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Acoustic Elegance TD18H+ in da house!

30K views 129 replies 26 participants last post by  Martycool007 
#1 ·
I just wanted to pass on initial impressions from my new Acoustic Elegance TD18H+ as it has made quite a positive impression. I admit to being a little unsure of my need to buy one given I already had a Peavey Black Widow 18 driver in action. However, once I installed the TD18H+ it was easy to work out why it was more than twice the price of the BW! Great bass makes for great music!


The bass is just so clear! I didn't think it would make such a difference as I am currently running them from 70Hz down. However, I am getting great response and serious punch from the AE driver, more so than before. Just put on a rock album and the bass drum kick is phenomenal. They are paired up with AE TD15S drivers for mid bass and the Unity Horn for the mids and up.


I obviously need to do some measurements to see if I can determine what the difference is. I am aware AVS is about measurements and not subjective opinions. I think that measure distortion' function on REW looks like something to explore. Any advice on what to measure (and how) would be greatly appreciated.


Next steps are to try the TD18H+ in a 90L sealed cabinet (like Findbuddha) and also try crossing the TD18H+ a little higher. My next project is building some cabinets for dual TD15S drivers so I can compare them directly with the single TD18H+.


Here are the T/S parameters for comparison:


Acoustic Elegance TD18H+

Fs: 29Hz

Qms:5.9

Vas: 390L

Cms: .185mm/N

Mms: 165g

Rms: 5kg/s

Xmax: 14mm

Sd: 1220scm

Qes: .23

Re: 5.6ohm

Le: .41mH

Z: 8ohm

Bl: 27Tm

Pe(cont): 1000W

Qts: .22

1W SPL: 98.2dB



Peavey Black Widow 1888HP BWX SPLi= 95.24 dB SPLo= 96.39 dB RMS=650W

Rem= 6.32 ê, Lem= 2.073 mH @1KHz

============================================================ =

Znom= 8.000 ê Sd= 0.1178 sqM Fi= 33.840 Hz Hvc= 20.7000mM

Revc= 5.790 ê BL= 23.8283 TM Fo= 36.130 Hz Hag= 7.0000 mM

Krm= 9.948 mê Vas= 230.1325 Litr Qms= 10.947 Xmx= 6.8500 mM

Kxm= 44.661 mH Cms= 116.7856 uM/N Qes= 0.385 Cmx= 2.0000mM

Mms= 166.1560 Gram Qts= 0.372 Mmd= 142.9080 Gram Pmx=1000.000


And of course some pics of the setup. Bass bin is 8 cu ft, tuned to 33Hz.


 
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#103 ·

Quote:
Originally Posted by Martycool007  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23762640


Wow, those AE woofers are super expensive, especially the 18" versions. If they are better than a 2226 then I would absolutely love to have 3 of the TD18's for mid-bass duties, unfortunately there is no way that I could ever afford those prices.
They're priced approximately for what you're getting.
 
#104 ·

Quote:
Originally Posted by Martycool007  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23762640


Wow, those AE woofers are super expensive, especially the 18" versions. If they are better than a 2226 then I would absolutely love to have 3 of the TD18's for mid-bass duties, unfortunately there is no way that I could ever afford those prices.

I don't see the 2226 as being in the same league. The better comparison is the 2265HPL Differential Drive 15" and that retails for more than the TD18. The AE drivers are the best value speakers out there in terms of function and build but not the cheapest.
 
#105 ·
The JBL driver that is most comparable to the TD18H+ is the 2246H. It is the only one that takes advantage of a shorting ring to lower inductance. It has a single small ring at the middle of the gap instead of a fully sleeved pole like the TD18H+. The JBL also has only 9mm Xmax vs 14mm Xmax of the TD18H+. The other driver people are often upgrading from is the TAD TL-1801 which has no shorting rings and only 7.5mm Xmax. The low, linear inductance and much higher Xmax makes the TD18H+ a great upgrade in applications where the 2246H or TL-1801 were previously was used. When looking at comparable drivers the TD18H+ is an amazing value and many cannot figure why the price is so low. See the prices on the two comparable drivers here:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=294-485

http://www.proaudiodesign.com/TAD-TL-1801.html
 
#106 ·

Quote:
Originally Posted by John_E_Janowitz  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23764970


