You only need one pair of cables. One per speaker.
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Review and Measurements of Benchmark AHB2 Amp
- Thread starter amirm
- Start date
You only need one pair of cables. One per speaker.
I may go back to the single stereo setup if the mono does not float my boat so I will need the 6 foot pair to reach the speakers from a single AHB2. When I try the monos I will need a pair of 3 foot or less cables. I will buy a used 6 foot cable and chop it up.
There is no audible difference between 6 feet and 3 feet of 4S11 cable. If you want to cut the length for neatness then I’d reterminate the banana end as I’ve found the SpeakON connectors are tricky with 11 gauge cable.
Last edited:
Edited for accuracy. ;-)
Coach_Kaarlo
Active Member
Ha. Ha.
in fairness I have been able to reproduce the results. But unable to measure the clearly audible difference with a Unimik and REW. Some high speed photography or laser measurements might.....
Joking aside, I seriously question the "clearly audible" statement.
However *** disclaimer *** I am personally convinced that all speaker cables (barring esotic, badly designed ones) sound 100% indentical and are completely indistinguishable from one another in any properly controlled testing.
Coach_Kaarlo
Active Member
Ok I will bite. You question the "clearly audible" statement because you have conducted the same tests and measurements with the same equipment in a similar environment as I have, and come up with a different result?
Or you question it because YOUR personal convictions (biases) makes you think something is always true?
It's not the cable brand or price which makes a difference. It is the physical properties of the cable - AS THEY RELATE TO THE ENTIRE SYSTEM.
Amplifier; damping factor, dynamics (slew rate, voltage rise, max. instantaneous current), rated static power
Speaker; actual min. impedance value, physical properties (mass of moving parts, current req'd to move coil, etc), sealed or open
Cable; resistance, capacitance, insertion loss, length, termination quality
So I can agree that GENERALLY changing the type of speaker cable makes no difference to the "sound", and with properly controlled testing they are indistinguishable from each other when only the cable is changed.
However, small changes in the cables electrical performance & properties, and physical & mechanical properties CAN affect the performance of the entire system in a way which is predictable, repeatable, and audible. Changing the other parts of the system and using the same cable CAN also produce differences.
I have attached some specs for the cable Benchmark Media use - they clearly show the effect changing one parameter in the entire system (cable length and type) has on the damping factor.
Couple an amplifier with a low damping factor, a low slew rate, and slow rise time, and limited current delivery (AHB2) - to a heavy coned, big magnet, and low impedance speaker. Then make the cable long or very short and see what the reproduced sound is like coming out of the speaker? Seriously, try it for yourself instead of reading / typing comments on here.
What you will observe is a failure at some point for the woofer cone (hardest one to drive) to accurately track the signal, both out and back in (rate of movement, and travel distance). What has been interesting is that changing the speakers made such a difference to the performance (ability to accurately reproduce the signal) of the amplifier (all amps sound the same?). I can infer that when I see an impulse response like the one below, that the speaker driver is more efficient, and therefore easier to drive with the AHB2.
As far as the cable goes it affects the SYSTEM damping factor enough for me to ensure I am using a cable with very low resistance, and a very short length - particularly if using my 2 x AHB2's in mono.
Benchmark / John Siau produced a great spreadsheet to calculate this damping factor stuff for the WHOLE SYSTEM, try it out for yourself, small differences in speaker impedance and cable length make big differences to the ACTUAL damping factor. AND with sub optimal system equipment combinations, an audible, reproducible, and measurable (with decent tools) difference CAN be observed.
Oh and in the interests of full disclosure (possible uncontrolled variables) I should add my hearing isn't amazing, but ok at low frequency (eyes still work well enough to observe differences in cone extension tho);
Last edited:
OK, I will bite back.
Just because something might be electrically infinitesimally different as measured by laboratory test equipment, is not proof that the human ear - an organ which massively less capable than such devices - has any chance of detecting these changes.
It's like the businesses trying to convince people that 24/192 sounds better than 24/48 or 24/96, for example, when the human ear has no chance of hearing anything above 20 KHz, and for the old fogeys like me who follow this nonsense - probably not much over 15 KHz. Or the silly "stepped sine wave" trying to show how hires audio is better, when no steps exist in lower res audio anyway. It's quack science.
The entire industry is jam packed full of such guff, seeking to explain audible differences which do not exist. And I can see why, to admit that they do not would be the demise of a multi-million (billion?) pound business scam.
I am quite sure some people are convinced different speaker cables sound different. That of course is their prerogative. As it is mine to be 100% certain in my mind that they are fooling themselves and that they are wrong.
