What B&W has learned and implemented is that a minimal baffle loaded driver produces the best imaging performance possible…..and this where their systems outperform most others. Their systems that sound bright are voiced that way for their aging retail clientele who’s hearing above 10k is failing……..they KNOW who can actually afford this stuff……well accomplished GenX and Boomers with excess capital to shed…….but there’s NO denying the spatial presentation.
I’d submit the B&C 8pe21 as another option…..only better. Marketed as an 8” driver, the actual cone surface is closer to that of a 6.5” driver given the wide surround. It also plays lower and its breakup is more controlled……I’d say the treated paper cone and single reinforcing rib are responsible here. Those looking for high SPL are better served here as well with the very low QTS making the B&C driver ideal for horn loading.
The 8PE21 has an SD of 220cm² that's smack bang in 8" territory. 6.5" are around 135cm².
Most PA drivers have tons of impedance wiggles between 500Hz-2kHz indicating a plethora of resonances. The FST does not. Just with the Kevlar version breaking up at ~3.5kHz and the continuum being completely flat. 3.5kHz being way higher than you should really be going with the driver anyway.
While it is true that there are a bunch of options that have high sensitivity and, what looks to be, a smooth frequency response. I've yet to see a driver that is actually resonance free and with HD as low as the FST.
Yes there are some newer drivers from Purifi/SB/Scan that have the similar low HD but then they don't have the sensitivity.
Most PA drivers have tons of impedance wiggles between 500Hz-2kHz indicating a plethora of resonances. The FST does not. Just with the Kevlar version breaking up at ~3.5kHz and the continuum being completely flat. 3.5kHz being way higher than you should really be going with the driver anyway.
While it is true that there are a bunch of options that have high sensitivity and, what looks to be, a smooth frequency response. I've yet to see a driver that is actually resonance free and with HD as low as the FST.
Yes there are some newer drivers from Purifi/SB/Scan that have the similar low HD but then they don't have the sensitivity.
But they still have the tweeter in an extra pod. Visually nice but acoustically? I think I like the KEF approach with the coax driver and shadow flare better. The flare means the mids don't see the baffle edge.
It’s been 3 years since my OP and I’ve learnt many things, forgotten some, so sometimes I go back and update what I’ve previously written as a way to teach myself.
The minimum information what from the manufacturers datasheet one needs to look at is the amplitude response IN conjunction with the impedance response
B&C 8pe21 amplitude sweep and impedance sweep from datasheet: Looks pretty good right? 98dB/2.83 sensitivity from an 8" midrange-
The response appears reasonably smooth, but let's look at the impedance response:
Here’s a summary of what @TMM taught us re: Cone Breakup, impedance blips and Distortion in Speaker Drivers:
1. Cone Breakup
- Affects all types of cones, including paper and metal.
- Paper cones have a broader range of breakup frequencies but lower Q factors, resulting in less pronounced spikes.
2. Impedance Plot Indicator:
- The impedance plot helps predict potential distortion and performance issues.
- Doubling impedance: Check out the impedance plot in the drivers datasheet and we see the impedance has doubled from the minimum of Re=~7ohm to 14 ohms just over 2KHz. Therefore, we'd expect the response to have fallen by 6dB after 2kHz, but instead it hasn't fallen at all, therefore we can conclude the cone is breaking up by +6dB at 2kHz. If you don't understand why this is, we drive speakers with a voltage source so if the impedance has doubled the current has halved, and the pistonic movement of the cone is proportional to current through the voicecoil. Half the current is -6dB.
- A resonance-free cone would roll off at 2 kHz, but 8pe21 remains goes up to cone breakup (red arrows) and voice coil inductance interaction:
- Despite appearing to have minimal breakup, it experiences significant cone breakup.
5. Interpreting Datasheets:
- Datasheet analysis can reveal potential distortion without purchasing and testing drivers.
- Consistent impedance rise without corresponding frequency response drop indicates poorer performance.
3. Harmonic Distortion:
- Higher 5th order harmonics are due to cone breakup.
- Distortion from non-linear components (magnetics, surround, spider) is amplified by cone breakup
- Needs to be addressed by passive crossover
- Knowledge of these interpretation techniques aids in selecting high-performing drivers, without having to measure them. Without measuring, you don't know. And not all manufacturers provide comprehensive data sheets. And measuring is expensive, and unless you're willing to buy samples of everything and measure everything, one needs to start learning the datasheet.
