I recently received a PM from another DIYAudio member (@Audio Elite) to design something that could beat the Tekton Pendragon.
I am a full-range driver sub-50 watt kind of guy, and up to this point, had never heard of Tekton or the Pendragon. Reading about it, I got interested because this thing sounds like it has some major performance for the dollar - given that it is still $2500 a pair (a lot of money for speakers anyway you look at it). Seeing the raving reviews and the 98 dB efficiency coupled with the claimed low bass extension got me interested. In case you don't know, the Tekton Pendragon is a very formidable speaker both in size and reported performance. More info can be found at the manufacturer's website tekton-designcontent2011 or in one of the many on line reviews Part II: Digging in to the Tekton Pendragon | Confessions of a Part-Time Audiophile It is a large 54 in tall tower with dual 10 in pro-audio drivers from Eminence. The 10 in drivers sit above and below three proprietary dimpled dome tweeters from Scanspeak. I have also heard that the drivers used are the B102's, but that doesn't add up as the efficiency of the B102's is only 91 dB and two drivers would only make it a 94 dB system, not 98 dB. The performance reported by the manufacturer is phenomenal: flat 98 dB response from 30 Hz to 30 kHz with only a loss of -4.5 dB at 20 Hz for 1 watt input. Although I haven't seen measurements to substantiate these claims anywhere, if anyone has knowlede of them, please let me know.
So how do you beat a design? First you have to understand what it currently does, and then you start from there. Not having a measured or predicted frequency response curve, I set about reverse engineering the Pendragon to see what the predicted performance should be. Here are the relevant physical dimensions that I could find or estimate: 12 in wide x 16 in deep x 54 in high. I will assume 0.75 in thick boards as the building material for the walls. The drivers are set at 20 in centers and one is at the mid point and other is at top. The vents are estimated to be 4 in dia x qnty 2, set at an estimated median height of 14 in from floor and spaced about 10 in apart.
From closeups of the photos, the 3-pleat accordion surround indicates that the driver is indeed the BP102 bass guitar driver rather than the Beta 10CX which has a higher 95 dB efficiency. Given this info, I first ran WinISD to determine the optimal tuning for the ports based on the calculated volume of 131 liters assuming 0.75 in thick walls. WinISD said for qnty 2 x 4 in dia vents, the length should be 9.2 inches. I then built a model of a mass loaded transmission line (MLTL) with dual drivers and dual vents. I used a MLTL model in AkAbak due to the extended length of the speaker which means that there will be some cabinet-enhanced 1/4-wave action going on.
Based on the dimensions, the drivers, the ports, the AkAbak simulation of the frequency response is shown in the first plot for 2.83 volts input measured at 1 meter with the speaker baffle located 48 in from the back wall
(as specified by manufacturer for optimal performance) shows that the frequency response is not anywhere flat. What is troubling is that the claim of 98 dB efficiency (a key selling point) doesn't seem to hold up. Given that the BP102's nominal 90.5 dB sensitivity coupled with baffle step losses produces a peak bass SPL of 92.5 dB at 50 Hz seems consistent with the driver's rating by Eminence. The SPL level falls off to 87.5 dB at 30 Hz and down to only 77 dB at 20 Hz. Within the physical bounds given by the dimensions, no amount of playing with the vent tuning will ever make this speaker produce a flat 98 dB bass shelf from 30 Hz to say 1.5 kHz assuming a cross-over somewhere above 1 kHz. If I move the speaker so that the back is only 3 inches from the wall, we get the 97.5 dB SPL but that produces a huge dip at 150 Hz due to cancellation from reflected wall sound wave. This is shown in the second plot.
Given that the predicted frequency response and SPL levels are well below manufacturer's claims, it doesn't surprise me as they do not publish their measurements. What is surprising is how owners and people who review this speaker all seem to gush how good it sounds and how loud it is. Perhaps it is loud and has a nice musicality resembling live performances because Eminence drivers are used by many professional audio applications and by touring bands? The frequency response profile is a class 'Pro Audio' shape with a slow roll-off from 50 to 60 Hz rather than a sharp drop-off at a lower frequency like some other alignments. For completeness, the third plot shows the impedance, the fourth plot shows the speaker cone displacement - note how the middle driver actually has a different behavior at the null of the top driver. The fifth plot shows the impulse response which has 3 peaks but all are less than 8 ms so it should not cause too much trouble with group delay.
