Ported vs dual apposed subs

[TankTop5]

Just out of curiosity which will have more output? Looks to me that dual apposed have more output from several manufacturers, Arendal 2V, Rythmic G25HP, KEF KC92 and others the flagship high output subs all seem to be dual apposed rather than ported. I was looking at PSA (out of boredom and curiosity) and the lack of data led me to check forums. Most people suggested the TV42 Ipal would have almost 3 times the output of the S42 Ipal. Seems like dual apposed have better transient response and group delay but do they generally have more or less output than a ported sub with the same cone area?

 

[ryanosaur]

Just out of curiosity which will have more output? Looks to me that dual apposed have more output from several manufacturers, Arendal 2V, Rythmic G25HP, KEF KC92 and others the flagship high output subs all seem to be dual apposed rather than ported. I was looking at PSA (out of boredom and curiosity) and the lack of data led me to check forums. Most people suggested the TV42 Ipal would have almost 3 times the output of the S42 Ipal. Seems like dual apposed have better transient response and group delay but do they generally have more or less output than a ported sub with the same cone area?

A dual driver sub, including dual opposed, should have greater output than any single Driver version using the same Driver.
Ideally, these Subs will have the Drivers connected in Parallel to achieve that.
Comparing across different brands and models can be difficult as different designs will likely have different focus.
Dual Opposed can be Sealed or Ported.

As for Group Delay or transient response, any competently designed sub should show no issues here. Sealed Subs naturally have an edge over Ported in GD, but most Subs we’ve seen reviewed lately show that Ported Subs are capable of clearing that metric.

So… the real answer is that it depends, but any Dual Driver configuration should have increased output over the a single matching Driver.

 

[TankTop5]

A dual driver sub, including dual opposed, should have greater output than any single Driver version using the same Driver.
Ideally, these Subs will have the Drivers connected in Parallel to achieve that.
Comparing across different brands and models can be difficult as different designs will likely have different focus.
Dual Opposed can be Sealed or Ported.

As for Group Delay or transient response, any competently designed sub should show no issues here. Sealed Subs naturally have an edge over Ported in GD, but most Subs we’ve seen reviewed lately show that Ported Subs are capable of clearing that metric.

So… the real answer is that it depends, but any Dual Driver configuration should have increased output over the a single matching Driver.

Some manufacturers it seems even two driver ported are inferior to a sealed dual apposed sub though. That’s what has me asking. Rythmik for example dropped their dual 15” ported in favor of the apposed sub and claimed greater output

 

[TLS Guy]

Some manufacturers it seems even two driver ported are inferior to a sealed dual apposed sub though. That’s what has me asking. Rythmik for example dropped their dual 15” ported in favor of the apposed sub and claimed greater output

How do you know they are superior? I keep telling members that you DO NOT judge a sub just by looking at F3 and raw output.

The issue is that a sealed sub is inefficient as F3 will be high and so you have to boost power 12 db per octave below F3, and that is a lot. That means a robust motor system, power compression, and likely higher distortion.

The next issue is that some subs boost below Fs of the driver. In my view that should never be done, but is, and the distortion just goes off the clock. The darn admen though will boast their F3 and output.

The other issue is that sub manufacturers tend to spec. high Q drivers. The reason is to get a lower native F3 in a small box, so there is less boost required. This produces bass but again there is sacrifice of quality. Obviously I have not heard every sub going, but I have heard plenty and I'm yet to hear a commercial sub I could really live with long term.

The nice thing about a ported sub is that you can't play this game. You will not drive it below F3 whatever you do. However there is a tendency to higher Q, but you can't play this game too far, as they will end up with a sub size that will negatively impact sales. Also they do tend to go for extended bass alignments to give the admen that lower F3 number, when in fact a slightly smaller cabinet and higher F3 would deliver higher quality bass.

So, I really favor ported over sealed, as you know it is what it is. The only reason for going sealed is size. I don't care how big my speakers are though.

So, it is only for social convenience that it appears bass takes a lot of power. It does not. My bass sections are as efficient as the rest of the system.
So they don't take a lot of power, and the drivers are assisted over a much wider frequency range, and the lines couple much more efficiently to the room. There is nothing like the bass quality delivered by well designed transmission lines. You just can't accomplish it any other way.

So I strongly encourage members to design and build subs, you will quickly find that you will beat what the market has to offer.

 

[ryanosaur]

It's pretty much impossible to really comment on without knowing the parameters of the Driver... With the T/S Parameters, one can model ideal enclosure and experiment with options to weigh the tradeoffs that are part of Speaker design.

