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Trap Doors/Access Panels - Pros? Cons?

Discussion in 'Luthier's Corner [DB]' started by turf3, Nov 21, 2018.

  1. turf3


    Sep 26, 2011
    I have had my bass about 5 or 6 years so far, and so far have not had to deal with anything around the sound post. However, from everything I read, it seems like sooner or later everyone has a sound post drop. Plus, people are forever experimenting with sound post adjustments.

    Rather than doing the ship in a bottle thing, it occurs to me to have an access panel installed. This is what I would think of as a "medium-quality workshop/factory bass"; a Romanian no-name, probably from the Gliga factory, all carved.

    Most important question would be: Are there any defined negatives to having a trap door? Other than possibly affecting the resale value, I mean.
  2. A fallen post or making adjustments is a bit fiddly and needs to be done with care but is definitely not rocket surgery . The tools required don't need to cost much and if you learn how to do it yourself, you'll have a skill for life.

    I can't guarantee that you wouldn't regret devaluing your nice, carved instrument with an access panel though.

    Edit: The real luthiers will be able to better answer your last question but the problem that comes to mind caused by the trapdoor is the potential for introduced rattles/buzzes

    Last edited: Nov 21, 2018
  3. eh_train

    eh_train Supporting Member Commercial User

    Jan 12, 2004
    Owner, Stand Up Guy Basses (Repair/Sell/Buy upright basses)
    I don't think that setting or adjusting a soundpost is comparable to a "ship in a bottle thing". Not that I've done the latter, but I think those folks are trying to convince a whole bunch of rigging to stand up and look convincingly/cosmetically like the real thing.

    In setting a sound post, you're doing two things: cutting the post to the right size, and making it fit in the correct place (and yes, the correct place can be up for discussion depending on the desired sound).

    You really don't need an access panel to get this happening. And, as Tiern says, it would devalue your bass, and potentially cause rattles. Finally, a properly fit post shouldn't fall down, unless you take off all the tension at once (which usually isn't necessary). You've said yourself that you've had your bass for 5 or 6 years, with no soundpost issues. My suggestion is, if it ain't broke...
  4. I think they are more about getting to top cracks and the bass bar. I've considered it.
  5. The instrument is 500 years old. People started cutting access doors in basses quite recently, like they’re cars or some foolish thing.

    Setting an already-fit soundpost is not especially hard in the grand scheme of things. Fitting a new post is where the violin-school voodoo training comes in.

    I have an Ullman bolt-grabber. It looks like Dr. Octopus’ flexible arm and cost me $8.

    It grabs, it twists, it was made in America and it’s so much better than the standard tools that are barely useful.
  6. GretschWretch

    GretschWretch Supporting Member

    Dec 27, 2013
    East Central Alabama
    I went a similar route. The first time a soundpost drops and I have to fish it out, I adhese a very small metal washer to the center of the post, not enough to affect its response but large enough that one of those flex grabbers with a magnet on the end can grab it. It's like a lazy man's bolt-grabber.
  7. dhergert

    dhergert Gold Supporting Member

    Jan 17, 2018
    Blue Zone, California
    As many of you have seen with my posts about it, my Alcoa bass came to me with a hinged trap door, put in place long before I owned it. The bass needed top repairs and being aluminum and welded together from the factory, a trap door was realistically the best way to make the repairs. At the time of these repairs the bass back was also treated with acoustic paint to reduce the metallic tone. But anyway, I didn't have any decision making related to the presence of the trap door, with the exception being whether or not to purchase the bass for myself.

    As some have mentioned, there is a possibility of rattle with a trap door... Mine having 2 hinges riveted onto it means there are moving parts that can become loose. I've been lucky enough to find ways to prevent rattle there, but this being a metal bass with temperature expansion and contraction, things can become loose. I have considered and probably will eventually replace the rivets holding the hinges in place with tension bolt and lock nut assemblies, but for now I have eliminated rattle at the hinges with heavy duty velcro and I'm satisfied with that for the time being.

    Regarding rattles and access doors though, our own James Condino has described and shown some rare-earth magnetic clasps that hold his access panels closed with no rattle and no moving parts... That seems to me to be a very good idea.

    As an owner of a bass with a trap door, I've found it very useful for a few things, and if I were ever to have a new wooden bass commissioned I'd probably request a trap door be installed...

    As has been discussed, the sound post is a primary reason. For me, having access to the sound post has provided a way for me personally to replace and subsequently to tune my adjustable sound post whenever I want to, rather than having to take it in and describe what I want to someone else. This is not at all to denigrate the value of having a luthier examine a bass, but for me it has been really handy to be able to do this kind of tweaking on the fly and without tools.

    Another thing that is handy with a 7"x7" trap door in the driver side C is that it can be left open, providing a sizable sound hole pointing basically at the player. I've attached heavy duty velcro to points where I can keep the trap door open while playing for this purpose. I (and others) can actually hear the difference in both tone and volume, so I'd guess we're talking about at least a 10% difference with the door open. All this said though, if I were going to put a trap door in a bass exclusively to use as a driver-side sound hole, I'd place it in the upper driver-side bout, nearer to the player's ears.

    Other than that, I've had some fun with leaving the trap door open for my cats to play inside... They love it. I don't know if I would do that with a more standard wood bass, but mine is pretty battle-worthy as it is setup inside and the cats can't really do any damage there. And it's fun to take pictures of them playing inside.

    Of course there is the theatrical side of a trap door in a bass... I've heard of some players keeping their drinks or other things inside. That isn't probably something I'll ever end up doing though.

    That said, when looking inside my bass there isn't really a lot of other interesting stuff besides air and dust... Although I did once find a loose washer rattling inside, it was nice to be able to easily remove that. The bass bar is actually part of the top, and it probably isn't moving for at least another century. I can see the neck block and the neck attachment welds which need no maintenance... And I can see the end block and endpin plug from inside; I may replace both the endpin and plug one day, but I'll do that work from the outside of the bass. Other than that, there are a few manufacturer markings in a few areas which are interesting to see, but certainly not worth installing a trap door just for those.

    Regarding a fine antique wooden bass, I don't know if I'd have a trap door installed. Even if done expertly and tastefully, provenance is still a possible issue. If it's a nice old bass that I'll never sell, perhaps I would consider it more, but I'd have to not be worried at all about resale value. On the other hand, a trap door could sure make top and rib repairs easier on an older carved solid wood bass.

    Last edited: Dec 15, 2018
    T_Bone_TL, Tiern and Earl like this.

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