Ported V Sealed

[Billy Apple]

Fight your ground for your opinions on ported or sealed cabs.

Which is tighter?

Which has more 'thump'?

Does it change tone?

Does one have more bass/mid/treble?

What differences does it really make?

How does the same driver react in sealed and ported cabs?

In a fight....6X10 sealed (eg, Matamp) or 2x12 ported (eg Barefaced)?

Which one is best for Metal?

What do you think?

[LukeFRC]

are you being serious?
Most those variables i'm sure could be designed into a cab whatever the porting situation, apart from "[font="helvetica, arial, sans-serif"][color="#282828"]How does the same driver react in sealed and ported cabs?" everything else is like asking "which is better precisions or jazz basses"...[/color][/font]

[Roland Rock]

I have a sealed 6x10. I wouldn't say that it changes the tone, rather the attack, or transient response. Punchy is a good description.
Ported cabs have more bass response, but I happily play dub and reggae on mine, and believe me, it has as much low end as you could want, if required.

I don't know why (I'm sure someone on here could explain) but a sealed cab seems to be an especially good match with a valve head.

Edited November 28, 2013 by Roland Rock

[Billy Apple]

[quote name='LukeFRC' timestamp='1385666937' post='2290978']
are you being serious?
Most those variables i'm sure could be designed into a cab whatever the porting situation, apart from "[font=helvetica, arial, sans-serif][color=#282828]How does the same driver react in sealed and ported cabs?" everything else is like asking "which is better precisions or jazz basses"...[/color][/font]
[/quote]

Well, that's easy, Precision's of course . But the question is, which do you prefer and why?

[LawrenceH]

I am always puzzled when I see people say that you can design a ported cab to give the LF response of a sealed cabinet, because of the inherent phase relationship of the port and driver around and below resonance where it has to transition to a 4th-order rolloff. Closest you can do as far as I understand it is to tune very low so the more dramatic effects on system phase are out of bandwidth. Audibility is argued but a lot of us subjectively prefer the sound of a sealed box or these deep-tuned ported cabs, despite the fact that they don't make the most of the woofer in terms of raw in-bandwidth output level.

In hi-fi, I also think mid-range leakage from ports can be a difficult issue to solve completely satisfactorily as well. For high power PA/bass, I think the cooling advantage offered by ports probably does translate to a real-world benefit.

Based on spec alone I'd take the Barefaced over the Matamp any day of the week...but that's because the Barefaced uses much better drivers (sorry but the Matamp ones are nothing special AFAIK). Plus, I'm not absolutely sure but since the Barefaced driver has extension to spare, I suspect these cabs are tuned unusually deep so minimising the disadvantages of a ported cab wrt transient response. The Matamp versus another more run-of-the-mill ported cab...a tougher fight, I suspect I'd prefer the sealed cab.

[Billy Apple]

I'm not saying the Matamp is in anyway a state of the art sealed cab. It was just the first one that came in to my head that has (roughly) the same dims as the Barefaced.

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1385671086' post='2291055']
I am always puzzled when I see people say that you can design a ported cab to give the LF response of a sealed cabinet,
[/quote]You can. I don't know why you'd want to, but it's not all that difficult, if the driver specs are amenable.
[quote]In hi-fi, I also think mid-range leakage from ports can be a difficult issue to solve completely satisfactorily as well. [/quote]I've never found it an issue at all.
[quote]I don't know why (I'm sure someone on here could explain) but a sealed cab seems to be an especially good match with a valve head. [/quote]Because the impedance peak of a sealed cab with high Q drivers tends to be much lower than the peaks of a vented cab with low Q drivers, and valves don't deal well with high impedance loads.
[quote]How does the same driver react in sealed and ported cabs?[/quote]Not all that well, as a driver that works best in a ported cab has a high EBP, that which works best sealed has a low EBP, so putting either into the other is a round hole/square peg situation.

Edited November 28, 2013 by Bill Fitzmaurice

[Guest]

EBP ?

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1385672538' post='2291085']
You can.
[/quote]

No, you really can't and someone with a quote about the laws of physics in their sig should be clear on this. The sum of the driver/port below resonance will be a 24dB/oct slope. Always. All you can do is play with the knee, and push the 2nd-4th order transition so low that the peak is outside the effective bandwidth of the cabinet. Which is good, and still offers worthwhile benefits over an equivalent sealed cab in terms of size (although this can easily be eaten up by port size/length requirements for high power operation) and subsonic excursion. But it's not actually the same.

