[pauldixonuk]

Getting some PMC IB2's soon. However my 4BSST is too quiet, so I'm going to upgrade to either one 14 or a pair of 7BSST pro series. Which would you go for? I've read the 14 may have a very slight edge. I suspect it's more a cosmetic decision as much as anything. In that case the 14 looks ok - one less button to turn on, plus one less power lead. Mind you, a pair of 7's looks ok too.

Any thoughts? What would you prefer personally?

[mr_bill]

Hi,
What does 'too quiet' mean?
A low noise floor is desirable or if it's volume, you won't gain that much volume by going with a 14 or 7.
Thanks,
Bill

[pauldixonuk]

I want more volume.

Why won't twice the power = more volume then?

[KJ]

Reviewing the PMC IB2 specs, it runs nominally at 4Ohm with a recommended amplification of 120W - 500W.  The 4B-SST puts out 500W @ 4Ohms, and I believe has approximately two 1.0 kVa torroids.     Additionally, Bryston almost always under rates their amps.  Check out your spec sheet - I bet it's quite a bit more than listed.

Doubling the amplification power will not result in twice the volume.  Do a Google search on "loudness" and "power."  You'll find a ton of sites explaining the math.

If you are looking for a "wall of sound," upping the amplification on that particular speaker may not result in what you are looking for.

-KJ

[Levi]

I am not sure about "quiet".

 If I will upgrade from a 4BSST, I would go with the 7BSST.  This should give you the warmth and full bodied sound you are not  getting in the 4BSST.

Levi

[KJ]

This should give you the warmth and full bodied sound you are not getting in the 4BSST.

How so?

Per James.

-KJ

[Levi]

My findings was confirmed by first reading a Canadian Hifi magazine for which I forgot the name.  It will come to me later.  Finally, I recently auditioned a Bryston 7BSST w/B&W Nautilus, SP1.7 as the pre-pro and managed a back-and-forth comparison with a 6BSST and  4BSST, the 7BSST sounded warmer in the bass.  The mids and top end are similar.

I have a 9BSST and it is nowhere near the sonic quality of the 7BSST.

Cheers,
Levi

This should give you the warmth and full bodied sound you are not getting in the 4BSST.

How so?

Per James.

-KJ

[KJ]

Finally, I recently auditioned a Bryston 7BSST w/B&W Nautilus, SP1.7 as the pre-pro and managed a back-and-forth comparison with a 6BSST and 4BSST, the 7BSST sounded warmer in the bass. The mids and top end are similar.

I can understand how there might be greater presence of bass if you were auditioning one of the larger Nautilus 800 speakers with the 7B-SST.  This would explain  why the mids and highs sounded similar.  When I think "warmer" I think tubes.   To each their own I guess.  

-KJ

[pauldixonuk]

The 4BSST may put out near to 500 w rms in 4ohms at max output, but this will be rather distorted. I find anything over 1 o clock on the preamp is less than ideal quality output. Therfore I can only use an absolute max of 60% of it's power = 300 w at 4 ohms.

Theoretically if I have twice this power I could easily use all 500 w rms (at 4 ohms into the IB2's) of real CLEAN power. This added headroom means higher volumes and higher fidelity at those volumes.

I'd like to know if anyone thinks this is all wrong.

Back to the question: would you buy a pair of 7's or one 14?

[jethro]

The 4BSST may put out near to 500 w rms in 4ohms at max output, but this will be rather distorted. I find anything over 1 o clock on the preamp is less than ideal quality output. Therfore I can only use an absolute max of 60% of it's power = 300 w at 4 ohms.

Theoretically if I have twice this power I could easily use all 500 w rms (at 4 ohms into the IB2's) of real CLEAN power. This added headroom means higher volumes and higher fidelity at those volumes.

I'd like to know if anyone thinks this is all wrong.

Back to the question: would you buy a pair of 7's or one 14?

You might want to try another pre-amp and source just to make sure where the noise is coming from.

[pauldixonuk]

I'm changing my entire system. Looking to compare the Bryston 26 pre with a mcintosh c2200 and an audio research LS25mk2. I think I'm going to prefer a valve pre as I recently heard one into some active ATC50's where it transformed them beyond all recognition, compared to solid state. The inbuilt dac on the 26 pre looks handy though. Not sure it will match the performance of a benchmark dac1 though (for dac duties).

Anyway, I think you'll find the slight drop of quality will be found in any amplifier when your getting close to max output. Or above 60% for that matter, IME anyway.

[KJ]

The 4BSST may put out near to 500 w rms in 4ohms at max output, but this will be rather distorted. I find anything over 1 o clock on the preamp is less than ideal quality output. Therfore I can only use an absolute max of 60% of it's power = 300 w at 4 ohms.

