Help me Port this cab! (Kappalite content)

[DukeLeJeune]

For the Kappalite 3015 in 2.28 cubic feet (before subtracting for woofer displacement and port displacement), I'd suggest two 4" diameter ports, each 4.5" long (Edit: That should be 6.5"). If possible, place one port higher than the woofer magnet and one port lower, so that you get a bit of "chimney effect" cooling.

If you really want to get fancy, cut the inner ends of the ports on a 45 degree angle, with the 4.5" length measured along the centerline. This will give you more cross-sectional area at the inside opening because it will be an oval instead of a circle, and more cross-sectional area is beneficial there because that's where chuffing starts.

Use just barely enough internal damping material to keep the cab from sounding boxy. You don't want to overdo it with the damping material.

This will tune the cab to the lower 50's, probably about 52-53 Hz. You'll be roughly -4 dB at the first overtone of low-B, which is pretty good. Your excursion-limited power handling should be adequate as long as you don't boost the lows.

 

[seamonkey]

That's why I want to replace the driver as well. Also, if the ports help increase the bass response, it has the same effect as turning down everything else.

Ports use up valuable air space inside the cab, but you can hang a tube on the outside so you don't loose the volume space. I recall someone once did a pipe organ look with one of the fake pipes being the port.

You'll actually get better to your prediction if you use the appropriate size box for the driver.

 

[matt holt]

For the Kappalite 3015 in 2.28 cubic feet (before subtracting for woofer displacement and port displacement), I'd suggest two 4" diameter ports, each 4.5" long. If possible, place one port higher than the woofer magnet and one port lower, so that you get a bit of "chimney effect" cooling.

If you really want to get fancy, cut the inner ends of the ports on a 45 degree angle, with the 4.5" length measured along the centerline. This will give you more cross-sectional area at the inside opening because it will be an oval instead of a circle, and more cross-sectional area is beneficial there because that's where chuffing starts.

Use just barely enough internal damping material to keep the cab from sounding boxy. You don't want to overdo it with the damping material.

This will tune the cab to the lower 50's, probably about 52-53 Hz. You'll be roughly -4 dB at the first overtone of low-B, which is pretty good. Your excursion-limited power handling should be adequate as long as you don't boost the lows.

Thanks Duke- I was hoping you might chime in. The chimney effect for cooling is a great idea.

So just to clarify, if I cut the port tubes at 45 degrees, part of the tube will extend longer than than 4.5", correct?

Any suggestions for if I were to go with the 3012HO?

 

[DukeLeJeune]

So just to clarify, if I cut the port tubes at 45 degrees, part of the tube will extend longer than 4.5", correct?

Yes, that's correct.

I made a mistake in the port length, looks like somehow I entered the wrong box size into my program at the tail end, and got the wrong port length. The port length should be 6.5", not 4.5". The low-end extension estimate of about -4 dB @ 62 Hz is correct.

Any suggestions for if I were to go with the 3012HO?

The 3012HO will have more top end and less bottom end, and less excursion-limited power handling. I think you'd want a lower tuning frequency to better protect against over-excursion, assuming your bass is tuned to low-B. I'd suggest 9" long ports (still 4" in diameter), tuning the box to about 48 Hz.

I prefer the 3015 (non-LF) over the 3012HO in the bottom couple of octaves, say below 250 Hz or so.

 

[AstroSonic]

Yes, that's correct.

I made a mistake in the port length, looks like somehow I entered the wrong box size into my program at the tail end, and got the wrong port length. The port length should be 6.5", not 4.5". The low-end extension estimate of about -4 dB @ 62 Hz is correct.



The 3012HO will have more top end and less bottom end, and less excursion-limited power handling. I think you'd want a lower tuning frequency to better protect against over-excursion, assuming your bass is tuned to low-B. I'd suggest 9" long ports (still 4" in diameter), tuning the box to about 48 Hz.

I prefer the 3015 (non-LF) over the 3012HO in the bottom couple of octaves, say below 250 Hz or so.

