why no sEALed fEARfuls???

[rpsands]

I disagree with that. The Delta 15a in my 64 B-15N cab, a smaller square cab, has very even response to my ears with a goodly amount of mids. Put that speaker in the 77 B-15N cab I used to have, and the mids from 500-800 end up scooped. You can fix it with EQ, but using the same amp with the same settings, the mids will be lower in comparison. SO I believe the box does affect mids to some degree. Not the port, but I believe box size enters into it.

I would lay a lot of money that it's differences in cabinet design (say one of them is not offset on the baffle, one of them has a deeper setback, one has differences in batting internally, etc.) that do not relate to ported or sealed.

It is absolutely sure that differences in box shape and dampening can affect the midrange. Porting or sealing not so much.

* Edit: I am a nooby. It's obvious what you're hearing. The ported Delta 15a is much louder at 100hz (+3db) which causes it to sound scooped but have the same mids.

 

[3rdcurve]

Yes, which results in differences in frequency response.

If that was the case I should be able to eq my amp so my cabs sound sealed then? I mean if the only difference is low frequency roll off, right?

 

[rpsands]

If that was the case I should be able to eq my amp so my cabs sound sealed then? I mean if the only difference is low frequency roll off, right?

Well, if you had sufficient eq, yes. The midrange character of the particular driver is another story.

 

[JimmyM]

I would lay a lot of money that it's differences in cabinet design (say one of them is not offset on the baffle, one of them has a deeper setback, one has differences in batting internally, etc.) that do not relate to ported or sealed.

It is absolutely sure that differences in box shape and dampening can affect the midrange. Porting or sealing not so much.

* Edit: I am a nooby. It's obvious what you're hearing. The ported Delta 15a is much louder at 100hz (+3db) which causes it to sound scooped but have the same mids.

Both cabs are ported, though the 77 has a shelf port and the 64 has a second inner baffle with port slots cut into it. Anyway, if all you were saying was the port doesn't affect mids, I believe that, and said so

 

[3rdcurve]

I disagree with that. The Delta 15a in my 64 B-15N cab, a smaller square cab, has very even response to my ears with a goodly amount of mids. Put that speaker in the 77 B-15N cab I used to have, and the mids from 500-800 end up scooped. You can fix it with EQ, but using the same amp with the same settings, the mids will be lower in comparison. SO I believe the box does affect mids to some degree. Not the port, but I believe box size enters into it.

Absolutely! If you go to the eminence website and click on any particular driver, the will have a link to response graphs in different sized boxes.

 

[xk49w]

Here's a graph to illustrate a common bass driver - beta 10. <snip>

Now plot cone excursion with 25W.

Not sure if its a valid generalization but with your example the ported cab exceeds xlim extremely below cutoff. Sealed cab, not so much. HPF probably a good idea in both cases but definitely for the ported example.

 

[Passinwind]

So, I guess the question is all in the title. Why are all the fEARful designs ported? I know Greenboy is trying to design the most efficient and well voiced cabs he can, why are ported "better" for that than sealed cabs?

Just a WAG: One of the primary design goals for the fEARful cabs is for them to sound as similar as is practical to the front of house PA. So, when's the last time you saw a PA use sealed cabs for the low packs?

 

[rpsands]

Both cabs are ported, though the 77 has a shelf port and the 64 has a second inner baffle with port slots cut into it. Anyway, if all you were saying was the port doesn't affect mids, I believe that, and said so

Tuning will drastically affect the size of the upper bass hump, as will the size of the box.

It affects upper bass, though, not mids. Louder upper bass, quieter seeming mids.


30hz tuning - 2.25db bass hump.

60hz tuning - 5db upper bass hump.

Dig?

 

[rpsands]

Now plot cone excursion with 25W.

Not sure if its a valid generalization but with your example the ported cab exceeds xlim extremely below cutoff. Sealed cab, not so much. HPF probably a good idea in both cases but definitely for the ported example.

Practically: For 4-string bass, the sealed cab's tendency to distort like crazy under 100hz will be far more of a liability than the ported cab's tendency to exceed xlim below the tuning frequency.

 

[eyeballkid]

Just a WAG: One of the primary design goals for the fEARful cabs is for them to sound as similar as is practical to the front of house PA. So, when's the last time you saw a PA use sealed cabs for the low packs?

NOW THAT is probably the answer that explains it!

for the record, I wasnt bitching that he doesnt make those designs, just wondering why, thats all, cos it seems that most GOOD cab designers have some of both in their arsenal. But if thats the point of fEARfuls then that makes alot of sense.

 

[billfitzmaurice]

why no DIY kickass sealed designs?

Because there's no inherent advantage to sealed. And even if there were long excursion high sensitivity drivers don't work well in them.

it seems that most GOOD cab designers have some of both in their arsenal

Only because some people want to buy sealed cabs, and if there's someone who wants to buy it there will be someone who'll sell it.

Ah, then I must prefer sealed drivers. I have heard BillF mention that you can cop a sealed box feel with a ported cab, but as you said it has to do with driver design as well. I still find it hard to believe that a driver is going to react the same way in a ported (even in a properly designed ) box as in a sealed one.

