[pjpoes]

I'm finding that while bass management has progressed drasticly over the last 10 years, that even the best built in bass management solutions in pre/pro's and recievers isn't so great. I'm wondering what you all think, and what you have done to improve things.


Here are some area's where I take issue:

-My system's main speakers, while towers, are not big enough to be used full range, and so my subwoofers must take on the extra duty of system bass as well as LFE. With some material it seems that bass is appropriatly steered to the subwoofers, and all is good. With other material, it seems that there is no impact or bass to speak of. I have read that material is sometimes recorded with FR limited channels, and I wonder if its a poor interaction between the onboard bass management and the way the soundtrack was recorded? Any thoughts on that?


-While I know everyone loves their steep slopes, but bigger is not always better. It seems that the large majority of units have fixed 2nd order or 4th order slopes. I have a very hard time integrating my subwoofer smoothly with the main speakers using the built in setup features for my Boston Acoustics AVP-1. However, I've never had better luck with any other unit either. I recently played around with a borrowed Meridian unit, and found I had no better luck. However, with an external Ashley crossover, I can get things integrated for 2 channel just fine. I think the problem here is crossover symmetry. Symmetry is often not a good thing, and even when I'm designing speaker crossover networks, I rarely use the identical point for both the tweeter and midbass, or midrange and woofer. Thats because symmetrical crossover points can create either a hump or trough at the xo point. This is exactly the problem I have with my AVP, meaning I usually have a large excess of energy around 60-80hz.


-I'm wondering if the reason why a lot of people prefer full range front speakers is because of the problems with steering the bass to the sub. You would think this would be a basic and easy process, the bare minimum for a prepros bass management, but its an issue I think it struggles with. Again, I get such inconsistent results that I can't even track down the problem. If I measure using my ATB PC Pro or Speaker Workshop rig, I can get a reasonably flat response. I can take close measurements and see that each speaker is being fed what it should be fed (roughly). Then I listen to a cd and find, clearly something is wrong. Bass levels are clearly elevated, clearly missing, whatever. I put in a movie and durring an explosion seen where you would expect room shaking effects, nothing.


Actually on a tangent here, I find explosions, which should contain huge amounts of energy by there nature, seem to have the least amount of energy for a big sound effect, and I can't figure out why. I haven't taken the time to look at the spectrum of a movie explosion, but rarely do they shake the room the way I would expect. The shockwave created by an explosion should have considerably sub-sonic energy. I know my subwoofer can produce in excess of 100db's below 20hz, and measures practically flat down to 15hz. I know that some effects shake like they should, sound like they should, but explosions in every movie from the Star Wars series to war movies like saving private ryan just don't have the oomph I would expect. If anyone has further thoughts on the reason why I might feel this way, I'm all ears. I'm not sure if others feel that explosions don't give them what they expected, and someone maybe has looked at the energy spectrum of an explosion effect?

 

[JOHNnDENVER]

You know... You seem so knowledgable, I hate to even suggest the obvious here.


But, the effect your describing can often be traced to room issues / sub placement.


I mean, it seems you have some serious nulls going on maybe.



As stated, you seem very knowledgable, most likely exceeding my own.

 

[MichaelJHuman]

You seem to know way more than me on the subject. But I did wonder about your comments on explosions. I have heard explosions in movies that have varying levels of low frequencies. Some you feel more than anothers, in other words.


I would think that's a matter of how the explosions were created, mixed etc and not bass management at work.


Are you doing your analysis all by ear? Or do you have access to an audio analyzer? Do you think John's point has any merit? I was shocked by the degree to which low frequency response was affected by the room.


Have you ever tried out bass traps or other methods to try to tame the room response?

 

[pjpoes]

I suppose more information on my setup would be a good idea. I fall into the category of DIYer for sure, and I made my front speakers. I have a pair of JmLabs Electra 905's and a matching Electra center for comparison. These DIY efforts are using Focal drivers as well, just higher end ones. For designing, I have purchased or downloaded a multitude of measurement equipment. My main and most accurate setup is the ATB PC Pro with a flat measurement microphone and appropriate correction file. I have measured my system in various ways, I'm still learning the best ways to measure speakers, but at a minimum, I can get accurate in room measurements of the system. While there are room modes, nothing serious. I also have bass traps, not enough, but I do have some.


As for sub woofer placement, well I haven't played around with it too much. It's just right of center in the front of the room at the moment. It was in a corner, but I felt like it was exciting room modes more there, however at the time that I had it there, I had no measurement setup. It weighs in excess of 250 lbs, so moving it is no easy task. I have second subwoofer awaiting an amplifer, however once finished, I intend to place them in the back of the room to try and help with bass room mode issues.


However, as I said in my first post, I can get the response well integrated and have things meld well if I use a separate pro audio crossover. This is a problem that seems to only exist with a pre/pro in the signal path. I thought for a bit that maybe something was wrong with my Boston ACoustics unit, so I borrowed a Meridian, I think G35 or something like that. The friend who owned it helped me set it up, and we found the exact same issue. He has full range fronts, so he surmises that regardless of brand and type, maybe using bass management in this way may create problems. However, I think that makes no sense, its just acting as a crossover for the main speakers, the only thing complicating this is that it must also direct LFE signals.

 

[JOHNnDENVER]

The type of bass management your looking for here just doesn't exist in an avr or pre/pro that I know of.


I'm not sure what anybody here can offer except sympathy at this point.

For most people, a simple cross at 80hz is pretty good. Add a little EQ to smooth out the sub and your really starting to excel performance wise.


I run my cross at 60 hz, the curve while not perfect (especialy right around the xover point) seems OK enough in real world listening. I use my subs for movies and music. I have lower end subs (Dayton cheapie 15" cabs, low end drivers), old JBL s38's for L/C/R....


I'd post up your curve in the DIY speaker / sub section and solicit advice there. Some of those guys are amazing in their knowledge.


Seems like you have your two channel nailed right? So this is really only for multi-channel sources?

 

[pjpoes]

No no, my 2 channel isn't ok. The problem is that I can't really easily integrate the crossover into a multichannel setup.


I've thought about changing to another setup all together. In fact, I very well may if I get a check I'm hoping for. I recently had a lot of gear damaged in a lightening storm, including my normal (non-diy) main speakers. If they let me buy replacement main speakers of choice, I may use the money to DIY something with full range sound. One idea I have been toying with is a multi-way design that includes GR Research servo subs in the towers, with other well implemented drivers for the rest.

 

[chatanika]

What is the -3db point of your mains? Might try lowering crossover some on sub to avoid 60-80hz overlap hump. Might have to heave that beast closer to the corner again and play with crossovers some more. Bass is finniky and I bump it up or down on almost all disc changes & even sometimes between songs on the same cd. Recording venues change, different people get involved, equipment, mics, eq, etc all can affect the bass so I keep the remote handy and adjust sub volume as needed. Don't know if this relates to your situation but theres my .02 worth.