BLOG #48. Just Published New Sets of Measurements of StereoPravda SPearphone SB-5/SB-7/SB-7A Family of Earphones


BLOG #48. Just Published New Sets of Measurements of StereoPravda SPearphone SB-5/SB-7/SB-7A Family of Earphones

A few days ago, Roman Kuznetzov of kindly re-measured the whole StereoPravda SPearphone family of our earphones and published the data at his (very informative) web site:

As I see it, one of the most interesting aspects of this last series of measurements is an ability of direct comparison of Frequency Response curves of all our earphones between each other, especially between the SB-7’s FR and the SB-7A’s one.

As I mentioned on numerous occasions before, the earphone technology based on “passive” implementation of historically happened nomenclature of the current BA-drivers – which is practically unchanged for more than several decades – and even in its multi-way incarnation, allows to build only: either high resolution products, or wide frequency band products (I am talking mostly about low end extension here).

But not both at the same time.

The only way to “have your cake and to eat it” is via application of a multi-way “active” configuration of separate BA-driver sections, where each earphone section has got some necessary adjustments on the board and is driven but its own separate amplifier.

And the latter is exactly what is happening when our SB-7A are driven by our dedicated differential DAC/Control audio processor/two-way separate Amplifiers-in-one DACCA unit.

For this set of tests Roman Kuznetzov measured the SB-7A when the earphones were hooked up to the DACCA unit, with the latter’s all adjustments having been set up via my own previous personal extensive auditioning of the combo (and which were stored in one of the unit’s memory slots).

So, compared to its “passive” version bearing SB-7 moniker subjective auditioning confirmed an elevated level of sonic resolution of our ear monitors’ “active” version implemented via SB-7A/DACCA combo (unfortunately, we can’t resort to any objective measurements procedures in this area yet).

At the same time the direct comparison of SB-7 vs SB-7A FR measurements plots also demonstrates - with all the objective certainty - much more extended Frequency Response at the low end of the SB-7A ear monitors.

Which are, again, exactly the same as the ordinary SB-7 with the only exception that SB-7A’s cable is configured the way that they can be specially adjusted for in each of their two “active” bands and to be driven by two separate amplifiers in each channel via our portable DACCA unit.

Below is the RAA measurements test procedure description and the measurements report.

The Description of the Test Rig

The StereoPravda SPearphone SB-5 and SB-7 ear monitors’s shape is not conventional and are intended to be positioned deep within an ear canal.

A typical ear monitor measurement rig is usually employing an ear canal chamber of an average size that wouldn’t allow to measure these models due to their deep insertion positioning and a complexity arising from their silicon tip design’s method of sealing an ear canal.

The measurements were taken at Reference Audio Analyzer’s lab:

For the measurements in the lab a special rig was built, in which a microphone was positioned at a depth of 6 mm inside a special chamber (emulating conditions when an ear monitor is deeply inserted inside an ear canal). To allow the measurements the earphones’ silicon tips were pressed against the chamber’s surface to ensure a perfect seal.

Besides the Frequency Response plots of a particular product you can find at the RAA site some direct FR comparison plots of different products between each other, and also you can find there sensitivity and power ratings charts for a wide range of products.

The main plots

The title links to particular products:

StereoPravda SPearphone SB-5:

StereoPravda SPearphone SB-7:

StereoPravda SPearphone SB-7A:

From the title pages you can also pass to various reports and online services.

Some links to particular plots

The sensitivity and FR plots:
(under the plots you can choose a channel)

StereoPravda SPearphone SB-5:

StereoPravda SPearphone SB-7:

General Comments

Both of these models have a similar sensitivity – 133 dB/V, or 114dB/mW at 16 Ohms.

The value a little bit higher than an average value for the ear monitors. The most of the source components would play nor too loud, nor too quiet with these ear monitors (with some external noise).

Their FR- plots are very even both at the low-, and at the mid- frequencies.

The uneven shapes of the FR plots at the high- frequencies are due to the resonances in the ear monitors’ sound tubes and to resonances within the measurement chamber. The resonances central frequencies values depend on the ear monitors’ positioning within an individual ear canal. That’s why these values would slightly change for each individual.

SB-5 vs SB-7 FR plots:

SB-7 vs SB-7A FR plots:

Impedance Measurements

StereoPravda SPearphone SB-5:

StereoPravda SPearphone SB-7:

The ear monitors’ impedance is 16 Ohms and the plots are very even.
This parameter would affect an FR change when the earphones are connected to a source.

So, the FR of these particular ear monitors would not change when they will be connected to the vast majority of all sorts of different source components:

But in some extraordinary cases, when the source components would have their own very uneven output impedance, the ear monitors under the test can demonstrate a diminished low frequency FR:

11.08.2018 // Author:  (Bigmisha) // Number of views:  1680

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