Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker
Does running this amp in bridge mode mean each channel will see half the impedance i.e 2 Ohm each when connected to a 4 Ohm speaker. If so will this cause a problem when the speaker dips to 3 or 2 ohms?.
Anyone running Benchmark AHB2 in bridged mode with low impedance speakers?.
clio09 You are correct, other than the recommendation by Roger, we haven’t really had any discussion on that. Vertical bi-amping is the way I roll these days and see no reason to go back, regardless of which pair of speakers I am using. I think using two Benchmark amps in that manner will yield very good results.
twoleftears BTW, am I right in noting that there has been little discussion here, until just now, of vertical or horizontal bi-amping, which are other possibilities, no?
My first post to the OP geek101 at the beginning of page one.
Speaker impedance always varies with frequency. Speaker impedance may be much lower than the rated "nominal" impedance at certain frequencies. The over-current fault detection circuits prevent potential damage that can be caused by driving very high signal levels into very low impedances. In STEREO mode, at full output, the current limit can be reached if the load impedance dips below about 1.3 Ohms. In MONO mode, at full output, the current limit can be reached if the load impedance dips below about 2.6 Ohms.
The OP has Legacy Aeris loudspeakers (a design that requires bi-amping) which according to at least one Legacy dealer really likes high power amps. The OP wants to know if the Benchmarks in bridged/mono mode will have trouble driving the Aeris.
I looked at the manual and I dont see any requirement for bi-amping. I dont know of any speaker that "requires" bi amping though I am all for it if there is an active crossover before the power amps.
This is a $21,000 speaker, Why use the Benchmarks on that? There are better choices and bridging the Benchmarks is not a good idea given the low impedance
@ramtubes, Impedance minimum for top section of Aeris is only 3.8 Ohm (this information is from the source). So it seems AHB2 is fine with that.
Which amplifier would you think can be a better option than Benchmark AHB2 given that I have gotten myself one amplifier for $2100?. What do you think in technical terms another amplifier can be better than Benchmark and at what price and size?. I am looking for 150 watts with no distortion per channel easy, which means no crossover distortion or anything else. Just because I have spent some money on a speaker does not mean I am going to weight that and buy an expensive amplifier. If I could find a $2k Legacy Aeris I would have purchased that instead. I want a great amplifier optimized for cost.
Please let me know I have been looking for a while. I just cannot audition 10 amplifiers to compare and select which sounds good in my room and with the speakers I have. I have to look at the specs, build quality, technical innovation and what generally people think. Anything that comes close to this in my opinion is Hypex NC500 based modules which again can be obtained for $2k approximately. I will consider if you can point me few of them.
General rule of thumb is fine but at the end I am constrained by my experience and capacity to audition amps and I like to re-verify past ideas. Technology changes and things change. If someone says X amp sounds good then I have no context, I will go read the specs, read the forums and reviews and move on.
With someone who knows, looking at the access via the back plate amp, it wouldn’t be hard to split the passive xover and add a second pair of speaker terminals for the bass driver. Then you can purchase the 2nd AHB2 and can vertical by-amp for the best sound, as I said in my first post.
@ramtubes, Impedance minimum for top section of Aeris is only 3.8 Ohm (this information is from the source). So it seems AHB2 is fine with that.
Which amplifier would you think can be a better option than Benchmark AHB2 given that I have gotten myself one amplifier for $2100?. What do you think in technical terms another amplifier can be better than Benchmark and at what price and size?. I am looking for 150 watts with no distortion per channel easy, which means no crossover distortion or anything else. Just because I have spent some money on a speaker does not mean I am going to weight that and buy an expensive amplifier. If I could find a $2k Legacy Aeris I would have purchased that instead. I want a great amplifier optimized for cost.
Please let me know I have been looking for a while. I just cannot audition 10 amplifiers to compare and select which sounds good in my room and with the speakers I have. I have to look at the specs, build quality, technical innovation and what generally people think. Anything that comes close to this in my opinion is Hypex NC500 based modules which again can be obtained for $2k approximately. I will consider if you can point me few of them.
General rule of thumb is fine but at the end I am constrained by my experience and capacity to audition amps and I like to re-verify past ideas. Technology changes and things change. If someone says X amp sounds good then I have no context, I will go read the specs, read the forums and reviews and move on.
