Sealed smaller subs better for music?

[sigbergaudio]

Define full potential?

We get less vibrations, as well as needing less power and less excursion (= less distortion).
That is already quite some extra potential right there.
If you flip one of the woofers (inside out) and also flip its phase, the distortion will be even less.

I suspect you understand what I mean.

 

[OWC]

I suspect you understand what I mean.

maxSPL is what you mean or slightly lower -3dB point for the same maxSPL for one driver.

I am just trying show people that there is a lot more than that.

 

[OWC]

EDIT: But unless you're on a budget, you could of course eat your cake and have it too, by having TWO dual opposing subs.

Yes, although those vibration are quite a bit of debate how audible they are to be very honest.

The "excursion" of the side panels is very small at best, at least an order of magnitude (or more) than the excursion of the woofers themselves.
So we can kind of calculate and estimate its contribution.
Also they are fully correlated to the source itself.

So the negative contribution of it soundwise is very debatable.
In fact, I have never seen any objective experiments with quantitative data (aka real numbers) proving that it will have a negative impact on the overall sound (read: distortion).

But yeah, if there is no budget constraints, go for it.
For the same budget I would go for an active four mutli sub system any time of the day, since the negative impact of room modes is a lot worse.

 

[gnarly]

In fact, I have never seen any objective experiments with quantitative data (aka real numbers) proving that it will have a negative impact on the overall sound (read: distortion).

Here's my objective experiment....

Two stacked subs, one on top the other, either sealed !8"s or vented 18"s....same drivers.
Both stacks vibrate a lot when driven...both are very well built 3/4" baltic birch heavily braced cabinets. Will toss a beer.
Can hear transmitted vibrations induced into main speakers when sitting on the sub stack, and only the subs playing....mains completely off.

Put the two 18"s into an opposed cabinet. Won't spill wine from a glass, when cranking.
No sound from main speakers picking up any transmitted vibrations.

That's proof enough for me

 

[OWC]

Here's my objective experiment....

Two stacked subs, one on top the other, either sealed !8"s or vented 18"s....same drivers.
Both stacks vibrate a lot when driven...both are very well built 3/4" baltic birch heavily braced cabinets. Will toss a beer.
Can hear transmitted vibrations induced into main speakers when sitting on the sub stack, and only the subs playing....mains completely off.

Put the two 18"s into an opposed cabinet. Won't spill wine from a glass, when cranking.
No sound from main speakers picking up any transmitted vibrations.

That's proof enough for me

sound from main speakers? You mean mechanically induced vibrations to the mains?

 

[antennaguru]

I have found that sealed subs are easier to set up in most rooms, especially in frame construction rooms. They should have their woofer(s) aimed into the room, and NOT down-firing at the floor. The goal is for natural and not boomy bass, that appears to come from the main speakers.

I would disagree with small as an objective, unless you only want modest bass output. I prefer multiple large sealed subs.

Look at what Arnie Nudell did with the Infinity Reference Series that included 4 large towers, 2 of which were woofer towers that had lots of woofers each, in sealed enclosures. Plus they controlled the woofers with a feedback system with accelerometers on the woofers for accuracy.

 

[sigbergaudio]

@antennaguru Since we have a subwoofer that is designed to be either downfiring or have the driver play against the wall, I will happily disagree that it is important to have the driver facing you / into the room.

On the contrary, locating the driver close to a room surface will excite fewer room modes and reward you with a more even frequency response.

 

[HooStat]

locating the driver close to a room surface will excite fewer room modes

Interesting. I was going to start a thread on down-firing subwoofers, but this seems to make sense. I assumed there would be little difference since subs are usually right on the floor.

 

[Tangband]

Interesting. I was going to start a thread on down-firing subwoofers, but this seems to make sense. I assumed there would be little difference since subs are usually right on the floor.

You have consider the wavelengt for subwoofer freq. At 50 Hz its 6,86 metre.
So it doesnt matter much if its turned backwards. Of course , if the subwoofer amp have only 12 dB / oct crossover you can hear differences .

With subwoofers thats downfiring you might ( maybe ) get problems with the cone suspension after a couple of years, especially if the cone is heavy.

One important thing is getting perfect integration between main and subs. The crossover should be right with the right slopes and this is not only an electrical thing - perfect integration is in the acoustical domain . This is complicated since closed box mains and ported mains drop of with different acoustical slopes , even without any electrical crossover involved. So - ported mains or closed main speakers demands different order of crossover slopes in HP and LP filtering. It took me three years measuring with dsp crossovers and testing, listening to the results and reading about the theory behind it .

My conclusion about perfect subwoofer integration is its like opening a can of wormes. You have so many variables because of the rooms involvement. Correctly done it can sound good, if not, the sound gonna be worse with subs than without .

 

[abdo123]

@antennaguru Since we have a subwoofer that is designed to be either downfiring or have the driver play against the wall, I will happily disagree that it is important to have the driver facing you / into the room.

and what happens when the volume of Air the driver needs to displace is not immediately available? (this is a rhetorical question)

On the contrary, locating the driver close to a room surface will excite fewer room modes and reward you with a more even frequency response.

