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High powered amp + high Effeciency speakers =?

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Posted on February 23, 2017 at 05:10:44
audiophilewannabe
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Location: toronto
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Since day one I've been using SET amp on my Edgarhorns. A local dealer has a stock ARC D125 for sale and I'm curious on how it would pair up with my Edgarhorns Titan. Is it dangerous? Will I hurt my speakers? I don't listen to loud music at all . I know that this much power is not necessary. Any of you guys have experience with high effeciency+high powered amp? ARC D125 is rated at 110 watts per side and it's a hybrid amp I believe it has 8 6550 output tubes 4 per side.
This what I got from the ARC site.

Features include: Servo for auto balance of plate currents between output tube push & pull pairs; Front panel LED indicators and adjustment controls for left and right channel output tube plate current; Low current LED indicator for each output tube viewable through cover; "Tube Saver" circuit to protect output tubes from abnormal conditions or input overloads (eg. DC); Twin subsonic cooling fans for temperature control and increased life of output tubes.

 

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RE: High powered amp + high Effeciency speakers =?, posted on February 23, 2017 at 05:46:41
Bill Fitzmaurice
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By modern standards 110w/ch isn't a high powered amp. There's no reason why it would damage your speakers. Obviously it would have more headroom than an SET, whether or not you'd hear any difference one can't predict.

 

RE: High powered amp + high Effeciency speakers =?, posted on February 23, 2017 at 07:14:18
KanedaK
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I've used 120watts on 104dB speakers with no issues at all but you might just réalise, as I did, that with such high sensitivity, the smallest the amp the better.

 

no reason not to try it, the crux of the matter, I'd opine, will be --, posted on February 23, 2017 at 07:34:34
mhardy6647
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how does that ARC amplifier perform (more to the point, how does it SOUND) at output levels of, say, 50 milliwatts to 1 watt?

That's what, I would opine, a lot of "modern" amplifiers get "wrong" -- because, for the loudspeakers for which they're intended to be used, those output levels are encountered only on "fadeouts".

I put "wrong" in quotes only because it's wrong for nuts like us who use loudspeakers with 100+ dB/watt @ 1 meter sensitivity. Normal (I'll refrain from using yet more quotation marks!) audiophiles, with today's highly-engineered, complex & sophisticated, say, 82 dB/watt @ 1 meter sensitive loudspeakers have (again, I'd opine) very different requirements of an amplifier.


That, in my far from objective, uneducated and completely personal/empirical perspective, is - as Frank Zappa might put it - the crux of the biscuit.

Only one way to find out :-)

all the best,
mrh

 

RE: no reason not to try it, the crux of the matter, I'd opine, will be --, posted on February 23, 2017 at 07:42:27
audiophilewannabe
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Huh??LOL....you lost me at hello.

 

really? do the math (it's easy!) , posted on February 23, 2017 at 07:46:04
mhardy6647
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if the loudspeaker's got a sensitivity of 100 dB, and you're listening at 80 dB, the amount of amplifier power you're requiring is something like 10 milliwatts.

How will that ARC amplifier sound at 10 mW output compared to, say, a single-ended 2A3 amplifier at 10 mW output? Best tested empirically (i.e., using your own ears). It might be fine. It might not. Only one way to find out.

This is the same point - I think! - that the post by KanedaK was making.


all the best,
mrh

 

My speakers are 104 db eff., posted on February 23, 2017 at 08:00:36
bcguitar
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They sound best with 10 watts or less as long as its push pull. SE always lacks in my system. Try a PP Triode 6V6 or 6AQ5 amp if you ever get the chance.

