Preamp difference : if it's not the frequency, not the slew rate, and not the harmonics, what is it ?

[abbey road d enfer]

The issue of back spillage is now commonly dealt with cardioid design.
The active solution, which uses additional drivers and amps, is quite expensive.
The passive solution, based on a principle similar to that used in cardioid mics (acoustic delay in the backpath) is more suitable for cost effective products.
It is applied only to the LF section, since the mid and HF are usually horn-based, with a natural directivity.

 

[JohnRoberts]

My studio monitors, made by Wayne Jones Audio, now come with carbon fiber boxes and the new model does sound different than my model without the carbon fiber. Not a huge difference, but noticeable.

of course the sound not leaking out the back, comes out the front.

Cabinet rigidity was an issue mostly for bass response in molded plastic cabinets (back last century when I was over all product management for Peavey). Adding a wood internal strut to stiffen up the plastic cabinet helped, but the extra weight worked against the light weight selling feature.

JR

 

[kags]

of course the sound not leaking out the back, comes out the front.

Cabinet rigidity was an issue mostly for bass response in molded plastic cabinets (back last century when I was over all product management for Peavey). Adding a wood internal strut to stiffen up the plastic cabinet helped, but the extra weight worked against the light weight selling feature.

JR

These speakers, even without the carbon fiber, have heavy, rigid solid wood cabinets. The monitors weigh 45 pounds, so I assume any rearward sound is diffraction/baffle step below 250 Hz or so. The builder says the carbon fiber reduces cabinet resonances, which would be internal and would not affect leakage.

Plastic speaker cabinets sometimes benefit from a layer of dynamat or mass loaded vinyl, too.

 

[Cqwet Dbdfte]

Rauna speakers used concrete for enclosures.
Not really related to pre-amps though...

 

[RoadrunnerOZ]

Rauna speakers used concrete for enclosures.
Not really related to pre-amps though...

Maybe granite could be a contender? Little heavy though but would look good - a lot denser than concrete.

 

[Cqwet Dbdfte]

The speaker enclosure material should not be resonant, have great damping, have strength, easy to work with, looks not relevant to sound output. Added mass is a bonus. Concrete is probably overkill. Granite should work fine, not the easiest to cut. Fred Flintstone would approve. I'll stick to MDF.

 

[CLASS-A]

Hi,

I took the opportunity to measure different preamps (new SSL ones, Focusrite Scarlett, Warm Audio TB12), and investigate a bit on the topic of "audible differences between preamps".

If we run the preamps too hot, I came to the following conclusions :

• The preamps are usually rather flat in terms of frequency. At least nothing that couldn't be fixed with some basic digital EQing. Example : Measurement of an API312 here on SoundOnSound
  So it seems unlikely that frequency response is really what differs between preamps.
• The harmonics are of course different, in the case of transformer-balanced preamps. But they are usually at a rather subtle level (unless the preamp is pushed).
• The slew rate of the preamp usually seems to allow for a correct reproduction of all the audible frequencies.

So now I am wondering :

1. Why would a preamp like the API be called "punchy" ? What would "punch" be ?
2. If it's a variation of the transients (we hear about "slow" vs "fast" preamps), then where does it come from if the slew limit is > 20000 Hz ? The transformer ? If so, aren't the transformers supposed to be rather transparent, harmonics put aside for the lower frequencies, in the frequency range ?
3. Would the slew rate, if a bit too low, be able to influence the audible frequencies (even if the amplifier would, on paper, be able to reproduce those frequencies without any problem) ? It seems so : https://hifisonix.com/wp-content/uploads/2018/03/SID_and_TIM_W_Jung_77-79.pdf
4. Did I miss any phenomenon ?

I've searched all around the Internet but I can't find a clear answer.
Everyone seems to hear punch and smoothness differences, and I feel I hear them too, but where does it actually come from ? Has anyone been able to 'demonstrate' that ?

Thanks
Adrien

Hi Adrien
I made the same observation and during my various projects I tried to understand what could be happening. My (provisional) conclusion is that these differences are attributable to dynamic and not static aspects because measuring harmonic distortion in steady state on a sinusoidal signal is (I think) not very representative. When the components are well chosen and well used, the effects of DHT, slew rate and noise at these infinitesimal levels do not seem to me to be detectable by the human ear. The level differences and therefore the "punchy" aspect that you speak of are not integrated into this measurement protocol. The load impedance in relation to the current capacity must have a probable influence on this parameter. Finally, for line stages or microphone stages integrating an audio transformer, the characteristics of this component are essential for the sound signature. If we talk about legendary analog consoles like the Neve or SSL, they are all made from NE5532 or 5534 type circuits and even some with TL07n. However, these circuits are very inferior to what we can have today and yet the sound of these consoles is very appreciated and often considered "better". Is this a collective illusion linked to psychoacoustics. I don't have the definitive answer but I'm not entirely convinced that this is the case. What I noticed is that nowadays OPAMPS are often designed with consumption constraints which perhaps limit dynamic performance. In addition, I deliberately ignore the fact that the open loop bandwidth is very limited and the gain is very high which thanks to the feedback allows a high bandwidth and very low distortion but be careful, this is measured in steady state and not in impulse mode. However, under these conditions, the internal amplifier stages can go into saturation for a very short time and cause audible differences.Daniel