It is a way to understand quickly a speaker properties, how it
will sound. It is defined
in this
standard from the USA CTA.
Here is an example:
The spinorama gives you a few graphs:
On Axis: this the frequency response of the speaker on axis. You expect it to
be as flat as possible above 100Hz.
Listening Window: this an average of various
measurements around on axis. The idea is that it is closer to real
life since your head is always moving a bit in practice and you
are not staying frozen in front on the speakers. It is expected to
be close to the previous one, slighlty going down.
Early reflections: expected to be a smooth, slowy going
down line.
Sound power: expected to be a smooth, slowy going
down line (slope is greater than Early Reflections).
ERDI and SPDI: are the difference between the Early
Reflection curve and the Listening Window (resp. Sound Power and
Listening Window). This should be as straight as possible above
100 Hz. If the DI curves are flat, you will be able to correct the
frequency aberations of your speaker easily. It is important to
understand that a bad directivy cannot be corrected with a IIR eq.
The speaker above is very good. You can compare with
another one:
which is not flat at all. Remember that ±3dB means that the
volume doubles/halves at the corresponding frequency. If you look at
the on axis measurement below, you see that it going up, the
speaker will likely be bright and emphasis high frequency.
Please tell me more:
If you like to read:
You can go to the source
(the
standard document) and starting page 56, you have a good and compact explanation of each curve.
The measurements are collected on the internet. Some are of very
high quality and done by independant reviewers, some are of medium
or low quality or provided by vendors.
You can filter the results by clicking the wheel on the website near
the search bar.
How precise are the measurement data?
High quality data: provided by a Klippel NFS or measured in a large
anechoic chamber. Data precision is around 1%.
Medium quality data: medium size anechoc chamber, data
precision decreases <500Hz. By how much is unknown.
Low quality data:
measured without an anechoic chamber but
using windowing for high frequency and plane ground method for low
frequency. Precision can be as good as a Klippel
measurements.
provided by vendors: usually smoothed data (less
measurement points, or data is smoothed, or quality is just
unknown). Smoothed
measurements usually
generate a score
which higher by 0.7 on average over a score computed raw
data. Note that the 0.7 can change depending on the amount
of smoothing and other factors.
How precise are the computed data?
Generally precision depends on the quality of the input
data. If you want to compare 2 measurements, you should select
them from the same category.
Score computations
The score is not significant ±0.5. It means that 2
speakers which have a difference in score less than 1 are in
the same broad bucket. No point to look at the decimals.
Anechoic EQ computations
EQ is for one measurement. Since there are variations
speaker to speaker, you should not look at very sharp or very
precise EQ. How much variation between speakers? This is very
brand/model dependant. Some manufactures provide tolerance
like Neumann or Genelec.
IIR eq (aka PEQs) are not working if the phase is varying
a lot over some frequency range. Group delay (phase
derivative) must be relatively flat. That may explain why EQing
around the crossover frequency does not necessary give
excellent results. On this other side, we are less sensitive
to phase anomaly than frequency anomaly.
Can I use this data to decide which speaker to buy
See dedicated section.
Should I use room EQ?
Absolutly! Dirac, REW, Audyssey etc will provide audible
improvement to the sound, in general making it flatter (so more
tonally correct).
Focus or broad radiation pattern?
Speakers do not radiate uniformly. Some speakers are designed to be
very focus: they minimise the reflections but the sweet spot is very
tiny. Some speakers are designed to diffuse sound, research proved
it is something that people usually like.
If you are near field, for example on a desk, low directivity works
well. The farther from the speaker you are, the more good
directivity becomes important. If the room is reflective, this is
especially important.
How can I help?
This website is generated
from this
code and data from various websites (see below).
You can provide feedback or add more datas
at github
or in
this thread
at ASR.
How to select your speaker?
That is a polemic section, I know, I know.
Criteria
I believe there are a few criteria in whatever order you want:
Price:
Price is not linked to quality (sadly) and is a factor where
you are the only judge of the worthiness.
Design:
Design is to each is own. Some like monkey coffins, some like
studio monitors, some like big horns, it is up to you
Build quality:
Some brands built to high standars some don't. Do some due
diligence.
Support quality:
Who can or will repair your speaker if you have an issue?
How long do they store parts? How long is the guarantee? What
is covered. It is worth a close look if you buy once in a
lifetime expensive speakers.
