what's the pros and cons of down firing vs front firing

[Sheep]

Buck,

That was some weak advice.

Axiom wasn't the first to have front firing driver and ports (my athena is hte same). The sound also doesn't just come from the port.

The way the subwoofer is situated in its position is key to how it will sound. Not every one knows what will have when you turn things this way and that.

Experiment with it, but theres nothing wrong with a rear ported sub, or a ported one for that matter. Its the Box, driver and amp that will determin if it is a good sub or not.

SheepStar

 

[Hi Ho]

My down firing sub reproduces bass as coming from the front speakers for music.

See its placement:

As for LFE, it will follow sound movement. For instance, in "Flight of the Phoenix", in the opening scenes the aircraft appears at low altitude coming toward the audience then flies over our heads. The LFE follows that movement in a very dramatic way.

Hahaha, I have that exact same blanket in my living room.

Anyway, I have only owned front firing subs and have no experience with down firing other than in-store demos. I think both sound perfectly fine.

My DIY sub has the port right below the driver, see HERE, The plans were for a down firing sub. I modified them a bit to make it front firing.

 

[toquemon]

I have one front-firing and another floor-firing and I can't tell the difference between them. So It's pretty much the same.

Another, very audible differencie is between ported and non-ported designs. I checked two B&W non-ported of like a thousand watts each and I can say that I undestood what the word "musical" really meant.

 

[awesomebase]

Need Good Driver

Well, nobody mentioned the effect of "sag" on down-firing subs. That is basically the slight sag/compression of the driver's material due to gravity. In general, a good driver won't distort because of this, but if you're not sure, you should get more information on your driver's tolerances for this.
The advantage of down-firing subs comes in to play if your sub is considerably heavy. If it is light, then you get more muddled up bass. A heavy down-firing sub with good spiked feet will produce crisp bass with very little resonance. That is the main objective for those subs. With front firing, you are battling resonance going forward and back; something that is much more difficult to control though, again, spikes do a good job of planting a heavy sub in the floor. It is just that physics comes in to play in terms of where the force is being pushed.

 

[mfabien]

My down firing sub weighs 78 lbs.

 

[WmAx]

A heavy down-firing sub with good spiked feet will produce crisp bass with very little resonance. That is the main objective for those subs. With front firing, you are battling resonance going forward and back; something that is much more difficult to control though, again, spikes do a good job of planting a heavy sub in the floor. It is just that physics comes in to play in terms of where the force is being pushed.

I'm not exactly sure of which resonance you are describing. The mass of a typical enclosure vs. the typical speaker cone mass is not going to allow any significant movement. Some minor movement may occur(as to show up as a blip in the impedance curve or a tiny frequency response anomoly) that is directly related to the resonant frequency of the mechanical coupling to the floor. Let's say you set a speaker with no feet on a surface. The broad flat area would not make good contact with the floor unless both surfaces were essentially perfect flatness(not likely). This would potentially cause a resonance to be excited, directly related to the coupling point(s). Another example would be to mount the speaker on an undampened spring-like surface. This would cause the largest excitation of resonance(since the undampened narrow Q resonant freuquency would allow high amplitude peak at this frequency). Spikes ensure a stabile mounting. But this can cause resonances related to the resonant frequency of the floor structure if it is a wood supported floor. A proper isolation(no rigid coupling) platform that has a resonant point below the bandwidth of the subwoofer and also has good self dampening, is the ideal mounting method for some wood supported floors that will react as described.

-Chris

 

[Tomorrow]

A proper isolation(no rigid coupling) platform that has a resonant point below the bandwidth of the subwoofer and also has good self dampening, is the ideal mounting method for some wood supported floors that will react as described.

-Chris

And in the real world, that translates to what kind of platform...for say an Hsu VTF-3? I would guess a rug has proper isolation and a resonant point below the bandwidth of most subs. ??

 

[WmAx]

And in the real world, that translates to what kind of platform...for say an Hsu VTF-3? I would guess a rug has proper isolation and a resonant point below the bandwidth of most subs. ??