So how do we go about beating this design, or as the thread title asks, "How to Slay the (pen)Dragon?" We will aim for deeper and flatter bass extension while keeping high efficiency. The first step is the swap out for a higher efficiency driver. The Eminence Beta 10CX is a perfect choice as it actually costs less and has a slightly higher Qts which will allow the MLTL to push the tuning frequency a bit lower. The next step is to adjust the cabinet volume for the new driver. In doing this, the cabinet height grew by 2 inches, and
the depth grew from 16 in to 24 in, quite a bit bigger footprint, but the acoustical result is well worth it. Then I optimized the driver placement by pulling them as close together as possible (11 in) so that they work together rather than out of phase. The position of the ports were tweaked and moved to the front. If you want to know how to initially size a MLTL cabinet, see my thread on the "Accidental MLTL Technique" here: http://www.diyaudio.com/forums/full-range/231951-accidental-mltl-technique.html
With all these optimizations, the sixth plot shows the frequency response of the newly optimized speaker at 1 meter placed 48 in from a wall (as measured from baffle), the seventh plot is the impedance, eight plot is the cone displacement and as you can see, the movement of both cones are almost identical. Last plot is the impulse response which is still good as the response is below 8 ms so there should not be too much group delay effects. I had to add a 1.7 mH coil and 4.7 ohm resistor in parallel before the drivers to reduce the HF for BSC. If you are building a XO, that can of course be part if the XO.
Looking at the SPL frequency response plot we can see that the bass extension is deeper and flatter. Also note that the CX10 is a wide band driver thus has an extended frequency response allowing cross-over to the tweeter at up to 2.5 kHz allowing the majority of vocals to be delivered by the dual 10 in cones for great phase coherence that full range drivers are known for. The high frequency stuff is handled by the single tweeter to eliminate comb-interference effects associated with 3 tweeters. The bass SPL is now about 95 dB at 40 Hz, 93 dB at 30 Hz, and 79 dB at 20 Hz for 1 watt input. There is an upper-bass hump at 250 Hz, but that is also present on the baseline Pendragon case. Stuffing adjustments in the cabinet may be able to tame this. The final design is 10.5 in wide x 22.5 in deep x 54.5 in high (internal), with drivers centered at 16 in from top and separated by 11 in. Ports are centered at 16 in from bottom and separated by 8 in. Ports are 4 in dia x 5.0 in long and front firing. Polyfill or Acoustastuff stuffing is used in the upper 2/3rds of TL and 3 in thick pad of fiberglass is placed at very bottom of cabinet to reduce HF reflections.
One still has to spec a decent 94 to 96 dB efficiency tweeter (The Vifa BC25TG15 4 ohm silk dome tweeter is perfect) with great dispersion, the right sensitivity, and a good price. Place it above the two drivers with a 1.5 to 2.5 kHz crossover and you should have your self a speaker with a flatter response, deeper bass extension, better spatial imaging since the drivers are closer together and there is only one tweeter. If you are really stuck on an MTM configuration add an extra 3 in separation between the drivers (not detrimental and performance is the same). The total cost not including cabinet is thus: $280 for qnty 4 Beta 10CX drivers, $30 for qnty 2 Vifa tweeters, probably $40 in XO parts if you DIY it, for $360 total. Cabinet cost will very depending on material but probably $120 in birch plywood should cover it.
So there you have it, the (pen)Dragon Slayer.
In case you are wondering what the maximum rms SPL is for this speaker, I calculate an xmax of 6 mm at 50 watts rms. This corresponds to an average SPL of about 112 dB at 1m. It can handle a lot more peak power above 100 Hz, so as long as you are stating away from HT style bass effects, 100 watts rms is probably OK. One advantage of using the BP102's is that they have less cone movement and thus a higher input power can be had, but at the expense of reduced sensitivity, I am not sure if it means a louder playing speaker.
In subsequent posts I will continue the optimization and analysis of this speaker, perhaps using different alignments such as a push-push bipole to get more full bass without BSC.
