This may be a bit of a bonehead question, but does anyone every consider "system Q?"
You hear about loudspeaker Q and you hear about output impedence, but what about their sum?
What got me thinking about this recently is a set of dipoles (dual concentric + bass) I want to build. Fiddling around with my dipole spreadsheet, I've come up with a ballpark setup. As y'all probably know, dipole bass response is highly dependant on driver Qts, fine tuned with inline resistance.
To drive these puppies, I'd like to whip up a pair of SOZs. Though I have not heard SOZs myself, the preponderance of public opininion seems to sit squarely on the plus side. The one negative review of note, however, comes from Lynn Olson. He says they don't work well with his Ariels.
With all this in mind, I began wondering about the importance of amp output impedence and how it adds to speaker Q. Were the SOZs sub-ideal for the Ariels because their relatively high (for SS) output impedence messed up the tuning of the TLs? What effect would they have on the low end of my dipoles? Is there some factor I can add to be able to model the combination?
So I put it to you, gentle reader: Is "system Q" as simple as adding amp output impedence into Qts? Are SOZs the cat's meow for open baffles? Anything else here I'm missing?
Gratzi
Bill
You hear about loudspeaker Q and you hear about output impedence, but what about their sum?
What got me thinking about this recently is a set of dipoles (dual concentric + bass) I want to build. Fiddling around with my dipole spreadsheet, I've come up with a ballpark setup. As y'all probably know, dipole bass response is highly dependant on driver Qts, fine tuned with inline resistance.
To drive these puppies, I'd like to whip up a pair of SOZs. Though I have not heard SOZs myself, the preponderance of public opininion seems to sit squarely on the plus side. The one negative review of note, however, comes from Lynn Olson. He says they don't work well with his Ariels.
With all this in mind, I began wondering about the importance of amp output impedence and how it adds to speaker Q. Were the SOZs sub-ideal for the Ariels because their relatively high (for SS) output impedence messed up the tuning of the TLs? What effect would they have on the low end of my dipoles? Is there some factor I can add to be able to model the combination?
So I put it to you, gentle reader: Is "system Q" as simple as adding amp output impedence into Qts? Are SOZs the cat's meow for open baffles? Anything else here I'm missing?
Gratzi
Bill
Hello Bill,
if I understand You right You want to know what influence has the output resistance of a given amp on what You call "system-Q".
Usually output resistance off SS-amps is very low (high-damping factor) and effects on system-Q is neglectible.
But in case of higher output resistance of amplifiers as for example most tube amps and maybe Your SOZs too (I don`t know) this affects driver Qes (electrical damping) and therefore Qts (system Q) as well.
There is a simple formular to calculate effects of series resistance Rg on driver Qes:
Qesb=Qes x (1+ Rg : Re)
where is:
Qesbg = the "new" value for driver Qes with series resistance Rg
Re = DC-resistance of the voice coil
Rg = all kind of resistance in series with the driver as: amp.-output resistance, filter-choke resistance, cables
You can easily calculate all those series resistance effects on "system-Q" now:
Qts = Qesb x Qms : (Qesb + Qms)
Hope this was for help
Christoph
if I understand You right You want to know what influence has the output resistance of a given amp on what You call "system-Q".
Usually output resistance off SS-amps is very low (high-damping factor) and effects on system-Q is neglectible.
But in case of higher output resistance of amplifiers as for example most tube amps and maybe Your SOZs too (I don`t know) this affects driver Qes (electrical damping) and therefore Qts (system Q) as well.
There is a simple formular to calculate effects of series resistance Rg on driver Qes:
Qesb=Qes x (1+ Rg : Re)
where is:
Qesbg = the "new" value for driver Qes with series resistance Rg
Re = DC-resistance of the voice coil
Rg = all kind of resistance in series with the driver as: amp.-output resistance, filter-choke resistance, cables
You can easily calculate all those series resistance effects on "system-Q" now:
Qts = Qesb x Qms : (Qesb + Qms)
Hope this was for help
Christoph
Thanks Christoph,
That's how I was thinking it worked. It seems to me like an important thing to consider when you're building a speaker to go with a certain amp.
Bill
That's how I was thinking it worked. It seems to me like an important thing to consider when you're building a speaker to go with a certain amp.
