STF-1 or STF-2

[goombawa]

Hi all :) First post here on these forums...

cschang pointed me this way when I posted a question on subs over on the AVS forum. It appears that the STF-1 fits my exact requirements:

1. Size. I live in a small NY apartment (are there any other? ;) and my listening area is 9x11.5, although the entire room is about 20x11.5 (there is an open kitchen at the end of the the living room). However I'm really only concerned about listening from the sofa.

The only place I can put the sub is in the Northeast corner of the room - couch is on South wall; plasma is on North wall; kitchen is to the West; radiators and windows on the East wall. Suffice it to say that the STF-2 would be the largest sub I could get, but the STF-1 is a perfect fit.

2. Sound. As I explained to curtis, I don't have the need to "feel" my bass so to speak. Being in an apt doesn't lend itself too well to shakin' couches. ;) So, what I'm looking to do is "fill in the tone" below that which my fronts can't reproduce. Currently I have Vienna Accoustics Weberns on either side of the plasma (50") which are rated 60Hz-25KHz, so I need to get the tones below 60 to fill up the sound. My receiver is a Denon 3803.

So.....on to my question. I think the STF-1 will be perfect but I'm just a little curious as to the extra -8Hz bottom end on the STF-2. I think 150W is enough power though, and don't think I really need the 200W of the STF-2. Due to the size of my place, I don't need a gigawatt of power. ;) How much of a "tonal" difference is there between 32Hz and 25Hz? The answer is likely not a linear one but if anyone could tell me from first-hand listening to these two subs that would be great. I'm very close to getting one of these (my first sub, btw...) and any help would be greatly appreciated.

Thanks. :)

[goombawa]

Unfortunately I think I need to take the STF off my list. I didn't realize it was downfiring and I need to "try" and minimize the boom for the people who live below me. As such I need to look at forward firing subs like the DT ProSub 80 or the Velo DLS3500.

Too bad, though, since I liked what everyone had to say about the HSU subs. :(

[Lwang]

A downfiring sub does not mean the sound is the loudest toward the bottom. If you put a front firing sub in the middle of a room and walk around it, you will hear very little difference whether you are in front or behind the sub. What you might hear more when you are in front are the higher order distortions when the sub reaches near or beyond its limit.

One way to minimize the sub's loudness to your neighbor is to place the sub very close to the listening position. This way, you will hear more direct sound as compared to the reflected sound (the sound bouncing back and forth between the walls/floor/ceiling, which is also most of what you heard when you walked around the sub). This allows the absolute level of the bass to be lower, thereby disturbing the neighbor less.

[goombawa]

Thanks lwang. I'm confused...doesn't a downfiring sub push air downward to reflect off of the floor, whereas the front firing pushes it out laterally? As such wouldn't there be less boom heard below me? I know that even front firing will be heard below as well... it's just when comparing to a downfiring I would think there'd be less. However I do realize that a boom is a boom and you can minimize the boom effect outside the apt walls only so much without soundproofing. But I guess the way my apt is placed (i'm in the corner of my apt bldg and on the top floor, so I don't have neighbors on 2 of my walls nor any above me) I would rather boom the walls/ceiling than the floor as much as possible.

I get the point about location but unfortunately my place is such that I don't have any other option but the NE corner of the room. However, I will say that I am in no danger of getting to the sub's limits very often as I am pretty vigilant about volume so as not to upset the neighbors. So I really need a sub which adds bass tone at low-med volumes.

[Lwang]

The sound would radiate out like a sphere, with much of it moving horizontally out from under the sub. The rest, even if it is reflective off the ground, does not mean it is like a hammer banging on the floor. Your downstairs neighbor would hear much more of the sub from the flexing of the floor as a whole.

If what you state is true, then nobody would make downfiring sub since there would be so much sound loss due to the sound wave transmitting through the floor as soon as it is launched from the woofer.

You could still get a slab of stone sized bigger than the area of the sub and put it on top of that, and maybe a little piece of rug between the two.

[goombawa]

I didn't realize that...I thought the downfiring sub leveraged the floor as a "bounce board" to radiate the sound. The reason I thought companies made them was potentially for better bass via the use of the floor, as opposed to front firing which would dissapate faster in the air. I guess I'm showing my noob-ness with this theory...sorry. ;)

So, in conclusion, you are saying that the STF-1 will not be heard any louder direcly below my apt than the DT ProSub 80 at the same levels?

