Film-Tech Forum ARCHIVE: weak subwoofer output

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Posted by Charles Dale Carter (Member # 2315) on 04-01-2004, 04:41 PM:

I've got a digital Panasonic receiver/decoder hooked up to some KBH (cheap, I know) speakers. The 5 speaker system has a non-powered subwoofer that receives L and R channels then disperses to FtL, FtR, RL, and RR. In stereo mode it puts out good bass, but in surround modes (DTS and Dolby digital) it is very weak.
Am I going to have to get a powered sub for better performance or do I have something hooked up wrong? (Yes, I did follow factory directions). I've got DVD, VCR and Digital Cable hooked in.

Any help/clues would be appreciated! Thanks!

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-01-2004, 04:44 PM:

Some recievers have separate crossover points for surround mode (or no crossover point at all for other modes). Make sure the crossover is turned off or set as low as possible.

Posted by Charles Dale Carter (Member # 2315) on 04-01-2004, 06:32 PM:

Daryl,
Thanks for input. I'll admit to my ignorance here, but I don't recall reading about any crossover points or coming across any crossover settings. I'm out of town right now, but I'll check that out when I return home over the weekend.

I need to correct one thing I said, the subwoofer only puts out the front L & R. Rears come from separate jacks on recvr.

Receiver's got a subwoofer jack, so I wonder if I just hooked up the sub to that and used regular L & R jacks on recvr front channels if that would help.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-01-2004, 07:03 PM:

Normally the reciever only has a sub pre-out (line level) which is no good for your unpowered sub.

If there's no crossover point control for the surround mode it's probably permanently set at 100Hz which would explain why you get little sub response out of the left and right channels in surround mode (other modes often bypass the crossover for a more natural sound for those formats).

If you've got the cash, two or three 18" powered subs would make good end tables. [Smile]

Posted by Charles Dale Carter (Member # 2315) on 04-01-2004, 08:56 PM:

Thanks, Daryl. I'll check that stuff out when I get home. Yeah, wouldn't 2 subs be really cool? However, don't think my wife would be so enthusiastic. If I can't resolve my issue, I'll probably go out and get a powered sub.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-01-2004, 09:08 PM:

Hey, you need matching end tables. They're the right height and 18" subs generally have the right size top surface.

Posted by Ron Lacheur (Member # 1126) on 04-01-2004, 10:14 PM:

Check your speaker size selection. Most modern Home Theater receivers have a SMALL and LARGE setting for all the speakers in the surround set up.

Selecting SMALL will roll off the low frequencies to the subwoofer and will produce more impressive bass response.

There aren't many Home 18" subs that I've seen that are worth what they are charging ( ie Velodyne ). For the price of a single Velodyne, I'm sure you could get 2 JBL 4645C with the necessary amplification and x-over for less than the price of the Velodyne and will blow it out of the water.

Posted by Charles Dale Carter (Member # 2315) on 04-02-2004, 02:27 PM:

Ron,
I do have those settings and I think it is set to SMALL, but will check and see. Thanks for model specific recommendations. JBL makes good stuff for the right prices. My Dad chose JBL systems when refitting an old theater he bought several years ago, replacing the monolithic Altec tower and horn behind the cinemascope screen.

Posted by Darryl Spicer (Member # 711) on 04-03-2004, 01:13 AM:

What you want to do is set your speaker sizes to large if the speaker wires are going from the receiver to the sub then to the left and right speakers. If you have them set to small the low frequency is diverted to the low frequency pre-output of the reciever for a powered subwoofer. By having them set to large the full frequency is sent to the left and right speaker outputs, that full signal will go to the sub, the sub will pull off the low frequencies at the subs crossover pont and then send the rest to the left and right speaker. Normaly on a lot of receivers when you just run in stereo all this large small size is bypassed and you have the ability to set bass and trebile levels.

Oh, one other thing, when running in Digital modes DTS and Dolby. You will not get the full bass extention that the process provides. This is only availabe through the pre-amp output and you will need a powered sub-woofer for that.

Posted by Charles Dale Carter (Member # 2315) on 04-03-2004, 01:26 PM:

AHA! Darryl, I think you have given me the crucial clue. For it is indeed when I'm trying in DTS or digital that performance is so weak. Looks like I need to buy a powered sub to get that rumble in my thunder again.

Posted by Ron Lacheur (Member # 1126) on 04-03-2004, 01:41 PM:

Just thinking about it again, when you start fiddling with the small and large settings, make sure you set Center on Large and keep it there. The lower end in the center gives a more presence in the dialog, IMO.

Posted by Mike Olpin (Member # 1115) on 04-08-2004, 01:12 PM:

A really great sounding home theatre speaker package on a budget:
(I use these in both of my setups)

Front and Rear L & R
KLH 911B $20.00/pair

Center
Sony SSMB150H $60.00/pair (I use one in each setup)

Sub
Sony SAWM200 $99.00

Posted by Ron Lacheur (Member # 1126) on 04-08-2004, 01:19 PM:

I really can't suggest a sub lower than 10". The frequency rolloff is too high ( an 8" is more in the 35-40hz range ) and the driver just take a beating on DTS soundtracks when played at a reasonable volume.

All three fronts should be the same or at least the same manufacturer for more seamless transistion from panning dialog/effects.

Posted by Charles Dale Carter (Member # 2315) on 04-09-2004, 02:08 PM:

Thanks, Mike and Ron, for such specific recommendations and obviously experienced advice. [beer]

Here's to some better sounding DVDs in the future!

