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Hi,


First off, Im using a JBL SCS178 and a H/K AVR2000. I was experimenting with the subwoofer's phase switch (0 or 180 deg) because I'm trying to eliminate a big dB dip in AVIA's test tones near the H/K's crossover (I connected the sub to LFE out). The thing is, no matter which switch postition I set it up, there is always a volume drop dependng on the sub's phase. When it's at 0 deg, the drop occurs at around 110 Hz, while at 180 deg, the drop is at around 90 Hz (which is interestingly +/- 10 above/below the H/K's 100 Hz crossover). So which setting is preferred then? Is there any way to eliminate this big volume drop completely?


Also, is it better to connect the front right/front left speakers to the subwoofer in order to use the subwoofer's variable crossover dial or is my subwoofer's connection to the H/K's LFE out and the 5 speakers' connection to the corresponding speaker outs on the H/K more ideal?
 

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FS1,

The purpose of the phase switch (on some subs it is variable from 0 to 180) is to correct a problem where bass coming from more than one source is out of phase and cancelling each other out. If you only have one sub, you shouldn't need to use it. That is, unless you have set your speakers to large, in which case you have base coming from your mains.
 

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I have a contrasting viewpoint from kabillyhop.


The phase switch should be set to whichever position gets the flattest in-room frequency response, as measured via your SPL meter.


If possible, can you try a few locations around your room, to see where you get the best overall frequency response? Different positions in the room will allow you to either (A) maximize output by corner loading or (B) get smoothest response in a number of positions.


In terms of "better" for connections, I recommend running all speakers as small and feeding the LFE output to the subwoofer. Running main speakers as large, with no subwoofer and utilizing the internal crossover puts some serious demands on the main channels.


Assuming you had the crossover dial set at about 60 Hz, you would require 112dB output on each main from ~60Hz to 120Hz. Most main speakers aren't designed for this level of output, and you've also just required that your receivers amplifier take over full range amplification out to the level of the LFE channel, only to "throw away" the 1-2 octaves that use up the most power by crossing them over to the subwoofer at speaker level.


Most speakers are not designed to have 112+dB of SPL capability from whatever crossover frequency you choose in the subwoofer out to 120Hz.


Hope this helped.


Regards,
 

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a typical room resonace mode is around 60-80hz, depending on room dimensions; it could be made worse if two or more of your three room dimensions are similar.

primary res =((1/2)(1,100ft/sec)/(room dimension) or 55hz and 10', 68hz and 8 feet (typical ceiling ht). after the primary, there are secondarys as well.
 

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What about the option of "both" when sending bass to the mains and sub. I seemed to get a flatter bass response in this mode, but I didn't spend a lot of time on relocating the sub as there aren't too many options. When I set my mains to large and send bass to sub only, the sub doesn't get a signal. It's either mains small/sub only or mains large/both, to get the sub active. My receiver (yamaha rx-v3200) is fairly new so I'm still feeling my way around.


Terry
 

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Terry,


I'm not going to tell you which of these is right for you......


It sounds like you're talking about stereo tracks only with this particular post.


By definition, a "large" speaker should be capable of full range reproduction, so there shouldn't be need for a subwoofer to assist the speaker. So Mains large+Sub bass only would get no engagement of a low-pass/high-pass pair.


Mains small + sub will engage a low-pass/high-pass filter pair, with low-pass going to sub, and high-pass going to the main speakers.


Mains large / both will engage a low-pass filter, which derives the info below crossover frequency and routes that to the sub while leaving mains full range.


Mains large / both has the potential of overdoing bass between the crossover frequency and the -3dB point of your main speakers. Some people might like that added bass boost.


Hope this helped.


Regards,
 

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Thanks John, I'm still experimenting and it never hurts to get imput from those more knowledgable even though it's my ears that count. ;)


Terry
 
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