Damping factor

Hi folks,

Bass response question:

Does the damping factor (control?) of an amp have any effect on that of a dedicated subwoofer amp connected via variable line out? 

Or am I hearing something different?

My office system has a Hegel H 190 and a pair of Magnepan LRSs. The variable line out on the Hegel is connected to a dedicated subwoofer amp which powers 4 subwoofers.

I got back a Michael Yee Audio PA-1 SS 100wpc amp from Michael Yee sent in for repairs and some mods to the high end frequency response.

Over the holidays, I swapped out the Hegel and hooked up the PA-1 using a Bryston BP26 preamp. Variable line outs to the subwoofer amp. Same source (basic streaming from laptop)

After listening for just a few minutes, the first thing I heard was a noticeable difference in the bass response. 

At anything above low level listening, it seemed fuller and more enveloping. But not as tight (fast?). 

At anything above moderate levels, I had to get up and slightly reduce gain on the subwoofer amp.

Swapped the Hegel back in, listened for a few days then switched back to the Bryston/PA-1. 

Is this because the Hegel and PA-1 have very different damping factors that affect the subwoofer amp?

I tend to enjoy the difference depending on what's playing. 

Can't tell if there is an overall preference yet.

Just curious about what is behind this difference.


Thanks everyone!




>> Does the damping factor (control?) of an amp have any effect on that of a dedicated subwoofer amp connected via variable line out? <<

The damping factor is related to only two things: the output impedance of the final power stage and the impedance of the speaker, usually assumed 8 ohms for calculations. So NO, the damping factor of your power amplifier is not relevant when you are driving powered subs from a line output.

The only damping factor involved is that of the subwoofer amp. 

If you have a preamp feeding multiple amps you may be having an issue with impedance matching.  With solid state this isn't usually an issue.  Amps tend to have impedances in the 30-50kOhm range, and solid state preamps can usually handle 2-3 amps.. However if you are dealing with a tube preamp it may have issues.

The damping factor is basically the ability of the amplifier to control the driver, tightness. The higher the damping factor the faster the amplifier will be able the return the cone or diaphragm to the center or neutral position. An important specification for low frequency, woofer/subwoofer control, but can also affect low midrange drivers.

You are using two different preamps (the Bryston and the preamp section of the Hegel), and they have different sound signatures. Do this to isolate and hear the difference between the preamps:

  1. Connect speakers to the PA-1 amp, and don't use the subwoofers
  2. Connect Bryston variable line-out to the PA-1 and listen
  3. Connect Hegel variable line-out to the PA-1 and listen

I would expect you to hear a difference, and it is caused by the Bryston and Hegel preamps having different sound signature. It follows that Bryston and Hegel should also sound different when connecting to the subwoofer amp,