Stereo systems

Stereo systems 2

These are my loudspeakers in my new listening room. Notice the thick double carpets on the floor and lots of dampening around the room! The speakers were constructed by Ingvar Öhman at Ino Audio and are the "Ino pi60 signature" model with bass-support – not the same thing as a sub-woofer – and the latest version of the elements and filters. For serious listening one has to use damping especially on the floor, but also on the wall behind the speakers and in other various places in the room. The damping behind the speakers are in three layers, and improves the clarity of the sound immensely.

This is the back of the room and the listening area. One can see some of my records in the background.
To the left there is a desk with a computer and programmes to edit music.

The system has a capability to deliver a sound pressure level of more than 126 dB at 100 Hz and more than 115 dB over 20 – 20.000 Hz. I will come quite close to this maximum performance level with the very powerful and neutral sounding Rotel amplifiers RC-1090 and RB-1080, that in this configuration into 4 Ohms can deliver around 450 Watts. To have a big headroom is important for any speaker or system, to give very low distortion at normal listening levels. A speaker or system that does not have a strong dynamic capability will not sound correct. So the whole system must work at on only a fraction of its capability, to be able to deliver a true representation of the recorded sound.

The speakers have a frequency response of ± 1 dB over 24 – 26.000 Hz and are extremely durable. I have seen the measurements made by Ingvar Öhman, but I do not have them at hand for publishing. The measurement below is made at the Technical University in Luleå. (Remember that the room will add sound in the bass and the frequency response is adjusted so it will be flat in a real room).

The very carefully calculated frequency response is in fact a little different in different directions. The explanation for this is too extensive to be discussed in depth here. But, the transmission of the direct sound should be nearly straight, except in the lowest bass register, as the wall behind the speaker will add to the sound. But, due to system errors, all stereo systems – with the limitations of radiating sound with only two speakers – cannot present a sound image compatible with the concert hall. The adjustments needed to correct for these "system errors" are very minute, and within 1 dB on the axis of the direct sound. From other directions from the speaker, the frequency response should be slightly altered to enhance the speakers presentation of the sound image in a correct way.

The bass element (in the main speakers), can stand more than 1,5 kW of power and extreme accelerations in excess of 800 G! The maximum transient power is in fact over 10 kW with reasonable distortion. The bass-element has a frequency response that is linear (up to 6 kHz ± 1 dB) and has extremely low distortion. The voice-coil is of titanium and is wound in two layers with a two-layer wire (copper over a core of aluminum). The treble element will create a perfect spherical wave up to more than 20 kHz and has therefore an exceptional spread of the sound. It can handle signals in excess of 150 volts.

These loudspeakers are something special. It is difficult to describe the sound.
But they may be as neutral as it is possible to achieve today.

This is the pulse-response for the pi60s speaker. A really exceptional performance!

For comparison the pulse response for another Swedish speaker the Audio-Pro A4-14 and the B&W 801.
The last speaker is presented closer at the bottom of the page.



These are the Bower and Wilkins 801. They are a studio standard for many big companies such as Deutsche Grammophon, Decca or EMI. You can see from the frequency response that they have a somewhat swollen sound (for some unclear reason this is a bit typical for some very expensive speakers). This loudspeaker costs 114.800 skr in Sweden, which is about 12.700 Euros. B&W says in their technical description that the frequency response is 37Hz – 20kHz ± 2dB on the reference axis. Not bad, but not as exceptional as 24Hz – 26kHz ± 1 dB.

The new version for 2005, the Bower and Wilkins 801 Nautilus D, has new elements and cross-over electronics, and a tweeter whose membrane is partly treated with diamond-dust, to push the resonance frequency over 20kHz. It's a clear improvement. But the price is no improvement and is now 146.800 skr, which is about 16.300 Euros. The frequency response for the new model is 29Hz – 28kHz ±3dB on reference axis which also is an improvement. The speaker is -6dB down at 23Hz and 33kHz, an improvement but not as good as 24Hz – 26kHz ± 1 dB. But the price tag is just too much, and you also need a powerful amplifier to power them.

In 2010 there was an update of the 800 series.





These are the Bower and Wilkins 802 Nautilus loudspeakers. They are used by the record company Hyperion and have really a somewhat better frequency-response than their bigger cousin 801. They were considered by Hi-Fi&Musik in 2004 (and now 2005 for the model D) to be the very best of all speakers tested for a long period. This loudspeaker costs in Sweden 83.800 skr, which is about 9.300 Euros. Ingvar's speakers are at about half the price and will outperform these speakers on most objective parameters. B&W says in their technical description that the frequency response is 39Hz – 20kHz ± 2dB on the reference axis. Not bad, but not as exceptional as 24Hz – 26kHz ± 1 dB.

The new version for 2005, the Bower and Wilkins 802 Nautilus D, has new elements and cross-over electronics, and a tweeter whose membrane is treated with diamond-dust to push the resonance frequency over 20kHz. It's an improvement. But the price is no improvement and is now 109.800 skr, which is about 12.200 Euros. The frequency response for the new model is 32Hz – 28kHz ±3dB on reference axis which also is an improvement. The speaker is down -6dB at 25Hz and 33kHz. Again an improvement, but not as exceptional as 24Hz – 26kHz ± 1 dB. Still there is a problem around 1,6 – 3 kHz, where the response is subdued and gives the typical "closed sound" of the speaker. But the price tag is just too much, and again you also need a powerful (expensive) amplifier to power them.

Remember, as was mentioned above, that the frequency response is just one of the vital parameters in the delivery of excellent sound quality. And the parameter that I have chosen to describe differences between loudspeakers, mikes, concert halls and recordings. It's one of the most important factors and one which can be clearly heard without any special training.

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