Full Range-ifying a custom 115 cab

[Patman27]

Hey all,
I'm thinking about adding a 6"-6.5" midrange driver to my custom-made 115 bass cab. (mentioned here. Because it's impossible to build a separate enclosure for a new driver, I guess I'll have to go with a sealed midrange driver. Here's what I've dug up so far:

http://www.parts-express.com/pe/show...number=292-208 - SPL seems too low for my 100.2db/1m Eminence Kappalite 3015LF

http://www.parts-express.com/pe/psho...82&ctab=1#Tabs - Although the SPL is closest to my 15", it only takes 100w total

http://www.parts-express.com/pe/psho...42&ctab=1#Tabs - greater power handling, at the cost of a lower SPL

Assuming cost isn't a factor, which of these would, in the opinion of the masses, be the best match for a 15" Kappalite? How would I wire the crossover to only route 150w max to the midrange driver?

Thanks in advance!

[kesslari]

May I suggest building a fEarful Headcase? Keep your 115 intact and simply add the crossover, mid, and optional horn in the Headcase. Then you could use a better driver.

[Patman27]

True. Then again, to make my existing cab full range, I could simply cut a hole and pop the driver in. Relatively cheap and painless. A headcase would mean more weight, cost, complexity, etc.
I guess what I mean to say is, how much better will a headcase sound than one of these sealed mids and a good crossover? (assuming I can make a good crossover)

EDIT: I forgot to mention that my Kappalite is currently running Full Range. I need to fix that, but I'll make a separate thread for my crossover questions.

[Patman27]

Also, it seems fEarful cabs are quite the staple of the DIY cab builder. Are they REALLY that good?

[Passinwind]

Originally Posted by Patman27

How would I wire the crossover to only route 150w max to the midrange driver?

With how much power available to the whole system? Why can't you retrofit a sub-enclosure? And what is the internal volume of that cab?

Kesslari's suggestion would save you a lot of headaches, since you could just use greenboy's crossover design and not have to sweat doing your own. I have built three different styles of headcase myself (my own designs though), and am very happy with all of them. Best of luck, whatever you decide to do.

[Patman27]

Originally Posted by Passinwind

With how much power available to the whole system?

Ah, sorry. Forgot to mention that; Carvin BX600 Mono bass amp, 600w into 2Ω. When I connect my SWR Goliath Jr, III (8Ω) and my custom 115 (8Ω), it goes down to the minimum of 2Ω.

As far as headaches, I need a crossover for my Kappalite 3015 anyway, because right now it's not sounding so good full-range. I figure if I just mount a sealed 6" in my existing enclosure, then it simplifies it quite a bit. Only one crossover, no more enclosures, etc.

Does Greenboy have crossover designs up?

[Passinwind]

Originally Posted by Patman27

Does Greenboy have crossover designs up?

They are in the fEarful Wiki, along with some generic commercial ones you can just buy. The 15/6 CBG design will not work correctly with a sealed mid driver though, it is meant for the 18Sound 6ND410.

Building a sub-enclosure is really simple compared to the cab build you just did though, what's the hangup?

When you connect two 8 ohm cabs, you have a 4 ohm load, not 2 BTW.

[Patman27]

Originally Posted by Passinwind

When you connect two 8 ohm cabs, you have a 4 ohm load, not 2 BTW.

Now I know why I said 2 ohms instead of 4. that's the measured DC resistance, not the marked resistance. According to my multimeter, the Goliath and custom cabs go down to 2.6 ohms.

[Passinwind]

Originally Posted by Patman27

Now I know why I said 2 ohms instead of 4. that's the measured DC resistance, not the marked resistance. According to my multimeter, the Goliath and custom cabs go down to 2.6 ohms.

You don't measure impedance that way though, that's the DC resistance of the voice coils. You're not running DC through the cabs, bass signals are AC. You are looking at a 4 ohm nominal load, and an amp that is spec'ed at ~400 watts at 4 ohms.

