Hi to all! 
I wonder is it better to have an 50W/8 Ohm amplifier working with 8 Ohm and 90 dB/W loudspeaker or 500W/8 Ohm amplifier working with 80 Ohm and 90 dB/W loudspeaker?
In other words would it be of any advantage to have a more powerful amplifier and a higher impedance loudspeaker?
higher impedance means proportionally less current and less distortion. Or it is not? I am not sure
such a higher impedance and and at the same time high efficiency loudspeaker can be build as an array of ten 8 Ohm speakers wired in series
but an array of 10 drivers per side means quite a lot of money for quality speakers and a lot of woodworking in any case
so – is it worth trying? what do You think?
best,
graaf
I wonder is it better to have an 50W/8 Ohm amplifier working with 8 Ohm and 90 dB/W loudspeaker or 500W/8 Ohm amplifier working with 80 Ohm and 90 dB/W loudspeaker?
In other words would it be of any advantage to have a more powerful amplifier and a higher impedance loudspeaker?
higher impedance means proportionally less current and less distortion. Or it is not? I am not sure
such a higher impedance and and at the same time high efficiency loudspeaker can be build as an array of ten 8 Ohm speakers wired in series
but an array of 10 drivers per side means quite a lot of money for quality speakers and a lot of woodworking in any case
so – is it worth trying? what do You think?
best,
graaf
Hi,
Whilst a 500w / 8ohm amplifier is a 50W / 80 ohm amplifier the obvious
question is why ? You want utter overkill current capability ? Whilst at
full power 500W/8R vs. 50W/80R distortion for the latter will be lower,
ignoring noise there would be not much difference for 50W/8R case.
It will be "better". Just not very sensible. Poor way to get 50W.
/sreten.
Whilst a 500w / 8ohm amplifier is a 50W / 80 ohm amplifier the obvious
question is why ? You want utter overkill current capability ? Whilst at
full power 500W/8R vs. 50W/80R distortion for the latter will be lower,
ignoring noise there would be not much difference for 50W/8R case.
It will be "better". Just not very sensible. Poor way to get 50W.
/sreten.
sreten said:
I want better sound, this is why
audiophiles are told that less distortion means better sound
is it not true?
sreten said:
You mean that those lower distortions would make not much difference audibly?
They wouldn't be significantly lower?
sreten said:
in fact I would like to get the cleanest first Watt
You mean "better" = not better that is not "truly better"?
why not? difference in distortion levels would be insignificant?
best,
graaf
sreten said:
"not much difference" - but how much?
what exactly does it mean "not much"?
we are talking about 10x difference in nominal impedance
a 4x difference (2-8 Ohm) in case of typical solid state amplifier can result in 3x difference in THD+N % or even more
is it significant? can it be?
is it mainly a change in "N" and not in harmonic distortions?
best,
graaf
I do not think that series wiring drivers, especially
fullrange drivers, is a good strategy.
Drivers - even of same type - differ, because
there are tolerances.
Drivers are not precision mechanics like clockwork ...
Resonance frequency differs, Q differs, cone breakup
patterns differ.
This is why impedance vs. frequency differs.
By series wiring you loose averaging over the differing drivers.
At each frequency the driver with highest impedance has
the greatest voltage across the voice coil.
Which means, the driver with highest cone velocity gets
the most power.
If you choose 4 same type drivers randomly and compare
the impedance curves series vs. parallel, the curve for parallel
wiring is much smoother even when using logarithmic scaling.
Concerning stability of (some) amps your idea is worth thinking.
But concerning the behaviour of the speaker array itself, series
wiring is no good idea to me ...
Kind regards
fullrange drivers, is a good strategy.
Drivers - even of same type - differ, because
there are tolerances.
Drivers are not precision mechanics like clockwork ...
Resonance frequency differs, Q differs, cone breakup
patterns differ.
This is why impedance vs. frequency differs.
By series wiring you loose averaging over the differing drivers.
At each frequency the driver with highest impedance has
the greatest voltage across the voice coil.
Which means, the driver with highest cone velocity gets
the most power.