Using the published specs, I find that both drivers are at their best in this cab volume with Fb=52 Hz, which is what you recommended above. however, the 3012HO has deeper bass, and at quite usable power levels. For the 3015, F3 = 65 Hz. For the 3012HO, F3 = 57 Hz. For the 3015, excursion limited power handling drops below thermal power handling (900w) at about 42 Hz. For the 3012HO, excursion limited power handling drops below thermal power handling (800w) at about 46 Hz, but drops to about 620w at 73 Hz (over Fh) in a power handling 'sag' between about 63 and 92 Hz. If we choose a worse case of 620w excursion limited power handling for the 3012HO (280w less than the 3015), then include a 2 db sensitivity advantage for the 3015 (between 150 and 500 Hz), the 3015 will produce about 3.6 db more output in the bass range. If we neglect the power handling sag in the 3012HO and use the excursion limited power handling (equal to thermal) of 800w (above 46 Hz), the 3012 HO will produce 2.5 db less sound. Of course this neglects an thermal compression losses, but these should be fairly close considering the very similar motor structures.

Basically it would appear that the 3012HO has superior deep bass and high end extension (as well as better upper mids dispersion) relative to the 3015 in the same cab, but that the 3015 will produce 2.5 to 3.6 db more maximum output.

With respect to the number of ports, two are needed for chimney effect cooling, and they do keep the mach number near 0.1. The single port I recommended uses up less cab volume (minor difference), but allows the mach number to be double the recommended 0.1. While that might seem a deal killer, it only comes into play over the range of loading - about 47 to 62 Hz. As a full range bass cab there is little probability that a fundamental or second harmonic falling in this range will have more than 20-30% of the total power of the note (fundamental and harmonics). If the note power is at the thermal limit (800w), then the power in the loading range (where turbulence would be generated) is only 240w. If we are generous (but somewhat unrealistic) and call it 300w, then the mach number for the single port is 0.09. At the 620w level the mach number is 0.13 - still pretty reasonable. The latter might be more applicable to the use of the cab as a PA sub, where the power in a fundamental or second harmonic could be equal to the excursion limited power handling (800w in the loading range), and chuffing might be audible.

All things considered, it would seen that the 3012HO has the advantage for a full range bass cab application, while the 3015 excels for a PA sub application.

Of course, I have not used either driver in a cab with this volume and tuning. My guess at what would make or break this conclusion is the thermal compression behavior of the two drivers.

 

[DukeLeJeune]

Astrosonic, you make an excellent case for the Kappalite 3012HO tuned to the lower 50's.

In my experience, a low end that "looks like" the curve we see from modeling the 3015 sounds better for electric bass than a curve that "looks like" what we see from modeling the 3012HO. But it's a juggling of tradeoffs, as always, and you may well be correct that the 3012HO would be the better choice overall.

 

[matt holt]

Using the published specs, I find that both drivers are at their best in this cab volume with Fb=52 Hz, which is what you recommended above. however, the 3012HO has deeper bass, and at quite usable power levels. For the 3015, F3 = 65 Hz. For the 3012HO, F3 = 57 Hz. For the 3015, excursion limited power handling drops below thermal power handling (900w) at about 42 Hz. For the 3012HO, excursion limited power handling drops below thermal power handling (800w) at about 46 Hz, but drops to about 620w at 73 Hz (over Fh) in a power handling 'sag' between about 63 and 92 Hz. If we choose a worse case of 620w excursion limited power handling for the 3012HO (280w less than the 3015), then include a 2 db sensitivity advantage for the 3015 (between 150 and 500 Hz), the 3015 will produce about 3.6 db more output in the bass range. If we neglect the power handling sag in the 3012HO and use the excursion limited power handling (equal to thermal) of 800w (above 46 Hz), the 3012 HO will produce 2.5 db less sound. Of course this neglects an thermal compression losses, but these should be fairly close considering the very similar motor structures.

Basically it would appear that the 3012HO has superior deep bass and high end extension (as well as better upper mids dispersion) relative to the 3015 in the same cab, but that the 3015 will produce 2.5 to 3.6 db more maximum output.

With respect to the number of ports, two are needed for chimney effect cooling, and they do keep the mach number near 0.1. The single port I recommended uses up less cab volume (minor difference), but allows the mach number to be double the recommended 0.1. While that might seem a deal killer, it only comes into play over the range of loading - about 47 to 62 Hz. As a full range bass cab there is little probability that a fundamental or second harmonic falling in this range will have more than 20-30% of the total power of the note (fundamental and harmonics). If the note power is at the thermal limit (800w), then the power in the loading range (where turbulence would be generated) is only 240w. If we are generous (but somewhat unrealistic) and call it 300w, then the mach number for the single port is 0.09. At the 620w level the mach number is 0.13 - still pretty reasonable. The latter might be more applicable to the use of the cab as a PA sub, where the power in a fundamental or second harmonic could be equal to the excursion limited power handling (800w in the loading range), and chuffing might be audible.

