Single digit frequency response is not reliable with the Behringer or any other USB soundcard so disregard anything below 10Hz. This could also be other artifacts like clothes dryer, traffic etc. The same with the high frequency above 1kHz it's unlikely to be noise transmitted through the plinth, this is based on listening to the plinth with a stethoscope there is very little microphonic noise heard.
I should have added some clarification that the area to focus on is the band between 20Hz and 500Hz. Ideally the impulse response would be a single peak at the fundamental with no other peaks. Around 40-50Hz the peaks are about the same this is most likely the fundamental impulse peak. If you push the impulse peak to the top of the audio band this would be the ideal solution just like @niffy carriage.
It would be interesting to see these responses in the time domain to see how quickly the impulse decays. unfortunately I didn't record them.
My plinth is 62mm thick Permalli with 3mm 6061 T6 aluminium plates top and bottom to increase rigidity.
I should have added some clarification that the area to focus on is the band between 20Hz and 500Hz. Ideally the impulse response would be a single peak at the fundamental with no other peaks. Around 40-50Hz the peaks are about the same this is most likely the fundamental impulse peak. If you push the impulse peak to the top of the audio band this would be the ideal solution just like @niffy carriage.
It would be interesting to see these responses in the time domain to see how quickly the impulse decays. unfortunately I didn't record them.
My plinth is 62mm thick Permalli with 3mm 6061 T6 aluminium plates top and bottom to increase rigidity.
I've just discovered that this thread has 6 more pages than when I last checked.
Look like I've got some catching up to do.
Niffy
Look like I've got some catching up to do.
Niffy
Hi Mike,
Just caught up on this thread after after missing the last half dozen pages.
The reason that higher quality arms (decks and cartridges too) have significantly lower surface noise can be a bit counterintuitive. Surely a higher resolution arm should more clearly reproduce clicks and pops, right?
The typical size of the motes of dust that contaminate a record groove is in the 3μm to 9μm range.
The average linear speed of the record past the stylus is in the region of 600,000μm/s.
Factoring the size of stylus even a large dust mote will have come and gone in less than 1/20,000th of a second.
If the stylus were to perfectly trace the dust as if it were just part of the grooves modulation it would result in a single high level impulse. This impulse would be equivalent to a half wave at 10khz. The human ear is just not sensitive enough to hear such a short impulse.
The impulse from the impact with the dust sends a shock wave into the arm and deck, like a little hammer blow. This shock will cause the arm and deck to "ring" at their various resonant frequencies.
What you hear as clicks and pops is not the dust itself but the arm and deck resonating in response to the impact with the dust.
A better arm and deck will control these resonances better and ring less.
You may have noticed that surface noise with lower quality arms tends to be at a lower frequency. This is because better arms tend to have higher bending mode resonances. With better equipment the sound of surface noise tends to be locked to the location of the speakers. With lower quality equipment the location of the noise is more spread throughout the soundstage.
The same effect is caused, to a lesser degree, by the normal modulation of the groove. As the induced resonances are in time with the music they are less obvious but still degrade the signal.
The level of surface noise audibility can be a very good indication of deck and arm quality.
You may have heard some reviewers saying that they can get a handle on the sound quality of a arm/deck combination just from the initial sound of the run-in groove. This may at first glance seem ridiculous but to a large degree you can. If any surface noise is low in level, high in frequency and locked to the location of the speakers it indicates that resonances are being well controlled.
One word of warning.
If you have an arm and deck of high quality the dust and dirt will still be in the groove, you just won't be able to hear it. It will still be causing wear to your precious stylus. Good record handling practice and cleaning are even more important. Don't assume that just because you can't hear it it isn't there.
Niffy
Niffy, great to see you back on the thread and thanks for that deep and careful explanation.
In making comparisons i have to make do with what i have owned and used myself as i don't have access to a range of equipment.
From this i believe my current set-up is working quite well, but there will always be scope for improvement and i shall continue to experiment on that and will think through the points you make as i do that!
Mike
In making comparisons i have to make do with what i have owned and used myself as i don't have access to a range of equipment.
From this i believe my current set-up is working quite well, but there will always be scope for improvement and i shall continue to experiment on that and will think through the points you make as i do that!