If you choose 4 same type drivers randomly and compare
the impedance curves series vs. parallel, the curve for parallel
wiring is much smoother even when using logarithmic scaling.
Concerning stability of (some) amps your idea is worth thinking.
But concerning the behaviour of the speaker array itself, series
wiring is no good idea to me ...
Kind regards
LineArray said:
well, perhaps, I don't know
on the other hand the fact is that series wiring is quite common in line arrays, after all it is a part of "series/parallel wiring"
Dr Griffin writes in His paper:
so we can safely wire 4 of them in series - says Dr Griffin (and others)
"the speaker never knows that there is another speaker wired in series with it"
see: http://www.monstercable.com/mpc/sta...ing_Woofers.pdf
see also this (from Martin J. King):
http://www.quarter-wave.com/General/Two_Drivers.pdf
so why not wire them all in series? for example 10 of them to get 80 ohms of overall impedance?
perhaps measurable problems of "tolerances" are not a real world audible problems? just like "comb filtering" ("a measurement artifact" - conclusion of Dr Toole's research)
best,
graaf
LineArray said:
Dr Griffin in His paper writes about wiring speakers in series groups first and than connecting those series groups in parallel
He writes about wiring of 6 speakers in series as something quite normal
see: http://www.audioroundtable.com/misc/nflawp.pdf
at page 22
so 6 "Ok" but 10 "no - overdose"?
LineArray said:
I don't know what is enough
perhaps nothing is enough when the aim is "the best"
in audiophile audio "the tendency is to push it as far as You can"
best regards,
graaf
I think the section in the griffin paper is
about power tapering.
If you want to use the impedances of driver groups
for power tapering and beamforming one may subordinate
questions of tolerances in order to obtain the desired
power distribution over the array.
But as far as i understood, you do not use power tapering
or beamforming. You want the drivers to be driven uniformly.
That is the application to which i was answering.
We were not talking about power tapering.
At this point the best might be: Test it.
I would make paralleled groups
( ideally of the most differing drivers) and then wire
those groups in series.
You can connect a switch to each parallel group to make it
series if you want and listen to both variants (series-parallel vs.
total series). Thereby compensating the input voltage
from the amp properly. Cheap experiment.
If there is no difference, there is no difference.
about power tapering.
If you want to use the impedances of driver groups
for power tapering and beamforming one may subordinate
questions of tolerances in order to obtain the desired
power distribution over the array.
But as far as i understood, you do not use power tapering
or beamforming. You want the drivers to be driven uniformly.
That is the application to which i was answering.
We were not talking about power tapering.
At this point the best might be: Test it.
I would make paralleled groups
( ideally of the most differing drivers) and then wire
those groups in series.
You can connect a switch to each parallel group to make it
series if you want and listen to both variants (series-parallel vs.
total series). Thereby compensating the input voltage
from the amp properly. Cheap experiment.
If there is no difference, there is no difference.
LineArray said:
this specific section is about power tapering
BUT nowhere in the paper He says that parallel is preferable to series wiring
all He says is:
nothing about what is to be preferred
Can we say that Dr Griffin overlooked an important problem?
LineArray said:
BUT if "one may subordinate questions of tolerances in order to obtain the desired power distribution" then why not subordinate questions of tolerances in order to obtain something else that is the desired overall impedance?
isn't it that if it can be subordinated to beamforming then it is not really important in the sense that subordinating it does nothing harmful to the sound quality?
LineArray said:
well, easy to say
I am not a technical person, just a music lover
and there is more fundamental question - is it worth testing? is lowering the level of distortion significant enough to justify trying something like this?
sreten was suggesting that it was not (it would not be better - only "better")
what is Your opinion?
best,
graaf
Hi graaf,
this is how i see it:
- Power tapering has major effect.
- Tolerance Problems between drivers have minor effect,
which may tend to more majority dependent on the quality
of drivers used and the "amount of seriality" in your circuitry.
- Impedance issues when using a stable and well designed
amplifier have minor effect in the impedance ranges
( 8 .. 80 Ohms) you are talking about. The effects tend to more
majority when exotic amp designs (tube amps e.g.) are used.