The JBL driver that is most comparable to the TD18H+ is the 2246H. It is the only one that takes advantage of a shorting ring to lower inductance. It has a single small ring at the middle of the gap instead of a fully sleeved pole like the TD18H+. The JBL also has only 9mm Xmax vs 14mm Xmax of the TD18H+. The other driver people are often upgrading from is the TAD TL-1801 which has no shorting rings and only 7.5mm Xmax. The low, linear inductance and much higher Xmax makes the TD18H+ a great upgrade in applications where the 2246H or TL-1801 were previously was used. When looking at comparable drivers the TD18H+ is an amazing value and many cannot figure why the price is so low. See the prices on the two comparable drivers here:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=294-485

http://www.proaudiodesign.com/TAD-TL-1801.html

Damn right! John, I hope you can figure out what is going on with Ricci's TD18's so we can get them fully tested on DB.
 
#107 ·

Quote:
Originally Posted by John_E_Janowitz  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23764970


The JBL driver that is most comparable to the TD18H+ is the 2246H. It is the only one that takes advantage of a shorting ring to lower inductance. It has a single small ring at the middle of the gap instead of a fully sleeved pole like the TD18H+. The JBL also has only 9mm Xmax vs 14mm Xmax of the TD18H+. The other driver people are often upgrading from is the TAD TL-1801 which has no shorting rings and only 7.5mm Xmax. The low, linear inductance and much higher Xmax makes the TD18H+ a great upgrade in applications where the 2246H or TL-1801 were previously was used. When looking at comparable drivers the TD18H+ is an amazing value and many cannot figure why the price is so low. See the prices on the two comparable drivers here:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=294-485

http://www.proaudiodesign.com/TAD-TL-1801.html

I did not mean to imply that the TD18's were not worth their asking price, as they very well maybe, and from what others are saying, it seems like they are. I was just saying that there is no way that I can afford to purchase these. I truely wish that I could as I would love to see how they perform for dedicated midbass duty in their own cabinets under my Ascend Acoustics Sierra-1 book shelf speakers.


Something that I am not clear on with regards to the TD18h woofers is how do they differ in terms of sound quality in a 2-way or 3-way setup compared to using something like a Seas L18, or W16, or perhaps a Scan Speak 18W? Both the Seas and the Scan Speak will easily go down to 60hz in the right enclosure, and I believe that they will go up as high as the TD18.....so what is to be gained with a pro-woofer, such as the TD18h or TD15, over the Seas or Scan Speak? Not trying to be snotty as I am genuinely curious about this.
 
#108 ·

Quote:
Originally Posted by John_E_Janowitz  /t/1319123/acoustic-elegance-td18h-in-da-house/100_50#post_23764970


The JBL driver that is most comparable to the TD18H+ is the 2246H. It is the only one that takes advantage of a shorting ring to lower inductance. It has a single small ring at the middle of the gap instead of a fully sleeved pole like the TD18H+. The JBL also has only 9mm Xmax vs 14mm Xmax of the TD18H+. The other driver people are often upgrading from is the TAD TL-1801 which has no shorting rings and only 7.5mm Xmax. The low, linear inductance and much higher Xmax makes the TD18H+ a great upgrade in applications where the 2246H or TL-1801 were previously was used. When looking at comparable drivers the TD18H+ is an amazing value and many cannot figure why the price is so low. See the prices on the two comparable drivers here:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=294-485

http://www.proaudiodesign.com/TAD-TL-1801.html

John,


I don't think any knowledgeable individual would say that your drivers aren't worth the asking price, but we must be honest about the JBL and TAD drivers. JBL got out of the DIY business years ago and raised the prices of their drivers to an ultra premium level. The technology is solid, but they are overpriced (same as the TAD drivers). We DIY'ers are such a small market that missing a few sales from us doesn't register with them. You are filling a gap in the market, and I think that most of hope you can succeed long-term.
 
