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sealed and ported cabs?

Discussion in 'Amps and Cabs [BG]' started by b-ace!, Oct 1, 2004.


  1. b-ace!

    b-ace!

    Jul 15, 2004
    Hi, I've heard alot about sealed and ported cabs but I have no idea what that means. whats the difference between a sealed and a ported cabinet? which brands do which? I know GK do sealed but at the moment this means nothing to me. please help me be wiser :bawl:
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    A sealed cab is just that, sealed airtight. A ported cab has vent in it, usually with ductwork behind. A vented cabinet has the advantage of generally being smaller than a sealed cabinet with the same bass cut-off frequency (f3). Below that frequency a vented cab loses sensitivity at a rate of 24dB/octave. A sealed cab has a rolloff rate of only 12dB/octave below f3, so a sealed cab with a higher Fb than a vented cab may still have better response than the vented cab at some point below the vented cab Fb.

    In general you're better off with a sealed cab when the f3 is significantly higher than the frequencies you're putting into it; for instance, the average cab loaded with tens has an f3 of around 100 Hz; since a 4 string bass works down to 41 Hz sealed is usually the better option here to prevent overexcursion of the drivers. In contrast an 18 with an f3 of perhaps 60Hz is usually better off going vented, mostly since a sealed 18 cab capable of a 60Hz f3 may well have to be over 20 cubic feet volume to do it, while a vented cab can do so in about 3 cubic feet.
     
  3. b-ace!

    b-ace!

    Jul 15, 2004
    ahhhh I see. so what you're sayin is for a 410 a sealed cab is better, for anything bigger a 18" ported is better? are ampeg cabs sealed or ported? I've been to 2 gigs where they've used an Ashdown 810 cab(they're ported), and when I'm far away from the cab, the sound is a complete mess. its so blurry, it feels like you know the bass is there because you can feel it but you can't hear it. But when I got real close to the cab (2 or 3 metres away) I could hear anything fine. With the ampeg everything was clear. I know ampeg is seen as an better brand, but the clarity of notes the bass player was playing in a rock setting (the band was sparta) was impressive.
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That's most likely caused by a poor EQ choice by the player. I'd say he had the midrange scooped and the bottom cranked. No midrange= no presence. To vent or not to vent is pretty much dictated by the driver specs and box size. There is no hard and fast rule as to the superiority of one or the other; personal taste rules. It is easier to screw up a vented box than a sealed, though, and I personally have my doubts if every manufacturer has qualified speaker engineers on payroll.
     
  5. b-ace!

    b-ace!

    Jul 15, 2004
    I guess I'll just try them out and see which I prefer. The thing is shops here are so bad, its taken the shop 2 months just to get a cab for me to try out. are ampeg cabs sealed or ported?
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I believe most Ampegs are sealed. Most of their designs pre-date T/S parameters that started the industry wide switch away from sealed towards ported boxes in the 1970s.

    Want to get even with the music stores? Build your own. There is absolutely nothing magical about the speakers being sold today; in fact, from a technical standpoint they are all dinosaurs, not having progressed significantly in thirty years. You can duplicate a 4x10 SVT for less than $300, and beat it badly for another $100, and that's with a simple sealed box.
     
  7. b-ace!

    b-ace!

    Jul 15, 2004
    wow! thats pretty cool, though I have no clue about where to start and I really really have any sort of knowledge about cabs. I havent had an cab for 3 months now and I'm soo desperate to just get one and crank it up! :hyper:

    I'm deciding between an ashdown MAG 410 cab, an GK 410 BLX (backline) and a GK 410 SBX. I know the ashdown is ported and the GK stuff is sealed. It just a matter of getting them all in one place to try them out with my bass and hartke head.

    In terms of sound, if I was to choose a between organic (natural?) sounding cab and a hi-fi cab, I'd be on the side of the organic souding cab but wanting a little warmth. so if on a scale 1-organic cab and a 10-hi-fi, I'd be a 3 or 4 maybe. if that makes sense.

    have you made any cabs youself? how did they work out?
     
  8. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    do yerself a favor, just for me
    try a bag end 1x15 with and or without coaxial tweeter ;)
     
  9. b-ace!

    b-ace!

    Jul 15, 2004
    Do they do them in the UK? I've never seen one in the guitar shops I go to. I know Avatar stuff is only available to the US too. man you guys get it good! :spit:
     

  10. That price doesn't include LABOR (my time isn't free) or the cost of the tools to build this box. Table saw? Router? Drill? Jig saw?

    Furthermore, good plywood isn't cheap anymore, a sheet of 3/4 exterior is $40 or more. And don't forget handles, corner protectors, grills, jack plate, screws, glue, carpet covering, rubber feet....You can buy a 4x10 from Avatar cheaper than you can build it yourself IMHO.
     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I've made a few. Take a look here:

    www.billfitzmaurice.com

    What you're paying for with any speaker is, in order of cost highest to lowest, the following:

    1. Dealer profit.
    2. Manufacturers profit.
    3. Marketing and shipping costs, which includes advertising/catalogs/user endorsements
    4. Materials
    5. Labor

    When you build your own you eliminate all but #4. Now if your labor is worth $50 an hour I can see buying, and it's true that tools cost money, so the option is going to be limited pretty much to those who do have tools and don't have unlimited funds. That still leaves DIY as the better option for a goodly percentage of us.
     
  12. b-ace!

    b-ace!

    Jul 15, 2004
    wow! nice site!
     
  13. morebass!

    morebass! I'm listening

    May 31, 2002
    Madison WI
    Most cabinets on the markets now are ported. Almost all of ampegs are ported with the exceptions being their classic 8x10 and maybe one of their 4x10s. Most manufacturers go this route because ported cabs are more efficient in the low end. I've heard the sealed GK SBX 4x10s described as "tight and warm" The tightness is due to the lack of "flop". Sealed boxes prevent drivers from moving as much.

    The bergantino NV series cabs are sealed. Many players love them. I'd love to try one. Supposedly they cut very well and have a lot of warmth. No tweeter on these.

    Pretty much everything else out there is ported.

    Also, not many people make their own cabinets because they are not that easy to make, even if you already have all the tools. With the cost of plywood going through the roof it's an even less attractive option. Especially if you have Avatars available.