Custom DIY 2x15 cab build

[Joe Louvar]

BTW, I just clicked on your custom bass link for the first time - and wow, they look very nice, no wonder your new Starlliner 215 is built so nice - you’re a real craftsmen!!!

[johnk_10]

a long shelf port would give it more port area but again, i think if they tuned it to 45Hz, the cab should sound the same as mine.

BTW, while i was breaking in my speakers last night, i ran my signal generator thru it and slowly swept a pure sign wave thru the cab from 10Hz to 6Khz and a pretty loud volume and while i could feel lots of air blowing out of the ports, there was no chuffing at all. due to the size, shape and port location on my cab, and using flared ports, i couldn't use any larger diameter ones. if i used 6" ports, they'd have overlapped the speakers.

[Joe Louvar]

Way cool, and since the Starliner 215 sounds good and there in no chuffing I would think your port area is large enough. On another note - if there is a big noticeable difference after the 3015s break in please post a heads up comment.

[fuzzer]

Originally Posted by johnk_10

a long shelf port would give it more port area but again, i think if they tuned it to 45Hz, the cab should sound the same as mine.

.......... if i used 6" ports, they'd have overlapped the speakers.

I know some people don't like this as an alternative, but what about putting 6" ports in the back of the cab? Perhaps the very lower bottom corners?

[Joe Louvar]

That would a be a completely different cabinet deign. Personally I hate rear ports - because walls and etc can affect the performance way too much.

EDIT: besides, there doesn't seem to be any reason for more Starliner 215 port area.

[johnk_10]

if you want more port area, i'd just make the cab a little taller and place two 6" or three 4" ports at the bottom (like one of the replies to this thread mentioned). that would put the 15's up higher (closer to ear-shot).

[johnk_10]

Originally Posted by fuzzer

I know some people don't like this as an alternative, but what about putting 6" ports in the back of the cab? Perhaps the very lower bottom corners?

yes, that would work, i just wanted mine to have them on the front.

[greenboy]

Originally Posted by Joe Louvar

EDIT: besides, there doesn't seem to be any reason for more Starliner 215 port area.

There isn't, if your input into the cab doesn't require it. But there is if you are using higher power amps that can drive the woofers to full excursion and the signal has appreciable LF content. In these cases, it's not just about chuffing either - the cab impedance and tuning can actually begin wandering.

Alex has a lot of port area for those reasons.

[Joe Louvar]

Hi greenboy, thank you very much for jumping in here. Wow, that is good to know.

John, what happens when you drive the Starliner 215 with some high power - any chuffing?

And thinking out loud - the round plastic ports seem to make building lighter and easier. Since the Starliner 215 has two 4” round ports which equals 8 inches of port area - I wonder if for example the shelf port on the Barefaced Super Fifteen is about 12 inches of port area. I think Mr Foxen has a super 15 may be I can ask him to measure the size of the shelf port and depth (length).

greenboy, how much more port area does your 215 design have - what is your total port area?

[rpsands]

The current design would accept side shelf ports easily due to the width, or 5" ports - down side with 5" tube ports is they are not readily available. You would need to go shopping for 5" ABS and then bust out the dremel if you wanted flare.

[Joe Louvar]

Hmm, the Starliner 215 has 8 inches of port area now - how much port area would be best?

[johnk_10]

Originally Posted by Joe Louvar

John, what happens when you drive the Starliner 215 with some high power - any chuffing?

i've run the cab louder than i'd ever want to be gigging with it standing 8-12 feet from it and it hasn't shown any signs of chuffing with gobs of power and more low end than i'd ever play with.

....but, i'm certain that greenboy's 2x15 design would be more correct than mine, since he has alot more experience in cabinet tuning and speaker response characteristics than i do (i just kinda go by the seat of the pants and the 'TLAR' (that looks about right) method), but i actually couldn't be happier with the way that my cab sounds.

[John D]

+1 for the TLAR method.

[rpsands]

Originally Posted by Joe Louvar

Hmm, the Starliner 215 has 8 inches of port area now - how much port area would be best?

It has 2( 2 ^ 2 * pi ) square inches of port area so around 25 square inches. About enough for a single 3015 to reach max excursion in a slightly bigger box.

With the small internal dimensions I would expect to see at minimum 32 square inches with flared ports for maximum excursion (remember, bass guitar signals are not sine waves; huge crest factor = occasional chuffing at average levels far below those that don't make noise with sine waves).

Ideally, I would aim for right about exactly twice the amount of port area that's there.

With 300w or less, I wouldn't bother worrying about it, but for commercial consumption I'd redesign with corner triports or side shelf ports.

[Joe Louvar]

Check - oh and I’m sorry if I hijacked your thread, I just like trying to learning all I can - so I hope greenboy replies to my above question and thank you so very much for sharing your new Starliner 215 - it’s awesome.

[thisSNsucks]

That is one cool looking and great sounding cab!

[Joe Louvar]

Thank you rpsands.

[johnk_10]

the funny thing is, with all of this port tuning discussion, is that while i had the grill off yesterday, i ran it again as a sealed cab with some port blockers, and i think i actually like it better that way. even though eminece says that you're not supposed to run 3015's in a sealed cab, i like the way that it tightened up the low end and made it feel more immediate and punchy. they'll add a full pound to the weight of the cab, but i have a feeling that i might run it that way for a while.

[stiles72]

Amazing build John! This is what a modern 2x15 should be! It would be a great cab for the Ampeg PF500 head- would love to have one of these covered in Black Diamond with the Neutrik jack on the side of the cab.

Maybe I missed this in the thread - but have you thought of using aluminum dust caps on the drivers, like you did in your 4x12 cabs? I think it would really set the cab off from a cosmetic perspective.

[rpsands]

Originally Posted by johnk_10

the funny thing is, with all of this port tuning discussion, is that while i had the grill off yesterday, i ran it again as a sealed cab with some port blockers, and i think i actually like it better that way. even though eminece says that you're not supposed to run 3015's in a sealed cab, i like the way that it tightened up the low end and made it feel more immediate and punchy. they'll add a full pound to the weight of the cab, but i have a feeling that i might run it that way for a while.

The whole not using in a sealed cab thing is more an "optimal performance" or whatever I think. The 3015 will roll off on bottom much earlier than a speaker with the appropriate characteristics for a sealed box.

That said, GB has had a lot to say about low tuning being better than sealed most of the time (excepting with some tube amps) and my modeling suggests he's right.