I have spent years as a tube amp/ported fanatic (and I still am) - Bergantino NVs and Ampeg 810s have defined my sound. Recent acquisition of two ported cabinets, Fender neo 810 and Ampeg 212AV, have forced me to be more open minded. It seems there is no generic rule. The Ampeg 212AV in particular is about as tight in the low end as any sealed cabinet I have played. I guess you just have to judge by your ears in the end and good cabinet design seems to be more important than whether it is sealed or ported. I also think that a good cabinet should respond readily to eq, if it is a bit woolly in a certain venue a good cabinet combined with a decent amp should be able to tweak it out.
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Ported cabs. Yes/No/maybe?
- Thread starter bottomfeeder33
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This is rarely discussed but I recall Andy Lewis addressing the issue in the instruction manual I received with my Acme B-4. There is a "damping" factor which needs to be taken into consideration which is why SS power amps were recommended for this particular enclosure. I can't provide any details but perhaps somebody can shed some light on the matter,
Riis
Specifically, output transformer amps (most tube, very few SS) the speaker is an indirect load magnetically coupled to the actual load (the output transformer primary winding). How well the speaker/cab combination self-dampens (controls overshoot) is a matter of design choices.
SS amps (except the Hellborg) the speaker is the direct load on the output (part of the circuit). Andy makes some specialized cabs that make compromises to achieve a specialized goal (and he is really good at letting any special needs be known, no BS, no end-user surprises).
SS amps (except the Hellborg) the speaker is the direct load on the output (part of the circuit). Andy makes some specialized cabs that make compromises to achieve a specialized goal (and he is really good at letting any special needs be known, no BS, no end-user surprises).
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I don't think there's much of a market for Eminence to create drivers with floppy/sloppy suspension needed for a sealed cabinet. Not at what people expect out of excursion. Especially when louder, smaller, lighter, low distortion ported designs are so easy to design with software these days, even for DIY designers.
I've tried a lot of sealed cabs and a lot of ported. I like and own only ported cabs. You can equivocate all you want about whether generalities apply regarding the inherent sound of the two types, but I think sealed cabs tend to emphasize low mids which makes them sound boxy to my ear. No sir, I don't like it.
- Mar 8, 2011
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There are too many good examples of both designs to dismiss either one, in my view. I have and use both. Mostly sealed lately because I've been goofing around with those designs for my own fun 
Can any one recommend a "good" sealed bass cabinet. I owned a Fender bassman 100 sealed cabinet with two 50 watt alnico 15's. I thought it sounded good.
Then an Ampeg 810E and since then ported cabs. Would love to hear of any sealed designs other than an 810 for the sake of trying one out again.
Then an Ampeg 810E and since then ported cabs. Would love to hear of any sealed designs other than an 810 for the sake of trying one out again.
Ampeg has a few relatively new ones
The SVT 210av, the PF210he and PF115he.
Ampeg has a few relatively new ones
Thanks. I will be sure to try them s I see them. Any one else have a sealed design they like?
- Nov 24, 2008
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All amplifiers have an inherent internal resistance that acts like a resistor in series with their output sections. The lower this internal resistance, the higher the "damping factor", and theoretically the tighter the bottom end. I know, that sounds like geekspeak... even my eyes are glazing over. Still, I'm going to take a shot at explaining how this affects the speaker's response down low.
As far as what the amplifier section itself "sees", this internal resistance is effectively added to whatever the speaker's voice-coil resistance is. And the effective voice coil resistance, or Re, in turn affects the woofer's "electrical Q", or "Qes". In fact Qes is proportional to Re, so Qes goes up proportionally as we increase the effective voice coil resistance. This matters because Qes is a major factor in determining the shape of the frequency response curve. "Damping factor" is typically calculated by taking 8 ohms (an arbitrary "typical" value for a speaker load) and dividing it by the amplifier section's internal, or "output", impedance. To calculate the amplifier's output impedance from a damping factor specification, divide 8 by that number.
