View Full Version : Dynamic Range Expanders

louped garouv
11-13-2006, 02:46 PM
anyone have experience with them?

DBX, RG Dynamics seem to be the "biggies" in the old school/vintage segments....

thoughts, experiences, bashing.....

all welcome here :D

11-13-2006, 03:02 PM
...friend had a 3-band dbx unit years ago (3BX?), that could subjectively improve
some recordings. I recall it was easy to over-do it, but I'm sure there are even
recent recordings that could benefit from a mild dynamic range expansion.
I just never got into it.

I personally wouldn't bother with a lesser (fewer bands) unit if I wanted one to play with.


11-13-2006, 05:58 PM
I used to have an RG. I think Dolby was the only other thing going at the time and you needed encoded material and you had to calibrate the unit for it to be acurate. I don't have one now but if I had a system somewhat dialed in so there wasn't a bunch of other stuff I needed, it was pretty trick. It actually worked as a noise reducer much like the dolby. You set it up so that every increase in amplitude on the input made a larger increase on the output so you could set it up so that normal LP background noise was inaudible but the material sounded good. I seem to remember that you set a threshold and a rate of "compansion" (I don't remember if that was their term or someone elses) and a limit. If I'm not mistaken, below the threshold you could compress. How good and how real it sounded depended on the recording and how much it had been compressed. Also how you were listening. If you wanted something in the background, you might want it compressed, but if it had been seriously compressed and you wanted just to listen you might be able to make it sound live. If it was too compressed of course you were screwed. What it could do is take existing dynamic range and magnify it. Of course with CD's you don't have background scratches (I just don't get the cd vs lp thing. sure cd's have absolute limits and vinyl it's all theoretical there is no brick wall as far as limits so maybe some LP's sound better than some CD's but the average mid priced cd played on the average playback equipment against the average mid priced LP played on averag mid priced playback equipment Where's the contest?) Anyway a lot of times if you have top notch equipment the thing that will give it away as not live is the lack of dynamic range. Most JBL systems are capable of it but the material isn't there. You can turn it up good and loud but then the quiet parts aren't as quiet as they are supposed to be. That is what a compander or dynamic range expander is supposed to do. I loved my RG but it's been more than twenty years, and a plus is that you do not need encoded material. A minus is that if you are looking for realism you won't find one setting that is right for every recording, although you may find one setting that is better than without it that you can live with. It's not for Quiet listening because that is one of the things compression is for. That is the only unit I have eperience with. If I remember right RG made two units back than and I have had both but it's too long ago to remember the differences. Someone else must have had one also because I think compander was someone elses name. Hope there was something in all these words you could use.

11-13-2006, 06:03 PM

Just reread your post. How are the bands broken up? Frequency?

scott fitlin
11-13-2006, 06:29 PM
Actually, in the respect to how many freq bands and expabnder has, LESS IS MORE! The RG Dynamics has a more together sound, IMHO, (and I have both DBX and RG), because it is a 1 band unit.

DBX divides the signal into 3 seperate bands, perform expansion then reassembles the signal back into a full range output, hard to put the signal back together with exactly the same phase relationship it originally went into the unit with. Not saying DBX doesnt sound good, but this was always the argument in favor of the RG years ago.

Expanders will add punch and dynamic scale to playback of your recordings, and CD,s benefit from this just like records used to!

11-13-2006, 06:46 PM
If you know the compression parameters of a given recording, and set the expander accordingly, (and your system has enough dynamic headroom), they're the cat's meow. Otherwise, if you're guessing, it's just a sound effect.(I'm spending my 2 cents awfully fast tonite....)

11-13-2006, 07:19 PM
I've owned a 3bx-ds for 18 years. I use it in conjunction with a SNR-1 single ended noise gate. The 3bx-ds also has a compressor on the same knob, a nice touch. THe three bands can be tweaked at the rear to favor the high and low crossover points.

I use it at around 20% with an even amount of gain and atenuation. In short, I have an equal amount of above threshold and below threshold action. The 3bx-ds has an impact restoration function, a transient amplifier that lifts percussion up. To round it off there is a "ambiance" control that mixes L-r and L+R information in the midrange to remove air or add it to recordings. Works to remove noise as well.

They are very versatile machines and I would not be without it. THey fetch a good coin on eBay regularly. I also have the 120-ds subharmonic bass synthesizer. Now that is a great little toy!:applaud:

scott fitlin
11-13-2006, 07:24 PM
Yeah, I got the 120 Sub Harmonic Syth, and the Original Model 500 Sub Harmonic Synth.

Was never my personal cup of tea. Always found the bass much more natural without than with!