@Audio Elite suggested that he will use a very nice (and expensive) pleated diaphragm tweeter from Beyma called the TPL150H, which, frankly is a little overkill for this genre of speaker as it costs more than 4 of the Beta 10CX drivers put together. More info on that tweeter can be found here: http://profesional.beyma.com/ingles/pdf/TPL150H.pdf
If you have listened to a Pendragon, I would like to hear your comments and feedback. I am not trying to knock the Pendragon here (even with probably inflated ratings), it still sounds like an excellent value at $2500 a pair and can probably beat the socks off many $10k+ speakers. My point is that it can be improved by a DIY'er, as usual, for less cost than the original pieces and parts through good design and selection of components.
An externally hosted image should be here but it was not working when we last tested it.
I am a full-range driver sub-50 watt kind of guy, and up to this point, had never heard of Tekton or the Pendragon. Reading about it, I got interested because this thing sounds like it has some major performance for the dollar - given that it is still $2500 a pair (a lot of money for speakers anyway you look at it). Seeing the raving reviews and the 98 dB efficiency coupled with the claimed low bass extension got me interested. In case you don't know, the Tekton Pendragon is a very formidable speaker both in size and reported performance. More info can be found at the manufacturer's website tekton-designcontent2011 or in one of the many on line reviews Part II: Digging in to the Tekton Pendragon | Confessions of a Part-Time Audiophile It is a large 54 in tall tower with dual 10 in pro-audio drivers from Eminence. The 10 in drivers sit above and below three proprietary dimpled dome tweeters from Scanspeak. I have also heard that the drivers used are the B102's, but that doesn't add up as the efficiency of the B102's is only 91 dB and two drivers would only make it a 94 dB system, not 98 dB. The performance reported by the manufacturer is phenomenal: flat 98 dB response from 30 Hz to 30 kHz with only a loss of -4.5 dB at 20 Hz for 1 watt input. Although I haven't seen measurements to substantiate these claims anywhere, if anyone has knowlede of them, please let me know.
So how do you beat a design? First you have to understand what it currently does, and then you start from there. Not having a measured or predicted frequency response curve, I set about reverse engineering the Pendragon to see what the predicted performance should be. Here are the relevant physical dimensions that I could find or estimate: 12 in wide x 16 in deep x 54 in high. I will assume 0.75 in thick boards as the building material for the walls. The drivers are set at 20 in centers and one is at the mid point and other is at top. The vents are estimated to be 4 in dia x qnty 2, set at an estimated median height of 14 in from floor and spaced about 10 in apart.
From closeups of the photos, the 3-pleat accordion surround indicates that the driver is indeed the BP102 bass guitar driver rather than the Beta 10CX which has a higher 95 dB efficiency. Given this info, I first ran WinISD to determine the optimal tuning for the ports based on the calculated volume of 131 liters assuming 0.75 in thick walls. WinISD said for qnty 2 x 4 in dia vents, the length should be 9.2 inches. I then built a model of a mass loaded transmission line (MLTL) with dual drivers and dual vents. I used a MLTL model in AkAbak due to the extended length of the speaker which means that there will be some cabinet-enhanced 1/4-wave action going on.
Based on the dimensions, the drivers, the ports, the AkAbak simulation of the frequency response is shown in the first plot for 2.83 volts input measured at 1 meter with the speaker baffle located 48 in from the back wall
(as specified by manufacturer for optimal performance) shows that the frequency response is not anywhere flat. What is troubling is that the claim of 98 dB efficiency (a key selling point) doesn't seem to hold up. Given that the BP102's nominal 90.5 dB sensitivity coupled with baffle step losses produces a peak bass SPL of 92.5 dB at 50 Hz seems consistent with the driver's rating by Eminence. The SPL level falls off to 87.5 dB at 30 Hz and down to only 77 dB at 20 Hz. Within the physical bounds given by the dimensions, no amount of playing with the vent tuning will ever make this speaker produce a flat 98 dB bass shelf from 30 Hz to say 1.5 kHz assuming a cross-over somewhere above 1 kHz. If I move the speaker so that the back is only 3 inches from the wall, we get the 97.5 dB SPL but that produces a huge dip at 150 Hz due to cancellation from reflected wall sound wave. This is shown in the second plot.
