Preference For Sealed Cabs? Why?

[FFTT]

Some players love boosted mids playing live, where I generally cut the mids, especially for recording.

Clips would be helpful, but that also depends on the signal chain, the instrument, the amp, the strings, the player's attack, bass tone and volume settings, and how the cab was mic'd up.

 

[dukeorock]

Better yet, post bass-only recordings of ported vs. sealed cabs.

I did a couple primitive recordings for my own fun. Just recorded onto my iPhone at the shop. The sealed cab I made is similar in size, weight and power handling to a Fearless F115, so I used that in an attempt to keep things as apples to apples as I could.
Gear used was a Reiner 6SL7 pre with all tone controls set to noon. Basses were a Dingwall Super J/P4 and 1982 Gibson G3. I kept the controls the same and just bounced back and forth between cabs. I only shared the clips with two buddies of mine. Both cabs sounded really good and very different from each other.

I did the same 'test' using an upright into the Pope pre and recorded that as well. Again, both were very good and would work well, but they were very different. When I have time, I'd be happy to do this again with better recordings, but that will be a while. Headed to Europe for a tour in a few days and have too many cab builds to finish!

 

[Luke the Fluke]

I did a couple primitive recordings for my own fun. Just recorded onto my iPhone at the shop. The sealed cab I made is similar in size, weight and power handling to a Fearless F115, so I used that in an attempt to keep things as apples to apples as I could.
Gear used was a Reiner 6SL7 pre with all tone controls set to noon. Basses were a Dingwall Super J/P4 and 1982 Gibson G3. I kept the controls the same and just bounced back and forth between cabs. I only shared the clips with two buddies of mine. Both cabs sounded really good and very different from each other.

I did the same 'test' using an upright into the Pope pre and recorded that as well. Again, both were very good and would work well, but they were very different. When I have time, I'd be happy to do this again with better recordings, but that will be a while. Headed to Europe for a tour in a few days and have too many cab builds to finish!

aww go on - we don't mind low quality recordings!

 

[dukeorock]

aww go on - we don't mind low quality recordings!

I don't think it's a good idea. Lots of background noise and whatnot. Also concrete floors and reflections. It was meant to give me a reference point to help research this. While it did serve to show the differences, it doesn't show either cab in their best light

 

[FFTT]

Well you are in Nashville.

I totally get small custom builder budgets and the cost of having proper studio demos produced, but these days
there is no better way to promote your gear than to post good sounding demos on youtube.

My Reeves/ SVT demos have been viewed in over 70 countries every month.

 

[JGR]

So we've been talking here about the difference in "feel" of sealed and ported. And we've spoken about how the low end is different, how the ports come out of phase but lower and so on... so that's the bottom end - but a lot of sealed cab fans are talking about how the note sounds across it's whole range....

and I'm thinking how, take a popular design, the Fearful range - seem to have a ported bass and a sealed mid..... what effect does that have having both systems (at different freqs) - or does the difference really only matter in the bottom end?

We're mainly talking about the bottom end. Separate mid drivers need to be in their own chambers regardless of whether the woofer is ported or sealed to protect them from distortion and over-excursion as a result of the woofer back-pressure.

 

[Mike Arnopol]

One other thing--maybe Aged or Astro can chime in

One area I think that the ported box can affect mids--

Most ported boxes are tuned above 42hz. So--let's say a ported box is tuned at 47hz (many are). Any thing the speaker sees below that will cause the woofer to perform in an unloaded state. Like it's flopping around in free air. I would assume that putting the woofer in such a state would detrimentally affect frequencies above that in the harmonic sequence.

Duke gives an option by blocking ports. This lowers the tuning frequency. I think that Greenboy has inched his tuning frequencies down. Andy of Acme uses lower tunings than most. I always preferred lower cab tuning. Response is more like a sealed box but with a bit of added oomph in the low-lows---a gentle slope that can be eq'd up. You lose some sensitivity and ultimate volume but it's more of a hybrid between both. When I had a Thunderchild 12 I always blocked one port. Had to turn the bass up a notch but I much preferred the low end response and envelope of the note.

 

[dukeorock]

Maybe a little background would be helpful.

