Down Firing vs Front Firing sub?

[kingofgrills]

Originally Posted by zoso0928

I currently have a 7.1 home theater system and i am using a down firing sub.. My question is : I have a front firing sub in a box..which would sound better in my set up? TIA

Front versus down firing on it's own shouldn't really influence the performance one way or the other. Whether or not the subs were sealed or ported and overall construction quality would make a bigger impact on sound quality.

[Blu-Dog]

Originally Posted by Fors*

Underlying the importance as you stated of the room itself and the sub's location. But based on your results in your room, to me anyway, I would say the bottom firing sub performed just as admirably as the front firing ones.

Blu-Dog, I hope you don't think I am agruing with you. I am simply "defending" my opinion of bottom firing subs and their performance.

No, I don't see it as an argument at all. Total volume in a room, ceiling height, furniture placement, floor and wall treatment, all go into play.

I haven't pulled the JL Audio Fathom into the room my Klipsch SUB-12 is in (the SOB weighs a ton, I hate dragging it around anyway) but I think it would be overkill...the Klpsch works best where it is. There is no "right" answer here.

My point is that for flexibility and options, I prefer front-firing. But I agree, my situations are not all situations, and I've listened to (and own/owned) some very nice down-firing subs.

The other factor - price - is huge. A sealed, front-firing sub requires huge amounts of power, and power is money. For an incremental difference, down-firing, ported subs offer a very good alternative - often overly sufficient for many environments. I don't mean to come off as an elitist, as I haven't always been in the position to purchase a monster like the JL.

I'm just enjoying the discussion, it pries knowledge out of people.

[kareface]

The principle argument I tend to agree with Blu-Dog with, but I don't agree with a lot of the points that he made. Blu, I'm going to pick on you here, don't take it personal, lol.

Originally Posted by Blu-Dog

Small areas do fine with any sub source, at much lower cost for down-firing models.

I disagree with this. Based on my experience I believe that larger rooms, or larger distances between the source of the bass and the primary listening position have less impact on the source. I've done quite a few calibrations. At that point you're dealing mainly with room reflections as oppose to direct waves or near field effects.

It is still true that a front firing sub gives you a small degree of additional control over the quality of the sound, but to the average consumer this is pointless. If you can find a gallery that has a front firing but that isn't A) parallel with a wall with the front in the general direction of the listening position or B) pointed directly at the listening position then I could see your argument. In the position I had my sub at for the test, pointing the sub away from the primary listening position produced more even response. How often have you seen anyone do that? It's more likely that people will place their subs in the 2 configurations I mentioned above and reposition the sub until they find a placement that meet that criteria. In that vein, the down-firing subs would be no different.

Originally Posted by Blu-Dog

Rare is the down-firing sub that doesn't have a port coming out of the side. Many people make the mistake of thinking the port doesn't make sound; it does, usually the majority of the sound output. Of course, you know this; I've seen you champion even more radical designs.

Deeper bass will come from most ports as they are designed mainly to extend the LF. However I think it might be misleading to say "the majority of the sound" as it will be dependent off the wave length the port is tuned to and the crossover of the AVR. I will agree that most ports will produce the majority of the deep bass. It's pretty easy to tell, just close up the port and run a sweep. I will admit that closing the port will change the Q of the sub, but in most cases that would adversely affect the driver only benefiting the test results in favor of the port. With that being said, assuming a THX standard of 80hz crossover for the AVR, you'll see the majority of the frequency response will be produced by the driver. You'll lose the low end roll off tho, your sub won't go nearly as deep.

Originally Posted by Blu-Dog

Sound waves propagate in odd ways, based on more that just the frequency of the sound. Sound is energy moving air. Subsonic sound is not some freak of physics; energy is used, to move air, at a lower frequency.