Given that the predicted frequency response and SPL levels are well below manufacturer's claims, it doesn't surprise me as they do not publish their measurements. What is surprising is how owners and people who review this speaker all seem to gush how good it sounds and how loud it is. Perhaps it is loud and has a nice musicality resembling live performances because Eminence drivers are used by many professional audio applications and by touring bands? The frequency response profile is a class 'Pro Audio' shape with a slow roll-off from 50 to 60 Hz rather than a sharp drop-off at a lower frequency like some other alignments. For completeness, the third plot shows the impedance, the fourth plot shows the speaker cone displacement - note how the middle driver actually has a different behavior at the null of the top driver. The fifth plot shows the impulse response which has 3 peaks but all are less than 8 ms so it should not cause too much trouble with group delay.
So how do we go about beating this design, or as the thread title asks, "How to Slay the (pen)Dragon?" We will aim for deeper and flatter bass extension while keeping high efficiency. The first step is the swap out for a higher efficiency driver. The Eminence Beta 10CX is a perfect choice as it actually costs less and has a slightly higher Qts which will allow the MLTL to push the tuning frequency a bit lower. The next step is to adjust the cabinet volume for the new driver. In doing this, the cabinet height grew by 2 inches, and
the depth grew from 16 in to 24 in, quite a bit bigger footprint, but the acoustical result is well worth it. Then I optimized the driver placement by pulling them as close together as possible (11 in) so that they work together rather than out of phase. The position of the ports were tweaked and moved to the front. If you want to know how to initially size a MLTL cabinet, see my thread on the "Accidental MLTL Technique" here: http://www.diyaudio.com/forums/full-range/231951-accidental-mltl-technique.html
With all these optimizations, the sixth plot shows the frequency response of the newly optimized speaker at 1 meter placed 48 in from a wall (as measured from baffle), the seventh plot is the impedance, eight plot is the cone displacement and as you can see, the movement of both cones are almost identical. Last plot is the impulse response which is still good as the response is below 8 ms so there should not be too much group delay effects. I had to add a 1.7 mH coil and 4.7 ohm resistor in parallel before the drivers to reduce the HF for BSC. If you are building a XO, that can of course be part if the XO.
Looking at the SPL frequency response plot we can see that the bass extension is deeper and flatter. Also note that the CX10 is a wide band driver thus has an extended frequency response allowing cross-over to the tweeter at up to 2.5 kHz allowing the majority of vocals to be delivered by the dual 10 in cones for great phase coherence that full range drivers are known for. The high frequency stuff is handled by the single tweeter to eliminate comb-interference effects associated with 3 tweeters. The bass SPL is now about 95 dB at 40 Hz, 93 dB at 30 Hz, and 79 dB at 20 Hz for 1 watt input. There is an upper-bass hump at 250 Hz, but that is also present on the baseline Pendragon case. Stuffing adjustments in the cabinet may be able to tame this. The final design is 10.5 in wide x 22.5 in deep x 54.5 in high (internal), with drivers centered at 16 in from top and separated by 11 in. Ports are centered at 16 in from bottom and separated by 8 in. Ports are 4 in dia x 5.0 in long and front firing. Polyfill or Acoustastuff stuffing is used in the upper 2/3rds of TL and 3 in thick pad of fiberglass is placed at very bottom of cabinet to reduce HF reflections.
One still has to spec a decent 94 to 96 dB efficiency tweeter (The Vifa BC25TG15 4 ohm silk dome tweeter is perfect) with great dispersion, the right sensitivity, and a good price. Place it above the two drivers with a 1.5 to 2.5 kHz crossover and you should have your self a speaker with a flatter response, deeper bass extension, better spatial imaging since the drivers are closer together and there is only one tweeter. If you are really stuck on an MTM configuration add an extra 3 in separation between the drivers (not detrimental and performance is the same). The total cost not including cabinet is thus: $280 for qnty 4 Beta 10CX drivers, $30 for qnty 2 Vifa tweeters, probably $40 in XO parts if you DIY it, for $360 total. Cabinet cost will very depending on material but probably $120 in birch plywood should cover it.
So there you have it, the (pen)Dragon Slayer.
In case you are wondering what the maximum rms SPL is for this speaker, I calculate an xmax of 6 mm at 50 watts rms. This corresponds to an average SPL of about 112 dB at 1m. It can handle a lot more peak power above 100 Hz, so as long as you are stating away from HT style bass effects, 100 watts rms is probably OK. One advantage of using the BP102's is that they have less cone movement and thus a higher input power can be had, but at the expense of reduced sensitivity, I am not sure if it means a louder playing speaker.
In subsequent posts I will continue the optimization and analysis of this speaker, perhaps using different alignments such as a push-push bipole to get more full bass without BSC.