I became an authorized greenboy designs builder about 3 years ago. Up to that point, I had been a full time musician (still am). Most of my cabs were obtained through endorsements and some of the cabs were pretty good but I couldn't help but think there was a better solution for loud upright bass. That led me to Talkbass and research. I found some boutique cabs that were much closer to what I was looking for and struck up some terrific friendships with some really smart, interesting people like Duke (AudioKinesis), Dave Green, Mike Arnopol, Jonathan Reiner and several others. I tried a fEARful cab and was impressed. The thought of making cabs was also exciting, so I built a fEARful 1515/66/1,15/6/1, 12/6/1cube and a 15sub in about two weeks to see if I could do a decent job at it. I guess I did because I got accepted as an authorized builder. It was a really fun process and I've built well over 100 cabs since then. At no point would I have ever claimed to be a cab designer. I never experimented or strayed from Dave Greens specs once. That would be horrible ethics and I happen to think Dave is a brilliant designer, so I built everything to spec. In those 3 years I began studying and asking questions to figure out how stuff works

Since I have stopped taking orders on cabs and am leaning toward ending my participation in the authorized builders program, I still have a shop, tools and plywood, so why not have some fun? I have no grandiose plans or illusions about reinventing the wheel. I do want to see if I can make my favorite cab for what I like. Maybe my favorite cab will be two cabs. Maybe it will be sealed, maybe not. For now, I just want to goof around in the shop, play music and build stuff. I am collaborating with a good friend who happens to be an amazing designer. We throw ideas back and forth and it's fun again to build cabs. We're currently playing around with 4 different design variations and it's been a blast. Once I get my backlog of orders filled, we will dive into these designs more seriously and see what we think of them. For now, I'm just fooling around with this one sealed concept we came up with.

 

[dukeorock]

Well you are in Nashville.

I totally get small custom builder budgets and the cost of having proper studio demos produced, but these days
there is no better way to promote your gear than to post good sounding demos on youtube.

My Reeves/ SVT demos have been viewed in over 70 countries every month.

Understood! If I were attempting to promote anything I would do that

 

[FFTT]

I totally get what you're going through.

 

[dukeorock]

It's tough for a cab builder like myself to start threads because it can easily come off like a Trojan horse sales pitch. I have nothing for sale at the moment. Maybe a couple microphones and basses, but nothing in conflict here

 

[FFTT]

I have no commercial affiliation what so ever with any manufacturers.

I post demos simply to share what I'm learning.

 

[JGR]

One other thing--maybe Aged or Astro can chime in

One area I think that the ported box can affect mids--

Most ported boxes are tuned above 42hz. So--let's say a ported box is tuned at 47hz (many are). Any thing the speaker sees below that will cause the woofer to perform in an unloaded state. Like it's flopping around in free air. I would assume that putting the woofer in such a state would detrimentally affect frequencies above that in the harmonic sequence.

Duke gives an option by blocking ports. This lowers the tuning frequency. I think that Greenboy has inched his tuning frequencies down. Andy of Acme uses lower tunings than most. I always preferred lower cab tuning. Response is more like a sealed box but with a bit of added oomph in the low-lows---a gentle slope that can be eq'd up. You lose some sensitivity and ultimate volume but it's more of a hybrid between both. When I had a Thunderchild 12 I always blocked one port. Had to turn the bass up a notch but I much preferred the low end response and envelope of the note.

Unless you are putting in a lot of energy below the frequency where the driver unloads (exceeds Xmax) which is well below the tuning frequency, I don't know that it would excite break up nodes since it is still operating within it's linear region. If anything, I'd expect that type of effect in the 70 - 90 Hz range where excursion peaks before the drop-off since there is a lot more energy up there in the second harmonics.

I think part of the sealed appeal is the way the driver excursion stays consistent in the lower registers once you hit the max power handling - no peaks or dips, no unloading down low. I also think they sound better when you drive them at the limits and beyond.

 

[aborgman]

Well, gee---than someone should tell that to John Dunlavy who was one of the most respected speaker designers in audio who's testing lab rivaled virtually anything out there. His speakers (in the late 90's) routinely were regarded as the best of the best in Stereophile and Absolute sound.

Stereophile...

Mpingo Discs, Shakti Stones, Directional Cables...


There is a reason engineers called it "Stereophool"

 

[will33]

Unless you are putting in a lot of energy below the frequency where the driver unloads (exceeds Xmax) which is well below the tuning frequency, I don't know that it would excite break up nodes since it is still operating within it's linear region. If anything, I'd expect that type of effect in the 70 - 90 Hz range where excursion peaks before the drop-off since there is a lot more energy up there in the second harmonics.

I think part of the sealed appeal is the way the driver excursion stays consistent in the lower registers once you hit the max power handling - no peaks or dips, no unloading down low. I also think they sound better when you drive them at the limits and beyond.