[DavidD]

Also remember that the deepest bass is coming out of the port, which, I believe, is in the back.

[sputnikv8]

No reason you couldn't turn the sub on its side. Voila... now its "front firing". :D

As was said, you're neighbors aren't going to be "thankful" you got a front firing vs. down firing. What you'll need to do is place it (as was said) close to your viewing position so the overall volume on the sub can be kept low and you still get desired results.

[Ajax]

I, too, live in an apartment. And though I've got no one below me, I still am concerned about disturbing my neighbors.

Would it be possible to minimize the disturbance to goombawa's downstairs neighbor by placing the sub on some sort of dampening material. What if, under the sub, one placed a 2 or 3 inch thick pad of a rubber like material, or any other material that would absorb vibrations, then top that with a thin piece of plywood, covered with a hunk of carpet so the spikes wouldn't just sink into the rubber? Would that reduce the vibrations transmitted through the floor and joists? If so, what effect, if any, would that have on the sound of the sub?

I think all apartments should be soundproofed at the managements expense. Don't you? :D

[goombawa]

Originally posted by DavidD
Also remember that the deepest bass is coming out of the port, which, I believe, is in the back.

Interesting. Can anyone confirm this?

[Ddavidson]

Confirmation is complete.
The majority of the lowest bass comes from the port, while most of the subwoofers "higher freq bass reproduction" comes from the driver. If you run a slow frequency sweep through the sub you will see where the port comes in to play and then where it fades away as it gets higher up the range.

Those big long waves come from the port and this is why port noise can come into play when things get low and loud. Pushing such big sound waves (especially loudly) means you are going to be squeezing a lot of air through that port which can really get the velocity up if its too small.


Ddavidson

[Ajax]

Originally posted by goombawa
Interesting. Can anyone confirm this?

To my knowledge, it is correct. The deep bass comes from the port, and the mid-low bass comes from the woofer itself. I read that somewhere in either this forum or the Axiom forum.

[goombawa]

Someone posted this answer to my same question on another forum:

"Bass energy is absorbed by the walls and floors. A downfiring sub will transfer energy into the floor first. A sub that's front firing /w a rear port will transfer it's energy into the walls first which will then travel through the floors. Downfiring subs tend to shake the couch a little more for that reason. They tend to be preferred for HT."

Hmmm...

[Dudley]

Even if that is true, the real deep bass that would shake a couch is coming from the port which is in the rear. To see for yourself, go to an audio dealer and bring a long a disc with some test tones. When the real deep stuff starts playing there will be huge amounts of air coming from the port, and the woofer will not be moving as much as it was for higher tones.

[Michael Bain]

Rest assured, the Hsu is no boombox. The others have it right. At the lower operating frequency range, essentially all of the bass comes from the port.

[gr1m]

hi,
will be moving into a house with a 19x16 living room, 65" Mits RPTV on the long end of the room. now, would the Ventriloquist be enough for this size room? we'll most likely be doing 99% HT. if the Ventriloquist won't do, I'm leaning towards Paradigm bookshelves all around to go with an STF-2. pls advise.

[goombawa]

Spoke to support today and he said that there is no difference between down and front firing with respect to the effect off the bass hitting the floor.

While I'm sure he was not trying to mislead me, I still do not believe this to be the case. It simply defies logic. Air is being pushed downward towards the floor as opposed to outward into the room first. The "net" effect of the bass may sound the same from the listening position on the couch, but I still believe that if you measure the dB or SPL or whatever directly underneath the downfiring sub it will be more than the frontfiring sub. Hence it will be heard more readily by people living below me. Of course, at a certain volume it doesn't matter. But I'm talking about med level volumes.

I wish they would do a test like this to confirm either way. I think that this would be a fairly common concern for people in apartments.

In any case, unless I can find some other information on this, I think it is time to look at the Def Tech 80. Either that or I will have to build a platform of wood and rubber to absorb some boom.

[cschang]

goombawa,

I have actually been told that it does not make a difference as well....and it did not come from Hsu support.

[tdekany]

Originally posted by goombawa
Spoke to support today and he said that there is no difference between down and front firing with respect to the effect off the bass hitting the floor.

