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-Can you please discuss more about 'port-compression'?
I have the understanding that the port does 2 things. 1) It's TUNED to a certain frequency, and 2) it's for air intake/exhaust due to the driver displacement.
The port air-velocity should try to be minimized - or you'll hear 'chugging'. (110 ft/s or less?) You can reduce air-velocity with more vents - or larger diameter vents.
I've never seen 'port-compression' referenced.
Max port air speed will be at tuning, and the port needs to pass that without becoming to resistive, so it needs to be as large as possible to keep the PAS as low as possible. However, the large CSA of a port the longer it will need to be, so some manufacturers use the shortest port possible. When it tries to pass the max volume of air, the CSA will be too low and it will behave like a dynamic filter at port tune, reducing output at the highest levels, but not at lower levels so it still measures well at low levels. Manufacturers won't talk about it because it's their dirty little secret. I try to keep PAS below 15m/s.



Chuffing is more what happens when the air is in a fairly high impedance zone, in the port, and it comes to the open air, their is shear in the flow and this sound can become audible. Where that is and how bad depends upon the tuning and design of the port and box. This why many ports have flared ends, and note that because the port is bidirectional in flow, the intake (inside the enclosure) is also best flared.
 

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Ported and Horned works great but only for outdoors or in large rooms, and/or for people who don't mind being [email protected]

I've heard quad 16hz ported Full Marties.
I've also heard my own system (which is mostly all-sealed.)
My system wins easily...

Here's my stance on the topic, if I'm gonna drop >$20k on 32 subwoofers, I want ALL the frequencies, not just some of them! PERIOD! :)
I can easily hear 12hz, and I can feel 5hz easily (with a concrete floor and no butt shakers.)

You couldn't pay me to port all my subs (ok ok... maybe for $100k I'd re-consider it "temporarily", before reverting right back to an all-sealed design. :D)

The thing is: Ported doesn't scale well once go past about ~8 subs.
Who wants to deploy 32 ported subs and spend 5 figures doing that, taking up a barn of space, and still be [email protected]? (Answer: Nobody! ;))
Ported and Horned only works well for small quantities of woofers, or outdoors, or in a 200'x200'x50' Cinema / Barn (where 5hz is gonna be unpossible via conventional-methods.)

sealed CAN work in small spaces; and IB/sealed can also work if you want the least-rolloff and no port noise at ANY db!

It's a balance of budget, space and priorities.
Different strokes for different folks: 2000HP Lambo vs Armored Royce Limo.
One is just really-loud, the other gets you there while you eat some breakfast and without any holes... :p
 

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-Can you please discuss more about 'port-compression'?
I have the understanding that the port does 2 things. 1) It's TUNED to a certain frequency, and 2) it's for air intake/exhaust due to the driver displacement.
The port air-velocity should try to be minimized - or you'll hear 'chugging'. (110 ft/s or less?) You can reduce air-velocity with more vents - or larger diameter vents.
I've never seen 'port-compression' referenced.



-I could also use some insight regarding 'room-gain'.
My room is large and open, ...although the theater (big screen) is in a corner of the room - not the whole thing.
I have (0) knowledge on this, but seen it discussed a lot - and it seems important.
How do I understand this, and how does it impact sub-woofer designs?
Please use small words. : )


-My 14 cu ft ported design has an inherently flat response down to 16 hz (+/- 3db).
I am mostly new to DSP's. Is there any point in a DSP?
I understand them as 'digital equalizers' to custom set for unique rooms interactions. Yes?
Good/bad/unnecessary?


Thanks.
1. The port is not an exhaust, the tuning uses an air slug to achieve tuning. Essentially moving the air back and forth is what achieves the output. If this is restricted than the output is lowered requiring more power. If your port is too small it won't match the sims in WinISD as it doesn't predict port compression. What you want is to keep the port msec down below a desired range, if its high you'll hear it.

Builders can also take advantage of smaller ports by building based off of planned power usage. Take for example your build can handle 2500watts but your compression is obscene, how ever at 800watts (your planned amps RMS rating) you'll be well below port compression. That doesn't really leave you with the ability to upgrade but then again you'll have to ask yourself if you do plan to eventually upgrade.

2. & 3. Both of these play into each other, where you have room gain you also have dips and spikes. DSP is necessary to tame these or you'll have some wicked booms.
 

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Wow replied yesterday to the wrong thread :D
So here is my point of view.

