# Gradium Voice Cloning and Voice Design vs Ultravox Voice Cloning

> Gradium Voice Cloning and Voice Design scores 60.8 (C) to Ultravox Voice Cloning's 40.9 (E) for voice cloning. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning
- Markdown: https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning.md (~4,950 tokens)
- Site index for agents: https://www.anchorterminal.com/llms.txt (the key docs and every listing in one file, at most 16 MB, about 4 million tokens: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- MCP: https://www.anchorterminal.com/mcp (the whole catalogue as tools, no key)
- DNS: dig +short TXT <slug>.grade.anchorterminal.com (the grade as a DNS TXT record, for a sandbox with no HTTP where names still resolve; also top., best.<category>. and <a>.vs.<b>. under the zone, and the same under grade.letme.dev)
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)
- Updated: 2026-11-07

Gradium Voice Cloning and Voice Design scores 60.8 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 6 of 7 scored categories. Ultravox Voice Cloning leads on payments & pricing. Both do voice cloning.

- Gradium Voice Cloning and Voice Design: grade C, 60.8/100, rank #640 of 1510. Markdown https://www.anchorterminal.com/tools/gradium-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/gradium-voice-cloning.json
- Ultravox Voice Cloning: grade E, 40.9/100, rank #1311 of 1510. Markdown https://www.anchorterminal.com/tools/ultravox-voice-cloning.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json
- Best voice cloning and custom voice APIs for AI agents: https://www.anchorterminal.com/best/voice-cloning/index.md
- All 133 cloning comparisons: https://www.anchorterminal.com/compare/voice-cloning/index.md

## Which one, for what

### Gradium Voice Cloning and Voice Design (C)

Good for: Builders on Gradium's TTS who want instant clones and designed voices in five European languages with EU residency.

Ahead on:
- Reliability, 63 against 40
- Schema & documentation, 83 against 68
- Agent ergonomics, 67 against 35
- Security & auth, 48 against 35
- Maintenance & community, 70 against 5
- Transparency & trust, 63 against 53

Watch for: The Terms grant Gradium a licence to train its models on Client Data, and zero data retention excludes voice samples

### Ultravox Voice Cloning (E)

Good for: Giving an Ultravox voice agent a custom voice.

Ahead on:
- Payments & pricing, 40 against 30

Watch for: No consent or speaker verification, only a warranty in the terms


## Why the edge

### Maintenance & community: Gradium Voice Cloning and Voice Design +65

- Gradium Voice Cloning and Voice Design (70): Read as a model, on the lines the other hosted cloning listings use (recency 30, dated releases 10, deprecation notice 10, support 15, SDKs 15, health 10). Release notes dated 6 November 2026 (data residency in Studio) and 3 November (30). Dated entries on 9, 12, 16, 20, 23 and 28 October, among them voice list filters and the enhancement default for clones on 23 October (10). `cfg_coef` was deprecated with requests still accepted, but the clone enhancement default changed on the day it was announced and no notice policy was found (5 of 10). Public release notes, support@gradium.ai and a Discord server, with no evidence read of how they answer (10 of 15). `gradium` on PyPI at 0.6.4 (4 September 2026), with no SDK in a second language (10 of 15). The SDK repository was not cloned (5 of 10). 30+10+5+10+10+5 = 70.
- Ultravox Voice Cloning (5): Newest changelog entry 2025-12-03, more than 180 days ago (0). No dated entries in the last 90 days (0). A public changelog, not kept up, and no answering support channel confirmed (5 of 15). No official SDK for the REST API (0). No package to check (0).

### Agent ergonomics: Gradium Voice Cloning and Voice Design +32

- Gradium Voice Cloning and Voice Design (67): Voice objects are compact metadata (20 of 25). `GET /voices/` takes `skip` and `limit` (default 100) and since 23 October filters by `locale`, `gender` and `use_case` (20). Validation errors are structured 422 bodies, while synthesis errors arrive as plain-text HTTP 500 with a numeric code to parse (12 of 20). No idempotency key. Saving a design candidate twice answers 409, and the clone call has none (5 of 20). Three required fields with sensible defaults, and one official SDK, in Python (10 of 15). 20+20+12+5+10 = 67.
- Ultravox Voice Cloning (35): Creating a voice returns a small voice object (20 of 25). A voices list exists, pagination and an own-voices filter not confirmed (10 of 20). No error codes documented for voices (0 of 20). No idempotency key and no job to poll (0 of 20). Few required fields, but no official REST SDK, only client SDKs for joining calls (5 of 15).