Last I looked, Rythmik is still using their servos rather than DSP, but the Servos act in the same manner that DSP can in order to control Driver behavior outside of ideal performance. This won't change the fact that the Driver will still be better served in a specific size and type of cabinet. Likewise, it won't change how the designer chooses to treat the Driver with DSP (or use of the Servos) to then boost a Driver in a small sealed cabinet to get a lower flatter response.

This is usually what happens in small sealed Dual-Opposed builds. If you look at any of the builds for Stereo Integrity Drivers, for example, Nick recommends using a Linkwitz Transform which boosts the lower end of the Driver response to get that low end up and flat. Without using a powerful Amp and a Driver designed to take that power, you couldn't achieve what he does.

The same is true with the Pro Drivers that PSA is using. Those B&C Drivers are designed to take a lot of Power. But when you push a Driver below its resonant Frequency, other things start happening. Those B&C Drivers, and other Pro Drivers like Eminence and LaVoce which are used in DIY Subs, also usually have very stiff Suspensions to control the Driver when its being pushed with all that power.

Balancing Stroke/Excursion, Motor strength, and the ability to absorb power/dissipate heat is what the Extreme Sub world is all about. How loud and how low is the game.

What you commented on about the PSA Subs is a harsh reality. You never see folk taking their Subs out for Distortion measurements. I've voiced my concern about PSA several times and the fact that there are no true measurement suites for any meaningful performance metric.

Data-Bass was the only real spot to do this, but Ricci stopped doing that years ago. They used to keep the measurements available but I've heard those might have gone away, too.

 

[TankTop5]

This sounds like a case for multiple large overpowered subs running well below their max output regardless of design so long as it’s competent.

 

[ryanosaur]

This sounds like a case for multiple large overpowered subs running well below their max output regardless of design so long as it’s competent.

This is the thing that many HT enthusiasts end up looking at.
Ultimately it’s about headroom.

Find subs that deliver the Extension you need and use multiples to cancel room modes and increase output.

If you need to create a 2- way Bass system, this is less ideal, but doable if done smartly, and you will usually need fewer Mid-Bass modules as there are many options that are super efficient in that range.

Watch some of the Bass-Hedz on AVSF and they will have 2-4 each 24” Subs for extension, and then a few Mid-Bass Subs for the slam. I’ve seen guys running 2-3 Devastators which are allegedly violent in that Mid-Bass range but cr@p below 20 Hz.

Anyway.
Back to your point…
Find the Sub that does what you need and want. You need 18Hz, cool: get 3-4 that can do that comfortably and in a small room you are probably good. Maybe get 6 to really boost the SPL by co-locating or stacking a few.
You use less power per Sub and each unit is more likely to stay linear in it’s performance.

Its when you want single digit extension and need to set a house curve for 20 Hz output at 125+ dB that you get into trouble!!!

 

[lovinthehd]

It's pretty much impossible to really comment on without knowing the parameters of the Driver... With the T/S Parameters, one can model ideal enclosure and experiment with options to weigh the tradeoffs that are part of Speaker design.

Last I looked, Rythmik is still using their servos rather than DSP, but the Servos act in the same manner that DSP can in order to control Driver behavior outside of ideal performance. This won't change the fact that the Driver will still be better served in a specific size and type of cabinet. Likewise, it won't change how the designer chooses to treat the Driver with DSP (or use of the Servos) to then boost a Driver in a small sealed cabinet to get a lower flatter response.

This is usually what happens in small sealed Dual-Opposed builds. If you look at any of the builds for Stereo Integrity Drivers, for example, Nick recommends using a Linkwitz Transform which boosts the lower end of the Driver response to get that low end up and flat. Without using a powerful Amp and a Driver designed to take that power, you couldn't achieve what he does.

The same is true with the Pro Drivers that PSA is using. Those B&C Drivers are designed to take a lot of Power. But when you push a Driver below its resonant Frequency, other things start happening. Those B&C Drivers, and other Pro Drivers like Eminence and LaVoce which are used in DIY Subs, also usually have very stiff Suspensions to control the Driver when its being pushed with all that power.

Balancing Stroke/Excursion, Motor strength, and the ability to absorb power/dissipate heat is what the Extreme Sub world is all about. How loud and how low is the game.

What you commented on about the PSA Subs is a harsh reality. You never see folk taking their Subs out for Distortion measurements. I've voiced my concern about PSA several times and the fact that there are no true measurement suites for any meaningful performance metric.

Data-Bass was the only real spot to do this, but Ricci stopped doing that years ago. They used to keep the measurements available but I've heard those might have gone away, too.

The data-bass site has been somewhat revived. Here's an article on measuring dual opposed subs https://data-bass.com/#/articles/5cb4eb62079a580004e73249?_k=xyaon7

I've not seen that dual opposed subs are particularly superior, altho my Epik Empire is still doing fine, altho I really wanted a Submersive at the time....

