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Acquiring an SWR SM-900, reasonable?

#41
agedhorse said:
The 960 watt input power is based upon the duty cycle being less that 100%.

Generally 1/8-power (12.5% duty cycle) is the minimum that can be stated and is what the test labs will use but some designers (including me) state the input power at a higher duty cycle (I use between 33% and 40% depending on the products).

With an AB power amp, linear power supply, the overall efficiency is about 50%, so the 100% duty cycle input power will be about 900 rated power X 2 = 1800 watts. Now to me it looks like the duty cycle is also right around 50% which is how they get 960 watts input power.
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I don't disagree, but oddly enough Andy I think that on the 110 V version on the SM900 (which can run a 4 Ohm load bridged) that same input power marking is around 1400 Watts (I'm going from memory). Is it possible that when they substitute parts to convert to the 230 V version certain aspects of capability are then downgraded because of those parts having less lesser capability or a lesser design margin to meet safety requirements at 4 Ohms?
 
#42
Al Kraft said:
I don't disagree, but oddly enough Andy I think that on the 110 V version on the SM900 (which can run a 4 Ohm load bridged) that same input power marking is around 1400 Watts (I'm going from memory). Is it possible that when they substitute parts to convert to the 230 V version certain aspects of capability are then downgraded because of those parts having less lesser capability or a lesser design margin to meet safety requirements at 4 Ohms?
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I wouldn't think so, but I'm going to check the docs...

Ok, they were originally all screen printed 960 watts power input, but when Fender redesigned the SM900, due to the way they labeled all of their amplifier products, the newer Fender versions were screen printed 1400 watts. These Fender manufactured units are labeled on the rear panel Corona, CA. The older versions are from Sylmar or Sun Valley and probably not labeled as such on the rear panel.
 
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#43
agedhorse said:
I wouldn't think so, but I'm going to check the docs...

Ok, they were originally all screen printed 960 watts power input, but when Fender redesigned the SM900, due to the way they labeled all of their amplifier products, the newer Fender versions were screen printed 1400 watts. These Fender manufactured units are labeled on the rear panel Corona, CA. The older versions are from Sylmar or Sun Valley and probably not labeled as such on the rear panel.
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Thanks! At least I remembered it correctly, even if it didn't explain the difference between why 4 and 8 Ohms in different production runs of the same product. :)
 
#44
The Fender version was quite different, there were changes necessary to meet international safety regulations. IMO, the later version was more robust.
 
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#46
agedhorse said:
The Fender version was quite different, there were changes necessary to meet international safety regulations. IMO, the later version was more robust.
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You're not the first person with real expert knowledge I've heard say this. While I've read many comments that the pre-Fender models were the best products and that Fender just bought and killed off SWR, I think there was more emotion than genuine engineering knowledge behind them. I never saw any evidence (on the consumer/user side) that the Fender SWR products reflected anything other than what I consider impressive Fender engineering and quality levels.
 
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#47
baxter_x said:
Si this very version I'm interested in could be more reliable in the end?
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Maybe, presuming that nobody has been inside the amp messing around.

The pots with concentric controls are more or less unobtanium, as are the knobs themselves. I have not been able to find any sources. Be sure they are working correctly.

Also, be sure the rack ears that are part of the top cover assembly are not damaged, these can crack and split at the bend.
 
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#48
Al Kraft said:
You're not the first person with real expert knowledge I've heard say this. While I've read many comments that the pre-Fender models were the best products and that Fender just bought and killed off SWR, I think there was more emotion than genuine engineering knowledge behind them. I never saw any evidence (on the consumer/user side) that the Fender SWR products reflected anything other than what I consider impressive Fender engineering and quality levels.
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Fender invested considerable money and time into SWR, it was not a “throw-away” investment IMO.

Tastes changed, costs increased, the result was lower than necessary sales.

People feel obligated to throw those large companies under the bus with “populist” rhetoric, when in fact the truth is quite different.
 
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#49
Dam... I really want that amp, but the fact I simply willnever be able to use it bridged is a big problem to me.
@agedhorse could it be so kind of typo, or there were actually some version of the amp like the one I'm interested in?
I'm asking as I've been searching the hole web after such a version and couldn't find one like it.
 
#52
baxter_x said:
Thank you for your feedbacks.
Were you involved in a way or another in the design of the amp?
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Nope, though I worked for the brand's owner through the end of the brand and am familiar with some of the history through my technical research of the products during that time period.
 
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#53
agedhorse said:
Nope, though I worked for the brand's owner through the end of the brand and am familiar with some of the history through my technical research of the products during that time period.
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I see. Can you explain the choice of SWR to offer that "weird" version of the SM-900?
I mean, such a power only available at a minimum of 8 ohms is a bit of a joke to me in terms of usability and design.
 
#56
baxter_x said:
So I guess the amp is pretty old. But how come the versions from the 90s could be bridge at 4 ohms?
And when you mention larger cabs, I think about 810 cabs. And to my knowledge, there are no 8 ohms 810 cabs.
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The earlier versions were just that, earlier.

Larger cabinets for that style or type of amp would be say a 215 cabinet with 2 x 16 ohm drivers wired in parallel. The JBL E-145 (not the K), 2225, etc. would be examples.

Also, it was not uncommon to see 16 ohm 215's, using 2 x 8 ohm drivers wired in series, the amp would deliver about 450 watts RMS into 16 ohms which is ideal for the E-140 as well as the EVM-15L/B. This way 4 x 15's could be operated if needed, though the same power would be available with 2 x 4 ohm cabinets operated in dual mode.

There were also the larger folded horn cabinets with stout drivers, 8 ohm folded horn cabinets were also somewhat common.

Evolution caused the market to adopt 4 ohm bridged as being more useful though, especially as driver power handling increased. That's why later models supported 4 ohm bridged mode and 2 ohm dual mode.
 
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#59
I had a few of the early ones and they were all 800w bridged/mono into 4 ohms. This capability was one of the reasons why I went with SWR and not the Eden WT-800.
Bridged into 8 ohms min seems silly to me…
You’re pretty much limited to a single cab in bridge mode.
 
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