#109 ·
"Something that I am not clear on with regards to the TD18h woofers is how do they differ in terms of sound quality in a 2-way or 3-way setup compared to using something like a Seas L18, or W16, or perhaps a Scan Speak 18W? Both the Seas and the Scan Speak will easily go down to 60hz in the right enclosure, and I believe that they will go up as high as the TD18.....so what is to be gained with a pro-woofer, such as the TD18h or TD15, over the Seas or Scan Speak? Not trying to be snotty as I am genuinely curious about this."


those little guys are actually quite nice. but they are limited in what they can do, so you would need a proportionally large number of them to make a valid comparison and then the price would get ridiculous. for example, to get the same sd, you'd need about 10 seas L18 and for the same volume displaced, you'd need something like 20 of them compared to a single td18h+. not saying that it couldn't be done or that it wouldn't be great...it would.


the next closest thing in the market to the td18h+ is probably the 18sounds 18lw2400 or the b&c 18tbx100. the 2242 price is no longer competitive.
 
#110 ·

Quote:
Originally Posted by Martycool007  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23765218


Something that I am not clear on with regards to the TD18h woofers is how do they differ in terms of sound quality in a 2-way or 3-way setup compared to using something like a Seas L18, or W16, or perhaps a Scan Speak 18W?

I cant vouch for Scan Speak, but IMHO the AE drivers deliver better mid bass and midrange compared to the Seas drivers you mention. I also think AE is better than the current PHL driver I use. None of this is based of measurements as the Seas, PHL, and AE systems I have spent a good amount of time with measure relatively similar. I just found the AE drivers to deliver better mid bass detail. ....just my 2 cents
 
#111 ·
Thanks for the replys gentlemen! So basically what it comes down to when comparing the TD18's or TD15's to the Seas L18, Scan Speak 18W, or Scan Speak Revelator, is that they will have more SPL in the lower and upper mid-bass & mid-range frequencies and give you a more "kick you in the chest" type of feeling? I can't help but wonder how the actual sound quality between the two would compare.


I am in the process of doing a speaker build that was on the Zaph Audio website, and it uses some of the Scan Speak drivers. I have also been planning on building some Seos-15's when they become available to use at my fiances' apartment. I wish that I could afford to buy some of the TD15's to use in the Seos-15 build, and also some TD18h's to use in dedicated mid-bass cabinets that will be placed under each of my LCR Sieraa-1s.


Unfortunately, I can not afrord the AE drivers, so for the Seos and midbass cabinet build I plan to use the JBL2226. Anyway, good discussion guys!
 
#112 ·
The 18 Sounds LW2400 is a lot cheaper for me compared to the AE TD18H. I can actually get the next high end model up and still be slightly cheaper than AE. BUT I think the AE could still be used higher than any of the 18 Sound 18" drivers regardless of price. Although I am not intimate with all the 18 Sound drivers so I could be wrong. I still have to wait till beginning of next year for my 9600C's.
 
#114 ·

Quote:
Originally Posted by Martycool007  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23765218


Something that I am not clear on with regards to the TD18h woofers is how do they differ in terms of sound quality in a 2-way or 3-way setup compared to using something like a Seas L18, or W16, or perhaps a Scan Speak 18W? Both the Seas and the Scan Speak will easily go down to 60hz in the right enclosure, and I believe that they will go up as high as the TD18.....so what is to be gained with a pro-woofer, such as the TD18h or TD15, over the Seas or Scan Speak? Not trying to be snotty as I am genuinely curious about this.

The comparison really isn't a realistic one as you will see. As mentioned you would need a ton of the L18 to equal the output of a single TD18H+. A total of 23 of them to get the same low end displacement. If you didn't need the low end output and are just talking about upper end, the other difference is efficiency. 98db vs 87dB mean the single L18 needs over 10x the power to get to the same output as the TD18H+. A driver with 1/10 the power handling that needs 10x the power to reach the same level is not realistic. You are also comparing one driver with inductance control and one that does not have any.


A more realistic comparison if we are talking about midrange/midbass is the Seas Excel 10" or Scan Speak Revelator 10" vs a similarly sized TD10H. Both have shorting rings to bring down inductance and lower distortion. The Revelator shorting ring is much more effective due to placement, bringing down Le to .3mh while the Excel still has an Le of 1.43mH. There are other significant differences though. The motor strength of the TD10H is far more. Bl^2/Re is 64 in the TD10H compared to 16.47 in the Revelator and 17.26 in the Excel. This makes the TD10H 2-3dB more efficient so it will take less power to get loud and work in a smaller enclosure as well.