 

RE: High powered amp + high Effeciency speakers =?, posted on February 23, 2017 at 09:12:50
hottattoo
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Location: New York
Joined: July 30, 2011
I use a Dr.Bruce "Titan" type system with field coils drivers along with dual Altec 515b's per mid bass horns. With a sensitivity of around 108db, it is important to use an amplifier that is "QUIET" noise wise. I prefer 211 / 845 type amplifiers along with higher power triode tubes like KR t100. My system is in a medium size room 15.5' x 23' with 10' ceilings and I sit 17' away from the voice coils. Using 2A3, 50 , 300b amps ( which I have ) DON'T cut It !!! when playing large orchestral works, realistic live jazz, drum recordings etc. I have an older modified VTL mono blocks with 225 triode watts per channel and they sound ok but not as clear, spacious, and dynamic as my SET amps. I have had various ARC, CJ, and other push pull amplifiers in my system and none sound as good IN MY SYSTEM as SET. My sub woofers are dual TC Sounds LMS 5400's per sealed 9.5 cu ft. in dual opposed configuration with a pair of Crown Itec 5000hd amps strapped to mono blocks and crossed over at 60hz. at48db. The subs are eq'd flat from 12hz. to 60 hz. using Crowns built in eg / crossover functions.

 

I hate to say it, but I went to the dark side..., posted on February 23, 2017 at 18:26:48
Rod M
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I used a 45 SET amp for the longest time and prior to that a 30 watt Atma-Sphere amp. My problem was with the phone preamp that didn't quite have enough gain for my Shelter cartridge with the 45 amp though since we moved in 2010, I didn't have space to unpack all the records and I was doing a music server anyway.

After picking up a few trhift stores LPs, I got the bug for a change and put my old Classe DR9 150 watt SS amp into the system and it's still there a year later. It does play louder and it sounds great with more authority. You surely won't hurt the speakers if you're sane. My Edgarhors use JBLs which are speced for 25 to 60 watts or more. Real specs are hard to find. At 25 watts, you ears will break before you break the speakers.


-Rod

 

There are two problems, and its not the speaker !! , posted on February 23, 2017 at 19:24:48
drlowmu
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There are two problems I see, overall, with SETs and high efficiency speakers.

The first is, about 99% of the SETs have poor power supplies, in design and in wiring - so they all play non-dynamic. Also, about 99% of the SETs have a very poor high-end response, because the SET amp designer is unaware how to ( the usual case), or unwilling to spend the money, to GET a great high end response.

The SET "idea" is FINE, a match made in heaven for 98 Db and higher speakers, but the SET implementations MOST people use.... simply put, sucks big time.

It IS possible for a SET to be dynamic and have good highs, but unfortunately, most are sorely lacking versus whats possible.

The second problem is, very few high efficiency speakers are properly wired, from inside the SET amp that drives it, all the way through to the drivers' voice coils.

Because of the two problems, identified above, people are " forced " to go to push - pull ( 6AQ5s, 6550s etc ) or solid state,

In reality, if the two problems were THOUGHT about, and fixed, there is no need for more than a 3 Watt 2A3 amp, ( say a modern JJ 2A3-40 implementation ), on any WELL designed High Efficiency speaker system. That is exactly what I use on A7-800 VOTTs.

Well, there you have it in a nutshell. Have fun, I do !!


Jeff Medwin

 

RE: High powered amp + high Effeciency speakers =?, posted on February 24, 2017 at 03:39:07
audiophilewannabe
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One of the reason I even wanted to try this is because of the review of the Audio Research VS115 that I've read. The VS115 is 120watts/per side, the reviewer seems to be hearing something different from most folks here or maybe this VS115 is really that good.

http://www.audioresearch.com/contentsfiles/vs115-soundstagereview.pdf

I'll cut and paste what the reviewer said about the maxxhorn which has a 103 Effeciency.

