Help me Port this cab! (Kappalite content)

matt holt

matt holt

Apr 5, 2005
613
596
5,036
Cincinnati OH
www.mattholtmusic.com
#1
Ok Cabinet Gurus:
I have a box (currently sealed) with a vb 2.28 ft3 made out of 3/4" plywood. I've installed an eminence defeat-able 250hz LPF. I would like the cab to serve two functions: a full-range 115 BG cab with the LPF turned off, and a small PA sub with the LPF on.

Most likely going to put a kappalite 3015 in it (although I'm open to other suggestions).
What should I do as far as porting?

Edit: I've never ported a cab before, and am a bit of a noob as far as cab construction, so suggestions on the actual technique for porting/suggested materials would be welcome as well.
 
#7
Why spend money on a premium driver when the cab will not allow you to get the performance that the driver is rightly well known for? Since ultra deep bass is evidently not a high priority, consider the 12 inch 3012HO. It is at its best in a cab like yours, where it will produce deeper bass than the 3015 and be audibly just as loud?
 
#8
rogypop said:
You can put eminence beta 15, delta 15 or legend bp1525 (for more lows bur less mids) and keep it sealed for a punchy old school cab.
Click to expand...

I actually have a beta15 in there right now lol. It works, but the upper mids are a little out of control. I am hoping to find something with a smoother response.

AstroSonic said:
Why spend money on a premium driver when the cab will not allow you to get the performance that the driver is rightly well known for? Since ultra deep bass is evidently not a high priority, consider the 12 inch 3012HO. It is at its best in a cab like yours, where it will produce deeper bass than the 3015 and be audibly just as loud?
Click to expand...

Thats an interesting idea I hadn't thought of. What would you recommend in terms of porting if I did that, and what would be the best method for converting the baffle?

edit PS:the KL 3015 with porting was Anthony Lucas' suggestion, I figure he knows those drivers as well as anyone, although I suppose he does have an incentive to push the high-end stuff...
 
#9
matt holt said:
I actually have a beta15 in there right now lol. It works, but the upper mids are a little out of control. I am hoping to find something with a smoother response.



Thats an interesting idea I hadn't thought of. What would you recommend in terms of porting if I did that, and what would be the best method for converting the baffle?

edit PS:the KL 3015 with porting was Anthony Lucas' suggestion, I figure he knows those drivers as well as anyone, although I suppose he does have an incentive to push the high-end stuff...
Click to expand...

The advice from Anthony will depend on the exact information you provided, particularly for the intended use. Certainly, the 3015 will work fine in that box, albeit, with an early bass rolloff (relative to an optimally sized box). The 3012HO will be operating in a box that is in its optimum performance range with respect to the bass performance it has to offer. However, the 3015 is slightly more sensitive in the 150 to 500 Hz range by about 1.5 db, which may be an advantage for use as a small PA sub (below 250 hz). However, if optimum/maximum bass performance is a top priority the 3012HO is the way to go (between these two drivers).

A shallow EBS alignment, with 52 Hz tuning will yield a response that is shelved down about 2 db between 60 and 100 Hz, but has an F3 of about 53 Hz. It requires a single 4 inch ID port, 1 3/4 inches long, or two 3 inch ID ports, 3 1/8 inches long.

Really, the 3015 is hardly a disaster, especially if you're not overly concerned with deep bass response. A nearly flat response with an f3 of 66 Hz is possible with Fb=54 Hz.

If you have already cut for a 15 inch driver and want to go with a 12, make an adapter plate: cut a 'doughnut' from 1/2 inch plywood, 17 inches in diameter, and with a central hole cut to the mounting size for the 12 inch (11 1/16 inches for the 3012HO).
 
#12
uh well a 15" in that airspace is ideal for a pa Midbass. And you would highpass at 80Hz. And the lows would go to a sub at 80Hz

the 12" or the 15" gonna have the same low-end in that airspace and exactly the bandwidth your working with the 15" would have more sensitivity and flatter mid bass/ mid range.

to port the cabinet use flared round tubes. And the suggested ports so far are way to small and have much
to much vvelocity.

use 2 x 4" ports or 4 x 3" ports depending on how things can fit on the baffle. 2 4" ports will use more space. so using smaller ports helps allows you to easily locate them in each corner. And using four total in each corner will give you enough port area so you don't exceed velocity.

the 3015 does fine tuned to fs or resonant frequency of the driver.
which is around 44Hz if a remember right.
there is absolutely no need to use annoying high tuning in the 50Hz plus territory the box is small and has plenty of power handling
 

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#14
matt holt said:
The eminence website does say the 3012ho will work in a sealed cab this size. Anyone have thoughts on how it might work if I just adapted the baffle for the 12" and left the box sealed?
Click to expand...

Eminence does show plans and modeling results for a 2.5 cf sealed box for the 3012HO. It has a rolled bass response with an F3 of 144 Hz. They call it a 'mid bass cabinet' for good reason. It has no low bass: not what a person would want for a 'sub'.
 
#16
BogeyBass said:
uh well a 15" in that airspace is ideal for a pa Midbass. And you would highpass at 80Hz. And the lows would go to a sub at 80Hz

the 12" or the 15" gonna have the same low-end in that airspace and exactly the bandwidth your working with the 15" would have more sensitivity and flatter mid bass/ mid range.

to port the cabinet use flared round tubes. And the suggested ports so far are way to small and have much
to much vvelocity.

use 2 x 4" ports or 4 x 3" ports depending on how things can fit on the baffle. 2 4" ports will use more space. so using smaller ports helps allows you to easily locate them in each corner. And using four total in each corner will give you enough port area so you don't exceed velocity.

the 3015 does fine tuned to fs or resonant frequency of the driver.
which is around 44Hz if a remember right.
there is absolutely no need to use annoying high tuning in the 50Hz plus territory the box is small and has plenty of power handling
Click to expand...

Agree with the first paragraph. :-)

The drivers will have different low ends in that cab, due largely to the difference in the Vas of the drivers. This is quickly realized after a few minutes of modeling.

The suggested ports are just fine: the high velocities occur only in the range that the cab resonance loads the driver, which is less than an octave. For the suggested 3012HO alignment, this is between about 45 and 65 Hz. Energy in the fundamental rarely exceeds about 20% of the total energy in a 'typical' bass note. Designing ports for minimum turbulence at the thermal power handling limit of the driver is simply misdirected.

If the 3015 is tuned at Fs (45 Hz) in the OP's cab, the low end is substantially rolled off (F3 71 Hz). Tuning low does not always result in more low end than tuning higher.
 
#18
When you go to do the actual port modifications, after the dimensions are planed out, go through the speaker opening with a piece of scrap wood and clamp it to the backside of the baffle the best you can. That way either a spade bit or a hole saw will have far less splintering and blow out on the back side. If you measure carefully, you can mount the scrap wood with screws and holesaw around them too. Don't try that with a spade bit haha. A spiral cutting bit with a circle jig is my preferred method, but its most likely not an option if you're asking or if there is any type of lip on the front of the cab. Good luck
 
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