I haven’t measured the SB Audience pure midrange, but now I understand what @5th element is saying.
In post #12 I suggest that perhaps the SB Audience pure midrange is a close equivalent:
Here's the datasheet:
High sensitivity- check
amplitude response- hmm...
impedance response- hmm...
I retract what I said 2 years ago. I was wrong. The Nero is not equivalent to the B&W FST...
Compare:
The minimum information what from the manufacturers datasheet one needs to look at is the amplitude response IN conjunction with the impedance response
B&C 8pe21 amplitude sweep and impedance sweep from datasheet: Looks pretty good right? 98dB/2.83 sensitivity from an 8" midrange-
The response appears reasonably smooth, but let's look at the impedance response:
Here’s a summary of what @TMM taught us re: Cone Breakup, impedance blips and Distortion in Speaker Drivers:
1. Cone Breakup
- Affects all types of cones, including paper and metal.
- Paper cones have a broader range of breakup frequencies but lower Q factors, resulting in less pronounced spikes.
2. Impedance Plot Indicator:
- The impedance plot helps predict potential distortion and performance issues.
- Doubling impedance: Check out the impedance plot in the drivers datasheet and we see the impedance has doubled from the minimum of Re=~7ohm to 14 ohms just over 2KHz. Therefore, we'd expect the response to have fallen by 6dB after 2kHz, but instead it hasn't fallen at all, therefore we can conclude the cone is breaking up by +6dB at 2kHz. If you don't understand why this is, we drive speakers with a voltage source so if the impedance has doubled the current has halved, and the pistonic movement of the cone is proportional to current through the voicecoil. Half the current is -6dB.
- A resonance-free cone would roll off at 2 kHz, but 8pe21 remains goes up to cone breakup (red arrows) and voice coil inductance interaction:
- Despite appearing to have minimal breakup, it experiences significant cone breakup.
5. Interpreting Datasheets:
- Datasheet analysis can reveal potential distortion without purchasing and testing drivers.
- Consistent impedance rise without corresponding frequency response drop indicates poorer performance.
3. Harmonic Distortion:
- Higher 5th order harmonics are due to cone breakup.
- Distortion from non-linear components (magnetics, surround, spider) is amplified by cone breakup
- Needs to be addressed by passive crossover
- Knowledge of these interpretation techniques aids in selecting high-performing drivers, without having to measure them. Without measuring, you don't know. And not all manufacturers provide comprehensive data sheets. And measuring is expensive, and unless you're willing to buy samples of everything and measure everything, one needs to start learning the datasheet.
I haven’t measured the SB Audience pure midrange, but now I understand what @5th element is saying.
In post #12 I suggest that perhaps the SB Audience pure midrange is a close equivalent:
Here's the datasheet:
High sensitivity- check
amplitude response- hmm...
impedance response- hmm...
I retract what I said 2 years ago. I was wrong. The Nero is not equivalent to the B&W FST...
Compare:
What you write is interesting because only last night I was at a Sarah Blasko gig which attracted a diverse range of ages of listeners (I'm retired). I overheard an older guy, probably 65-ish, discussing with another older fella the new Blasko album. They got talking about the sound of the album and while describing his fairly high-end system, he mentioned that there was a pair of B&W 801's on the end of it.
That said, his ears were so big he SHOULD have had the hearing of a bat. 😉
Critically damped drivers are nothing new……it’s been all the rage since the 80’s as transducer manufacturers began experimenting with all sorts of materials because tech had improved enough to produce diaphragms efficiently…..Focal has been making similar diaphragms from decades now.
But none of this test tone measured behavior indicates how a cone will behave with complex signals. For the sake of many here, how I wish that music behaved in this linear and predictable behavior to make all of this analysis worthwhile…..then we’d have half a dozen drivers arranged in a few different alignments with an end result of maybe 50-60 speaker systems that performed perfectly………….an eventual end to quest for the veil…….a theme so baked in to society by fantasy role play and video games to now be a cultural phenomena.