The MaxxHorn Lumination speakers are completely different â€" very sensitive (a claimed 103dB/W/m) horn-loaded speakers I reviewed a few months ago and subsequently purchased. Because of their low power-handling capability, specified at only 15 watts RMS, I was apprehensive about using them with the VS115. But after the US distributor for the Feastrex drivers used in the Luminations told me the speakers will handle quite a bit more power than their rating suggests, I had to give amp and speakers a try. The result? Possibly the most gorgeous reproduced sound I've ever heard. The ability of the VS115 to reproduce a coherent, organized musical picture proved a terrific complement to the MaxxHorns' temporal coherence. Together, they produced some of the most real-sounding reproduced music I've experienced, and not in a sterile, analytical fashion. Listening to "Miserere" was incredibly moving; although I had meant to sample only a part of the piece, I literally could not bring myself to move until the last note faded into silence, and then I sat there dumbfounded that recorded music could sound so beautiful. Jennifer Warnes' voice sounded as realistic as I've ever heard it on "The Panther." I've heard this recording zillions of times, but never has it portrayed such a real-sounding voice in a real space. And so it went with recording after recording.

 

RE: High powered amp + high Effeciency speakers =?, posted on February 24, 2017 at 06:32:55
cawson@onetel.com
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I have Avantgade Uno speakers with 102dB efficiency. For years I was using valve amps of between 5 and 28 watts, but have recently been using solid state amps. I've had in my system:

Red Wine Signature 30.2 - 30 watts - decidedly not happy with my speakers
Benchmark AHB-2 - 100 watts - If you want dead silence but deadly dull sound, this is great!
Accuphase A-36 - 30 watts Class A - Very good but bass not brilliant
GamuT D200 - 200 watts - the best I've heard my horns sounding, particularly the excellent well controlled bass.

Provided you don't push the full power from a big amp into your speakers, they will not suffer any damage. However if you can adjust the gain to improve accurate volume setting and to reduce the effective power from the amp, so much the better. Otherwise don't do what I did last week - place an object on the remote volume control and accidentally release its full output!

Peter

 

re: solid state - two words. Nelson. Pass., posted on February 24, 2017 at 07:22:53
mhardy6647
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That guy gets it. :-)

I've been playing with one of these of late. As low-end an implementation of Mr. Pass's philosophy as can be imagined, with specs that are evocative (for better or worse) of an SE 2A3 amplifier.

DSC_6923 (2)


Danged thing sounds good.
I am sure his serious (and expensive) SS amplifiers are even better.
Just sayin'.

Kit link below: see also http://www.firstwatt.com and http://www.firstwatt.com/pdf/art_amp_camp_1.pdf for more philosophy and info.



all the best,
mrh

 

RE: High powered amp + high Effeciency speakers =?, posted on February 24, 2017 at 08:11:26
Inmate51
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Posts: 8747
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There are at least a couple of things to consider here.

First, let's talk about sound level, or SPL. You want to play your system at some level which you like. Once things start to get a bit LOUD, would you rather have your amp: a) Clip, or b) deliver the desired output?

Next, there's the issue of loudspeaker capabilities. What can it actually do, in terms of output at various frequencies (low, mid, high)? There are two critical parameters here: excursion and heat dissipation.

As long as your amp isn't clipping, and your speakers can do what they're being asked to do, you're good. You can put a billion watt amp into the chain, and if your SPL requires 100 watts peak, it's just sittin' there slackin'.

Having said that well-known and obvious info, here's the kicker: Many solid state amplifiers don't have good/high quality sound at low output levels. This is one reason why well-designed amplifiers run in Class A mode at low drive levels. My good friend John Curl can talk your ear off about this stuff (and correct me).

So, it seems to me that you should be concerned about output and having the necessary components to get it done, as well as having that first quarter of a watt be as pristine as possible.

:)

:)


 

they do :-), posted on February 24, 2017 at 10:02:36
bare
Audiophile

Posts: 525
Joined: April 14, 2009
My Firstwatt is Last Amp I will be using.. ever.
Been thru many amps over the years, meshplate 45's even.
This thing IS the best I've heard.
They may ? be better ones.. but frankly: I have no desire to explore further.

 

A less powerful amp is recommended; here's why:, posted on February 24, 2017 at 10:15:51
Ralph
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In most push-pull amps, the distortion is a certain amount at full power. As you decrease the power, the distortion goes down to a point about 5% or so of full power. At that point the distortion often increases, and it can be by quite a lot!