Mike
Mike, I have a record I almost threw away because it is so badly scratched. I ended up keeping it to assess click/pop suppression as I develop my TT/arm. It's unlistenable on a regular TT, on my highly modified SP10 it's still annoying with my pivoting arms, but the LTA reduces the surface noise to a level that makes the LP playable.
And Niffy and Warren, i believe that you both feel that the reduced resonance of your linears is as much a benefit over PTA's as is the linearity?
I guess, without the rigorous analysis i have some degree of the same result with mine.
Which leads me to another question, in considering resonances in my RTA set up, is it most likely that the resonant frequencies of each individual part are most impactful or is there a whole system resonance i should consider, The individual parts are small and stiff and by intuition i would say the resonances are well up the range, for the whole system, i have no idea, but thinking of the vibration flowing along it seems to me its likely the individual parts are the critical bits.........
Mike
I guess, without the rigorous analysis i have some degree of the same result with mine.
Which leads me to another question, in considering resonances in my RTA set up, is it most likely that the resonant frequencies of each individual part are most impactful or is there a whole system resonance i should consider, The individual parts are small and stiff and by intuition i would say the resonances are well up the range, for the whole system, i have no idea, but thinking of the vibration flowing along it seems to me its likely the individual parts are the critical bits.........
Mike
Mike as soon as you fix 2 individual items together they essentially become a system and the individual resonances will change and the system will resonate at a new frequency.
Don't confuse vibration and resonance, resonance is a buildup of vibration at the resonant frequency of the system, in essence the system becomes a mechanical amplifier, google Tacoma Narrows Bridge, this is engineering 101 on how NOT to build a bridge. Vibration is just that and does not build (amplify) with time.
Below the resonant frequency a PTA arm wand acts as a rigid beam, as soon as the energy hits the fr then the rigid beams commences to flex and bend just like the bridge. Below fr energy flows along the structure exactly the same as waves travel in air or water.
Don't confuse vibration and resonance, resonance is a buildup of vibration at the resonant frequency of the system, in essence the system becomes a mechanical amplifier, google Tacoma Narrows Bridge, this is engineering 101 on how NOT to build a bridge. Vibration is just that and does not build (amplify) with time.
Below the resonant frequency a PTA arm wand acts as a rigid beam, as soon as the energy hits the fr then the rigid beams commences to flex and bend just like the bridge. Below fr energy flows along the structure exactly the same as waves travel in air or water.
Hi Mike,
Warren's answer to the second part of your last post is excellent. This is why I designed my carriage as a single piece, all of the components it's made from acting as a whole.
As to the first part of your post,
I believe that the reduced resonance of my arm is MUCH MORE of a benefit than the reduction in lateral tracking error.
My experience and experimentation pointed to the bending modes of the armtube being the single biggest problem with vinyl playback. There was only so much that could be done to improve the resonant characteristics of an armtube, changing the material, shape, mass distribution etc whilst keeping the length the same, say 9". To improve the resonant characteristics further the length of the arm HAD to be reduced.
Making the arm very short dictated that the arm had to be linear. Reduction in lateral tracking error was just a bonus.
Another bonus, greater than reduced LTA, is that linear arms naturally have a much better balance of vertical to lateral effective masses.
As a general rule of thumb I would say that the important aspects of a tonearm in order of importance are;
Bending mode resonance,
Reflection of compression waves,
Effective mass
Azimuth
VTA
LTA
Anti-skate.
As you can see LTA is second from the bottom of the list. Anti-skate mainly presents as an LTA error so could be lumped in with it.
If you picture a stylus, especially one with an exotic profile, in a groove it is easy to see why azimuth is the most important of the alignments.
Adjusting VTA by a degree makes much more difference than the sound changes due to LTA errors across a record, which add up to much more than a degree with a conventional arm.
Of course if you get any item on the list grossly wrong it can jump up a position or two.
I won't go into compression waves in this post as that is another topic that is way too involved to do justice to in a couple of lines.
If you have ever upgraded a conventional arm you already know that LTA makes much less difference than other factors. The better arm still sounds better at its maximum tracking error than the poorer did at its minimum tracking error at the null point. It was this observation that started my whole DIY journey.
Niffy
Warren's answer to the second part of your last post is excellent. This is why I designed my carriage as a single piece, all of the components it's made from acting as a whole.
