Differences on ported and sealed subs

[shadyJ]

Perhaps I should have said "consistent levels of bass". Or I could have used the term "flat response" over a greater portion of the sub-bass and bass range.

https://www.teachmeaudio.com/mixing/techniques/audio-spectrum/

I'd like to learn more about why you say that ported/sealed views are outmoded because the predominant views here, and on other forums, as as follows:

A flat response is necessary for accurate sound reproduction, which is what music lovers typically seek.

A response favoring high levels of very low bass is what movie buffs typically seek.

Maybe some movie buffs like tons of bass, and sometimes that can be fun, but someone who wants to take film as an artform seriously would strive to reproduce what the artist intended as closely as possible. If you want to listen to movies like how they are supposed to be heard, you should try to get a flat response. It's not going to bother anyone to have Transformers part 18 with the LFE jacked up by 10 dB, but that isn't how I would want to watch a normal movie. In the end, the reproduction of film or music should be treated the same.

 

[GrimSurfer]

Maybe some movie buffs like tons of bass, and sometimes that can be fun, but someone who wants to take film as an artform seriously would strive to reproduce what the artist intended as closely as possible. If you want to listen to movies like how they are supposed to be heard, you should try to get a flat response. It's not going to bother anyone to have Transformers part 18 with the LFE jacked up by 10 dB, but that isn't how I would want to watch a normal movie. In the end, the reproduction of film or music should be treated the same.

If only the movie industry thought the same way.

The sound of explosions, jets, helicopters, pistols, rifles, howitzers etc. sound much different in real life (my experience, having spent 35 years in the military) than the way they are portrayed movies... or movie theatres (which is what people are trying to emulate in HT setups).

 

[ryanosaur]

What’s a pair of shoes?

Shoes = Hsu. Williams got his propeller beanie on, I think.

 

[KEW]

Here is SVS's treatment of the question of sealed vs ported:
https://www.svsound.com/blogs/svs/75367747-sealed-vs-ported

One of my biggest take-aways is this graph which shows the anechoic FR of the SB2000 and what typical room gain does to the response (blue - flattens it down to the low teens):

So if we look at the typical anechoically flat response of a ported sub (PB3000 - purple line below) we see that the ~8dB of room gain at 20Hz would add a rather atrocious spike in the low 20Hz region!
Because of this, SVS offers a sealed mode for their better ported subwoofers (yellow line below). This is much more in line with a sealed sub's FR. Hsu is good about offering this type of tuning for their ported subwoofers being the first (I believe) major ID company to offer plugs and EQ options on their ported subs.

You can get the general idea from the graph above, but it did not link well. Here is the actual page with the chart:
https://www.svsound.com/products/pb-3000



PS: In so many ways, SVS seems to reflect a "best practices" standard of information and customer services, but I have to comment on how poor this linked PB3000 chart is by not carrying the horizontal and vertical lines across the chart so you can read it with some precision! The chart they use for showing the effect of room gain for the PB2000 (the first one I posted above) is so much easier to read! It seems like they are going out of their way to obscure the information needed to compare subwoofers!

PPS: The chart for the PB3000 marginally works when I am editing, but gives a failed link when I actually post it. Unless someone knows how to fix it, I am leaving things as they are with the link to SVS for the graph!

 

[Alex2507]

multiple bass sources are generally better than one for bass smoothness.

The exceptions would be what you call 'ambitious' subs, as in really expensive ... and probably sealed ... maybe dual driver ... able to take gobs of power and driven by a humungoid eq'ed amp.

 

[shadyJ]

Here is SVS's treatment of the question of sealed vs ported:
https://www.svsound.com/blogs/svs/75367747-sealed-vs-ported

One of my biggest take-aways is this graph which shows the anechoic FR of the SB2000 and what typical room gain does to the response (blue - flattens it down to the low teens):

You would need a pretty small room to get that kind of room gain. And even with that type of gain, you don't want to push a sealed sub too hard in deep bass because they quickly run out of excursion down there. I can see your point about the response shape, but sealed just doesn't have a lot of deep bass headroom, even in small rooms that get lots of low-frequency gain.