Thanks for your questions.Right now you have an amplifier and speaker that are working for you. It would be wise to find out some things about how you listen.
Do you have and SPL meter, the RadioShack one is quite good? The cellphone aps accuracy is unknown but better than guessing, Guessing never works.
Do you have a meter that can read AC or Peak volts? An old analog meter would work also. We need to find your power level unless you already know it.
The sensitivity appears to be 95 dB. Is this at 2 or 2.8 volts? Try to find out, makes a 2 to 1 difference in power,
No one needs an amplifier with specs this good. If the distortion was a four timer higher you would not hear it. I hope the amp has good sound but I would not own it due its complexity. Distortion measurements are done steady state, music may not enjoy those same specs. They worked hard to get distortion this low yet I am unimpressed at how they did it. Look inside that amp and then a Bryston or something traditional. Look at a Hafler, or TransNova, perhaps even a tube amp. This amp has too many parts and the failure rate if chip capacitors is alarming. I pulled a noisy one out of a Mic pre. Last thing I would have expected.
What happens in Electronics is someone gets on a tear to make an amp that excells in some area. If they do this by creating some thing very complex they can make a monster.
Read the Atkinson review. His test equipment is the best and latest test gear yet he can hardly measure the distortion. No one needs this low distortion. How will you know how long it will stay that way?
The coments in this thread about the small increase in distortion was like children arguing over pennies. Same for the damping factor as I have pointed out.
Bottom line, go get a real amplifier. (My shields are UP) :)
Is this amplifier made completely in China, or boards or parts from China? I cant imagine a surface-mount board that large being populated in USA.
geek101 OP227 posts11-16-2018 2:07pm@georgehifi With Legacy Aeris what you are suggesting is not possible.
Of course it is, the plate amp still drives the lower bass as is, the passive xover is split (easy job) so the original terminals do just the mid/highs and a second set of speaker terminals (that has to be put on) do the 10" mid/woofer. So your vertical AHB2, one channel drives the 10" mid/bass and the other channel drives the Tweeters and 8’’midrange, the plate amp still drives the 2 x 12’ low bass. And your other ABH2 does the other speaker.
@ramtubes Agree with you that great specs on a single tone at some frequency or even frequency sweep tests does not really come close to complexity of music. But at this point that is all I have. Good point about complexity yes it is more complex but the amp has been out there for a bit. And people who have it never seem to complain why it failed or how it faulted. Still I see these (amplifiers) as simple things compared to stuff I am aware of. These days manufacturing and design has come a long way with computer simulation etc. Testing techniques etc have come a long way. I am more concerned with someone in their backyard building a complex amp more than anything else.
Agree with you that good specs might not translate to good sound. But I cannot go on some one saying some monster class A/B or class A sounded great and since it is big and consumes a lot of power I have to go for it.
I have a class A SET tube amp and I am going to compare with this amp along with class D (Hypex NC500) before making my mind up on few things. I am in the bucket of people who think all good amp sound the same.
At the end can an amp just amplify the source faithfully and get out of the way. Can it just get out of the way!!. This is what I am going for and I want it at lowest price possible.
Suggest me few amps better than AHB2 at this price and I will consider them, I am only looking for a great amp that do justice to my speakers. I don't have any past baggage or any biases.
Suggest me few amps better than AHB2 at this price and I will consider them, I am only looking for a great amp that do justice to my speakers. I don’t have any past baggage or any biases.
I did, a pair of used John Curl Parasond Halo JC1’s in high bias class-A mode on your speakers will sound majestic. I heard them on Wilson Alexia’s and they were just a little behind the Gryphon Antillion Evo. And they come with 5 year warranty.
@geek101, just so you'll know (in case you don't), poster ramtubes is Roger Modjeski of Music Reference, designer and maker of tube electronics. Asking him for an amplifier recommendation puts him in an awkward position ;-) .
Ramtubes, could be my terminology is off, but if a loudspeaker has a built in power amp for the bass drivers and separate inputs for an external amp to drive the midrange/treble, then it requires bi-amping.
Ramtubes, could be my terminology is off, but if a loudspeaker has a built in power amp for the bass drivers and separate inputs for an external amp to drive the midrange/treble, then it requires bi-amping.
We really shouldnt have to be doing all this guessing. I wish the OP would tell us more about how this speaker is set up in his system.
