Discussion in 'Amps and Cabs [BG]' started by jazztonebass, Apr 14, 2014.
How do these cab designs differ sonically?
How they differ sonically is all dependent on the design of each individual cab and it varies so wildly that there are no generalizations you can make.
Go try out some different cabs in a band context. When you find a cab you like you will know. Sometimes it is a combination of head and cab (or cabs) that does the trick.
Although there are many exceptions, some generalizations can be made. Watt for watt, ported cabs will give you more low end. Most sealed cabs have a tighter feel to them. A ported cab should be designed so that the lows from the port are synced with the sound coming from the front of the driver, but many don't quite pull it off. All IMO etc.
What they all said above. A ported cab will typically be louder and lower than it's sealed counterpart, but more boomy. A sealed cab will be tighter sounding, at the expense of efficiency and low end extension. You need to throw the power to sealed boxes, while a ported box will do more with less power, generally speaking.
I own some decent sealed and ported cabinets - a pair of Ampeg SVT210AV and a single fearful 12/6. Both are nice examples of the strengths of their respective designs.
The Ampeg cabinets have a voice that can't be eq'd into the fearful - there's a bit of compression, plenty of low mids and a wonderful responsiveness that keeps a speedy line intact. The bottom end is a bit soft, fine on a four string, less fun with a five. That soft bottom works great with an un mic'd bass drum.
The fearful isn't at all compressed, and the B string just comes to life in comparison. I find ported designs a little slower sounding than a sealed cabinet, they have plenty of articulation and slam, just not as much as my sealed cabinets. If I've got the fearful in full roar the kick has to mic'd to keep up.
Both work, and work well. What it comes down to for me is my mood and what sort of PA we are dealing with. The one thing I haven't tried is to mic the sealed cabinets into a PA.
In a nutshell, with all things equal - ported cabs can usually deliver a little more bottom end than sealed cabs.
Sealed cabs roll off the bottom end a bit more gradually than ported cabs, at the expense of starting the downward slope at a higher frequency.
Some will say that you should use a sealed cab with tube amps, but this by no means a rule. Lots of tube amps especially in years past actually came with ported cabs.
Ported cabs also can sound very, very different from each other. My Sunn 2000S 2x15 and the Ampeg SVT-410HLF are both ported cabs, but they sound completely different.
Both types can be designed and tweaked in such a way that you can't make a generalisation on their "sonic" differences. There are great sounding examples of both designs. The debate on this is allready going on for "ages" in the home-audio world....
The main three reasons I use ported enclosures for bassguitar are:
* more efficient
* mechanical more robust (within it's working range and when tuned correctly) which leads to higher SPL.
* lower distortion (higher fart-out-threshold )
But, I must admit there's something to the sound of lots of cone area in a closed design where the drivers don't have to work that hard like e.g. an 810.
The general rule on low frequency amplification is that it's "better" to increase the cone area instead of increasing the excursion. This leads to lower distortion and better coupling to the surrounding air.
Not only does the cab design matter, but the speakers as well.
Some speakers usually with a short, low depth cones may be fine in a sealed cab, where speakers like an EVM-12L have a Long throw, deep cone that moves a lot of air, so it will work better in and open or ported cab.
Of course the SVT 8X10 is a sealed chamber design, not just a closed back cab. The design is 4 sealed 2X10 chambers.
The Reeves 15" cab is bottom ported and might be considered a bass reflex cabinet design.
Google images of Bass Reflex Cabinets and you'll see all kinds of design options.
An interesting assessment, Arjank. Based solely on my own experience I would have to agree with you that ported enclosures are more efficient as a general rule, although it plainly depends on the drivers inside each enclosure - there can always be found exceptions.
So far as "lower distortion (higher fart-out-threshold)" for ported enclosures I would have to disagree. Again IME a good sealed cabinet is significantly tighter sounding and less likely to fart out than a ported design, which seems to allow it to be driven harder. I don't know that one side or another can be proven empirically - you would have to put the same drivers in both a ported and sealed enclosure then compare them. The issue would then be that the driver may have been designed to suit a specific enclosure type.
When it comes to quality of tone vs. practical portability, I think a 6X10 or 8X10 a generally taller cab, may be heavier dea weight, but you don't lift the dead weight, you use leverage to tip them in and out of a vehicle.
Same for a well designed 2X15.
As long as you can roll them, loading is actually easier on your back to move the 135 pound 8X10 than it is to lift the 85 pound head on top of it.
A 4X10 or 1X15 may seem less bulky, but loading and unloading, you'll be lifting that dead weight because the cabinets are too short to use leverage.
Last time I went speaker comparison shopping for a bass rig.
The EV/Mesa Road Ready Cabs 1X18" + 2X12 was superb.
yes, the driver is important but I have yet to see a driver that has optimal TSP's for a closed box to be as efficient(in the low end) as a driver of the same size with optimal TSP's for a ported enclosure.
One reason most sealed cabs sound tighter is because they lack the low-end extension.
The fart-out threshold of a sealed cab is lower compared to a simlar ported cab (so don't compare a ported 6" driver to a 15" in a closed cab)
See, the port puts a "load" on the driver around it's tuning frequency. In this range the driver has very low excursion, much lower then when the port would be closed. That's the reason why a port will reduce distortion and increase the fart-out threshold. Even a driver that has not the most suitable parameters for a ported cab can take profit from the load that a port put's on the driver. Drivers with an extremely high Qes shouldn't be used in a ported cab, those also won't take profit from the load that a port would normaly put on a driver.
I can show you simulations of a driver that has TSP suitable for both cabinet types that it will have a higher far-out-threshold in a ported cab.
I cannot argue with your clearly superior technical knowledge and logic, Arjank. Your point about the port loading the speaker is most valid and one I had not considered.
Trouble is, my ears tell me different.
Then the two cabs you've compared may differ greatly in some other part of the design other then being ported or closed.
E.g. the drivers in the closed cab may have far superior xmax compared to the drivers used in the ported cab resulting in lower distortion.
Or, you've send a signal to the ported cab that contains to much low-end below the tuning frequency of the port (1/4th octave below). That's why I wrote in my 1st post "within it's working range and when tuned correctly"
Edit: I added an example of a max SPL graph to visualize the above.
red = ported (typical 15" driver with TSP's suitable for both enclosure types, tuned to 50hz)
blue = closed (same 15" driver)
As you can see, below 37hz the closed box will have more output then the ported one and will not fart-out as fast in that range. But, between 38 and 200hz the ported cab will have more ouput, thus the fart-out-threshold is higher in that range then the closed box.
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