
Pink noise has a crest factor of 12 dB, less than most music.
If you play music with a crest factor of only 10 dB, the average power delivered to the speaker is only 100 watts when hitting 1000 watt peaks.
I'd far prefer a sub exceeding Pmax than Xmax.
Art
The amp-hour capacity from a 12V battery is necessarily large because it's used in a low voltage DC circuit.
AC power designed for distribution avoids the voltage drop in a DC system and utilizes higher transmission voltage to get more power across a grid of limited ampacity without having to resort to enormous wire.
Since speaker VC use wire around #29 they have limited ampacity, so it makes more sense to raise sensitivity.
Getting the compression chamber size correct is important on regular horns.
The OP inquired about tunable tapped horns.
Tapped horns don't use a compression chamber.
One of the benefits of horn loading is reduced distortion through the passband. This is largely because of reduced excursion. Where the distortion rises is down low, below cutoff. Excursion rises rapidly, and so therefore, so does distortion. This is not unlike the situation with bass-reflex speakers.
Tapped horns are a sort of hybrid. They act like transmission lines and bass-reflex speakers. They have strange loading though, and this tends to make a lot of high-frequency artifacts, so distortion is a little higher.
I'd say the 10% thing is a very generalized rule of thumb. It's where some people consider xmax is reached. But this is probably better seen as where the distortion rapidly rises at low to moderate power levels. At high power levels, a lot of things are happening that tend to increase distortion, even when the driver is used within its mechanical limits.
When the speaker is unloaded, it can reach xmax (and even xmech) at relatively low power levels. That's why reflex boxes and horns have such rapidly rising distortion levels below their passbands - they become unloaded.
A quick aside - xmax is usually taken to mean the place where the speaker starts rapidly becoming increasingly non-linear, and xmech is where there is physical interference. The xmax value is somewhat ambiguous in exact figure, because there is no standard of what constitutes the ending of the (relatively) linear region. Some consider it to be where the coil begins to leave the gap. Others say it's where the coil is halfway out. Others use a distortion figure, often 10%.
A second aside - the linear region (notice above, I said "relatively" linear region) is the operation within xmax. It's where cone motion is not excessive, where the speaker is most linear. But even in this region, the motion isn't perfectly linear (obviously).
A third and final aside - distortion is an indirct measure of linearity. The idealized perfect loudspeaker would move one unit forward with one unit of positive voltage and one unit backward with one unit of negative voltage. But what we actually find is that even in the linear region, a speaker will move, say 1.0001 units in the forward direction and 0.9999 units in the backward direction, with one unit positive and negative voltage, respectively. Some of this is due to suspension nonlinearities, other is because of electro-magnetic nonlinearities. Some can even come from abnormal acoustic loading.
Things that make a speaker symmetrically nonlinear create odd harmonics (third, fifth, etc.) and things that make it asymmetrically nonlinear create even harmonics (second, fourth, etc). So distortion measurements can help identify the cause. An example of asymmetrical nonlinearity is flux modulation, which causes the cone to move slightly further in one direction than the other with the same amplitude of drive voltage in both directions. Symmetrical nonlinearity is usually caused by the suspension, and it makes the speaker move slightly more or less at different excursions. So for example, if the speaker moves 1 unit of distance with 1 unit of voltage, but then 2 units of voltage only moves the cone 1.999 units of distance, if this movement is the same both forward and backward, then the nonlinearity is symmetrical.
Most drivers that are loaded in an appropriate enclosure are pretty linear at low to moderate power levels through their passbands. Excursion rises as frequency drops, so nonlinearity (distortion) will tend to increase as frequency drops too. If the box unloads down low, like a ported box or a horn, then distortion will rise rapidly under cutoff. It can easily exceed xmax, even at low power levels, so the distortion curve goes straight up. So that's where the xmax ~10% figure makes most sense - it's when the power levels are so low that through the passband, the distortion is very low. Unloaded, even at low power levels, xmax can be reached at low frequencies, so as it shoots up, when it rises from basically zero to 10%, that's a good indicator that the driver is out of its linear range. That excurison value becomes a useful figure. But again, above the unloaded frequency where xmax is reached, within the passband, at low to moderate power levels, the speaker is typically pretty linear and distortion is low.