I think he has the preamp/processor that goes with this speaker. If one looks at the back panel there is an XLR jack to drive the plate amp. There is one one pair of speaker terminals for the rest of the speaker so it cannot be biamped without going inside. What I do find curious is: If you do not have their preamp, which is featured on the website, then where are you supposed to get the signal to drive the XLR?
If a speaker has a built in power amp for the sub, no other amp is required there. It wants a line level signal. So there is no biamping in this case. One could s
Many speaker makers, Vandersteen and others provide two pair of inputs that can be biwired, biamped or simply strapped for one amp. That is when biamping is possible. Some choose different amps in that situation as the upper speaker often needs less power than the lower (regardless of the sub). So a big SS amp on the bottom and a nice tube amp on the top.
There are many of us who feel small amplifiers sound better. The sins that are committed in making a large amp will cause the lower power range to suffer. As an amplifier designer I happen to agree.
That is why the FTC stepped changed the rules in the 70's. Before distortion could be specified at full power where it is often lowest (in SS amps). At low levels there was often large amounts of crossover distortion. So they changed the rule to quote maximum distortion from 0.25 watts to full power. I would further reduce it to 0.000000025 watts to full power. We dont want distortion to climb at the bottom of the range.
It bothers me there is no sub control. Makes me think you have to buy their pre.
It bothers me there is no sub control. Makes me think you have to buy their pre.
I think the plate amp get a high level signal from the speaker terminals, and the xlr connection (room correction) may have something to do with this I found on line. And there’s a passive xover illumination lamp switch, so you can see it through the side grills??, how tacky. https://ibb.co/cKhCx0
https://hometheaterhifi.com/wp-content/uploads/2014/11/legacy-aeris-floorstanding-speaker-fig3-lg.jp... "The bass section is powered by 1,000 watts of included ICEpower® amplification and offers exceptional extension to 18Hz. The included 24-bit DSP room correction features balanced analog inputs and outputs for optimizing performance. The upper portion of the speaker cabinet is open air dipole for fast decay of mid-bass frequencies and airy spacious highs. The elegant design employs a 2.25” thick baffle with 2” side walls. LED Crossover Illumination within the upper portion of the cabinet reveals the intricately wired crossover design."
If I understand correctly Legacy Wavelet when used with Aeris at build time is configured to correct/adjust for the small errors among how different drivers work and also corrects for room also in the domain of time. I do like the idea of using dsp to correct these errors. I think from what I have heard in person it works well. No speaker can make the room go away!.
Buying passing Wavelet and the internal crossover is not an option, I think they add quite an amount of value.
As I said before in an another thread, if I could redo this it will be an all active speaker. The more expensive ATC look quite good to me. I want active crossovers and internal amplification. No need for this amp matching speaker merry go around.
@ramtubes The tube amps you guys make look quite good.
Legacy Wavelet and Aeris are an integrated system.
Meanwhile... Some ears at Stereophile are hearing the same attributes from the AHB2 as I have. Two honors each for the Benchmark DAC3 and AHB2. Kudos to Benchmark.
I think you’d be hard pressed to find a better sounding amp period, much less for the money. I auditioned a number of amps through my dealer who had 20.1s in a show room with various amp configurations over the years including some uber expensive equipment such as Boulder 3050 Monoblocks. I read about the innovative design of the Bencmark amps and gave them a try. I don’t plan on ever letting them go. I now hear only the music recording rather than the equipment which I feel we audiophiles get caught up in more often then not. I have my 20.1 Maggie’s bi-amped with Benchmark amps and can get much louder than I can comfortably listen before I run into clipping. They both run in stereo mode . . . Geek101 I think you’d be impressed with the output of one amp and would try it before getting a second. That being said, it’s your system and John has said that two mono amps will work well. Please tell us what you think. It would be nice to hear your experience of driving the system with one stereo vs. dual mono Benchmark amps.
I am running a small tower that is 89dB and 4 Ohm, and two of AHB2 in Mono with Exogal Comet and Plus Power Supply take 90 of 100 setting sometimes at listening level. This is no issue for the Comet or the amps, but with less efficient speakers you might bump into a barrier with listening level and amp output.
As I stated in my review the amps do not pull off absolute power for any and all speakers with unlimited listening level. Know your speakers and know your preference. Now, having said that, I would guess that in 90% of the cases, perhaps more, this is not an issue.