11-13-2006, 09:22 PM
Those 120s just happen to add EXACTLY one full octave lower extension to a Wurlitzer electric piano.......quite handy, indeed.

jim campbell
11-13-2006, 09:53 PM
i used the 3bx with good results for playback only (mostly vinyl).albums seemed quieter surface noise wise but with a more dynamic sound.the purists and single ended triode crowd tends to shun any added gear but try it and make up your own mind

11-13-2006, 09:57 PM
It livens up FM a lot too. I have the owners manual, it offers great information on using it, anyone needs a copy let me know

11-14-2006, 07:39 AM
Actually, in the respect to how many freq bands and expabnder has, LESS IS MORE! The RG Dynamics has a more together sound, IMHO, (and I have both DBX and RG), because it is a 1 band unit.

Hey Scott.

No arguments here :D. I haven't heard an RG unit.

I did hear a single band dbx unit of similar vintage to the 3BX (again... all -many-
years ago) and I recall that one could subjectively improve the playback a bit more
without obvious artifacts with the multiband unit from dbx vs. the single band dbx unit.


scott fitlin
11-14-2006, 08:05 AM
Hey Scott.

No arguments here :D. I haven't heard an RG unit.

I did hear a single band dbx unit of similar vintage to the 3BX (again... all -many-
years ago) and I recall that one could subjectively improve the playback a bit more
without obvious artifacts with the multiband unit from dbx vs. the single band dbx unit.

-grumpyYes, that is what they were talking about back then. And the old 3BX ( 503 ) could also cause a breathing and pumping type of sound, the RG did not do this!

Regardless of whatever adjustments the later 3BX, 4BX, and 5BX had, you just couldnt reassemble the output signal with the same exact phase relationship the input signal had.

But, the DBX units can, used correctly, sound good, and add life to recordings.

The RG had a more solid sound, but, overused could get harsh sounding too.

I have them, the DBX and RG,s and I much prefer my tubed processor these days! Adds the dynamics, but, it is natural and acoustic sounding.

As always, its up to the individual to decide what they like for themselves.

11-14-2006, 10:10 AM
I have and used to use a dBx 119 Compander (compressor/expander) and in the days of vinyl it was great for reducing background hiss, though there was always a certain amount of "pumping." For CDs it adds to the dynamic range and can make old recordings more dramatic, if used minimistically.

Alas, when I went to my current Yamaha Z9, similar operations are performed in the digital domain for all channels and with efficient speakers, I find the added noise audible and objectionable.

Besides, I'd need a couple more units to apply it to all channels and the front and rear surrounds don't have effects loops built into the receiver like the L,C,R.:blink:

I do continue to use the dBX Subharmonic synthesizer that pushes the Crown PSA-2XH running in mono into the W15GTI sub (and sometimes W15GTI and 2235). This gives the bottom a nice boost and the synthesizer can add some real depth to movies.

WORD OF WARNING! Too much subharmonic synthesization coupled with too many watts can bottom out a 2235 with a nice audible "CRUNCH!" The W15GTI has not exhibited this trait.

scott fitlin
11-14-2006, 10:54 AM
I got an old Model 500, the original boom box, sub harmonic synthesizer, if you overdo it, the bass gets rubbery sounding.

They were known as speakerblowers back in the day!


Merkin Berfel
11-14-2006, 06:50 PM
The RG16 worked well, the RG20 was even better but harder to find. As it was explained to me the RG units were dual mono with no interaction between channels where on the DBX the expansion was on both channels simultaneously, which created some audible artifacts on hard left or right material.
The expander should be set up for gain reduction only. It should not increase the volume of loud passages, just decrease the gain on softer passages for a wider perceived dynamic range. You can tune it in by ear by switching the unit in and out of the signal path on louder material and listening for volume changes. I would usually set the expansion just short of maximum as the dynamics sounded more natural.

An expander along with a transient noise eliminator is a great combination for vinyl. These things are also great on compressed to death sources like FM and TV, although a less agressive expansion setting is better for TV as the softer dialogue tends to get lost.

11-16-2006, 11:01 AM
I also favor pressing down with only a limited amount of gain. DBX had a system they called "overeasy" which made the compressor a lot more listenable.

louped garouv
12-04-2006, 03:39 PM
I am liking the RG PRO-20 unit pretty well so far....

makes the music "beefier" and "quieter" if that makes sense...

I have only listened for about 3/4 songs so far though...
much listening needed in the next week or so...

If anyone needs a scan of the manual for the RG units, let me know...

12-14-2006, 07:04 AM
I got recommended a dbx 3bx, from my usual source and have loaned one for quite a while now.

Most has been said before what they do - as I describe it they just give the music back what has been compressed before, on CD or in recordings - they don't add anything that wasn't already there in the studio.

I believe only purists will call them just effect machines but I've heard a long and well-founded explanation from an studio tech why most pro's wouldn't want to live without them. But it has to be an analog unit for me - those dynamic range expanders deliver a kind of improvement for home use as well that one gets used to in very short time. Beside all other sources, particularly mp3 collections from devices like computers or ipods as source in a hifi rig benefit a lot from them.