As to the first part of your post,
I believe that the reduced resonance of my arm is MUCH MORE of a benefit than the reduction in lateral tracking error.
My experience and experimentation pointed to the bending modes of the armtube being the single biggest problem with vinyl playback. There was only so much that could be done to improve the resonant characteristics of an armtube, changing the material, shape, mass distribution etc whilst keeping the length the same, say 9". To improve the resonant characteristics further the length of the arm HAD to be reduced.
Making the arm very short dictated that the arm had to be linear. Reduction in lateral tracking error was just a bonus.
Another bonus, greater than reduced LTA, is that linear arms naturally have a much better balance of vertical to lateral effective masses.
As a general rule of thumb I would say that the important aspects of a tonearm in order of importance are;
Bending mode resonance,
Reflection of compression waves,
Effective mass
Azimuth
VTA
LTA
Anti-skate.
As you can see LTA is second from the bottom of the list. Anti-skate mainly presents as an LTA error so could be lumped in with it.
If you picture a stylus, especially one with an exotic profile, in a groove it is easy to see why azimuth is the most important of the alignments.
Adjusting VTA by a degree makes much more difference than the sound changes due to LTA errors across a record, which add up to much more than a degree with a conventional arm.
Of course if you get any item on the list grossly wrong it can jump up a position or two.
I won't go into compression waves in this post as that is another topic that is way too involved to do justice to in a couple of lines.
If you have ever upgraded a conventional arm you already know that LTA makes much less difference than other factors. The better arm still sounds better at its maximum tracking error than the poorer did at its minimum tracking error at the null point. It was this observation that started my whole DIY journey.
Niffy
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This is a very good point. When I modified my Technics EPA-100 it bettered the linear tracker, UNTIL I fixed some of the issues with the carriage, this was mainly COG being too high and the wheels were not perfectly concentric and orthogonal to the thrust line. The next upgrade to the LTA was a new billet aluminium rail with an 8mm pocket for the 2x carbide rods and a new carriage with lower COG, the LTA now smashes the modified EPA-100.
Hi Warren,
A successful upgrade is always good news.
I was kinda talking about upgrading from a conventional pivoted arm to another conventional pivoted arm.
Many years ago I upgraded my tonearm. I upgraded from what would be in today's money around a £250 arm to a £1750 arm. Both were 9" and had similar geometries and effective masses. The £250 arm had been rewired with probably better wire than the £1750 arm. The smoothness of movement of the bearings seemed the same. The £1750 arm absolutely trounced the cheaper arm in every way possible. The variation in sound quality as either arm tracked across the record was very slight compared to the huge difference between the two. This told me that something much more significant than LTA errors was effecting the difference between the two arms.
I preformed a little experiment to investigate this further.
I aligned my cartridge in the £250 arm so that it had a null point around 10-15mm in from the outside of the record. This would mean that the cartridge would be close to perfectly aligned for the first track of a record.
I then swapped arms but this time purposefully misaligned the cartridge by 2.5-3° at the same 10-15mm from the edge of the record, much greater than the tracking error due to the geometry of the arm would normally be.
The £1750 arm still sounded much better.
The main difference that I could ascertain was that the first bending mode of the more expensive arm was about an octave higher and better controlled.
Many years later, a degree in composites engineering and a lot more experimentation have resulted in my current arm.
Niffy
A successful upgrade is always good news.
I was kinda talking about upgrading from a conventional pivoted arm to another conventional pivoted arm.
Many years ago I upgraded my tonearm. I upgraded from what would be in today's money around a £250 arm to a £1750 arm. Both were 9" and had similar geometries and effective masses. The £250 arm had been rewired with probably better wire than the £1750 arm. The smoothness of movement of the bearings seemed the same. The £1750 arm absolutely trounced the cheaper arm in every way possible. The variation in sound quality as either arm tracked across the record was very slight compared to the huge difference between the two. This told me that something much more significant than LTA errors was effecting the difference between the two arms.
I preformed a little experiment to investigate this further.
I aligned my cartridge in the £250 arm so that it had a null point around 10-15mm in from the outside of the record. This would mean that the cartridge would be close to perfectly aligned for the first track of a record.
I then swapped arms but this time purposefully misaligned the cartridge by 2.5-3° at the same 10-15mm from the edge of the record, much greater than the tracking error due to the geometry of the arm would normally be.
