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  • how large should bass drum ports be?

    my bass drum is a 22x18 and currently have a 4-inch port on the reso head. i've heard of 4.5 and even 7 inch at the center or to the side. which one is the best? is there a golden ratio to this?

    i wanna maximize the low end of the bass drum... kinda like the ports on the subwoofer of your home entertainment system where, when you listen near the port hole, the sound is massive compared to listening to the driver itself.

    so how large should the ports be to have the same effect?
    spreading some love

  • #2
    well ideally you wouldn't have one. ports tend to deplete the resonance of the drum, which then by reducing the resonance, you end up with more high-end punch.

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    • #3
      Well, that's not what a bass drum port really does.. in actuality, it's just letting the sound pressure out of the drum, which does a couple of things in real life:

      1) It allows for pressure relief. This is good for most people, it makes the beater a little "deader", so you have less bounce back from the drum.

      2) You will have LESS bass response than an un-ported drum. This is because the amount of surface area that is resonating is directly proportional to the amount of "low-end" you hear from the drum. Now, this is not a bad thing - by cutting a hole in the head, you will hear more of the beater, i.e. more attack. This is the "modern" sound.

      As far as the hole size goes.. the bigger the hole, the less bass you will get. For non-mic'd situations, I use an ambassador reso with 2 2" ports. This is great for maximum volume, resonance, and tone from the bass drum. Sounds great and projects well. But for mic'd or rehearsal situations, where I don't need a ton of volume from my kick, and am more looking for a controlled, "attacky" sound, I use a 5" offset hole. This also allows me to adjust any muffling I have inside (typically just an EQ pad), and the microphone as well.

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      • #4
        7 inch hole offset not center. Placing the hole in the center makes the bassdrum eeven more dead because the trapped air inside the shell escapes easier thus releasing the energy quicker and not letting the shell resonate a little bit more.
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        • #5
          I hate the feeling of drums unported... the Aquarian regulator hole is the perfect size for me.
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          • #6
            If you still want some tone from the drum keep the port small and off-center. When you use a large port in the center the sound is pretty much the same as having no reso at all: tone-free.

            If you want a bassier sound go with no port. The hole in a reso head and the ports in some speakers serve two different purposes, apples and oranges. A port in a bass drum does not "let the bass out," it diminishes bass and resonance.

            If you play out miked you need a port. To reduce its impact on bass and sustain keep it small (4") and off-center at around 4 or 8 o'clock. Use whatever muffling inside the drum you need to cut sustain.

            But if you play out unmiked leave the reso unported; you need all the bass and sustain you can get to cut through the band.

            I keep both on hand depending on the gig.
            Pearl ECX

            New to tuning? Check these out:

            Tuning toms Tuning Snares Tuning bass drums Why reso heads are important

            Too much snare buzz? See this, then this.

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            • #7
              Originally posted by drumtechdad
              If you still want some tone from the drum keep the port small and off-center. When you use a large port in the center the sound is pretty much the same as having no reso at all: tone-free.

              If you want a bassier sound go with no port. The hole in a reso head and the ports in some speakers serve two different purposes, apples and oranges. A port in a bass drum does not "let the bass out," it diminishes bass and resonance.

              If you play out miked you need a port. To reduce its impact on bass and sustain keep it small (4") and off-center at around 4 or 8 o'clock. Use whatever muffling inside the drum you need to cut sustain.

              But if you play out unmiked leave the reso unported; you need all the bass and sustain you can get to cut through the band.

              I keep both on hand depending on the gig.
              ^Exactly!
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              • #8
                http://home.earthlink.net/~prof.sound/id6.html
                Originally posted by Prof. Sound
                Holes in Your Head or Not


                Here are the basic concepts:



                · Any hole larger than 7” is like having no head at all on the drum.



                · A 7” hole creates the feel of a one-headed kick drum, feeds more beater attack direct to an audience and provides some of the tone of the resonant head. Further, it’s easy to position a mic and change internal muffling devices, if used.



                · A 4-1/2” or 5” hole, or even 2 such holes, offset, allows some relief for rebound control of the kick beater, contains more of the drums resonance so that the resonant head is more pronounced in the tuning of the drum. A 4-1/2” hole is difficult to get large mic’s positioned within (but can be done) and/or internal muffling altered.



