ramtubes
It appears you may be confusing gain with power as many do. He is, by me too. douglas_schroeder The amp is FAR superior sounding in bridged mode regardless of the speakers used, efficient or less efficient.
I ask again, then why sell it in stereo mode if it’s so hobbled in stereo mode??? You should then be suggesting that no one buy it for stereo mode listening there are far better offerings. douglas_schroeder
I have said several times previously that there is NO sonic degradation in bridged mode, nor distortion associated with running the amp full out. This is a furphy, I didn’t ask that half a page back, I asked a simple question of amp sound quality driving the Kingsound III it was ignored. I present it again. "How did one stereo amp sound to a level it was totally comfortable at. Then the bridged ones at the same level?" "To gauge which sounded better." "NOT WHICH COULD GO LOUDER!" I think it all needs "paralleled interconnects attached to each channel", that should fix the problem/s. Cheers George |
ramtubes
I think Benchmark has done an excellent job of convincing everyone to buy two. Got a feeling there’s a couple of latent shills helping out too. Cheers George |
I had mentioned in my review that the AHB2 is not able to drive the Kingsound King III electrostatic to an unlimited level of listening. However, there is no degradation of sound as the amp is pushed to its limit, and there is no degradation associated with mono use. How did one stereo amp sound to a level it was comfortable at, and then the bridged at the same level? To gauge which sounded better. Not which could go louder! Cheers George |
Perhaps 18A specification was for the early versions. R Yes of course they were, just like when Sterophile does a mediocre review, the manufacturers comments always say they must have sent a faulty one in for the review. Wouldn’t you think at they would send the best possible tweaked one they could!!!! What a load of **** Cheers George |
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."
Cheers George
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Using the manufacturers own specs there's no refuting the current sag.
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.
Would be even more interesting to see independent measurements done.
Cheers George |
To put it more simply for the nay sayers.
If this "bridged" amp is ask to give 380w when the speaker is at 8ohm and can only give 480w when it dips to 4ohms it is clearly current sagging.
If that same amp "not bridged" can do 100w when the speaker is at 8ohms and can then give 190w when it dips to 4ohms it has almost no current sag.
I ask the nay sayers, which is going to remain flatter in frequency response driving those speakers????
Cheers George |
What would have been good to see is this simulated speakers load graph which is "non bridged" vs the bridged on the same simulated speaker load graph. Non bridged is good showing good current ability. https://www.stereophile.com/images/1115BAHB2fig01.jpgI 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. Cheers George |
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. Cheers George |
Sorry: Can't talk yourself out of that one sunshine.
Cheers George |
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".
Cheers George |
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." Cheers George |
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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. Cheers George |
geek101 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. Cheers George |
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. https://forum.audiogon.com/posts/1646450Trouble is his terminals don't allow it! Cheers George |
In contrast, the JC1 (suggested by George) produces 0.15% THD at full output What fool, sorry no, idiot! would run these massive Halo JC1 powerhouses at full output. Here are the real figures into 4ohms. "Distortion was also acceptably low (fig.6), with the 1kHz difference component lying at -94dB (0.0015%). Note that these last two graphs were taken at 635W and 600W into 4 ohms!" Also +1 for Rogers last post, and I’m also signing off this stupid merry go round. Cheers George |
I’m kicking back listening to my bridged mono AHB2’s :) And there it is, protecting ones self interest regardless of the facts for others. Yes you need bridged ones with your speakers (attached). But the OP does not, and he’ll get better sound with just 1x stereo one. ATC SM19 Lab Report " Average sensitivity (considering measurements in octave steps between 125Hz up to 16kHz) is close to 83dBSPL/2.83V/1m, a performance that undoubtedly classifies the SCM19 as a low-sensitivity loudspeaker," "SCM19’s impedance magnitude variation is quite small for frequencies above 100Hz and as an amplifier load is -for all purposes- constant. The minimum value of about 5.6 Ohm appears near 150Hz and allows us to conventionally consider the loudspeaker as an 8-Ohm load, although -typically speaking- a correct designation would be 6 Ohms. Below 100Hz, impedance magnitude significantly increases up to 50 Ohm, a behavior which could affect amplifiers with low damping factors. Also, phase behavior, ranging from +47° to -57° could be quite punishing for small amps." http://www.avmentor.net/reviews/lab/2016/atc_scm19/display/atc_scm19_impedance.jpgCheers George |
My questions are answered. I am in the process of getting a second amp. Thanks.
