When choosing a speech-to-text provider for non-English languages, both AssemblyAI and Speechmatics offer robust solutions, but they come with different strengths and weaknesses. Here’s a deep comparison to help you decide:

AssemblyAI

AssemblyAI has made significant strides in multilingual transcription, positioning itself as a strong contender with its Universal models.

• Pros:
  • High Accuracy in Supported Languages: AssemblyAI’s Universal model demonstrates high accuracy, with benchmarks showing strong performance in languages like Spanish and German. Some tests indicate it performs consistently well across various scenarios, even tying with or outperforming competitors in specific non-English tests (e.g., French).
  • Extensive Language Support: AssemblyAI supports transcription for a wide range of languages (reportedly over 99+ with its Nano model and a significant number with its “Best Tier” models, including languages like Chinese, Hindi, Russian, Turkish, and Vietnamese).
  • Automatic Language Detection: The platform offers automatic language detection, which is crucial for workflows dealing with diverse audio inputs. They have been actively improving the accuracy and expanding language support for this feature.
  • Developer-Focused API: Provides a comprehensive and well-documented API, making it easier for developers to integrate transcription capabilities into their applications. Features like speaker diarization, custom vocabulary, and PII redaction are available.
  • Advanced AI Features: Offers additional audio intelligence features like summarization, sentiment analysis, and topic detection, which can be beneficial even for non-English content.
• Cons:
  • Newer to Extensive Multilingual Support: While rapidly expanding, their primary focus was historically on English, with broader multilingual capabilities being a more recent, though significant, development.
  • Cloud-Dependent: Primarily a cloud-based service, which might be a limitation in environments with poor connectivity or for users requiring on-premise solutions.
  • Cost for High Volume: While offering a pay-as-you-go model and free credits to start, costs can accumulate with very high volumes of transcription, especially when utilizing advanced features.
  • Limited On-Premises Options: Currently, there are no on-premises deployment options available, which could be a concern for organizations with strict data residency or security policies requiring on-site processing.

Speechmatics

Speechmatics emphasizes its “global-first” approach to language support, aiming for high accuracy across numerous languages and their dialects.

• Pros:
  • Extensive and Established Language Coverage: Speechmatics supports over 50 languages, with a strong focus on providing high accuracy across various accents and dialects within those languages (e.g., global English, global Spanish, global French). They highlight their ability to add new languages relatively quickly due to their underlying technology.
  • Strong Non-English Accuracy and Dialect Handling: User reviews and company statements frequently highlight Speechmatics’s strength in transcribing non-English languages and handling diverse dialects effectively.
  • Flexible Deployment Options: Offers both cloud and on-premises deployment options, providing flexibility for businesses with varying data security and infrastructure requirements.
  • Real-time Transcription: Provides robust real-time transcription capabilities across its supported languages. They have focused on optimizing the trade-off between latency and accuracy in real-time scenarios.
  • Integrated Translation Features: Offers translation capabilities for transcribed audio into multiple languages through a single API call, which can be a significant advantage for multilingual workflows.
  • Focus on Inclusivity: Their approach of creating single language packs to cover many dialects aims to simplify workflows and ensure broader voice inclusivity.
• Cons:
  • Pricing Concerns for Some Users: Some user feedback mentions pricing as a potential issue, and costs can be higher compared to some alternatives, especially for enhanced features.
  • API Complexity for Some Features: While offering a powerful API, integrating and managing some advanced features or scaling usage might require more effort for some users.
  • Geographical Limitations for Servers: Some users have noted potential latency or data transmission issues in regions where Speechmatics does not have local server presence (e.g., China).
  • Average Accuracy in Some Benchmarks (for pre-recorded): While generally strong, some third-party comparisons have shown its accuracy for pre-recorded audio as average in specific tests, though it often excels in real-time and dialect-heavy scenarios.

Deep Comparison: AssemblyAI vs. Speechmatics for Non-English Transcription

Feature	AssemblyAI	Speechmatics
Language Coverage	Rapidly expanding, supports 99+ languages with Nano model, good coverage with Universal/”Best Tier” models.	Strong focus on 50+ core languages with extensive dialect support within each (“global” language packs).
Accuracy (Non-English)	High accuracy with Universal model in tested non-English languages (e.g., Spanish, German, French). Improving automatic language detection accuracy.	Generally lauded for high accuracy in non-English languages and diverse dialects. Strong in real-time.
Dialect Handling	Aims for broad accent coverage with its models.	A core strength; “global” language packs are designed to handle many accents and dialects within a single model.
Real-Time Transcription	Offers real-time transcription with low latency.	Robust real-time capabilities with configurable latency/accuracy trade-offs. A key focus area.
Automatic Language Detection	Yes, with ongoing improvements in accuracy and language support.	Yes, supported for batch transcriptions.
Translation	Not an explicitly integrated core feature for transcription; would likely require separate services.	Integrated translation to multiple target languages via API call.
Deployment Options	Primarily cloud-based.	Cloud and on-premises options available.
API & Developer Focus	Strong developer focus with comprehensive API and documentation. Extensive additional AI features.	Powerful API, well-suited for integration. Good customer support reported.
Pricing Model	Pay-as-you-go, volume discounts available. Free tier/credits.	Pay-as-you-go and enterprise plans. Some users note it can be on the higher side.
Ease of Use (Non-Developers)	API-centric, might present a learning curve for non-developers.	API-focused, though some portal access for testing is available.
Key Strengths (Non-English)	High accuracy with newer models, broad language list, advanced audio intelligence features.	Excellent dialect handling, established non-English accuracy, integrated translation, flexible deployment.
Potential Weaknesses (Non-English)	Newer to deep multilingual focus compared to Speechmatics, cloud-only.	Can be pricier, some geographical server limitations.

See Google Sheets

Which to Choose?

• Choose AssemblyAI if:
  • You need the absolute highest accuracy in one of the non-English languages where their Universal model benchmarks exceptionally well.
  • You require a broad range of additional AI-powered audio understanding features beyond basic transcription (summarization, sentiment analysis) for your non-English content.
  • You are comfortable with a cloud-only solution and have developer resources to leverage their API extensively.
  • You are dealing with a very wide array of less common languages where their broader list might offer coverage.
• Choose Speechmatics if:
  • Your primary need is highly accurate transcription of non-English languages with strong support for diverse accents and dialects.
  • Integrated audio translation is a key requirement for your workflow.
  • You require on-premises deployment for data security or regulatory reasons.
  • You prioritize robust real-time transcription performance for non-English languages.
  • You value a provider with a long-standing, dedicated focus on global language support.

Ultimately, the best choice will depend on your specific non-English language requirements, the importance of dialect handling, whether you need real-time transcription or translation, your deployment needs, and your budget. It is highly recommended to test both platforms with your own audio samples in the target non-English languages to assess their performance directly.