Tonality:
Here we have more concensus, a lot of people like the same
thing. To be HIFI, you want to have a speaker with a high
tonality score. This score takes into account flatness,
directivity and how much bass you will get.
SPL aka Sound Power level:
How loud do you want your speaker to be? It depends a lot of
your room and at which level you want to listen.
Some examples:
Bedroom 3m x 4m, listening distance <2m, 73dB reference
level, +20 dB for peak: 93dB at 1 meter. Around 90dB per
speaker.
Living room 6m x 8m, listening distance <3m, 73dB reference
level, +20 dB for peak: 93dB at 1 meter. Around 96dB per speaker.
Large room or studio 7m x 12m, listening distance <5m, 73dB reference
level, +20 dB for peak: 93dB at 1 meter. Around 116dB per speaker.
Bass extension:
Small speakers dont have much bass. You need a subwoofer or a
large speaker if you want both deep bass and high volume. New
speakers with DSP can produce a lot of bass while being small
but not at high volume. If you listen to music only and do not
like electronic music, you dont need subwoofers with large speakers.
Some examples:
Bedroom 3m x 4m, one 10 inch subwoofer.
Living room 6m x 8m, one 15 inch subwoofer or two 12 inch subwoofers
Large room or studio 7m x 12m, two 15 inch subwoofers, may
be more
You can choose floorstanders or bookshelves with
subwoofers. Integration is not very easy but very doable
especially if you use an AVR. Most people like bass, your
neighbourgh may not like your bass.
How good is your room?
Is the room dedicated to music?
Is the room symmetrical?
Does the room have some absorption?
Did you add panels to control reflections?
Did you have multiple subwoofers to control bass linearity?
Did you measured your speakers in your room?
If you did not answer yes each times, then you do not need the best
speakers in the world and obsessing over scores, SPL etc will not
make it the best room in the world.
At the same time, I understand very well the attraction of having a
great pair of speakers.
Speakers with a high tonality score will be easier to EQ and will
adapt well to your room. Define the SPL you want (at 1% distorsion)
and now you have reasonable choices.
Source of data and citations
AudioScienceReviewaka
ASR: it is a fantastic source of speakers data thanks
to amirm@. They
also have a lot of data about DACs that you may found useful. There is
little correlation between price and quality in the audio world and
this data gives some objective criteria to decide what to buy. You can
support
ASR.
They provide a database of speaker measurements
(manual)
Some scientific papers I have used:
Metrics for Constant Directivity (abstract,
paper, poster)
Authors: Sridhar, R., Tylka, J. G., Choueiri, E. Y.;
Publication: 140th Convention of the Audio Engineering
Society (AES 140) ; Date: May 26, 2016
A Database of Loudspeaker Polar Radiation Measurements (abstract, )
On the Calculation of Full and Partial Directivity Indices
(abstract);
Authors: Tylka, J. G., Choueiri, E. Y.; Publication: 3D3A Lab
Technical Report #1; Date: November 16, 2014
speakerdata2034
is a blog with a collection of spinorama from various
sources. Index of measurements is available.
Standard Method of Measurement for In-Home Loudspeakers is
available for free at CTA
A Multiple Regression Model for Predicting Loudspeaker Preference
Using Objective Measurements: Part II - Development of the Model
by Sean E. Olive, AES Fellow. Convention paper 6190 from the AES.
Farina, A. “Simultaneous Measurement of Impulse Response and
Distortion with a Swept-Sine Technique,” Presented at the AES
108th Convention, Feb. 2000.
Hatziantoniou, P. D. and Mourjopoulos, J. N. “Generalized
Fractional-Octave Smoothing of Audio and Acoustic Responses,”
J. Audio Eng. Soc., 48(4):259‐280, 2000.
A. Mouchtaris, P. Reveliotis and C. Kyriakakis, "Inverse
filter design for immersive audio rendering over loudspeakers," in
IEEE Transactions on Multimedia, vol. 2, no. 2, pp. 77-87, June
2000, doi: 10.1109/6046.845012.
M. A. Poletti and P. D. Teal, "A Superfast Toeplitz Matrix
Inversion Method for Single- and Multi-Channel Inverse Filters and
Its Application to Room Equalization," in IEEE/ACM Transactions on
Audio, Speech, and Language Processing, vol. 29, pp. 3144-3157,
2021, doi: 10.1109/TASLP.2021.3120650.