With the UM18, the issue is that it needs a BIG box. The box needs to be soo big you can fit 2 sealed UM18 in the same space. I don't think a single 18 in a vented box will be better at SPL than 2x18s even at the tuning frequencies.
Keep in mind that sealed really benefits from room gain.
Sealed is easy to build, takes a small space (or takes the same space with 2x the drivers -> 2x more surface area).
No need to worry about port velocity and keeping the port resonance at check.
With this new invention called the BOSS and all of its variations you don't even need anything under 18hz, unless you want to "feel" the bass while you hear your hours rattle.
Another plus is the group delay, or the so called how fast a sub is. Everyone says sealed is always faster than vented. I haven't heard subs at this caliber in a vented box so i can't speak for myself. The only thing i can tell you is that when i watch a movie i can't remove my smile from my face.

I just finished building 2xUM18 in sealed boxes. I didn't need to boost the low end i had to reduce massive peaks (14db at 30hz), at the end i'm flat down to 18hz. My subs are placed at the absolute worst place in the room and the room is super bad (it's 50% windows from floor to ceiling). I've done 110db at 20hz at the current tuning. I still need to see how much SPL i can do. Looking at the cone movement i think i can squeeze another 3db of each driver. Can't find time to make some videos =/

If i could place them in the corners it would be even louder with less cone movement. But maybe, there is a very very small chance i can fit 1 or 2 more subs somewhere in the room in the future.

EDIT: so my response is a day late. I want to add something. When you model a sub in winISD for example, the response you see is in open space (technically an anechoic chamber), it will greatly differ when you place the sub in YOUR room. Speakers behave substantially different in a room, based on it's size, what materials were used to build the room, and the interior, furniture, carpets, ect. Also the elevation of the house changes the frequency response, because sound travels at different speeds depending on how dense the air is. That's why you can change those variable if you are gonna build speakers for a hours placed at 3000m above sea level.
 

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Wow replied yesterday to the wrong thread :D

So here is my point of view.



With the UM18, the issue is that it needs a BIG box. The box needs to be soo big you can fit 2 sealed UM18 in the same space. I don't think a single 18 in a vented box will be better at SPL than 2x18s even at the tuning frequencies.

Keep in mind that sealed really benefits from room gain.
The modeled output of the ported enclosure shows a nearly 10db gain at 20hz.

By adding a 2nd equal sub, you can expect only 3db gain.
So according to that you would need at least between 3-4 sealed UM18 to equal the single ported around the port tune.

Of course you can boost the low end in the sealed boxes, but I don't think you could boost enough even with two subs to come close to a single ported enclosure around tuning.

The advantage there is placing the subs in different spots will even out the peaks and dips though.

Room gain will affect ported subs equally as sealed, so you will get an even bigger boost to the low end in a smaller room.
However after building a sealed UM18 I was surprised how little room gain I got in a 1800ish cu ft room.




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The modeled output of the ported enclosure shows a nearly 10db gain at 20hz.

By adding a 2nd equal sub, you can expect only 3db gain.
So according to that you would need at least between 3-4 sealed UM18 to equal the single ported around the port tune.

Of course you can boost the low end in the sealed boxes, but I don't think you could boost enough even with two subs to come close to a single ported enclosure around tuning.

The advantage there is placing the subs in different spots will even out the peaks and dips though.

Room gain will affect ported subs equally as sealed, so you will get an even bigger boost to the low end in a smaller room.
However after building a sealed UM18 I was surprised how little room gain I got in a 1800ish cu ft room.




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Did you measure the entire room or only the MLP? Realistically you should be seeing a pretty massive amount of room gain if you're in a 12x14 room, or is it an open room?

I still think the bigger advantage of sealed subs is the slope, ported starts to rise in distortion fast post tuning and unless you are boosting the low end on a sealed you won't be seeing too high distortion there.
 

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Did you measure the entire room or only the MLP? Realistically you should be seeing a pretty massive amount of room gain if you're in a 12x14 room, or is it an open room?



I still think the bigger advantage of sealed subs is the slope, ported starts to rise in distortion fast post tuning and unless you are boosting the low end on a sealed you won't be seeing too high distortion there.
Yes, I measured several different positions in the living room, and everything below 40 Hertz remained pretty much unchanged, only 1-2db difference. The uncorrected frequency response was actually very disappointing.
Basically looks like a pyramid peaking at 40 Hertz.

The biggest difference moving it around was actually in the mid bass region, from around 70-100hz.

I found this was critical because the um18 is not a good mid bass producer. in fact there was such a huge drop off in the mid bass in certain positions, my receiver refused to apply any room correction until I moved it into the corner facing the wall, which boosted the mid-bass by about 6db.

I have a large 8 by 10 foot opening on the left into the dining room, and a hallway opening on the front right side. I think it's mainly the openings that kill the room gain for me.

