From organtec@charter.net Sun Sep 11 15:51:56 2011
Subject:Re: Leslie woofers 16-ohm
Gary,
Variable impedance with frequency, speaker enclosure loading is a given. Depending on WHAT 8 ohm speaker is used in a Leslie is a greater influence of crossover/phase considerations than just saying an 8 ohm load will shift crossover greatly. Some really upset the apple cart while others stay very close to original.
For sure on a ‘short’. Sometimes lets the smoke outJ
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com] On Behalf Of Gary Brumm
Sent: Sunday, September 11, 2011 12:58 PM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
Keith,
That 4 ohms is a nominal value based roughly on the DC resistance of a speaker. Once you apply AC (audio) it becomes a variable reactive load
and is no longer a static resistive load so the 4 ohm rating will change based on the speaker and enclosure design. If the woofer is changed in a
Leslie from 16 ohm to 4 or 8 the crossover frequency will change. Phase will be affected as well. Power output in a SS amp will be higher with
a lower impedance but is dependent on the power supply design. One thing a SS amp definitely doesn’t “like” is a short at the output. ☺
Gary
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com ] On Behalf Of Keith H Clark
Sent: Sunday, September 11, 2011 3:28 AM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
Gary,
I can make a statement as such. Most solid state amps operate the most efficiently at 4 ohms. Solid state devices by design and their low impedance, much higher damping factor, 4 ohms is the best comprise between higher impedance and 2 ohms and below operating too close to a shorted output. Earlier SS designs operated into 8 ohms as we were leaving the 16 ohm speaker impedance that tube amps were rated at. The speaker norm was 16 ohm, went to 8 ohms. Now it is very common to see 4 ohm speaker impedances. That wasn’t done for fashion but a better match for SS amp output stages. Now 2 ohms for auto usage is common. Amps are designed to work into such a low impedance safely.
16 ohm was favored in tube designed made it easier for a smaller spread of impedance matching ( correcting ) from the high impedance of the tube output stage to the speaker load. Also tube amp is a voltage device vs solid state as a current device.
The best impedance matching to speaker loads in a solid state amp still remains the McIntosh autoformer in their output stage. It is wound with as near perfect match to the output stage as possible, and having various impedance speaker taps to allow full power output to any of the loads connected to it. It has other favorable attributes as well.
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com ] On Behalf Of Gary Brumm
Sent: Sunday, September 11, 2011 3:25 AM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
Keith,
Where in the world did you get the idea the solid state amps “favorite” impedance is 4 ohms?
There is no way you can make a generalized statement like that.
Gary
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com ] On Behalf Of Keith H Clark
Sent: Saturday, September 10, 2011 2:33 PM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
Chris,
Not nitpicking. Solid state amps favorite impedance is 4 ohms. It seems to happen that way with solid state outputs, EXCEPTION, transformer coupled.
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com ] On Behalf Of Chris Richmond
Sent: Saturday, September 10, 2011 11:42 AM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
Keith,
You are mostly correct, but I have to take minor exception with your comments on solid state amps.
You are correct, assuming nothing in the design was limiting the output power at low impedance, however
if the amp’s power supply was current limited or the amp had overall thermal limits with a 2 ohm load, but
not so with a 4 ohm load, then you may actually get a power rating that looks different than what you predict.
Example: 400w@2ohms, 275@4ohm, etc. Sorry if that seems like picking nits.
Chris
From: CloneWheel@yahoogroups.com [mailto:CloneWheel@yahoogroups.com ] On Behalf Of Keith H Clark
Sent: Saturday, September 10, 2011 6:54 AM
To: CloneWheel@yahoogroups.com
Subject: RE: [CWSG] Re: Leslie woofers 16-ohm
There are some amps which are rated at a 2 ohm load. Deceptive advertising which gives greater power output figures and makes it look more powerful. Yes, the amp will probably work at that load impedance as it was built to do so. But as far real power rating, the STANDARD impedance for ratings is for 8 ohms. So an amp rated @ 400 watts into 2 ohms is just that. Into 4 ohms it will deliver half or 200 watts. Into 8 ohms, 100 watts. Not so impressive now, is it?
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