Bryston 7BST 600 Watt Monoblock Review

[Sokel]

Before that as in before Toole's research? Or as in before modern speakers?

Are you referring to DIY? Or manufacturers?


The trends that was already there before who's/what research?

Because before Toole's research there was a lot people and manufacturers didn't know.

Not DIY, no.
Before, as before the Toole's research, yes.

There were the ones who didn't know (or ignored) and the ones who did.
You can find commercials from the '50s with the advertised qualities which are still trending (flat, extended FR, etc)

Now, if that trend suits all of us is the end-of-times debate.

But you can find older gear (and designs) that measure just fine.

 

[FraPia-62]

I

I can confirm everything you said about the amp. I wonder if you could have left pin 1 floating provided it was a twisted pair cable and solved the problem. Does equalizing the input impedance on each leg of a differential amp optimize the cmrr? I'm assuming in this case you are talking about an installation you were familiar with and not something installers run across all the time and deal with professionally.

Hi, as far as I remember, lifting the ground only changed the hum into a metallic buzz, while only leaving pin 1 floating only reduced hum a bit, but made the amplifier more sensitive to RFI.
Equalising the impedance on each leg of the differential amp will indeed optimise cmrr. A differential amp is a resistive bridge that includes both the resistors of the difference amplifier and the output resistors of the source (typically 50-100 Ohm and identical on both legs). Only when also the input resistors of the balanced input are identical the bridge is balanced and can provide acceptable cmrr.
The installation was an open air festival, and the Bryston amplifier and 4 speakers was a later addition to the system to cover also a snack bar area. The hum issue was discovered on field and had to be handled on site.

 

[PristineSound]

Not DIY, no.
Before, as before the Toole's research, yes.

There were the ones who didn't know (or ignored) and the ones who did.
You can find commercials from the '50s with the advertised qualities which are still trending (flat, extended FR, etc)

Now, if that trend suits all of us is the end-of-times debate.

But you can find older gear (and designs) that measure just fine.

Before Toole's research, not many knew about psychoacoustics and listeners' preferences. Sure they knew about on-axis linearity. But they knew very little about controlled directivity and the related psychoacoustics that follows.

If you really believe that speakers of the past are up to snuff, then name some make and model that are even remotely close to some of the best speakers today, of the likes of KEF, Genelec, Neumann, Dutch&Dutch, Kii, Perlisten, Ascend, Revel, Ascilab.

 

[pma]

If you really believe that speakers of the past are up to snuff, then name some make and model that are even remotely close to some of the best speakers today, of the likes of KEF, Genelec, Neumann, Dutch&Dutch, Kii, Perlisten, Ascend, Revel, Ascilab.

https://jblpro.com/en/site_elements/4430-and-4435-information

Small monitors are inadequate, regardless good looking measurements.

 

[PristineSound]

https://jblpro.com/en/site_elements/4430-and-4435-information

Small monitors are inadequate, regardless good looking measurements.

Toole started his research work at the NRCC in the early 60's and was publishing in the early 70's. These JBL were introduced in the early 80's.

Additionally, compare these with modern day speakers of the likes that I have previously listed, these are no comparison.

 

[Sokel]

Before Toole's research, not many knew about psychoacoustics and listeners' preferences. Sure they knew about on-axis linearity. But they knew very little about controlled directivity and the related psychoacoustics that follows.

If you really believe that speakers of the past are up to snuff, then name some make and model that are even remotely close to some of the best speakers today, of the likes of KEF, Genelec, Neumann, Dutch&Dutch, Kii, Perlisten, Ascend, Revel, Ascilab.

As I mentioned Aerial, will 25 years do?

Aerial Acoustics Model 7B loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements The big Aerial's estimated sensitivity was a little lower than specified, at 84.4dB(B)/2.83V/m, probably due to a lack of energy in the low treble. Its plot of impedance magnitude and phase against frequency (fig.1) revealed the 7B to be a moderately demanding load, with...

www.stereophile.com

Vertical response, and that without WG, etc.

...and the lateral one.
$5k back then.

A LOT more back then, is just that a lot of people didn't rely on measurements much back then so JA didn't get the attention he should have.

