Designed for real-time use, it combines multilingual speech, voice cloning from seconds of audio, and conversational-level prosody in a single system
San Francisco, CA: Smallest.ai, the research-first Voice AI company building proprietary speech models and production-grade voice agents, today announced the launch of Lightning V3, its most advanced text-to-speech (TTS) model for real-time, conversational AI.
In conversational evaluations, Lightning V3 achieves a 3.89 MOS, outperforming leading models from OpenAI, Cartesia, and ElevenLabs, while also leading on intonation (3.33) and prosody (3.07)– two of the most critical factors for natural, human-like speech. The model combines this performance with multilingual support, instant voice cloning, and streaming generation designed for real-world interactions.
Most TTS models today are still evaluated on complete sentences generated in isolation. That setup is easier to optimize for, but it doesn’t reflect how voice systems actually behave in production- where audio is generated in chunks, context is incomplete, and responses have to adapt as conversations unfold.
Lightning V3 is built for how voice systems actually run in production- generating speech in chunks, without full context, and adapting as conversations evolve. It maintains consistency across turns and adjusts tone and pacing mid-sentence, which is where most systems break down.
That same setup allows the model to work across use cases without retraining- including voice agents, contact centers, podcasts, audiobooks, dubbing, and interactive applications.
It supports 15 languages with automatic detection and mid-sentence switching, and can clone a voice from 5–15 seconds of audio. These cloned voices tend to sound more natural than preset ones, since they retain the variations of real speech.
The model outputs audio at 44.1 kHz, and can be downsampled to 8–24 kHz for telephony.
“Conversation is where most voice systems fall apart,” said Sudarshan Kamath, Founder and CEO, Smallest.ai. “It’s not just about sounding clear- the voice has to track context, timing, and emotion at the same time. If it works there, it works everywhere.”
A shift in how voice quality is measured
The launch also challenges how voice models are evaluated. Most benchmarks rely on static outputs- a setup that rarely reflects real usage.
Lightning V3 is evaluated across these use case specific settings, measuring how well the voice maintains coherence, responsiveness, and believability throughout an interaction, in the given context of the conversation not just within a single utterance.
Voices should be designed and judged in context: for whether they fit the persona they are meant to inhabit, carry the right social signal, and feel believable in the moment they were built for.
Pricing
Lightning V3.1 is available on a pay-as-you-go model, with no upfront commitments, seat licenses, or minimum usage requirements.
Teams can scale from early prototypes to high-volume deployments across both voice agents and content generation- with usage-based pricing and non-expiring credits.
About Smallest.ai
Smallest.ai is a research-first Voice AI company building proprietary speech models and production-grade voice agents for regulated enterprises.
The company develops state of the art speech-to-text, text-to-speech, and real-time voice systems, enabling end-to-end automation of high-volume conversations across support, collections, onboarding, and servicing- without relying on stitched third-party APIs.
Designed for financial services and other regulated industries, Smallest.ai is SOC 2, GDPR, HIPAA, and PCI compliant, supports on-prem and private cloud deployments, and operates reliably in multilingual environments.
Its platform is used in production by enterprises across banking, insurance, BPO and telecommunications in the US and India.