Agreed.

Yes, excursion shoots up fast below tuning, but it's still not immediate. Still is within linear region for maybe 1/2 octave or a bit less. Usually (according to models as well as me just seeing how loud I can play before audible fartout) in a cab tuned to say 40hz, if it hits xmax or audible distortion at "X" input above tuning, it'll take a similar amount of power @ 31hz to send it over xmax as well.

I think Mike has a equally valid point though when looking at higher tuned cabs and lower tuned basses. Wild cone movement down there then has to affect the quality of the higher frequencies as well. Maybe something sorta similair to how whizzer cones or coax's on high excursion woofers don't usually work out very well, under higher power at least where you'd be using the excursion capability.

 

[DukeLeJeune]

...and I'm thinking how, take a popular design, the Fearful range - seem to have a ported bass and a sealed mid..... what effect does that have having both systems (at different freqs) - or does the difference really only matter in the bottom end?

Over in the home audio world, ported vs sealed is debated, and one of the accepted tenets is that sealed cabs have better midrange because midrange energy escaping through the ports is unwanted coloration.

Years ago (before I got into bass cabs) I was working on optimizing the stuffing inside a sealed box, and was using two identical boxes and doing A/B comparisons of the different stuffing configurations. Anyway at some point I decided to port one of the boxes just to confirm that sealed boxes really do have better midrange. I mounted a 3" diameter flared port on the back of one box. I used only acapella vocals or little-girl-with-guitar recordings to minimize any low-end advantage the ported box might have. As usual my wife did the actual listening, without knowing what was different about the two boxes. I told her to focus on the voices and pick which sounded most realistic. So it was a controlled blind test with a very small sample size.

Well to my surprise and dismay, she preferred the ported box! That went against all of my beliefs on the subject, and against the collective wisdom of vast herds of audiophiles. I kept tweaking the damping material in the sealed boxes, and even took out all the damping material in the ported box to handicap it as much as possible, and every time she picked the ported box. And I agreed with her.

In retrospect, I think I just happened to stumble upon a ported configuration that worked really well in the midrange, with the rear-mounted flared port.

Anyway, point being, in my somewhat unorthodox opinion, ported boxes can offer minor advantages in the midrange region.

As far as combining ported wooferboxes with sealed mid-chambers, or vice-versa, I see no reason not to mix and match as long as the midrange drivers are adequately protected. My marketing department likes to go on about my "open format" mid-chambers, but in a way they're really just high-tuned ported boxes (and have to be approached as such from a crossover standpoint).

 

[JGR]

Over in the home audio world, ported vs sealed is debated, and one of the accepted tenants is that sealed cabs have better midrange because midrange energy escaping through the ports is unwanted coloration.

Years ago (before I got into bass cabs) I was working on optimizing the stuffing inside a sealed box, and was using two identical boxes and doing A/B comparisons of the different stuffing configurations. Anyway at some point I decided to port one of the boxes just to confirm that sealed boxes really do have better midrange. I mounted a 3" diameter flared port on the back of one box. I used only acapella vocals or little-girl-with-guitar recordings to minimize any low-end advantage the ported box might have. As usual my wife did the actual listening, without knowing what was different about the two boxes. I told her to focus on the voices and pick which sounded most realistic. So it was a controlled blind test with a very small sample size.

Well to my surprise and dismay, she preferred the ported box! That went against all of my beliefs on the subject, and against the collective wisdom of vast herds of audiophiles. I kept tweaking the damping material in the sealed boxes, and even took out all the damping material in the ported box to handicap it as much as possible, and every time she picked the ported box. And I agreed with her.

In retrospect, I think I just happened to stumble upon a ported configuration that worked really well in the midrange, with the rear-mounted flared port.

Anyway, point being, in my somewhat unorthodox opinion, ported boxes can offer minor advantages in the midrange region.

As far as combining ported wooferboxes with sealed mid-chambers, or vice-versa, I see no reason not to mix and match as long as the midrange drivers are adequately protected. My marketing department likes to go on about my "open format" mid-chambers, but in a way they're really just high-tuned ported boxes (and have to be approached as such from a crossover standpoint).

I'd assume in the home audio world we're going for clean/minimizing coloration. I would think we generally get more coloration/distortion in a sealed box, but in MI applications, that's not always a bad thing, and I suspect is one of the attributes the sealed camp likes - part of the "growl" that seems to be present in these designs. Too much of course makes the mids sound honkey, and over damping kills everything, so there's definitely some dialing in with various thickness/locations, as well as overall choice of damping material. IME, it definitely has a big impact on the outcome, and is maybe a bit more of a critical aspect of design than for a ported box.