What remains rock solid is the control, cleanness, tonal richness etc. from class AAA. It's simply a great design. BUT, you must work with cables to elicit the best result you are seeking.
The DAC3 is very good as a preamp. Tends toward lean and light, not a thick, warmish pre like tubed preamps. Again, cables make the difference in so many rigs. The Exogal Comet with AHB2 is a bit warmer, and the DAC3 a bit cooler, but both are superb with the amps.
I have a pair of AHB2s. My speakers are 6 ohm nominal and not sure where they dip to (Tempo Electric EP-1).
However going form one amp to two, was relatively dramatic in my opinion, and I would recommend it. If you don't love it, send one back.
I didn't do it for the watts, as my speakers are 91 db sensitive and were designed with lowish power tubes in mind. I also listen very much in the near field, so again, not really looking for more watts. I was looking for the benefit of one amp not having to share a power supply, and more ease tot he sound. What I got was more realistic sound, larger sound, and an overall increase in sound quality
No answer to the above claim. All I can say to that is "if correct", that Benchmark should never have released this amp in stereo form, they should be all bridged, as the Stereo version is in some way hobbled and should not be purchased.
And there is no parameter that’s improved with bridging with this amp, except for and increase in wattage, and as Roger Mojeski said "it’s just a sale gimmick to sell more amps".
Lordcloud is not making a claim (an assertion without evidence). He is sharing the experience of using the AHB2 in Mono mode.
George, let's suggest someone bought two parasound bridgeable amps, and they said they sound better in Mono mode than biamping. Would you suggest that Parasound bridgeable amps are a sales gimmick to sell more amps, and Parasound, "should never have released this amp in stereo form, they should be all bridged, as the Stereo version is in some way hobbled and should not be purchased."
I'm checking for consistency. Imo you are making claims far beyond that of biamping versus bridged operation, suggesting that the AHB2 has been poorly designed or intentionally hindered to sell more units. To date I don't think you have provided one shred of evidence to support such claims. Frankly, I think you are walking on very thin ice with such claims against Benchmark. :)
There's a bit of anti-bridging hysteria on this thread. I've run bridged, vertical bi-amp and regular and the idea that bridging is necessarily bad is silly. Current certainly doesn't go down in bridged mode. Watts are volts times amps and volts = amps times impedance. An amp that can put 100 watts into 10 ohms, say, means that it is putting 3.33 amps at 33.3 volts into the speaker. If you bridge it and get 200 watts into the same load the current has gone up. In this case the formula for current is the square root of the watts divided by ten. The current for 200 watts is the square root of 20. For 400 watts it's the square root of 40, etc.
Keep in mind, too, that the amp is only driving one speaker so it's not working as hard for the same volume. There is certainly the potential for problems with low impedance loads but I've never experienced it. I'm running two amps bridged mono into 4 ohm speakers now, have been doing it for 6 years and have never had a problem. I like the option of being able to buy a second identical amp if the first one is a little underpowered.
How much power the amp can actually put out will vary. My point was just that bridging increases the watts an amp can deliver to a speaker and increasing watts means increasing current.
Benchmark clearly states in it’s specs: Not bridged 100w into 8ohms 190w into 4ohms =Clearly very close to doubling it’s watts, good current
Bridged: 380w into 8ohm 480w into 4ohms =Nowhere near doubling it’s watts, current diminishing.
Clearly the "not bridged" AHB2 is pushing current better because it’s closer to doubling the wattage into 4ohm, and therefore keeping the amp FR flat into varying speakers loads and not sounding like a tone control. Like the bridged would, regardless of how many more watts it has up it’s sleeve.
It is also possible that 480W limitation comes from power dissipation of the output or power supply (29A max current seems adequate) and is not relevant, unless one listens to continuous sine waves. Music has very low average power while peaks might still reach close to 800W.
I would bet looking at the wattage's I posted before, the "wavy black line" in the graph above, would be far more wavy with the bridged than the non bridged. But were’re never ever going to see that with the same test equipment now.
The Stereophile graph referenced above is done at 2.83V which is equivalent to 1W/8ohms and 2W/4ohms. Obviously, whether bridged or in stereo mode it won't be effected by any insinuated current limitation. What will effect the simulated speaker load is higher output impedance - which is doubled with the bridged amp - but because its already usefully low this won't make a substantial (read audible) difference. It certainly won't turn the bridged AHB2 into a tone control - which is a ridiculous exaggeration - especially in comparison to any tube amp or many other SS amps for that matter.