The £1750 arm still sounded much better.
The main difference that I could ascertain was that the first bending mode of the more expensive arm was about an octave higher and better controlled.
Many years later, a degree in composites engineering and a lot more experimentation have resulted in my current arm.
Niffy
I guess my point was that when I removed the resonant peak of the decoupled counter weight from the EPA-100 it bettered the LTA, because the LTA had stability issues due to the high COG, so just having a short carriage is no guarantee of ultra high performance. The high COG was caused by the smallest size rings I could buy being 18mm OD. To lower COG I split the carriage top to raise the wheel pivot point. So the cartridge mounting surface is 4mm lower, the COG is still slightly above the pivot but not by much. I know this because VTF drops 0.1g as the carriage pivots up 5mm.
I was approached by a guy recently who is a toolmaker with access to highend CNC. He has asked me to make him an inverted bearing Technics SP10 and LTA the like mine. He is doing the CAD and will CNC the parts. One set of carbide rings I have, thickness varies by 0.03mm and OD by 0.08mm these are the worst. To get the rings more uniform he is going to grind new carbide rings at 16mm OD so we should end up with far better concentricity hence lower rolling resistance. I'll post pics once we have it built.
I was approached by a guy recently who is a toolmaker with access to highend CNC. He has asked me to make him an inverted bearing Technics SP10 and LTA the like mine. He is doing the CAD and will CNC the parts. One set of carbide rings I have, thickness varies by 0.03mm and OD by 0.08mm these are the worst. To get the rings more uniform he is going to grind new carbide rings at 16mm OD so we should end up with far better concentricity hence lower rolling resistance. I'll post pics once we have it built.
Getting everything balanced within the design is of paramount importance. Get one thing grossly out and the design will fail.
When designing my carriage I set up a very involved spreadsheet that operated similar to finite element analysis.
It calculated the first bending mode both vertically and horizontally. It also calculated the lateral and vertical effective masses, the tracking force, the height of the centre of mass and the expected variation in tracking force. It also calculated how much warp wow the design would likely suffer.
Good luck with the build.
Having a someone with both the skills and equipment to help manufacture precise components is going to be a biggy.
When designing my carriage I set up a very involved spreadsheet that operated similar to finite element analysis.
It calculated the first bending mode both vertically and horizontally. It also calculated the lateral and vertical effective masses, the tracking force, the height of the centre of mass and the expected variation in tracking force. It also calculated how much warp wow the design would likely suffer.
Good luck with the build.
Having a someone with both the skills and equipment to help manufacture precise components is going to be a biggy.
Thanks Niffy and Warren,
I shall consider all the points you've made and no doubt reach out to tap your brains further in the near future!
Best
Mike
I shall consider all the points you've made and no doubt reach out to tap your brains further in the near future!
Best
Mike
Morning Niffy, may i ask you kindly to expand your thoughts, optimums and solutions on two of these areas please, being reflection of compression waves and Effective mass?
Many thanks in advance
Mike
Hi Mike,
I'll have a go at explaining these two areas over the next couple of days. It might take a couple of posts to do the topic justice.
I have gone into effective mass in this thread in quite some detail a couple of times. Unfortunately this thread has grown somewhat and it might be rather difficult to find.
I have previously attempted to write up my thoughts on compression waves. Unfortunately either my phone or the diyaudio site glitched and lost the entire post. Hopefully I'll have more luck this time.
I'll have a go at explaining these two areas over the next couple of days. It might take a couple of posts to do the topic justice.
I have gone into effective mass in this thread in quite some detail a couple of times. Unfortunately this thread has grown somewhat and it might be rather difficult to find.
I have previously attempted to write up my thoughts on compression waves. Unfortunately either my phone or the diyaudio site glitched and lost the entire post. Hopefully I'll have more luck this time.
Many thanks Niffy, i look forward to that, I have never been good at deep analysis, i try hard to understand and work somewhat intuitively and empirically, but having been involved in areas where failure is not an option, if it matters, i always wish to know enough to be sure, often with others in a team to lean on, so i am certain your insights will be valuable to me, and i expect to many others!! - if read with an open mind...........
M
M
For long posts I write it up in Word and copy it across because I've had the same thing happen to me.
