Crossover Quandry / Please Help (1 Viewer)

[GregBe]

I have Cambridge Soundworks MC300 speakers for my left, center and right main speakers. These speakers have two 4" drivers and one 1" tweeter. The specs say they play down to 80 Hz. Recognizing that I need to set the crossover higher than 80, I toggled between 100 and 120 on my Onkyo 600 receiver (I set the low pass on the sub all the way up to defeat it). Male voices sounded a little thinner with a setting of 100 and more full with a 120 setting so I went with that. Not able to leave well enough alone, I started playing with DVE and a SPL meter the other day, and I came across the "Bass Management" section. It runs a sweep for each speaker (with the sub) as well as the whole system from 15 Hz up to 150 Hz or so. When I ran the sweep at 100, it appeared to be a big dropoff in SPL between 90-120 (a small portion actually went completely silent. When I ran the sweep with the 120 Hz crossover there was still a big dropoff between 100-120 Hz. This didn't seem right to me. I know that 120Hz is not an ideal crossover, but I figured that it would be far enough above the low end to at least get a full signal throughout the full range.
I thought that it might be something wrong with the Onkyo crossover settings, so I tried hooking the sub to the l/r main speakers, the main speakers out of the sub, set the main speakers to large and set the sub to off. Again not ideal, but I know that with Dolby's mfg requirements, I could set it up this way, and through bass management get all of the information from all of the channels.
What I found was interesting. Even with a low pass setting on the sub of 100 the dropoff went away.
1)Does this make any sense?
2)Could there be a malfunction in the receivers crossover circuitry?
3)Am I even running the right test from DVE to figure this out?
4)If I am getting better readings this way, is it ok to leave my system set up this way. (it is hard to mentally not hook up the sub through the sub out; especially if there is any lack of performance)
Any ideas would be greatly appreciated
Greg

 

[GregBe]

I wonder if this has anything to do with it. I read through some posts on octave slopes, and how if the slopes of the sub and the receiver are varied, it would be very difficult to match the mains with the sub. I read that my sub (CSW P500), has a 48 Oct. Slope. That seems much higher than most that I have seen. If I am bypassing the sub out of the receiver and using bass management and sending everything to the mains and using the low pass crossover on the sub, am I in fact getting a better blend.
I am not really sure what I am talking about, but comments would be great

Greg

 

[Wayne A. Pflughaupt]

What you’re probably seeing is some phase cancellation. This is not uncommon with electronic crossovers. If you’re happier with the way you have it now, then by all means use it that way!

Regards,
Wayne A. Pflughaupt

 

[Ray_C]

I just went through the excact same thing with my speakers and setup (Klipsch RB-25 fronts, Denon AVR2803 used as pre/pro to Marantz MM9000 amp), and at about the same frequencies as you (around 80-100). I'm pretty sure it has something to do with my room acoustics. Before going out and getting an EQ and trying to integrate it with my main speakers, I decided to mess around with my crossover and speaker settings. I originally had all my speakers (all Klipsch Reference 25's) set to 'small' and my crossover at 80Hz, but there was still a hole. Upping the crossover to 100Hz helped a bit, but it felt like I was starting to rob the speakers of what they should be playing, and the bass, although fuller, got boomier and more loose. I found the best setting to be setting all my speakers to 'large' (the MM9000 doesn't even break a sweat with the Klipschs), and the subwoofer output to 'LFE+main', rather than just 'LFE' which would have diverted lower signals away from the mains, with the crossover at 100Hz. This way, the speakers are getting low signals and can add a bit of punch/tightness, while the sub is still filling things out up to 100Hz. Things are much fuller in both 5.1 DVD's and 2-channel music. There's still a bit of a dip in the sweep, but it's not that bad, and definitely not as severe as before.

 

[DavidLW]

I'm not sure if I got this right but I'm assuming that when you set the crossover on the receiver to 100 or 120hz that this sets the low pass to the sub and the high pass to the mains (and center). If this is the case then what's happening is that your sub is not efficient at playing 100hz and above. Which is not unusual as most subs are really meant to play 80hz and below. By playing the main full range you are letting your main (and center) play the 120 to 80hz range and they are much better at playing these frequencies than the sub. You got to remember that the sub is trying make up for three speakers at frequencies it was not design to play with great efficiency.

 

[GregBe]

Thanks guys,

David, That is what I initially thought, but when I ran the frequency sweeps with the mains as large by themselves with no sub, they were extremely strong in spl down to 100 Hz, and dropped off from there. I didn't make sense when I added the sub in, the whole it created went past that number up to 120Hz. Maybe it was a cancelation issue as Wayne had mentioned.
Here is something else I did last night that is certainly not the norm. I wanted to test out the new setup with speaker level inputs. I played a scene from the Sopranos that isolated Tony's voice. I switched back and forth between Dolby Digital where his voice is coming from the center channel, and Stereo which moved the voice to the mains. The Dolby Digital version sounded much thinner and very weak in comparison even though all three front speakers are identical. (At this point my center was set to small with the bass crossed over at 120Hz and sent to the sub which is wired with the mains set to large).
On my sub, I noticed that it additionally had a set of speaker level inputs for the center channel. I never had heard of this before, and the manual says that it is for "Dolby Surround receiver in WIDE mode", but I figured what the heck why not try it.
I hooked up the center as well as the mains to the sub through speaker level inputs and set all three speaker to large, so I could control the crossover for all three with the sub. What happened was awesome. Mr. Soprano's voice sounded full and deep in Dolby Digital. I went and played some other deep voices such as Mel Gibon in Braveheart, Ed Norton in Fight Club and Russel Crowe in Gladiator and the whole system sounded a ton better.
I am not sure if what I did was completely wrong, and I am sacraficing in other areas, but for now it sounds a lot better. I will try it today at much higher volumes and play some music and bass heavy scenes as well. I guess it shows that you can't be afraid to try different things, and go with what sounds best to you.
Any thoughts or criticisms would be greatly appreciated.
What other areas could I be sacraficing to have my system set up this way.
Greg