At higher power levels, excursion rises and so does flux modulation. Even within the passband, some distortion is expected. Even a good driver on a baffle might be at 3-5% THD at 10% of its rated power. By 50%, it might be at 10% or 15%. So then at low frequencies, of course, distortion will be much higher. When it reaches xmax, if it's already at 5-10% distortion, then naturally distortion will go much higher than that. It's like a breakover point. Whatever distortion level the driver is at just below xmax, it will quickly rise above that as it goes past. Under xmax, distortion rises slowly and fairly evenly. Above xmax, it rises rapidly.
Things that reduce distortion are horn loading, shorting rings and push-pull drive. Horns reduce excursion, which tends to reduce mechanical non-linearities. Shorting rings reduce flux modulation, so decrease electro-magnetic non-linearities. Push-pull drive cancels harmonics, so can reduce both electro-mechanical and mechanical non-linearities, but only those that are asymmetrical in nature. Good horns can reduce distortion by 10dB to 15dB or more. So can push-pull drive or shorting rings, they can offer 10dB to 15dB reduction of distortion. Push-pull drive tends to work best at low frequencies. Shorting rings tend to work better at midrange frequencies up.
These technologies can be combined for even greater distortion reduction, but you can't expect 15dB from each one for a total of 45dB, if you used all three. They tend to work in different regions, so where one begins to work, the other stops. For example, shorting rings work at high frequency, push-pull works down low. If you combine them, you'll basically just have a wider range that you get that 10dB to 15dB improvement (all the way from deep bass up). If you put a driver with shorting rings on a horn, both contribute to reduce distortion, but instead of getting -15dB from each, you'll get like -20dB from the combined system. Same thing with push-pull horns. It will greatly reduce distortion at the bottom end, where the horn unloads. In the low end, the only thing preventing distortion is the push-pull drive. But higher up, in the passband, the horn is already reducing distortion, and the push-pull drive just gives a little more reduction from the combined system.
Tapped horns are a sort of hybrid. They act like transmission lines and bass-reflex speakers. They have strange loading though, and this tends to make a lot of high-frequency artifacts, so distortion is a little higher.
I'd say the 10% thing is a very generalized rule of thumb. It's where some people consider xmax is reached. But this is probably better seen as where the distortion rapidly rises at low to moderate power levels. At high power levels, a lot of things are happening that tend to increase distortion, even when the driver is used within its mechanical limits.
When the speaker is unloaded, it can reach xmax (and even xmech) at relatively low power levels. That's why reflex boxes and horns have such rapidly rising distortion levels below their passbands - they become unloaded.
A quick aside - xmax is usually taken to mean the place where the speaker starts rapidly becoming increasingly non-linear, and xmech is where there is physical interference. The xmax value is somewhat ambiguous in exact figure, because there is no standard of what constitutes the ending of the (relatively) linear region. Some consider it to be where the coil begins to leave the gap. Others say it's where the coil is halfway out. Others use a distortion figure, often 10%.
A second aside - the linear region (notice above, I said "relatively" linear region) is the operation within xmax. It's where cone motion is not excessive, where the speaker is most linear. But even in this region, the motion isn't perfectly linear (obviously).
A third and final aside - distortion is an indirct measure of linearity. The idealized perfect loudspeaker would move one unit forward with one unit of positive voltage and one unit backward with one unit of negative voltage. But what we actually find is that even in the linear region, a speaker will move, say 1.0001 units in the forward direction and 0.9999 units in the backward direction, with one unit positive and negative voltage, respectively. Some of this is due to suspension nonlinearities, other is because of electro-magnetic nonlinearities. Some can even come from abnormal acoustic loading.
