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Basic Speaker Design Questions

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PhantomGuitar

Guest
Aug 9, 2014
15
3
34
#1
Hi all,

So, if I was to use a Eminence Beta 15A speaker in a speaker enclosure, the spec sheet recommends a volume of 8.3cubic feet^3.

So, If i was to have a cabinet that was 33 inches tall, by 24 inches wide, by 22 inches deep, i would come up with a volume of 8.4cubic feet^3.
I've been happy with Betas in similar sized enclosures, with no tweeters/mid range drivers etc. I'm fine with the response of Betas (for what thats worth, and i would prefer to use one here).

Would this work?

Am I way off here?
 
#2
I am no speaker design expert by any means but that's freaking huge! They'll work in smaller boxes than that. They're often recommended for the old B-15 ported double and single baffle cabs, which are like 21" x 21" x 14".
 
#3
It is huge. Like the size of an 810 fridge for one speaker.

Know that some of those "suggested alignment" are for pigeon-holing one-goal goals, like absolute deepest response, or absolute flattest response with lowest possible bass extension, with total disregard for how It will sound with a bass guitar or If you'd even be able to move It out of the house yourself or even fit It out the door.

I bet its powerhandling is a tiny pile of dung down there too in that giant box.

A more realistic alignmemt that would work well in the real world would be something like 3.25-4 cu.ft (net internal volume) and a port tuning between 40 and 50hz.

Ton of different voicings within those ranges, all of them fit through the door, and won't start a fire with a 50 watt amp.
 
#4
Thanks! I had a feeling that was rather big for a driver such as a Beta 15. If it was a 3015 then maybe, but i digress.

The Beta 15 is fairly flexible about enclosures correct? All i'm going for is a Vintage style 15, which will be paired with a V4.

Could i get away with a Ampeg B-15 size cab, but sealed?
 
#5
PhantomGuitar said:
Thanks! I had a feeling that was rather big for a driver such as a Beta 15. If it was a 3015 then maybe, but i digress.

The Beta 15 is fairly flexible about enclosures correct? All i'm going for is a Vintage style 15, which will be paired with a V4.

Could i get away with a Ampeg B-15 size cab, but sealed?
Click to expand...
You might. I tried a Delta once in a PF115he I used to have, which is sealed and approx the same size as the old B-15 cabs, and I didn't care for it, but the Beta may react better. However, you don't need to build a complex double baffle design to port a B-15 cab. Porting method is immaterial as long as the tuning's the same.
 
#7
Beta is a bit more friendly toward sealed boxes than the Delta is. I'd still port it, and use a couple plugs or port cover of some sort to end up with a sort of "regular tuning/low tuning/sealed" options. Could come up with that by making 2 ports, with the option to close one or both of them.

A very low port tuning can help get some more oomph and power handling out of it, but still have a lowend rolloff that more simulates a sealed cab, ie: not big booming lows.

Pull up WinISD and model it with say a 50hz port, 35hz port, and sealed. Box size around 3.5 cu.ft give or take.
 
#8
Also Eminences cab design .pdf's will have sort of small, medium, and large box models for that driver. Can look at those to get a place to start.

None of them will be as large as that "fridge with one speaker in it" alignment the program gave you in your first post.
 
#9
This is why I asked questions before cutting anything.

So, If I had a box that was 20x24x14, for a volume of 3.8 cu.ft, plus my two ports would be acceptable?

(So wide so it can fit my V4 head, and not hang off the sides)
 
#10
Check out the WinISD box designer program if you don't already have it. It's simple to learn and use, and will give you excellent info on your box's capabilities. You only need the regular version not WinISD Pro.

Your box is about right for tuning with a single 100mm (4inch) diameter port, to get down to around 42hz or so. The port is going to be around twice as long as it is wide. This is where the software is so helpful, you can play around with tunings and look at the response it graphs on screen. You should also look at the maximum cone movement (excursion or Xmax) that will occur as the speaker nears its tuning point at high power.

But your design is pretty close now. WinISD is free and doesn't anything bad to your PC, so you should use it as a tool to make your box that much better. Good luck ! Speaker box designing and building is a lot of work, but also a lot of satisfying fun.
 
#12
PhantomGuitar said:
This is why I asked questions before cutting anything.

So, If I had a box that was 20x24x14, for a volume of 3.8 cu.ft, plus my two ports would be acceptable?

(So wide so it can fit my V4 head, and not hang off the sides)
Click to expand...

That's an acceptable volume for the beta15a, yes. I don't really like that driver for bass guitar use though. I would put 2 Beta 12's in that same size box instead. Excursion limited power handing would be nearly 3x better, maximum spl would be 3db higher, and you would have a smoother frequency response in the ~100hz region.
 
#13
NoGraveConcern said:
That's an acceptable volume for the beta15a, yes. I don't really like that driver for bass guitar use though. I would put 2 Beta 12's in that same size box instead. Excursion limited power handing would be nearly 3x better, maximum spl would be 3db higher, and you would have a smoother frequency response in the ~100hz region.
Click to expand...
It's Ampeg. Who wants that? ;)
 
#15
The Beta 15a will provide 'vintage' bass tone in a 3.5 cf box tuned to 35-40 Hz, and will have sufficient power handling for the V4. Larger cabs will have less bass peaking, but also less power handling in the mid-bass. The other option is to use a sealed cab. The Beta 15a will provide 'vintage' tone in a sealed cab as small as 2 cf. 3 cf sealed will get you nearly the same tone as the ported boxes above (some would say better because its sealed), and with sufficient power handling for the V4. Larger sealed boxes yield lower bass, but less power handling. 2-3 cf sealed is optimum for your needs.

The Eminence 8.3 cf vented box yields a maximally flat bass response that goes spectacularly deep, but has equally spectacularly low power handling. Possibly great for a low power hifi system, but non-useful for bass guitar (with the exception of a wildly impractical, low power practice rig).
 
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#18
I believe this is the cab design doc.

[Invalid or Expired Link Removed]

I see two suggestions for ported cabs. One has total volume just over 6 cu. ft, the other around 3.5 cu. ft.

BTW, I just put a Delta 12LFA in a 2.7 cu. ft. ported box and it is delightful for bass. (Note, I corrected the figure here.)

Otto
 
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