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Yes, I measured several different positions in the living room, and everything below 40 Hertz remained pretty much unchanged, only 1-2db difference. The uncorrected frequency response was actually very disappointing.
Basically looks like a pyramid peaking at 40 Hertz.

The biggest difference moving it around was actually in the mid bass region, from around 70-100hz.

I found this was critical because the um18 is not a good mid bass producer. in fact there was such a huge drop off in the mid bass in certain positions, my receiver refused to apply any room correction until I moved it into the corner facing the wall, which boosted the mid-bass by about 6db.

I have a large 8 by 10 foot opening on the left into the dining room, and a hallway opening on the front right side. I think it's mainly the openings that kill the room gain for me.

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Interesting the room correction had safeguards, I know of an individual that ruined his SVS sub because room correction put his sub at 10db hot in the midbass. Pretty sure he was using a Yamaha.

I agree, I think your opening is ruining your room gain, my room is also open and I see very few and small peaks with my subs, which are 2x NSW6021's tuned to 17hz.
 

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Everyone says sealed is always faster than vented.

No, "everyone" doesn't say that. Only the misinformed that continue repeating an old myth. That myth was based on old poorly designed subs with weak motor strength that didn't control the cone properly and sounded boomy/sloppy. A properly built/designed ported sub will sound just as "fast" as a sealed one.
 

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Oh boy. This thread is devolving, like most sealed vs ported threads do. Why is it that every time this sort of discussion happens, everyone who has sealed subs has to repeat the same old myths, misconceptions, and pseudo-science to justify that they have sealed subs in their systems and they work well and they are happy with them?

For the record, I have both alignments actively in my system, and I have no bias either way. They are what they are, with their strengths and weaknesses.

With the UM18, the issue is that it needs a BIG box. The box needs to be soo big you can fit 2 sealed UM18 in the same space.
That's not really a UM18 thing, it's a ported box thing. The bigger a ported box is, the bigger port it can support for a given max port length and tune, the more output it can give around tune at a reasonable port velocity. But that's the strength of a ported box, you get tons of "free" output with the same driver and same power, all it does it take up more space. Sure, you can fit 2 sealed UM18 in the same space, but then you need to buy 2 drivers and twice as much amp. That's the trade-off. Both are perfectly reasonable options with their own pros and cons.

I don't think a single 18 in a vented box will be better at SPL than 2x18s even at the tuning frequencies.
Actually, it's very easy to design a vented box that crushes its 2x sealed equivalent. My subs, for example, are more like 9x sealed at tune.

Keep in mind that sealed really benefits from room gain.
As others have said, all subs do.

With this new invention called the BOSS and all of its variations you don't even need anything under 18hz, unless you want to "feel" the bass while you hear your hours rattle.
I just finished building 2xUM18 in sealed boxes. I didn't need to boost the low end i had to reduce massive peaks (14db at 30hz), at the end i'm flat down to 18hz.
You can't tell anyone what they "need", and are you drawing the line at 18Hz for any particular reason, or just because your system happens to be flat to 18Hz? Having TR doesn't change the fact that SPL
 

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The modeled output of the ported enclosure shows a nearly 10db gain at 20hz.

By adding a 2nd equal sub, you can expect only 3db gain.
So according to that you would need at least between 3-4 sealed UM18 to equal the single ported around the port tune.
If you split the 1w to both subs then yes, you get only 3db of gain. But if each sub is getting 1w instead of 0.5w, you get 6db of gain. So double the cone area +3db, and double the watts another +3db. So you can expect around 6db more over a single sub, this is ofcourse if they are placed in the same spot. You can do this easy in winISD.

One project is 1 sub at 1000w, the second project is 2 subs at 2000w, double the box volume used in the first sub. Go to the SPL chart no the transfer function one and see what is calculated.
Both vented and sealed have the same SPL at 20hz.
The vented has 6db more at 15hz. But because we have 6db from 20hz and above over the vented box, for ex at 40hz the vented should do 116db, the 2x sealed should 121db. Lower those 121 to 116, we just lowered from 2000w to 500w (250w each). Then we can apply 6db boost at 15hz and we still can't reach the simulated SPL of the vented box.
But again this is in free air space, not in a room. I wish i could have a second um18 in a vented box to do some real world in room measurements.

My "room" is actually the living and kitchen combined and it's relatively big. If i open the door for outside, i get 3db more output at 18-20hz without changing the the higher frequencies, which is nuts one door can do. 18hz flat is what i wanted because BOSS exists now. I really don't know why anyone would want anything lower than 17-18hz especially when BOSS exists.

