Poultrygeist
Lunatic Member
Close up of the amazing Bohlender Graebener planars.
thoughts on super tweeters
- Thread starter invaderzim
- Start date
Recently read that Shure did a study and 13k was all that was needed to satisfy most people. Cut off at 11k or even 12k people found it lacking. I don't know how many in the study but Shure was serious about sound in the 60s. I'm also old with hearing loss, been tested, but screaming tweeters still sound like screaming tweeters. It's still easy to tell what doesn't sound natural. Still, looking at graphs of tweeter output most drop off above 10k, especially off axis.
Poultrygeist
Lunatic Member
With some recordings I hardly hear the tweets at all. But I'm fortunate to like jazz and when the hi-hats take center stage ( and that's often ) I'm loving every brush stroke. With the dipole B&G's each cymbal shimmer hangs in mid air for what seems like an eternity ( aka decay ).
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Hawkeye83
Super Member
I was highly skeptical of super tweeters until I actually bought/heard a pair! I have these perched on top of my KEF 107's:
http://www.townshendaudio.com/supertweeters/
They operate from 6khz to 90 khz. They speculate that the eyes and even some facial bones can transfer sound "information" to the brain, beyond what the ears can hear.
Quite pricey, especially if you pay full price (I did not, I think mine were a new/demo pair, if I remember correctly). Even at a discounted or used price, still pricey! Typically $750 used to $1,500 new.
But - they did inform me that there is much more than placebo effect going on. Their effect is most obvious when turning one side on (super tweeter on) and the other side off. You get a STRONG "pull" to the side that is on. It's unmistakable. Now, if I turn them both off, I still find my 107's sound good. I turn them back on, I can tell the difference for sure...it's subtle, yet NOT. Hard to explain. I think it is the harmonic thing, and the top end sizzle thing, mostly. Things just sound more natural (and I thought they sounded plenty natural before...one of the KEF 107's strengths, IMO).
This is one of two things that I've DEFINITELY had my mind changed about in audio - super tweeters and DAC's - I used to not be a believer, but now I am!
http://www.townshendaudio.com/supertweeters/
They operate from 6khz to 90 khz. They speculate that the eyes and even some facial bones can transfer sound "information" to the brain, beyond what the ears can hear.
Quite pricey, especially if you pay full price (I did not, I think mine were a new/demo pair, if I remember correctly). Even at a discounted or used price, still pricey! Typically $750 used to $1,500 new.
But - they did inform me that there is much more than placebo effect going on. Their effect is most obvious when turning one side on (super tweeter on) and the other side off. You get a STRONG "pull" to the side that is on. It's unmistakable. Now, if I turn them both off, I still find my 107's sound good. I turn them back on, I can tell the difference for sure...it's subtle, yet NOT. Hard to explain. I think it is the harmonic thing, and the top end sizzle thing, mostly. Things just sound more natural (and I thought they sounded plenty natural before...one of the KEF 107's strengths, IMO).
This is one of two things that I've DEFINITELY had my mind changed about in audio - super tweeters and DAC's - I used to not be a believer, but now I am!
kach22i
Active Member
You didn't need an L-Pad to turn the volume down and balance them with the mains?
kach22i
Active Member
That's the way I've always used my Realistic super tweeters, otherwise they would overpower the mains and sound too bright.
AudioCarMan
Member
Apart from checking whether you can hear high frequencies above, for ex. 15.000 Herz, I would double check about the volume of the super tweeter. I wasted hours checking and testing weather the super tweeter in my Dahlquist dq-10 was working and after calling Regnar they said that the super tweeters work but they are engineered in a way that makes them produce a very soft volume. I can hear above 15.000 and 16.000 Herz, but if one is playing music and all of the drivers are loud except for the super tweeter, it is pretty much impossible to notice any difference because the other drivers will hide the sound produced by the super tweeter.
Poultrygeist
Lunatic Member
No, an L-pad is not required. With some trial and error selecting the right value cap ( 1.5uF in this case ) makes them blend. The tweets run off the same main amp and it's a simple matter of wiring the cap to it's positive terminal.
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Retrovert
Addicted Member
Yes, one would normally add an L-pad to balance.
The capacitor value merely determines the overlap between the super-tweeter and the existing tweeter. It does not balance the driver efficiencies. Many older adults cannot properly hear above 10k Hz, so the blending is less critical for them and the overall increased volume for higher frequencies may be beneficial, so the L-pad may not be necessary for that audience. Younger listeners will object to the comb artifacts formed as the two drivers, farther apart than 1/4 wavelength, interact.
But that doesn't mean an L-pad isnt' necessary. Here's why.
The capacitor forms a first-order high-pass filter and determines the filter's corner frequency, fc, i.e. the lowest frequency passed, at least subject to the 6 dB / Octave roll off. For the example you cited of 1.5 µF that is 8,841 Hz. Choosing a higher frequency crossover point merely reduces the overlap between the cone tweeter and the super-tweeter. It has nothing whatsover to do with balancing the driver efficiencies.
The tweeter should have an inductor added to create a band-pass filter, and thus prevent overlap between the tweeter (which will distort at higher frequencies) and the super-tweeter. In addition, the super-tweeter itself should have a band-pass to avoid ultrasonic oscillation, which many amplifiers have, as this can destroy a super-tweeter. A normal cone tweeter is mechanically limited, so it tends to be less vulnerable to such oscillation, but it, too, can be destroyed.
