Need help designing Xover for 2x15 +MT Bass Guitar Cabinet

[nodestiny]

Hello gang!

Im planning on putting together the following...

2x Eminence Kappalite 3015LF Neo 15" Driver (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-598&FTR=eminence%203015lf&CFID=9143281&CFTOKEN=41250777)

1x Eminence Alpha-6A 6" Midrange 8 Ohm (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-400)

1x Eminence APT-80 Super Tweeter with 80° Conical Horn (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-532)

I plan to do the two 15"s in parallel to get a 4ohm load (as my amp, Mesa Boogie BB750, is rated 750 Watts @ 2 Ohms, 550 @ 4, and 280 @ 8). I want to do a 12db/oct Xover for both the mid and woofer and 18db/oct for the tweet, probably 500 and 5K, roughly.

There are a few things about the Xover design I don't know about. One of them is L-Pads. I want to be able to adjust both the midrange and the tweet independently. I found this (100 Watt Speaker Control Panel (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-240)) but since I have only ever done basic crossovers, I didn't know how to go about choosing the right Lpads for them.

Also, another thing I commonly see in these crossovers that are pre-built. Tweeter fuse bulbs. I see I can order the bulbs, but was not sure about mounting/connecting them. I also noticed that all the Xovers with them have them obviously on the tweeter circuit, but first thing on the positive side. Am I correct? Can these simply be added in without any needed calculations or further planning?

Finally, with as much power as these are going to see (550w!!!), I have never built a Xover that was designed for such power. Im assuming I want to up to a rather high gauge on the woofer inductors, but is there anything else I should note?

You guys taught me much in the past! Hope this trend hasn't changed ;)

[wg_ski]

I don't think you'll want to put an L-pad on that midrange. L-pads are troublesome - they have a nasty habit of burning up at levels a PA or instrument amp can put out in the midrange. The A6 is only 93dB, and I doubt that it will be too forward with two woofers. I might even go for something with more kick myself. I can see using an L-pad on the tweet - use a big one, though. The light bulb tweeter protectors are always a good idea. Wire them in series and take the cold resistance into account when tuning the crossover up.

For crossover inductors, think iron core. Steel laminate is fine for this app. The caps require some consideration as well - cheap NP electros can and will explode. Polypropylene can get expensive but will give the least problems. If you do use electrolytics for the 500Hz x/o, try to get ones designed for switch mode power supplies because they can handle high currents and build your own bipolar with two back to back.

[billfitzmaurice]

Hello gang!

Im planning on putting together the following...

2x Eminence Kappalite 3015LF Neo 15" Driver

-1. If you don't have at least 700 watts/4ohms available there's no benefit to using two 3015LF. A pair of standard 3015 will take more power than your amp has to give, and with their higher sensitivity will be louder. A single mid and tweeter won't be able to keep up with two woofers either, you need two of each. Make life easier all around by building two 1x15 3-ways, which also allows you to run an Eminence PXB crossover. After building the first cab you'll likely as not find no need for a second.

[nodestiny]

Thank you for the replies!

wg_ski - I definitely want to do it right the first time! So I will probably find a more sensitive midrange and use resistors to quiet it down if it gets too loud. I see 100watt adjustable L-pads on partsexpress, would that be enough for the tweet you think? Also, you mentioned the cold resistance of the bulb when considering the Xover... can you further explain please? And I will definitely spend the money on good crossovers! Do you have any specific ones you would recommend from partsexpress? Again, I have built home theater Xovers that take ~100w, but since these will see ~550w, I want to make sure its built like a tank!

billfitzmaurice - Currently I have a 4x15 cab @ 8 ohm and its just loud enough for our practice room, but not enough low end and I fear in a large open area w/ the rest of the band on the PA system, I would need more. I realize there is NO way to get enough power to these with my current amp, but working with plenty of drivers in the past that don't get quite their RMS, I'm sure ill get plenty out of these. I want to do 2 simply for headroom. I might not EVER need it, but I would rather have it and not need it, then need it and not have it ;)

On top of that, pre-built crossovers are more expensive and are not specifically tuned for the speakers in plan (to my knowledge, though they seem to be pretty generic use... probably would work fine, but if I'm going to do it, might as well do it the best I can!).

Though I will put into consideration bumping up the midrange/treble somehow. Though, I don't want 2 separate cabs, rather, one large and heavy setup. I plan to put flush mount casters on it and wheel it around VS having to carry multiple cabs. Edit: Actually, I may just start with your suggestion and build one for now and play around with it and see what it can do first ;) I guess I just want the "ego" boost of a monster of a bass cab :D

Edit (again):
The more I think about it, the more I have decided I will just do 1 for now. I can build my monster later if I want :D So anywho, back on the topic of Xover design...

[nodestiny]

Another thing I was thinking about: How much heat are these Xovers going to take? Would it be worth using the port to get some air moving over them?

[wg_ski]

I would get a midrange that is the right sensitivity to begin with - using resistors to tame one down gets back to the same problem of overheating Lpads. In the end, you'll actually have a hard time finding a single 6 or 8" mid that would overpower two 15's anyway. A couple dB less sensitivity in the mid is not a bad thing, but not so much it gets swallowed. Two A6/Beta 8 or one B&C 8PE21 would be what I'd be trying.

100 watt Lpad is what you want on a tweeter. When they're turned way down, they can only handle a small fraction of that 100W. As for the light bulb, it will have a couple ohms resistance when it's not lit (limiting). If you're building your own x/o, it needs to be tuned for this higher resistance. I build all my own x/o's becuase there's enough improvement over a pre-built to justify it. And since I wind my own coils (on steel laminate or ferrite bobbin cores) with #17 or #15 wire overheating at 500+ watts is no issue.

[nodestiny]

Excellent info, thanx much!