While some amp manufacturers may mislead the casual buyer and quote the rms value based on peak power, Bryston does not.  500 watts should reflect the true rms rating (at 4ohm) per conversations I've had with James on this subject.

Theoretically if I have twice this power I could easily use all 500 w rms (at 4 ohms into the IB2's) of real CLEAN power. This added headroom means higher volumes and higher fidelity at those volumes.

I'd like to know if anyone thinks this is all wrong.

There is a lot more to take into consideration.  First, wattage isn't everything.  I'd recommend reading Julian's comments in this thread.  Second, how large is your room?  Are you listening nearfield?  Is the room treated?  Loudness can be rather subjective.

Back to the question: would you buy a pair of 7's or one 14?

If the kVA rating is identical in each, then the decision should really be based on your preferences for room setup.

-KJ

[pauldixonuk]

kJ,

I am clearly not doubting my 4BSST has a MAX output of 500 rms into 4 ohms! What I am saying is this: I cannot use all 500 rms as it is not all CLEAN power! I can use maybe 60% of it's output before things start to sonically deteriorate. This equates to roughly 300 rms or so, USABLE into 4 ohms.

I want to fully power my IB2's. This means I want 500 rms of CLEAN power. Therfore I need an amp with MORE than 500 rms into 4 ohms, so I only have to use 60% of it's potential power. This will mean my power amps get an easy life, run cooler, run at lower distortion for any given power. It's all about headroom.

Anyway, I don't want twice the output volume! I just want an extra 15% or so, of pure, undistorted volume. That will be just right.

It's a bit like choosing your car. Would you rather thrash a little car with a 1.8 engine, or cruise along with a 6.0 V8. Same speed, different refinement. Understand?

[dan_lo]

pauldixonuk wrote:
The 4BSST may put out near to 500 w rms in 4ohms at max output, but this will be rather distorted. I find anything over 1 o clock on the preamp is less than ideal quality output. Therfore I can only use an absolute max of 60% of it's power = 300 w at 4 ohms.

I disagree.
 The 500w is the maximum CLEAN power to 4ohms. This value combined with the  effiency of 89DB will give you max SPL level of ~115 DB (1 m), which is about as high as the IB2 can reach,and more than enough for most people.

This rule of "everything higher than 1 o'clock" is relevant if the amplifier does not have enough current reserves.  For example - if you tried to push a speaker with nominal impedance of 1 Ohm, your amplifier would "choke" even before you reach 12 O'clock on the volume control.
But the 4sst has enough current reserves for 4ohms speakers.

[pauldixonuk]

Forget theory and numbers! It's what it sounds like that counts.

I listened to the IB2's with my 4BSST. It sounds great up to 60% of full power (1 o clock on preamp). Above this level it slightly distorts, which makes the song sound more harsh. Vocals stop being smooth etc.

I just want it slightly louder and MUCH cleaner at this high volume. I trust my ears, not some figures on paper, thankyou.

[dan_lo]

I listened to the IB2's with my 4BSST. It sounds great up to 60% of full power (1 o clock on preamp). Above this level it slightly distorts, which makes the song sound more harsh. Vocals stop being smooth etc.

I just want it slightly louder and MUCH cleaner at this high volume. I trust my ears, not some figures on paper, thankyou.

Let me put it this way:

If you are right - then Bryston's/PMC specs are completely false. Do what you will with this information.

[pauldixonuk]

I give up. Obviously spec sheets are more important to you than listening to music.

[brucek]

Back to the question: would you buy a pair of 7's or one 14?

My feeling is that the 7B (being a mono block design), allows you the luxury of locating each amp very close to your speakers, facilitating super short speaker cables (down to 3 gauge on the post) with all the benefits derived from that configuration.

Because the speaker connection is in the order of 4 ohms, a long speaker cable, particularly one of high gauge can become an appreciable proportion of the speaker impedance and as such can affect a signal loss resulting in a change of system response and decrease system damping. The system damping formula is almost exclusively driven by the speaker cables impedance, which is a function of its resistance and inductive reactance (capacitive reactance can be ignored here).

Personally, I'd choose two 7B's over the 14B.



brucek  

[KJ]

Forget theory and numbers! It's what it sounds like that counts.

I guess the best solution for you is to find some to listen to.  Jimmyp58 used to own both.  You may want to send him a pm and get his opinion.

-KJ

[pauldixonuk]

I think I'll get a pair of mono's so I have the added flexibility of installation. Plus they'll be easier to move one each, rather than one 14 at a time. Thanks for the input guys.