(I am not talking about edge cases with extremely high capacitance cables or 1000 ft cables or what have you. I am merely suggesting that a bog standard pair of Canare 4S11 will sound INDISTIGUISHABLE to some esoteric nonsense costing 10x, 50x, 100x as much. It is snake oil, pure and simple.)
Last edited:
This article gave me pause. I’d been considering a replacement of my older Bryston 4B-ST for a 4B-SST2 or a AHB2. Now, I’m skeptical of the real audibility of the change. That’s precisely why I come to this forum.
Pdxwayne
Major Contributor
- Joined
- Sep 15, 2020
- Messages
- 3,219
- Likes
- 1,172
I asked about the speakers used but got no response.
Those are speakers with "powered" woofers.
"....
Featuring a 15-inch (CLS™) XStat™ electrostatic transducer, dual 12-inch PoweredForce Forward™ woofers powered by dual 500-watt Class-D amplifiers, and controlled by a 24-Bit Vojtko™ DSP Engine and ARC™ (Anthem Room Correction).
...."
When 200 Hz and below are handled by internal power amps of the speakers, what exactly are we testing?
But, you know you WANT an AHB2.
Archaea
Active Member
I told you what the speakers were in the write up.
We’ve done this test three times now. With different amps. With different enthusiasts. With different speakers. So far, same results. Each time someone says we used the wrong speakers for the test. JTR 212HT, (too sensitive). Klipsch Reference towers with a pair of 8” woofers (not high end enough). Martin Logan Renaissance 15A. (Has powered subs).
The Martin Logan speakers we used are notoriously difficult to drive. I feel we’ve had a good sample of speakers so far in our 3 rounds of testing — certainly covered a few of the popular designs and extreme ends of sensitivity.
What are we testing? Real world listening scenarios with blind testing and immediate A/B/C/D carefully level matched amplifier switching.
It’s fairly impossible to please everyone. There’s always sand to throw in this playground.
Take, or discard, what you want from our testing.
Last edited:
Pdxwayne
Major Contributor
- Joined
- Sep 15, 2020
- Messages
- 3,219
- Likes
- 1,172
In all 3 cases, you are not stressing any of the amps.
How about testing just normal non powered speakers, less than 90 dB sensitivity for a start? One that has reputation of reveling the upstream problem.
Play something bass heavy, loud, like 85 dB average and 90+ dB peak, measured at your seats?
Here is one song example:
Last edited:
- Joined
- Oct 11, 2018
- Messages
- 3,741
- Likes
- 6,457
I can think of absolutely no good reason to ditch a perfectly good Bryston amplifier.
As far as the linked test, it is what one would expect. There are valid (i.e. practical electrical) reasons one might have to prefer one amp over another. With highly sensitive loudspeakers, hiss might be evident on quiet passages with one of the noisier amps. If your loudspeakers dip into the bottom ohms and stay there, and are hugely inefficient, you'd want one of the beefier amps able to crank a lot of current.
Once you get past that, it's preference. Do you desire cutting edge tech that pushes the limits of engineering? Do you need a strong warranty? Build quality? Cosmetics? Blue meters? Bang for the buck? All those reasons are important, but will have nothing to do with what you are going to hear.
What these sorts of tests show of course is that all the 'audiofool' reviewer nonsense you read is just that. On the other hand, once you get into the fringe stuff (SET, Ampcamp toys, and other really low powered/high distortion devices that aren't suitable for much of anything) YMMV, from a sonic standpoint.
I told you what the speakers were in the write up.
We’ve done this test three times now. With different amps. With different enthusiasts. With different speakers. So far, same results. Each time someone says we used the wrong speakers for the test. JTR 212HT, (too sensitive). Klipsch Reference towers with a pair of 8” woofers (not high end enough). Martin Logan Renaissance 15A. (Has powered subs).
The Martin Logan speakers we used are notoriously difficult to drive. I feel we’ve had a good sample of speakers so far in our 3 rounds of testing — certainly covered a few of the popular designs and extreme ends of sensitivity.
What are we testing? Real world listening scenarios with blind testing and immediate A/B/C/D carefully level matched amplifier switching.
It’s fairly impossible to please everyone. There’s always sand to throw in this playground.
Take, or discard, what you want from our testing.
How were you able to level match with instant switching between 4 amps?
- Rich
Archaea
Active Member
As described in the write up under Setup: Post 8989.
https://www.avsforum.com/threads/ka...e-night-events.1496367/page-450#post-60198218
Here's a snippet, but there are more details in the original writeup under that section...