@Audio Elite suggested that he will use a very nice (and expensive) pleated diaphragm tweeter from Beyma called the TPL150H, which, frankly is a little overkill for this genre of speaker as it costs more than 4 of the Beta 10CX drivers put together. More info on that tweeter can be found here: http://profesional.beyma.com/ingles/pdf/TPL150H.pdf
If you have listened to a Pendragon, I would like to hear your comments and feedback. I am not trying to knock the Pendragon here (even with probably inflated ratings), it still sounds like an excellent value at $2500 a pair and can probably beat the socks off many $10k+ speakers. My point is that it can be improved by a DIY'er, as usual, for less cost than the original pieces and parts through good design and selection of components.
Attachments
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Pendragon-MLTL-Baseline-Freq-1m.png -
Pendragon-MLTL-Freq-1m-3inch-wall.png -
Pendragon-MLTL-Baseline-Impedance.png -
Pendragon-MLTL-Baseline-Displ.png -
Pendragon-MLTL-Baseline-Impulse.png -
Pendragon-MLTL-Optimized-Freq-1m.png -
Pendragon-MLTL-Optimized-Impedance.png -
Pendragon-MLTL-Optimized-Displ.png -
Pendragon-MLTL-Optimized-Impulse.png
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The tweeters look exactly like a SB29RDCN, definitely not a scan speak. Tekton is basically a one man show with a 2+ month wait for speakers to be delivered. Not going to have a custom driver.
Here's a thread with some semi useful measurements
Let's have some fun with measurements!!
Here's a thread with some semi useful measurements
Let's have some fun with measurements!!
Hi xrk971,
Would you have a drawing for the single CX10 version ? Or at least the dimensions.
Thanks.
Would you have a drawing for the single CX10 version ? Or at least the dimensions.
Thanks.
The dimensions are here http://www.diyaudio.com/forums/multi-way/224770-eminence-coaxial-towers-6.html#post3586283
12 in wide x 11 in deep x 45 in tall with 4 in dia x 5.25 in long vent. Driver at 11 in from top, vent 6 in from bottom.
I have got to get akabak running over here. Looking at the driver specs, your graphs and description looks like it's tuned improperly. The peak @~165 can be lowered and the port placement looks incorrect. Also the heigth looks too short. Appears to be a BR with some TL qualities. Is this a straight dual isolated line?
This is not a critism, only want to see you make the best of a good design 🙂
The TPL150 might be expensive but would make this speaker shine.
This is not a critism, only want to see you make the best of a good design 🙂
The TPL150 might be expensive but would make this speaker shine.
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Thanks for the feedback. The 45 in tall design is not what I would use for the final design, it was something I came up with for 1 driver based on the Eminence Tower thread design. It needs to be next to wall to work. The design posted in first post is design that works well 48 in from wall. What is your design for single driver wrt to length and port placement? No offense taken, glad to see someone else using Akabak. If you have suggestions on how to optimize the Pendragon Slayer, let us know. First of all, can you achieve the 98 dB claim from 30 Hz with only -4.5dB drop to 20 Hz?
Regards,
X
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Lets see?
I have heard the Pendragon and thought it was an amazing speaker for the price and punched way above its price point. The TPL150H is way above the price point of the other drivers, but I have some available and it would take this speaker to another level. Maybe I will look for an alternative compression driver, but it would have to be very good to compete with the Beyma TPL!
Does anyone know what to use here?
The Pendragon has been compared to the big Wilsons and I think that is a tall order, but I think we can get a lot closer if we do all the math and get things right.
Lets see what we can do with a little time, hard work and imagination😉
I have heard the Pendragon and thought it was an amazing speaker for the price and punched way above its price point. The TPL150H is way above the price point of the other drivers, but I have some available and it would take this speaker to another level. Maybe I will look for an alternative compression driver, but it would have to be very good to compete with the Beyma TPL!
Does anyone know what to use here?
The Pendragon has been compared to the big Wilsons and I think that is a tall order, but I think we can get a lot closer if we do all the math and get things right.
Lets see what we can do with a little time, hard work and imagination😉
Audio Elite,
If you have the Beyma's already, by all means use them! A CD horn is very different but can achieve high efficiency needed to match drivers. Would a ribbon tweeter with neodymium motor work well here?