(as a side note, 20T (not that ones) would have been my speakers now if I was in US, either that or some Rockports,)

 

[pma]

Additionally, compare these with modern day speakers of the likes that I have previously listed, these are no comparison.

Listen to the big philharmonic orchestra recording at high SPL level. That is my test. No small monitors are able to create believable sound effect from such venue. Regardless their super duper directivity. It is similar to B100 x adult amplifier.

 

[PristineSound]

As I mentioned Aerial, will 25 years do?

Aerial Acoustics Model 7B loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements The big Aerial's estimated sensitivity was a little lower than specified, at 84.4dB(B)/2.83V/m, probably due to a lack of energy in the low treble. Its plot of impedance magnitude and phase against frequency (fig.1) revealed the 7B to be a moderately demanding load, with...

www.stereophile.com

View attachment 481134

View attachment 481135

Vertical response, and that without WG, etc.

View attachment 481136

...and the lateral one.
$5k back then.

A LOT more back then, is just that a lot of people didn't rely on measurements much back then so JA didn't get the attention he should have.

(as a side note, 20T (not that ones) would have been my speakers now if I was in US, either that or some Rockports,)

Again, Toole was already publishing in the early 70's.

And take these Aerial compare them with today's top end speakers, it's not close.

Anyway, not here for a pissing match. I was just stating that old speakers has a very hard time matching the performance of today's speakers. I think most people who research this topic deeper will come to a conclusion that this statement is generally true.

This shouldn't be treated as an ding to the audiophiles from that era, as everyone thinks their era is special. The fact is, science will always advance, resulting in technologically better products. I know one day, my Neumann won't be considered good speaker and I look forward to that day.

 

[PristineSound]

Listen to the big philharmonic orchestra recording at high SPL level. That is my test. No small monitors are able to create believable sound effect from such venue.

I would probably say that is true, except you should give the Dutch and Dutch a listen. I'm sure there are other speakers as well.

Regardless their super duper directivity. It is similar to B100 x adult amplifier.

I don't think much of any Topping amps, aside from giving my thumbs up on their incredibly low distortion and noise.

 

[Sokel]

Again, Toole was already publishing in the early 70's.

And take these Aerial compare them with today's top end speakers, it's not close.

No, not close, agree, what we see is better than even today's SOTA ones.
Charts don't lie.

My comment was about the "10-15 years" mark you set.
There's lot's of research even from the 40's , not only '70's.

Let's hope it will evolve, cause recent years trends about thin, tall speakers got the meat out of them.
They can maybe go reference loud but no kick, no body, thin and strident.

 

[FraPia-62]

1. is a usual issue of most commercial audio amplifiers. Often resulting from the fact that SE and BAL input share the same circuitry (to save costs) and SE input just uses half of the circuitry with 2nd half input shorted to gnd.

2. again, a usual issue and misunderstanding of circuit function by commercial audio designers. They tried to "balance" -IN and +IN SE impedances vs. ground, forgetting how CMR works. They also rely on assumption that only short signal cables (like 2m) are used.

Yes, I agree. I just wonder if a simple bal/unbal switch that does the proper connections is too expensive for a very expensive amplifier like this one.
Regarding the unbalanced resistors in the difference amplifier I don't know what to say. Design and operation of the difference amplifier is taught in technical schools and universities, how can it be that Bryston engineers don't know?
In the meantime I downloaded the schematic diagram of this amplifier and I can confirm that the two design errors are there.

 

[PristineSound]

My comment was about the "10-15 years" mark you set.
There's lot's of research even from the 40's , not only '70's.

This is the entire statement:

"Modern speakers, as in the last 10-15 years or so, speakers has gotten to it's current peak performance."

As in speakers from the last 10-15 years are the best speakers ever. This statement will probably be true in another 10-15 years as well.

Let's hope it will evolve, cause recent years trends about thin, tall speakers got the meat out of them.
They can maybe go reference loud but no kick, no body, thin and strident.

My Ascend ELX RAAL, is a skinny little tower, they kick, they have body. Yes, they are not bookshelves.

Anyway, I think we agreed on most points, I'll stop hijacking the thread

 

[pma]

Hi, as far as I remember, lifting the ground only changed the hum into a metallic buzz, while only leaving pin 1 floating only reduced hum a bit, but made the amplifier more sensitive to RFI.