Solid state amps tend to have a much higher damping factor (lower output impedance) than tube amps, and this is at the root of the notion that tube amps and ported boxes don't mix, because a lower damping factor = higher output impedance = greater effect (increase) on the woofer's electrical Q = might become boomy. BUT, this is not some mysterious "loss of control"; rather, it is something that can be modeled quite reliably with an ordinary speaker modeling program, and it ends up being a bump in the frequency response curve.
Let's walk through an example so that we can get a feel for this.
Suppose we have a tube amp with a damping factor of 5, and we want to see how much of an effect that will have on the speaker's frequency response curve relative to what our modeling program predicts. We first need to translate damping factor into output impedance, and that would be 8/5 = 1.6 ohms.
Next, let's assume that we're all geeks (otherwise, why have you read this far??), so we know the cab manufacturer is using the Eminence 3012LF woofer. This is an "8 ohm" woofer, but the actual voice coil DC resistance, Re, is 5.6 ohms. How do we know that? Geeks read spec sheets.
First we need to start with a, ah, baseline, for comparison purposes. Let's say we estimate the cab's net internal volume at 2.0 cubic feet, and guesstimate the tuning frequency at 50 Hz. We plot the curve and it's pretty flat: +.7 dB at 200 Hz, +.5 dB at 100 Hz, 0 dB at 62 Hz, and -3 dB at 49 Hz. For all practical purposes, this predicts the frequency response curve when the cab is driven by a high-damping-factor solid-state amp.
Now let's bring in our tube amp, run some calculations, and see what happens. We need to see how much Qes changes. So first, we need to see how much the effective voice coil resistance changes. Re' (pronounced "R e prime", the resulting new effective Re) = Re + amplifier output impedance = 5.6 + 1.6 = 7.2 ohms. So the ratio Re'/Re = 7.2/5.6 = 1.286. This is the factor by which Qes will be increased and become Qes' (Q e s prime). So Qes' = (Re'/Re) x Qes = 1.286 x .34 [from the spec sheet] = .437.
Now we go back and re-run our modeling program, substituting Qes' for Qes, and Re' for Re (if the program calls for Re). We get +1.0 dB at 200 Hz, +2.1 dB at 100 Hz, +1.2 dB at 62 Hz, and -2.5 dB at 49 Hz.
So over the two octaves from 49 - 200 Hz, this cab will average about 1 dB louder when driven by our hypothetical tube amp. The greatest difference is in the upper 70's through mid 80's, where it's almost 2 dB.
Now is this going to make the cab boomy? In this case, I think not... the warmer bottom end may or may not be what you want, but I don't think it's inevitably undesirable. However if this was a 4 ohm cab, with two 3012LFs in parallel, Qes' would be .534, and that's getting to be on the high side. Now the difference in the upper 70's to mid 80's is almost 4 dB, and that's pretty significant.
All of the "loss of damping" or "loss of control" attributed to low damping factor tube amps is fully accounted for by what happens to the frequency response curve. In my opinion it would be more useful to speak in terms of "introducing some bumpage into the low frequency response", instead of talking about "damping", which most of us - myself included! - have a hard time translating into an idea of "what it sounds like".
All of the "tighter bottom end" of a solid state amp is likewise predicted by the lack of bumpage in its frequency response curve... but if the speaker design has bumpage already built in, then a solid state amp can't make it go away.
In case it isn't obvious, the above has been the "long answer" to whatever the question was.
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- Nov 24, 2008
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Dukeorock has been working with sealed cabs a bit lately, I think, you might contact him for his opinion.
I like a nice fat low end. So I always end up with ported cabs. Not saying it can't be done sealed. But i always end up with a ported cab.
I have a Bag End D12, the damping material is amazingly dense and thick. I really like the cab. Rear ports don't bother me and I feel its very responsive like the sealed cabs I used to own. Still though would like to try and design/build a "good" sealed bass cab. I have played through guitar cabs, 4x12 with decent results. People have stated that the fender 2x15 Bassman 100 cab was terrible and by today's standards I get that, but it had a certain tone and punch that I am sure could be improved upon.
