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As an owner of the 4 cuft cabinet and the 18 inch driver, I can say that I am quite happy with sealed.


I have done in-room testing on a number of subs, and find the computers do rough estimates at best. The room is a much bigger factor in my case for overall response than cabinet design (cu ft and ported/sealed).


I have a pretty good sound meter that has a 'flat' setting. (A or C weighting is useless for sub measurements.) I get response that is down only a very few db (3 to 6) to 8 Hz out of that sealed Dayton Audio combination.



Toss your computer design programs, build a good sealed enclosure with a good driver, run Audyssey (or equivalent) then get out your level meter good down to at least 20Hz and fire up your signal generator connected to the line input and do some 5Hz to 100Hz measurements.
If you actually find you have a meaningful gradual dropoff starting somewhere about 35 to 50Hz, there is such as circuit as a Linkwitz equalizer that will flatten the response of a sealed enclosure and maintain those single digit bass responses. Or go for one of the new DSP plate amps (also available from dayton audio) that have equalizers built in. You can have a sine wave response equal to vented and maintain the great transient response and controlled phase delay at the lower frequencies.



I have run vented enclosures before. I prefer sealed because, IMO, transient response and attack time seems much tighter.
By the way, passive radiator designs can do great at sine wave reproduction at low frequencies. However, with events such as drums, etc, the signal may have come and gone before all that passive cone mass and enclosure air volume even gets going. That is the price paid for 'better' low frequency numbers on the spec sheet.
 

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I'm going to say that it's both. Generally ported enclosures need to be larger than sealed to get a decent response, however the sub comes into play as well.

Some subs do better in smaller ported enclosures than others.

The um18 needs a larger ported enclosure than average to perform well.
But none of that changes the main point I was trying to make, that the port is what really matters, and the port size is limited by max length for a given enclosure size and tune. While it looks like what you're saying matters significantly at first glance, port velocity is the ultimate equalizer.

I'll show you what I mean with a specific example. I'll use an SQL-15 vs a UM18, both in a small 6.5cf box tuned at 15Hz, and I'll use a huge for that box 6" port at 47.5" long to give as much of the benefit of the doubt here as possible.



Here we see the stronger driver, the SQL-15, appears to be able to push the port to output an additional 2dB at tune, 111dB vs 109dB. But in order to push the port to 111dB, it would take a port velocity of >30 m/s. Even the 109dB that the UM18 pushes the port to is at > 24 m/s. So while it appears the SQL-15 has an advantage, that evaporates as soon as we account for port velocity.

I've modeled tons of subs over the years, and the fact is, pretty much any capable driver like the UM18 is able to push almost any port to its limits. So the bottleneck down low on a ported sub is pretty much always the port, not the driver, and the only way to get past that is to make the box bigger (or tune higher, but I'm assuming we're at the desired tune and don't want to increase it).

Going to an extreme example, I'll change the tune to 20Hz and change to an even more huge for this box 8" port @ 46" long. The SQL-15 still shows a 2dB advantage at tune, but maybe port velocities are finally getting low enough where it might be able to retain some of that. Not really, it's still over 20 m/s, and if we go with 20 m/s max, its advantage is only 1dB. I think this is a good example that even at the extremes, it's not much of a difference between drivers because the port is almost always the bottleneck.
 

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“It simple really just spend 3 times more on drivers and amps and deliver 3x the power and you will still have less output at tune.”

Also most people when they get a second and third sub they usually don’t mutually couple (I know it isn’t the proper term) them so they don’t get that +9db, also if you mutually couple them you lose the multi sub benefits (less room modes).
 

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Toss your computer design programs, build a good sealed enclosure with a good driver, run Audyssey (or equivalent) then get out your level meter good down to at least 20Hz and fire up your signal generator connected to the line input and do some 5Hz to 100Hz measurements.
I don't use a computer, I design subs on my abacus. Here's my model of a "good sealed enclosure with a good driver". It doesn't support Audyssey yet, so please don't mind the unEQed response.



If you actually find you have a meaningful gradual dropoff starting somewhere about 35 to 50Hz, there is such as circuit as a Linkwitz equalizer that will flatten the response of a sealed enclosure and maintain those single digit bass responses. Or go for one of the new DSP plate amps (also available from dayton audio) that have equalizers built in. You can have a sine wave response equal to vented and maintain the great transient response and controlled phase delay at the lower frequencies.

I have run vented enclosures before. I prefer sealed because, IMO, transient response and attack time seems much tighter.
But, but...won't that Linkwitz equalizer circuit and DSP plate amp equalizer increase my group delay and turn my wonderful magical sealed transient response (that I can't hear) into a slow, jumbled mess (that I still can't hear)?
 

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Do you think i would benefit from this, if i replace my 164l boxes with 300l ones ported at 15hz with some eq ?
Yes, you would likely end up flat to 12 or 13Hz without any low-end boost.

Here's a comparison between your current box in yellow and your proposed ported box in red. Max port velocity on this ported response is a reasonable 20 m/s.

