4 OHM LOAD WITH AN 8 OHM CABINET?

#61
agedhorse said:
The ASX series uses a different power supply topology and is not regulated, thus my comment applies to products using the ASC series (almost all of the newly released products)

I designed a power supply that used PWM regulated voltage foldback control for high line management specifically, and this was almost 15 years ago. It's not new technology by any means.
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If it is true that these new SMPS class D amplifiers actually produce double the power into 4 ohms, that is excellent news, though I would still like to see some reliable data which support that assertion in the real world. I know that Krell has made some amps which which produce prodigious amounts of current into very low impedance loads, but again these are not typical.

Still, I think it is important that anyone reading this thread does not simply assume that they will see a full 3dB increase in SPL if using a transformer to convert an 8 ohm to a 4 ohm load, because that will typically not be true. A near 3dB increase in SPL can only be gained if certain conditions are met, including an amp that doubles output power into 4 ohms and that power compression and other factors are negligible.
 
#62
12bass said:
If it is true that these new SMPS class D amplifiers actually produce double the power into 4 ohms, that is excellent news, though I would still like to see some reliable data which support that assertion in the real world.
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Just look at the ICEpower data sheets.
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ICEpower – Class D OEM audio amplifiers – Consumer & Professional Audio
 
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#63
Passinwind said:
Just look at the ICEpower data sheets.
Yel_wink.gif


ICEpower – Class D OEM audio amplifiers – Consumer & Professional Audio
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Manufacturer's data sheets are not always the most reliable or accurate source of information. Further, many bass amp manufacturers are claiming output power which exceeds that specified by B&O in the data sheets and bench testing of some of these amps has shown that they fail to meet such claims (while some have met or exceeded specified performance). This why I suggested providing some real world bench test results, because reliable real world results are better than unsubstantiated manufacturer's claims.

For a 3dB SPL increase I might consider using a transformer, but for 1dB I would not bother with the trouble or expense.
 
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#64
12bass said:
Manufacturer's data sheets are not always the most reliable or accurate source of information. Further, many bass amp manufacturers are claiming output power which exceeds that specified by B&O in the data sheets and bench testing of some of these amps has shown that they fail to meet such claims (while some have met or exceeded specified performance). This why I suggested providing some real world bench test results, because reliable real world results are better than unsubstantiated manufacturer's claims.

For a 3dB SPL increase I might consider using a transformer, but for 1dB I would not bother with the trouble or expense.
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Their claims are completely accurate, conservative and substantiated (presuming you understand the data of course).
 
#66
RoadRanger said:
There you go again, challenging TBer cherished beliefs with facts ;). I'm sure glad I don't have to market my products to this "demographic" LOL.
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Not sure to whom you are referring? I am asking for facts, for reliable, accurate, measured data.

If I were looking to buy another bass amplifier, I would be much more likely to purchase a unit which had been bench tested under controlled conditions and shown to meet or exceed its specifications than another unit from a manufacturer who only made unsupported claims on marketing documents. In other words, I'm seeking hard facts, as should anyone thinking about making an expensive purchase, IMO....

I have an MA in philosophy with a special interest in the area of epistemology. I care deeply about the veracity of information and seek accuracy whenever possible. I am certainly not the sort of individual who "chooses to believe whatever I want", as I think that line of thinking is an untenable doxastic methodology.
 
#67
agedhorse said:
Their claims are completely accurate, conservative and substantiated (presuming you understand the data of course).
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Frankly, I feel as if there's a "defending my castle" sort of thing happening here and that that is a disservice to people who might be considering using a transformer to convert their 8 ohm cabinet to a 4 ohm load.

That's great if the above is true. I would like to believe B&O's claims, but think that it would be wise to seek impartial third-party confirmation.

Assuming it is true, then there are cases where a near 3dB SPL gain can be achieved. For those cases, a transformer may be a reasonable option. However, that stipulation appears to apply to only a small subset of existing bass amplifiers and is thus not true in the majority of cases where only a 1 to 1.5dB gain may be possible, making the addition of a transformer of questionable value.
 
#69
Geez, I tried to provide helpful information to folks with a question that might apply to others and this is the kind of response I get... and from a philosophy major to boot? Why are you so argumentative about everything 12bass???
 
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#70
agedhorse said:
Geez, I tried to provide helpful information to folks with a question that might apply to others and this is the kind of response I get... and from a philosophy major to boot? Why are you so argumentative about everything 12bass???
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Because a process of employing rational argumentation informed by objective data clarifies matters of fact. I seek clarity in understanding. Not a personal thing.

Off to Yellowstone.... ☺
 
#71
It being a tube amp it could sound different with a 4 ohm load, depending on design and so forth. The lower impedance load may give a nicer (softer) clipping characteristic. This is something that could be tried with a resistive load in parallel with the speaker. If it sounds better then one could stay with the resistive load in parallel - the amp will presumably be putting out more power, and as we all know a 3 dB drop is almost inaudible. ;)

Or find some cheapish transformer and try it.
 
#72
agedhorse said:
Geez, I tried to provide helpful information to folks with a question that might apply to others and this is the kind of response I get... and from a philosophy major to boot? Why are you so argumentative about everything 12bass???
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Guess you haven't encountered many philosophy majors? It's their "thing" to argue everything. I'da guessed the left coast was infested with 'em but we sure have our share hereabouts. So, how many hands clapping simultaneously does your amp support ;) ?
 
#73
BTW strangely enough the first bass cab I ever bought had two 8 ohm 15" speakers in it and a 8/4 ohm autotransformer inside. I removed that as my second hand Heathkit bass amp (decapitated from their combo by the previous owner) was 4 ohm capable. Think I still have this around someplace, maybe rated at 100w? Weird cab, it was wider on the bottom than the top, slot ported on the back, speakers arranged vertically, blond color wood - no idea what brand, heck I'm not 100% of much from those days ;) .
 
#74
12bass said:
...While impressive, amplifiers which can produce a doubling of power into 4 ohms appear to be a statistical outliers.
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I have routinely seen it in amps that can drive 2 ohm loads. The power output from 8 ohms to 4 ohms doubles but 4 ohm to 2 ohm does not. I don't know why, perhaps it is a PS regulation issue.

And truth be told, I have quit monitoring those numbers. Now I just play bass.
 
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#75
RoadRanger said:
Guess you haven't encountered many philosophy majors? It's their "thing" to argue everything. I'da guessed the left coast was infested with 'em but we sure have our share hereabouts. So, how many hands clapping simultaneously does your amp support ;) ?
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Funny!

I wonder how philosophy majors stay married? It must be exhausting... ;)

I don't have any real data on hands clapping support at the moment ;)
 
#77
Marial said:
Would make an excellent death metal song title. Maybe add 'of necrotic torture' at the end.
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LOL...

FWIW, I wasn't arguing because I like to argue. Rather, I was attempting to clarify some issues because I was concerned that future readers of this thread might get an incorrect impression regarding a complex question.

If someone happens to have an amp that doubles output power into 4 ohms and they are able to find good quality, reasonably priced, transformer with minimal insertion loss, then they may see close to a 3dB increase in SPL, provided that the transformer and speaker are operating in a linear fashion (minimal loss, power compression, etc...). However, while this scenario seems to apply for certain new low power, regulated, SMPS class D amps, I'm uncertain if this recommendation can be rightly generalized for most bass gear out there today. Individuals with amps which do not double output power will see lesser gains. Finding a suitable transformer for higher power levels may be costly or impractical. Power compression and other non-linearities may also limit potential gains at higher power levels. The gist, as agedhorse has said himself, is that it depends....
 
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