I'd like to discuss the mechanisms by which vibrational energy is transmitted from the stylus/groove interface into the body of the cartridge and by extension the arm. I'm going to say a lot of stuff that you already know. I'm putting it in to help paint the picture.
The stylus moves in what is basically a linear fashion to follow the modulation of the groove. It's movement is constrained to the vertical and horizontal plane. The vertical movement is inclined to about 23°, the tracking angle. This angle is not important to this discussion. Technically the stylus travels in an arc due to the pivoting of the cantilever. This angle, even at its maximum, is very small at less than 1/4 of a degree. So there is virtually no rotation of the stylus.
The cantilever is compliantly attached to the cartridge. The compliance is set so that it is stiff enough to allow the arm to be moved at very low frequencies, such as those produced by record warps and eccentricity, and flexible enough to allow free movement at higher, audio band, frequencies.
In combination the mass of the arm and the compliance of the cartridge will have a resonant frequency. Well below this frequency the arm will move with the stylus. Well above this frequency the arm/cartridge body will remain roughly stationery as the stylus moves back and forth. It is this relative movement that powers the output of the cartridge. The resonance is normally set to be between 8-12hz so that it is above the frequency of warps (up to ~5hz) and below the audio band, starting 20hz. Ideally we want the cartridge body to remain absolutely stationary relative to the record surface as any movement will be output as if it were groove modulation.
Unfortunately the cartridge does move relative to the movement of the stylus. The amount of this movement decrease as the frequency of movement increases. The amount of cartridge body movement decreases by 12dB/octave. At 20hz the cartridge body's movement is typically only 10dB below that of the stylus. This means that the cartridge body is moving more than a quarter the amount the stylus is. By the time we get to 100hz the relative motion is down to -40dB. This chart shows the movement of the cartridge body relative to that of the stylus, the frequency response.
The blue trace shows the typical response of an arm cartridge tuned to 10hz. The orange trace shows the response of an arm tuned to 5hz. As you can see the resonant peek now sits in the frequency range of where warps occur. This could cause serious tracking problems. You will also notice that the orange trace is 12dB lower in level. This would result in the cartridge body moving only a quarter as much as in the case of the arm tuned to 10hz. For a typical cartridge with a compliance of 16μm/mN the effective mass would need to be 16g to achieve a resonance of 10hz. To a achieve a resonance of 5hz the effective mass would need to be increased fourfold to 64g.
Warps only occur in the vertical plane so the vertical effective mass wants to be kept in the normal 8-12hz range. Laterally we only have eccentricity which is at a much lower frequency, 0.55hz for 33rpm. The lateral resonant frequency can be set much lower without fear of being excited.
Below around 120hz records are only cut laterally, there is no vertical modulation. This is to prevent the stylus from being flung from the groove.
The vertical and lateral compliance of most cartridges differ by about 25%.
As the frequency range and compliance are completely different vertically and laterally there is absolutely no reason to make the vertical and lateral effective masses the same. By making the lateral mass much higher the response in the bass is massively improved.
By the time the frequency is up to around 100hz the relative movement of the cartridge body, both vertically and laterally, is very small.
These two plots show the actual amount the cartridge body moves relative to the stylus. At 20hz there is a huge difference between the 10hz and 5hz tuned arms. At 100hz, before there is any stereo information, the difference is very small.
An advantage of a linear arm is that it naturally has a higher lateral effective mass.
If this was the only mechanism that transmitted vibration into the arm there would be very little high frequencies transmitted.
If we stick a mechanics stethoscope against the base of the arm we hear that the majority of the sound is high frequency, much higher than 100hz.
This means that the majority of the vibrational energy transmitted to the arm is via a different mechanism. I'll aim to cover this in my next post.
Niffy
The stylus moves in what is basically a linear fashion to follow the modulation of the groove. It's movement is constrained to the vertical and horizontal plane. The vertical movement is inclined to about 23°, the tracking angle. This angle is not important to this discussion. Technically the stylus travels in an arc due to the pivoting of the cantilever. This angle, even at its maximum, is very small at less than 1/4 of a degree. So there is virtually no rotation of the stylus.
The cantilever is compliantly attached to the cartridge. The compliance is set so that it is stiff enough to allow the arm to be moved at very low frequencies, such as those produced by record warps and eccentricity, and flexible enough to allow free movement at higher, audio band, frequencies.