If you're interested in building something PM me and we can work through a design together.

 

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Put simply:
Ported and Horned are louder/more efficient because they use both sides of the driver. The horn using most of it and the ported using some of it. High-order is somewhere in-between. Needs HPF/phase etc.

Where as with sealed the back is constantly fighting the front, causing undershoot and overhang and some loss of efficiency.

PR is somewhere in-between those two. Delayed/hanging mass/spring issues. Needs HPF/phase etc.

With IB the backside is literally thrown out the window, discarded; the side effect of doing that is a lack of excursion control which ultimately limits the acceptable input power before bottoming out, which further limits the >40hz SPL which is entirely power-limited for subwoofers. Really flat but you have to deploy a lot of cones to bring up the mid-bass to acceptable levels.

There is no free lunch...
You are either restricting the bandwidth with box tricks, or spreading the power out too thinly, or fighting the back pressure. Or some combo there-of.

But the solution to all of those boxes is the same: deploy more cones/amps until the SPL is so-loud that you CAN'T use it all. (Problem solved! :p)
[Or the WAF/Cops-limit. Whichever comes first... :D]
 

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Discussion Starter #47 (Edited)
Ahem....

Looks like a fun topic!


Ok, here's what I got so far.
In my head, and per the WinISD outputs, ported cabinets produce a sizeable advantage of SPL-output below 40 hz - when compared to sealed.
To compensate for sealed 'characteristics' - it requires (more amplifier, more speakers, or both) - to equal the same SPL output of a ported configuration.
Sealed is effective in some situations - and lots of people are extremely happy with their UM18-22 sealed configuration (as per countless threads across countless forums).


It appears the main deciding factor for ported versus sealed is purely cabinet size preference.
Neither configuration is perfect, and both has it's challenges to design around.
But looking solely at (SPL vs Frequency) - which is generally the entire purpose - ported configuration certainly has large advantage below 40 hz.




I'm still confused regarding the ports, and I'm still oversimplifying it in my mind.
So far - the only rule of thumb I've gleaned is stay within 50-65 ft/s (15-20 m/s) for max port speed - to avoid 'port compression'. (I'll have to read up on this topic)
I understand port tuning is a combination of (diameter and length) to match the desired frequency. To maintain lower port speeds, you need more port cross-section area.
But aron7 has repeatedly stated you need a 48" (ish) long tube, and use length to determine diameter. ?!?! I'm confused. Did I get that wrong?

I could go with x4 ports (4") which would reduce velocity to 55 ft/s. (I was planning on PVC tubing. Is that ok? or is there a better approach?)
Or I could go with rectangular port, like the built-in ports in the marty builds. Plenty of 'area' there to slow the velocity.
For my given configuration (UM18-22, 14 cu ft cabinet, 16.5-hz tuned ports) - what would you recommend?
 

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Ahem....

Looks like a fun topic!


Ok, here's what I got so far.
In my head, and per the WinISD outputs, ported cabinets produce a sizeable advantage of SPL-output below 40 hz - when compared to sealed.
To compensate for sealed 'characteristics' - it requires (more amplifier, more speakers, or both) - to equal the same SPL output of a ported configuration.
Sealed is effective in some situations - and lots of people are extremely happy with their UM18-22 sealed configuration (as per countless threads across countless forums).


It appears the main deciding factor for ported versus sealed is purely cabinet size preference.
Neither configuration is perfect, and both has it's challenges to design around.
But looking solely at (SPL vs Frequency) - which is generally the entire purpose - ported configuration certainly has large advantage below 40 hz.




I'm still confused regarding the ports, and I'm still oversimplifying it in my mind.
So far - the only rule of thumb I've gleaned is stay within 50-65 ft/s (15-20 m/s) for max port speed - to avoid 'port compression'. (I'll have to read up on this topic)
I understand port tuning is a combination of (diameter and length) to match the desired frequency. To maintain lower port speeds, you need more port cross-section area.
But aron7 has repeatedly stated you need a 48" (ish) long tube, and use length to determine diameter. ?!?! I'm confused. Did I get that wrong?

I could go with x4 ports (4") which would reduce velocity to 55 ft/s. (I was planning on PVC tubing. Is that ok? or is there a better approach?)
Or I could go with rectangular port, like the built-in ports in the marty builds. Plenty of 'area' there to slow the velocity.
For my given configuration (UM18-22, 14 cu ft cabinet, 16.5-hz tuned ports) - what would you recommend?

I will for sure say that the rectangle ports are easier to build but I’d recommend going with circular. They are better than square ports. With that said I have rectangular and the system is fine. When I rebuild mine I’ll build my ports out of sonotube.

If you stay under 20 msec you should t hear any chuffing but people get away with more too. I’d recommend going lower than what I did (28msec at max output).


Sent from my iPhone using Tapatalk
 

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Pjackso


Of course, each sub design has its tradeoffs, and some designs are just better for particular situations. At one end of the spectrum, bass SPL contests in open parking lots clearly demand ported or passive radiator designs for maximum db per watt. Or open air concert venues as an example.



