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Old 22nd October 2007, 13:39   #1
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Default Need help understanding subwoofer controls.

Our JAMO (S406 + Yam RX-V357 amp) sub has a couple of knobs behind, that i've been wanting to know more about.

Would really appreciate it, if i could get some info on these and how they can be tuned to get the best LFE output.

1. Level
2. Cut Off
3. Phase
4. Sub has Left-Right cable input but the system came with one cable. Do i need to get a dual pin cable for better LFE output?

Shan2nu

Last edited by Shan2nu : 22nd October 2007 at 13:47.
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Old 22nd October 2007, 16:30   #2
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Originally Posted by Shan2nu View Post
Our JAMO (S406 + Yam RX-V357 amp) sub has a couple of knobs behind, that i've been wanting to know more about.
1. Level
2. Cut Off
3. Phase
4. Sub has Left-Right cable input but the system came with one cable. Do i need to get a dual pin cable for better LFE output?
1. Level to match level with main speakers. A sub should not be heard but it's absense should be felt.
2. CUt off. Usually mean how high do you want the sub to go. It depends on how good your main speakers are. the less you need the sub the better.
3. phase usually varies between 0 and 180 deg. It helps "align" the bass coming from the sub to sound in time with main speakers. since the sub is not placed close to the main speakers this feature makes the bass like it is.
4. Usually one input can be set to be used for mono input. If not a Y connector will more than suffice.
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Old 22nd October 2007, 20:52   #3
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3. phase usually varies between 0 and 180 deg. It helps "align" the bass coming from the sub to sound in time with main speakers. since the sub is not placed close to the main speakers this feature makes the bass like it is.
Ah, so this is where the prob is. The output from the sub wasn't in sync with the main speakers. Will alter the knob position till i get the desired effect.

Shan2nu
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Old 22nd October 2007, 21:01   #4
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May not be really off topic but Navin, what's the difference between a front facing and a down firing sub?
I'm under impression that a down firing sub can be kept anywhere. Please correct my impression.
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Old 22nd October 2007, 22:33   #5
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Quote:
Originally Posted by Rudra Sen View Post
May not be really off topic but Navin, what's the difference between a front facing and a down firing sub?
I'm under impression that a down firing sub can be kept anywhere. Please correct my impression.
If I may interrupt Navin...

Downfiring sub is no different from a regular front firing sub. There is a little bit of loading compared to a regular front firing sub.

You will mostly find this is home audio subs.

Last edited by Bass&Trouble : 22nd October 2007 at 22:35.
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Old 22nd October 2007, 22:36   #6
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B&T.. I'm lost. Little more detail please.

I've a JA AUDIO 10" down firing sub. Hence the question.
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Old 22nd October 2007, 22:46   #7
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Quote:
Originally Posted by Rudra Sen View Post
May not be really off topic but Navin, what's the difference between a front facing and a down firing sub?
I'm under impression that a down firing sub can be kept anywhere. Please correct my impression.
Rudra, in general below 80Hz or so both subs will perform similarly. It depends on the specific design.

A bottom facing sub couple with the floor and often gives the sensation of more bass. In most cases the space between the floor and sub is more than 3" or so and there is no mass loading. However if one wants one can bring the sub very close to floor and and produce partial air mass loading. Using air mass loading lowers the F3 of the sub/floor system at the cost of some sensitivity. down firing also means that your sub will be about 90 deg out of phase with your main speakers but that can be easily rectified as most activ subs have a phase compensating circuit built in.

However assuming all things remaining equal; the same sub in the same box facing down or facing forward. If my main speakers were capable I'd use down facing and use phase shifting to compensate. If my main spekaers were not capable (5" or less) I'd use front facing as I could then safely XO my sub higher and not have the midbass get all muddled by hitting the floor (smear).

REL, Velodyne, Bag End, JL Audio, etc.. all make some very good subwoofers. REL and Velodyne are dedicated solely to the art of making subs and dont make fullrage speakers.

Some of my favourite alignments: Nestorovic, Horn (yes Horn), TL (a la Bud Fried), and OB (Open Baffle). Each of them have their advantages and disadvantages.