In combination the mass of the arm and the compliance of the cartridge will have a resonant frequency. Well below this frequency the arm will move with the stylus. Well above this frequency the arm/cartridge body will remain roughly stationery as the stylus moves back and forth. It is this relative movement that powers the output of the cartridge. The resonance is normally set to be between 8-12hz so that it is above the frequency of warps (up to ~5hz) and below the audio band, starting 20hz. Ideally we want the cartridge body to remain absolutely stationary relative to the record surface as any movement will be output as if it were groove modulation.
Unfortunately the cartridge does move relative to the movement of the stylus. The amount of this movement decrease as the frequency of movement increases. The amount of cartridge body movement decreases by 12dB/octave. At 20hz the cartridge body's movement is typically only 10dB below that of the stylus. This means that the cartridge body is moving more than a quarter the amount the stylus is. By the time we get to 100hz the relative motion is down to -40dB. This chart shows the movement of the cartridge body relative to that of the stylus, the frequency response.
The blue trace shows the typical response of an arm cartridge tuned to 10hz. The orange trace shows the response of an arm tuned to 5hz. As you can see the resonant peek now sits in the frequency range of where warps occur. This could cause serious tracking problems. You will also notice that the orange trace is 12dB lower in level. This would result in the cartridge body moving only a quarter as much as in the case of the arm tuned to 10hz. For a typical cartridge with a compliance of 16μm/mN the effective mass would need to be 16g to achieve a resonance of 10hz. To a achieve a resonance of 5hz the effective mass would need to be increased fourfold to 64g.
Warps only occur in the vertical plane so the vertical effective mass wants to be kept in the normal 8-12hz range. Laterally we only have eccentricity which is at a much lower frequency, 0.55hz for 33rpm. The lateral resonant frequency can be set much lower without fear of being excited.
Below around 120hz records are only cut laterally, there is no vertical modulation. This is to prevent the stylus from being flung from the groove.
The vertical and lateral compliance of most cartridges differ by about 25%.
As the frequency range and compliance are completely different vertically and laterally there is absolutely no reason to make the vertical and lateral effective masses the same. By making the lateral mass much higher the response in the bass is massively improved.
By the time the frequency is up to around 100hz the relative movement of the cartridge body, both vertically and laterally, is very small.
These two plots show the actual amount the cartridge body moves relative to the stylus. At 20hz there is a huge difference between the 10hz and 5hz tuned arms. At 100hz, before there is any stereo information, the difference is very small.
An advantage of a linear arm is that it naturally has a higher lateral effective mass.
If this was the only mechanism that transmitted vibration into the arm there would be very little high frequencies transmitted.
If we stick a mechanics stethoscope against the base of the arm we hear that the majority of the sound is high frequency, much higher than 100hz.
This means that the majority of the vibrational energy transmitted to the arm is via a different mechanism. I'll aim to cover this in my next post.
Niffy
Fantastic thanks Niffy, i have given it a first read, need to read several times. Looking forward also to the next post!
Best
Mike
Best
Mike
I forgot to address a common audio myth about the high lateral mass of linear arms. It is said by many that the high mass causes the stylus to be slammed from one groove wall to the other causing massive tracking errors.
If you take a conventional pivoted arm and play a seriously eccentric record were the cartridge dances back and forth by 1mm the cantilever will be deflected by a maximum of 0.02°.
If you play the same record on an arm with a lateral effective mass four times as great the maximum deflection of the cantilever will be 0.08°.
Although the cantilever deflection is higher it is still so low as to be inaudible. The benefit of the cartridge body being held more stably at low frequencies is very audible.
Of course if the record is well centred there will be no back and forth motion and therefore no cantilever deflection on either type of arm. The benefit of lower cartridge movement will remain.
Niffy
If you take a conventional pivoted arm and play a seriously eccentric record were the cartridge dances back and forth by 1mm the cantilever will be deflected by a maximum of 0.02°.
If you play the same record on an arm with a lateral effective mass four times as great the maximum deflection of the cantilever will be 0.08°.
Although the cantilever deflection is higher it is still so low as to be inaudible. The benefit of the cartridge body being held more stably at low frequencies is very audible.
Of course if the record is well centred there will be no back and forth motion and therefore no cantilever deflection on either type of arm. The benefit of lower cartridge movement will remain.
Niffy