TSP are scalar - queries

[hollowboy]

T/S parameters are curves not scalars. When you collapse them to a number its value depends on where you pick it off the curve.

I remember (and Wikipedia reminds me / confirms it) that Fs & Qts drop and VAS rises as signal level increases. I remember once seeing a webpage where this was measured for a cheap pro woofer - but I can't find that info now. From memory, the woofer was well off spec (Qts high) at 1 watt, but closer to spec with 100 watts. I think it was a P Audio woofer.

Anyone got any links / info on this (actual examples)?

Btw, most comercial designs are intentionally bumped, not maximally flat, to match mainsteam consumer taste.

Presumably, with appropriate data, one could design so that these two ideas come together nicely. If you had:

1. a woofer with high Qts (measured small signal) and ~0.7 Qts at high level
2. an enclosure insensitive to VAS (so that the Qts was the dominant effect as signal changed)

...the bass would be slightly bumped on quiet music, but flat at higher volume. A built in "loudness" button.

The catch is: is any enclosure insensitive to VAS, good for bass and not huge?

The best examples I can think of would be an IB or big fully-absorbing line (something like the el pipe-o sub, but with more stuffing) - and while they do make good use of floor area, they aren't dainty

 

[TBTL]

Not answering your question, but strictly speaking, TSP only define behaviour at low drive levels, at which the behaviour should be constant with respect to drive level.

 

[hollowboy]

Found something: this is from the advertising material for the Smith and Larsen Audio Woofer Tester Pro site.

Their website has an error (bad URL) for the Qts graph, so I'm posting it here.

In their graphs, at high power:

VAS ~doubles
Fs frops ~25%
Qts drops ~35%

 

[hollowboy]

Found something else:

Morel (for at least some of their products), show both the small signal values, and the non small signal (1V) values.

e.g. MSW-144 Slim 5" Woofer Ø 5", Ø 3" voicecoil, 8Ω
Small Signal vs 1v

0.44 -vs- 0.36 (Qts)
50.5 -vs- 42.5 (Fs)
8.2 -- vs- 11.8 (VAS)

Roughly a 20% difference.

SB acoustics are odd, in that their tech note for "Measuring Thiele/Small parameters" is actually telling you to measure a 1V value: "For a typical mid-woofer, the voltage should be about 1 V (rms) at the resonance frequency".

When I bought a quad of 12-sb34nrx75-6/ (advertised Qts of 0.4, presumably measured at 1V), they had Qts >0.5 when measured with small signal.

Roughly a 20% difference.