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1 Sealed, 1 Ported Cabinet Together?

Discussion in 'Amps and Cabs [BG]' started by spitfirees20, Jan 7, 2014.

  1. spitfirees20


    Dec 20, 2013
    Hello All,

    Looking for some experience here. Right now I have 1 cabinet, an custom 2.25 ft^3 sealed enclosure with an Eminence CA154. I really like it because I like the sound of a sealed cabinet, it's super portable (30 lbs and easy to cary with one handle), and reasonably loud. However, I have two problems. One, I need a little more volume. Two, I feel like it doesn't go low enough. Modeled in WinISD the -3db rolloff is at 80 Hz, and the -6db rolloff occurs at around 60 Hz. When I hit the low E, I can tell it's missing something as the fundamental occurs at 41 Hz. It's most noticeable when hit an E and then an A after for comparison; you can clearly hear the strong fundamental of the A.

    What I want to do is add a second cabinet. I could add another identical custom sealed enclosure, but I was thinking about a ported 1x15 or 1x18 for some extra low end extension. I know that mixing two different types of cabinets is usually seen as a bad idea, but I was wondering if anyone has heard this combo in person? Ideally if you've heard 1x15 sealed and 1x15 or 1x18 ported at the same time that would be cool, but if not, any combo of ported / sealed I would be interested to hear about.

    If it matters at all, I'm running my bass through a sansamp vt bass di into a carvin poweramp. I was also thinking about doing something crazy, like maybe running just the vt bass into one side of the poweramp for that ampeg distortion into the sealed 15, and then one side into a cleaner preamp to go into the ported 15 or 18. Would that work, or would I be introducing some other weird phase issues?

    Thanks in advance!
  2. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    Clean/dirty rigs are certainly a normal thing and people doing that don't usually worry about phasing. If it sounds good...awesome! :D

    [del]It could work. Have you tried a bass boost around 4-6 dB at 50 Hz to compensate or would that drive your 12 too hard?[/del]

    In retrospect, that's not the best idea. ^
  3. spitfirees20


    Dec 20, 2013
    It's actually a 15, and I haven't yet because the only graphic eq I have is for guitar and it stops at 100 Hz. I can probably find an EQ pedal meant for bass and give it a try though!
  4. Boosting E fundamental in sealed cab will only eat up power, heating your driver.

    Try boosting 80hz. It's not like svt 8x10 has much response down below 80hz, yet that tight sound you think you like, you don't?
  5. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    The phase anomaly between the ported and non ported cab is only in the area of the overall frequency response that the port is extending the low frequency, therefore as the sealed enclosure rolls off quite steeply, the ported cab will just take over and extend the low frequency response without having much in the way of phase cancellation, as there is little or nothing coming from the sealed enclosure to fight with, phase wise, at that frequency.:bassist:
    This is not just the usual music tech student theory vis a vis phase anomaly dogma (that abounds this board like a plague), this is from actual tested experimentation with 12" drivers and cabinets measuring the results with Waves software.
  6. wcriley


    Apr 5, 2010
    Western PA
    AstroSonic and Dragonlord like this.
  7. JBL K2 Project with IET

    JBL did something similar in their no-holds-barred design of the K2.
    In a nutshell, they use two of the same bass driver, but in two different vented alignments.

    The Bessel (0.577) offers the tightest transient response and minimal phase shift, where the Butterworth (0.707) offers the flattest response.
    These Q values are normally associated with sealed boxes, but they do have vented equivalents: SBB4 and Flat.

    JBL's objective was reducing the "vented box" sound inherent in reflex cabinets.
    In a reflex design, vent radiation is 90-degrees, or more, out of phase with the cone.
    Sealed boxes do not have this, and sound "tighter" or "faster".

    Opinion: IET has no value for live electric bass in a mix.
    This is for the critical audiophile.

    For the OP, mixing different drivers over the same operating range is a recipe for merde.
    If this had merit, the pros (Meyer Sound, et al) would do it, and they do not.
  8. spitfirees20


    Dec 20, 2013
    Thanks for all of your well thought out and informative replies, everyone! Basically, after reading all of these and doing some more independent research, I've realized it's an awful idea, unless I want to get a larger ported cab and set it up with some sort of crossover, so that I use the ported cab for the lows and the 15 for the highs, which I'm not really interested in.

    What I'm going to do is:
    - Get another identical cab
    - Try a boost around 100 Hz

    Thanks again for the help!
    PawleeP likes this.
  9. First you should learn what frequencies you actually want to hear. The low A you hear presently isn't 55hz, it's 110hz overtone. This is "tight" bass. Your sealed cab rolls off too much 80hz so E pales.