[quote name='Bill Fitzmaurice' timestamp='1385672538' post='2291085']
I don't know why you'd want to, but it's not all that difficult, if the driver specs are amenable.
[/quote]

Because a lot of people like the sound of the transfer function of a sealed cab between, say, 0.5 and 0.7. If you're not concerned about cone excursion, then considering the sealed cab versus a (bandwidth-limited) identical ported cab, the former is extremely easy to build and avoids certain problems with port/room placement, port resonance and midrange leakage. These latter I'd agree can be made a very small problem, but a very small problem is still not as good as no problem, may as well keep it simple if it suits the application.

Edited November 28, 2013 by LawrenceH

[VTypeV4]

[quote name='kennyrodg' timestamp='1385675824' post='2291126']
EBP ?
[/quote]

Efficiency Bandwidth Product which is defined as Fs (free air resonace freq) divided by Qes (electrical Q)

[Guest]

Cheers for that bud,
any chance of examples of high and low EBP drivers or Fs figures that would demonstrate it.
Thanks again.

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1385676173' post='2291136']
The sum of the driver/port below resonance will be a 24dB/oct slope. Always.
[/quote]That doesn't mean one cannot realize the same result with vented and sealed, just that one must possess the necessary design skills to do so.

Edited November 28, 2013 by Bill Fitzmaurice

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1385678796' post='2291179']
That doesn't mean one cannot realize the same result with vented and sealed, just that one must possess the necessary design skills to do so.
[/quote]

Yes, it does mean exactly that. Unless the 'laws of physics' you so humbly equate yourself to are markedly different to everyone else's. You can get it the same in a limited bandwidth, which is what I said at the beginning. You can't get the final slope of a ported cab below resonance to roll off at 12dB/oct no matter how many magical beans you buy from mysterious old men you meet on the way to speaker markets.

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1385679616' post='2291203']
Yes, it does mean exactly that. Unless the 'laws of physics' you so humbly equate yourself to are markedly different to everyone else's. You can get it the same in a limited bandwidth, which is what I said at the beginning. You can't get the final slope of a ported cab below resonance to roll off at 12dB/oct no matter how many magical beans you buy from mysterious old men you meet on the way to speaker markets.
[/quote]This is a chart of the Ampeg SVT driver, ported in blue, sealed in red, in the same net volume. Of course the gross volume of the ported is larger, to account for the duct, but the increased sensitivity makes that worthwhile.



The ported does have a higher roll off slope below 30Hz, but that's hardly of any consequence. This also answers the OPs question regarding what the same driver may do sealed or ported, in this case with a driver that has a moderate EBP that allows it to function in both.

Edited November 28, 2013 by Bill Fitzmaurice

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1385679948' post='2291209']
This is a chart of the Ampeg SVT driver, ported in blue, sealed in red, in the same net volume. Of course the gross volume of the ported is larger, to account for the duct, but the increased sensitivity makes that worthwhile.

The ported does have a higher roll off slope below 30Hz, but that's hardly of any consequence.
[/quote]

Your own example is a good one for showing exactly what I'm talking about. Yes, the slope rolls off steeper below 30 just as physics says it must. With this particular example the increased sensitivity above that means the group delays between the two cabs will diverge at a much higher frequency ie the transient response of the ported cab will be poorer. The only way of getting it to perform equivalently, above 40-odd Hz, would be to reduce the cab volume. And you'd still see it peak abruptly below this.

Edited November 28, 2013 by LawrenceH

[Bill Fitzmaurice]

[quote name='LawrenceH' timestamp='1385681328' post='2291228']
Your own example is a good one for showing exactly what I'm talking about. Yes, the slope rolls off steeper below 30 just as physics says it must. [/quote] So? That being well below the passband it's moot.[quote] With this particular example the increased sensitivity above that means the group delays between the two cabs will diverge at a much higher frequency ie the transient response of the ported cab will be poorer. [/quote]In this particular case GD of the vented cab is significant only below 40Hz, so it is also moot. GD at 50Hz is 4 and 6ms respectively, putting both well below the threshold of audibility, and GD of the two above 100Hz is identical.

[BassTractor]

[quote name='LawrenceH' timestamp='1385676173' post='2291136']
No, you really can't and someone with a quote about the laws of physics in their sig should be clear on this.
[/quote]

Bloody nonsense!
I have a quote about the laws of physics in my sig, and I'm not clear on anything!

[LawrenceH]

[quote name='Bill Fitzmaurice' timestamp='1385683787' post='2291266']
So? That being well below the passband it's moot.In this particular case GD of the vented cab is significant only below 40Hz, so it is also moot. GD at 50Hz is 4 and 6ms respectively, putting both well below the threshold of audibility, and GD of the two above 100Hz is identical.
[/quote]

It's ok - if you like I can go back and edit my original post to make it look like I didn't say about the cab's bandwidth or raise the question of audibility and instead just made a sweeping inaccurate statement. Then you can edit yours to put in the caveat about the bandwidth and then pretend that you have been arguing the same thing all along rather than gradually backtracking. Let's pretend, eh? Then we can also pretend that your undefined threshold of audibility is the Last Word on the topic and it's not at all controversial. Then all will be safe in internetland and bassists the world over can breathe happy sighs of relief.

