Hi

Firstly: what have you set the HD500's output to?

Secondly: are you using FULL or PRE amp models?

I ask because obviously those things are key to how your HD500 will sound.

I have had an HD500 since June and have found that it sounds great and very accurate through pretty much anything I put it through IF I choose the correct options.   Sure i can make it sound 'boomy' if I make incorrect choices for what I'm putting it through.

For instance if I'm going direct to PA, I choose the Studio/Direct output option in the HD500 and I use FULL amp models.   If on the other hand, I'm plugging in to the Power Amp Input on my two Spider Valve amps, I would choose Combo Power Amp In and I would use the PRE amp models.

If I'm going in say via my Marshall JCM2000 TSL100's front input I'd set the Marshall to the Clean channel and everything else to mid-way (12 o'clock) to get as 'flat' a frequency response as possible, and because I'm going through the front input and out through a Marshall 4x12 loaded with Celestion G12T75 speakers, I'd probably probably turn cab modelling off in my POD HD500 presets and I'd use PRE amp models or possibly no amp models at all depending on what I wanted (realistically, I personally would not be going in via the front inputs of a Marshall  - I'd use the FX Return, but that's just the way I'd do it).   I'd set the HD500 output to Stack Front.

Using say a Marshall JCM800 amp (pre or full) model into a Marshall amp which is attached to a genuine Marshall 4x12 with Celestion G12T75s in it and then overlaying a modelled cab loaded with 'virtual' G12T75s is going to sound wrong because you're overlaying a model onto the real thing and therefore exaggerating the effect - which I would find would lead to boominess.

Now - it's interesting to read your comments about the 'unrealistic' sound of the cab modelling.   I find exactly the opposite IF you handle all the output modes and what you're inputting to correctly.  I have a Marshall 4x12 loaded with G12T75 speakers like the model in the HD500 and I have other speaker cabs too.  In the real world using my Marshall TSL100 or JVM205H heads, and with the settings left the same for testing, the Marshall 4x12 DOES sound somewhat quieter than my other cabs, and this is actually mirrored correctly in the HD500.  My other cabs have V30's, G12K100, Eminence and EV speakers in them.

As I said, I find the amp and cab models in the HD500 extremely accurate, but your mileage may vary depending on your expectations - which from my own personal experience regarding my own expectations is not necessarily a reflection of reality.  It's easy to sometimes forget exactly what the real thing actually sounds like in isloation, and that being the case when I hear a model of an amp in isloation I can be fooled into thinking that it doesn't sound quite right in that it might sound a bit too 'boomy' or 'toppy' and it's only when I get to a situation where I actually have the real thing to hand that I actually am forced into modifying my perception of what the model should sound like because there it is right in front of me - real amp pitted against virtual amp, and you know what?  99 times out of 100 my memory is slightly out of whack and the model is a lot closer to the real thing than I think.

The models in the HD500 are in my opinion very realistic and very close indeed to what has been modelled.  In a blind A/B comparison I think most people would be very hard pressed to tell the difference between the real thing and the model - which isn't saying quite the same as the difference between your real amp and the model necessarily, but between the actual amp modelled and the model of that amp.   Remember that with ALL amps any two examples will almost certainly sound a little different because of various factors such as speaker wear and tear, minor manufacturing modificaations, after makerket modifications, component tolerances, component wear and tear and maybe the exact values/tolerances of capacitors or gauge of copper wire used in the circuit (I don't think amp manufacturers were that fussy over stuff like that - they used what was available to keep production lines running).  Line 6 have a range of real amps in their labs that they have sought out and purchased because they believe those amps to be both authentic and because they sound great.  It may be that some of the amps that have been modelled, that minor after market modifications have been made, but that those modifications are considered an improvement - unfortunately or fortunately whichever way you look at it, that's the nature of vintage amplifiers - they may have been repaired or modified over the years.  In all honesty, the lengths these guys at Line 6 go to to get the real authentic sound of whatever they are modelling - even down to the hum you get with a Class A amp, is second to none.

Nick

Bomminess? Hmm? I am using the HD500 with a JSX and two 4x12 400w cabs, and I haven't the slightest complaint about boominess. In fact with some of the pre-amps I have had to add a little more bass from time to time to round the sound out a little more, mainly at high volumes. But hey this is all subjective anyway.