Spinorama.org

Published

February 2, 2025

Abstract

Help for the spinorama.org website. How to understand the graphs? What is a Spinorama? Why you should care?

Measurements

What is a spinorama set of graphs?

It is a way to understand quickly a speaker properties, how it will sound. It is defined as a standard from the from the US CTA.

Here is an example: Genelec 8341A

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
  • Sound power: expected to be a smooth, slowy going down line (slope is greater than Early Reflections for classical speakers).
  • 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 linear, 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 an IIR eq. The slope of the line gives a good idea of the speaker properties. Note that you will not get a flat line except for speakers designed for this (and they are usually large): they are usually labelled as constant directivity speakers.

The speaker above is very good. You can compare with another one:

Tannoy XT6

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.

Tannoy XT6

Please tell me more

If you like to read:

If you prefer to watch:

There is a fine set of videos from ErinsAudioCorner on Youtube:

How to select a 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 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?
  • Do you have multiple subwoofers to control bass linearity?
  • Did you measured your speakers in your room?
  • Are you using a room correction software?

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 Great speakers need a great room to reveal all their potential. At the same time, I understand very well the appeal 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.

How to interpret the numbers on the landing page?

Each speaker measurement shows up in a box similar to:

Example for one speaker on the landing page

  • Price: should be self explanatory; it is in USD per speaker not for a pair. The price was the first hit on Google when I looked it up. It may be different in your country and/or later in time.

  • Tonality: this is a value between -10 and 10. It is defined in the CEA2034 standard and is computed from the spinorama data: Higher is better.

    • It make sense for tower, bookshelves or center but not for surround, in-wall or column speakers; if you see *** instead of a number, it is to remind you that the score is not valid for some shapes of speakers. If you go to the page of a speaker you will still still see the computed value. It needs to be taken with care. It may “work” for some speakers but not for others. The predicted in-room response assumes a rectangular room with standard reflection and a dipole speaker. All bets are off for a stadium or an omnidirectional speaker.
    • Note that a difference between two scores is only significant if the difference is greater than 0.6.
    • Be also mindfull than smoother or less precise data can yield a higher score than an Klippel generated set of data for example. You can easily remove 0.5 to 1.5 to the score for highly smoothed data.
    • The score does not tell about maximum output or about distorsion. You can get the same score for a portable bluetooth speaker and a large tower.
    • If you know how to read code, you can find my implementation in Python here. There is also a version in Cython which is faster if needed in the same repository.

  • Bass extension: this is low frequency extension (LFX in short) from a research paper from Olive. It is computed as here. Lower is better.

    Note that it is slighlty different from the frequency of the -3dB point. The rational for using it is:

    • The low frequency extension (LFX) LFX = log10(xSP-6dB.re:y _ LW(300Hz-10kHz) where LFX is the log10 of the first frequency x_SP below 300 Hz in the sound power curve, that is -6 dB relative to the mean level y_LW measured in listening window (LW) between 300 Hz-10 kHz.
    • LFX is log-transformed to produce a linear relationship between the variable LFX and preference rating.
    • The sound power curve (SP) is used for the calculation because it better defines the true bass output of the loudspeaker, particularly speakers that have rear-firing ports.

  • Flatness: This is the variation in dB around the average SPL of the on axis measurement between 300Hz and 5kHz. Lower is better.