While I'm sure he was not trying to mislead me, I still do not believe this to be the case. It simply defies logic. Air is being pushed downward towards the floor as opposed to outward into the room first. The "net" effect of the bass may sound the same from the listening position on the couch, but I still believe that if you measure the dB or SPL or whatever directly underneath the downfiring sub it will be more than the frontfiring sub. Hence it will be heard more readily by people living below me. Of course, at a certain volume it doesn't matter. But I'm talking about med level volumes.

I wish they would do a test like this to confirm either way. I think that this would be a fairly common concern for people in apartments.

In any case, unless I can find some other information on this, I think it is time to look at the Def Tech 80. Either that or I will have to build a platform of wood and rubber to absorb some boom.

Forget about Def Tech subs - you will get so much midbass boom your neighbors will hear it no matter what.
For applications like yours the clear choice is upward firing subs. Their selling point is that " you can push our subs as hard as you like without your neighbours suspecting anything" . When I lived in New York I had a pair of down firing hsu subs. Never had any complaints. Of course accurate low bass that comes out of quality subs like HSU can and will shake the whole building. It will be felt everywhere. Get a VTF3! here or used on Audiogon.com.
I hope I was helpful.

[goombawa]

Originally posted by tdekany
Forget about Def Tech subs - you will get so much midbass boom your neighbors will hear it no matter what.
For applications like yours the clear choice is upward firing subs. Their selling point is that " you can push our subs as hard as you like without your neighbours suspecting anything" . When I lived in New York I had a pair of down firing hsu subs. Never had any complaints. Of course accurate low bass that comes out of quality subs like HSU can and will shake the whole building. It will be felt everywhere. Get a VTF3! here or used on Audiogon.com.
I hope I was helpful.

What are some upward firing models? (or were you joking?) I need to keep the width to 12" max. Upward would be ideal in that I live on the top floor, i.e., nobody is above me. :)

[Michael Bain]

The low bass is not firing into the ground. On the contrary, with this ported design, the low bass by design flows through the ports at the rear of the sub.

[goombawa]

Then why have a downfiring design? And how can it not be pushing air out of the bottom if the woofer is moving in and out? I understand that air will also move out of the port, but I still cannot see how a woofer that is located on the bottom of a cabinet does not reflect sound off of the floor, given the air is being moved directly towards it.

[Michael Bain]

The downfiring design sometimes helps to make the subwoofer slightly less directional and less easy to locate where the bass is coming from. Also, the woofer is less exposed, and there is no need for external covering. If you observe the woofer behavior on the Hsu true subs, at very low frequencies the woofer is barely moving. Almost all of the bass is coming from the ports. This is one of the reasons why it is highly recommended to have at least 3 inches of space between the ports and the rear wall.

[Lwang]

The wavelength is so long compared with the diameter of the driver that sound radiates out omnidirectionally, the floor, in conjunction with the bottom of the cabinet, act as a slot loaded coupled cavity.

Hsu recommends roughly 3 inches between the port and the wall. If your logic is true, then the amount of air that is moved through the small port (relative to the woofer size) should be pumching holes in the sheet rock.

Also note, most music subs are down-firing, while HT subs are front-firing.

Here is what Dr. Hsu said in an interview:

http://www.goodsound.com/features/2001_08_01.htm

SE: I've noted that many subwoofers with good reputations for music applications use down-firing rather than front-firing drivers. Is this just coincidence or does it reflect a particular design philosophy?

PH: I feel that's just a coincidence. In the case of the VTF-2, the down-firing design was chosen to save money. A down-firing woofer doesn't need a grill to protect it. The upcoming VTF-3 will have a forward-firing woofer because the box is larger. We feel it would look too plain and large without a grille.

[goombawa]

Originally posted by Lwang
The wavelength is so long compared with the diameter of the driver that sound radiates out omnidirectionally, the floor, in conjunction with the bottom of the cabinet, act as a slot loaded coupled cavity.

Hsu recommends roughly 3 inches between the port and the wall. If your logic is true, then the amount of air that is moved through the small port (relative to the woofer size) should be pumching holes in the sheet rock.

The larger woofer size compared to the smaller port size actually supports my logic. The fact that the placement of the sub should be 3" from the wall means (to me) that yes, there is air coming from the port which needs to be reflected off of the wall. However, this says nothing about the amount of air being pushed downward by the woofer. Hence I still don't see where there wouldn't be more direct sound hitting the floor from a downfiring sub vs. a frontfiring. I mean, the frontfiring design has *nothing* pushing air downward. How could there not be less of an impact on the floor?

