One thing I’ve noticed in reading his book and even in his posts is that his observations are for multi-seat listening. Yeah, while I will never have achieved the academic and scientific level of achievement, or renown, of course, that Toole has and deserves, I also come from a motion picture theater background, so I really love his writing and perspective. In the book, almost everything he has to say about low frequencies and subwoofer placement has to do with optimizing for multiple seating positions. I think this explains a lot about his own choices in home audio. I’m mainly concerned with single-seat listening. My home theater system is good enough for my purposes. I know it may not sound as relevant, but your fixes are _almost_ always the same. Controlling reverberation time for instance is something hard to do for one spot, without also controlling it in the rest of the room. Adding effective bass traps makes EQ possible. What Toole gets exactly right, IMHO, is that the concept of room correction is greatly oversold. attempting big corrections in EQ because your sound field sucks doesn’t end up with acceptable solutions for most. Let me explain with a common and specific problem. Let’s say you have a harsh or compressed mid/treble experience in a very live room. Measuring it hyper accurately at your seated position may flatten the curve, but it still won’t sound good. You will control the energy say, between 2kHz and 10 kHz, so it no longer sounds too bright, or too dull, but with long reverb times, all that signal is noise. It’s like watching a movie, where you get the right color and brightness but you can’t tell the actors and scenery apart. In the bass, with a bad room, the best you can do is clip peaks. Now, that may be a really good improvement, I've seen peaks that were the equivalent of 200x the power output vs. the rest of the system, and clipping them was a major benefit, which EQ can handily do, but trying to EQ these subs into a great response requires a sledgehammer like approach with major amplitude shifts in multiple adjacent bands which, may work for exactly one place and is not all that satisfactory a solution at the end. Fix your reverberation, and often, the tonal balance fixes itself, and then you are left with very mild, gentle corrections to make. Add bass traps, the peaks flatten themselves, the nulls stop being so severe and again, just a little EQ here and there can give superb experiences. Hope this helps, Erik |
Concerning headroom: Each channel of an early Bryston 200 wpc amp has a 375 watt transformer, two 4000 Mf filter caps and two outputs. The 125 wpc Audire has a 500 watt transformer per side, plus 4 26,000 Mf filter caps and 6 output devices. At loud volumes, teh Bryston loses some bass oomph. Later Audire gear uses many more outputs. When the power supply is big enough, the output transistors can regulate the current provided; when too small, they have to strain to get anything out, as Julius Siksnius of Audire discovered with his first amp, which had a one thousand watt transformer, and two much smaller filter caps, plus six outputs driving both channels, not one. Mine became a great sub amp, but the upper ranges sounded a bit taxed when playing really loud on full range speakers, but much less so than My Phase Linear 400.
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I mainly agree with everything erik_squires stated in his last post. My only disagreement is that in my practical experience, the use of 4 subs, properly positioned and configured in a distributed bass array (DBA) concept system, results in exceptionally good bass performance in most any room. Just as Dr. Earl Geddes scientifically proved with his PHD thesis over 4 decades ago.
There's also no need for any bass acoustic room treatments of any type when using this concept. Mics, room analysis and room correction equipment are interesting and can be utilized if preferred, of course, but I'm certain none of this was required in my 23'x16'x8' room to perform at a very high level.
On another topic that danvignau posted about, I'm failing to understand why having an abundance of amp headroom in an audio system can be accurately considered to be anything other than beneficial by Floyd Toole or anyone else.
As a practical but admittedly anecdotal matter, I drive fairly inefficient, 86db/1 watt, Magnepan 3.7i 4 ohm speakers with 2,400 watt/30 amp class D monoblocks with an abundance of beneficial results and no negative results that I've been able to discern.
Tim
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Correction, my monos are 1,200 watts each into 4 ohms
Tim
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I mainly agree with everything erik_squires stated in his last post.
My only disagreement is that in my practical experience, the use of 4
subs, properly positioned and configured in a distributed bass array
(DBA) concept system, results in exceptionally good bass performance in
most any room. Just as Dr. Earl Geddes scientifically proved with his
PHD thesis over 4 decades ago.
Sorry, was assuming 1 sub placement. I don't have a problem with this either. |
I think one area we should talk about is not power, but sag. I don’t have a better word for it, but I’ve seen speakers with low impedance, sometimes deliberately low impedance, sometimes unavoidable, sometimes the result of ad hoc experimentation, become "discerning." That is, they give off the impression that they are so revealing that different amplifiers now sound glaringly different.
I have come to believe, with limited data that the issue is not the amplifier’s power rating but how consistently it performs across the audio band, and this is a place where the math doesn’t quite live up to the audible effects. I find that speakers with drooping impedance have this characteristic, and that amps which _should_ be quite stiff and sturdy, are still susceptible.
So, I don’t think 300 Watts is a lot better than 200, or maybe 100. It’s the output impedance in the location of the speaker’s impedance droop that matters a lot more. The mythical Krell 50 W Class A which doubles in power down to 1 Ohm is a great example of what I’m talking about. It’s also mroe than I would use, but it helps illustrate what I think is going on.