Things that make a speaker symmetrically nonlinear create odd harmonics (third, fifth, etc.) and things that make it asymmetrically nonlinear create even harmonics (second, fourth, etc). So distortion measurements can help identify the cause. An example of asymmetrical nonlinearity is flux modulation, which causes the cone to move slightly further in one direction than the other with the same amplitude of drive voltage in both directions. Symmetrical nonlinearity is usually caused by the suspension, and it makes the speaker move slightly more or less at different excursions. So for example, if the speaker moves 1 unit of distance with 1 unit of voltage, but then 2 units of voltage only moves the cone 1.999 units of distance, if this movement is the same both forward and backward, then the nonlinearity is symmetrical.
Most drivers that are loaded in an appropriate enclosure are pretty linear at low to moderate power levels through their passbands. Excursion rises as frequency drops, so nonlinearity (distortion) will tend to increase as frequency drops too. If the box unloads down low, like a ported box or a horn, then distortion will rise rapidly under cutoff. It can easily exceed xmax, even at low power levels, so the distortion curve goes straight up. So that's where the xmax ~10% figure makes most sense - it's when the power levels are so low that through the passband, the distortion is very low. Unloaded, even at low power levels, xmax can be reached at low frequencies, so as it shoots up, when it rises from basically zero to 10%, that's a good indicator that the driver is out of its linear range. That excurison value becomes a useful figure. But again, above the unloaded frequency where xmax is reached, within the passband, at low to moderate power levels, the speaker is typically pretty linear and distortion is low.
At higher power levels, excursion rises and so does flux modulation. Even within the passband, some distortion is expected. Even a good driver on a baffle might be at 3-5% THD at 10% of its rated power. By 50%, it might be at 10% or 15%. So then at low frequencies, of course, distortion will be much higher. When it reaches xmax, if it's already at 5-10% distortion, then naturally distortion will go much higher than that. It's like a breakover point. Whatever distortion level the driver is at just below xmax, it will quickly rise above that as it goes past. Under xmax, distortion rises slowly and fairly evenly. Above xmax, it rises rapidly.
Things that reduce distortion are horn loading, shorting rings and push-pull drive. Horns reduce excursion, which tends to reduce mechanical non-linearities. Shorting rings reduce flux modulation, so decrease electro-magnetic non-linearities. Push-pull drive cancels harmonics, so can reduce both electro-mechanical and mechanical non-linearities, but only those that are asymmetrical in nature. Good horns can reduce distortion by 10dB to 15dB or more. So can push-pull drive or shorting rings, they can offer 10dB to 15dB reduction of distortion. Push-pull drive tends to work best at low frequencies. Shorting rings tend to work better at midrange frequencies up.
These technologies can be combined for even greater distortion reduction, but you can't expect 15dB from each one for a total of 45dB, if you used all three. They tend to work in different regions, so where one begins to work, the other stops. For example, shorting rings work at high frequency, push-pull works down low. If you combine them, you'll basically just have a wider range that you get that 10dB to 15dB improvement (all the way from deep bass up). If you put a driver with shorting rings on a horn, both contribute to reduce distortion, but instead of getting -15dB from each, you'll get like -20dB from the combined system. Same thing with push-pull horns. It will greatly reduce distortion at the bottom end, where the horn unloads. In the low end, the only thing preventing distortion is the push-pull drive. But higher up, in the passband, the horn is already reducing distortion, and the push-pull drive just gives a little more reduction from the combined system.
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What is thermal mass???
Partly true, HornResp shows continues sine wave energy without power compression (thermal and dynamic) losses.
It really depends how you define music: “live music without compressors/limiters”, “live-music with compressor limiters”, “Recorded music” as dynamic or “recorded music” as heavy processed such as dance oriented music or other popular styles.
You can’t make such statement in general. If a driver gets to its to its point below the system max excursion point the excursion is very low. If you keep on pushing the driver on this point until it reaches its Xmax, the driver would be burned way before you get there…
Also low excursion as result of high efficient loading types means less air movement in the motor which can result in dramatic rise of temperature. So it really depends on different things, different situations, different causes.
And that's all besides the story of different Xmax formulas that are used all around....
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