I'm looking for a monospace font which has a lot of the unicode glyphs. In particular I'm interested in the speaker symbols, code points 1F507 to 1F50A.
I'm not sure if the speaker would be included, but have you tried GNU Unifont? It is monospaced, it comes in
TTF and it covers glyphs for every printable code point in the Unicode 6.3 Basic Multilingual Plane (BMP). I do think, however, that it's a bitmap font.
You can see the insanely huge list of covered glyphs here.
Monospace, on the other hand, is based on Georgia and covers 2,862 glyphs. Apart from the languages, it includes:
General Punctuation, Superscripts and Subscripts, Currency Symbols, Combining Diacritical Marks for Symbols, Letterlike Symbols, Number Forms, Arrows, Mathematical Operators, Miscellaneous Technical, Control Pictures, Enclosed Alphanumerics, Box Drawing, Block Elements, Geometric Shapes, Miscellaneous Symbols, Alphabetic Presentation Forms, Halfwidth and Fullwidth Forms.
You can use FileInfo to check which fonts support character U+1F507 or other characters. Maybe you will find the font you're looking for.
I found this one which looks great and has many glyphs though the ones you're interested in are not included : Everson Mono on FileFormat or the original web page. I have counted 8835 glyphs but FileFormat mentions 9756 of them.
Please note that this is a shareware:
Everson Mono is shareware. If you use it, support its development by buying a licence to do so. The shareware fee for using one or more than one (that is, any or all) of these Unicode-supporting coded font programs is €25.00. The licence gives you the right to use these fonts on three CPUs and three CPUs only. (That’s two at the office and one at home, so please don’t complain.) Shareware is not freeware. You may not use Everson Mono for free.