Believe it. This charts the Ampeg SVT driver in the same 1.5 cu ft box vented (blue trace) and sealed (red trace). Response is identical, but the vented is more sensitive.

The main difference is that the sealed cab will fart out in the low end with less than half the power that the vented will. That combined with the sensitivity difference, means it would take two sealed cabs to equal one vented in the low end.

 

[AwkwardLoudness]

So, I guess the question is all in the title. Why are all the fEARful designs ported? I know Greenboy is trying to design the most efficient and well voiced cabs he can, why are ported "better" for that than sealed cabs?

The 6" mid driver is in a sealed chamber in a fEarful 15/6 or 12/6 cab. The 15" or 12" sub is in a separate ported chamber. Best of both worlds?

 

[Phendyr_Loon]

The 6" mid driver is in a sealed chamber in a fEarful 15/6 or 12/6 cab. The 15" or 12" sub is in a separate ported chamber. Best of both worlds?

True, though there is little to no advantage or reason to port the mid drivers used in the fEarfuls. The crossover frequency can not utilize a ported enclosure.
So in the case of the "best of both worlds" idea, the mid in a separate sealer chamber is less of a option and more of a necessity.

 

[DukeLeJeune]

The 3015LF is probably more suitable for a sealed box than most big woofers, based on its T/S parameters and generous x-max. If you have your heart set on a sealed bass cab, I think you could do a lot worse than sticking a fEarful in a sealed box.

In my opinion a vented box sounds better in the midrange than a sealed box, this based on a series of blind listening tests I conducted a few years ago.

 

[rpsands]

In my opinion a vented box sounds better in the midrange than a sealed box, this based on a series of blind listening tests I conducted a few years ago.

Was this with a full range signal or with a sine wave of a given frequency or what?

My assumption is that the added bass content makes the midrange content sound less pronounced, which almost everyone finds more pleasing to the ear.

Could be wrong there, and I don't know your method obviously

 

[JimmyM]

The 3015LF is probably more suitable for a sealed box than most big woofers, based on its T/S parameters and generous x-max. If you have your heart set on a sealed bass cab, I think you could do a lot worse than sticking a fEarful in a sealed box.

No kidding? I figured with all that xmax, it would be pointless not to put one in a ported box to take full advantage. But I guess what you're saying is since the xmax would make more low end, a sealed box would be easier to get more low freqs out of it, right?

In my opinion a vented box sounds better in the midrange than a sealed box, this based on a series of blind listening tests I conducted a few years ago.

Care to expound on that a little, Duke?

 

[rpsands]

A 3015LF in a 2.6cf sealed box will perform competitively to four eminence betas in 4 cf--with twice as much power (and take 4x as much power before farting).

Pretty sweet if you're going for that low end rolloff, and does it in a very small box.

-3db @ 80hz, -6db @ 60hz. With as much power as it can take, probably usable for a 5'er if you can use an SVT 8x10 with a 5-er (since it'll get almost as loud down low given enough juice).

* again kinda sad given that a vented 3012LF comes damned close to this performance level. Giving up about 4db over 100hz and as much as 6db better than either at 50hz--7db better than the betas.

 

[DukeLeJeune]

Was this with a full range signal or with a sine wave of a given frequency or what?

My assumption is that the added bass content makes the midrange content sound less pronounced, which almost everyone finds more pleasing to the ear.

Could be wrong there, and I don't know your method obviously

I used two speakers which were identical except for the port and internal damping material (which was optimized for each type, and adjusted several times over the course of the test).

The music used had no bass instruments, and the test subjects were instructed to focus only on the human voice in the recordings, and judge how natural or realistic it sounded. Recordings of spoken voice were also used.

I expected the sealed box to be preferred, and was quite surprised by the outcome.

 

[rpsands]

I used two speakers which were identical except for the port and internal damping material (which was optimized for each type, and adjusted several times over the course of the test).

The music used had no bass instruments, and the test subjects were instructed to focus only on the human voice in the recordings, and judge how natural or realistic it sounded. Recordings of spoken voice were also used.

I expected the sealed box to be preferred, and was quite surprised by the outcome.

What was the frequency range of the human voice?

 

[DukeLeJeune]

No kidding? I figured with all that xmax, it would be pointless not to put one in a ported box to take full advantage. But I guess what you're saying is since the xmax would make more low end, a sealed box would be easier to get more low freqs out of it, right?

The key thing is the reduction in cone excursion at and near the port tuning frequency; that's what saves the vented box's bacon.

If a vented box isn't driven by high-level signals well below the tuning frequency, it is actually less demanding of x-max than a comparable sealed box. So assuming a judiciously-chosen tuning frequency, a given woofer will play a lot louder before fartout in a vented cab than in a sealed one. As Bill said a few posts up, "the sealed cab will fart out in the low end with less than half the power that the vented will." The 3015LF has enough excursion that its sealed-box fartout threshold will still be pretty high, though certainly not as high as if it were in a vented box.