All things considered, it would seen that the 3012HO has the advantage for a full range bass cab application, while the 3015 excels for a PA sub application.

Of course, I have not used either driver in a cab with this volume and tuning. My guess at what would make or break this conclusion is the thermal compression behavior of the two drivers.

I will freely admit that I am way out of my league here, and that I probably only Reaalllyy understand about 20% That-but also feel like I got a little smarter just from trying to understand it .

Astrosonic, you make an excellent case for the Kappalite 3012HO tuned to the lower 50's.

In my experience, a low end that "looks like" the curve we see from modeling the 3015 sounds better for electric bass than a curve that "looks like" what we see from modeling the 3012HO. But it's a juggling of tradeoffs, as always, and you may well be correct that the 3012HO would be the better choice overall.

These kinds of interactions are what I love about talkbass

 

[rogypop]

3012ho while flatter overall could sound mid heavy and shy on lows, it all depends on personal taste after all..

 

[BadExample]

I will freely admit that I am way out of my league here, and that I probably only Reaalllyy understand about 20% That-but also feel like I got a little smarter just from trying to understand it .

Those two are superhumans. Probably implanted in our society by alians to help us sound good and be happy, docile and not care about the takeover. There are others here too! Beware

 

[matt holt]

Those two are superhumans. Probably implanted in our society by alians to help us sound good and be happy, docile and not care about the takeover. There are others here too! Beware

if the invasion brings more audiokinesis Cabs, consider me subjugated.

 

[BogeyBass]

speaker response falls after 3k we have a thing called treble knob

speaker response falls below 80Hz
we have a thing called bass knob.

there is little to no cone movement at Fb and cone excursions go way up below fb

looking at a pretty graph and getting a better f3 by high tuning is misleading. it's all port. not electrical reproduction. so you think your getting more bass. yes you are but it's very inaccurate poof of port. by tuning lower you get more accurate reproduction of notes. And likewise tuning high in the 50s puts you at the A string fundamental so the E string at 44 and B string fundamental are causing more overexcursion. the exact reason you decide to low tune the 12. so you could low tune the 15 to 33Hz. but the opinion you get is ohhhh horrible f3 lol but in reality you havea pported system with more accurate note reproduction. And not a false flabby poof of port that looks pretty on a computer screen. the bass is limited to the volume of the box. And in reality any user is gonna boost bass on eq to make up for it. so the low f3 your getting from low tuning is misleading. yes I know the 2nd harmonic is more audible. but the fundamental is still being reproduced by the speaker. high tuning Looks pretty on screen. but you forget sealed cabs roll of around 70Hz but are highly praised for being "punchy" " fast" and accurate" It's ok to tune low at fs of the speaker or even lower. for a more accurate and punchy system. And then the restricted cone movement of the fb of the box becomes like a built in brake to restrict cone movement. it's not based upon program material at 20Hz. it's based on the musical instrument the system is being designed for. a ideal ported system for bass would be fb of 33hz. so E fundamental would be accurate electrical production and low b would be restricted by fb of the box to protect against overexcursion. this is why I sold all my flappy neos cause those speakers all have high resonant frequency around 44Hz with cast frames. a few neos and alot of ferrite drivers have low fs of 33hz and work to make a actual real theile small alignment box. nit this lets look at the pretty picture on the screen and make some "magical" box all based on personal opinion and not true alighments. high tuning for better f3 is annoying
And inaccurate.

 

[pie_man_25]

what about the deltalite 2515? there's a design on the website that recommends 2.3 cubic feet or not much bigger, with an f3 of 66hz.

 

[fnordlyone]

For OP:
pic of the angled ports. I cut the 45's, then measured from center back and cut the straight cuts
pict0123-jpg.390320
Duke… Good!
f!

 

[matt holt]

what about the deltalite 2515? there's a design on the website that recommends 2.3 cubic feet or not much bigger, with an f3 of 66hz.

Hmmm that is also an interesting idea-and saves me some $ and weight. Another driver I spotted was the legend BP-1525; that looks like it would be right in its comfort zone without me having to even port the cab. Anyone have thoughts on that idea?

 

[AstroSonic]

Hmmm that is also an interesting idea-and saves me some $ and weight. Another driver I spotted was the legend BP-1525; that looks like it would be right in its comfort zone without me having to even port the cab. Anyone have thoughts on that idea?