[Phil Starr]

[quote name='Billy Apple' timestamp='1385666411' post='2290971']
Fight your ground for your opinions on ported or sealed cabs.

Which is tighter?

Which has more 'thump'?

Does it change tone?


In a fight....6X10 sealed (eg, Matamp) or 2x12 ported (eg Barefaced)?

Which one is best for Metal?

What do you think?
[/quote]

Great question, there are differences some of which are down to the type of cab and some down to just differences due to the actual speaker in question. Now the physics isn't really helpful on the above. mainly because 'thump', 'tone' and 'tight' mean different things to each of us. I'm not a fan of metal but even my superficail listening tells me that metal bassists don't all sound the same, though big cabs seem to have the image needed


[quote name='Billy Apple' timestamp='1385666411' post='2290971']
Fight your ground for your opinions on ported or sealed cabs.

Which is tighter?

Which has more 'thump'?

Does one have more bass/mid/treble?

What differences does it really make?

How does the same driver react in sealed and ported cabs?

[/quote]

There are differences which Lawrence has talked about, They are all in the bass region so no, they don't make any difference to mid or treble. Yes in hi-fi speakers some midrange sound can be reflected off the back panel of the cab and come out through the port though this isn't really relevant to bass cabs as it isn't going to be noticed unless you are miking up in a strange place.

The main effect of the port is to give you extra output at the frequency around the ports tuning point, About 3dB or double the output which you can see clearly on Bill's graph, Most bass designers can't resist this 'free' extra bass so most modern style cabs are ported designs. Older cabs with walls of cheap drivers were filled with speakers that couldn't work in ported designs so tended to be sealed getting their extra bass from sheer muscle, a bit like American sports cars.

The other advantage of porting is that sealed cabs always raise the resonant frequency of the speaker so the bass output starts to fall from a higher starting point in a sealed cab compared to a ported cab depending upon which drivers you use. (it's a bit complex here but this holds true for most commercial cabs IMO)

There are disadvantages coming from the port though, below the resonant frequency of the cab the speaker unloads very quickly. The air in the port acts like a plug at high frequencies, like a tuned bass string at resonance and like a big open hole below resonance. This has lots of consequences because the cone flaps around under little control from anything. First of all it is likely to exceed its excursion limits and the power handling can be reduced to a tenth of its rated level as it starts to hammer against the back of the magnet. The bass output falls very rapidly in a ported cab (at 24 db/octave) so if the cab was tuned to 60Hz the bottom note of a 5 string might easily be 1/200th of the power of B an octave above. (you'd still hear plenty of harmonics, just not the fundamental tone) You also get problems with phase at these frequencies. If you are using a ported cab and want it ot go on working then you really need to cut all the bass below 40Hz or even higher with some designs

With the sealed cab the bass falls off at half the rate of a reflex cab at 12 dB/octave though it will do this from a higher point because of the raised resonant frequency. Because the cab is sealed it acts on the back of the cone and reduces the excursion at low frequencies, this means you can often use a little bass boost safely to bring the level up to that of a ported cab. At some point the ported cabs more quickly falling output will cross over the slowly falling output of the sealed cab. Bill gives one example where it crosses over below any bass note we play but there could be any number of examples where it is higher than this.

Sealed cabs can be designed easily to either give a big hump in frequency and a slightly woolly bass or a flat response or a really tight well damped bass simply by changing the size of the cab. This makes it easy to design in 'thump' or 'tight, fast bass'. You can do this with ported cabs too but I would say with less flexibility.

The other factor is room resonance, you can easily get an extra 6dB or more of bass by the sound being reflected off the floors and walls, I find myself cutting the bass more often than boosting it when I play live so a slow bass roll off might be something between a curse and a blessing.

It is hard for an engineer designing a speaker to turn down the advantages of the extra bass of a ported design and most sealed cabs have really cheap drivers in them so you aren't comparing like with like quite often. No-one I know of has taken the Barefaced approach of putting the best modern bass drivers into a well engineered lightweight sealed cab yet, though someone will correct me on that. I don't think there is anything intrinsically wrong with the idea though.

[Roland Rock]

[quote name='Phil Starr' timestamp='1385725058' post='2291509']


Great question, there are differences some of which are down to the type of cab and some down to just differences due to the actual speaker in question. Now the physics isn't really helpful on the above. mainly because 'thump', 'tone' and 'tight' mean different things to each of us. I'm not a fan of metal but even my superficail listening tells me that metal bassists don't all sound the same, though big cabs seem to have the image needed




There are differences which Lawrence has talked about, They are all in the bass region so no, they don't make any difference to mid or treble. Yes in hi-fi speakers some midrange sound can be reflected off the back panel of the cab and come out through the port though this isn't really relevant to bass cabs as it isn't going to be noticed unless you are miking up in a strange place.