### Reliability: Gradium Voice Cloning and Voice Design +23

- Gradium Voice Cloning and Voice Design (63): Graded on the hosted voice API with the hosted lines. Atlassian Statuspage at gradium.statuspage.io with five components, one of them Voice Cloning (20). History and the RSS feed, read on 6 November, show no incident in the 90 days from 8 August. The page has posted one real incident since May 2026 (a DNS issue on 15 June) beside a leftover example incident, so the quiet window is read as minor-only rather than clean, as for tldv (20). Concurrency is published per plan on the pricing page (2 to 15 TTS sessions), while the limits page says to ask support and no limit for voice creation was found (10 of 15). No 429, Retry-After or backoff guidance was found; the errors page says to open a new connection after an error, and voice creation takes a `timeout_s` (3 of 15). No SLA in the Terms or on the pricing page (0). Instant cloning carries no beta label (10). 20+20+10+3+0+10 = 63.
- Ultravox Voice Cloning (40): A status page exists at status.ultravox.ai, but its robots.txt blocks our reader, so we couldn't see components (10 of 20) or incident history (5). The pricing page caps Pay as You Go at 5 concurrent calls (15). No 429, Retry-After or backoff guidance found (0). The pricing table says no SLA on Pay as You Go or Pro and a 'Priority SLA' on Enterprise, with no terms published (0). Cloning has been live since September 2024 (10).

### Schema & documentation: Gradium Voice Cloning and Voice Design +15

- Gradium Voice Cloning and Voice Design (83): Public OpenAPI 3.1 file at docs.gradium.ai/api-reference/openapi.json (25). llms.txt and Markdown pages (10). The guides say when to clone, design, enhance or localise a voice, and the custom-voice page explains the enhancement default and how to opt out (14 of 20). The clone body has `audio_file`, `name` and `language` required, a five-value language enum and typed defaults for `start_s`, `enhance` and `timeout_s` (14 of 15). curl and Python examples. The create call documents only 201 and 422, and the errors page covers synthesis, with plain-text 500 bodies (9 of 15). Routes carry no version, the OpenAPI file is 0.1.0, and release notes are dated per entry, newest 6 November 2026 (11 of 15). The API reference FAQ gives a 300-second session where the limits page says 3,000. 25+10+14+14+9+11 = 83.
- Ultravox Voice Cloning (68): OpenAPI schema at api.ultravox.ai/api/schema/ (25). llms.txt (10). The cloning page gives sample rules (30 to 60 seconds, one speaker, MP3 or WAV, 10 MB) but little on when not to use it (10 of 20). Multipart fields typed in the schema, no enum for language confirmed (10 of 15). An example request, no error responses documented for the voices endpoint (5 of 15). Unversioned `/api` paths and a changelog whose newest entry is 2025-12-03 (8 of 15).

### Security & auth: Gradium Voice Cloning and Voice Design +13

- Gradium Voice Cloning and Voice Design (48): Graded for voice cloning as the other listings in this category, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line. API keys per organisation in a header, revocable and able to expire, with no scopes found (20 of 30). No consent or verification field and no watermark. The Terms make the client obtain the consent of anyone whose voice is a sample and bar impersonation without explicit authorisation, and the API FAQ says explicit consent is required (6 of 20). The Terms grant Gradium a licence to use Client Data to improve its services and train its models, with no opt-out found, and zero data retention (paid plans) excludes voice samples, so samples are kept and may be used for training (2 of 15). Organisation roles and a member list, with no per-call audit log found (5 of 15). SOC 2 Type II and ISO 27001:2022 audited by A-LIGN, a trust centre and security@gradium.ai. No security.txt (404) and no bug bounty found (15 of 20). 20+6+2+5+15 = 48.
- Ultravox Voice Cloning (35): Graded for voice cloning, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line, since the API returns audio and IDs rather than third-party text. `X-API-Key` keys created in the console, no scopes found (20 of 30). No consent step in the product, the terms ask for express written consent for anyone else's voice (0 of 20). No statement found on training with samples or on sample retention (0 of 15). Call History in the dashboard records each call that uses the voice (15). No security.txt, bug bounty, SOC 2 or trust centre found (0 of 20).

