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Post by gzubeck on May 3, 2017 19:29:49 GMT -5
I just started using a A-300 to drive my Boston Acoustic Lynfield 500L series 2 speakers. My A-300 shuts down multiple times a high levels. I have it connected to the pre-outs of a Anthem MRX-510 receiver. My speaker wire is 10gauge solid silver twisted. my RCA's are a little on the low end, but that being the weak link I don't see there being a major issue there. Movies sound great, but music in 2 channel is where it shuts down. What should I do? when you say High....how high? earsplitting levels...Also maybe you should try some 14 gauge wire as the resistance actually might help here... do you have an active preamp going into your a300? you might be doing something here that is pushing the amp beyond its limits and not getting the desired results if the input signal is too weak. |
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klinemj
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Post by klinemj on May 3, 2017 21:16:38 GMT -5
If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here.
Mark
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Post by novisnick on May 3, 2017 21:20:24 GMT -5
If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here. Mark |
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Post by leonski on May 3, 2017 23:57:00 GMT -5
If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here. Mark If all amps were 'equal' driving reactive loads, the above would be a True Statement. 2 amps which measure near-identical (say within 1 or 2 db) into a resistor net may NOT measure even close when driving a highly reactive load. Add In Bottoming out below 2ohms? OUCH! Such data is not easy to come by. Amp manufacturers depend on resistor power to sell amps and would not like it if it were known that the be-all / end-all of amps fell to pieces driving a reactive load. The only reliable source of measured data for speakers is Stereophile. I don't offhand know of similar data for amps. Would those BA speakers be happy with say....100 4ohm watts? Maybe, if the amp would actually deliver that kind of power to a 4ohm / 60 degree load, but otherwise, more power from a More Capable amp is key. |
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Post by gzubeck on May 4, 2017 1:05:34 GMT -5
If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here. Mark I know it's probably not the answer but I was trying to make a connection between less resistance and more resistance threw different sized cables. I found an impedance chart of this speaker and its not just that it dips to 2 ohms it stays there through quite a bit of the lower frequency range. |
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klinemj
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Post by klinemj on May 4, 2017 4:49:45 GMT -5
If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here. Mark I know it's probably not the answer but I was trying to make a connection between less resistance and more resistance threw different sized cables. I found an impedance chart of this speaker and its not just that it dips to 2 ohms it stays there through quite a bit of the lower frequency range. My bet is that any cable difference would be the equivalent of trying to bail out the Titannic with a bucket. Mark |
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KeithL
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Post by KeithL on May 4, 2017 11:25:57 GMT -5
Everyone is looking at this a little bit sideways here. When you've got a very inefficient speaker, that also has an impedance that dips unusually low, and isn't purely resistive at that low point either, the issue isn't just power. Because of the difficult impedance, you need an amplifier that's stable into difficult impedances... And, because of the low efficiency, you need a lot of power.... However, what you need is BOTH AT ONCE. (A super powerful amplifier that isn't stable into low reactive loads will still have problems.) The cable is NOT going to help in a useful way. The cable counts as a more or less pure resistance between the speaker and the amplifier (in series with the speaker). A nice thick cable will basically not count at all (because the amount of resistance it adds is really tiny)... which is the way things should be. A really thin cable, which has a lot of resistance,will actually make things easier on the amplifier, because it makes the impedance of the overall load higher. If you put a speaker cable with 1 Ohm of resistance in there, then the amplifier will see a 3 Ohm load (2 Ohms for the speaker + 1 Ohm for the cable). This will make the amplifier's job easier, but a third of your power will be burned up in the cable, and your damping factor will be reduced to about 8 (so the speaker probably won't sound as good). (Putting in a thin cable, or just a big fat 2 Ohm resistor in series, would stop the amp going into protect.... but it would also adversely affect both the efficiency and the sound quality as well.) The simple fact is that those Boston Acoustics speakers are a really weird and unpleasant load... (to the point where one might even suggest that it counts as a design flaw). They really are outside the boundaries of what you might call "a normal speaker". And, while all of our amps are designed to be stable into low and difficult loads.... The XPA Gen3 amps are BETTER at it than the BasX amps.... If the speakers dip to 2 ohm at a fairly low frequency and are low efficiency and you want to listen at high volume, the answer is amp power...not cables. That appears to be the case here. Mark I know it's probably not the answer but I was trying to make a connection between less resistance and more resistance threw different sized cables. I found an impedance chart of this speaker and its not just that it dips to 2 ohms it stays there through quite a bit of the lower frequency range. |