The main effect of the port is to give you extra output at the frequency around the ports tuning point, About 3dB or double the output which you can see clearly on Bill's graph, Most bass designers can't resist this 'free' extra bass so most modern style cabs are ported designs. Older cabs with walls of cheap drivers were filled with speakers that couldn't work in ported designs so tended to be sealed getting their extra bass from sheer muscle, a bit like American sports cars.

The other advantage of porting is that sealed cabs always raise the resonant frequency of the speaker so the bass output starts to fall from a higher starting point in a sealed cab compared to a ported cab depending upon which drivers you use. (it's a bit complex here but this holds true for most commercial cabs IMO)

There are disadvantages coming from the port though, below the resonant frequency of the cab the speaker unloads very quickly. The air in the port acts like a plug at high frequencies, like a tuned bass string at resonance and like a big open hole below resonance. This has lots of consequences because the cone flaps around under little control from anything. First of all it is likely to exceed its excursion limits and the power handling can be reduced to a tenth of its rated level as it starts to hammer against the back of the magnet. The bass output falls very rapidly in a ported cab (at 24 db/octave) so if the cab was tuned to 60Hz the bottom note of a 5 string might easily be 1/200th of the power of B an octave above. (you'd still hear plenty of harmonics, just not the fundamental tone) You also get problems with phase at these frequencies. If you are using a ported cab and want it ot go on working then you really need to cut all the bass below 40Hz or even higher with some designs

With the sealed cab the bass falls off at half the rate of a reflex cab at 12 dB/octave though it will do this from a higher point because of the raised resonant frequency. Because the cab is sealed it acts on the back of the cone and reduces the excursion at low frequencies, this means you can often use a little bass boost safely to bring the level up to that of a ported cab. At some point the ported cabs more quickly falling output will cross over the slowly falling output of the sealed cab. Bill gives one example where it crosses over below any bass note we play but there could be any number of examples where it is higher than this.

Sealed cabs can be designed easily to either give a big hump in frequency and a slightly woolly bass or a flat response or a really tight well damped bass simply by changing the size of the cab. This makes it easy to design in 'thump' or 'tight, fast bass'. You can do this with ported cabs too but I would say with less flexibility.

The other factor is room resonance, you can easily get an extra 6dB or more of bass by the sound being reflected off the floors and walls, I find myself cutting the bass more often than boosting it when I play live so a slow bass roll off might be something between a curse and a blessing.

It is hard for an engineer designing a speaker to turn down the advantages of the extra bass of a ported design and most sealed cabs have really cheap drivers in them so you aren't comparing like with like quite often. No-one I know of has taken the Barefaced approach of putting the best modern bass drivers into a well engineered lightweight sealed cab yet, though someone will correct me on that. I don't think there is anything intrinsically wrong with the idea though.
[/quote]

Great info thanks! I have the Barefaced 6x10 sealed cab, but not sure exactly what drivers are in there

[VTypeV4]

[quote name='kennyrodg' timestamp='1385677661' post='2291162']
Cheers for that bud,
any chance of examples of high and low EBP drivers or Fs figures that would demonstrate it.
Thanks again.

[/quote]

The old Precision Devices PD1850 is a good example of a high EBP driver. These were (still are?) commonly used in heavy bass applications and work particularly well in folded horns where the acoustic loading on the driver can be heavy.

FS: 30Hz and Qes: 0.22 = an EBP of 136.

Whereras the Eminence has a much lower EBP designed to work in a vented enclosure. It has a lower motor strength too.

FS: 27 and Qes: 0.33 = an EBP of 84.

[Bill Fitzmaurice]

Related to the OPs original question is if you can get higher sensitivity ported than sealed while maintaining the same response why wouldn't you? This is why:



The blue trace is a ported ten with EBP 138, the black a sealed ten with EBP 80, both are 1.5cu ft cabs. At 50Hz, where demands on the amp and driver are the highest, the ported cab has 6dB higher sensitivity. That means it would take two of the sealed to match one of the ported. One reason one might prefer the sealed is if one doesn't care for the stronger low end of the ported. But that's why amps have all those knobs and sliders. Using those devices one can get the same response as sealed, with a major difference, that being headroom in the amp is increased while driver excursion is decreased by using EQ to reduce low frequency output. The other reason why one might prefer sealed is that the reduced amp headroom and increased excursion demands on the driver with sealed will result in a dirtier tone. If that's what you're after all well and good, but if not you should reconsider bias against ported.