For the box size.
I'm using litters.
The optimal vented box for the according to winISD is 613L without the port. I can lower that to 500L and still get the low end. My um18s are in a 164L sealed boxes. 500 / 164 = *3.048.... So i should be able to make 3 um18s sealed in the same spot where a single vented wlil take in it's optimal box. Downside is that you need more amps and watts.
 

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But again this is in free air space, not in a room. I wish i could have a second um18 in a vented box to do some real world in room measurements.
FYI, it all translates to the room the same.

I really don't know why anyone would want anything lower than 17-18hz
Have you ever heard/felt good, clean, impactful SPL at 17Hz, 16Hz, 15Hz, 14Hz, 13Hz, 12Hz, etc?

But again, if someone told me they didn't care about output below 17-18Hz I would absolutely recommend they go ported over sealed. It becomes far more likely that they will have enough output down to that 17/18Hz point that they want with only two subs or however many they want.
 

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If you split the 1w to both subs then yes, you get only 3db of gain. But if each sub is getting 1w instead of 0.5w, you get 6db of gain.

Thanks for the clarification / correction there.
So it seems it would take about 3 sealed subs with 3x power to roughly equal a single, large ported enclosure running at x power, at the tuning frequency.

I still feel like a large ported enclosure tuned low like 17hz, accompanied with a nice boss platform wood be the ultimate bang for buck in low frequency response.

And to get into single digits that's really my only option, I cannot fit 3-18 subs in my living room, not even close, and I imagine many others can't either.

Pretty much everyone has unused space under their couch though!




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Oh boy. This thread is devolving, like most sealed vs ported threads do. Why is it that every time this sort of discussion happens, everyone who has sealed subs has to repeat the same old myths, misconceptions, and pseudo-science to justify that they have sealed subs in their systems and they work well and they are happy with them?
I don't know :D, but hey this time i can actually join in with my own opinion. 2 weeks ago i finish my first build.

That's not really a UM18 thing, it's a ported box thing. The bigger a ported box is, the bigger port it can support for a given max port length and tune, the more output it can give around tune at a reasonable port velocity. But that's the strength of a ported box, you get tons of "free" output with the same driver and same power, all it does it take up more space. Sure, you can fit 2 sealed UM18 in the same space, but then you need to buy 2 drivers and twice as much amp. That's the trade-off. Both are perfectly reasonable options with their own pros and cons.
I totally agree, the only problem is that i can't simulate a smaller vented box in winisd with a desired flat response. For ex a 300L box with a 15hz tune, is always has this weird slope, changing the port size doesn't change the response, only the port tuning does, cuz we can't simulate that a guess.

You can't tell anyone what they "need", and are you drawing the line at 18Hz for any particular reason, or just because your system happens to be flat to 18Hz? Having TR doesn't change the fact that SPL
 

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FYI, it all translates to the room the same.
Have you ever heard/felt good, clean, impactful SPL at 17Hz, 16Hz, 15Hz, 14Hz, 13Hz, 12Hz, etc?
I wrote the above comment before reading your previous post, and now i answered your previous post and it got messy. This time delay between reading and typing in forums...
Now you make me rethink if i could fit 2 ported enclosures in the living room. Sadly i don't have a free room to make a dedicated HT.
 

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I totally agree, the only problem is that i can't simulate a smaller vented box in winisd with a desired flat response. For ex a 300L box with a 15hz tune, is always has this weird slope, changing the port size doesn't change the response, only the port tuning does, cuz we can't simulate that a guess.
Does it look like this?

 

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Does it look like this?
Yes, see how at 15ish hz it's at 111db and at 30hz it's around 117db. 6db sound like a lot of difference. To me it would sound like the bass would be lacking just because the higher frequencies would be louder. I wonder in this situation do you lower everything above to 111db to be flat or ?

Also sorry to OP about taking your thread over :D
 

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That's not really a UM18 thing, it's a ported box thing.
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.


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Yes, see how at 15ish hz it's at 111db and at 30hz it's around 117db. 6db sound like a lot of difference. To me it would sound like the bass would be lacking just because the higher frequencies would be louder. I wonder in this situation do you lower everything above to 111db to be flat or ?
Do the same comparison with the sealed response, then. ;)

This is what I meant when I said they both translate to the room the same way. You are holding the ported response to a different standard than the sealed response, but they both will get the same room gain.
 

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Do the same comparison with the sealed response, then. ;)

This is what I meant when I said they both translate to the room the same way. You are holding the ported response to a different standard than the sealed response, but they both will get the same room gain.
Do you think i would benefit from this, if i replace my 164l boxes with 300l ones ported at 15hz with some eq ?

It's almost midnight here so i will have to leave you. It was a nice chat :).
 
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