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KeithL
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Post by KeithL on May 4, 2017 11:37:29 GMT -5
There actually are somewhat informal standards about what the impedance of a speaker should be - based on how it's rated. (And a "4 Ohm speaker" isn't supposed to drop below 3 Ohms or so - certainly not at any frequency where it's likely to need a lot of power.) Of course, if they told you to get an amplifier designed to run a 2 Ohm speaker - your options would be... somewhat limited. (And they wouldn't sell very many of the speakers.) Interestingly (a blast from the past) our old Sherbourn 4Z-75 amp, which was somewhat unusual, was actually rated to run into 2 Ohms or lower. It was designed to run multiple pairs of 4 Ohm speakers in parallel in different zones. If all amps were 'equal' driving reactive loads, the above would be a True Statement. 2 amps which measure near-identical (say within 1 or 2 db) into a resistor net may NOT measure even close when driving a highly reactive load. Add In Bottoming out below 2ohms? OUCH! Such data is not easy to come by. Amp manufacturers depend on resistor power to sell amps and would not like it if it were known that the be-all / end-all of amps fell to pieces driving a reactive load. The only reliable source of measured data for speakers is Stereophile. I don't offhand know of similar data for amps. Would those BA speakers be happy with say....100 4ohm watts? Maybe, if the amp would actually deliver that kind of power to a 4ohm / 60 degree load, but otherwise, more power from a More Capable amp is key. |
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Post by leonski on May 4, 2017 16:59:22 GMT -5
Keith,
thanks for steering the issue back to the speaker, its really wacky load and that REACTANCE is the issue, not necessarily impedance. Though to be sure, an impedance minima AND a huge phase angle together are death for many amps.
It is possible for amps to even become unstable and 'self oscillate' under such conditions. One amp in particular, from out of the past, the Phase Linear 400, was notorious for such behavior. That gave rise to the nickname of Flame Linear.
I think the real take away from all this is that Amp designers and builders do NOT talk very much with Speaker Designers. If they communicated at all, speakers with huge loading problems would not be made or would come with a list of 'recommended amplifiers'.
How often does Rory show up at a meeting with a new speaker and say that 'This is one of the best sounding speakers ever, but needs a very capable amp'? I doubt the speaker would be manufactured. And don't forget that HT receivers are technically the worst, having marginal power supplies and rarely even 6 ohm ratings.
The other thing is that the Original price of the BA speakers was 4500$ give or take. That was pretty rarified territory then and anyone going for those speakers would be spending some serious coin on a presumably very capable amp.
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klinemj
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Post by klinemj on May 4, 2017 17:08:28 GMT -5
When I refered to a powerful amp, I meant one powerful enough at the impedance required and for the efficiency in question (duh...goes without saying...). Anyway, yes...the speakers in question are, for the reasons stated, a tough load to drive. Either buy an amp that can handle it...or ditch the speakers.
I have said here before and will again...I have seen this problem with certain B&W speakers...low impedance dip at certain frequencies and hard to drive efficiencies. It didn't cause the amp to shut down, but it made awful sound from a wimpy amp that would have sounded fine for reasonable speakers.
Mark
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Post by leonski on May 4, 2017 21:04:05 GMT -5
Indeed. Some B&W speakers are AWFUL from an electrical standpoint and generally can't even be recomended for TUBE amps.
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Post by leonski on May 4, 2017 22:07:45 GMT -5
Measuring an amp with THIS system is both measureable and repeatable. While seperating the real performers from the also-rans. audiograph.se/wp-content/uploads/2013/12/PowerCube_12p_brochure_complete.pdfI'll bet some highly regarded amps ($$$$$) would not do so well, while I'd expect the XPA-1 or 2 to do well. What about it guys? Publish THIS data for your top-performers. NOTE: regardless of how the amp performs with this test, it may or may Not sound OK to you in your system. |
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klinemj
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Post by klinemj on May 5, 2017 5:14:53 GMT -5
It's always good to have a more complete picture of performance...like this test provides. Good article.
Mark
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