 

[shadyJ]

The only advantage that dual-opposed driver configurations have is they eliminate rocking motion of the enclosure. Other than that, there is no advantage over a typical sealed sub.

 

[TankTop5]

This is the thing that many HT enthusiasts end up looking at.
Ultimately it’s about headroom.

Find subs that deliver the Extension you need and use multiples to cancel room modes and increase output.

If you need to create a 2- way Bass system, this is less ideal, but doable if done smartly, and you will usually need fewer Mid-Bass modules as there are many options that are super efficient in that range.

Watch some of the Bass-Hedz on AVSF and they will have 2-4 each 24” Subs for extension, and then a few Mid-Bass Subs for the slam. I’ve seen guys running 2-3 Devastators which are allegedly violent in that Mid-Bass range but cr@p below 20 Hz.

Anyway.
Back to your point…
Find the Sub that does what you need and want. You need 18Hz, cool: get 3-4 that can do that comfortably and in a small room you are probably good. Maybe get 6 to really boost the SPL by co-locating or stacking a few.
You use less power per Sub and each unit is more likely to stay linear in it’s performance.

Its when you want single digit extension and need to set a house curve for 20 Hz output at 125+ dB that you get into trouble!!!

My room isn’t particularly large and I’ve been finding SB3000’s for about $1500 a pair. Who knows maybe someday I’ll have 4 stacks of 2. Think that’ll be enough for most humans, won’t do much below 16hz though.

 

[TLS Guy]

This sounds like a case for multiple large overpowered subs running well below their max output regardless of design so long as it’s competent.

No it does not.

It makes the case for competent total system design.

Once you add subs, then you essentially have a three or four way system with an active bass system.

This business of mid bass modules should not be required. That is an attempt to make up for poor speaker design.

Competently designed speakers should have enough resources in the power bands of all musical genres. The problem is that a lot do not.

There is only one mid range driver for instance that can really handle the power without using two, and that is the ATC midrange driver. Dynaudio used to make one, which was very similar.

A design with one 4" or 5" mid is going to run out of "gas" where it counts.

Having subs dotted about solves some problems and causes others.

A double bass covers a huge frequency range, and its sound needs to emanate coherently, or it will not sound right.

 

[oniiz86]

The only advantage that dual-opposed driver configurations have is they eliminate rocking motion of the enclosure. Other than that, there is no advantage over a typical sealed sub.

Surely that can't be the only advantage, I thought it having an additional woofer would provide an additional 3dB-6dB of output, so much greater headroom & does it eliminate even-order harmonic distortion similar to M&K's push-pull configuration claims that even-order harmonic distortion is eliminated entirely or is it merely reduced?

I've heard that claims of even-order harmonic distortion are much harder to discern & much less objectionable anyway, its odd-order harmonic distortion that is easier to discern & much more audible.

 

[shadyJ]

Surely that can't be the only advantage, I thought it having an additional woofer would provide an additional 3dB-6dB of output, so much greater headroom & does it eliminate even-order harmonic distortion similar to M&K's push-pull configuration claims that even-order harmonic distortion is eliminated entirely or is it merely reduced?

I've heard that claims of even-order harmonic distortion are much harder to discern & much less objectionable anyway, its odd-order harmonic distortion that is easier to discern & much more audible.

The additional woofer can add more SPL, but it needs to be given double the enclosure space of the first woofer as well as amplifier power. You are basically just taking two sealed subs, sticking them together, and removing the shared panel. If you just put an additional woofer onto an existing sub enclosure and amp, you choke its enclosure space which raises the resonant frequency and kills the deep bass as well as overall linearity. The amp also needs to handle the additional load unless you give it its own amp circuit.

Typical dual opposed does not reduce any distortion products. Push-pull does reduce even-order distortion, but that is a special case.

Even-order distortion is more difficult to perceive and is thus less offensive. Since it is closer in frequency to the fundamental, it is more likely to be masked.

 

[Oddball]

Probably does not matter in the greater scheme of things, but Arendal 1723 2V is ported - they have 2S that is sealed. I do find 2V better in all aspects than eg. SVS PC 4000 that has same size driver (albeit 1), same wattage amp and cost couple of hundred less. But for large rooms don't expect wonders from that sub or any sub in that class. You might need couple of them and you need to be lucky to get decent below 15hz output from these relatively small drivers. Good thing is that you can stack them up as they don't move at all due to their design. Due to weight I would still not stack more than 2.

 

[MrBoat]

Many people don't completely grasp just how low 40-30hz for music actually is, with trying to aim for lowest frequencies possible. I often hear requirements included in the event that they come across the lowest pipe organ frequencies, as few and far between as those occur. I mean, to aim for that criteria, I would almost have to entirely listen to nothing but pipe organ music, instead of the two or 3 notes in those ranges I might happen across less frequently than winning lottery tickets.