Yes, big amps tend to have more output transistors, and therefore, lower output impedance, but it’s not the power rating that makes them sound better with some speakers.
Best,
Erik
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I have come to believe, with limited data that the issue is not the
amplifier’s power rating but how consistently it performs across the
audio band, and this is a place where the math doesn’t quite live up to
the audible effects. The problem isn't the math, its how the amplifier is measured which is something else altogether. Most traditional amplifiers (tube and solid state) that employ feedback don't/can't use enough, so as frequency is increased distortion increases too. This results in brightness/harshness, and is fundamentally at the tubes/transistors debate. To get around this problem, distortion is usually measured at 100Hz which is too low a frequency for the problems I described to show up. This has become a tradition, so there are those that do this and don't realize that its only done that way to sweep dirt under the carpet. The reason not enough feedback is used is that you need in excess of 35dB of feedback to prevent it causing brightness (distortion) through its application. This is because traditional amplifiers lack the Gain Bandwidth Product to really allow them the proper amount of feedback at 7KHz and higher. In addition, phase margin is a problem so amps with this much feedback can be unstable and go into oscillation. If you can run enough feedback, the amp will sound just as smooth as any tube amp running zero feedback. I think what you are describing is really just the amp showing off its limitations. |
Below is an email I just sent to the guy that did my ROON Convolution filter for my small room system. Since you are sound guy I thought you would find this interesting.
I was curious how the Benchmark AHB2 in mono would sound with my Thiel CS3.7, which likes power at low impedance. So I took my single stereo AHB2 and switched it to mono and drove only 1 speaker. It sounded louder and with more details. It also was much more hard hitting. I listened to Soundgarden: A Sides completely on stereo. I then kept everything the same and played the CD again but in AHB2 mono and single speaker. Even with a single speaker I had more bass. In fact the bass was so much that I had to change filters to the first one you gave me where the bass was not enhanced. After I changed from filter 3 to filter 1 my irritation subsided.
I was always curious whether more power at low to medium volume gives you better sound. For me it seems obvious that it does. I believe in mono the AHB2 gain is boosted 6 db however, I am hearing more than increased loudness. It is a better sound. I should add that the AHB2 SNR drops to 135 when the AHB2 is run in mono. That is not much different that the SNR 132 in stereo but I was hearing more details in mono. I think my Thiel gobbled up that extra power and made better sound and it was not the SNR that made the sound better. - Filter 1 was a Convolution file that was very flat. Now using with the single speaker running a AHB2 in mono (700 watts @ 2 Ohm) - Filter 3 was a Convolution file that had a slight bump in the bass from 100 Hz down. I was using this filter with the stereo AHB2 which does not have much power into 2 Ohm (259 watts). So yes, I am buying a second AHB2 to run in mono. Maybe Floyd was using a more efficient speaker. |
@yyzsantabarbara Thiel says those speakers, though rated at 4ohm, will go down to 2.8. With recommended power at 100w - 600w, I bet they spend a fair amount of time at or near 2.8. The AHB puts out 190 @ 4ohm, 240 @ 3ohm. I'm still learning here but I would say that's way underpowered for the Thiels. Have you considered a high output Class D? I believe @mapman is running Bel Canto Ref 1000 monoblocks after switching from a lower-powered Musical Fidelity and says the difference was night and day. I bet those would do wonders for your Thiels as well. |
@diamonddupree Those numbers you listed was why I am still investigating more power. However, I really wanted make the AHB2 work because I like it more than other amps (I have heard a lot). For less than $3K I think I will improve my sound a lot by going mono. Even though the AHB2 is not officially rated at 2 Ohm because it cannot run a test tone for 30 minutes at 2 Ohm (the AHB2 in stereo can). I think that is inconsequential now after my test yesterday. Even if it clips the forward correction will stop that from getting to the speaker. Since I have been investigating other amps. The 2 other lines I was considering are: CODA #8 - 150 | 300 | 600 (approx. first 18 watt class A but halved as impedance halved)
- 250 | 500 | 1000 (approx. first 12 watt class A but halved as impedance halved)
- 400 | 800 | 1600 (approx. first 8 watt class A but halved as impedance halved)
- SNR 118
CODA #16 with a SNR 130 and first 100 watt Class A. I think it's power rating is as follows,
150 | 300 | 600. The upcoming Class D Puriif amps with 1000+ watt in 2 Ohm. These ones maybe the closest sounding to the AHB2. I was also considering the Luxman m900u which is similar in spec to the CODA #8 (150 | 300 | 600) but 3x the cost. It sounds great and the only one I have heard from this list. I should be able to get a second AHB2 next month. |
@yyzsantabarbara a second AHB might not even do it. There's a pair of Belo Canto Ref 1000s available right here on Agon I think for less than $2k. |
ref1000s do not have custom input stage for best tube amp results nor beefed up power supply.....stock icepower. So may not be best still for a 4 ohm load or use with tube pre-amp if needed, ....even though 500 w/ch. You need somewhat pricier ref1000m for that. ref1000m is what I have been using for a number of years now and still sound very good. Drives every speaker I have thrown at it to the max (Ohm, Dynaudio, KEF) and never breaks a sweat. |
If you are looking into CODA, try the Sanders MagTech. Made by CODA with built in power supply regulation. The only other big amps I know of who have any sort of regulation are the Krells. I'm sure there are others though.