Posted by Bobby Henderson (Member # 840) on 04-09-2004, 07:47 PM:

You can get away with using a 10" powered sub if your home theater system is set up in a small room. But that is also provided if you get a good quality unit. I have a Paradigm PS1000 sub and it has more than enough oomph for my listening space.

Another added tip, most receivers have a single line out for a subwoofer. But most subwoofers have 2 line inputs. If you get a good Y splitter (such as the little doohickeys sold by Monster Cable) you will get an extra 6db of gain by plugging into both subwoofer ports.

Posted by Charles Dale Carter (Member # 2315) on 04-21-2004, 02:19 PM:

Bobby,
What do you consider small room? My tv room is around 19X19. I haven't had a chance to try out any of the above folks' suggestions yet, but I will when I can get some free time away from honey-do's. What do you think of the Bose 3-2-1 system? Too good to be true from just three speakers?

Posted by Ron Lacheur (Member # 1126) on 04-21-2004, 05:57 PM:

I don't recommend Bose speakers. Despite how good their marketing is, their product isn't all that great for the price you pay. Cheap drivers and their box contruction isn't that great either.

Posted by Bobby Henderson (Member # 840) on 04-21-2004, 06:17 PM:

I would consider a room "small" if it measures under 225 square feet (15' X 15' approx.). My living room is just 16' X 12', a pretty small cubic area of space. With a room roughly 20' square, I might consider bumping up to a sub with a 12" driver and at least 500W of amplification.

I don't like Bose products. Their systems just don't have the bottom end of a traditional surround sound speaker package (and the midrange is greatly lacking as well). On top of that, the price just isn't right. It's entry level gear at a high "mid-fi" price. For what Bose charges, you're better off spending a couple hundred or so more for a set of Paradigms.

Regarding the Bose 3-2-1 speaker system, as well as ALL would-be "surround sound" 2 speaker and 3 speaker systems, none of them work as advertised. If you want REAL surround sound for DVD, DSS, HDTV, etc., you have to go with at least a six speaker setup.

Lots of people get suckered into 2 and 3 speaker systems for two reasons. First, they believe all the psychoacoustical techie hype coming from companies like SRS that you can get surround sound from two speakers. Second, women latch onto the idea because there will be less stereo system hardware visible. Many ladies are more interested in making the living room look good rather than having things in the living room that makes you want to be in there (such as a kick ass home theater system).

Now, if you are wanting the best home theater surround sound coverage, get a receiver and speaker package that supports Dolby Digital Surround EX and DTS-ES. Instead of having two surround sound speakers, you'll have four. One pair goes to the back wall and the other pair goes to your side walls. The better receivers will have various 5.1 and 6.1 modes to properly treat and divide speaker pairings. Still, with DD-EX, you have to be careful about enabling that with some DVDs (like "The Abyss" for instance). Many films originally mixed for 70mm Dolby mag release will feature mono surround summed across the LS and RS channels. Activating DD-EX modes on those types of DVDs will cause all the surround activity to collapse to the back wall pair of speakers.

Posted by Charles Dale Carter (Member # 2315) on 04-23-2004, 05:59 PM:

Thanks for the advice fellas. I've got no plans to scale down to 3 speaker system, given your glowing denunciation of the much-touted Bose equipment. I was mostly curious what you thought of it. I'll definitely stick with the six speaker system that I've got now--just trying to improve on them. The technical expertise that eminates from this site is truly amazing to me. You have a question about airplanes? Ask me. When I have more questions about theater stuff, I'll keep coming back here!

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-23-2004, 07:35 PM:

How many parts fall off of a DC Late on a typical landing?

Posted by Charles Dale Carter (Member # 2315) on 04-24-2004, 08:27 PM:

Depends on who's flying--Captain or First Officer (or flight attendant sitting in either's lap)

Posted by Charles Dale Carter (Member # 2315) on 05-14-2004, 07:12 PM:

I've finally had a chance to play around with all my speaker/amp settings following all of your advice. The output is considerable weaker in surround and DTS modes even with the changes. I think Daryl is right. I'm gonna have to buy a powered sub. Luckily, some advice there has already been given! Thanks for your help. [Smile]

(sorry! I meant Darryl (Spicer))

Posted by Brad Allen (Member # 470) on 05-15-2004, 11:19 AM:

Home speakers that will blow your socks off for a fair price.
Onix Rocket speakers

Charles, have you used a sound pressure meter to properly setup the sound levels of your speakers? The system will sound only as good as your setup procedures.

Posted by Ron Lacheur (Member # 1126) on 05-15-2004, 01:28 PM:

The Onix Rockets have been a favorite among the Home Theater community for sometime now. They are a web based company ( like Axiom ) but offer solid performing speakers for the dollar.

Posted by Charles Dale Carter (Member # 2315) on 05-16-2004, 08:57 PM:

Brad I don't even know what a sound pressure meter is, much less have one to use to set up my speakers. [Confused]

I use a distance setting based on seating position v. speaker location. These settings are preset into my receiver. Thanks for the sales advice on a powered sub. Those look like real nice units! I'll need to do some extra flying to get one,though. [thumbsup]

Posted by Ron Lacheur (Member # 1126) on 05-16-2004, 09:06 PM:

A sound pressure meter measures the volume of sound in decibels.

It is used with a pink noise tone from a calibration dvd such as Avia or Digital Video Essentials.

Most common SPL meter used for home applications is Rat Shack's Meter.

Posted by Charles Dale Carter (Member # 2315) on 05-17-2004, 10:49 AM:

Thanks for the info Ron. When I get my new sub, I'll look in to buying or using a meter to fine tune system. I'm afraid, though, that my ears may not be as refined as some, but I'm willing to give it a shot.