Ported Cabs vs Sealed

[BassAdder60]

What’s your preference and why ?

 

There seems to be more ported cabs around than sealed and they both have there places 

 

What do you like about both variants and why 

[grandad]

All my cabs I think have been ported and my combos too. The only exception is my TCE BG250-208 which is my small portable practice combo.  Can't really compare from my experience but most do seem to be ported. 

Edited December 19, 2021 by grandad

[Lozz196]

Of the sealed cabs I’ve used I found that I preferred the sound to the ported cabs I’ve used.

[BassAdder60]

I’ve had both over the years and the best was the sealed Ampeg 610 cab

 

More recently the Ampeg PF115LF which is rear ported but a very low bass cab and heavy 

 

Just trying the Fender Rumble v3 115 ported cab and I like what I hear. Is it down to ported and cab design perhaps ? Hard to describe but in layman’s terms it’s a fullness or roundness to the sound which some may prefer the mid punch tone of sealed smaller box cabs 

[itu]

Neither is superior, both can be designed well - and not so well. They are a bit different, but both are complicated to design.

[BassAdder60]

32 minutes ago, itu said:

Neither is superior, both can be designed well - and not so well. They are a bit different, but both are complicated to design.

I agree as it’s possible to have good and bad designs in most things.

I do think both designs up close have a different sound, maybe less so out front playing live. 
It does make it harder making the best choice as we seldom have the opportunity to try at volume in a store etc.

I guess some of us also like mid punch less lows and others like low boom and fullness without so much mid growl or we want both depending on EQ etc 

We have so much choice these days it’s a tough one choosing the right set up for a preferred sound and need 

[chris_b]

I think every cab I've had since the 80's has been ported. I don't really think about it.

 

If the cab sounds good enough porting isn't a question that springs to mind.

[Sparky Mark]

A generalisation is that sealed enclosures have a more contolled/attenuated low end response. It's a characteristic that can mean sealed cabs are a good partner with amps with a lower damping factor, such as valve amps. The most famous example being the Ampeg SVT and its 810.

[Bill Fitzmaurice]

9 hours ago, itu said:

Neither is superior, both can be designed well - and not so well. They are a bit different, but both are complicated to design.

Sealed designs are simple compared to ported. The advantage to sealed is that they're hard to mess up, so long as the drivers used have the right specs for sealed. It just so happens that the right specs for sealed are high Qts, which are what's usually found with inexpensive drivers, so if you're going to use an inexpensive driver just stick it in a sealed box and you're good to go. Ported cabs work best with lower Qts drivers, which also tend to be more expensive, so if you have a more expensive drive it probably needs to be in a well designed ported box for best results. Ported goes lower than sealed when done right. What you don't want to do is to put an inexpensive high Qts driver in a badly designed ported box, as the result will usually be a boom box. When you hear people complain about ported speakers being boomy it's usually because they had a cheap driver in a bad box.

Quote

A generalisation is that sealed enclosures have a more contolled/attenuated low end response. It's a characteristic that can mean sealed cabs are a good partner with amps with a lower damping factor, such as valve amps.

Like most generalizations it's not true. The Ampeg SVT, for instance, was made sealed because that's what gave the best results with the high Qts drivers that they used. They could have made it ported and probably would have if they were able to find low Qts 32 ohm drivers, but none were to be had in 1969.

Damping factor is a non-factor other than in extreme cases that are very rarely seen.

http://www.cartchunk.org/audiotopics/DampingFactor.pdf

[Twincam]

As a experiment I converted a little sealed practice combo, an Ibanez soundwave. To ported with the help of winisd and a new speaker. That was a few years ago.

 

Beforehand I felt the combo had a great neutral sound, which in my opinion, was the best I had heard in an inexpensive combo. Great for jazz. It just lacked any real authority. I also liked the fact it didn't rattle or have any funny resonance. 

I can't remember all the details but after porting, and the new speaker. It sounded not that different in its basic sound signature. Apart from it had better low end and the volume was maybe very slightly increased. There was limitations to the small box as to what I could actually achieve. 

Many bass and guitar players have plugged into the little combo and said how good it sounds. It's far better than my previous practice amp a fender rumble v3 1x12 100, not that was just boomy and also rattled badly. 

 

On another note. It's funny how in the early days some bass cabs were open backed. Just sealing them surely would of made a big difference.

 

 

 

[Bill Fitzmaurice]

The early bass cabs that were open backed might not have benefited from being sealed, as they used generic musical instrument drivers which were guitar oriented anyway. Besides, they could give a good tone, they just couldn't go loud. Play just about any Beach Boys recording and you're probably hearing Carol Kaye playing through an open back Fender Super Reverb.