And you have efficient speakers, so the ARC is going to be operating about 95% of the time in this higher distortion range! So you won't be hearing the best of the amplifier by any means.

The solution is a less powerful amplifier. You can still run push-pull, but it should be 30-60 watts in most rooms. With a single pair of output tubes it will be less distortion as well.

Whatever your SET amp was for power, I would get a push-pull amp of about 4 times the power of the SET. I think you will find that to work quite nicely and you may find that it sounds a lot better.

I suspect that is not a lot of power so you might be able to find a triode amp to fit the bill. Might as well make the most of it...

 

RE: High powered amp + high Effeciency speakers =?, posted on February 25, 2017 at 04:57:42
Scholl
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I enjoy listening to a combination of high powered MOSFET amps and various high efficiency speakers including large horns to 300hz.

I also enjoy a simple setup with push pull 6BQ5s and a 12" two way.

Lots of enjoyable combinations.

Scott

 

RE: really? do the math (it's easy!) , posted on February 25, 2017 at 09:10:35
tomservo
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An issue is, a sound level meter and Volt meter respond to a "short term average" and not peaks. For compressed FM, the instantaneous peaks may be 10 times greater than the average SPL, power or Voltage but many audiophile recordings have 20 or 30dB or more peak to average.
While you can't hear instantaneous clipping as a flaw, when compared to the same signal without it, the without version is more dynamic.

So, lets say you had a P to A of 30dB and you had 100dB 1w1m speakers To reach 80dB at the listening point say 2m away requires 92 dB at 1m and about 1/6 Watt no problem... until you examine what's needed for the musical peaks +30dB or 1000 times larger or 165 Watts.

The up side is modern music is increasingly compressed so we can use MP3 players so dynamic range is no longer as much of a concern and as i said, you can't hear very short clipping as a flaw, but one can easily see it on an oscilloscope looking at the amplifier output Voltage.

 

RE: My speakers are 104 db eff., posted on February 25, 2017 at 09:23:19
drlowmu
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Most all SET amps lack, because they are not built to be dynamic, nor are they built to be wide band. A Push Pull amp gets top-end bandwidth easy, and you hear that. 99% of the SET amps don't cut the mustard in the two areas I have mentioned. Good job listening on your own !

Jeff Medwin

 

RE: really? do the math (it's easy!) , posted on February 25, 2017 at 09:42:52
audiophilewannabe
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So your saying that more dynamic sound means no instantaneous clipping? In essence a high powered amp would sound better?

 

RE: really? do the math (it's easy!) , posted on February 25, 2017 at 10:55:24
tomservo
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"Sounds better" is subjective but so far as producing what's in a recording with 30dB peak to average level, yes that's it.
You can hear prolonged clipping and it sounds bad, but instantaneous clipping you cannot hear as a flaw, only a difference in dynamics comparing with and without.
The final arbiter of it is examining the amplifier output voltage, any clipping at any stage of the electronics chain shows up there.



 

RE: really? do the math (it's easy!) , posted on February 25, 2017 at 11:20:50
audiophilewannabe
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That being said, is there some sort of a table for a good match between power and Effeciency? Something like cartridge and tone arm mass matching? If you know what I'm saying.

 

RE: High powered amp + high Effeciency speakers =?, posted on February 25, 2017 at 18:55:17
EduardG
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Power is a strange thing - you can never have too much of it. What I think matters the most is how well your particular speakers interact with that power amplifier. To my ears, nothing sounds better with high efficiency horns than SET. Having said this I have to remind myself of an insanely good PP amplifier (a pair of KT88 per side) I heard at my dear friend's Cy Brenneman's house driving a 106 dB horn system. Well, I guess there are exceptions...

 

RE: High powered amp + high Effeciency speakers =?, posted on February 26, 2017 at 04:44:25
audiophilewannabe
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Do you recall which Cyrus Brenneman amp that was? He makes around 4 or 5 different ones I think.

 

RE: High powered amp + high Effeciency speakers =?, posted on February 26, 2017 at 13:00:48
Rod M
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AFAIK, it was his Cavalier that Bruce typically used.