Originally posted by Lwang
Also note, most music subs are down-firing, while HT subs are front-firing.

Here is what Dr. Hsu said in an interview:

http://www.goodsound.com/features/2001_08_01.htm

SE: I've noted that many subwoofers with good reputations for music applications use down-firing rather than front-firing drivers. Is this just coincidence or does it reflect a particular design philosophy?

PH: I feel that's just a coincidence. In the case of the VTF-2, the down-firing design was chosen to save money. A down-firing woofer doesn't need a grill to protect it. The upcoming VTF-3 will have a forward-firing woofer because the box is larger. We feel it would look too plain and large without a grille.

I get what he is saying here and it makes sense. However, there would be no reason for him to say "there is a side effect of a downfiring design which is more bass hits the floor". And I wouldn't really expect him to say that ... primarily because if the "net" bass effect of both designs is equal, i.e., they sound the same from the listening area (with the possible exception of the aforementioned "harder to detect where the bass is coming from" effect) then it is a moot point...UNLESS you are concened about the boom effect below you.

This may not be an issue for alot of people but for apartment dwellers I think it is a valid concern. I still think a simple test of measuring the SPl/dB underneath each type of sub would be a worthwhile effort IMO.

[Lwang]

The larger woofer size compared to the smaller port size actually supports my logic. The fact that the placement of the sub should be 3" from the wall means (to me) that yes, there is air coming from the port which needs to be reflected off of the wall. However, this says nothing about the amount of air being pushed downward by the woofer. Hence I still don't see where there wouldn't be more direct sound hitting the floor from a downfiring sub vs. a frontfiring. I mean, the frontfiring design has *nothing* pushing air downward. How could there not be less of an impact on the floor?

A 10" woofer would have 6x the surface area compared to a 4" port. So there would be 6x the velocity coming out of the port.

Due to the length of the wavelength, it is not reflecting off the floor, but more of a change in pressure in the region between the sub and the floor, and with its effective design as a coupled cavity, it acts as a slot for compression and rarefactions of the air into the room.

If you want to isolate anything, you should replace the cone feet with some supersized superballs, since the inertia force from the driver would have the greatest effect on transimitting its kinetic energy to the floor.

[goombawa]

Thanks for the explanations lwang. I think we're getting closer to an answer. ;)

"A 10" woofer would have 6x the surface area compared to a 4" port. So there would be 6x the velocity coming out of the port."

I won't debate this, but again I'm not concerned about the port nor the relationship of it's air movement compared to the woofer's. It is the absolute value of the woofer's impact that I am focusing on. The port could have 1000x the impact but that still has nothing to do with the absolute value (non-relational) impact of the woofer's air movement on the floor.

"Due to the length of the wavelength, it is not reflecting off the floor, but more of a change in pressure in the region between the sub and the floor, and with its effective design as a coupled cavity, it acts as a slot for compression and rarefactions of the air into the room."

Interesting comment. I'm not an audio engineer (obviously) so I can't comment technically on the difference between "region pressure" and "air being pushed onto the floor". Doesn't it take two sides to create pressure in a region, i.e., the floor and the woofer? In that case I'm still not getting the difference.

"If you want to isolate anything, you should replace the cone feet with some supersized superballs, since the inertia force from the driver would have the greatest effect on transimitting its kinetic energy to the floor."

This is a sound (pun intended) idea, but I would assume this would be useful for any sub, not just a downfiring. Cushioning the vibrations from the entire housing definitely would lessen the impact and is likely to be my plan when I get a sub.

[Lwang]

Interesting comment. I'm not an audio engineer (obviously) so I can't comment technically on the difference between "region pressure" and "air being pushed onto the floor". Doesn't it take two sides to create pressure, i.e., the floor and the woofer? In that case I'm still not getting the difference.
You are talking about flooring the area equal to the size of the subwoofer. If you are going to flex the wood floor/multiple layers of plywood base enough in that small area enough so that it re-transmits the sub's sound from its own vibration, then you are talking about some serious pressure. The higher pressure region quickly dissipates into the lower pressure around the perimiter of the sub, hence their coupling.

This is a sound (pun intended) idea, but I would assume this would be useful for any sub, not just a downfiring. Cushioning the vibrations from the entire housing definitely would lessen the impact and is likely to be my plan when I get a sub.

You can't do that with a front firing sub, since it has to be coupled tighly to the floor in order to minimize its own front/rear driver intertia while the sub is in action. A down-firing sub would have to fight its own weight. If it was to move, it would still stay stationary in relation to the floor.