 

[KEW]

You would need a pretty small room to get that kind of room gain. And even with that type of gain, you don't want to push a sealed sub too hard in deep bass because they quickly run out of excursion down there. I can see your point about the response shape, but sealed just doesn't have a lot of deep bass headroom, even in small rooms that get lots of low-frequency gain.

All I have to go on for room size is SVS's text referencing the chart:

Below is a graph showing the SVS SB-2000 quasi-anechoic frequency response compared to the in-room frequency response with 7 dB/octave of room gain starting at 40 Hz (common for a small to mid-size enclosed room).

So you are saying "pretty small" and they are saying "small to mid-size enclosed room", that leaves a lor of uncertainty.
Then we also often have comments on acoustics where the author will consider any residential room small because they are thinking in terms of theaters and performance venues!
I wish room size comments were generally more specific!

@shadyJ , we can also generally reduce room gain by putting the subs in the middle of the room (like a near-field position) and increase room-gain by putting the subs against walls and (moreso) in corners, correct?

 

[Irvrobinson]

The exceptions would be what you call 'ambitious' subs, as in really expensive ... and probably sealed ... maybe dual driver ... able to take gobs of power and driven by a humungoid eq'ed amp.

I use an 18" sealed sub, and multiple bass sources are still better, at least in my room.

 

[shadyJ]

@shadyJ , we can also generally reduce room gain by putting the subs in the middle of the room (like a near-field position) and increase room-gain by putting the subs against walls and (moreso) in corners, correct?

Placing the subs next to a wall or corner will produce more boundary gain, which basically just changes the response in room- depending on the room (size and dimensions, etc). It won't affect pressure vessel gain which is what boosts lower frequencies but not higher frequencies. Pressure vessel gain is a matter of room size vs frequency wavelength. But room modes will take a toll on all of this, so who knows where the dips and peaks occur in the response in a normal domestic room. It's hard to make generalizations when modes can mangle the response so badly.

 

[Steelers252006]

The exceptions would be what you call 'ambitious' subs, as in really expensive ... and probably sealed ... maybe dual driver ... able to take gobs of power and driven by a humungoid eq'ed amp.

Which brings me full circle....one SVSPB16 over dual lots of everything else then?

 

[William Lemmerhirt]

What’s a pair of shoes?

Shoes = Hsu. Williams got his propeller beanie on, I think.

Yep. Ryan wins. HSU is Dr. HSU’s last name and is pronounced shoe.

 

[ryanosaur]

Which brings me full circle....one SVSPB16 over dual lots of everything else then?

no.

I use an 18" sealed sub, and multiple bass sources are still better, at least in my room.

Irv has it... even with an 18"sub, multiple LF sources are better.

I get it it, I would love to have 16 Ultras or a double Mariana, or a 24" Funk... but my 2 X-13s create better in-room bass than any 1 of those will. (yes, this is a generalization, or simplification...)

2 Hsu VTF15Hmk2 will do the same for you! (As an example.)

 

[William Lemmerhirt]

You would need a pretty small room to get that kind of room gain. And even with that type of gain, you don't want to push a sealed sub too hard in deep bass because they quickly run out of excursion down there. I can see your point about the response shape, but sealed just doesn't have a lot of deep bass headroom, even in small rooms that get lots of low-frequency gain.

I agree. I’ve used the sb2k in a variety of spaces and it’s just not that suited for lfe greatness. Even in a smaller room you can tell it’s working just a little too hard, despite what the graph says. It also lacks the efficiency down low to be effective unless the volume goes up. It is very smooth and does sound great with everything except really low content. I also think room gain is overstated and people underestimate sometimes how much power and excursion it takes sealed subs to do the same job.

 

[ryanosaur]

I get it it, I would love to have 16 Ultras or a double Mariana, or a 24" Funk... but my 2 X-13s create better in-room bass than any 1 of those will. (yes, this is a generalization, or simplification...)