It isn't a freak, but it is very different when compared to mids and highs. Low frequencies are very low energy, when the energy is passed between molecules they require a much more direct collision then higher energy waves to propagate effectively. Imagine you are in a sand trap with a golf club. If you very slowly push the club through the sand, most of the sand will simply get pushed to the side with a small wave of sand in the front. Now if you if you speed up that swing by several factors most of the sand you impact will be flung in a very narrow dispersion from the source of impact. Because of the low efficacy of the LF transmissions, the sound spreads much faster then higher frequencies and takes more energy to reproduce at equivalent volumes. You can recreate this effect with mids and highs by using non directive speakers like dipoles. They sound quieter even if the same drivers are used when compared to monpoles because more energy is required to perceive the same volume at the listening position. LF is unique in it's interaction simply because of the nature of the medium, our atmosphere. If you changed the air density you'd change the nature of the sound.

Originally Posted by Blu-Dog

This energy is diffused by whatever surfaces it strikes, either directly, or as secondary or tertiary reflections. If it's a floor, it rebounds, and immediately strikes against its source - the speaker driver. This sets up interference waves, a natural occurrence.

The only problem I have with this comment is you are thinking of sound only as a wave, and not describing the medium. In a completely open space a wave will travel pretty uniformly out in all directions (described by the inverse square law). In that instance thinking of sound as simply a wave is appropriate. However, this doesn't consider the source and the room.

Starting with the source, a speaker or sub does in large degree radiate lower frequencies in all directions. The directionality of the sound increases as the frequency does. (I'm aware that you know this, I'm just stating it for clarification sake) This can be seen when doing near field measurements. If you get too close to the speaker the results change greatly. There is a point where if you get close enough to the sub, you'll see sharp increase in the air velocity. There is a sphere of air around the sub, moving from the driver to the back of the sub that produces great speeds when the driver is in use. This is created by the air following the path of least resistance.

LF because of it's tendency to have poor propagation efficiency likes wrapping around solid objects. This is because the objects reflect the energy that would normally continue to disperse in the air. LF moves faster when running along a solid surface then nativity through the air because more of the energy is being effectively used. This creates a bubble of displaced air around the sub that radiates out once it runs out of surface area. As you go lower, the propagation efficiency continues to decline and the displacement is more likely to cling to solid objects. The energy will follow the path of least resistance, very little of the energy will be reflected at such a short distance directly back at the driver. Just like how the microphone can't be used to accurately measure a sub if it's too close to the driver, the influence of the floor is very minor unless you increase the air gap between the driver and the floor. In other words at that distance sound doesn't act like a wave quite yet, very little rebound will occur.

You can see this effect as room gain, when you get a sub closer to a corner more of the energy is effectively being used and the perceived volume increases. For this reason you can't think of LF or any sound waves strictly as waves. You have to account for the nature of the medium as well. Bass gets deeper if you place a sub against the wall. Obviously this isn't always ideal, as it frequently changes the quality of the sound. Most subs were designed and tested in a scenario where there are few room influences. This is a good idea because you can't design a sub that will work the same in every room. However, this means that the influence your room has on the sub can hurt the intended reproduction.

Originally Posted by Blu-Dog

If it's a floor, it rebounds, and immediately strikes against its source - the speaker driver. This sets up interference waves, a natural occurrence.

Ug, I think this is a terrible description of interference waves. Interference waves will almost always radiate away from the source, not directly back at it. In this case interference waves would radiate sound away from the driver, actually hurting your case. If what you described was true, many folded horn designs wouldn't work or there would be major dips and peaks in down firing subs.

Originally Posted by Blu-Dog

I personally find this feature easier to control with front-firing subwoofers, along with easier placement for finding the room's "sweet spot". I own and enjoy both types of subwoofers, and have dealt with this issue at length and under different types of circumstances.

You have more options in a given space, that isn't indicative of being easier. I will agree that front firing subs allow for greater control, but easier implies that one option will frequently work better then the other, and this simply isn't the case.

Originally Posted by Blu-Dog

I would say it's less important for movies than with music, unless it's a large room - the larger the space, the more important it is to control the direction of the sound. I won't settle for boom boom boom; I want to sound to hit, then quit. Banging subsonics off the floor and waiting for the delayed tone to wander to my listening position via several reflected surfaces is a second-best solution, at least for me.