[Downunderwonder]

My old Trace 1518 came with advice in the manual for the through grill tuning ports. ''Goes lower, but not as loud, with ports plugged''.

[Twincam]

10 minutes ago, Bill Fitzmaurice said:

The early bass cabs that were open backed might not have benefited from being sealed, as they used generic musical instrument drivers which were guitar oriented anyway. Besides, they could give a good tone, they just couldn't go loud. Play just about any Beach Boys recording and you're probably hearing Carol Kaye playing through an open back Fender Super Reverb.

 

Interesting. 

I had a open backed valve Wem dominator combo a few years back. 15w 1x15. It sounded fine for bass practice at home. And micd recording.

 

Wasn't very loud until paired with a guitar then was seriously loud! I believe the amp was the same as the guitar version, just the 1x15 was bass specific celestion g15m 50w 

[itu]

18 hours ago, Bill Fitzmaurice said:

Sealed designs are simple compared to ported. The advantage to sealed is that they're hard to mess up, so long as the drivers used have the right specs for sealed.

Simple compared to ported - yes, but not simple. I studied acoustics in the uni, and I do remember quite many issues that are too easy to meet if the designer is not sharp. Modern tools like WinISD surely help, but the basics have to be understood in the first phase. Shapes, volume, materials, leaks... I still want to build a lightweight cab in the future.

 

I do hate this trio, where everything is related:

cubic volume - efficiency - lowest reproducible f

[Phil Starr]

So the graph below is the predicted response of a 12" speaker in a 60litre box, the red line shows a ported cab and the blue line a sealed cab. Same driver same box. The first thing to see is that above 300hz the lines converge and pretty much the whole of the midrange and top end are going to be the same. Exactly as @Twincam discovered when they tried the experiment. Below 200 Hz and for a full two octaves the red line is higher showing that the ported cab is a lot louder and gives a lot more bass. There's an extra 6db at 50 Hz where the port is tuned. That's the same as if you moved from a 200W amp to an 800W amp, and more is better right? It's really hard for a designer to ignore this effect, when you go to try the speaker out in a showroom the ported cab is going to be louder and bassier and sales teams know that this is what sells. It is also what most customers want so why would a designer choose to withhold the extra bass? The sealed cab gives a -3db of 76 Hz and the ported -3db of 50 hz, hands up who will buy the 50Hz cab over the 76Hz cab?

 

OK now move into a gig. Put the cab on the floor and the bottom end gets a 3db boost, back against the wall another 3db. Now you start to notice something else. That sealed cab has a nice flat response that tails off slowly, the sealed cab has a sharp knee and lots of deep bass. The extra 3db makes up for the missing bass for the sealed cab and it sounds a little better. 3db of deep bass isn't so helpful for a cab which already has enough deep bass and it starts to sound boomy/muddy.  This is exactly what @BassAdder27  was describing in terms of mid-punch versus fullness or roundness. Extra bass isn't always good, you need to make decisions based on what sound you prefer and recognise that what works in one situation won't sit comfortably in the mix in another. 

 

Now there is quite a lot of over-simplification here. I've deliberately chosen a driver which will 'work' in both a sealed or ported cab and which is the sort of speaker you'll find in a lot of mid priced commercial cabs. I've also used the sealed cab size that gives the flattest response, that happens to give the nearly 2db peak for the ported cab. I could have easily changed drivers, porting and tuning to create a flat response ported cab. I've chosen to emphasize difference too but you are always going to get that extra bass from a ported cab all other things being equal. It's the sound coming out of the port that does that and the port does other stuff too. There's a bit of a generic difference between ported and sealed cabs but a good designer can create a good response from either sort of cab with the choice of driver and the careful matching of the cab

 

There's one other thing to think about too. We almost can't hear bass, not the deep stuff. Most of what we hear as bass is the second harmonic, 80-160Hz for a four string so -3db at 76Hz is more liveable with than you'd expect and on top of that what really makes the timbre of your bass is all up in the mid frequencies where the cab makes little difference.

 

[Lozz196]

Think that explanation illustrates nicely why I seem to prefer sealed cabs, cheers Phil

[BassAdder60]

That’s really helpful Phil thank you 

 

It does make sense and also introduces other factors that makes the cab sound different ie the room etc.