The biggest difference though is in displacement. The Excel has 7mm Xmax while the Revelator has 9mm. The TD10H however has 14mm Xmax and 20mm of suspension travel. It will take 2 of the Excel or 1.6 of the Revelators to equal the low end output of one TD10H. The TD10H has a real power handling 2-3x higher than either of those drivers as well. Then consider both of those drivers are already about $100 more.


Other drivers in the same general class as the TD10H would be the Audiotechnology Flexunits, ATC, Dynaudio, Morel Ultimate, Focal, etc which are all significantly higher, have less power handling, less Xmax, and do not have the low, linear inductance of the TD10H.
Quote:
Originally Posted by zora  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23765841


I don't think any knowledgeable individual would say that your drivers aren't worth the asking price, but we must be honest about the JBL and TAD drivers. JBL got out of the DIY business years ago and raised the prices of their drivers to an ultra premium level. The technology is solid, but they are overpriced (same as the TAD drivers). We DIY'ers are such a small market that missing a few sales from us doesn't register with them. You are filling a gap in the market, and I think that most of hope you can succeed long-term.

See the above part regarding all the other available DIY drivers out there. Whether it is these companies or the pro companies, there is one huge difference. I build the drivers and sell them direct. The other companies sell through standard distribution channels. Each step along the way of regional/national sales reps, wholesaling, warehousing, retail, etc is getting a portion of the overall sale which bumps up the cost to the end user. Not to mention the money spent on advertising. The raw parts cost in the TD18H+ before I spend a minute assembling one is already higher than the cost that these drivers are sold to the wholesalers. I would rather put the money into quality components and sell directly to the end user so they receive the benefit of a better product.

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23765914


the next closest thing in the market to the td18h+ is probably the 18sounds 18lw2400 or the b&c 18tbx100. the 2242 price is no longer competitive.

It depends on the basis of comparison if this is realistic or not. Cost wise they are less but these drivers both have only 9mm and 9.5mm Xmax vs 14mm Xmax of the TD18. The B&C has nothing in terms of impedance compensation or inductance control and has 4x the inductance. The 18sound has over 3x the inductance of the TD18H+ . While the demodulating rings help to reduce distortion some, nothing works like the full sleeve of copper over the entire pole to force the coil to act as an aircore inductor over the full travel. While many consider this to be out of band, the 18Sound has a massive breakup from the dustcap about 1.6KHz as does the B&C. If using for pure subwoofer duty, it may not be an issue. If using the driver up to 300hz in a 3way system, that places the 5th harmonic right about that point. Higher, odd order harmonics are very audible and much related to inductance. While price wise those drivers may be less, you need multiples to equal the output capability of the TD18H+. In terms of clean output they also don't compare directly.

Quote:
Originally Posted by Elill  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23765915


I cant vouch for Scan Speak, but IMHO the AE drivers deliver better mid bass and midrange compared to the Seas drivers you mention. I also think AE is better than the current PHL driver I use. None of this is based of measurements as the Seas, PHL, and AE systems I have spent a good amount of time with measure relatively similar. I just found the AE drivers to deliver better mid bass detail. ....just my 2 cents
Quote:
Originally Posted by Martycool007  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23766035


Thanks for the replys gentlemen! So basically what it comes down to when comparing the TD18's or TD15's to the Seas L18, Scan Speak 18W, or Scan Speak Revelator, is that they will have more SPL in the lower and upper mid-bass & mid-range frequencies and give you a more "kick you in the chest" type of feeling? I can't help but wonder how the actual sound quality between the two would compare.


I am in the process of doing a speaker build that was on the Zaph Audio website, and it uses some of the Scan Speak drivers. I have also been planning on building some Seos-15's when they become available to use at my fiances' apartment. I wish that I could afford to buy some of the TD15's to use in the Seos-15 build, and also some TD18h's to use in dedicated mid-bass cabinets that will be placed under each of my LCR Sieraa-1s.


Unfortunately, I can not afrord the AE drivers, so for the Seos and midbass cabinet build I plan to use the JBL2226. Anyway, good discussion guys!

There always tends to be discussion about the "sound" of a woofer. A good woofer shouldn't really have a sound to itself. Many woofers can be considered "smooth" because the top end rolls off. Or they are considered to punch or kick hard because the inductance creates a bump that exaggerates somewhere in the 50-100hz range. They are considered to cut or be bright because they breakup around 3KHz. Characteristics like that IMO are not good. A woofer should be able to most accurately reproduce what is input to it without changing the sound at all. Those characteristics are things put into the sound by the musician when it is made. You want to be able to hear things as they intended, not add the same brightness or smoothness to everything you listen to.