-Rod

 

RE: High powered amp + high Effeciency speakers =?, posted on February 27, 2017 at 03:22:53
PeterZ
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A large number of high efficiency speakers built today have multiple woofers which lend themselves to not being as easy a load in the bass as their efficiency numbers suggest. If you like solid bass, make sure you have a high damping factor amp with lots of current on the bottom end.
Other than that, a lush SET / Triode for lower mids on up typically is what many prefer.
PeterZ

 

NDCR, posted on February 27, 2017 at 15:16:12
djk
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40 years ago Yamaha used the NDCR (noise distortion clearance range)to measure it's receivers at low volume settings.

Yamaha CR-1020, NDCR (IHF-A) : for 0,1% into 8Ohm 20Hz to 20Khz from 100mW to 70W (Vol -20dB, Phono to SP Out)

Most other brands could not meet this kind of performance at low power levels, Yamaha could.
Not 2 Big 2 Jail

 

yeah but for some of us 100 mW = ca. 94 dB @ 1 meter (1 channel)!, posted on February 27, 2017 at 16:28:44
mhardy6647
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So we need "good" at 10 to 25 mW or so :-)

... and NOT that I have anything against 1970s Yamaha, as you may know.
I've been something of a fan -- since 1976 -- and owner since 1978.

DSC_0241

I still think the stuff sounds good -- but not something I'd use for the Duplexes.
all the best,
mrh

 

RE: yeah but for some of us 100 mW = ca. 94 dB @ 1 meter (1 channel)!, posted on February 28, 2017 at 08:02:10
Inmate51
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Just fyi, if that really is a reel of Ampex 407 on the Otari, it's going to need baking before playing, unless it's a reformulated newer vintage.

:)

 

RE: really? do the math (it's easy!) , posted on February 28, 2017 at 09:43:45
Tre'
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"...and you had 100dB 1w1m speakers To reach 80dB at the listening point say 2m away requires 92 dB at 1m..."

Outdoors yes, but indoors, once you are within the reverberant field, the SPL stays the same regardless of distance.

Plus, a stereo has two speakers and two amplifiers you need to add 3db.

BTW I believe 30db P to A is optimistic. Maybe I just listen to the wrong recordings. :-)

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

it's just used a take-up reel; no tape, fortunately, posted on February 28, 2017 at 12:51:21
mhardy6647
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A gift from a kind denizen @ AK some time back.

Someone chided me for mixing reels on my A77. I can't now remember if my gaff was that I mixed NAB and standard hubs, or metal or plastic reels, but I am willing to believe what I was told.

So, I can't quite say I understand the physics well enough, but I'll admit to being far from a reel to reel tape pro, so I needed a metal, NAB hub take up reel or two. It's perfect for that duty, you know? :-)

DSCN5764
all the best,
mrh

 

RE: High powered amp + high Effeciency speakers =?, posted on February 28, 2017 at 20:16:30
BigguyinATL
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Noise Level is important for high efficiency speakers. Increasing power doen't necessarily increase noise. A 5 watt amplifier can have a higher specific noise level than a 500 Watt Amplifier. But theoretically can handle 20 dB wider dynamic range. While most recordings don't have minimum to peak levels of more than 40dB some recordings can span 70dB or so... and live music can span 80dB or more! A snare rim at 10 Feet away can have a peak level of over 125dB!
90dB/W/m loudspeaker needs a 500Watt amplifier to score that peak!
a 100dB/W/m Loudspeaker still needs a 50 Watt Amplifier.


"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

RE: yeah but for some of us 100 mW = ca. 94 dB @ 1 meter (1 channel)!, posted on March 1, 2017 at 04:06:49
PeterZ
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If that's an old Yamaha CA-800 or CA-1000, the class A amplifier mode should get you close :-)
PeterZ

 

RE: really? do the math (it's easy!) , posted on March 1, 2017 at 04:07:03
tomservo
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A few thoughts;
The reverberant field only exists in very large spaces and is as you suggest the point where the SPL stops falling with increasing distance, it doesn't exist at audio frequencies in a living room and once in that field, voice ineligibility and a stereo image is gone, STIpa is VERY low.

