LFE and the 500 Watt Amp's High Pass Filter

[Active Speaker]

If I connect my subwoofer to my main speakers via the 500 watt amp's high pass filter and set my receiver to: mains - large, no sub, will all the LFE effects present in Dolby Digital, DTS, & Pro Logic be routed to my main speakers (and sub)?

[Sasha_G]

If I connect my subwoofer to my main speakers via the 500 watt amp's high pass filter and set my receiver to: mains - large, no sub, will all the LFE effects present in Dolby Digital, DTS, & Pro Logic be routed to my main speakers (and sub)?

Yes, your setup will work. Sending the L/R signals from the receiver (L/R/C set to LARGE, NO SUB) to the 500 watt amp will work. The Center channel will have to provide its own bass.

However, if you have a Dolby Digital system, its often best to use the SUBWOOFER output. This will employ the Digital crossovers in the receiver, and you can send the center channel's bass to the subwoofer as well.

The only advantage of using the 500 watt amp's crossover in surround systems is that our crossover has a steep 24 db/Oct slope, so that the integration between L/R and the subwoofer will work very well. However, some quality receivers have slopes as steep.

[Active Speaker]

Sasha,

I have a B&K AVR202 & the manual says that I can direct all the bass to the left & right speaker; I'd never heard that bass would still go to the center. I'm really concerned that I might miss the LFE information from DD, DTS, & DPL by hooking things up this way; will I miss anything?

[Lwang]

I think DTS standard specifies that the center channel's bass not be routed to any other channel or LFE, no matter what. So even with the center to small, low bass meant for the center in DTS would still go there. At least that was what I was told.

[Active Speaker]

Where did you hear this? I've looked everywhere, including the DTS web site, and I find no mention of this. They do say that it is most desirable to have three identical front speakers, but they also say that 5 speakers set to small or 3 to small and large mains are acceptable. I'm just trying to determine if I will lose any LFE information if I set my mains to large with the sub connected through the high pass filter of the 500 watt amp.

[Lwang]

Meridian told me this. Obviously, most companies don't follow this implementation.

[Active Speaker]

Well, I've scanned the old Harmonic Discord Forum, the Hsu thread on the AVS Forum; I've been to the Dolby & DTS websites, I've searched Stereophile, Sound & Vision, Stereophile's Guide to Home Theater, avguide.com, etc... Does anyone know the answer to this question: If I use the active crossover in the 500 watt amp and set my mains to large (the LFE out is not used in this arrangement), will I lose any information that would normally be output via the LFE in Dolby Digital, DTS, or Pro Logic, OR will I still get all the home theater info (DTS center channel excluded)?

[Dudley]

No. If the mains are large the LFE info will go there. In fact some people prefer to do it this way (I forget why off the top of my head, but it made sense at the time) . This was gone over in much detail on sound & vision 6 months or so ago.

[Active Speaker]

Dudley,

Do you remember the exact issue? Thanks.

[Dudley]

http://www.soundandvisionmag.com/idealbb/view.asp?topicID=19709&forumID=40&catID=1&search=1&searchstring=&sessionID={43FFB3FD-6673-47BC-BBF9-001FB92CD9D1}

The link above discusses the issue. It seems that the main advantage is if you are using stereo subwoofers (this is different that using a y connector to split the LFE to two subs - instead you send the pre-amp Left and Right each to a different sub)

[Nigel_Pl]

Hi Active,

I have set my SUB to NONE and my MAINS to LARGE and the LFE signal is definately being redirected to my Front speakers.

Regards,
Nige

[Active Speaker]

Hi Active,

I have set my SUB to NONE and my MAINS to LARGE and the LFE signal is definately being redirected to my Front speakers.

Regards,
Nige

How can you tell?

[Nigel_Pl]

I just used a Dolby Digital/DTS test disc then ran a LFE test...the LFE came out of the front channels which are connected to my main speakers + TN1220. Try the opening credit sequence of "Fifth Element" with the SUBWOOFER set to YES while keeping the Front channel outputs connected to the TN1220 so the LFE signal cannot be heard. Then try setting the SUBWOOFER to NONE which will redirect the LFE to the front speakers and the TN1220. Believe me you will be able to tell the difference without an SPL meter.

[Active Speaker]

Thanks. How "hot" do you run the 1220 for music & movies? What did you notice sonically when you first connected the sub in terms of improvements?

