Agree. Cms and Kms looks very ugly, but higher in frequency excursion goes down very very quicly. So Le(x) becomes very important. I think thats why i measure up to 10dB less distortions with current drive. Thats for no box speakers.
You're referring to the cabinet?
BL is a property of the driver itself, so impossible that it will change.
You're being very cryptic?
How does that fit in the context here?
In general I deem isobaric (or compound) obsolete these days anyway, can easily be solved with active EQ.
We just got done entertaining the reasons why BL, F, le, cms, etc are important versus excursion...
First thing to come to my mind was tuning choices, to address where F is...
The second thing to come to mind was isobaric, which doubles Bl, halves cms and lowers f...halving le doubling le depending on series vs parallel
The harmonic distortion below (of a free air Td15m I think...) has a pattern up to F....cannot be changed with Eq, because its source isnt electrical
These patterns of thd look just like the patterns found in the impedance chart of a cd+horn....I think it has some kindship. These patterns in the thd are surrounding a "harmonic mode" like in a horn but different source
So anything to lower F helps...is where this is all leading...like potentially isobaric, lol yet, I think I caught that within low xmax le dominated...so if you create enough sd to keep xmax under 2mm in bass reproduction then what? I'd imagine lower excursion is the key for all areas of bandwidth
First thing to come to my mind was tuning choices, to address where F is...
The second thing to come to mind was isobaric, which doubles Bl, halves cms and lowers f...halving le doubling le depending on series vs parallel
The harmonic distortion below (of a free air Td15m I think...) has a pattern up to F....cannot be changed with Eq, because its source isnt electrical
These patterns of thd look just like the patterns found in the impedance chart of a cd+horn....I think it has some kindship. These patterns in the thd are surrounding a "harmonic mode" like in a horn but different source
So anything to lower F helps...is where this is all leading...like potentially isobaric, lol yet, I think I caught that within low xmax le dominated...so if you create enough sd to keep xmax under 2mm in bass reproduction then what? I'd imagine lower excursion is the key for all areas of bandwidth
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U can Use any Speaker 2 to 3 times above its Fs and xover min 1 to 2k below its breakup mode to minimized all the inductance n spider factors of a speaker.
I used a KEF coaxial 5in as a midbass from 250hz to 2.7khz. This hv a Fs of 65hz n breakup around 8khz. I reduced cone xmax by 5 to 10 times! This will reduce inter-modulation distortion by many times n if the upper xover is way below breakup u reduce distortion n blend the merging over to tweeter smoothly.
So if u follow this u dont need to bother with copper sleeves , spider n other magnetic abnormalities.
For Woofers go for the biggest u can afford or your wife can accept, there is no cheap substitute for displacement. Unless u hv lots of idle cash I stay away from purifi. Get an motion feedback subwoofer will be much better deal. Work well within a speaker specs n don,t bother try pushing the fundamental limits .
I used a KEF coaxial 5in as a midbass from 250hz to 2.7khz. This hv a Fs of 65hz n breakup around 8khz. I reduced cone xmax by 5 to 10 times! This will reduce inter-modulation distortion by many times n if the upper xover is way below breakup u reduce distortion n blend the merging over to tweeter smoothly.
So if u follow this u dont need to bother with copper sleeves , spider n other magnetic abnormalities.
For Woofers go for the biggest u can afford or your wife can accept, there is no cheap substitute for displacement. Unless u hv lots of idle cash I stay away from purifi. Get an motion feedback subwoofer will be much better deal. Work well within a speaker specs n don,t bother try pushing the fundamental limits .
Motion feedback is also not gonna do much for mids.
Only below 100Hz, and like amplifiers, a small Vd=Sd*xmax still won't give you a lot of SPL levels.
You can make a extremely well performing 10W amplifier that doesn't distort, but it will only give you so much power to deliver the speakers.
Not going into the debate IF that is even useful, I am purely talking about performance vs maxSPL.
For a 6 inch woofer that is the same thing, doesn't matter if your name is Purify or something else or add motion feedback.
Some 8 inches will already outperform these 6 inch woofers.
And any decent 10 inch definitely will outperform them.
So the market for these things is extremely niche.
There are two exceptions,
- When you really have to fit everything in a small box, can only use one speaker and there is absolutely no way around it.
- Or for PA/sound-reinforcement solutions, just to keep everything intact and preventing from damaging.
But I have never seen a solution that is affordable.
Seen from a production point of view, mounting the MFB sensors, tuning them etc etc etc.
It's just to much hassle at that point and you will pay more in labor costs of assembling everything (back again) than just getting a better speaker.
All assuming that these systems will work flawlessly, which in practice they never really do.
Only below 100Hz, and like amplifiers, a small Vd=Sd*xmax still won't give you a lot of SPL levels.