Do you have some evidence for this?

 

[Sancus]

Subs are omnidirectional. The acoustic center is the driver, however, not the center of the box. Other than that, there is no difference based on where the driver is facing. This is stated pretty directly in various sources like Toole(pg1).

Honestly, unless the sub is really big then even that doesn't matter much in most cases. I've never seen a case where different room modes were triggered by moving 12-18", it usually requires a few feet. I'm sure it is possible of course, but uncommon.

 

[Tangband]

I have had good results with DIY subwoofer drivers that has low qts ( 0,25 ) with a big motor, and low fs in small closed cabinets with Linkwitz transformer and a lot of amplifier power.

 

[DanielT]

With subwoofers thats downfiring you might ( maybe ) get problems with the cone suspension after a couple of years, especially if the cone is heavy.

Large , fat downfiering sub ,which can really pump air, there are other problems before that. Neighbors, if you live in an apartment. Then it can be a matter of days.

That in itself matters less, downfiring or not. Neighbors may have views on loud bass frequencies regardless of the type of subwoofer / speaker design.

Edit:
Sorry, if I mixed that damn reality into the equation.

 

[gnarly]

sound from main speakers? You mean mechanically induced vibrations to the mains?

Yes, that's what i mean.

 

[OWC]

Yes, that's what i mean.

In that case the subs and/or the mains aren't properly decoupled.

 

[OWC]

Interesting. I was going to start a thread on down-firing subwoofers, but this seems to make sense. I assumed there would be little difference since subs are usually right on the floor.

A huge down side of down-firing is that this will create a asymmetrical force.
Resulting in an dynamic as well as static off-set of the woofers, which means more (even order) distortion.
Although seeing some Klippel measurements, some woofers seem to have an offset to begin with, so technically one could compensate I guess.

 

[OWC]

Subs are omnidirectional. The acoustic center is the driver, however, not the center of the box.

At these wavelengths that doesn't really matter anymore, unless you have a very huge box were the distance between front and back is in de same order of magnitude of the wavelength of de bandwidth of the subwoofer.

 

[antennaguru]

@antennaguru Since we have a subwoofer that is designed to be either downfiring or have the driver play against the wall, I will happily disagree that it is important to have the driver facing you / into the room.

On the contrary, locating the driver close to a room surface will excite fewer room modes and reward you with a more even frequency response.

Well, you certainly could have found a better way to handle downfiring woofers than me. I will quickly agree that on a concrete floor they work just fine because they cannot overexcite the floor, but IME on all frame floors I have encountered I either had to put the subs on their sides or put Sonex foam underneath them to keep them from overexciting the floor and getting boomy. This was also the case when they weren't sealed subs and had a port on the bottom with the driver facing the open area of the room. This Sonex treatment underneath was the preferred option numerous times as a number of people didn't like seeing the unfinished underside of the sub.

In my own listening room, which is a largish room with frame construction on the first floor with a basement underneath, I initially installed an additional header under the floor joists with three support posts using a hydraulic house jack under the new header to slightly raise the floor so we could insert three support posts between the header and the concrete basement floor, and then let the jack down and removed it. That significantly stiffened the frame floor of the listening room and the problem with the downfiring woofer was reduced. However, it was only possible because there was an unfinished basement under the room. Another side benefit was that footfalls no longer affected the turntables on the top of the equipment racks, which I took as proof that there was originally too much floor flex before. The house was well built by construction standards using 2 X 12 inch floor joists on 16 inch centers, 3/4 inch underlay plywood on top of the joists, and 1inch solid wood flooring on top of the plywood. The room has a large thick area rug on top of all of that flooring.

As to the subwoofers I eventually graduated to, I now have the IRS Beta subwoofers (2 sealed towers with 4 X 12 inch woofers each) using feedback control thru a highly adjustable subwoofer controller plus separate class D amplifiers. The woofer towers are close to the front wall and facing the listening position. No more floor issues. I am also using a third small sealed and self powered subwoofer slightly to the side of and behind the listening position, and within a couple of feet of the rear wall. That third sub is the one I make fine adjustments on based on the differences between recordings. This room currently exhibits excellent and natural bass response at the listening position.

I agree with you that placing sealed subs close to room boundaries is effective, and respectfully disagree that aiming the sub's woofer at the floor is effective as IME it can lead to issues with most frame construction floors. Possibly you are using a stone decoupling plinth or absorption material under the down-firing woofer to resolve this?

 

[sigbergaudio]

and what happens when the volume of Air the driver needs to displace is not immediately available? (this is a rhetorical question)

Do you have some evidence for this?

It's basically the allison / SBIR effect, the closer the driver is to the wall, the further up in frequency dips move. Whether it was a problem to begin with depends on how far out on the floor the sub is located and how high it is crossed over.

 

[gnarly]

In that case the subs and/or the mains aren't properly decoupled.

haha...good try

most of my builds can also double for live sound ...stout as can be....