Archived from groups: rec.audio.high-end (
More info?)
Stewart Pinkerton <patent3@dircon.co.uk> wrote in message news:<cnljcu01fk3@news1.newsguy.com>...
> On 19 Nov 2004 00:44:59 GMT, wdirksen@p-we.com (Wessel Dirksen) wrote:
>
> >Stewart Pinkerton <patent3@dircon.co.uk> wrote in message news:<cngumf0dn6@news2.newsguy.com>...
> >> On 17 Nov 2004 00:42:35 GMT, wdirksen@p-we.com (Wessel Dirksen) wrote:
> >> >
> >> >This issue seems to come back quite often and it's good to see that
> >> >there is a general tendancy to dispel fuzzy logic. Yet "lamp cord" as
> >> >I would define it is reletively high guage wire (20 tot 16 guage) with
> >> >potentially non-negligable DC resistance characteristics. So I don't
> >> >agree that is all the same in comparison to let's say 12 of 10 guage
> >> >OFC wire.
> >>
> >> Neither does anyone else, if you took the trouble to notice that the
> >> above comments *specifically* stated 'same gauge'.
> >>
> >My input was meant to be general and not a specific reply to the
> >above. I noticed that virtualy all of the strings seemed to omit the
> >DC resistance issue which is a factual matter and not a matter of
> >hype; whether its significant or not.
>
> Untrue - almost all cable discussions mention loop resistance at some
> point, and any DBT discussion always mentions level-matching, and the
> fact that there's no merit in comparing cables with massively
> different RLC parameters.
Hi Stewart,
The whole DC resistance thing is important to me and that's what's
fueling my input here. So this reply is about DC resistance in general
as it applies to loudspeaker performance, whether from cable or
inductors. So please consider this a departure from the above. As
such, I appreciate the discussion on this.
>
> >>I'm curious how others feel about a similar fenomenon with lossy
> >> >inductors in the signal path in woofers. It is my personal view that
> >> >series DC resistance in the signal path should be strategically
> >> >minimized as much as possible. The overall Q factor of the filter
> >> >doesn't have to suffer from this if you are in control of the design
> >> >process. Once again in the interest of affording the amplifier maximum
> >> >EMF control of it's load along with minimized DC loss along the way.
> >>
> >> It is my personal view that speaker designers in the major companies
> >> know what they're doing. If a lossy inductor is used, then that is
> >> factored into the overall voicing of the speaker.
> >
> >Agreed, this is a question of good engineering. But the choice of
> >inductors in a production loudspeaker is ussually not based on optimal
> >performance, but on minimizing the negative affects of compromise.
> >This is act of life due to aggressive cost budgets to which all
> >loudspeaker engineers must adhere in a production setting. (exotica
> >excepted) Low Rdc inductors are expensive, and as you state below, is
> >not a bad strategic area to save some money. But that doesn't mean
> >that lowering series DC resistance to woofers is theoreticaly not
> >audible or desirable.
>
> Sez who? Have you ever done a listening comparison?
Well, sez me I guess.
As I have brought in before here, I do loudspeaker modification and
design professionally, and for quite some time now and have seen and
modded filters of many loudspeakers. So FWIW, my input is based on
personal experience which I will carefully dare to call expertise not
just conjecture. All along the way I listen and compare all the time
very often with a someone next to me so I'm not listening alone. Even
though it only affects a small part of the overall performance of the
entire design, I have discovered that reduction of this DC resistance
thing is easily the most repeatable noticeable improvement you can
make to a standard production loudspeaker with lossy inductors. So
this is a petpeev issue with me especially since this seems to be
downplayed or held silent by the bulk of this expert group now and the
last time this came up. This is a last stab at throwing this out there
for scrutiny. I am curious to know why there is a tendancy to
underestimate/disbelieve this issue while experience has shown me that
there is almost nothing else more predictable as a focus for
improvement. Heck, maybe I'll learn more about loudspeakers and people
while I'm at it.
This is what I have been doing on a regular basis: I've been almost
exclusively using German Intertechik HQ-80 inductors (large, very
densely compressed ferrite powder inductors) for about 10 years since
they have been on the market. They allow air core quality at normal
power levels for living rooms often less than 10% of original series
resistance. (ex. 1.5mH has 1.6mm diameter copper wire, Rdc=0.07ohm) If
you doing nothing else besides this swapping the series woofer
inductor(s), but make small value adjustments in the rest of the
filter to restore original filter response, the difference in bass
definition is astounding. The sole negative factor that seems to
infrequently pop up with such projects is a less stable image. This is
however greatly dependant on the amplifier and filter topology. Also,
if this occurs, it is usually fixable and change is warranted since
this indicates an overall vulnerable filter design.
>
> >None of these
> >> parasitic resistances bear any comparison to the resistance of the
> >> voice coil.
> >
> >If "lampcord" and inductors add 0.5 ohm of DC resistance, but very
> >often even more than this, than this constitutes almost 10% increase
> >of a standard driver Rdc of 5.2 to 5.7 ohm. This is audible in most SS
> >amplifiers, although subtle. It is enough to possibly make more than 1
> >db SPL changes in a majority of tube amplifiers. This doesn't cover 4
> >ohm drivers which typically have Rdc values of 3.9 ohm or so making
> >the phenominon more distinctive.
>
> Agreed that it may reduce the sensitivity of the speaker by a dB or
> so. Just add more power - not an issue for a real amp, i.e. SS.