I ended up high passing my sealed subs at 30hz just to see if it hurt anything while adding a bit of protection in the event I get rambunctious, and the cabinets are only tuned to the mid 30s. I never lowered it after, mostly because I forgot that I had set a HPF. I listen to quite a bit of electronic music and ho-lee-chip. . . it will rattle the fillings in your teeth. I still feel frequencies down to 20hz with whatever small amount that rolls past the high pass and my room would not be able to stand any more than that. But the bass frequencies in the music I listen to is a perfect blend to my ears and other senses. Possibly the highest fidelity bass I have ever experienced in a residential space.

I would not compromise what performance I am getting for lower extension than what I have. I have not felt shortchanged. Music that contains well recorded bass is audibly flawless. As it is, it more than adequately and cleanly picks up the lowest notes on say, contrabassoon, which is an effect I find very pleasing.

It ended up sounding so good, in fact, that it prompted me to post a thread on favorite basslines in music. I was about to try a lower reaching sealed design and never needed to. As someone who will DIY build speakers and subs just out of curiosity and boredom, this says a lot.

 

[TLS Guy]

Many people don't completely grasp just how low 40-30hz for music actually is, with trying to aim for lowest frequencies possible. I often hear requirements included in the event that they come across the lowest pipe organ frequencies, as few and far between as those occur. I mean, to aim for that criteria, I would almost have to entirely listen to nothing but pipe organ music, instead of the two or 3 notes in those ranges I might happen across less frequently than winning lottery tickets.

I ended up high passing my sealed subs at 30hz just to see if it hurt anything while adding a bit of protection in the event I get rambunctious, and the cabinets are only tuned to the mid 30s. I never lowered it after, mostly because I forgot that I had set a HPF. I listen to quite a bit of electronic music and ho-lee-chip. . . it will rattle the fillings in your teeth. I still feel frequencies down to 20hz with whatever small amount that rolls past the high pass and my room would not be able to stand any more than that. But the bass frequencies in the music I listen to is a perfect blend to my ears and other senses. Possibly the highest fidelity bass I have ever experienced in a residential space.

I would not compromise what performance I am getting for lower extension than what I have. I have not felt shortchanged. Music that contains well recorded bass is audibly flawless. As it is, it more than adequately and cleanly picks up the lowest notes on say, contrabassoon, which is an effect I find very pleasing.

It ended up sounding so good, in fact, that it prompted me to post a thread on favorite basslines in music. I was about to try a lower reaching sealed design and never needed to. As someone who will DIY build speakers and subs just out of curiosity and boredom, this says a lot.

You are absolutely correct, Only pipe organs and synths go down to 20 Hz and below. The lowest note of the 32' stop on a pipe organ has a fundamental of 16 Hz.

I am a pipe organ enthusiast. What I can tell you is that with room gian a system with an F3 in the mid to low 20 Hz range, will reproduce a 32' stop just fine.

In videos you can see the organist run his feet up and down the pedal board.

I can tell in my AV room, that the whole pedal board is reproduced evenly, with no loss of output down to the last note.

My in wall system with a 10" driver in a TL has slight diminution of output with the last note on the pedal board, the rest are very even.

I just don't think it is necessary to engineer F3s below the lower 20 Hz range.

Remember F3 is not a brick wall and there is output below F3. Depending on design roll off will likely be 24 db per octave below F3. A sealed could theoretically be 12 db. but usually they have to be high passed to prevent driver damage.

My TLs, roll off at 12 db per octave, but do not have to be high passed as they do not suddenly decouple from the loading like reflex porting does.

I can't see the point of engineering for Hollywood's highly artificial effects. But for me its all about the music.

 

[TLS Guy]

The additional woofer can add more SPL, but it needs to be given double the enclosure space of the first woofer as well as amplifier power. You are basically just taking two sealed subs, sticking them together, and removing the shared panel. If you just put an additional woofer onto an existing sub enclosure and amp, you choke its enclosure space which raises the resonant frequency and kills the deep bass as well as overall linearity. The amp also needs to handle the additional load unless you give it its own amp circuit.

Typical dual opposed does not reduce any distortion products. Push-pull does reduce even-order distortion, but that is a special case.

Even-order distortion is more difficult to perceive and is thus less offensive. Since it is closer in frequency to the fundamental, it is more likely to be masked.

You are absolutely correct there is no free lunch. When you use two drivers, then Vas is double, and so enclosure volume is doubled for the same tuning.
Isobaric is an exception, as Vas is halved. This does not halve enclosure volume as you have to add the volume of the tunnel. Sensitivity loses 3 db compared to one driver and 6 db compared to two drivers without isobaric loading. So their is absolutely no free lunch to be had in speaker design.