The real basis for comparison would be to play a given waveform through the speakers and record it. Then compare the recorded wave to the original. The woofer that has the most linearity in terms of Bl and Le will best be able to recreate this waveform. Le(x) and Le(i) distortion will physically put the VC in the wrong position which greatly distorts the waveform. You can see in this FEA analysis with and without the aluminum shorting ring on the OD of the coil how the eddy currents affect the flux near the gap. Without the shorting ring, there is a lot of flux modulation around the gap on both sides. The shorting ring removes all of it at this position.




The main issue is that this flux modulation affects the position of the VC. The following graph shows the curve with the shorting ring and without the shorting ring in red. This is not an optimized shorting ring, but you can clearly see that the coil is in a different position with and without the coil.




If you want to accurately reproduce a signal, the coil has to be in the right place at the right time. If it isn't, it is reproducing something else. Slower continual tones like sine waves are less effected. Quick transients are much more critical in terms of VC position with respect to time. When you play both at the same time is when it gets really messy. I have done the comparison with a TD woofer with and without the copper sleeve on the pole. There is a world of difference in terms of being able to reproduce a hit on a kick drum, snare hits, slap bass, or striking keys on a keyboard.


I realize that a used 2226H may be able to be picked up cheaper. I've had many people offer to sell them to me or ask me to find homes for theirs after upgrading to TD15's. A used driver you don't necessarily know how it was used though. You don't necessarily know what parts were put in to a reconed woofer either. Just be aware of those things. There are very few TD woofers that end up on the used market. If an issue does arise that is not covered under the 3yr warranty, a factory done recone here is $75 plus parts. Typically about $125 total.

Quote:
Originally Posted by chrapladm  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23766121


The 18 Sounds LW2400 is a lot cheaper for me compared to the AE TD18H. I can actually get the next high end model up and still be slightly cheaper than AE. BUT I think the AE could still be used higher than any of the 18 Sound 18" drivers regardless of price. Although I am not intimate with all the 18 Sound drivers so I could be wrong. I still have to wait till beginning of next year for my 9600C's.

The 18sound LW9601 is a fairly comparable driver because it does have the 14mm Xmax. The issue is inductance is 2.1mH and the efficiency is only 94.6dB. Also look at the response curve. Inductance causes the dip centerd around 800hz, then the duscap breakup at 1.6KHz is there.

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23766599


there is also the b&c 18sw115 floating around as a close price competitor.


not aware of any 18" drivers with as good of inductance control though.

Price wise that is a good comparison. Xmax is 14mm making it comparable too. As you mention though, inductance is almost 5x as high and without the linearity.


With any comparison you need to make sure you are comparing something similar. Between 18" drivers most all will model with similar response curves on the low end. The pro style 18's are designed most typically for 6-8cf front loaded vented enclosures. The TD18H+ and B&C 18TBX100 model nearly identically below 60hz. The 18sound, BMS, EV, JBL, RCF, etc all have similar response curves in that range so they can be compared on that basis. Power ratings are mostly similar as well. In terms of output, these are almost always excursion limited in their applications, not thermally limited. There are a lot of drivers in the lower Xmax range of 6mm - 9.5mm. These can be found cheaper, but if you need the lower end output aren't really a good option. There are only a handful of options with 14mm or Xmax, and none are less than the TD18H+.


Look at everything including Xmax, low and linear inductance, efficiency, and a smooth frequency response well upwards of the crossover point. You won't find another driver that has this combination.
 
#115 ·

Quote:
Originally Posted by John_E_Janowitz  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23767195




I realize that a used 2226H may be able to be picked up cheaper. I've had many people offer to sell them to me or ask me to find homes for theirs after upgrading to TD15's. A used driver you don't necessarily know how it was used though. You don't necessarily know what parts were put in to a reconed woofer either. Just be aware of those things. There are very few TD woofers that end up on the used market. If an issue does arise that is not covered under the 3yr warranty, a factory done recone here is $75 plus parts. Typically about $125 total.

Ouch. That was like... a direct poke.



Yes, yes, yes. I WILL get around to picking up some AE drivers but not until after I had a chance to finally enjoy these JBL's that have been sitting around for far too long.



