Here are a few options depending on the context:
* A panel of speakers: This is a common term for a group of speakers presenting at a conference or event.
* A group of speakers: This is a general term that can be used in any context.
* A chorus of speakers: This implies a large number of speakers speaking in unison.
* A parliament of speakers: This is a playful and slightly unusual term, suggesting a group of speakers debating or discussing a topic.
Ultimately, the best collective noun to use will depend on the specific context and the desired effect.