 

[Coolhandjjl]

Stereophile...

Mpingo Discs, Shakti Stones, Directional Cables...


There is a reason engineers called it "Stereophool"

BFM refers to them as Oddphiles.

 

[dukeorock]

Anyway, point being, in my somewhat unorthodox opinion, ported boxes can offer minor advantages in the midrange region. ).

There's no way I'd ever step into the ring against you when it comes to enclosure design, though I do have a question!

In that example you cite, vocals only program material, your wife preferred the ported design for the mid range. I have no reason to doubt that. I've found I can make lots of different cabs sound good at low levels and with less low end. It's when you're trying to get up over the drums and guitars where things can get nutty, not to mention so many crappy sounding rooms one might be faced with playing live. Try to add more lows in your amp, and the midrange can go to pot real quick. It's not a home installation where everything gets tuned to that particular space, then stays there. The goal, in my mind, is an attempt to lessen the variables one encounters playing different rooms every night with a tone that the player finds pleasing to them.

I don't pretend to know the answer, but I know bass guitar and upright for that matter, ask a lot from our cabs from the low end up.

 

[AstroSonic]

One other thing--maybe Aged or Astro can chime in

One area I think that the ported box can affect mids--

Most ported boxes are tuned above 42hz. So--let's say a ported box is tuned at 47hz (many are). Any thing the speaker sees below that will cause the woofer to perform in an unloaded state. Like it's flopping around in free air. I would assume that putting the woofer in such a state would detrimentally affect frequencies above that in the harmonic sequence.

Duke gives an option by blocking ports. This lowers the tuning frequency. I think that Greenboy has inched his tuning frequencies down. Andy of Acme uses lower tunings than most. I always preferred lower cab tuning. Response is more like a sealed box but with a bit of added oomph in the low-lows---a gentle slope that can be eq'd up. You lose some sensitivity and ultimate volume but it's more of a hybrid between both. When I had a Thunderchild 12 I always blocked one port. Had to turn the bass up a notch but I much preferred the low end response and envelope of the note.

Ported boxes can affect the mids in two ways. First, ports can act as open ended pipe resonators. These are excited by sound at or close to the resonant frequency from the main driver. The Q of these can be quite high. An impedance sweep will show a blip at the ports pipe resonant frequency. I designed and built a cab with a bad case of this. This can be prevented by crossing the woofer well below the pipe resonance. You can also use shorter ports, pushing their resonant frequency above the woofers passband.

Ports do not leak mids and highs significantly, as their mass reactance essentially closes them up above the higher of the two impedance peaks. I have a pair of speakers in ported cabinets using full ranger drivers. The drivers send a wide range of frequencies into the cabs, but only low bass is heard exiting the ports. There is minimal insulation on 3 sides.

High excursions may fowl up the mids and highs via doppler distortion. The higher frequencies are modulated upward and downward in frequency as the cone moves back and forth (reproducing bass). This is somewhat controversial, with some experts claiming it as an important source of distortion. It turns out to be inaudible on most signals, but can be heard using simple, clean signals. This could impact ported cabs more than sealed ones due to unloading below the trough between the bass impedance peaks. It is really more than unloading, as the port mass is added to that of the driver cone, producing the lower impedance peak. In essence, the cone is out of phase (up to 180 degrees) with the port, so that inward movement of the cone drives the port air mass outward (and outward cone motion pulls the port air mass in). A little damping material in or too close to the port will damp this resonance, decreasing the lower peak, but leaving the upper peak only slightly changed (this also damps the helmholtz resonance resulting in a modest change to the upper peak). Below the lower peak, phase rotation decouples the port and driver, and the driver is unloaded. There are probably better ways to explain this, so others feel free to correct and refine.

I too like the low tuned, EBS-like alignments. Early on, after the initial 'wow, listen to that bass! ' reaction to near flat alignments (with the bass response rolloff knee only a few db below reference), I found that there was actually too much bass in-room, and that the quality of the bass was not as good as I had hoped. Using an low-tuned alignment that drops the knee 4-6 db below reference solves this and results in excellent bass quality. You do have to watch for a power handling 'sag' between Fb and the upper peak. There can be a lot of energy there and the driver behaves as though it were in a sealed box, above its resonant frequency. I prefer an alignment that loads the driver down to the lowest expected frequency (like low B, E, etc). The lowest expected frequency should fall within the impedance trough.