Total $6K. Pity for that you could of got a pair of John Curl designed Halo JC1 monoblocks that would eat these bridged AHB2's for breakfast. They "unbridged" output
400W into 8 ohms, 800W into 4 ohms, 135 amps of peak current, and 25W of pure class-A power into 8 ohms. JUST SAYING! Cheers George |
tobes
Really?
Lets look at that. Show me where it states about and using the words "distortion being the same" in bridged mode into a 4ohm speaker, which means it’s seeing a 2ohm load? I doesn’t, and it’s a furphy! https://www.google.com.au/search?q=furphy&rlz=1C1CHZL_enAU820AU820&oq=furphy&aqs=chrome....But like Roger Modjeski "ramtubes" said, it’s a great spiel to be able to sell two amps with. Even though the user will go backwards in sound quality if he didn't need the extra watts. Cheers George |
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My speakers can only dip to 3.8 Ohm minimum.
That means the amp/s in bridged mode will see a load of 1.9ohms, not good for the bridged, but fine for a single stereo amp.
Sure two AHB2s may be overkill for my speakers
Yes as I told you before, with a single stereo you will not only get better sound, but be able to reach with your speakers in room at 3mts, 110db!!!! Enough to blow your eardrums out. Cheers George |
No matter what sort of spin you want to put on it
tobes the fact is that this thread is about the OP and his speakers, and bridged AHB2's are not the way to go into his speakers 4ohm load.
"Bridging good for more watts, but everything else takes a hit."
Cheers George |
If we put aside the term "damping" , because thats not what really matters, we need to inform people that an amplifier with high output impedance may cause a marked change in the frequency reponse of their speaker. Thats what really matters.
Yes add that to the other cons, the amp starts to behave like a tone control. (ie: not flat from 20hz to 20khz) Cheers George |
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I imagine in the 4 ohm bridged mode the current limiting would become apparent. JA is often kind by omission. I think the amp would shut down with a 4 ohm bridged load. Thats like 2 ohms per channel as you well know. Yes and before it shut down, the distortion would be higher than the 8ohm they did give. I am just amazed at how well Benchmark marketing has pulled off selling 2x amplifiers. Great marketing, all in the wording and the omission of certain measurement graphs. I understand there is some power supply wonderfullness going on.
Yes, like Krells Plateau biasing except done on the voltage rails instead, Quad 405 I think used something similar, and maybe Devialet Class-D amps do something similar also. " Output voltage is variable by a factor of 8 from +/- 10V to +/-80V and constantly changes to minimize overall thermal dissipation." Cheers George |
You believe what you want, and I'll believe what I know for the OP's speakers, and that's what this thread is all about.
In general Bridged Amps
Pros=
More watts.
Cons=
Worse damping factor
Higher output impedance (has relevance to damping factor)
Lower stability (especially into low impedance's)
Current ability is reduced
(especially into low impedance's)
Higher distortion.
Cheers George
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djones51
George I don’t really see why 1 amp in stereo wouldn’t be enough with the OP’s efficient speakers Been there, done that. https://forum.audiogon.com/posts/1647982and here https://forum.audiogon.com/posts/1647933
But he seems to want 2 amps to try in bridged mode and from everything I have read on this amp it can do it.
Not really into 2ohm which is what the amps will think their driving (bridged) and then there's the disadvantages with bridging that I and many on the net outline. If there was no disadvantages then we'd all be using and selling bridged amps. Cheers George |
In my case the bridged AHB2 amps do sound better than a single AHB2, but my ATC speakers are very different from the OP. Yes because your speakers need the extra watts, the OP’s don’t, and that’s what the discussion is all about. I would lay money on it, that if your speakers didn’t need those extra watts, you’d be saying one stereo sounds better that two bridged, regardless of the cost saving. Roger Modjeski (Ramtubes) a few posts back has also tried to say similar. Cheers George |
georgehifi, my question was in the form of yes/no.