That was going to be one of my suggestions from the start, but I thought you wanted to stay with bigger brands.
Best,
Erik
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PS - When it comes to convolution filters and roon, I go 100% with Toole. I think they are too much, and if you want to go that flat, what is the point of your speaker brand to begin with?
With Roon, I prefer minimal EQ, using parametrics. It maintains the character of my speakers, reduces CPU demand on the Roon server, and does the least harm. Also, prevents over-EQing for 1 spot.
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@diamonddupree I should be happy with the sound I am getting from a single AHB2 now. However, if I was that type of person I would not be hanging around A'gon.
I have great synergy with my all Benchmark system now. Adding that second AHB2 will just move the needle to 11. |
@erik_squires When it comes to Convoluton filters what I have now was created by a rock star in the field, not by some random DIY’er who thinks they are an expert after tinkering around. This was done by a professional audio engineer doing this for 20+ years and has written a book on this issue. What I have now is the best tweak or upgrade to my system. I do not know if you hang out in the Computer Audiophile site but my filters were created based on info posted there. Some very knowledge folks on this issue over there. I am posting my findings here because most folks on this site are not aware of the possibilities with Convolution. My Convolution files was created using Audiolense which I understand is some very complicated software (Accurate is another option). It is also not free, like REW. I had to pay $200 for a 1 time license usage of the software by the outsourced audio expert. The implementation cost was another $500. Peanuts from my perspective. I paid more for an XLR interconnect and that had 0.00145% the benefit of the Convolution. What I solved was getting a big speaker into a small room and getting it sounding perfect. That was my goal from the start and mission accomplished. It took me 2 years to get to this destination from the start of this thread. https://forum.audiogon.com/discussions/big-speakers-in-small-room-at-moderate-volume-levels?highligh...With regards to ROON setup, I have a 2 computer solution. My client computer was picked out of the trash 5 years ago from an previous employer. My ROON Core server is a under $1K DELL refurbished machine. It has something like 20 cores and 32 Gigs of RAM. This is actually my weakest server in the house, I have about 10 computers in the house. ROON Core does not need that much power, even with Convolution. If you go to the ROON forums and ask the ROON developers there they will tell you the same. I had a buddy over to my office today. I had him sit at my desk and I played the music. He had the same reaction I am having, glorious sound. I have actually heard enough uber systems and other non-uber great systems to know that my system is now also great. |
I'm glad you are enjoying the results!!
I apologize I was thinking of the generic/common use of convolution filters with Roon, which most time is a thoughtless exercise.
Those same filters however can be used to make much more discrete changes.
My bad. :)
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Speaking of amps that will truly, "Double Down".
The only one's, "theoretically" that will, that I know of are the Pass "Aleph 0's".
I had a pair of the, "Aleph 2" but I never really ran them hard.
Very nice amps though.....
"Erik"?
You mentioned a "Mythical" Krell, 50 watt amp also? Do you by any chance mean the KHA-100 mono-blocks?
I have a pair sitting here. And cannot seem to find anything much about them. Large though. |
MC is very wrong again on many accounts. Headroom - this is where an amp can really shine in producing high instant peaks and crescendos. If any amp, listening amp, guitar/bass amp, pushing an amp too hard will cause distortion, clipping, or possibly shut it down. Headroom is a buffer of sorts, just like the car you drive, do you always need 300hp to go to the store? No, but when passing or trailering you might hedge that way. MC always gives his wisdom on speaker sensitivity and since he thinks his low fi speakers are 94db rated, he tells everybody to ignore speakers less than 90+db efficient. He ignores a few reviews of tekton speakers where the reviewer actually measured tekton 7db lower than the rated 94db from the manufacturer. If this is the case, which I’m guessing is fact since 1 of the trade mags does measurement tests and MC doesn’t, I would think MC would follow his own advice and start looking for a quality speaker this time around that’s 90+db efficient. IMO, it’s foolish to state a speaker needs to be greater than 90db unless you want to use a low powered SET amp, then by all means look for a high efficient speaker. |
Always had amps with 250W or more at 8ohms for 25+ years.
Had pickup truck bed of receivers, stereo amps, mono amps, etc etc. with less than 150W’s. Always clipped, never sounded good at drum solos, hard rocking metal/rock. Always sounded strained, and learned my lesson when I blew multiple mids and tweeters and 1 woofer.
If you like 100, 125, 40, or those little 3 watt amps, enjoy.
Not for me, and not at the levels I listen to.
More has always been better for me. It’s just effortless, clean, unrestrained flow of power to my speakers.
Will never get anything less than 250w @ 8 ohms ever again.
My experience and opinion.
Enjoy the music. |
