View Full Version : Crossover question?
03-05-2003, 02:59 PM
For example, If I have a HT system below:-
A/V Receiver: Denon AVR-3803
Center: Polk CS400i - Large
Fronts: Polk RT800i's - Large
Surrounds: Polk F/X 1000s - Large
Back Surrounds: Polk RT38i's - Large
Subwoofer: Velodyne CHT-15 - Yes
Now, If I set 60hz for the crossover on my receiver because I'm using large setting for speakers. What crossover should I set on my subwoofer?
My goal is to get the bass from all the speakers including subwoofer. I'm using LFE out from my receiver and then Y-cable, 'cause the subwoofer only has a line level input.
Thanks for the help.
03-05-2003, 03:04 PM
You don't even need to set the subs crossover... max it out and you will be fine.
You don't want to double filter and thats what I'm trying to prevent from happening.
03-05-2003, 03:10 PM
I guess you mean that I've to bypass the subwoofer's crossover to the max. in other words cancelling the crossover so it won't interfere with receiver's crossover because I'm already using receiver's crossover. Using double crossover doesn't make any sense anyways.
I think I got you!
03-05-2003, 03:19 PM
You got it Bud!
03-05-2003, 03:38 PM
Good advice HBomb. Cascading both filters is a no-no. By virtue of its low pass filter, the AVR will ensure the CHT-15 sees virtually no signal above say 100 Hz. If you set the filter on the CHT-15 to its max setting, there will be nothing TO filter at that frequency and this will have the same effect as bypassing it altogether.
The use of a Ysplitter is fine, but not needed. Either the left or right will do fine. The only thing the Y-splitter does is double the strength of the input signal, so the sub plays 3 dB louder. The same can be accomplished by turning up the plate amp a bit.
Regardless, I would set your LFE volume on the AVR to -3 and adjust at the plate amp for calibration purposes.
Also, you will have to set your speakers to small in order to send the bass from them to the sub, regardless of your selected filter point.
Bear in mind the typical high pass filter rate is 12 dB/octave in order to smooth the transition to the sub. Selecting a filter point of 60 Hz may create a situation where you are asking your center/surrounds to play a signal which is below their F3 point.
This in turn may create a depression in the FR centered around 50 Hz since both your speakers and the AVR will be rolling off at the same time.
If you want to try 60 Hz as a filter point, my advice is to first run an FR sweep on your center and surrounds to determine the true roll off of each speaker to help you select the best filter point. Just set your sub to off/no and all your speakers to large and run the sweep on each speaker with the others disconnected.
Since your Denon cannot select the filter point individually for each speaker, the speaker with the highest F3 is the limiting factor for your entire system and you can logically select your filter point with confidence.
Since the high pass filter is not a brick wall, I would select a filter point of at least half an octave above the highest F3 of your speakers. Otherwise you will probably see a depression in the FR below that point until the sub takes over completely at the lower frequencies.
03-05-2003, 04:00 PM
Thanks Dr. Spec!
Let's say If I want to direct more bass to my sub and still want to keep little bit but safe for the speakers. What setting should be the best? Once again I want to keep large setting for all of my speakers.
How about setting 80hz in the receiver and bypass to max. in the sub.?
03-05-2003, 04:20 PM
The only way to tell for sure is to run an FR sweep on each speaker and see how deep it really goes before it nose dives.
And you HAVE to set your speakers to small in order to select ANY filter point in your AVR. Setting them to large sends them a full range full power signal with no filtering over to the subwoofer.
For a vigorous HT environment where you will be blasting pretty loud, and taking into consideration your high pass filter rate is probably 12 dB/octave and your speakers will be still playing well below your filter selected filter point, I tend to err on the side of conservative and am comfortable with 80 Hz.
If I owned your AVR, I would definitely try 60 Hz in my own system, because I also use some pretty big center and surrounds and I like the thought of getting the most out of them - within reason.
But if my FR sweep showed any of them starting to roll off around 55 Hz, and/or if I felt they were straining at high volumes at a 60 Hz filter point, I'd go right back to 80 Hz in a heartbeat.
I play HT loud, and that definitely would factor into my decision on a filter point. Your surround speakers can easily take an 80 Hz filter point even at very high volumes.
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