Bill
"It seems to me like an important thing to consider when you're building a speaker to go with a certain amp. "
Not IME. The speaker cable itself often has more effect on dampng than the amp, in most solid state applications. Just use a heavy guage cable and keep your worries to a minimum. Much more importantly than this, is overall impedance of the speaker, when designed for a certain range of amps. Now, if your implementing an ungodly high output impedance amplifier, such as a tube to be used exclusively on a speaker, then referring to the forumula cocolina provided could very well prove beneficial.
John Murphy published some useful data on this subject, if your interested.
http://www.trueaudio.com/post_index.htm
-Chris
Not IME. The speaker cable itself often has more effect on dampng than the amp, in most solid state applications. Just use a heavy guage cable and keep your worries to a minimum. Much more importantly than this, is overall impedance of the speaker, when designed for a certain range of amps. Now, if your implementing an ungodly high output impedance amplifier, such as a tube to be used exclusively on a speaker, then referring to the forumula cocolina provided could very well prove beneficial.
John Murphy published some useful data on this subject, if your interested.
http://www.trueaudio.com/post_index.htm
-Chris
>The speaker cable itself often has more effect on dampng than the amp, in most solid state applications.
I agree that you can ignore the output impedence of most SS amps, as it's typically a fraction of an ohm. However, if I remember right, the SOZ has a 6-ohm output impedence. Driving a 4-ohm bass cabinet, that's certainly going to affect the alignment, IMHO.
Thanks for the link.
Bill
I agree that you can ignore the output impedence of most SS amps, as it's typically a fraction of an ohm. However, if I remember right, the SOZ has a 6-ohm output impedence. Driving a 4-ohm bass cabinet, that's certainly going to affect the alignment, IMHO.
Thanks for the link.
Bill
"if I remember right, the SOZ has a 6-ohm output impedence. Driving a 4-ohm bass cabinet, that's certainly going to affect the alignment, IMHO."
If your data is correct, I would have to assume this amplifier is designed specifically for euphonics, instead of accuracy. IMO their is no excuse for an output impedance that high. However, if you insist on using such a 'special' sounding amplifier........enjoy. hehe.
-Chris
If your data is correct, I would have to assume this amplifier is designed specifically for euphonics, instead of accuracy. IMO their is no excuse for an output impedance that high. However, if you insist on using such a 'special' sounding amplifier........enjoy. hehe.
-Chris
Well, you can take that question up with Nelson Pass.
Just pull on your asbestos underwear before you post on the PassLabs forum. 😉
Don't forget, this is pretty much a fan club.
Bill
"Well, you can take that question up with Nelson Pass.
Just pull on your asbestos underwear before you post on the PassLabs forum. "
NO thank you, I will pass on that. I have better things to do than crash and burn. 🙂
-Chris
Just pull on your asbestos underwear before you post on the PassLabs forum. "
NO thank you, I will pass on that. I have better things to do than crash and burn. 🙂
-Chris
>the speaker cable itself often has more effect on dampng than the amp, in most solid state applications. <
That`s true but in almost any case this kind of speaker cable effects can be neglected too unless You have
many, many meters of thin cable. At usual length of 2-4 meters the influence is minimal.
>Just use a heavy guage cable and keep your worries to a minimum. <
Much more influence than the cables have filter chokes (or do You say coils?).
I does not make any much difference if You hook up some meters of heavy guage cable in front of a drivers series choke that may have dozens of meters of wire which usually has many times the cables resistance
>However, if I remember right, the SOZ has a 6-ohm output impedence. Driving a 4-ohm bass cabinet, that's certainly going to affect the alignment, IMHO<
That is certain!
Depending the driver is damped more mechanically or electrically this will make a big to huge change of the alignment and has to be taken in account by all means.
With this high output impedance You`ll also get some serious frequency deviations due to non-linear speaker impedance - but that`s another topic.
Christoph
That`s true but in almost any case this kind of speaker cable effects can be neglected too unless You have
many, many meters of thin cable. At usual length of 2-4 meters the influence is minimal.
>Just use a heavy guage cable and keep your worries to a minimum. <
Much more influence than the cables have filter chokes (or do You say coils?).
I does not make any much difference if You hook up some meters of heavy guage cable in front of a drivers series choke that may have dozens of meters of wire which usually has many times the cables resistance
>However, if I remember right, the SOZ has a 6-ohm output impedence. Driving a 4-ohm bass cabinet, that's certainly going to affect the alignment, IMHO<
That is certain!