Duke, thank you for that terrific explanation of damping factor. I didn't understand most of it but it does explain why I don't care even a little about this notion that tube amps work better in sealed cabs than ported. Yeah, OK, tube amps behave a little differently in ported cabs. Big deal. What's important is the sound that comes out, and I've always believed a good amp into a good cab will always sound good no matter what they are. Might not always work out to your tastes, but it will sound good. But somehow or another, this damping factor thing got twisted over time into "Tube amps will cause your ported cabs to blow out way too much low end and explode so you have to use sealed cabs."
Puh-leeze!
but it does explain why I don't care even a little about this notion that tube amps work better in sealed cabs than ported. Yeah, OK, tube amps behave a little differently in ported cabs. Big deal. What's important is the sound that comes out, and I've always believed a good amp into a good cab will always sound good no matter what they are. Might not always work out to your tastes, but it will sound good. But somehow or another, this damping factor thing got twisted over time into "Tube amps will cause your ported cabs to blow out way too much low end and explode so you have to use sealed cabs." Puh-leeze!
For me the ampeg 410he and 810e are by far my favorite cabs and they are both sealed (non-ported)
Basically the reason is I want super low frequencies coming out of the PA but not onstage. because having super low frequencies onstage not only makes your amp less efficient because it takes a lot of power to reproduce really low frequencies. But it makes your sound onstage very muddy and unintelligible. With a sealed cab i get a tighter stage sound with more clarity so I can hear myself well and play better, but i can still send the pa all those really low frequencies using the xlr.
It's actually funny in a way. I see so many bass players get talked into buying ported cabs, with sayings like "this cab is specifically designed for 5 string bassist" but the funny thing is what happens live. Because when you have a low tuned cab that puts out a lot of low end, you compensate by cutting lows on your eq. But then guess what happens? If your using an xlr sognal and or mic signal and your cutting lows because your cab is boomy onstage then the signal becomes thin in the PA. So imo lower tuned ported cabs are counter productive when it comes to playing with PAs with good subs. At the same time ported cabs are my preference when playing without any pa support. So I think it just depends on your gigging situation. If the majority of your gigs are situations where your not going through the pa then get a ported cab, but if your playing through PA systems with like 8-12 18" subs like I do most shows get a sealed cab.
Basically the reason is I want super low frequencies coming out of the PA but not onstage. because having super low frequencies onstage not only makes your amp less efficient because it takes a lot of power to reproduce really low frequencies. But it makes your sound onstage very muddy and unintelligible. With a sealed cab i get a tighter stage sound with more clarity so I can hear myself well and play better, but i can still send the pa all those really low frequencies using the xlr.
It's actually funny in a way. I see so many bass players get talked into buying ported cabs, with sayings like "this cab is specifically designed for 5 string bassist" but the funny thing is what happens live. Because when you have a low tuned cab that puts out a lot of low end, you compensate by cutting lows on your eq. But then guess what happens? If your using an xlr sognal and or mic signal and your cutting lows because your cab is boomy onstage then the signal becomes thin in the PA. So imo lower tuned ported cabs are counter productive when it comes to playing with PAs with good subs. At the same time ported cabs are my preference when playing without any pa support. So I think it just depends on your gigging situation. If the majority of your gigs are situations where your not going through the pa then get a ported cab, but if your playing through PA systems with like 8-12 18" subs like I do most shows get a sealed cab.
Check out the ampeg 410he. It's the exact same speakers as the 810. It's a sealed cab just like the 810e and is probably the lightest non neo 4x10 you'll find.
Good post. I'd also point out, though, that some of us don't even like those super lows to come through the PA. I'm not a fan of them at all and I've taken to forcing those frequencies to be rolled off with a pedal. Would much rather not use a pedal, but some of these soundmen I work with can't be trusted