Are you speculating, or do you have actual experience with the amp in different configurations? I repeat, If you have a technical background and understand what happens when you bridge an amp, you wouldn’t be asking this question. Cheers George
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They promote bridging so they can sell you two amplifiers obviously.
geek101 OP seeing I gave many other cons and hardly any pros, glad someone else said this, I held off that one, good one Roger now I don’t have to bring it up. Cheers George |
geek101 OP
Legacy Aeris is spec’d for 500w.
Probably peak also. Here’s your spl at 3mts in your room for a stereo AHB2 seeing a 4ohm load (210w) into your 94dB effcient speakers. 110dB spl! say good-by to your hearing. And "if" they were 8ohm 94dB speakers and your amp would give then give 105w your still at an in room SPL of 107dB!! still ear shattering!
To my limited knowledge even after bridging Benchmark seems to out perform its peers.
If this were the case, and there are no downsides as I've explained, then why not just have bridged amps if they out perform in all areas. Cheers George |
geek101 OP BTW geek101 OP your Legacy Aeris I just noticed are 94db!! why do you need more than one AHB2, one is plenty and will do the 4ohm load on it’s ear, and not have any disadvantages of it bridged. A bridged one beside all the cons I mentioned, will be looking at a 2ohm load and if that speaker has high -phase angles at 2ohm impedance dips, it could be even lower as seen by the amp. Cheers George |
Are you speculating, or do you have actual experience with the amp in different configurations? If you have a technical background and understand what happens when you bridge an amp, you wouldn’t be asking this question. Cheers George |
I’ve tried geek101 with links to pro and cons and every which way, the site and manual, and post you’ve presented are just too ambiguous. Purchase another one I hope for your sake two bridged amps can do it as good as just one bigger non bridged amp can, I seriously doubt it. Cheers George |
geek101 OP
Any thoughts?.
Yes! believe me? it’s in the wording, you need to read like a tech to find the tricks, as this is very misleading to the novices, as the last two distortion figures are NOT I repeat NOT in bridged mode, but measured one mono channel only. Then find the output "current rms" output for a single channel and then what it does with two channels in bridged mode. And you couls also do peak current for both. Then find the damping factor single channel and compare to bridged. Also the output impedance for both, which is in relation to damping factor. Cheers George |
kijanki3, we still don’t get the full Bridged spec picture. There are no specs accompanying these copy/pasted excerpts you put up, again misleading, if you are referring it back to the other figures on the other page that geek101 put up. Lets see both distortion graphs
THD+N and THD for both bridged and non bridged into 4ohms or less. This will be the true test of what the OP wants to do. Cheers George |
It’s clear that you Benchmark bridging "experts" have no idea what happens to a stereo amp electronically when it’s bridged.
Guarantee whoever spends the bucks and does it here, will be back asking for other alternatives after they lived with their bridged amps.
When they’ve realized it was a backward step from using the same amp non bridged, even though it didn’t have the watts to go loud enough.
And they’ve realized all they gained was watts, and everything else sound quality wise took a hit.
Cheers George |
Now I just have to decide if I need to buy two amps or just live with one.
Just Google and read the technical explanations from technical backgrounds of the "disadvantages of bridging stereo amplifiers" Cheers George |
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geek101 OP203 posts11-10-2018 11:56am@georgehifi I cannot bi-amp since Legacy Aeris has the low frequency section already powered.
That a pity, would have been perfect, if the upperbass unit had it's own speaker terminals, and the mid and highs their own. Anyway I would not bridge the amps to get more watts, for the disadvantages I listed above. I suggest you get bigger amps, good value are the John Curl designed Halo A21+ 300w or the Halo JC5 400w. Cheers George |
geek101
Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker I would never bridge an amp all you gain is watts, distortion goes up, damping factor is reduced, stability into low impedance’s is reduced, and current ability is reduced. "Basically" you turn a good amp into a high wattage P.A. amp. If your speaker terminals allow it, and you have two "identical stereo amps" like 2 x AHB2’s, you should vertically bi-amp each stereo amp to each speaker. http://www.av2day.com/wp-content/uploads/2014/05/biamp2.jpgThe reason these guys preferred vertical bi-amping over horizontal bi-amping, is that the powersupply in each amp can be totally accessed by just one bass driver channel when needed for the biggest dynamics. http://av2day.com/2014/05/bi-amping-vertical-vs-horizontal/Cheers George |