I'll start the collection with two TD18h+'s...... next year.
 
#116 ·
Wow John, thanks for that extensive responce! I seriously wish that I could afford 3 of those TD18h's for my mid-bass cabs that I am getting ready to start on. Like I said previously, I will be using the JBL2226h drivers in a sealed enclosure that doubles as a stand for each one of my Sierra-1/RAAL bookshelf LCR's. I bet those TD18's sound nice, unfortunately I can not afford them, so I will be sticking with the JBL2226.


I really appreciate your response though, John, as I now feel like I know more about these AE woofers that were previously a mystery to me!
 
#117 ·
"The B&C has nothing in terms of impedance compensation or inductance control..."


tbx100 has demodulation rings.


"While the demodulating rings help to reduce distortion some, nothing works like the full sleeve of copper..."


i agree. would be interesting to see the difference measured though. my understanding is that most of the reduction in distortion can be achieved with demodulating rings, which is pretty much why that is what is universally done.


"the 18Sound has a massive breakup from the dustcap about 1.6KHz as does the B&C. If using for pure subwoofer duty, it may not be an issue. If using the driver up to 300hz in a 3way system, that places the 5th harmonic right about that point."


i don't understand this comment at all. if the driver is crossed at 300hz 4th order what is happening at 1.6khz is completely irrelevant. you are confusing two different concepts. maybe it was just a brain fart.


"Price wise that is a good comparison. Xmax is 14mm making it comparable too. As you mention though, inductance is almost 5x as high and without the linearity."


i didn't mention anything about the linearity of the inductance on the b&c, but now that you bring it up, it is actually quite good. and, as you know, it is the linearity in inductance that is more important to reducing distortion than the actual level of the inductance itself. changing inductance with respect to coil position or current is the source of the distortion.


the klippel on the sw115 shows an extremely linear inductance varying by only 10% or so.

 
#118 ·

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23769484


tbx100 has demodulation rings.

Sorry my mistake. The inductance is still high so i never noticed they had the rings.
Quote:
i agree. would be interesting to see the difference measured though. my understanding is that most of the reduction in distortion can be achieved with demodulating rings, which is pretty much why that is what is universally done.

A demodulation ring will help with reducing flux modulation by reducing eddy currents. The problem is that the effectiveness varies depending on coil position. It is most effective when the coil is fully next to the demodulation ring. It is more effective on the outward stroke than the inward stroke. Here are some images of the eddy currents in a motor at different positions.


At t=.012s the current to the coil is just being applied. You can already see current going into the shorting ring knowing it does help. At this position though less than half of the coil is around the pole so the eddy currents are small



At t=.028s you can see the coil fully around the pole and eddy currents are high. There are also a lot of currents seen in the demodulation ring. However, you can still see a large amount of eddy current in the pole piece. It is reduced some, but not a lot.



At t=.044s the coil is fully next to the demodulation ring. Here it is most effective with almost all of the eddy currents going into the ring. The key is to have the coil always fully next to the shorting ring like this.



Sleeving the entire pole with copper means the coil is always next to the shorting ring. There is no way for the current to get around the ring. It is continually shorted. The other thing to note is that the above lowering of inductance vs current, Le(i), does not help with inductance vs excursion, Le(x). With the steel pole in the middle, the coil is still acting as an iron core at all points. That is why inductance is high yet. As the coil begins to go upward and windings go past the tip of the pole, inductance lowers as it becomes partially air core. As it goes inward, it becomes fully iron core and Le goes up. If there is a copper cap or ring on the pole, this makes part of the coil operate as an air core and part as an iron core. As it moves back and forth past this section where it becomes air core, the inductance will change. Putting a full sleeve of copper on the pole makes it become air core at all points throughout the travel. That is why the Le(x) curves look like this on the TD woofers. You see no change in the impedance curve at rest or at 7mm.
https://sites.google.com/site/drivervault/driver-measurements/tang-band-75-1558se/ae-speakers-td12m/le-x


Drivers like the 18sound even with the AIC can lower inductance but not linearize it. If you look at the impedance curve at 10KHz, you see it does change with excursion. The change is actually more significant with the AIC on vs AIC off.
https://sites.google.com/site/drivervault/driver-measurements/tang-band-75-1558se/18-sound-12nda520/le-x
Quote:
"the 18Sound has a massive breakup from the dustcap about 1.6KHz as does the B&C. If using for pure subwoofer duty, it may not be an issue. If using the driver up to 300hz in a 3way system, that places the 5th harmonic right about that point."


i don't understand this comment at all. if the driver is crossed at 300hz 4th order what is happening at 1.6khz is completely irrelevant. you are confusing two different concepts. maybe it was just a brain fart.