---
Testing the relevance of the effects is really simple and takes
less time than discussion in this case. You can ask a friend to
pull the switches and do a blind test with yourself and your friends.
"Can we distinguish the two settings in a blind test ?"
"Is the difference a difference in the sense of better/worse ?"
Thats the way i often do it. It is fun and there is always
something to learn. Often one learns something different than
expected.
Kind regards
this is how i see it:
- Power tapering has major effect.
- Tolerance Problems between drivers have minor effect,
which may tend to more majority dependent on the quality
of drivers used and the "amount of seriality" in your circuitry.
- Impedance issues when using a stable and well designed
amplifier have minor effect in the impedance ranges
( 8 .. 80 Ohms) you are talking about. The effects tend to more
majority when exotic amp designs (tube amps e.g.) are used.
---
Testing the relevance of the effects is really simple and takes
less time than discussion in this case. You can ask a friend to
pull the switches and do a blind test with yourself and your friends.
"Can we distinguish the two settings in a blind test ?"
"Is the difference a difference in the sense of better/worse ?"
Thats the way i often do it. It is fun and there is always
something to learn. Often one learns something different than
expected.
Kind regards
Hi,
there is something i forgot:
in my own line array shown on my website i select the drivers
very carefully. Since in that design the highs are produced
mainly by the upper 3 drivers, this has a large effect.
Fullrange drivers (even of same type) sound normally
different especially in presence and brilliance region.
This is why i select the drivers according to their position
in the line.
A dull or sharp sounding one will not play in the mid-highrange group.
Left and right speaker are built by selecting "similar"
sounding drivers at same positions. The effect is far from being
"minor" and affects the design of the crossover (i could build it
more simple and drop some compensation components when
doing that selection consequently).
Grab some of your drivers, just take one at a time in your
hand and listen to different ones sitting on your sofa using
a connection you can switch quickly. You can vary distance
and angle, just play with them like child. You can apply
noise from a tuner e.g. or listen to repeating passage of
music.
After a while playing you can distinguish them by their name.
You will be surprised, when have never done that.
Kind regards
there is something i forgot:
in my own line array shown on my website i select the drivers
very carefully. Since in that design the highs are produced
mainly by the upper 3 drivers, this has a large effect.
Fullrange drivers (even of same type) sound normally
different especially in presence and brilliance region.
This is why i select the drivers according to their position
in the line.
A dull or sharp sounding one will not play in the mid-highrange group.
Left and right speaker are built by selecting "similar"
sounding drivers at same positions. The effect is far from being
"minor" and affects the design of the crossover (i could build it
more simple and drop some compensation components when
doing that selection consequently).
Grab some of your drivers, just take one at a time in your
hand and listen to different ones sitting on your sofa using
a connection you can switch quickly. You can vary distance
and angle, just play with them like child. You can apply
noise from a tuner e.g. or listen to repeating passage of
music.
After a while playing you can distinguish them by their name.
You will be surprised, when have never done that.
Kind regards
LineArray said:
Power tapering is very interesting
Can You desribe this effect subjectively?
in what sense does the tapering give better sound?
I ask because not everyone uses it and also Dr Griffin doesn’t seem to think it is mandatory for best results
From what He writes in His paper it looks more like case of certain individual preferences than sound quality strictly speaking
it seems to be like "making difference but not necessarily better/worse"
And Dr Griffin doesn’t really explain what is the nature of the problem which he poetically calls "sound bloom"
He refers to various effects of binaural hearing like Haas effect, but they concern sound direction in lateral plane - left-right - and not in the vertical plane
Neither he gives any references from professional literature for this problem
But if power tapering of a near field array is really important for good sound quality then my idea is not good because one must choose between this and power tapering, both cannot be done at the same time
And I am interested in high impedance loudspeaker but not at the cost of more important qualities
therefore I ask
best,
graaf
sreten said:
Hi,
Which is why I'm not going to expand on what I've already said.
