Physics and HiFi

[Christian_Thomas]

I expect you can pick them up on a night visit to your local railway sorting junction. You’ll probably need an F150 and a reasonably stocky mate.

The fun thing here would be to ask them if you can do an A/B with NACA5.

Surprisingly, they are tackling a very real problem, though this solution shows the free rein insanity has been given in the hi fi industry. The problem is that the Ground in the speaker’s crossover is always a little bit away from 0V because of the resistance of the speaker cables and this puts a floor under the maximum attenuation any of the crossover circuits can achieve. Usually that’s not as small as you’d ideally like, and you can tell that from the ratio of the resistances. The 4mm^2 cables, like NACA5, have a DCR of about 0.02 ohms, IIRC, for their 10m round trip versus 3-7 ohms for the speaker DCR, so your crossover might only manage 40dB of roll off before giving up, if that! There is no way around this if you are going to put the crossover in the speaker. Needless to say, half a tonne of copper is not the right solution.

[Edmund-of-Essex]

Hi Christian

PS: Thank you for posting on my thread about ‘audio grade solder’ - much appreciated.

However I would like to address your posting here as it misrepresents what Linn Space Optimisation actually does.

You are correct in stating that the ‘final column’ (i.e. acoustic impedance) in the chart posted by Fatcat will influence the magnitude of sound pressure getting into the room. However this is not relevant for the basic level of what Linn Space Optimisation does.

Linn Space Optimisation uses computational fluid dynamics calculations to model the ROOM ACOUSTIC behaviour and its impact on the sound at the listening position. Addressing your point specifically, Linn SO assumes ‘idealised’ point source stimuli for the low frequency driver(s) in the loudspeakers and also includes models for the ports if they exist. So the basic Linn Space Optimisation does NOT model the effect of air temperature and humidity on the acoustic impedance at the driver.

Nevertheless, the ROOM ACOUSTIC behaviour absolutely is influenced by temperature (and to a lesser extent humidity) as this significantly affects the low frequency room resonances (centre frequency and bandwidth) and accordingly results in audible differences if the temperature and humidity effects are not included in the Linn SO calculations correctly.

I hope the above is a sufficient explanation?

PS: I do have acoustic measurements showing what happens if the temperature and humidity are not modelled correctly in Linn SO.

PPS: There are enhancements to Linn Space Optimisation, called Linn Space Optimisation+. Which, the Linn website claims, “(with Exakt) incorporates the measured response of every individual drive unit. It enables even more advanced speaker modelling that’s specific, not just to the model of speaker, but to the unique pair of speakers in your home.”

So I guess if you think that Linn Products Ltd are making a claim that is “fantastical and comical”, I encourage you to challenge them and get them to prove that what they claim is functionally and demonstrably correct (that’s what I did on a related matter of Linn SO). Because if Linn Products Ltd cannot demonstrate a valid claim the Advertising Standards Authority would want to know, and purchasers of Linn equipment (using Linn SO) would also want to know that the money paid is for something that is “Fit for Purpose”.

All the best.

E of E