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  #1  
Old 02-23-2014, 05:01 AM
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Custom cab design w/Eminence BP102's

I have two of these drivers that I want to put into a 2x10 cab to use under my Mesa Carbine M3. Future plans will include a second cab of the same design.

I play in a 4-piece horn funk band and use an octave pedal occasionally. What I'd like is tight, round, punchy with good low-end.

I will use the recommended Eminence cab design but don't have a good feel for whether this will be a good cab for my application.

So I appeal to the TB cab design guru's for your expertise, guidance and knowledge!

Here are the driver specs.
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  #2  
Old 02-23-2014, 08:17 AM
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Those drivers will require a ported enclosure to work in your application. If you're willing to put up with lugging around a 4 cu ft 2x10, you can get very low, tight and punchy with those.

But most people don't want to lug around a 2x10 that's the size of a typical 4x10. The flat response is also off-putting to most, who prefer the "warmth" of a stronger mid-bass response. Both of these considerations drive the design to a smaller ported enclosure, and slightly higher tuning frequencies - which is where most commercial designs fall.

The joy of being a DIY is you get to choose what compromise you make according to your own personal taste and needs. Eminence has a "cabinet design" link on the page you referenced that shows several box sizes and their response. That's a good starting point for reference. Then you can start tweaking the design to your taste.
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  #3  
Old 02-23-2014, 11:33 AM
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OP,

The new-style BP102-8 has an EBP of 74.
This is midway between the sealed box (EBP<=50) and vented box (EBP >= 100).
In short, this driver will swing either way.

Link to BP102 Response

On paper, the tightest bass response always comes from a sealed box.
The audiophiles claim they can hear the difference... so up for debate.

If you notice the response bump for various sealed Qtc, you will see how box size affects the response.
The bump around 100 Hz is very "saleable" because it presents the illusion of big bass, at the expense of deep bass extension.
Note the steeper roll-off with the higher Qtc values.

The D2 (0.577) has the tightest bass response, and 0.99 has the highest power handling with most rapid fall off.
The B2 (0.707) produces the most area under the curve, plus an acceptable box size and power handling.

A solid sounding bass cab will have good response down to the 2nd harmonic of your bass.
If for low E (41 Hz) this is 82 Hz, and 64 Hz for a low B.
Notice that all the sealed BP102-8 are -3dB or less down to approximately 60 Hz.
These will do a nice job for electric bass.

Caveat: BP102-8 is a woofer.
It has a limited high frequency response, and will tend to sound "thuddy" compared to a brighter driver.
Link to BP102 Datasheet

Caveat: BP102-8 is not a high efficiency (loud) driver.
These don't make a whole lot of noise per watt, so multiple drivers are required.
If you have a two-channel amp, you can run four in all-parallel wiring and make a good amount of noise.
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  #4  
Old 02-23-2014, 12:28 PM
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Quote:
Originally Posted by bgavin View Post
OP,

The new-style BP102-8 has an EBP of 74.
This is midway between the sealed box (EBP<=50) and vented box (EBP >= 100).
In short, this driver will swing either way.

Link to BP102 Response

On paper, the tightest bass response always comes from a sealed box.
The audiophiles claim they can hear the difference... so up for debate.

If you notice the response bump for various sealed Qtc, you will see how box size affects the response.
The bump around 100 Hz is very "saleable" because it presents the illusion of big bass, at the expense of deep bass extension.
Note the steeper roll-off with the higher Qtc values.

The D2 (0.577) has the tightest bass response, and 0.99 has the highest power handling with most rapid fall off.
The B2 (0.707) produces the most area under the curve, plus an acceptable box size and power handling.

A solid sounding bass cab will have good response down to the 2nd harmonic of your bass.
If for low E (41 Hz) this is 82 Hz, and 64 Hz for a low B.
Notice that all the sealed BP102-8 are -3dB or less down to approximately 60 Hz.
These will do a nice job for electric bass.

Caveat: BP102-8 is a woofer.
It has a limited high frequency response, and will tend to sound "thuddy" compared to a brighter driver.
Link to BP102 Datasheet

Caveat: BP102-8 is not a high efficiency (loud) driver.
These don't make a whole lot of noise per watt, so multiple drivers are required.
If you have a two-channel amp, you can run four in all-parallel wiring and make a good amount of noise.
when you bring up the decimal places e.g. 0.99, are you referring to the volume of the box? e.g. .99 cubic feet?
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  #5  
Old 02-23-2014, 12:46 PM
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Thank you so much for the info, it's just what I was looking for!

I'd like to make the box as small as possible, but I'll look at the numbers a bit before deciding.

bgavin, would you go sealed or vented?
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Last edited by jongor : 02-23-2014 at 12:51 PM.
  #6  
Old 02-23-2014, 01:30 PM
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^ I'd personally go vented, it helps boost the low end of the driver, meaning you get a bit more bang for your low-end buck IMO. Of course, the BP-102 is a very capable woofer, I'd say one of the most capable 10" non-neo woofers out there, and it is also very capable of being in a sealed cabinet. Personally, I'd design something around their "larger vented 1x10", at 2 cubic feet and a 40 hz tuning, it'll go low, and it has a 100watt excursion limit, so it'll take a lot of power too, two BP 102s in a box of twice the size and the same tuning, paired with a good midrange driver, would kill most commercial cabs out there.
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  #7  
Old 02-23-2014, 02:39 PM
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Quote:
Originally Posted by jongor View Post
bgavin, would you go sealed or vented?
It depends.

Vented Flat is 4 cubic feet, F3 around 30 Hz.
Sealed B2 is 1.8 cubic feet, F3 around 60 Hz.

Power handling (xmax limits)
Vented Flat is 43 watts down to 31 Hz.
Sealed B2 is 33w to 31 Hz, 38w to 41 Hz.
Both are about 108 SPL at xmax limited input power.

I mostly play keyboard synths with full response down to C1 (32 Hz).
We don't play very loud, so I went with a LAB12 + Alpha 6a instead.
Sealed B2 is 1.9 cubic feet, F3 around 43 Hz.
Input power xmax limit is 240w down to 31 Hz, SPL is about 112 at this input power.

BP102 vs LAB12 Max SPL in 1.0 Cubic Feet
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  #8  
Old 02-26-2014, 02:36 PM
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What are the B2, D2 and C1 you refer to?
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  #9  
Old 02-26-2014, 03:47 PM
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I built a 210/6 (with a dedicated mid driver for everything above 800 Hz) quite a while ago. I never found the BP102's lacking for low end, but IMO they die out above 700-800Hz and by themselves don't really handle everything well. They handle lows great though.
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  #10  
Old 02-26-2014, 04:05 PM
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that sounds interesting...what were the specs?...mid driver, cab size, crossover...
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  #11  
Old 02-28-2014, 07:12 PM
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Quote:
Originally Posted by jongor View Post
that sounds interesting...what were the specs?...mid driver, cab size, crossover...
It was actually a 6" mid taken from one of my Bose entertainment speaker cabs. It actually sounded damn good with the BP102's. I used a bi-amp rig and messed with crossover points.

This was back when I was building my own cabs and experimenting. Then greenboy went and designed the fEARfuls and I haven't looked back. The 210/6 was a killer little cab and two of them together were even better (I think I installed Eminence 800Hz crossovers by that time).
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