Actually, a rug may not be sufficient. It might seem like that, but when you get down to the weight(of a heavy speaker) vs. surface the resting area, you may end up compressing the carpet to basicly make a more or less rigid coupling through at least most of the bass band. If the carpet is very stiff and does not compress, then it is going to have a rather high resonant frequency. It takes a delicate balance between the two variables. You may have to use many thick layers to get a substantial effect. In my attempts, a layer of carpet was never sufficient. I once used several layers of thick carpet mixed with a few layers of carpet padding foam(ending up being like 3"-4" thick over all) that worked well for most the bandwidth, but not as effective as I would have liked. I later changed the suspension to use compliant rubber foam blocks(I wanted to this initially but could not find the appropriate rubber at an appropriate size), that with the right mix, ended up at a resonant point below 20Hz, effectively de-coupling the entire band mechanically. Of course, with the thickness and low stability of these materials in these configurations, I did have to build a platform with a lower section and upper section that the materials could be inserted in between, with a metal shaft guide on each corner(along with foam rubber isolation rings on the shafts) to ensure stability.

-Chris

 

[awesomebase]

Just the point

My point was just to explain that down-firing subs have different physics with regard to resonance than front-firing subs. I wasn't trying to explain or predict the actual outcome, I just wanted to explain that the physics of either design comes into play and that some subs take this into account when they design their cabinets, others don't. In any case, neither of them are expecting you to have 3 or 4 inches of carpet or padding. There is an expectation of resonance from the sub at certain frequencies regardless of your setup because they are not producing the subs based on individual room parameters but rather on what satisfies the most common or typical platforms, hence the spiked feet. So, whether one designs a sub for themself with these things in mind is what is more applicable. If you buy a sub, you have to deal with what you have. That means making an estimation on what would work best in your environment. In this case we need to evaluate whether or not a down/front - firing sub is ideal for the application based on the parameter provided. If everything is, considered "average" then definitely one can infer some common advantages/disadvantages in terms of design between the two based on the assumption of those parameters.
Otherwise, we'll be guessing a hundred different solutions to a problem that may or may not exist. What we probably need more than anything, is a clearer explanation of the required parameters. In other words, we need more info on the actual room and equipment, etc. That way, we can at least introduce differences that would be applicable to the setup.

 

[WmAx]

I just wanted to explain that the physics of either design comes into play and that some subs take this into account when they design their cabinets, others don't.

How do you design the cabinet to account for coupling resonance(s) or resonances related to floor vibration/excitation? The cabinet is not capable of, nor do I know of any parameter related to the cabinet itself, that can be changed to account for variable coupling. If you use the subwoofer mounted on spikes or hard rubber feet on a rigid floor, then their would be no excitable resonance(s) to account. For non rigid floors(many wood supported floors) they could build a suspension system into the feet to decouple the system mechanically for the bandwidth of the device from the floor; but I am not aware of sub manufacturer that does this.

-Chris

 

[awesomebase]

Design counts.

I'm not talking about cabinet design by itself. I'm talking about alternatives in design between front and down firing subs. A "light" front firing sub without any stable feet is most certainly going to increase resonance at lower levels. A "heavy" done firing sub may still do the same, but at a much lower frequency and without as much resonance. So, definitely, design counts! I think we're basically agreeing, but I'm not talking about the cabinet in terms of dimensions or the interior part of it where the driver fires from. I'm talking about the design as was specified as being either a) front firing, or b) down firing. It also applies to subs that use spiked-feet as opposed to not using them. All I'm saying is that it is hard to deduce what is needed when we're not sure what parameters we're working with here. Are we putting a sub on a wood floor? cement? tile? carpet? Are there closed walls? Are there windows? All of these things can certainly contribute to the decision of which works best. To make a global overarching statement that one type of subwoofer is better than another (i.e. down-firing vs. front-firing) just isn't wise. Aside from the subjectivity of what people consider "better", there are just personal preferences for how people like to hear sound.
The goal in any of these discussions is to sort through the information and make a good determination. In this case, we can't say get a down-firing or front-firing sub because we lack the proper parameters, never mind the personal preferences of the person asking. So, the best we can do, is give them information to consider when making the decision based on personal experience and education.
In this case, there are definitely differences in the physics associated with the movement and vibration of the sub when it fires to the front or to the floor. One has to be aware of this. There are also different requirements in terms of placement, mounting, etc. I'm not saying that one should design a cabinet that decrease resonance. I'm saying that there are elements to a sub's design that, when considering your set of parameters to work with (the demographics of the room, personal preferences, etc.), are applicable for making the proper choice.