If you have the Beyma's already, by all means use them! A CD horn is very different but can achieve high efficiency needed to match drivers. Would a ribbon tweeter with neodymium motor work well here?
I don't think we can make a comparison without knowing the original test parameters. I do think they may be showing results that could be had in a particular room with certain setup perhaps, but wouldn't hold them hard and fast to that.
Will see what I can come up with, have many things on the table today, when I get a chance surely 🙂
Read this review a long time ago and got me interested! Since then I have read dozens of reviews and each praises this speaker like no other.
Here is the link to the Stereo Mojo review with measurements.
Tekton Pendragon Loudspeaker Review
Here is the link to the Stereo Mojo review with measurements.
Tekton Pendragon Loudspeaker Review
Where is the low end roll off? It looks like this has a flat response out to 10 Hz. The output at 20 Hz is higher than the output at 30 Hz? Anyhow it is 84 dB at 20 Hz and that is -11 dB down from average of 95 dB. I think a lot of this is the room response and not speaker response.
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here's what one old spec B102 did in my fake druid pipe outdoors F10 ~42Hz relative to 100
note the effect of changing the base plate vent gap
here's the new B102 vs old in-room - Eminence sure killed some mids and any highs - do some custom speakers
use the new B102?
I'd sure like some bass for theatre organ - best quality came from K15 with Altec re-tuned per Exemplar to around 30 and boosted at Fb . My Klipschorns with room gain get to around 31 but not so pretty. I had an Eminence in a simple reflex running 6th order but it did not sound good like the Karlson - part of that may be the Altec just being better than a typical Eminence 15 in that region (?)
the old fake Druid had some power handling and decent sound - compared to a Karlson 15, its still rather toy-like.
since I have over 40 speaker cabinets, its nice to play with a small foot print
Beta 10cx changed along the way too
note the effect of changing the base plate vent gap
An externally hosted image should be here but it was not working when we last tested it.
here's the new B102 vs old in-room - Eminence sure killed some mids and any highs - do some custom speakers
use the new B102?
An externally hosted image should be here but it was not working when we last tested it.
I'd sure like some bass for theatre organ - best quality came from K15 with Altec re-tuned per Exemplar to around 30 and boosted at Fb . My Klipschorns with room gain get to around 31 but not so pretty. I had an Eminence in a simple reflex running 6th order but it did not sound good like the Karlson - part of that may be the Altec just being better than a typical Eminence 15 in that region (?)
the old fake Druid had some power handling and decent sound - compared to a Karlson 15, its still rather toy-like.
since I have over 40 speaker cabinets, its nice to play with a small foot print
Beta 10cx changed along the way too
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From a little later on in the article...
Is the following a more meaningful and perhaps somewhat predictable view of this speaker's performance?
Is the following a more meaningful and perhaps somewhat predictable view of this speaker's performance?
there's a notion or something called "Hoffman's Iron Law" 😀 - Avatar used to have BP102 or close cheap - what's the input Z look like on the Tek? - ah - here it is
http://www.stereomojo.com/Tekton Pe...view.htm/TektonPendragonLoudspeakerReview.htm
Avatar has some neo 10s but must have old out of the ferrite model - check their overstock link - http://www.avatarspeakers.com/
$80/pop isn't real bad for a BP102 shipped if a good speaker can be made
what driver is used for the front array?
http://www.stereomojo.com/Tekton Pe...view.htm/TektonPendragonLoudspeakerReview.htm
Avatar has some neo 10s but must have old out of the ferrite model - check their overstock link - http://www.avatarspeakers.com/
$80/pop isn't real bad for a BP102 shipped if a good speaker can be made
what driver is used for the front array?
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Couldn't say, not without knowing a whole lot of other things like room size, dampening coefficient of walls, measurement distance, distance from the wall, etc.
Check out REW there is a simple room simulator in it that helps with determining placement of subs. Up to 4 sub placement points can be defined and the result of the listening position you define in that simulated room.
The primary candidates are heigth, width and depth causing major peaks and nulls with the room.
The Druid looks a lot like Tekton's Lore or M Lore - another very nicely rated speaker. Tekton M-lore Speaker Review
I did not know they changed the magnet in the BP102. Is that why it is only rated as 90.5 dB efficiency now?
I did not know they changed the magnet in the BP102. Is that why it is only rated as 90.5 dB efficiency now?
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