One last question: Is there a great site for learning on crossovers (or maybe a book?) that goes more into details such as adjustable L-pads and the fuse bulbs (and Im sure much more)? Just looking around online I could not find much info on anything but the basic 1st-4th order and a little on other things such as basic L-pads and zobels.

[billfitzmaurice]

billfitzmaurice - Currently I have a 4x15 cab @ 8 ohm and its just loud enough for our practice room, but not enough low end and I fear in a large open area w/ the rest of the band on the PA system, I would need more.
If your 4x15 isn't loud enough for stadiums without PA support it must be a pretty poor 4x15. Not to mention ungodly large and heavy. OTOH you shouldn't need something large enough to drive a stadium without PA support, that's why they make PAs. You only need a rig large enough to drive the stage, the PA drives the room. All you'll accomplish with a silly large rig is to be too loud on stage, making the rest of the band upset, and too loud out front, making the FOH engineer upset.
I guess I just want the "ego" boost of a monster of a bass cab Poseurs need big cabs. Professional musicians leave their ego at home.

[nodestiny]

If your 4x15 isn't loud enough for stadiums without PA support it must be a pretty poor 4x15. Not to mention ungodly large and heavy. OTOH you shouldn't need something large enough to drive a stadium without PA support, that's why they make PAs. You only need a rig large enough to drive the stage, the PA drives the room. All you'll accomplish with a silly large rig is to be too loud on stage, making the rest of the band upset, and too loud out front, making the FOH engineer upset. Poseurs need big cabs. Professional musicians leave their ego at home.

Bwahaha! TYPEO!!! I meant 4x10! Sorry about that!

Really though, again, its not about actually driving it to the max. Its the capability of turning up the volume when it may be needed. I expect the PA system to do wonders of course, but that doesn't mean I don't want the option to independently have great output. My current 4x10 cab barely keeps up with my guitarists 2x12 cab currently, and he is planning 4x12 shortly, leading to obviously more challenge for me. The 4x10 has served its purpose for many years and its time to move on.

[billfitzmaurice]

My current 4x10 cab barely keeps up with my guitarists 2x12 cab currently, and he is planning 4x12 shortly, leading to obviously more challenge for me. The 4x10 has served its purpose for many years and its time to move on.Let me guess, said guitar'd player thinks he's Jimi Hendrix reincarnate. There's been no logic to the 4x12 since the invention of 100 watt drivers and real PA systems, ie., roughly 1975. Where musicians in general tend to be, shall we say, less than well informed when it comes to the physics of sound, most guitar players are clueless to the Nth degree.

The main deficiency with 4x10s is the 4x arrangement; a pair of vertically aligned 2x10s using the same drivers in the same net box volume works much better, with twice the horizontal dispersion angle in the mids, and with the drivers closer to ear level so you can hear the mids rather than have them pass you by at waist level. Keep that in mind when designing your box, tall and narrow with the mid and HF drivers as high as possible is far better than short and squat.

[Mipsconsult]

"There's been no logic to the 4x12 since the invention of 100 watt drivers and real PA systems, ie., roughly 1975."

Amen brother.

ALL of the pro guitarists I know and respect are using 30-40 watt 1x12 or smaller rigs.

Most pro bassists are using 500 watt SS amps with a quality direct out to the PA with vertical 2x10, 2x12 or conventional 1x15 cabs.

Face it, 99.9% of our work is in small to mid-sized clubs where 30 watt 1x12 amps are still a bit on the loud side.

For larger rooms, I recommend 2x12 or 2x10 vertical extention cabs. These are NOT for additional volume but for dispersion when a PA boost is impractical.

For anything bigger (as in the rare shed or auditorium gigs, they rent bigger SR systems, not bigger instrument amps.

You see, it's ALL about tone....not volume.

Only the cluless hold tight to their 4x12's.

[nodestiny]

Again, thanx for the input doods.

No, he thinks he is Dimebag Darryl :cool: He wanted to go all Krank gear and I told him just to buy the drivers and well build an enclosure in order to save... well... a ton of money.

Ill take all the advice you guys give, though! I'm all about tone, no doubt. Hence, why I went to a Mesa Boogie BigBlock 750 ;)

[steve22]

For a bass guitar cabinet I would probably use a two way design. Your woofer is a good choice and it can play up to about 2kHz if it is not down at your knees. A big woofer does not have much dispersion at in the upper midrange frequencies.

Or a 1" throat compression driver like, Eminence PSD:2002S-8 1" Titanium Driver, Sku 290-446

or

Eminence Alpha-8MRA 8" Sealed Back Midrange, Sku 290-402

[wg_ski]

Or a 1" throat compression driver like, Eminence PSD:2002S-8 1" Titanium Driver, Sku 290-446

or

Eminence Alpha-8MRA 8" Sealed Back Midrange, Sku 290-402

Instrument amps tend to have lower peak-to-average ratio than a PA that's being fed the entire mix. If you go crossing a 1" comp driver low on an instrument cab, you'll be toasting it. A high power cone mid will take the $** that happens a lot more gracefully.

I don't know why everybody seems to recommend that sealed 8" mid. Maybe because it's easy, cheap and loud - but it doesn't have the best tone. Eminence's standard 8" drivers sound so much better.

[billfitzmaurice]

I don't know why everybody seems to recommend that sealed 8" mid.Probably because even a mediocre 8" mid still works far better than going without one, it's reasonably priced, and it doesn't need a sub-enclosure. The LA6CBMR is better, for only a few bucks more. Prices on European sealed back mid drivers are out of sight.

[nodestiny]

Yeah, looking at the response of the sealed back 8" VS the eminence 6", I would say I would rather go with the eminence 6" to be honest... it wouldn't take much for me to build a small sealed enclosure inside the cab.