We disengaged Audyssey, all tone trims, restorer, and any form of EQ. We set all speakers to large to remove any crossover. From the prepro we used three height channel pairs, and one surround back pair as our four source channel pairs. We put the Marantz 8805 flagship prepro to multi channel audio (all channel stereo) to do the testing so we knew each channel pair had the same source.
We used my omnimic and a micstand by the listening area to level set every entries' left and right channel to 80dB via the receivers internal test tones. The most variance we saw in any channel was .2 to .3dB. (since the increments were in .5 with the Marantz channel trim that's the closest we could get). With each amp level matched via Marantz channel trims, the overall master volume could cater to the listener's preference.
We re-used my trusty home made DIY amp testing setup from our first 2013 amplifier comparison. Each amp connection uses an identical amount and type of speaker wire, less than 40' of speaker wire which is inaudible at both 4 and 8 ohm according to the Roger Russel wire table).
http://www.roger-russell.com/wire/wire.htm#wiretable
The double pole light switch DIY switching mechanism I made has 8 switches - two switches per channel (L&R) you completely turn one pair off and turn the next pair on to change amp auditioned. You can turn them on in any order. All amps are constantly "hot"/receiving signal, but you are only listing to one amp at a time and you can simply switch as fast as you can flip a pair of light switches. If you turn on two pairs of switches at once, something fries since all amps are hot - fortunately we didn't run into that this time - and everyone was made well aware of that risk in advance of the testing.
Yes, presumably some level matching was required with one source, the AV8805.
If volume adjustment was required, then how much time was required to adjust the volume and where was it variable, depending on the source?
Where comparisons simultaneous with some listeners in the sweet spot and other not?
In the future, I recommend level matching with sine-wave and volt meter.
- Rich
Archaea
Active Member
Rich,
Once all the amplifiers were level matched we used the Main Listening Volume adjustment which in parallel raises or lowers all channel pairs and therefore XLR connected amplifiers. The auditioned got to choose any volume they wanted with the Marantz remote in hand (Though we agreed not to go above -10dB on the MLV as a precaution against source clipping since the individual channels were boosted into the +6dB +7dB range on a couple of the amps. (each amp had positive channel trims because of the low sensitivity ML Renaissance speakers)). The auditioner then could then switch amplifiers from the main listening position at their own whim as fast as they could throw light switches.
For the lesser portion where someone was controlling the switchboard out of sight for the auditioner (to test if any possible perceived preference from their time commanding the switching device would remain consistent when they couldn't actually see which amp switches were flipped) the tested auditioner was always in the MLP as well.
We used a voltmeter and sine wave sweeps in the original 2013 testing as part of our setup process, and it took a much greater amount of time to set up, but those doing the set up agreed after going through that process that it didn't matter in this specific type of audition/testing. Why? It's just one pair of speakers, with four amps connected to it and the auditioners goal is trying to detect a difference - if they can't, then the sine wave doesn't matter (also under the expectation the amps should be producing an absolutely identical frequency response sweep unless an amp is broken) IF OF COURSE - it was determined the auditioners could detect and reliably identify a difference consistently - - at that point we'd want to ferret out the difference. So that is simply a time constraint. We had agreed this would be a half day thing going in. Even still, it took us about 3 hours to carefully set up in a double blind manner - and then we auditioned thereafter for 2-3 hours.
Here's a video from our 2013 test. We didn't capture video this time, but this will kind of show you the idea.
Last edited:
Over the last 20 years, I have owned the following Bryston amps, 3B-ST, 4B-ST, 4B-SST, PowerPac 300, 7B-SST. I have also owned the AHB2. The AHB2 is smoother on top, you hear more details because the amp is insanely quiet, and no fatigue compared to the Bryston amps I have owned. Bryston does have more power in stereo configuration.
I also recently did a comparison of the Bryston BHA-1 vs the Benchmark HPA4 headphone/preamps on the same system. Again the Benchmark was smoother, more details, and no fatigue. I sold the BHA-1
The only Benchmark piece that I thought was fatiguing was the DAC1, unlike the DAC2 or DAC3.
Pdxwayne
Major Contributor
- Joined
- Sep 15, 2020
- Messages
- 3,219
- Likes
- 1,172
Of any of the systems tested, did you check the whole chain's transparency? And your ability to hear details in your sitting position?
For example, Diana Krall's "A case of you" from "Live in Paris" album has very obvious foot padal movements sound.
In the beginning of the song, can you distinctly hear the foot pedal movements, the padal press down sound with spring mechanism movements, and the letting go of the padal with a clean thud sound? All clearly at your listening position?
Can you hear the room reverbs, there are many, but one obvious one like around 1:50? From you sitting position?
Last edited:
Similar threads
- Poll
- Poll