>
> >Please note also that over the vast majority of its
> >> working range, a loudspeaker is mass/compliance controlled, and
> >> electrical 'damping' is not a factor.
> >
> >Agreed to a point. Bass is where this really becomes a common factor
> >to contend with for all amps. Tweeters /midranges often have resistors
> >in series. But I personally like my bass tight and find it reason
> >enough to pay attention to this.
>
> If you like your bass 'tight', then get a system with a Qts of less
> than 0.7. Agonising about inductor resistance won't make any
> difference.
Improving speakers is only sometimes agonizing, yet in the end always
fun.
But I'm glad you brought this up for 2 reasons. One change that can
occur with lowering of overall Rdc is lowering of Qe and thus overall
Q of the woofer. Depending on the amount of resistance recovered, this
is usually measurable yet negligible. Yet lowering of overall Q will
in theory improve transient response.
Second, many assume based on the calculated impulse response for the
well known transfer functions that there would have to be an obvious
audible difference in the subjective "tightness" of bass between let's
say a Qtc of 1.0 and 0.71 in sealed cabinet designs. Yet as it turns
out, listeners find the wider –3db bandwidth in higher Qtc speakers
subjectively discernable as "lower bass" but not necessarily "looser
bass". I do realize however that the occaisional subjective impression
of "more bass" can come from a looser impulse response. These kind of
controlled alignment comparisons within a limited range are common in
the R&D process for a production product when deciding on final design
so it happens all the time. Yet it seems such alignment comparisons
never seem to be as pronounced as the subjective "loosening" of the
low bass when adding a 0.5 or higher resistor in series with the
woofer with thereby only a slight increase in overall Qtc.
>
> > Also, with tube amps, the entire
> >frequency spectrum can be affected. If a SS amp with a damping factor
> >of 400 gets 0.5ohm between output and voicecoil it will be subtle. A
> >tube amp with a damping factor of 30 can easily have measurable SPL
> >variances especially at the low end.
>
> This is utter nonsense! The effect of parasitic resistance in a series
> inductor will if anything be *worse* for an amp with low output
> resistance, and the whole point of an inductor is that its impedance
> rises with frequency, so it's clearly rubbish to suggest that its
> series resistance will have any effect outside the bass range.
> Certainly, any FR differences caused by the high output resistance of
> say a SET amp will be the same as they would be had the speaker been
> otherwise designed, because the speaker will have been 'voiced' for
> whatever crossover components are used.
Whoa, I'd watch it with the superlatives but it's obvious you don't
agree. Also, it is primarily the bass range that I'm referring to
here. Just for the sake of definition, the FR of any amplifier is
defined by both it's own design (something I know nothing about) and
the load connected to it. The latter is out of the amplifiers direct
control. If you wanted to get devious, you could probably screw up the
FR of even the most stable and neutral SS amplifier if you know what
you're doing just by giving it a strategically sadistic load. Tube
amps are more sensitive and thus often slightly differ in FR from
speaker to speaker which nearly always have wacky loads. Therefore
there is no guarantee the "voice" of the filter design will be able to
speak neutrally if the input impedance of the speaker is such that the
amp cannot drive it neutrally. This is subtle if not negligable but
nonetheless a fact of life for many tube amps.
>
> >Basically, keep the loop
> >> resistance of the wire below a twentieth of the speaker nominal
> >> impedance, and you won't have a problem. Just as an illustration,
> >> that's twenty five feet of 16 AWG for a four ohm load. We audiophile
> >> types do tend to overkill on this matter of speaker wire resistance!
> >
> >True, but those typical cheap inductors add 5 times as much "wire" to
> >the signal path as your 25 feet of 16AWG. Together, I'm not so sure
> >its harmless anymore.
>
> As noted above, I suspect that the speaker designer knows more about
> this than either of us. If that kind of thing bothers you, then use
> active speakers, where the amps are directly connected to the drivers,
> or choose one of the two-way designs which has no crossover components
> connected to the bass/mid driver.
Now this is interesting if I may. Intelligent consumers are usually
critical and hopeful they make the best buying decisions and may feel
proud of some possessions enough to feel fond of them. Heck all the
cars I have owned have had a name. But few question that
unpleasantries lie waiting such as planned obsolescence, and quality
compromise vs. cost. Of course there is a difference between function
and performance. A gadget may be price-performance designed and
marketed for longevity, performance or usually a planned mix of both
in a certain proportion. But most agree you usually can't get both for
the price of one. So if we can accept that our toaster has economic
design limitations, why is there a general tendancy to accept the idea
that a loudspeaker design has been designed to a holy grail standard.
B&W is a good case in point, they are very good at engineering a solid
performing package together at a good price point, but only relatively
recently have they been truly able to deliver +/- non-compromise
ideology type designs. So outside of these models, you can usually
easily improve the performance of virtually any B&W, not because the
design is inferior, but because you can go after the areas they had to
skimp on. Incidentally, lower DC resistance inductors are being more
and more implemented through the years as technology and production
methods get better and cheaper. Along with it, the average hi-fi
speaker is much better out of the box than 10 years ago at the same
price point.
To illustrate from a trusted source, I'm wondering if Dick Pierce is
listening and can share light if he has ever seen the inside of a
production loudspeaker which he couldn't easily improve. I doubt are
many if any at all.
/www.stealthmicrophones.com
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