The source of this text is the (former) forum of GPS-Expert.nl

Upgrading the TTS voices of your nüvi - zūmo GPS

Making the Garmin voices louder for zūmo and nüvi series

By using a Hex Editor we can modify the zūmo's Text To Speech (TTS) navigation voices to make them louder, this is handy if you feel the zūmo's navigation prompts are too quiet particularly when on the bike and wearing earplugs. This does not work on non-TTS voice files.

Increasing the volume from the original 75 setting to about 85 or 87 is a worthy increase in volume without any distortion creeping in (especially when using the car mount).

Download the following PDF file containing full instructions: HowTo - Upgrade volume of zūmo TTS voices.pdf

Site of Tiny Hexer is closed. Use Free Hexedit (Windows) or Hex Fiend (Mac OSX).

Already changed voices (for all zūmo/nüvi models which support TTS voices with filesizes from 2-4 MB):

Like the zūmo 220

Nederlands-Claire - Volume 95 version 1.11 & 1.12

Already changed voices (for all zūmo/nüvi models which support TTS voices with filesizes from 12-14 MB:

Like the zūmo 550, zūmo 660, zūmo 350 and Montana

Older versions:

Unpack them from zip and place them in this folder: X:\garmin\voice\ or X:\voice\ (depending on the model GPS)

Volume of non-TTS voices:

I also have experimented on the normal voices. The British_English, Netherlands, Flemish, French, German and Spanish voices I already have them converted to have extra volume (normalising and the a 400% amplifying). These voices will be visible in your zūmo as version 2.21 (System/About - audio version)

How to Undo the voice changes:

Delete the English_British_Emily.vpm* file from GARMIN:\garmin\voice\ directory
Disconnect your zūmo from computer and let it startup completly
Reconnect your zūmo to your Computer
Start Garmin Webupdater and let it check the software
Check additional software in Webupdater
Select the needed voice file (English British Emily)
Press ok and the original Voice file is installed to your zūmo again.

* Or, just replace your modded .vpm file with the original which you should save a copy of before you start!