[Nigel_Pl]

Thanks. How "hot" do you run the 1220 for music & movies? What did you notice sonically when you first connected the sub in terms of improvements?

Well for music I run it 0db in relation to my mains and 0-3db when it comes to movies. The TN1220 really filled up the bottom end in some music with very low bass content and provided the extra head room with bass heavy DVD's which really added to the visceral impact of the movie.

[Lwang]

How can someone run the sub hot unless they have all their speakers set to large and let the sub handle LFE exclusively? You are getting a stepped boost in the bass on everything, music, main speaker effect, etc. Unless the pre/pro or receiver has LFE adjustment (not just sub) for specific source

[Active Speaker]

Good question, Lwang; do you have the 500 watt amp? I think that Nigel understood perfectly what I am referring to (thanks Nigel). On the 500 watt amp, even using the high pass crossover and setting only the mains to LARGE, you still get gain control. So, currently, I have my 1220 set about 10 db "hot" for music & at least 20 db "hot" for movies (I haven't measured with my spl meter for home theater yet). What this means is that all the bass lower than 51 hz (the crossover) is set higher then flat (my whole room is highly absortive, so this currently seems to be the best mix). I LOVE this sub!! Last night I was watching "Treasure Planet" & during an explosion, my pants' leg actually were moved by the wind (and the 1220 is 4 feet away, BEHIND another speaker!!)!! I'll probably eventually get around to setting everything "flat", but right now I'm just having TOO MUCH FUN!! Thank you Dr. Hsu! Best $1000 I've EVER spent on audio!

[Nigel_Pl]

How can someone run the sub hot unless they have all their speakers set to large and let the sub handle LFE exclusively? You are getting a stepped boost in the bass on everything, music, main speaker effect, etc. Unless the pre/pro or receiver has LFE adjustment (not just sub) for specific source

The bass from both the MAINS, CENTER and LFE are 3db higher for movies.

[Nigel_Pl]

Good question, Lwang; do you have the 500 watt amp? I think that Nigel understood perfectly what I am referring to (thanks Nigel). On the 500 watt amp, even using the high pass crossover and setting only the mains to LARGE, you still get gain control. So, currently, I have my 1220 set about 10 db "hot" for music & at least 20 db "hot" for movies (I haven't measured with my spl meter for home theater yet). What this means is that all the bass lower than 51 hz (the crossover) is set higher then flat (my whole room is highly absortive, so this currently seems to be the best mix). I LOVE this sub!! Last night I was watching "Treasure Planet" & during an explosion, my pants' leg actually were moved by the wind (and the 1220 is 4 feet away, BEHIND another speaker!!)!! I'll probably eventually get around to setting everything "flat", but right now I'm just having TOO MUCH FUN!! Thank you Dr. Hsu! Best $1000 I've EVER spent on audio!

Wow...thats pretty loud. Isn't the bass a little too loud in relation to the other frequencies? Can you lower the Sub volume and increase the main volume for a better blend?

[Active Speaker]

You've just identified my problem: my wife likes to listen very low, so I have no other choice at the moment.

[Lwang]

Active,

I do have the 500w amp & it is crossed @ 51hz. I did have my fun with the ultra hot setting, but eventually turned it back to flat for a more accurate music representation. If I want to feel the bass, I would just move to one of the seat that is situated right next to the woofers of the subs. It rattles the whole body, along with the whole sofa.

[Lwang]

I meant calibrated flat in terms of smooth transition from mains to sub, not just a white noise level match, which is no gurantee the transition is seamless with no freq abberations.

[Active Speaker]

I used test tones and an spl meter, not a white noise level match; is there another way to calibrate the transition from mains to sub? Are you using the high pass filter?

[Lwang]

I use an SPL meter and 1/3 octave warble tone, which I think is more accurate than spot tones centered at some freq. The main thing is to measure mains, sub and main+sub together to make sure it is a smooth transition, then of course you have to listen to see if it is seamless.

I do use the high pass filter, on both my main sub and center channel sub, since it is fruitless trying to get my maggies to move any amount of air at freq in which nothing comes out of them.

[Active Speaker]

Since all the readings concerning the 1220 that I got were within /- 1db as advertised, and the readings at the frequencies that my speaker's woofers are operating at are flat also, I think that the transition is accurate.