An amp that can put 480 watts into 4 ohms can put 240 watts into 8 ohms so it can double from 240 to 480. You can just think of it as an amp that puts 240 watts into 8 ohms and doubles into 4. Its ability to put more than 240 watts into 8 ohms isn't that relevant. Regardless of how you think about it, the amp delivers more current in bridged more. At any given volume the bridged amp will have better current capability. At 100 watts into 8 ohms it can double to 200 into 4 and again to 400 into 2 ohms since we know it can deliver at least 480 watts total. A speaker is a passive component so obviously increasing the power delivered to it increases the current. How else could it be?
The issue here is not the amplifier. It is the speakers. If you want high quality and high fidelity then 4 ohm nominal speakers are definitely best avoided. The very low impedance is bound to create amplifier issues (stress) with almost any amp.
You can't double voltage without also doubling current. volts = current times resistance. 29 amps into 8 ohm speakers would be 6,728 watts. That is instantaneous and not remotely sustainable, obviously. Actual sustainable current is directly related to watts. More watts means more voltage and more current flowing.
jon_5912, Yes, current will double when you double voltage, but you stated that current CAPABILITY (meaning max current) will be better. Current capability of AHB2 in bridged mode will be still 29A.
Assuming that you meant current (and not current capability) at given volume, it should state "at given volume knob position". At given volume (meaning loudness) bridged and unbridged configuration currents will be the same.
Max current will double. If an amp can double the voltage into a load by bridging then the current capability also doubles. I'm not sure what the max current rating really means. 29 amps into 8 ohms requires 232 volts. I'm pretty sure that isn't possible. Maybe it's theoretical short circuit current or something.
Maximum current won't double. (It will be still 29A). Maximum current is an absolute maximum that amplifier can deliver. This specification shows amplifier's ability to drive difficult low impedance loads. It says that when 4 ohm speaker's impedance drops to 1 ohm amp can deliver 29V peak.
Also, I'm not sure where specification 480W/4ohm came from. My manual (version G), as well as their website, shows 480W/6ohm bridged and 130W/6ohm unbridged. 480W is not that far from theoretical 530W for ideal voltage source.
The maximum current that can be delivered into 8 ohms or any other load will double when the voltage doubles. I obviously wasn't talking about the 29 amp "Maximum Audio Output Current" as specified by the benchmark website. We were discussing current capability into varying typical speaker loads. The maximum continuous current capability into 8, 4, whatever loads will increase when an amp is bridged.
George, there is no current sag. More watts mean more current. You are overestimating the importance of doubling into 4 ohms. It's not important in this case. What is important is how much power is available and how an amplifier handles various loads. If you lowered the gain on the amp so that in bridged mode it would only put 240 watts into 8 ohms it would still put 480 watts into 4 ohms. It would be doubling but would have the exact same current capability it does now. The issue is just that when you double the voltage you also double the current so the power is multiplied by 4. You just shouldn't think of the bridged total watts into 8 ohms the same as unbridged. Think of it as doubling the power. The bridged Benchmark will deliver 200 watts at 8 ohms and 400 at 4 ohms. It will actually put out more than that at both 8 and 4 ohms but you still get twice the power at 8 and it doubles that to 4. What's not to like?
bridged will be as flat or flatter at every volume that unbridged is capable of. Obviously. Bridged can put out 100w into 8 ohms, 200 watts into 4 ohms and 400 watts into 2 ohms. There will come some volume that is much louder than unbridged is capable of where bridged will start having problems keeping up. That isn't relevant to most people, though. Most people aren't running bridged because running stereo won't get loud enough.
Sorry your are correct it’s 6ohm as 4ohm they could not test, obviously current limited at 18amps and shut down, still not great 18amp shut down in bridged mode. And still 100w short of doubling into 6ohm anyway, still current sagging, should be around 570w not 470w
Benchmark specs given to Stereophile.: " Output power, bridged-mono mode: 200W into 16 ohms (26dBW), 380W into 8 ohms (25.8dBW), 480W into 6 ohms (25dBW). Output current: 18 amps/channel, both channels driven, 18 amps shut-down threshold."
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