2 Hsu VTF15Hmk2 will do the same for you! (As an example.)

Meant to add, @Steelers252006 :
Please don't misunderstand... its your money and system. if the 16Ultra is what you want, then that is your choice. I, and no one else here is going to presume to make or limit your choice! When you ask for guidance, and help understanding, we will give that! Based on what you've said, Danzilla, as well as many of us here have urged you along the path of multiple smaller subs... not that 15" is so drastically smaller than the 16Ultra... because our collective experience tells us that the multiple approach will perform very well!

Hope that makes sense!

Cheers!

 

[Alex2507]

.one SVSPB16 over dual lots of everything else then?

I'm usually a dual ported vote. Even room response at the expense of spl that you're not gonna use anyway.

 

[shadyJ]

Which brings me full circle....one SVSPB16 over dual lots of everything else then?

That wouldn't be my first choice. Two subs can get you a flatter response overall, and equal it in output for the most part. It's a great sub, but its size and weight is no joke.

 

[KEW]

I also think room gain is overstated and people underestimate sometimes how much power and excursion it takes sealed subs to do the same job.

If you are familiar with CEA2010 charts, there here are DataBass measurements that show the effect of moving this sub into Josh Ricci's room and measuring from the LP (which is a penalty on SPL, right. These charts are for the PSA XS15se, which I consider a good, but far from special subwoofer. It retailed for $800 and I think I got my pair for $1350 or $675 each.
Without room-gain, the low end is 88.9dB at 12.5 Hz.
With room-gain, the low end is 101.5dB at 10Hz!
You can also see that distortion has decreased, so you can't very well argue that this driver is being worked extra hard to produce these low frequencies

So how much power and excursion is required? 550W is nothing special for a sealed subwoofer and this is no stout JL Audio driver! This modest sealed sub accomplishes this feat at well below $1000! The point I am making is it does not require some super hardware or the driver to work any harder to do it, it is just free gain!

PS, In the past, I remember seeing some information involving the size of Ricci's listening room where these measurements were taken. I cannot find it now, but I do remember it was a decent sized room, not a small bedroom.
I am rather surprised not to see any dramatic nulls or nodes, but I guess Ricci knows the spot to place a single sub for good response at the LP!

 

[GrimSurfer]

Definitely two subs.

 

[KEW]

Which brings me full circle....one SVSPB16 over dual lots of everything else then?

Theorhetically, you can locate your sub to support your listening position with a good balance. However, two subs will even the sound out to provide a good balance at multiple positions.
Unfortunately, there is typically only something like 2 to 5 positions where your room layout would really allow you to place a sub, Whether an ideal location is included among those positions won't be know until you do it! So multiple subs using the best of those limited positions will do a lot to get you good even bass.
However, if you happen to be able to position your sub in an optimal location for your LP and if you don't plan to entertain in your room or nobody else cares much about SQ, you may realize no benefit from a second sub.
Most people don't qualify on those two points (or don't want to gamble on it); however, @Steve81 is the only knowledgeable subwoofer guy I know (there may be others, but I don't know about there systems) who has gone the single sub route with a Funk 21.0LX!

 

[shadyJ]

If you are familiar with CEA2010 charts, there here are DataBass measurements that show the effect of moving this sub into Josh Ricci's room and measuring from the LP (which is a penalty on SPL, right. These charts are for the PSA XS15se, which I consider a good, but far from special subwoofer. It retailed for $800 and I think I got my pair for $1350 or $675 each.
Without room-gain, the low end is 88.9dB at 12.5 Hz.
With room-gain, the low end is 101.5dB at 10Hz!
You can also see that distortion has decreased, so you can't very well argue that this driver is being worked extra hard to produce these low frequencies

I wouldn't bring discussion of distortion into this too much. Compared to groundplane measurements, the way distortion behaves in room is very complex. At many frequencies it can be a lot less as a percentage, but at others it can be much more.

We also have to keep in mind that It takes a lot more SPL in deep frequencies for the extension to be worthwhile. Sure a single 10" sealed sub can get a flat response down to 10 Hz in-room, but it doesn't make a difference if its deep bass output runs out of gas before it hits anything that can be humanly sensed. It is for this and other reasons that I generally don't advise people to buy sealed subs with expectations of room gain to deliver deep bass, unless they know for a fact that their room does do this, and the sub has enough displacement to make a real difference in that range.