Presuming you are in a room rather than outdoors, and have something like Audyssey for a room cal, you can cal your ported sub as open port and see how it sounds, then temporarily cover/plug the ports and cal the system as a sealed enclosure..

You get to choose which works best for your source material.
 

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It appears the main deciding factor for ported versus sealed is purely cabinet size preference.
Neither configuration is perfect, and both has it's challenges to design around.
Yes, here's a summary of the most relevant pros and cons of each...

Sealed

Pros:
Smaller boxes
Single-digit extension possible with enough subs

Cons:
More expensive to hit desired output levels
Less output/headroom than ported


Ported

Pros:
Cheaper to hit desired output levels
More output/headroom than sealed

Cons:
Bigger boxes
Steep rolloff below tune


I'm still confused regarding the ports, and I'm still oversimplifying it in my mind.
So far - the only rule of thumb I've gleaned is stay within 50-65 ft/s (15-20 m/s) for max port speed - to avoid 'port compression'. (I'll have to read up on this topic)
Think of port compression as what happens as the port starts reaching its limits. Before that point, if we increase the signal level by 1dB we get 1dB additional output. Once the port starts compressing that 1:1 relationship starts to diminish and gets gradually worse and worse. I use 20 m/s as a rule of thumb in my designs. I looked at multiple tests of ported subs on d-b and modeled equivalent boxes and checked what port velocities it took to hit the max output levels measured, and 20 m/s was very close. This doesn't mean you should avoid all designs that show velocities exceeding 20 m/s, just don't expect to actually get the output the model is showing beyond that.

I understand port tuning is a combination of (diameter and length) to match the desired frequency. To maintain lower port speeds, you need more port cross-section area.
But aron7 has repeatedly stated you need a 48" (ish) long tube, and use length to determine diameter. ?!?! I'm confused. Did I get that wrong?
You don't need a 48" long port. Pick any port length that is acceptable to you. As an example to illustrate what I'm saying about the relationship between length and area, let's model a ported box with some port size, length, and resulting tune. I'll use the model I used yesterday in a previous post, 6.5cf and 15Hz tune. We can use a 4" port @ 20" long to hit this tune in that size box, but port velocity will be crazy high at 48 m/s. We can keep the same tune and make the port bigger by making the port longer. For example, a 6" port @ 47.5" long. Port velocity drops to a much more reasonable 21 m/s. We could potentially go even longer, but first port resonance will become an issue. This is why I say, decide on the max port length you're comfortable with as far as first port resonance, and then use all of that to maximize port area for a given desired volume and tune.

I could go with x4 ports (4") which would reduce velocity to 55 ft/s. (I was planning on PVC tubing. Is that ok? or is there a better approach?)
Or I could go with rectangular port, like the built-in ports in the marty builds. Plenty of 'area' there to slow the velocity.
For my given configuration (UM18-22, 14 cu ft cabinet, 16.5-hz tuned ports) - what would you recommend?
Slot ports are the worst, as they have the smallest dimension being the slot height, yet they are still used on many subs with success, so it's not a deal-breaker by any means. Round ports are best, but they can be tricky to make really long with bends. I really like square ports as a middle-ground that captures most of the benefit of round ports over slot, while maintaining the ease of building them into the walls of the box and making easy bends to hit the desired length.
 

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I really appreciate that this thread was created as I have been asking myself this same question. I was thinking about going ported, but the $300 freight shipping for the the roundover martycube puts it out my price range. Looks like I will be going sealed and add more subs if needed.
 

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How do people normally measure SPL in room?

I'm trying to decide if I want to add a Marty cube to go with my Mini Marty or Go dual 8cu FT Cubes in a fairly small dedicated room, drivers are UM18-22. I tried running a 20Hz -10dB tone from REW and measured it with my sound meter in DBC, got to just over 100dB before some sort of distortion kicked in so I backed off (Not sure if it is room, cabinet or cone/amp).
 

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Oh you sure got me good!

Ill be more specific.

The ported box with a um18 will win in SPL output at every *frequency* that really matters, over the sealed.
The modeled response demonstrates that.
They are equal at about 11 Hertz.
Above that the ported has more output.

I understand there are other considerations, I was strictly talking frequency response.

I said one option is adding tactile to supplement ported subs, and it is. If that's not your preference that's fine. Many sealed subs or running nearfield is not an option for many, including myself.

It doesn't make sense to me to load a room with many sealed subs and immense amounts of power when you can replace that with a single ported sub and some tactile response.

Maybe it makes sense for you but not for me, and not for most other people.

The OP is asking about a single sub, and in a larger room, sealed subs placed anywhere EXCEPT nearfield is going to yield completely inadequate performance.

Sent from my Pixel 3a XL using Tapatalk
Hard to get a smooth room response with a single sub in a room. And can be hard to fit multiple large subs in a small room.
 
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