Depending the driver is damped more mechanically or electrically this will make a big to huge change of the alignment and has to be taken in account by all means.
With this high output impedance You`ll also get some serious frequency deviations due to non-linear speaker impedance - but that`s another topic.
Christoph
"Much more influence than the cables have filter chokes (or do You say coils?).
I does not make any much difference if You hook up some meters of heavy guage cable in front of a drivers series choke that may have dozens of meters of wire which usually has many times the cables resistance "
Do you not agree it is always beneficial to use low dcr cable? At least, in this case the resistance of the inducturs in the filter network and speaker voice coil are constants, while the cable is a variable. Using low dcr cable simply insures constant reaction, in most cases using low impedance amplifiers. However, even these effects can be considered insignificant as you stated, dependant on your preferences. Certainly the room itself has more effect than cable resistance in all but the most extrememe cases of small guage or extremely long cables. Large guage cable is so cheap now, i can't find a reason not to use it. True, the only repeatable blind tests picking out wire, were those comparing an average guage wire to an anemic 24 awg moderate length cable run.
-Chris
I does not make any much difference if You hook up some meters of heavy guage cable in front of a drivers series choke that may have dozens of meters of wire which usually has many times the cables resistance "
Do you not agree it is always beneficial to use low dcr cable? At least, in this case the resistance of the inducturs in the filter network and speaker voice coil are constants, while the cable is a variable. Using low dcr cable simply insures constant reaction, in most cases using low impedance amplifiers. However, even these effects can be considered insignificant as you stated, dependant on your preferences. Certainly the room itself has more effect than cable resistance in all but the most extrememe cases of small guage or extremely long cables. Large guage cable is so cheap now, i can't find a reason not to use it. True, the only repeatable blind tests picking out wire, were those comparing an average guage wire to an anemic 24 awg moderate length cable run.
-Chris
Chris,
sure I do agree to use low dcr cable in cases where it is required to keep series resistance to a minimum.
In particular for low impedance speakers this may be beneficial - or may be not - depending of what You want to achieve.
All I want to say is that effects of low dcr parts (cables, chokes) so far they have influence, are not always beneficial though I agree that more often it is desired not to add further resistance.
But sometimes it might be even desired to add some resistance, for example for tuning (increase) driver Q to meet certain requirements (specific alignments, crossovers).
Christoph
sure I do agree to use low dcr cable in cases where it is required to keep series resistance to a minimum.
In particular for low impedance speakers this may be beneficial - or may be not - depending of what You want to achieve.
All I want to say is that effects of low dcr parts (cables, chokes) so far they have influence, are not always beneficial though I agree that more often it is desired not to add further resistance.
But sometimes it might be even desired to add some resistance, for example for tuning (increase) driver Q to meet certain requirements (specific alignments, crossovers).
Christoph
But sometimes it might be even desired to add some resistance, for example for tuning (increase) driver Q to meet certain requirements (specific alignments, crossovers).
Very true. But, it would be VERY unusual to specifically add r by way of the cable. This is 'typically' done WITH specific rated inductors and/or resistors inline with the drivers, so that more or less, r is constant.
Also, it would seem that we agree on just about every issue mentioned so far, and it seems obvious that neither one of us has presented the other with any data the other did not previously possess. Are we agreeing to agree? LOL.
-Chris
Very true. But, it would be VERY unusual to specifically add r by way of the cable. This is 'typically' done WITH specific rated inductors and/or resistors inline with the drivers, so that more or less, r is constant.
Also, it would seem that we agree on just about every issue mentioned so far, and it seems obvious that neither one of us has presented the other with any data the other did not previously possess. Are we agreeing to agree? LOL.
-Chris
Though it`s not a purpose of a forum like this that folks always agree and do not have to present each other anything new - otherwise there would be nothing left to talk about -CHRIS8 said:
it actually seem to appear that we agree to agree!😉
(by the way what means LOL? - I`m not yet so familiar with all this kind of abreviations people using here)
regarding presenting data:
I remember to have an old article from a German Hifi magazine (frome times they were much better than this bullsxxt today) treating so called "dynamic damping" of amplifiers and how to measure it. This might fit well in this thread. Quite interesting point of views and up to now I have not read anything similar. With some more time I could try to get the essentials to be presented here in English later. Let`s see if I can localize it.
so long
Christoph
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