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Rear ports

Discussion in 'Amps and Cabs [BG]' started by huskies90, Nov 27, 2006.


  1. huskies90

    huskies90

    May 17, 2004
    I know this has been discussed before but when I search I can't seem to find a simple answer.

    I have always played front ported cabs but I just picked up a rear ported 2X10 that I want to plop on top of a front ported cab. When I ask people if this is a problem everyone looks at me like have ten heads.

    So, in simple terms. Is this a problem or not?
     
  2. nope
     
  3. Daytona955i

    Daytona955i

    Feb 17, 2005
    Albany, NY
    Depends. Shouldn't be, I run a rig like that. Actually it can come in handy because I can just move my stack farther or closer to a wall or corner and completely change the way I sound in the mix.
     
  4. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    The position of the ports has absolutely no bearing on this! This is simply the boundary effect which happens with any bass cabs - sealed, ported, transmission line, horn, whatever!

    Alex
     
  5. The frequencies coming out of the ports are omnidirectional :)

    So youve got no problems, i run a similar rig, using a front ported 2x15 and a rear ported 2x10, no problems at all!
     
  6. lug

    lug

    Feb 11, 2005
    League City, Tx
    I have a Peavey 4X10 TXF and and older 4X10 TX. The mids response is different (they changed the crossover point between these models), but to my ears the bottom end (where the port is effective) is identical though one is rear ported and the other is front ported.
     
  7. This has been beaten to death and the results are available by Search.

    In summary, there is (almost) always a conflict whenever two different bass cabinets are operating over the same bass range, and are within coupling distance of each other. The alternative is separating them by greater than 56 feet to insure no cancellation occurs.

    This is the reason pro sound folks do not mix subwoofers. Whether bass horns or direct radiators, they should all be identical when operating in a common bass range. In severe cases of cancellation, the inexperienced operator continues to crank the volume or EQ until he smokes a driver. It ain't the cabs' fault... it is being cancelled by the cab next to it.

    If both boxes are otherwise identical, the port location makes no difference. Changing the location of the port by a dozen inches is no impact to a 27 foot wavelength.
     
  8. huskies90

    huskies90

    May 17, 2004
    While I agree this topic has been discussed and I DID a search, there doesn't seem to be a clear answer. Most of the responses are like yours which for slow folks like me are incoherent. I am not asking the difference between front and rear ports just whether they can be stacked together. I thought the answer was "no problem" until your post although, I am not really sure if you are saying it is a problem or not...

    So, are you saying you'd have problem with two different cabs stacked even if they were both front or both rear?? Never heard that before, that is insane...56 feet????

    What is a severe case?

    I have always stacked two different front ported cabs and never had a volume problem although I did just creased the cone on my bottom speaker at a gig. Is there truth to what you are saying?? Of course, I had played over 100 gigs with that same set up...
     
  9. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Some interesting info from Bill Fitzmaurice about rear ports:
    http://www.talkbass.com/forum/showthread.php?t=290468

    I have used my SWR Goliath II (rear ported 4x10) with an SWR Son of Bertha (front ported 1x15) for about 140 gigs. No Problem!

    I also used the rear-ported cab with a front ported 2x10 (goliath Jr, III), again no problem. Don't sweat the "Ideal CASE" theoretical physics. No disrespect intended, but I suspect field conditions are very very complex compared to textbooks and simulations, all in my very humble opinion.

    Try it. It won't hurt anything unless you hear bad sounds. If you do hear bad sounds, turn down (or fire your singer, ha ha). :ninja:
     
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Most of what Bruce said has more to do with PA subwoofers, but he is correct. When using two ported cabs together they should be tuned with the same fb, otherwise there can be phase cancellation effects between the two, which can lead to toasted drivers.
     
  11. huskies90

    huskies90

    May 17, 2004
    At what frequency does this cancelling occur? Does it matter that I only play four strings? :D
     
  12. nysbob

    nysbob

    Sep 14, 2003
    Cincinnati OH
    That's interesting. I have a pair of of front ported single 15" cabs that I had made - the guy who made them deliberately tuned them a little differently from each other to curb or suppress a single resonant frequency, which can be issue on some stage environments. They're great cabs - I've been using them for the past 14 years.
     
  13. That sounds like a worst case scenario, ive never had any issues using front and rear ported cabs together.
     
  14. Steve

    Steve

    Aug 10, 2001
    I know you can put an acme b2 (rear port) on top of an epifani 212d (front port) an get nothing but great tone out of them.

    and I'm pretty anal about tone even by TB standards.:D
     
  15. bebass

    bebass Sho Me Music Commercial User

    Sep 3, 2006
    Bolivar, Missouri
    ShoMeMusic.com; Authorized dealer for Bergantino, Dingwall, Darkglass, Genzler, Phil Jones Bass, Quilter, Blackstar, Cort, Traynor, and other
    The problem with using a rear ported cab is that it can fart.

    Seriously, what bgavin & Bill are saying is very true. I have been totally amazed at this board with so many folks saying they mix this and that cab. The cancellations will occur. But different cabs may be tuned pretty close or very far apart and may not effect each other so much. And, some may actually like the cancellations, as in wow this cab setup is very punchy (lack of some frequencies due to cancellations), but be careful with this scenario.
    The boundaries where you have placed the cab(s) make a huge difference too, as in corner, wall, or open.
    It still comes down to experimentation to see if you like the sound. That said, I do not mix bass cabs.

    It doesn't matter if the cab is front or rear ported.
     
  16. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That's not what he said. You run into problems using two cabs with different tuning frequencies, not port placements. Port placement makes no difference.
     
  17. DEVILMAN

    DEVILMAN

    Nov 24, 2001
    New York,NY
    Beyond all this "techie" propaganda, I've been running my Bag End 2x10(rear ports) & my PV 2x15(front ports/Eminence drivers)together for years & it's one of the best combinations I've ever used live(my usual medium duty rig). It cuts & projects with tons of bottom & clarity. I've been complemented on the sound from this "inexspensive" set-up many times & never had any "weird" cancellations in the sound spectrum due to the different port areas, which IME is is the last thing in cab matching concerns. It's all about trial & error & what works for your situation/band setting/etc...


    ~S~
     
  18. Sorry, miswording, if it was more of an issue why wouldnt it be expressed more by manufacturers? And how are average folks meant to know the tuned frequency of the port, because im pretty sure it wont be the same with the different cabs ive used.
     
  19. bebass

    bebass Sho Me Music Commercial User

    Sep 3, 2006
    Bolivar, Missouri
    ShoMeMusic.com; Authorized dealer for Bergantino, Dingwall, Darkglass, Genzler, Phil Jones Bass, Quilter, Blackstar, Cort, Traynor, and other
    If you want to order from manufacturer "a" and you have a "b" cab of any manufacture, do you think they are going to tell you not to order?

    Most manufacturers are mostly concerned with sales, and hopefully, making a quality product. It is up to you how you use that product.

    This is fact, not "techie propaganda" as referred to by one poster.
     
  20. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Manufacturers are in the business of selling gear, not educating the consumer in how that gear works. You're on your own as far as that goes. Caveat Emptor.
     

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