Resemble AI Voice Cloning API vs Ultravox Voice Cloning

Resemble AI Voice Cloning API

Rapid clones from 10 seconds of audio, ready in under a minute. Cloning API only on Business ($1,000 a month) and Enterprise.

Ultravox Voice Cloning

One multipart request with a 30 to 60 second sample. No consent or speaker verification, only a warranty in the terms.

Resemble AI Voice Cloning API

1. Create the voice, upload recordings or pass dataset_url, then call /build. Nothing trains until you do
2. Set callback_uri rather than polling for status to reach finished
3. Expect a rapid clone. Since 2026-06-30 API-created voices default to rapid, and create-voice has no field to pick another type
4. Upgrade any voice on a pre-Ultra model before synthesis, since those voices can no longer generate audio
5. Check success in every response body, log the request ID, and stay under 40 requests a second per token with your own backoff

Ultravox Voice Cloning

1. Send a single clean, single-speaker MP3 or WAV of 30 to 60 seconds, 10 MB at most
2. Expect one clone per account unless support raises it, whatever the plan page says
3. Test the voice in the Playground before putting it on a live agent
4. Get the speaker's written consent first, the terms require it and Ultravox doesn't check