 

[WmAx]

A "light" front firing sub without any stable feet is most certainly going to increase resonance at lower levels. A "heavy" done firing sub may still do the same, but at a much lower frequency and without as much resonance. So, definitely, design counts!

I think I understand your concern(s). However, in normal applied situations, front firing vs. down firing should not yeild any substantial difference(s) in this respect. In the rare circumstance that a very light enclosure is used in combination with a subwoofer with an extraordinarily high moving mass, then at very high excursion/incursion levels, some physical enclosure movement may potentially cause vibrational problems at the coupling point if the feet are not very well secured. In this narrow set of circumstances, I might expect your concern(s) to be valid. But then, it's easy to ensure a highly stabile mounting in such circumstance(s). Squarely placed rubber feet on a hard floor, or spikes on a wood floor(or on carpet as to puncture through to the floor), should yeild enough friction to prevent substantial effect.

-Chris

 

[awesomebase]

Agreed

I think I understand your concern(s). However, in normal applied situations, front firing vs. down firing should not yeild any substantial difference(s) in this respect. In the rare circumstance that a very light enclosure is used in combination with a subwoofer with an extraordinarily high moving mass, then at very high excursion/incursion levels, some physical enclosure movement may potentially cause vibrational problems at the coupling point if the feet are not very well secured. In this narrow set of circumstances, I might expect your concern(s) to be valid. But then, it's easy to ensure a highly stabile mounting in such circumstance(s). Squarely placed rubber feet on a hard floor, or spikes on a wood floor(or on carpet as to puncture through to the floor), should yeild enough friction to prevent substantial effect.

-Chris

I totally agree, and that was my main concern!

 

[Dolby CP-200]

In my experience, downfiring is less directional.

That is True.

 

[Johnd]

Haaa! Did you revive this two year old thread just to poke fun CP? You forgot the smiley face.

Whilst true some bass is localizable, the whole idea of bass in a theater is to make it non-localizable. Bass gets less directional the lower the frequency.

I just find that statement funny. The solution (to localizable bass) is then either a better sub, better placement, or two subs.

 

[dem beats]

hehehe

This is an insanely entertaining thread.

I'm going to create a sub with 6 18" subs that will have on on every face of a cube and then cut the corners and use those as the ports then tie strings to a nail in each corner of the room and connect them to the opposing corner thus finding the exact center of the room.. Then I shall hang my omnidirectional bass cube of doom from a bungi cable and run slack wires up it.

Then I will have perfectly dispersed bass.... Then I can sleep at night....

 

[Dolby CP-200]

The Ultimate sub the sub to end all subs!

Hmm how about 14x 18” subs, if you where to angle the edges at the top and bottom at 45° mind you it would be very huge kinder like a sea mine.

It would have leg supports surrounding it to hold it up from the floor, kinder looks like the LEM doesn’t it. I would imagine the darn thing would be so heavy to lift so the enclosure would need to be brought in separately providing you can get it though the doorway. Then lifting it, you’d need a mini crane to hoist it up while the supports are fitted securely once done you can start to install the x14 18” subs around it then hook it up and blow the WINDOWS OUT! LOL

 

[dem beats]

Hmm how about 14x 18” subs, if you where to angle the edges at the top and bottom at 45° mind you it would be very huge kinder like a sea mine.

It would have leg supports surrounding it to hold it up from the floor, kinder looks like the LEM doesn’t it. I would imagine the darn thing would be so heavy to lift so the enclosure would need to be brought in separately providing you can get it though the doorway. Then lifting it, you’d need a mini crane to hoist it up while the supports are fitted securely once done you can start to install the x14 18” subs around it then hook it up and blow the WINDOWS OUT! LOL

I will one up you. I will create a golfball 30' in diamater and use the placement of the dimples for the woofers. It will have to be made out of a special blend of rigid space ceramic with concrete and carbo resin reinforced walls. It shall be known as the stadium destroyer and shall be my first step in global domination!!!

 

[louthewiz]

I have 1 of each and I like them both,..,