The idea behind stereo reproduction is that one has two independent sources, each able to reproduce it's assigned channel of the image.

It's possible that none of your recordings have that much dynamic range, especially if one depends on FM radio as a source or highly compressed pop mp3's etc. If you listen to "hifi" recordings, try analyzing one using Cool Edit, Audacity etc and see what that indicates and examine your amplifier output Voltage using an oscilloscope for instantaneous clipping.

There are reasons why home hifi falls so short of real.


 

RE: really? do the math (it's easy!) , posted on March 1, 2017 at 09:35:47
Tre'
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What you are saying about the reverberant field is at direct odds with what Paul Joppa has repeatedly said.

" In a room, you can separate the sound field into two parts, the direct field and the reverberant field. The reverberant field is all the energy that has bounced at least once off a wall. It's very chaotic, but averaged over a region of space or frequency the mean level is uniform in the room - at least, if the room is not too weird.

The direct field falls off with an inverse square law, just as you said.

There is a "critical distance" at which the direct field equals the mean reverberant field. Beyond that distance, the averaged sound level does not vary. In an average living room, with speakers of average directivity, that critical distance happens to be approximately one meter - an extremely lucky, or at least convenient, coincidence."

When I walk around my room I don't hear the SPL drop off due to distance.

4' to 16' would be -12db in an open space. 12db is a lot of volume change.

I'm walking around my room right now with the system playing. Walking up close to the speaker (4') and back (16') and I hear nothing like a 12db change. I hear very little change at all and any change I do hear could be due to standing waves, etc.

Do you hear a 12db drop in SPL in your room going from a 4 foot distance to a 16 foot distance?

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

there's a CA-800 and a CA-2010, posted on March 1, 2017 at 13:03:48
mhardy6647
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The CA-800 does indeed sound pretty good in Class A; haven't tried it on the Duplexes, though.


DSC_0184

The CA-2010 is reputed to work, but is utterly original & I've never had the chutzpah to plug it in! I've had it for years, too.

It DO look nice as a shelf queen, though, don't it? :-)

DSC_6689_z
(sorry for the wide-angle lens distortion -- this pair deserves a better photo)

all the best,
mrh

 

RE: really? do the math (it's easy!) , posted on March 1, 2017 at 13:12:48
tomservo
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As Paul points out in your link this is well studied / understood in commercial sound room acoustics is a well known field in commercial sound (as the larger the room volume the more critical all this gets), the reverberant field only exist when the reflected sounds are so random they average out and at audio frequencies this only happens in large rooms. Worth pointing out that when in the reverberant field there is essentially ZERO voice intelligibility and while you can tell the source is music, you are well past understanding words or hearing a stereo image and potentially being able to tell what sound it is. This is the highly muffled / garbled sound one often hears in gyms and some stadiums, a lot of reflected sound and a little direct sound.
What you describe is what happens between the near field (where the direct sound dominates) and reverberant field. The critical distance is as you describe but is not desirable to listen at or past that because of the great loss of articulation AND that distance is strongly dependant on the loudspeakers directivity which increases the near field zone.
"I'm walking around my room right now with the system playing. Walking up close to the speaker (4') and back (16') and I hear nothing like a 12db change. I hear very little change at all and any change I do hear could be due to standing waves, etc."
Hearing isn't measuring it, play pink noise, use a sound level meter to measure it.

Do you hear a 12db drop in SPL in your room going from a 4 foot distance to a 16 foot distance?"
It's about 11dB measured with SH-50's and broad spectrum pink noise.
Best,
Tom Danley
Danley Sound Labs

 

RE: High powered amp + high Effeciency speakers =?, posted on March 1, 2017 at 14:00:42
tomservo
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That helps underscore why it's so hard to accurately reproduce many dynamic things, what we hear and judge as "loudness" is only loosely related to the dynamic of the signal and for many things perceived loudness is more like a short term average C weighted SPL

 

RE: really? do the math (it's easy!) , posted on March 1, 2017 at 15:06:23
Tre'
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"It's about 11dB measured with SH-50's and broad spectrum pink noise."