This is something most people don't consider. Crossing over 4th order at 300hz will remove all fundamentals at 1.6Kz from being input to the amplifier. It does nothing to remove harmonic distortion at 1.6KHz that is caused by the driver itself. A fundamental tone at 300hz will create sound at various levels at every harmonic, 2nd -600hz, 3rd-900hz, 4th-1200hz, 5th-1500hz, 6th-1800hz, and on and on. It is proven you can have as much as 100% 2nd harmonic distortion and the human ear can barely notice it. The higher the order distortion, the less you need to be audible. You can have a 20th order harmonic as low as .01% and it is easy to hear as it is so far from the fundamental. Odd orders like 3rd and 5th are much more harsh to the human ear than the even orders.


So this 300hz tone bein input creates a 5th order harmonic at 1500hz. In the case of a TD woofer where a lot has been done to reduce flux modulation and linearize inductance, this 5th order harmonic will be low to begin with. There is also no breakup of 10dB or so due to the dustcap in that region. In a driver where there is no inductance control, this harmonic distortion will be as much as 10dB higher to begin with. Then factor in a 10dB increase in frequency due to the breakup. Not only is this a 20dB increase in magnitude of that 5th harmonic, but the dustcap creates a resonance that does not decay quickly. The 5th harmonic tone will be very high in level and continue for a long period of time. This is highly audible.
Quote:
i didn't mention anything about the linearity of the inductance on the b&c, but now that you bring it up, it is actually quite good. and, as you know, it is the linearity in inductance that is more important to reducing distortion than the actual level of the inductance itself. changing inductance with respect to coil position or current is the source of the distortion.


the klippel on the sw115 shows an extremely linear inductance varying by only 10% or so.


Yes, that does actually look quite good. Putting the alum properly placed on the pole as they did makes a big difference vs having it on the outside as many do. Inductance does still rise on the inward stroke, but a 10% variance is the best I have seen from drivers outside of our TD woofers. This is from the TD6H which has a thinner copper sleeve on the pole than the TD10-18. For all practical purposes, this driver has the worst Le linearity of every woofer we make. It varies only about 2.8%. The thicker the copper the less variance. The other TD woofers have even better Le linearity.

 
#119 ·

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23769484


i didn't mention anything about the linearity of the inductance on the b&c, but now that you bring it up, it is actually quite good. and, as you know, it is the linearity in inductance that is more important to reducing distortion than the actual level of the inductance itself. changing inductance with respect to coil position or current is the source of the distortion.


the klippel on the sw115 shows an extremely linear inductance varying by only 10% or so.


It's important to recognize what a graph does and does not show. In this case you are only looking at Le vs. VC position. The variance of Le vs. current vs VC position is another 3D variable which inductance control helps with to varying degrees for different methods. A great case to look at for this is near the Fb of a PR reflex design, a bandpass, or horn. I've measured more than a few cases where excessive Le modulation results unexpected distortion increase despite modest excursion vs. rated Xmax.
 
#120 ·
Hi John,


Is that supposed to be a sine wave?


If so, why do both traces have glitches?
Quote:
Originally Posted by John_E_Janowitz  /t/1319123/acoustic-elegance-td18h-in-da-house/100_50#post_23767195


The main issue is that this flux modulation affects the position of the VC. The following graph shows the curve with the shorting ring and without the shorting ring in red. This is not an optimized shorting ring, but you can clearly see that the coil is in a different position with and without the coil.

 
#121 ·

Quote:
Originally Posted by noah katz  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23770989


Hi John,


Is that supposed to be a sine wave?


If so, why do both traces have glitches?

I can't recall where it's posted, but I believe those images were from a paper or presentation online. I believe it was a complex signal, not a sine wave, but John will have to confirm as it's a bit ambiguous beyond there clearly being a difference without the input signal for comparison.
 