This is to be expected. Especially higher RFI susceptibility and potential CMV overload.

 

[PristineSound]

In 1973 is when I discovered that 100 watts a channel was not going to cover anything that I was going to do in audio and here is why:

The Dahlquist DQ10 was the first loudspeaker manufactured by the Dahlquist company, then based in Hauppauge New York. Among the company’s founders were some famous names in audio, such as Jon Dahlquist and Saul Marantz, Irving M. Fried and Werner Eymann.

• Type: 5-way phased array, open baffle
• Frequency response: 35 Hz — 27,000 Hz
• Recommended amplification: 150 to 200 Watts
• Crossover frequencies: 400, 1000, 6000, 12000 Hz
• Nominal impedance: 8 Ohms
• Bass: 1 x 25,4cm (cone)
• Mid-bass: 1 x 12,7cm (cone)
• Midrange: 1 x 4,45cm (soft dome)
• Tweeter: 1 x 1,9cm dome
• Super Tweeter: 1 x piezoelectric
• Dimensions: (h) 99cm x (w) 77cm x (d) 33cm
• Weight: 22,7 kg
• Years: 1973-1988

The DQ10's design was first exhibited at a New York audio show in 1972.

In combination with the speaker stands, the DQ10 looked light and non-technical from the front and slim from the side. It arguably held greater resemblance to a radiator than a loudspeaker, an aspect that made it both stand out as a design element and an understatement in terms of technology. Strangely enough, its appearance fits into a modern household just as well as it did back in the seventies. It is not surprising, therefore, that close to 60,000 pairs of Dahlquist DG10s were sold between 1973 and the end of its production in 1988.

The Dahlquist was rated at 8 Ohms and appeared to be easy to drive, and yet, the phased array design required lots of clean power from the amplifier to sound at its best.

150-200 watts paired with high-current ability went down well with the DQ10. (and 100 watts or less just did not cut it)

Although the speaker was positioned relatively low for many seating arrangements, its height became less of an issue when sitting further away from the speakers.

Generous distance (please note: GENEROUS DISTANCE) from the speakers was essential to minimize phase differences resulting from the spacious array design.

Since then, I have always skewed to the high side with high current & higher watt amps.

My six mid-1980's NAD 2200's are nominally rated at 100 watts RMS.
Results here indicate otherwise:
It is power measurements where the magic of this amplifier comes to life so let's look at that with 4 ohm load first:

We can see a kink in distortion when we hit 200 watts as the unit sails past that to produce whopping 337 watts per channel, both driven! Per design characteristics, you can have much more during momentary peaks:

Wow, we have one kilowatt of power coming out of this amp in short duration!

Switching to 8 ohm we see similar results as 4 ohm:

Sweeping the power test at 4 ohm with different frequencies shows a well-behaved amplifier:

You do loose power in higher frequencies but that is fine since music spectrum has lower energy there anyway.

Due to the long duration of this test, the protection circuit likely backed off the high voltage rail, producing lower output levels.

(SINAD 95 [through the LAB inputs]).

This post almost reads as an informercial for the Dahlquist

You can use this calculator from Benchmark to calculate peak SPL at listening position. I used this calculator and it is sufficient for my needs using my conservatively rated 90w/channel to power my 87dB sensitivity speakers.


Supposely, Luigi Nono – Fragmente – Stille, An Diotima (La Salle String Quartet, Deutsche Grammophon) has a DR27, probably one of the highest dynamic range an album has. I listen on average low 70's. I suppose if you have a much bigger room, than you may need more power, but most albums don't have this level of dynamic range.

 

[Sal1950]

To be fair, unlike electronics, speakers has been steadily improving ever since Toole's research. Modern speakers, as in the last 10-15 years or so, speakers has gotten to it's current peak performance. So having said that, all older speakers are essentially "junk."

Oh oh, I think that smack's gonna leave a mark.

 

[EJ3]

This post almost reads as an informercial for the Dahlquist

You can use this calculator from Benchmark to calculate peak SPL at listening position. I used this calculator and it is sufficient for my needs using my conservatively rated 90w/channel to power my 87dB sensitivity speakers.


Supposely, Luigi Nono – Fragmente – Stille, An Diotima (La Salle String Quartet, Deutsche Grammophon) has a DR27, probably one of the highest dynamic range an album has. I listen on average low 70's. I suppose if you have a much bigger room, than you may need more power, but most albums don't have this level of dynamic range.