An amplifier capable of 500W running at 50W all things being
equal will be better than a 50W amplifier, but x10 the cost.
Ok. I see
Thanks
but WHY "x10 cost"?
perhaps sometimes less expensive 500W amp running at 50W can offer better quality than more expensive 50W running at 50W?
best,
graaf
@ graaf:
Concerning power tapering this leads into philosophical
questions.
What i use is a frequency dependent power tapering.
Which means the array gets shorter with increasing
frequency. In my design this is supported by the placement
of the drivers. The result is not a near field line Array anymore.
The subjective effect is that the virtual sound sources
do not move with you when you move your head vertically.
Virtual sound sources have a fixed vertical position in space.
My subjective impression is a more direct sound and a more
concrete spatial imaging.
When using power tapering for the bass too, you loose some
advantages of the array:
- Directivity in low frequency range (some say this is not
necessary, but i do concerning excitaton of room modes)
- Maximum addition of the radiation impedance of the drivers,
giving high efficiency and dynamic headroom.
But you could do that in a simple way by combining
series/parallel groups of drivers.
So called Bessel arrays distribute the power over the length
of the array according to the bessel function, which is quite
common.
-----
-----
If you study that Griffin paper you see that the transition
from nearfield to farfield is dependent from length of the array
and frequency radiated.
The ideal for me - which is not reached by my design, but
intended and approximated to a certain point- would be
a line array with transition from near field to far field at a
constant listening distance and independent from frequency.
This transition should be at a practical listening distance in a
living room, say 1,5 - 2,5 m.
This is a very personal philosophy and i do not encourage
anyone to follow it. Neither i do claim that my "dipol 08"
design is the only way to go into that direction.
If you want to adapt that design, be warned because
crossover circuit is somewhat tricky to design and tune.
You have to compensate shrinking of radiating diaphragm
area with frequency, thereby taking the behaviour of your
individual drivers into account.
Some guys combine a line array with a conventional single
tweeter in the center, which goes into a similar direction
(and is more easy to handle technically IMO) but causes a
frequency response dependent from vertical listening angle at
crossover frequency. Additionally there is a sharp discontinuity
in vertical distribution, which is undesirable IMO.
Kind regards
Concerning power tapering this leads into philosophical
questions.
What i use is a frequency dependent power tapering.
Which means the array gets shorter with increasing
frequency. In my design this is supported by the placement
of the drivers. The result is not a near field line Array anymore.
The subjective effect is that the virtual sound sources
do not move with you when you move your head vertically.
Virtual sound sources have a fixed vertical position in space.
My subjective impression is a more direct sound and a more
concrete spatial imaging.
When using power tapering for the bass too, you loose some
advantages of the array:
- Directivity in low frequency range (some say this is not
necessary, but i do concerning excitaton of room modes)
- Maximum addition of the radiation impedance of the drivers,
giving high efficiency and dynamic headroom.
But you could do that in a simple way by combining
series/parallel groups of drivers.
So called Bessel arrays distribute the power over the length
of the array according to the bessel function, which is quite
common.
-----
-----
If you study that Griffin paper you see that the transition
from nearfield to farfield is dependent from length of the array
and frequency radiated.
The ideal for me - which is not reached by my design, but
intended and approximated to a certain point- would be
a line array with transition from near field to far field at a
constant listening distance and independent from frequency.
This transition should be at a practical listening distance in a
living room, say 1,5 - 2,5 m.
This is a very personal philosophy and i do not encourage
anyone to follow it. Neither i do claim that my "dipol 08"
design is the only way to go into that direction.
If you want to adapt that design, be warned because
crossover circuit is somewhat tricky to design and tune.
You have to compensate shrinking of radiating diaphragm
area with frequency, thereby taking the behaviour of your
individual drivers into account.
Some guys combine a line array with a conventional single
tweeter in the center, which goes into a similar direction
(and is more easy to handle technically IMO) but causes a
frequency response dependent from vertical listening angle at
crossover frequency. Additionally there is a sharp discontinuity
in vertical distribution, which is undesirable IMO.
Kind regards
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