                · No hole, very resonant, creates more bounce or rebound from the kick beater. It can become difficult to get the “slap” of the beater and resonance of the drum both when miced with one microphone. The muffling remains inside. The resonant head is very predominant in the overall sound.



                There are usually four reasons why drummers want a hole (or multiple holes) in the bass drum:



                · It looks cool.

                · They do not like the feel of the beater on the batter head surface, it bounces as a result of not enough air relief.

                · They need to mic the drum from or capture the sound from the inside.

                · They want more projection without using a mic (less bass impact, more beater attack presence).



                For those who want it because it looks cool, there is an acoustic impact on the sound by placing a hole or holes in the resonant side. By acoustic impact I mean that the removal of head material does affect the bass portion of the note coming from the drum.



                Allot of the “bass” portion of what you hear is based upon the surface area in the center of the drum. That surface area is a diaphragm working much like a speaker radiator might work, in that it will aid in moving air. Remember that pitch is dictated by the tension and the surface area in movement. So if you remove a large center portion, you lose a large portion of the bass reinforcement that gets emitted by the heads movement and tension usually has to increase to compensate for the removal of the center area. Adding holes does not increase bass content as might be the case on a tuned vented speaker cabinet would.



                Thicker heads tend to stay in motion longer. With loose tension they will vibrate at a lesser rate, which all translates into lower pitch and a longer resonance. This assumes no internal muffling, or other devices to make the head stop its vibrating motion sooner.



                Some want the different feel created by having air relief but still want maximum bass affect. As you remove more head area you trade off deep bass for a different feel. A solution is using smaller holes placed around the perimeter of the head. If you want the mic to capture sound from inside, you either have to resort to say the May mic system or revert to a larger hole to get the mic into the drum as you require. What you ultimately do will be based upon the balcance of all the factors that are important to you.



                It is the area of the hole that counts. Where it is located matters little for the affect on sound (as long as it isn't on the batter side). If you want maximum tone out of the head, then the size of each hole needs to be in the 1-2” size, and they need be placed closer to the perimeter, but not placed so the edge of the hole is closer than about 1” to the break for the bearing edge. In other words, for the best tone, you need to keep as much of the center of the resonant head intact as possible. And again, it’s not the number, it’s the area displaced that can make a big difference and where that area is removed. You can make any number you want, in the following example to illustrate the concept we'll make two holes to represent the maximum area displaced by a common 7 inch hole.



                The math is simple. We first need to calculate the area of a 7” hole. To do this we use the formula Pi(R²). So first find half of the diameter of the 7" hole (the radius), which is 3.5”. Now multiply that times itself. So 3.5 x 3.5 = 12.25. Then take this result of 12.25 and multiply it times Pi, which is 3.142. So we now have 12.25 x 3.142 = 38.5. So the area of the 7 inch hole we started with is 38.5 square inches. This 38.5 sq. in. is important. We will simply round it up to 40 square inches, cause close is enough.



                Now we can use any number of holes as long as is does not cumulatively exceed 40 square inches of total area. Yet at the same time does equal 40 square inches. This will be the same air relief as having one 7” hole and the end result will be more center surface are and a stronger bass affect.



                Now take the 40 sq. in. and divide by 2, 3, or 4, what ever. Let’s say you want 3 holes. 40 ÷ 3 = 13.33. So 13.33 is the maximum area for each of the 3 holes. So we now take the 13.33 ÷ Pi (which is 3.142) = 4.24. Now extract the square root (from a math table or calculator) of 4.24 and you get 2.06. So 2 x 2.06 = 4.12. This means 3 holes of 4.12 diameter will give the same acoustic result as a single 7” hole.



                Let’s say you have1 hole of a diameter of 4.5”, a common bass drum hole. Let’s compute the area displaced by that single 4.5” hole. (Math: 4.5 ÷ 2 = 2.25, THEN 2.25 x 2.25 = 5.0625, THEN 5.0625 x 3.142 = 15.9). A 4.5” hole has an area of 15.9 sq. in.



                In the above example we show that if we were to use 2 holes of 4.5”, the cumulative affect will have less area (31.8 sq. in. total) than that of a single 7” hole, whichj we learned was about 40 sq. in. The 2 – 4.5” holes will therefore be a little more bass heavy than will a head with a 7” hole because they do not remove as much of the heads surface, although you probably will not hear it.



