What speaker is commonly used for low-latency audio stimulation
There is generally an intervening stage between the sound card and the speaker, the amplifier. From the output of the amplifier to the speaker, there is an electrical signal traveling at like 0.01C that then drive the speaker via an electromagnet. The transmission and transduction time is essentially zero. Further, you can safely ignore any jitter.

For powered speakers, or amplifiers, there are all sorts of models. Some might have some built in filtering that could introduce a delay, but it is probably negligible.