What the downstairs neighbor hears is the whole floor being flexed (and re-transmitting the sound) while responding to the room being pressurized by the sub.

[goombawa]

"The higher pressure region quickly dissipates into the lower pressure around the perimiter of the sub, hence their coupling."

Fair enough, although I would say that in the area of the higher pressure there would be the equivalent of a "knock" which you would not get with a frontfiring.

I guess the last thing I would say is this... if possible it would be great if you would measure the SPL/dB/(whatever) beneath an STF and a frontfiring sub in the lab and post the results. If what you say is true it should be able to be proven with actual numbers. Again, I'm not saying you are not correct in theory...but as we all know it is what happens in practice that really matters.

I guess I'm just one of those thick-headed people that need proof. ;)

"You can't do that with a front firing sub, since it has to be coupled tighly to the floor in order to minimize its own front/rear driver intertia while the sub is in action. A down-firing sub would have to fight its own weight. If it was to move, it would still stay stationary in relation to the floor."

Good to know. I guess I'd need to use something like a rubber sheet for the pegs of the ff sub to dig into to prevent sliding.

[Michael Bain]

In your analysis, you need to factor in the fact that the Hsu woofer is barely moving at the very low frequencies, where essentially almost all the bass is coming from the ports. This woofer behavior was described in one of the Hsu sub reviews, in case you are wondering. http://hsuresearch.com/reviews/index.php?id=12

[Lwang]

Fair enough, although I would say that in the area of the higher pressure there would be the equivalent of a "knock" which you would not get with a frontfiring.

As much sound as eminating from the side of a cabinet. In the floor's case, it would be wooden floor & multiple layers of plywood plus whatever is in an apt's underflooring. That compared to 3/4" MDF in a sub.

[david_da_kine]

Try putting your ear close to the speaker ... doesn't sound much louder to me than standing on the other side of the room.

Or, just try an experiment. Point the speaker against a wall and go into the adjacent room. Rotate the sub in different positions. I doubt there would be any difference.

[sputnikv8]

The biggest issue you are going to have with neighbors is simply a matter of output. If you put either down/front firing too loud -- they are going to hear it!

Get the sub you want and get a long enough cable so that you can put it by your seating position so that the couch/chair will get more of the sound sensation at lower volume and your golden.

[DavidD]

I don't think any of us are going to be able to totally convince you. The fact is that subwoofers can be a problem in apartments. Bass does tend to travel through walls (and floors too, I guess.) However, I think that the downfiring driver is not likely to cause noticably more disturbance than a front firing driver. Your best bet, if you can manage it, is to keep the sub in a nearfield location, preferably right behind your chair. I can't speak for Dr. Hsu here, but I believe he often recommends that positioning.

[DavidD]

P.S. Don't forget there is a 30 day trial available. If you're not happy with the sub, you can return it.

[Dudley]

Won't both types of sub transfer more sound directly through their feet to the floor below than from the woofer?

Suspend it from the ceiling! :D

[sputnikv8]

Originally posted by Dudley
Won't both types of sub transfer more sound directly through their feet to the floor below than from the woofer?

Suspend it from the ceiling! :D

Or, mount it to the ceiling. Since he's on the top floor all the energy from the driver can then harmlessly go out to the roof.

:)

We're just playing. Honestly... you're either going to have to try positioning it close so you can use low volumes...or not get it at all.

[goombawa]

Thanks guys, I know you're only trying to help. :)

Can't move the sub to the south wall (where my couch is) due to space issues and the fact that the south wall is next to another apt. The only place it can go spacewise is in the NE corner of the room. Actually this is the best place for it anyway since the east wall is the windows (I'm 17 floors up...not much to bother out on that side) and the other side of the the north wall is my bedroom, which then faces out the north side of the bldg where again there's nothing but 17th story air.

Can't put anything on the east wall as it is all radiator.


outside air

=====north wall=======|
........................................|
...............bedroom.............|
........................................|outside air
........................................|
=doorway===wall=======|
........plasma/mains....sub....|
........................................|
........................................|outside air
...................couch..............|
=====south wall=======|
.........................................|
...............neighbor..............|


Anyhoo, I'll keep thinking about it and post back. :)

[goombawa]

Well, I pulled the trigger on the STF-1. Wish me luck with the neighbors. ;)