    EQ and two cabs may get you over the line. A couple of tl606 type cabs might be better. They don't do fundamental E either.
  10. PawleeP


    Oct 8, 2012
    what do yo mean by merde?
    I tried a 212 sealed on top of a 215 with an svt cl
    had a hard time getting a good EQ
    ended up disconnecting the 212 after a few songs
    even though the 212 sounded good by itself in
    the house when tested it..
    any one else ever try this live at a smallish sized venue?
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    In general, mixing a sealed box with a bass reflex box (of similar efficiencies) is not a great idea. The effects of the port certainly can have an effect even one octave above F3, which is right in the meat of the sealed boxes low end response. The different relative levels argument doesn't hold up under these common conditions.

    The phase response of a ported box with a high filter q response combined with the sealed box response can result in detrimental results.

    This doesn't mean all combinations will be bad, but certainly suggests that you should listen to your proposed combination before plunking hard earned money down.

    If it was me, and you really like the sealed box sound, I would recommend another identical sealed box.
    BassmanPaul likes this.
  12. craigie


    Nov 11, 2015
    What about cutting a port in the box you have?
    Dragonlord likes this.
  13. morgan138


    Dec 10, 2007
    Two TL606s with 3015 kappalites and the ports partially blocked is my heavy doom metal in C standard setup.

    Blocking the ports and switching from the original EVM-15Ls both increased the cabs' low end very noticeably. At this point they've got low bass to spare, even at real loud volumes.
  14. BogeyBass


    Sep 14, 2010

    yes this is a very wise decision. and yes like it was explained by downunderwonder when you were playing your low E and noticed a drop in overall sound it was not the 40hz drop you were hearing. you were hearing the second harmonic drop at 80hz. And yes you already reviewed the spl chart in the sim. if you notice your -3db is at 80hz and that is what your hearing. 40hz is sub frequency and its very difficult to obtain.

    doubling speakers will give you a 3db increase now at that 80hz you were looking for and allow more cone movement or power handling so you can add 80 to 100hz EQ boost to give you that "oooph" you desire. which again is a very good suggestion.

    what your mainly working against is the impedance curve of the speaker and the resonate frequency of the CA154 is 51hz in free air. when you place a speaker in a enclosure the resonate frequency will rise. In this case it rises to around 80hz and will be visible in the impedance curve chart in the sim you will see a impedance spike around 80hz. everything is pretty much down hill from there as far as what the speaker can produce accurately with good transient.

    likewise in a ported system the spl chart can be rather impressive and people think its so amazing. in reality looking at the impedance chart youll get two huge spikes and the first spike will be even higher. so again any accuracy and transient will be downhill from that first impedance spike. and likewise actual representation of the signal is not accurately reproduced by the cone since cone movement is limited around Fb in a vented system

    in a ported system with a ca154 in 2 cubic feet its very possible that impedence spike would be higher at around 100hz instead of 80hz
    and depending on FB a majority of any signal below that will not be reproduced by the speaker. cone excursion is limited about 10hz above and below Fb. so even though the static little picture can show amazing or improved bass response at 40hz. in the real world its just poof of port and the transients and accuracy is poor below that gosh darn impedance spike.

    only way to beat that impedance curve is to take a 18" speaker with a resonate frequency of 30hz and in a sealed cab that rises to 65hz so now you have a sealed system with more accuracy around 65hz instead of 80hz. still doesnt touch that 40hz fundamental and most players would probably be annoyed by it cause they aint use to hearing that much sub.
  15. PawleeP


    Oct 8, 2012
    box is a little small for a 212 vented (so I sealed it), and has 2 approx. 25 year old black widow 12's in it.
    had it sitting on to of a 215 road ready diesel w/1 evL and 1 evB
    sounded ok by itself when I unhooked the 212 1/2 way through a show..
    if I had 2 more black widow 12's I could maybe find a cab to put them in..
    thanx for the idea
  16. PawleeP


    Oct 8, 2012
    I had thought 3015's liked bigger vents than the std tl606 size!
    maybe the post I read had it backwards.. interesting..
    I do want to try some 3015's in the boogie one day if I can afford!
  17. morgan138


    Dec 10, 2007
    I don't know what their ideal vent would be...I was working at the problem from the other end, because I had the two TL606 cabs and didn't want to blow more EVM-15Ls. The 3015 was the closest match I could find, sounds pretty close to the EVM but with more bass and a bit less midrange cut (still quite a bit though).

    Putting in the half-vent plugs as described in the TL606 plans, the speakers got a noticeable deep bass boost. Honestly I'm not totally sure they NEED it, it kind of pushes them from "need to dial in a bit more bass" to "need to roll back the bass a bit."
    PawleeP likes this.
  18. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    What kind of power were you using with your EV drivers?
  19. morgan138


    Dec 10, 2007
    A D-180 and/or an old SVT, I forget which I was using more at the time. I don't think it was just the power, just low-tuned bass (B/C) and low-tuned baritone (F/B) in various bands. I could hear them farting out sometimes, and when one eventually blew I figured I'd upgrade.
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    It's possible that the tuning was not correct causing the drivers to unload at low frequencies. The EVM's were pretty robust for the time, but not bullet-proof by any means.