I recall the first time I tried my Ashdown Neo cabs with the band

 ( after setting what appeared a great sound at home ) only to discover I had very much less bottom end as I turned up the volume. The cabs were definitely not boomy ( in fact the opposite) and full of mids and very punchy. Even using the “ Shape Out” feature on the ABM600 still sounded good. The one thing personally I felt that was needed was more bass and of course you can add loads with EQ etc.

Im now experimenting with a 15” ported cab to see if I’ve either gone too far the other way and resulting in a boomy mess or I fill the room and band out nicely. 
The lesson I learnt is cabs react differently to the room or stage you put them on and the volume you push them with. How it’s ever possible to judge a cab in a music store is beyond me !! 

Edited December 20, 2021 by BassAdder27

[Bill Fitzmaurice]

16 hours ago, Phil Starr said:

OK now move into a gig. Put the cab on the floor and the bottom end gets a 3db boost, back against the wall another 3db.

Your chart is half-space, so it already shows response on the floor. Moving it close to the wall puts it in quarter-space, which adds as much as 6dB of axial sensitivity. It does so over a broad pass band, not just in the lows. Most speaker modeling software can't model the difference between different space loadings, but HornResp can. This shows the difference between quarter-space on the darker upper trace, and half-space in the lighter lower trace. You don't get just extra bass with wall loading, you get extra everything.

 

The effect is the same with ported and sealed cabs, so wall loading doesn't make a sealed cab work as well in the lows as a ported cab. It just makes both work better closer to the wall than away from it.

[Count Bassy]

6 hours ago, Bill Fitzmaurice said:

Your chart is half-space, so it already shows response on the floor. Moving it close to the wall puts it in quarter-space, which adds as much as 6dB of axial sensitivity. It does so over a broad pass band, not just in the lows. Most speaker modeling software can't model the difference between different space loadings, but HornResp can. This shows the difference between quarter-space on the darker upper trace, and half-space in the lighter lower trace. You don't get just extra bass with wall loading, you get extra everything.

 

The effect is the same with ported and sealed cabs, so wall loading doesn't make a sealed cab work as well in the lows as a ported cab. It just makes both work better closer to the wall than away from it.

Not an acoustic expert, but just looking at the graph: at 1KHz the boost is 92.5 to 95dB, ie 2.5dB, but at 100Hz its 97.5 to 103dB, so a boost of around 5.5dB, and at 60Hz you're getting over 5dB boost. So yes, you do a boost all over, but it does seem to be greater in the bass end.

 

Please correct me if I'm missing something.

 

** Corrected to 5dB - Thanks Barkin!

Edited December 21, 2021 by Count Bassy

[barkin]

1 hour ago, Count Bassy said:

at 60Hz you're getting over 10dB boost. 

 

Wanna borrow my glasses...?

[Bill Fitzmaurice]

The boost is greater in the lows. That's not the same as only in the lows.

[Count Bassy]

4 hours ago, barkin said:

Wanna borrow my glasses...?

 

I wondered if anyone would spot that 😝.

Well spotted, and thanks for pointing it out.

[Count Bassy]

3 hours ago, Bill Fitzmaurice said:

The boost is greater in the lows. That's not the same as only in the lows.

Yes, but the effect is that the basses become more prominent, which I think was the original point that someone made.

[Phil Starr]

Bill my aim here is to enlighten not to confuse, and as I always do I stated clearly that I had simplified things in my post.

 

I don't think anyone here wants technical nit-picking. I stand by the general principles of what was in the post. I was clear in saying "Now there is quite a lot of over-simplification here" You yourself have failed to mention that a practical speaker is rarely actually mounted flush with the wall but some distance in front of it leading to comb filtering issues so that the neat calculated response you put up is not a reflection of what would happen in practice. I'm sure you know this and offered a simple explanation that people would understand. 

 

 

 

[Bill Fitzmaurice]

There's a big difference between the 3dB sensitivity increase you said was realized from each boundary and the 6dB that's actually realized. You're not going to get any increase by putting a cab on the floor compared to your chart because your chart already reflects the result with floor placement. I didn't mention flush mounting because it's not pertinent to this discussion. Placement some distance in front of a wall does not lead to comb filtering. It does result in an Allison Effect response notch, which I could have put on that chart, but that would be making things more complicated than necessary for this particular thread. What matters as far as boundary loading is concerned is that it will not turn a well executed ported cab into a boom machine, nor will turn a thin sounding sealed cab into a low end monster. Most of the inherent characteristics of both will be maintained, but they'll be louder, which is seldom a bad thing. Just by being louder they'll seem to go lower, as that's part and parcel of how our hearing works.