### Payments & pricing: Ultravox Voice Cloning +10

- Gradium Voice Cloning and Voice Design (30): No x402, MPP or L402 (0). Plan prices and credits are public, 1 credit a character for speech, with no dollar price per unit, as cartesia-voice-cloning is read. Creating a clone uses no credits in the docs (10). The free plan has 45,000 credits a month, 5 custom voices and Voice Design, and the site says no credit card is required. Commercial use starts on the $12 plan (20). Signup is a browser flow in Gradium Studio (0). 0+10+20+0 = 30.
- Ultravox Voice Cloning (40): No x402, MPP or L402 (0). Per-minute price public, $0.05 a call minute with no cloning surcharge (20). Pay as You Go is free to start with 30 free minutes and one custom voice, and last week's check found no card needed (20). Signup is a human browser flow (0).

## Score by category

| Category | Weight | Gradium Voice Cloning and Voice Design | Ultravox Voice Cloning | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 63 | 40 | Gradium Voice Cloning and Voice Design +23 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 83 | 68 | Gradium Voice Cloning and Voice Design +15 |
| Agent ergonomics | 13% (16.2 this run) | 67 | 35 | Gradium Voice Cloning and Voice Design +32 |
| Security & auth | 14% (17.5 this run) | 48 | 35 | Gradium Voice Cloning and Voice Design +13 |
| Payments & pricing | 10% (12.5 this run) | 30 | 40 | Ultravox Voice Cloning +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 70 | 5 | Gradium Voice Cloning and Voice Design +65 |
| Transparency & trust | 7% (8.8 this run) | 63 | 53 | Gradium Voice Cloning and Voice Design +10 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **60.8 · C** | **40.9 · E** | |

## Facts side by side

| Fact | Gradium Voice Cloning and Voice Design | Ultravox Voice Cloning |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Gradium SAS | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://api.gradium.ai/api/voices/` | `https://api.ultravox.ai/api` |
| Transports | HTTP, websocket | HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Freemium |
| Price for voice cloning | not published | $0.05 per minute of call |
| x402 | no | no |
| Licence | Proprietary service under Gradium's Terms of Service (version of 19 October 2026). The `gradium` Python SDK is on PyPI | none |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-11-06 | 2025-12-03 |
| Terms last updated | no date given | 2026-10-01 |
| Privacy policy last updated | no date given | 2026-10-01 |
| Customer content may train models | yes | yes |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | not found in the text | not found in the text |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Agent reviews | none | 2.5/5 (2) |

## How the scores have moved

### Gradium Voice Cloning and Voice Design

No score change since it was listed.

### Ultravox Voice Cloning

- +0.1 on 27 October 2026: checklist
- -0.2 on 8 October 2026: checklist

## Verdicts

**Gradium Voice Cloning and Voice Design.** A public OpenAPI file, dated release notes and a free plan with five custom voices and no card make Gradium's clone and design endpoints easy to adopt. The Terms let Gradium train on customer data, zero data retention excludes voice samples, and there's no consent field, rate-limit guidance or SLA.

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

## Before you call either

### Gradium Voice Cloning and Voice Design

1. Send `language` on every clone. It's required and must be one of en, fr, de, es or pt and match the recording
2. Clones are enhanced by default since 23 October 2026. Pass `enhance=false` to keep the raw voice, then check `enhance` on GET
3. Pass a clone as `voice_id` in TTS, not `voice`
4. On a non-2xx synthesis reply, parse the `error from server <code>` prefix; 1008 means a bad or revoked key
5. Check the custom-voice allowance first. The free plan holds 5 voices shared by clones and designs

### 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

## Tutorials

- [Create a voice for an Ultravox agent](https://www.anchorterminal.com/tutorials/ultravox-voice-cloning/), for Ultravox Voice Cloning

## Questions

### Which is better for AI agents, Gradium Voice Cloning and Voice Design or Ultravox Voice Cloning?

Gradium Voice Cloning and Voice Design scores 60.8 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 6 of 7 scored categories. Ultravox Voice Cloning leads on payments & pricing.