Last edited by navin : 22nd October 2007 at 23:25.
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Old 22nd October 2007, 22:57   #8
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Hi Navin, while you were typing all this out, I PMed him something similar I think. Only, drawing an analogy with quarter and half space loading, I told him that the efficiency (or that as perceived) may increase on account of the loading rather than decrease.
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Old 22nd October 2007, 23:04   #9
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Man!! you guys are too technical!
Can I have a reply which is fit for for a normal human being like me?
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Old 22nd October 2007, 23:19   #10
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Quote:
Originally Posted by Rudra Sen View Post
I'm under impression that a down firing sub can be kept anywhere. Please correct my impression.
Neither sub can be kept anywhere. Even as low as 80Hz one can localise a sub if one takes the time and effort.

For music I am a fan of stereo bass.

Rudra, Especially for the kind of music you listen to I would suggest that you listen to a pair of TLs or Nestorovic or OB speakers. Unfortunately there are very few examples of these alignments around. Focal used to make drivers specifically for the TL alignment (B&T remember the J series 8K516J, 10K617J etc..). OB is not very efficient in the "bass per cubic foot" race but the quality of the bass of a good OB is hard to beat. I have heard the Linkwitz Orion (that too 5 of them used for HT, suplemented with 4 18" subs in IB for the last octave) powered by Pass's amps and it was pretty good. Many years ago I heard a custom system. AMTs mated to ScanSpeak 10" woofers in a TL even XOed at 800hz or so they made music. Oskar Heil who invented the AMT also invented the FET (Field Effect Transistor).

For home theater I'd like front and rear channels to be able to reproduce bass information. How else would you feel the T-Rex's foot steps behind you? The quality and quatity of bass required for Home Theater poses a seperate challenge.
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Old 22nd October 2007, 23:24   #11
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Originally Posted by Bass&Trouble View Post
Hi Navin, while you were typing all this out, I PMed him something similar I think. Only, drawing an analogy with quarter and half space loading, I told him that the efficiency (or that as perceived) may increase on account of the loading rather than decrease.
B&T think this. Increased Mms will drop sensitivity. But yes given that the down facing sub will most probably be placed along a wall it will given a percieved increase in bass. But often this bass will be muddy. It would be nicer if the sub was bought out into the room by 2-3 feet. Less bass but better definition.

Rudra, if you want a short explanation it is simple. There are no hard and fast rules. Think of the music system as a whole - the room, the electronics, the relative placements of the loudspeakers and listener. Trial and error are the order of the day and a compromise solution is almost always what one ends up with.
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Old 22nd October 2007, 23:27   #12
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Navin, I'm really lost here. This my 2 channel set up:

Harman Kardon 3480 amp/tuner
Mission 34i floor stander
JA AUDIO down firing sub
Denon DCD685 CD player

One hour ago I was playing Herbert Von Karajan's "the Legend" a memorial release. It sounded really good.
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Old 22nd October 2007, 23:47   #13
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But often this bass will be muddy. It would be nicer if the sub was bought out into the room by 2-3 feet. Less bass but better definition.
Yup, i've experienced this. Initially, i kept the sub (downfiring) in a corner where i was getting loads of bass but i couldn't really differentiate between the various low frequency notes.

Now that i've moved the sub away from the corner, the bass has reduced but it's much more distinct. Good for listening to music but when ever i watch a movie (with loads of sound effects), i prefer keeping it in a corner. This lets me enjoy the sub sonic waves passing through the floor.

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Old 22nd October 2007, 23:54   #14
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Originally Posted by Shan2nu View Post
This lets me enjoy the sub sonic waves passing through the floor.
I just passed out through the floor I think.
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Old 23rd October 2007, 09:13   #15
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Quote:
Originally Posted by Rudra Sen View Post
Navin, I'm really lost here. This my 2 channel set up:
Harman Kardon 3480 amp/tuner
Mission 34i floor stander
JA AUDIO down firing sub
Denon DCD685 CD player
Quite simply this is what I would do.

place the system along the long wall. Place the M34i about 3 feet from back or side walls. Toe in the M34i so that their axis cross about a foot in front of you. stick the sub in the center of the 2 speakers about 2 feet form the rear wall.

The JA audio sub looks like a slot loaded sub. IN this case I would stick to a XO no higher than 80Hz, preferably 60Hz. The M34i have dual 6" woofers and should be able to produce 60Hz without a problem.

I have heard the M34i (and M32i) and I would prefer it mated to something like the Arcam with an open cable like say Transparent Audio. With the Roksan Kandy and wired with Nordost Blue it sounded a bit dark. A good middle of the road preference could also be the Rotel or NAD.
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