Anyhow, many guys on Talkbass have made sub-enclosures out of plastic containers like say a cottage cheese one, glued into the cab. I would go a little nicer and make a 5 sided box and screw it in from the baffle side, or use pocket joints from behind, or even just glue it in and clamp it or weight it through the hole for the 15 until the glue sets.

[Patman27]

Originally Posted by Passinwind

Anyhow, many guys on Talkbass have made sub-enclosures out of plastic containers like say a cottage cheese one, glued into the cab. I would go a little nicer and make a 5 sided box and screw it in from the baffle side, or use pocket joints from behind, or even just glue it in and clamp it or weight it through the hole for the 15 until the glue sets.

Then again, this would subtract from the interior volume available for the 15", changing the speaker characteristics. Wouldn't even a .7ft^3 box, for example, have a considerable effect on the sound?

[Passinwind]

Originally Posted by Patman27

Then again, this would subtract from the interior volume available for the 15", changing the speaker characteristics. Wouldn't even a .7ft^3 box, for example, have a considerable effect on the sound?

Yes, but you would be looking at a much smaller figure than that! Look at the fEarful mid chamber dimensions and do the math...I get ~0.14 cu ft.

Again, what is the actual internal volume of your cab right now though?

[Patman27]

I hadn't even really looked at the specs for the mid box yet.

My cab has approx. 5.1ft^3 as of interior measurements. Subtract volume for the port (assume .15 ft^3) and the speaker (you figure it out ) then 4.x ft^3

[DukeLeJeune]

Originally Posted by Patman27

...SPL seems too low for my 100.2db/1m Eminence Kappalite 3015LF...

Once you've built a proper low-pass filter for the 3015LF, it's more like a 96-97 dB efficient driver. This is because, in the interest of clarity, you want to cross over well below that huge 1.2 kHz peak and/or suppress it aggressively. Just a thought, as you look at a DIY crossover.

That being said, greenboy has pretty much already thought out and solved the challenges you are now facing. I echo Passinwind's recommendation that you go the fEarful route.

[Passinwind]

Originally Posted by Patman27

I hadn't even really looked at the specs for the mid box yet.

Then why say you can't install one? Of course, if you just flat out don't want to, it's your choice.

My cab has approx. 5.1ft^3 as of interior measurements. Subtract volume for the port (assume .15 ft^3) and the speaker (you figure it out ) then 4.x ft^3

Great, although that sounds maybe a bit small for the port? WinISD has a calculator for the volume occupied by the speaker BTW.

[kesslari]

Originally Posted by Patman27

Also, it seems fEarful cabs are quite the staple of the DIY cab builder. Are they REALLY that good?

Yes.

[Patman27]

Originally Posted by DukeLeJeune

you want to cross over well below that huge 1.2 kHz peak and/or suppress it aggressively. Just a thought, as you look at a DIY crossover.

That being said, greenboy has pretty much already thought out and solved the challenges you are now facing. I echo Passinwind's recommendation that you go the fEarful route.

Duke, looking at the response curve on USSPEAKER, I think I'm just not reading it right. The "huge 1.2kHz peak" that you also referenced in my original build seems like only 3dBs at 1.5-2kHz. I've always been curious as to what I'm not getting.

As for the crossover, greenboy seems to have made it clear that using his crossover in a different enclosure will not yield such good results. Would you suggest that I just copy-paste one of his designs or use a crossover calculator program?

Interesting stuff!

[Plstrns]

Huge beaming peak.

I've played through my 3015lf's full range, you don't want to go there.

[Patman27]

Originally Posted by Plstrns

Huge beaming peak.

I've played through my 3015lf's full range, you don't want to go there.

That's what I'm currently doing, sadly. Which is why I need to whip up an x-over. And an 18Sound 6ND410.

[rpsands]

If you need to go on the cheap, an Alpha 8MRA and a stock 500hz crossover from Eminence would get the job done. Much better than nothing.

[Patman27]

I can make a crossover, I'm just not learned in all of the theory necessary to design my own. If I use a calculator or a pre-made design, then I'd rather go that route then buy an Eminence pre-made.