Rear-ported vs front-ported ?

Discussion in 'Amps and Cabs [BG]' started by JayAmel, Dec 1, 2005.

  1. JayAmel

    JayAmel Moderator Staff Member Supporting Member

    Mar 3, 2002
    Aurillac, France
    Hi folks,

    I noticed that MarkBass offers their cabs in two versions : rear-ported or front-ported. There are some differences in specs, but in a general way how different are both these cab types supposed to sound ?

    Many thanks
  2. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    If implemented correctly, and with identical tuning and cab volume, then there won't be an audible difference. However I'd be surprised if the cabs don't have different tuning/volume, or there'd be no point (other than bs marketing) in selling both types.

  3. jokerjkny


    Jan 19, 2002
    NY / NJ / PA
    i'd just get the front ported. at least you can set the cab directly against a wall. rear ports would need some extra breathing room.
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    About an inch is usually sufficient. I'm curious also as to why the option is offered. There do appear to be other differences resulting in different responses, but the information on their site is inadequate to even venture a guess what they may be, beyond the tuning of the box.
  5. Jay,

    Search TB for this... there is a whole lot of useful discussion on this topic.

    The effective air mass in a port extends beyond the physical ends (both) of the port. This is why you don't want the port close to the driver inside the cabinet, or close to an obstruction outside the cabinet.

    A conservative rule of thumb for distance is, keep the rear ports 1 diameter or more, away from the wall or other obstruction. For example, if you have a Bag End cab with a 4" diameter rear port, then keep it at least 4" away from the wall.
  6. specplyrz

    specplyrz Banned

    Nov 11, 2005

    Bill, wouldn't that speaker bottom that close to the wall sound like a "boom box". My Ampeg 210 rear ported speaker as well as my Ampeg Ba210, rear ported combo amp, had to be well away from the wall.

    Klipsch used walls as reinforcement with their corner horn system. Any time I have ever moved a speaker close to a wall, I get increased bass response.
  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Normally, the ports would be active at a low enough frequency that a matter of inches will not matter.

    The whole wall/floor/corner issue is one of the space the speaker radiates into.

    A speaker up in the air dangling from a crane would be radiating into approximately "full space", i.e. all around in every direction.

    Set it on a solid surface, and half that volume is removed, for "half space". Put near a wall, and you get "1/4 space", etc.

    This only matters because of the difference between dispersion of higher frequencies and lows. Most highs are directed, and generally directed forward. Much less hits ANY wall, let alone one behind. This is due to the wavelength being similar to or smaller than the box and/or speaker driver.

    Therefore, "all" the energy goes forwards.

    But with lows, which are much more omnidirectional, it goes in all directions, the box is normally much smaller than the wavelength (3 meters at 100Hz).

    So hanging up, highs go forwards, lows are scattered, and the lows seem weak. They are out of balance with highs on the weak side.

    As you radiate into half, and 1/4 etc space, the lows get closer to being dispersed over the same area as highs. Depending on the speaker, that may mean that the lows are accentuated in some situations, being now out of balance with the highs because they are stronger.

    And, some spacings from the wall make cancellations at particular frequencies. That complicates the matter.

    Port position is probably the least of the problems with speakers near walls or in corners......
  8. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    FWIW, I prefer front ports since I put the cab up on a chair with a back on some gigs. So a rear port would be covered.
  9. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    As it should, and most bass cabs have such a poor low end that it's usually of benefit. It shouldn't lead to booming, as the frequencies going out of the port should be an octave or more below the 'boom' zone,though an insufficiently damped box could have problems. Reflections of the front wave off the wall would be a far more likely source of boom.
  10. Blues Cat

    Blues Cat Supporting Member

    May 28, 2005
    Katy, Tx
    I would get the front ported. You don't have to worry as much about how far your cab is away from the wall. I've already made the switch from rear to front ported & have way less issues w/my sound lacking lowend when there's not a wall directly behind me.
    IMO, front ported cabs sound better & more consistent from room to room. ;)
  11. Peter Murray

    Peter Murray

    Dec 13, 2005
    Toronto, Ontario, Canada
    Artist Relations and Social Media Manager, Pigtronix
    Hi Jay, and all,

    Interesting thread. I'm not as much of a physicist as some of you on here, but I work for Markbass and have had considerable experience with the front and rear-ported models.