While I agree that the VST driver is nice, it’s not friendly to every recording……. no speaker is…….no Lord of the Drivers here…………there cannot be ‘only one’ in resonant systems……from the vocal cords to voice coils.
Just listen……it’s the easiest analysis a once you’ve evolved enough to remove bias.
But none of this test tone measured behavior indicates how a cone will behave with complex signals. For the sake of many here, how I wish that music behaved in this linear and predictable behavior to make all of this analysis worthwhile…..then we’d have half a dozen drivers arranged in a few different alignments with an end result of maybe 50-60 speaker systems that performed perfectly………….an eventual end to quest for the veil…….a theme so baked in to society by fantasy role play and video games to now be a cultural phenomena.
While I agree that the VST driver is nice, it’s not friendly to every recording……. no speaker is…….no Lord of the Drivers here…………there cannot be ‘only one’ in resonant systems……from the vocal cords to voice coils.
Just listen……it’s the easiest analysis a once you’ve evolved enough to remove bias.
That is your opinion. My opinion is that no set of human ears is capable to judge the cone behavior with complex signals. A lot of academic research on perceptual aspects of hearing concurs with that opinion.
@ Matt
Did you try to see if the NT1 tweeter would also fit in the 2014 FST with the double magnet? Have you measured distortion of the NT1 in the FST waveguide?
http://www.5een.co.uk/FSTNT1.htm
And bonus question: you were talking about a waveguide here: https://www.diyaudio.com/community/threads/b-w-n800-midrange.203699/post-2855381
"The wave-guide allows the FST to be used up until around 2.5khz without off axis issues and keeps the distortion hump at 3.3khz out of the picture too. With a standard 1" dome you'd be looking at an xover point of around 2khz or lower I reckon.
Here's the distortion profile for the FST + scan/wave-guide, 2nd order @ 2.5khz at what I would consider a loud listening level."
Was that a waveguide you were using on the FST or rather the WG300 waveguide used on the HDS tweeter?
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Thanks for your analysis!
May I just add:
May I just add:
and non-beaming
And of course, correct me if I'm wrong!
I have copied and overlaid your first graphs from each post, with the 2014 FST in muted colors. Of course, the FST was measured with a crossover whereas the continum was not. Not sure if the baffles were similar.
I'd argue that the 2014 FST has significantly (~ - 10 dB) lower 3rd and 5th order harmonics. Do you agree?
I'd argue that the 2014 FST has significantly (~ - 10 dB) lower 3rd and 5th order harmonics. Do you agree?
You should cross that 8PE21 at 2kHz or lower, as it starts beaming at that frequency like STV says, And the wiggles in the impendance and freuqnecy response are so minimal that it won't hurt there. I would even cross lower if possible, arround 1500Hz probally.
The B&W driver is slightly better in the breakup modes, but i'm relative sure it also starts beaming arround 1500 to 2000Hz, and crossing it that high as you do will cause a very uneven dispertion, that is very visible in many measurements that are made from their top speakers that use this driver. There is always a dip in the response arround the crossover frequency between the mid and tweeter. They should cross it way lower to avoid that.
The B&W driver is slightly better in the breakup modes, but i'm relative sure it also starts beaming arround 1500 to 2000Hz, and crossing it that high as you do will cause a very uneven dispertion, that is very visible in many measurements that are made from their top speakers that use this driver. There is always a dip in the response arround the crossover frequency between the mid and tweeter. They should cross it way lower to avoid that.
Bah, it's a PA.
At least this one was meant for live music.... One channel per string in the bass.... and check out the center channel.
Even the voice microphones were special as the Wall provided the monitoring as well.
This was a system made for the LIVE PERFORMANCE, not a Disco. A fully integrated PA with pioneering designs and thoughts.
And great music!
At least this one was meant for live music.... One channel per string in the bass.... and check out the center channel.
Even the voice microphones were special as the Wall provided the monitoring as well.
This was a system made for the LIVE PERFORMANCE, not a Disco. A fully integrated PA with pioneering designs and thoughts.
And great music!
Is the FST a bending wave transducer? It seems B&W dont really advertise it as such - rather talks a lot of bending wave behaviour in it...
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Most ‘soft’ cones are in a certain way in the region above pistonic behavior. In the cone breakup topic @krglee gives a nice history lesson on this.