I didn't ask you to measure it. I asked you if you heard it.

Sound meters are very directional and only measure direct sound.

If you can't hear the 11db loss that you say is there, then it's not there.

11db is huge and you would hear it without having to measure it.

Edit, I see now that your speakers have only 50 degrees of dispersion.

That would make all the difference.

I didn't understand that you are basing what you said on directional speakers.

Sorry.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: High powered amp + high Effeciency speakers =?, posted on March 1, 2017 at 19:33:36
claudej1@aol.com
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Posts: 261
Location: Detroit
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Right on!

 

RE: really? do the math (it's easy!) , posted on March 1, 2017 at 20:39:12
claudej1@aol.com
Audiophile

Posts: 261
Location: Detroit
Joined: August 17, 2007
Do you find that the dynamics of a commercial Jazz recording on a CD to exceed 20 db crest factor?

I have yet to encounter a 30 db crest factor except for live music and a few very special recordings that show off dynamic range, very rarely. Or maybe I haven't come across the right recordings. How would I know for sure?

Claude

 

RE: really? do the math (it's easy!) , posted on March 3, 2017 at 14:04:58
Inmate51
Audiophile

Posts: 8747
Joined: July 6, 2005
Hey - what happened to you guys? I just made some more popcorn!

But Siriusly, a studio's echo/reverberation chamber has a pretty long decay time, even though they're pretty small rooms. On the other hand...

It's pretty hard to measure ANY notable reflections in an anechoic chamber of the same size.

Reverberant field, or not?

Just sayin'.

:)






 

RE: really? do the math (it's easy!) , posted on March 4, 2017 at 16:41:59
Tre'
Industry Professional

Posts: 12031
Location: So. Cal.
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.
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: really? do the math (it's easy!) , posted on March 5, 2017 at 13:52:59
Inmate51
Audiophile

Posts: 8747
Joined: July 6, 2005
Hey Tre', thanks for that link. This is part of what I've been talking about for decades! I don't remember if Leo Beranek first analyzed and named the phenomenon, but the "critical distance" is an important measure of the soundfield at any position in a room (AND outdoors!), and is an important contributor to achieving good intelligibility and musical detail where speech and instrumental detail is important. (Be aware that the Critical Distance varies somewhat with frequency and with angle from the source.)

It is important to note that the explanations on the linked site are a bit over-simplified in a few areas, but overall, this is a very good basic explanation of what's going on in a room, sound-wise. It would be good if the author would state such, so that the uninitiated reader won't take it as "the gospel truth".

Anyway...

Even though we know several fundamental factors, the soundfield in a room is not easily described. For the purposes of discussion here, even "typical" living rooms are anything but "typical". Although they do often share some common traits with regard to absorption characteristics, as soon as we start talking about architectural plan design, things go way off the rails very quickly! An "open plan" house is acoustically very different from a more "segmented" house, even though they may share similar "room treatments".

Back to "reverberant field, or not". Clearly, in any "normal" home room where a high fidelity system is employed and some degree of ambient sound is present, there is a reverberant field, however "dry" it may be. Whether or not it achieves a state which can usefully be measured as an RT60 is another matter.

:)

 

RE: really? do the math (it's easy!) , posted on March 6, 2017 at 10:09:53
tomservo
Manufacturer

Posts: 6866
Joined: July 4, 2002
Hi
The issue is "where does the reverberant field begin".

Picture a low frequency one below the lowest room mode, at these frequencies your room is a leaking pressure vessel and this "containment" of the bass pressure is the only free lunch in audio, "room gain".

Be aware too that a flexing wall or floor etc is also a diaphragmatic absorber and a sink hole at that frequency.