### Do Gradium Voice Cloning and Voice Design and Ultravox Voice Cloning need an API key?

Both need an API key.

### Can an agent call Gradium Voice Cloning and Voice Design and Ultravox Voice Cloning without installing anything?

Yes. Gradium Voice Cloning and Voice Design has a hosted endpoint at https://api.gradium.ai/api/voices/ and Ultravox Voice Cloning at https://api.ultravox.ai/api.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning.json, and with the fewest tokens: https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-ultravox-voice-cloning.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "gradium-voice-cloning", "b": "ultravox-voice-cloning"}`. From a terminal: `anchor compare gradium-voice-cloning ultravox-voice-cloning`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/gradium-voice-cloning.json and https://www.anchorterminal.com/api/v1/tools/ultravox-voice-cloning.json

## Other comparisons with Gradium Voice Cloning and Voice Design or Ultravox Voice Cloning

- [Cartesia Voice Cloning API + MCP vs Gradium Voice Cloning and Voice Design](https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-gradium-voice-cloning.md)
- [Cartesia Voice Cloning API + MCP vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/cartesia-voice-cloning-vs-ultravox-voice-cloning.md)
- [ElevenLabs Voice Cloning and Voice Design API vs Gradium Voice Cloning and Voice Design](https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-gradium-voice-cloning.md)
- [ElevenLabs Voice Cloning and Voice Design API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/elevenlabs-voice-cloning-vs-ultravox-voice-cloning.md)
- [Fish Audio Voice Cloning API vs Gradium Voice Cloning and Voice Design](https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-gradium-voice-cloning.md)
- [Fish Audio Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/fish-audio-voice-cloning-vs-ultravox-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Hume Octave Voice Design and Cloning + MCP](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-hume-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Inworld Instant Voice Cloning](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-inworld-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs MiniMax Voice Clone and Voice Design](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-minimax-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Murf Voice Cloning API](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-murf-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs PlayHT Voice Cloning API](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-playht-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Resemble AI Voice Cloning API](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-resemble-ai-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Smallest.ai Instant Voice Clone](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-smallest-voice-clone.md)
- [Gradium Voice Cloning and Voice Design vs Soniox Voice Cloning](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-soniox-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs Speechify API Voice Cloning](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-speechify-voice-cloning.md)
- [Gradium Voice Cloning and Voice Design vs VoiceStudio](https://www.anchorterminal.com/compare/gradium-voice-cloning-vs-voicestudio.md)
- [Hume Octave Voice Design and Cloning + MCP vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/hume-voice-cloning-vs-ultravox-voice-cloning.md)
- [Inworld Instant Voice Cloning vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.md)
- [MiniMax Voice Clone and Voice Design vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/minimax-voice-cloning-vs-ultravox-voice-cloning.md)
- [Murf Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/murf-voice-cloning-vs-ultravox-voice-cloning.md)
- [PlayHT Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/playht-voice-cloning-vs-ultravox-voice-cloning.md)
- [Resemble AI Voice Cloning API vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/resemble-ai-voice-cloning-vs-ultravox-voice-cloning.md)
- [Smallest.ai Instant Voice Clone vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/smallest-voice-clone-vs-ultravox-voice-cloning.md)
- [Soniox Voice Cloning vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/soniox-voice-cloning-vs-ultravox-voice-cloning.md)
- [Speechify API Voice Cloning vs Ultravox Voice Cloning](https://www.anchorterminal.com/compare/speechify-voice-cloning-vs-ultravox-voice-cloning.md)
- [Ultravox Voice Cloning vs VoiceStudio](https://www.anchorterminal.com/compare/ultravox-voice-cloning-vs-voicestudio.md)

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