I don't agree with this. The further you get from the source, the greater the number of reflections, the less the direct nature of the sound will be influential. Most people prefer a diffused sound with bass as it's more natural to what we'd normally perceive. Smaller rooms can produce greater directionality and near field effects that make the direction of the source a little more evident. Simply because you had a couple situations where it was easier to find a sweet spot for a front firing sub when compared to a down firing doesn't mean that is a rule of thumb.

Originally Posted by Blu-Dog

The Klipsch units are excellent. They're fast and clean, if not over-driven. They will clip, and the huge port limits their range, but if dialed in right, they're terrific subs. But they induce delay - they can't "snap" sound, the way the Fathom can, an example being kick drums in music tracks.

This is a red herring. Delay you refer to has more to do with the speed of the driver and the position of the sub then it does with the direction the driver is facing. There are plenty many down firing survo sub owners that will tell you that down firing =/= increased delay or 'crispness'. You are comparing apples and oranges.

Originally Posted by Blu-Dog

First, give me this "scientific proof that bass waves are non-directional"...

The waves don't lack directionality, tho they will spread out much faster then higher frequency waves. What lacks directionality is our perception of the waves. We evolved into an environment where LF was uncommon and largely unnecessary for survival. Our ability to perceive directionality and tonality of LF is terrible. This is the entire reason why we don't need a subwoofer for each channel. If you were to move all of your speakers behind your seat and listen to a movie, you'd noticed right away. However, if you do the same with your subwoofers it's much harder to notice and if done right almost impossible.

I tried to describe it in a way that would be easy to understand. Most of the principles I described are much more complex and have to take into account other factors. This topic makes me want to do a series of tests. Depending on how much time I have I might get around to it this weekend.

[Blu-Dog]

Originally Posted by kareface

The principle argument I tend to agree with Blu-Dog with, but I don't agree with a lot of the points that he made. Blu, I'm going to pick on you here, don't take it personal, lol.

Good post! I need some time for clarification of my points, will get to it on Saturday...I'm in general agreement with most of this, but there are some things I have some small issues with.

[JOMV]

Originally Posted by Blu-Dog

Good post! I need some time for clarification of my points, will get to it on Saturday...I'm in general agreement with most of this, but there are some things I have some small issues with.

Almost 2 years and I'm still waiting for your findings!!!
This thread had me VERY interested as I'm one of those who think there must be a difference between them. I'm also searching for a new subwoofer.

[Blu-Dog]

Originally Posted by JOMV

Almost 2 years and I'm still waiting for your findings!!!
This thread had me VERY interested as I'm one of those who think there must be a difference between them. I'm also searching for a new subwoofer.

I just built up a front-firing dual subwoofer to complement my JL Audio F-113. It uses two JL Audio 12W3-V3 subs, in a ported configuration - drivers and ports both front-facing. Just finished it on Monday, more after I try it out on Expendables 2...

[Blu-Dog]

Originally Posted by JOMV

Almost 2 years and I'm still waiting for your findings!!!
This thread had me VERY interested as I'm one of those who think there must be a difference between them. I'm also searching for a new subwoofer.

Yes, it's been awhile, and I've made some changes. I'll update more fully after some pictures.

What I've done is built a dual subwoofer, front-firing, and ported. It's an experiment, and has been surprisingly successful. The object was to augment the JL Audio Fathom F113, a sealed, front-firing, 13 inch subwoofer with a 2000 watt amplifier, situated on the left side of the room.

The Fathom is a beast. From my experience, it runs effectively from about 20Hz to it's limit of 80Hz (limited from the receiver). The placement in the room faces towards the opposite right wall, which has huge openings for a doorway and a "window portal" giving the room an open feeling, but gives huge nulls off-axis from the sub.

The Fathom is facing the normal listening position for my wife and I when we watch movies. The sub tones are powerful, pounding sound directly into the listening position, with very meaty bass. This doesn't make for pervasive sound; it just bends the skull into something from a Dali portrait, and snatches air right out of you lungs. As a basshead, this is an enjoyable experience, in doses.