There are many drivers that will 'work' in that cab. How do you decide which to choose? It starts with list of your needs: how loud do you need to play (with or without Pa support?), how much power do you have available (or can you buy more if needed). What kind of tone do you like or play with: mid dominant, fat & punchy bass, thin, articulate bass, etc. The more of this information you can provide, the better we can help.

 

[matt holt]

There are many drivers that will 'work' in that cab. How do you decide which to choose? It starts with list of your needs: how loud do you need to play (with or without Pa support?), how much power do you have available (or can you buy more if needed). What kind of tone do you like or play with: mid dominant, fat & punchy bass, thin, articulate bass, etc. The more of this information you can provide, the better we can help.

Fair enough.
Here is more info:
As a standalone bass cab, I'd like something on the warm, punchy side-I want something that will be in contrast to my Eden 12s, which have a pretty aggressive, modern sound to them. That was what I was originally planning on when I put it together with the beta15 in the first place-and I'm not entirely unhappy with the sound with that combination. As I said though there is a bit more high mids than i'd like, and while I don't need it to be super loud (The Edens have that covered) I'd like to see if I could get a bit more volume than I currently am, which Is why I was thinking i'm going ported with a Kappalite- the kappas are loud for their size, and the specs that eminence publishes on their website seems to indicate that they will at least work in a small ported box. Also they were Tony's recommendation.

Amp wise I'm using either a GK MB500 or MB200.

As for the "PA sub" thing, my PA is really just a couple of powered Yamaha 110s and a 4 Channel Peavey mixer. I'm just looking for something that could fill out the low end a bit so I could engage the built-in HPFs on the yamahas and push them a little harder. While I frequently use the Yammys as montors, I generally only only use the whole PA a few times a year; so if I had a bass cab that could do double duty for that purpose (probably powered by whichever GK I'm not using) it would be awesome. I know that's a bit of a gerryrig, but for the infrequency with which I use the PA, I just don't know that it makes sense to tie up a bunch of money and storage space with an actual PA sub.

 

[BadExample]

For a sealed box, they recommend 1.60–2.20 cu.ft. For giggles, try the no cost option of plugging the ports!

Edit: Just noticed that is for the beta 15A. Same animal?

Edit edit: "A" is all I see http://www.eminence.com/pdf/Beta_15A.pdf

 

[AstroSonic]

So you want to run a single cab to replace one or two 112XLT's volume wise, and have a warm, punchy tone with more laid back upper mids. IMO, you're not going to be able to get that out of the Kappalites without some fairly precise EQ (read parametric EQ). You may be able to make the Beta 15 work: you'll need to have two 4 inch diameter holes that you plug with open cell foam (makes the cab 'aperiodic'). Then place a 5 inch diameter disc of open cell foam (1/2 to 1 inch thick, or egg crate foam with peaks toward the driver) in front of the dust cap (but not touching). To try it, just pin the foam disc to the grill. The foam ports will open up the bass a little, while the foam disc with tame the upper mids. I doubt that one Beta 15 cab will outperform two 112XLT's, but it will come close to meeting your tone goals. OTOH, a pair of Dayton PA255-8's (10 inch drivers) in your 2.28 cf cab, ported- about 55 Hz) will likely produce the tone you are after (probably with only a little EQ touchup) and have about the same volume as a single 112XLT. You would have to cut out all but a flange (like 1 1/2 inch margin) around the outside, and then mount a baffle cut for two tens. I have not seen your cabs dimensions and so am not sure that two tens will fit. Give the Beta 15 a try first...

 

[BadExample]

Nifty! Aperiodic Loudspeaker Enclosure Design

 

[AstroSonic]

For a sealed box, they recommend 1.60–2.20 cu.ft. For giggles, try the no cost option of plugging the ports!

Edit: Just noticed that is for the beta 15A. Same animal?

Edit edit: "A" is all I see http://www.eminence.com/pdf/Beta_15A.pdf

Interesting: Eminence's sealed cab recommended volume for the Beta 15A of 1.6 to 2.2 cf. I've spent some time with this driver and found that below about 2.5 cf sealed, the bass is just too boomy and lacking in upper harmonics, with poor note articulation. At 3 cf sealed the bass tone is much more satisfying: warm and punchy with a nice balance of mid and upper harmonics. Aperiodic loading of the 2.5 cf box produced a marked improvement, though not as good as the 3 cf box. OTOH, that's just my tonal preference. Some folks are pretty pleased with the Beta 15A in a sealed 2 - 2 1/2 cf box. For the OP's box, I would stuff the cab with teased out dacron, in addition to the aperiodic porting.