                As the bass drum is equipped with a solid resonant head, it will always sound warmer or more bass heavy. The smaller holes are designed to allow relief yet still allow the resonant head to resonate. As you cut away more of the head there is less to resonate.



                More large holes will make the drum a little louder and more present out front. Smaller holes around the perimeter gives better feel but the drum retains warmth.



                So if you want more acoustic impact from the resonant head itself, create less “hole” area.
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                • #9
                  ^^ I thought I said that!

                  This is why I seldom recommend the DTB to n00bs; guy has done us a great service, but he needs a friggin' editor.
                  Pearl ECX

                  New to tuning? Check these out:

                  Tuning toms Tuning Snares Tuning bass drums Why reso heads are important

                  Too much snare buzz? See this, then this.

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                  • #10
                    Well I have 2 5" offset ports symmetrically placed on the head. I did it for 4 reasons... (as stated)

                    It looks cool (1 looks weird)
                    It feels better to me
                    It has more attack and punch
                    I do mic it, and plan to mic it.

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                    • #11
                      Well, if you don't really care too much about sound, you can make them as big as you want. Of course, it could sound like poo, but hey... It's your head.

                      But seriously... I currently have a 5" port, at about 5 o' clock on the reso. The head I'm looking at getting to replace my current head is the Aquarian Regulator, I think... It's got a 4.75" hole, at about 3 o' clock on the head. That should be big enough.

                      In my opinion, 6" is too big. Unless you're rockin' a 26" kick... But for most situations, a 4" should be fine.
                      absent and not always accounted for.

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                      • #12
                        i had a question about porting toms and such and monday317 gave me a reply about the proper size of port holes. it's pretty similar to what killerbobbarker quoted from Prof. Sound but it's still good stuff.

                        Originally posted by Monday317
                        Placement--Holes generally should not be centered on the drumhead, but offset. You lose quite a bit of tone from the drum when you remove much of the center of the reso head. I would consider placing the hole toward the front (audience side) of the drum to get maximum projection from the batter head through the reso head. Cut the hole as close as possible to the bearing edge--but not so close the hole touches the crown of the head where it meets the drum. Maybe 1/2" in from there.

                        Size--P. S. felt that a hole whose diameter exceeds 7" will give the same effect as no reso head. I'm not sure where I was told this, but he was referring to a 22" bass drum. A 7" hole will have an area (A=πr2{squared; I couldn't find a damn HTML tag that would work...}--now you know why they taught you that stuff in school! ) of 38.48 square inches. As a 22" BD head is 380.13 square inches, we don't want the area of our tom's reso head hole to exceed 10% of the total area of the tom's reso head.

                        That means an 8" tom should have a reso head hole no larger than 5 sq. in.; a 10" tom shouldn't have more than a 7-3/4 sq. in hole and-- OK, here's a table:

                        08" tom use a ≦ 2-1/2" diameter hole
                        10" tom use a ≦ 3-3/32" diameter hole
                        12" tom use a ≦ 3-25/32" diameter hole
                        13" tom use a ≦ 4-3/32" diameter hole
                        14" tom (or snare) use a ≦ 4-15/32" diameter hole
                        15" tom use a ≦ 4-3/4" diameter hole
                        16" tom use a ≦ 5-1/32" diameter hole
                        18" tom (or bass drum) use a ≦ 5-11/16" diameter hole
                        20" bass drum use a ≦ 6-5/16" diameter hole
                        22" bass drum use a ≦ 6-31/32" diameter hole
                        24" bass drum use a ≦ 7-19/32" diameter hole
                        26" bass drum use a ≦ 8-7/32" diameter hole
                        28" bass drum use a ≦ 8-27/32" diameter hole

                        Remember these hole sizes are the maximum size recommended for the head to still affect the drum's sound. You may use multiple smaller holes, so long as the total areas don't exceed the 10% area limit. You simply divide the maximum diameter by the number of holes you want to use and cut 'em into the head, just be careful of placement (see Placement).

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                        • #13
                          I prefer a 4" or so hole off center. I currently have a EMAD reso and it has a 4" hole with a foam ring on it. So far that is my favorite reso head I have used.
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                          • #14
                            I just ordered an Aquarian Regulator 22" black head with the 4.75" offset hole.

                            I'm excited.
                            absent and not always accounted for.

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                            • #15
                              I have a 4" port at 6:00 on my 22". I like it, I still get a good amount of resonance and it makes micing really easy.
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