My aim was to have a more spread out sound. I have used dual down-firing Klipsch subwoofers, but they did not have the power to fill the large space, and in the open environment, much sub was lost. It's why I got the Fathom in the first place.

I robbed another home theater in my house of two JL Audio 12W3v3-4 subs, which were in sealed boxes. I found that sealed boxes did not work very well with the 12W3 drivers; they were stifled in there, and played very softly. The 12W3 is a tight, sound-quality sub, extremely efficient, and fast, without mechanical noise. While the sound was tight and clean, they did not have tremendous Xmax to produce prodigous bass (not required in that theater) but I felt they were wasted there.

As I am suspicious of down-firing subs in a large area, I built a box using both subs, using a low profile configuration 42 inches wide, 20 inches high, and 9.5 inches deep, divided into separate chambers for each sub. Instead of a single, 35 inch by 15 inch slotted port as called out by JL, I used two ports of 2 inch round PVC tubing, with a total length of 16 inches, for each chamber. There is an L bend of "wide turn" PVC 90 degree tubing right at the exit point at the front of the sub, so that both the ports and the drivers face forward.

The sub is powered by the same QSC 2450 amp that I used to drive the subs in a sealed configuration. This runs at about 800 watts per channel, with each sub running from it's own channel from this two-channel amp (though there is a single signal running to the amp from the receiver, split between the Fathom and my custom unit).

As a solo unit, the sound is amazing. I had never heard the output of the 12W3 drivers be that strong, even with the same amp. The sound is very clean - maybe slightly less clean than when sealed, but the differences are so slight I really can't tell the difference. The ports have no noise other than pure sound output, even though they are not flared in any way.

But even standing alone, the bass output still does not match the Fathom. Two drivers, in a ported box, still cannot match the output from that monster, which is still in a class above it. It certainly would suffice in any theater, including mine, but there is a difference.

But goal was not to build another Fathom; it was to fill out the sound. This was very successful. The sub had to match the room's visual esthetics, a fetish with my wife (who insists on perfect sound AND visuals) so the box went below a wood and stone side table, fitting in nicely. We did not want a big ugly box sitting out on the floor. The box is behind the normal listening position we use, with a table between us and the listening position, and ultimately facing a high wall where the TV and front speakers are. Sound is diffused only by the table and the two chairs.

The sound is profound.

I tried it with Expendables 2, a DTS 7.1 film that has very good clarity and a few scenes with powerful bass, but didn't take advantage of subs like I thought it would. Frustrated, I went into the archives.

First, I tried an amazing concert film - the Police's Certifiable. This is a Dolby Tru-HD 5.1 exercise in clarity and stunning bass and percussion work, and is an audio test standard for me. If you do not have this, please get it. "King of Pain" will change your way of looking at your home theater, no matter what kind of rig you have. The plucking sound of bass, and the snap of the drums was precise and fast.

The best overall sustained test of bass comes from Transformers: Dark of the Moon. This 7.1 exercise, from the opening credit Ironhide Sweep to the incredible devastation of Chigago is the real test of subwoofer capability. The front-facing ported rig filled the large area with the multi-toned bass of the film (it's not all borderline subsonics, the sound is all up and down the scale) and between the Fathom and the custom rig, the entire area was enveloped in sound.

I've tested this setup with other films - not yet with Master and Commander's first battle, I haven't worked up the nerve - but I will say that having a face-forward subwoofer is absolutely acceptable, without compromise. Whether a down-firing sub would do the same, no matter the aspect of the ports, I can't say, but I prefer this arrangement, especially in a large area with lots of obstructions.

If it is possible, see if you can get a sub meeting the design of front-firing driver and ports. You will be happy, even if your neighbors aren't.

[JOMV]

good post!.... I still think there must be a difference. The best subs are front firing and it has to be a reason why.

[JOMV]

I guess this thread died again!!!... It is one of the most interesting I've seen..