You can make a extremely well performing 10W amplifier that doesn't distort, but it will only give you so much power to deliver the speakers.
Not going into the debate IF that is even useful, I am purely talking about performance vs maxSPL.
For a 6 inch woofer that is the same thing, doesn't matter if your name is Purify or something else or add motion feedback.
Some 8 inches will already outperform these 6 inch woofers.
And any decent 10 inch definitely will outperform them.
So the market for these things is extremely niche.
I find that interesting, because that is what I also think of motion feedback.
There are two exceptions,
- When you really have to fit everything in a small box, can only use one speaker and there is absolutely no way around it.
- Or for PA/sound-reinforcement solutions, just to keep everything intact and preventing from damaging.
But I have never seen a solution that is affordable.
Seen from a production point of view, mounting the MFB sensors, tuning them etc etc etc.
It's just to much hassle at that point and you will pay more in labor costs of assembling everything (back again) than just getting a better speaker.
All assuming that these systems will work flawlessly, which in practice they never really do.
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Good for avoiding inductance effects - not so good for variation in B. Probably best avoided.
Has anyone experimented with current-drive?
Thinking on it, neither current nor voltage drive is useful for damping higher frequency cone resonances.
The resonance modes I have in mind are those which result from reflections from the cone's surround. Ideally, the surround would match the mechanical impedance of the cone, but where there is a mismatch (i.e. all cone drivers), matching at the driving end (i.e. at the voice-coil) would be beneficial.
I suspect dedicated midrange drivers with corrugated surrounds critically coated with damping material may be best placed to combat those resonances. Bass/midranges of course will tend to have low-damping roll surrounds - not good. I would think these types will exhibit the worst breakup effects and would benefit most from resistive damping at the voice-coil.
Perhaps it would be useful to experiment with different source resistances for midrange drivers...
The resonance modes I have in mind are those which result from reflections from the cone's surround. Ideally, the surround would match the mechanical impedance of the cone, but where there is a mismatch (i.e. all cone drivers), matching at the driving end (i.e. at the voice-coil) would be beneficial.
I suspect dedicated midrange drivers with corrugated surrounds critically coated with damping material may be best placed to combat those resonances. Bass/midranges of course will tend to have low-damping roll surrounds - not good. I would think these types will exhibit the worst breakup effects and would benefit most from resistive damping at the voice-coil.
Perhaps it would be useful to experiment with different source resistances for midrange drivers...
I think I found a trend I'd like to explore but I just wanted to specify that the thd graph above appears to be in a ported cab...I thought it was free air at first, but non the less it reminds me of a horns impedance and thd reading...where as thd is reflection of excursion...I'd think that there is a similar excursion expression nearing tuning looking at horns vs bass reflex vs TM.
Unlike the horn, you cannot see the impedance fluctuate...but yet thd is oscillating as we near tuning...I need to very if this happens in a sealed cab and free air as well.
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your perspective may be off
when Mr. Nelson experimented with current drive and full range drivers, he has seen much improvement in low fr extension
when I converted three pairs of chipmunks to current drive and used three way active crossover to run three current drive amplifiers to three drivers, I have seen best benefit in low fr extension
simple explanation is that with increasing impedance of the woofer towards low fr, you get increasing voltage from the amp
do you have actual proof current drive does not work for woofers?
That's not really my experience, also not what I see from a business point of view.
A lot of people are totally fine with a (even a couple) of small 8 inch of 10 inch subs.
Something like 8-15 liter will be enough in most cases.
Besides, good performing 6 inch subs can be already found as well as good performing 6 inch mids with a fraction of the price.
No, I think that is a little obvious, since cone resonances are not part of the piston part of a speaker anymore.
You can kind of see them like "local" resonances.
In acoustics these kind of resonances can never be tackled by changing the mass/piston part, but are properties of the material itself.
Think a bit of like the coincidence effect/region in acoustics.
Basically anything above 2 x Fs (roughly again) is not being effected by it.
That's like saying a guitar string can't be damped by applying a gentle palm pressure at the bridge end.
What I am saying is that the cone is a transmission medium, excited at the voice-coil end and terminated at the surround. To give the surround critical damping properties would obviously be beneficial. It would also be equally beneficial to terminate at the driving end, mechanically or electrically.
Since most voice-coils are rigidly attached (dual cones excepted), use of electrical damping would seem to have potential. Either using a series resistor or by modifying the driving amplifier. Sort of a half-way house between current and voltage drive.
Yes, I would imagine that Re may well be sufficiently low to damp metal cones (maybe not low enough?). Ideally, dedicated midrange drivers would have termination problems addressed mechanically. Though there are a lot more (inherently compromised) bass/midranges around than purpose-built midranges...