View attachment 481160

I don't (nor ever have given) a rip about Dahlquist DQ-10's (although I do own some M-905's, a completely different concept).

But, because Dahlquist's are pretty unknown (especially outside of the USA), I thought that I would provide some info on them.
My ONLY point was/is that they are one of the speakers that 100 watts is not sufficient for.
And, out of speakers that I have chosen over the years, there are many others. Acoustat X's would be another example.
Another speaker that the same friend that owned the DQ-10's had.
I personally never owned any speakers as inefficient as those, but I have only owned (and still do) 1 set of speakers that I thought 100 watts was more than adequate.
Those are a set of Frazier Super Monte Carlo's (made in Texas) that are 8 ohm (nominal) 94 Db @ 1 meter with 1 watt RMS [2.83 volt], if I remember correctly).
I want to thank you for putting the Peak SPL Calculator from Benchmark out, as many are unfamiliar with it.
At my mother's house (where my main stereo system is, about 12 miles from my house, her house is on a deep water creek & were I use a 15 ft. aluminum boat with a 15 HP outboard frequently).
Room dimensions: L 28 ft. X W 24 ft. L side wall 8 ft. high, Rt side wall 12 ft. high, one 8 ft. high by 12 ft. wide opening into the dining room, which as a 7 ft. X 34" doorway to the kitchen & breakfast area, and also, along the 12 ft high wall, there is a 3 ft. X 3 ft foyer that then opens into the breakfast area through a 7 ft. X 34" doorway, one 6 ft. wide 12 ft. tall opening into the 4 steps down foyer, a 3 ft. wide stair case going 6 ft up to a 3 ft. X 3 ft. platform with 2 more steps up, and a 7 ft. X 34" doorway to upstairs.
I think that I got all that correct, as I am not there right now. But there is also a half width partial wall involved on the wide part of the floor with a height of 8 ft to 10.5 ft over a 5 ft width.
I also forgot that there is a large, curved bay window (that a couple of people can sit in the inner sill area), made up of angled flat panels of glass.
Needless to say, I have never calculated all of this for square feet or room volume, much less what reflections do.
The good thing is that there doesn't seem to be any nulls with the sub-woofers.
As to dispersion and what you will hear in the sitting area, that can be highly variable with the program material.
My own home is about 1100 square ft., including the carport & patio.
Stereo pretty much sucks there, no matter what you do (everything has to appear relatively normal to the woman that I am married to from a non USA Asian culture. It's different than my normal growing up, to say the least). She is adapting pretty well, thanks to her having spent many years in Saipan & then Guam. But, still...

 

[Waxx]

Before Toole's research, not many knew about psychoacoustics and listeners' preferences. Sure they knew about on-axis linearity. But they knew very little about controlled directivity and the related psychoacoustics that follows.

If you really believe that speakers of the past are up to snuff, then name some make and model that are even remotely close to some of the best speakers today, of the likes of KEF, Genelec, Neumann, Dutch&Dutch, Kii, Perlisten, Ascend, Revel, Ascilab.

Those Neumann's are old "Klein & Hummel" designs that get refined, but the basic design is the same as the old ones. The KH420 goes back to the Klein & Hummel O96 from 1978

And the KH310 goes back to the O 98 from 1982

Both were active 3 way speakers with an electronic crossover build for the German broadcast industry, but also sold as studio monitors. The company was small and this was the time before internet, so they did not get over the ocean much, but in Europe, these were very popular at that time. And both are to today's standards still very good.

 

[Hipocrates]

Oh oh, I think that smack's gonna leave a mark.

Nah , but It kind of itch to be fair.

@MAB very cool amps, thanks for the review.

 

[ssashton]

I know I'm late, but just wanted to add my appreciation for this review. Always liked these amps but never knew quite how good they really were (some said they were not 'delicate'. Well, they ARE good! Quiet and clean and powerful.

 

[Count De Money]

i had a software problem on a bryston sp-3 audio processor i bought second hand . It was WELL out of warranty

i emailed them from australia and the solved the glitch for me. I even offered to pay their tech via paypal up front to help me but they said nope all ok.

Very good customer support