    From an un-scientific standpoint, I can tell you that the front-ported models have more "throw" to them in the bottom end. The bottom end is fuller, wider, bigger. But still very defined--when I say wider and fuller, I don't mean "looser"! The rear-ported (HR) cabs sound more controlled, not quite as expansive. They are often used in combination with a front-ported cab (for example, a rear-ported 2x10 on top of a front-ported 15). The rear-ported models are also smaller and lighter, because the ports don't have to add height to the cabinet.

    The difference between front and rear-ported cabinets is definitely audible. It's also not a "better or worse" comparison. The character of the bottom end is simply different. Ideally you'd get a chance to hear the difference for yourself. Generally most bass players using a single cabinet prefer the front-ported models, unless they're very interested in using as small and light a cab as possible.

    Hope this answers your question!

  12. jacove


    Apr 12, 2003
    Aalborg, Denmark
    This may sound pretty lame, but why haven't anyone tried making a cab, which can switch between ported/sealed...or front/ could be useful in some situations to make the change...hehe, just a thought :smug:
  13. D.A.R.K.


    Aug 20, 2003
    great answers here.
    i prefer front-ported because sometimes you're not near any walls at all...(outdoor festivals, large stages, etc.)
  14. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    Thanks for that info Peter. From a scientific standpoint however, I strongly suspect that the difference in sound is predominantly due to the difference in cab tuning. Unless the ports in the rear ported cabs are absolutely tiny there is a significant difference in internal cab volume betwen the front and rear ported designs, and your comments mirror the tonal differences I'd expect from such a change in cab volume and tuning.

    Why does this matter? Because this information only holds true for Markbass's current cabs, with the tuning decisions made for the front vs rear ported designs. Markbass could have actually chosen to make two different ranges of front ported cabs, but with different tunings to get the same change in sound. Unfortunately that would be utterly confusing from a marketing perspective, having to choose between a higher and tighter tuned or lower and looser tuned cab, both with the ports in the same place, which only appear to differ in size and don't have the obvious front or rear port look.

    I'd like to see more side ports, a la Acme or EA's M-transmission line - just to show that it's immaterial (if executed properly).

  15. jake_tim


    Jun 28, 2005
    North Carolina
    forgive me if im wrong, but woudlnt a rear-ported cab, near a wall, give it more bass overall?

  16. Baloney.

    I'll take that bet on front-vs-rear being audible. A blind test will reveal no more than statistical chance variation for ports of the same type.

    In your example above, of course the rear ported example is smaller and lighter, because you are comparing apples to oranges. The front port you describe is a slot port with most likely a different area (tuning), which by design adds to the height of the cabinet, and probably sound different. It's not the location, it's the port design. The slot port most likely has a larger vent area and less port noise.

    If you want to compare a front-round port to a rear-round port, that is at least a common comparison.

    Ports don't have "throw". They are not wave guide devices, nor do they behave like one. A port is a pressure device, similar to blowing up a balloon. It does not inflate just in the front.
  17. Peter Murray

    Peter Murray

    Dec 13, 2005
    Toronto, Ontario, Canada
    Artist Relations and Social Media Manager, Pigtronix
    As I indicated in my post, I'm not engaging in a scientific debate here. The original question asked about Markbass cabinets and the difference between Markbass front-ported and rear-ported cabinets. This is what I replied to, based on how these particular cabinets SOUND. I believe this is what most bass players will be interested in! I'm not comparing apples to oranges, I'm comparing Markbass front-ported cabs to Markbass rear-ported cabs.

    No doubt the difference in sound between these particular cabinets is related to many detailed decisions made in their design.

    Perhaps if you heard the sound difference yourself you might have better works to describe it.

    stonecoldbass likes this.
  18. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I believe that what Bruce and Alex are getting at is that they'd prefer a technical explanation, as anything else is purely subjective and as such does not enable one to come to a logical conclusion when they are unable to hear it for themselves. Comparative SPL charts would be a nice start.
  19. Person2Person


    Sep 13, 2005
    Well, I tried to post, but it was removed? What is with this forum. It was not offensive.
  20. Cougar207


    Jun 17, 2005
    St. Charles, MO
    Usually when tuning an enclosure you need more space for a ported enclosure and less for a sealed. So, if someone where to do this they would also need to have a bunch of wood/foam or something to take up space in there when you opened the port. Not to mention the fact that some drivers don't respond well to one or the other.