#122 ·
"So this 300hz tone bein input creates a 5th order harmonic at 1500hz. In the case of a TD woofer where a lot has been done to reduce flux modulation and linearize inductance, this 5th order harmonic will be low to begin with. There is also no breakup of 10dB or so due to the dustcap in that region. In a driver where there is no inductance control, this harmonic distortion will be as much as 10dB higher to begin with. Then factor in a 10dB increase in frequency due to the breakup. Not only is this a 20dB increase in magnitude of that 5th harmonic, but the dustcap creates a resonance that does not decay quickly. The 5th harmonic tone will be very high in level and continue for a long period of time. This is highly audible."


highly audible is what i would question. with a 4th order low pass at 300hz, spl is down about 55db by the breakup. that is low enough to not be concerned with it.


"It's important to recognize what a graph does and does not show. In this case you are only looking at Le vs. VC position. The variance of Le vs. current vs VC position is another 3D variable which inductance control helps with to varying degrees for different methods. A great case to look at for this is near the Fb of a PR reflex design, a bandpass, or horn. I've measured more than a few cases where excessive Le modulation results unexpected distortion increase despite modest excursion vs. rated Xmax."


yep, but that isn't what was mentioned so i didn't address it. :)~
 
#123 ·

Quote:
Originally Posted by noah katz  /t/1319123/acoustic-elegance-td18h-in-da-house/90#post_23770989


Hi John,


Is that supposed to be a sine wave?


If so, why do both traces have glitches?

This would actually be multiple tones occurring at the same time. This wasn't a great example because the one with shorting ring also isn't highly accurate. I wish it had another trace of the actual input signal. The point is that the flux modulation affects both time and amplitude response.
 
#124 ·

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/120#post_23771505


"So this 300hz tone bein input creates a 5th order harmonic at 1500hz. In the case of a TD woofer where a lot has been done to reduce flux modulation and linearize inductance, this 5th order harmonic will be low to begin with. There is also no breakup of 10dB or so due to the dustcap in that region. In a driver where there is no inductance control, this harmonic distortion will be as much as 10dB higher to begin with. Then factor in a 10dB increase in frequency due to the breakup. Not only is this a 20dB increase in magnitude of that 5th harmonic, but the dustcap creates a resonance that does not decay quickly. The 5th harmonic tone will be very high in level and continue for a long period of time. This is highly audible."


highly audible is what i would question. with a 4th order low pass at 300hz, spl is down about 55db by the breakup. that is low enough to not be concerned with it.

You're referring to frequency response, John was referring to distortion. The electronic low pass doesn't affect the 5th harmonic distortion product of a 300Hz input. Peaks in the response can amplify distortion products. Audibility becomes a tricky thing to figure as real use involves more than just one sine wave, but the case described would have different distortion behavior. So far as audibility, remember that the higher the harmonic, the more audible the same level of distortion is.

Quote:
"It's important to recognize what a graph does and does not show. In this case you are only looking at Le vs. VC position. The variance of Le vs. current vs VC position is another 3D variable which inductance control helps with to varying degrees for different methods. A great case to look at for this is near the Fb of a PR reflex design, a bandpass, or horn. I've measured more than a few cases where excessive Le modulation results unexpected distortion increase despite modest excursion vs. rated Xmax."


yep, but that isn't what was mentioned so i didn't address it. :)~

You answered a comment about linearity of inductance of the B&C mentioned with Le vs. (x) graph. I only pointed out that this was but one variable, and not all inclusive.
 
#125 ·

Quote:
Originally Posted by LTD02  /t/1319123/acoustic-elegance-td18h-in-da-house/120#post_23771505


highly audible is what i would question. with a 4th order low pass at 300hz, spl is down about 55db by the breakup. that is low enough to not be concerned with it.

Again, this is not at all what is in question here. The signal being input is about 55dB down because of the lowpass. The harmonics are not created by that signal that is 55dB down. They are created by the motor of the driver and are a direct result of the 300hz fundamental, not any input at 1500hz. Because they occur in the woofer after the crossover, they are not affected by it.
 
#126 ·
so you are saying the 5th harmonic is going to have whatever bump in frequency occurs at around 1500 hz or so in it?


gotcha.


so add 10db to the 5th harmonic, which tends to be down how much (20-30db below the 2nd harmonic distortion)? then add to that the masking effect in real music and you are saying that is audible?


no way. :)
 
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