AS soon as you increase the frequency past the first mode, one is in the modal region where a measurement easily identifies large peaks and dips in the response in the room.

The larger the room, the lower the first mode is and the more numerous the modes are as you go higher up. With a large enough, live enough room one can reach the critical distance and the reverberant field at that point no longer has large peaks and dips, the modes are so dense they have averaged out. There is zero voice intelligibility as well as the time information has been completely scattered and all is left is a noise with the same power spectrum as the acoustic power of the source.

That condition is pretty normal in very large spaces and when public address announcements are barely intelligible as a result of the direct sound not being high enough over the "noise" or reverberant sound.

At the dimensions of a living room and typical loudspeakers it is usually the specular reflections close to the loudspeaker which harm imaging the most, and the side walls are often the source.
One way to "see" where absorption will help is to place a mirror on the wall where you can see the tweeter of the closest speaker from your sweet spot and then replace the mirror with a sound absorbing panel, do both sides..
Remember that critical distance and rt-60 are all terms that were originated for and apply in large scale acoustics and do not apply where the modal density is sparse.

 

RE: really? do the math (it's easy!) , posted on March 7, 2017 at 03:54:48
Inmate51
Audiophile

Posts: 8747
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Thanks for your thoughful and useful post.

Room modes are definitely an issue. Here's a related story: Back in 1982, I wrote a BASIC program to calculate room modes and print the results. Whoa, dude, 1982?! Yeah. I was sick and tired of calculating and plotting everything by hand! Hey, remember slide rules?! Fortunately, they were past their prime when I was in high school.

"At the dimensions of a living room and typical loudspeakers it is usually the specular reflections close to the loudspeaker which harm imaging the most, and the side walls are often the source. "

This is common "wisdom" and is total bullshit.

But then, I'm a recording engineer and a musician, so what the heck do I know?

:)

:)

 

RE: really? do the math (it's easy!) , posted on March 7, 2017 at 06:17:55
tomservo
Manufacturer

Posts: 6866
Joined: July 4, 2002
"But then, I'm a recording engineer and a musician, so what the heck do I know? "

Well think about it, in a real studio, which end is dead and close to the loudspeakers when traditional front sofit mounted speakers are used?

When near field / meter bridge mounted monitors are used, how far away in time and level are the closest wall reflections?

To preserve stereo image, suppressing any strong reflected sound within say 0 to 10 ms of the source is usually audibly beneficial, something like directivty in the way it increases the nearfield where the direct sound dominates late reflections.

 

RE: really? do the math (it's easy!) , posted on March 7, 2017 at 07:22:43
Inmate51
Audiophile

Posts: 8747
Joined: July 6, 2005
Actually, I have thought about it. A lot. :)

The room is an integral part of the sound, and, early reflections contribute to the sound.

But, speaking of soffett-mounted speakers, when I moved to Dallas decades ago, my (now) old buddy Russ Berger invited me to his home, and guess what?... He had Altec 604's soffett-mounted in his house! Just like they had at the Mastering Lab in L.A. back in the day.

Anyway, here's a recent pic of a room where the stereo imaging was absolutely EXCELLENT without any absorption on the rear or side walls.

Edit: The guy on the right is Siegfried Linkwitz. I don't know who the guy on the left is.



:)

 

=higher x over distortion, posted on March 11, 2017 at 12:44:12
Rafaro
Audiophile

Posts: 116
Joined: July 30, 2005
Hi APWB:
The advantage of SETs is no x over distortion (since the single tube does both swings and there is no x over per say) and pretty sounding lower harmonics. Once you switch to Push Pull amp designs wether SS or tubes cross over dist. becomes a factor. Since x over distortion is quite audible this is to avoided as in SET or class A amps. In SS amps cross over distortion levels are higher at lower powers as opposed to tube amps. That AR amp with 4x6550 tubes per side?? is MASSIVE OVERKILL for horn speakers but horns being more efficient dissipate more heat and can tolerate more power than direct radiators. Luck


Rafaro

 

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