An L-pad is a attenuator, either fixed or variable, placed in parallel with a driver, in this case a tweeter, such it presents a constant impedance load, i.e. the impedance will not alter from the driver's nominal impedance, so that the crossover point will not change with attenuation. The L-pad is used to balance the tweeter's output volume to that of the other speakers. It has nothing to do with the crossover point.
As I have many times posted, the math won't lie, unlike the internet. Here's the math from one of my prior postings.
Consider the formulas:
Given:
R is Nominal Speaker Impedance (Ω)
C is Capacitance (Farad)
L is Inductance (Henry)
f is Frequency (Hertz)
L = R / (2π x f) (Henry)
f = R / (2π x L) (Hertz)
R = 2π x L x f (Ω)
C = 1 / (2π x f x R) (Farad)
f = 1 / (2π x C x R) (Hertz)
R = 1 / (2π x C x f) (Ω)
NB:
L is inductance in Henry.
To convert from Henry (H) to milliHenry (mH) multiply by 1,000.
To convert from milliHenry (mH) to Henry (H) divide by 1,000.
C is capacitance in Farad.
To convert from Farad (F)to microFarad (uF) multiply by 1,000,000.
To convert from microFarad (uF) to Farad (F) divide by 1,000,000 or multiply by 0.000001.
R is Nominal Speaker Impedance (Ω)
C is Capacitance (Farad)
L is Inductance (Henry)
f is Frequency (Hertz)
Inductor Formulas:L = R / (2π x f) (Henry)
f = R / (2π x L) (Hertz)
R = 2π x L x f (Ω)
Capacitor Formulas:C = 1 / (2π x f x R) (Farad)
f = 1 / (2π x C x R) (Hertz)
R = 1 / (2π x C x f) (Ω)
NB:
L is inductance in Henry.
To convert from Henry (H) to milliHenry (mH) multiply by 1,000.
To convert from milliHenry (mH) to Henry (H) divide by 1,000.
C is capacitance in Farad.
To convert from Farad (F)to microFarad (uF) multiply by 1,000,000.
To convert from microFarad (uF) to Farad (F) divide by 1,000,000 or multiply by 0.000001.
Nixxuz
Super Member
Very few mass market speakers run up to 40khz. Now as to whether they can be audible... My opinion is; I'd rather have a supertweeter and not need it, than need a supertweeter and not have it.
Poultrygeist
Lunatic Member
To me it's a given to select tweeters that are more efficient than the mains. I try to find a pair about 8-10 dbs higher than the mains so that when I pad them down with the correct value cap there's a good efficiency balance. That way an L-pad is not needed. It's easy to decrease the efficiency of tweeters but you can't increase their efficiency.
In this build I used compression horn tweeters which are over 100 dbs to match some fairly efficient Zenith wide band drivers. FWIW this set up is bi-amped with zero crossover on the SET powered wide band speakers with just the single filter cap on the tweeter. The woofers are powered and filtered by a plate amp.
bowtie427ss
Lunatic Member
Certainly, with regard to fundamental tones.
But, many of the harmonics of those fundamentals are within the range of hearing, and your brain will psychoacoustically use those harmonics to fill in some missing fundamental information.
Properly applied and balanced, the absence of a supertweeter should be much more immediately audible than it's presence.
Poultrygeist
Lunatic Member
Tweeters that sound good are super. 
Super Tweeter
Certainly true of most of my system experiments .. what is missing is often more noticeable than what was added ...
But I would question the logic of presuming that I can hear something above the limits of human hearing ..
If I can hear something, harmonic, or fundamental above the limit, then obviously LIMIT is the wrong word ..
And non super tweeters already extend to 45khz ..
I think that you're saying that tones above the limit produce lower harmonics that are within the range even though the tone is inaudible, and that there is therefore a value to reproduction above the range ..
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Infinity Emit eh?
That said there were a plethora of vintage speakers that employed super tweeters.
I'm using inexpensive add-on tweeters (semi super-tweeters) in the left/right of my basement system, which is used 50% for music and 50% for theater. What I really like about them is I can direct the tweeter at different angles from the main tweeters and, after some tweaking, I like what they do for imaging at least as much as the increased sparkle at the high end.
I try to "break all the rules" with my fun basement system, but never considered super tweeters for my 2-channel system (tube, no tone controls, etc.). Now, after reading this thread, I know I need them for my 2-channel system. I'm still a little confused on impedance -- does their low impedance only apply at high frequencies, or does it apply over the whole frequency spectrum? I don't like the idea of wiring something 5 ohms, or even slightly higher, in parallel with the mains.
It's a bit of a mystery to me why super tweeters don't include volume attenuators and some crossover frequency control.
I try to "break all the rules" with my fun basement system, but never considered super tweeters for my 2-channel system (tube, no tone controls, etc.). Now, after reading this thread, I know I need them for my 2-channel system. I'm still a little confused on impedance -- does their low impedance only apply at high frequencies, or does it apply over the whole frequency spectrum? I don't like the idea of wiring something 5 ohms, or even slightly higher, in parallel with the mains.
It's a bit of a mystery to me why super tweeters don't include volume attenuators and some crossover frequency control.
