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Bassbox Pro 6 vs WinISD, which do you trust? (Also, 12" driver recommendation)

Eric_Allard

Eric_Allard

Oct 30, 2010
529
480
Fredericton, NB
#1
Title says it all... When their results do not match, which do you trust more?

I have designed several cabinets with Bassbox Pro 6 over the years and I don't know that I trust it anymore. I don't fully understand why results from the "Electrical Power" graph doesn't match what can be derived from "Cone Excursion" graph for the displacement-limited region. I think it may derive EP from peak power and CD from RMS, but even that doesn't make sense since the thermally limited region is clearly based on Pe, not peak.

Long story short, I'm trying to choose replacement drivers for a box I built that can't take all of the power from my amp (480W from a GK 700RB-II). The box has a Vb of 4 CF and 15"x2"x3.25" long shelf port. I'm looking for a pair of 12" speakers. I currently have a pair of Eminence Delta Pro 12A's in there. I like the tone, but it loses a lot of clarity at high volume.

Bassbox Pro EP graph says it can take about 200W around 55Hz, but that drops off precipitously below that. WinISD says 275W down to approximately 43Hz.

I'm wondering what people think of Eminence's Kappalite 3012HO. It appears to have a similar frequency response to the Delta Pro, but the increased Xmax shows they should be able to take approximately 550W down to about 44Hz (according to WinISD). Bassbox shows about 315W down to about 55Hz, which is not a significant enough improvement to warrant the driver swap.

Also, does anyone know how much displacement-limited power handling is really required? I'm playing an instrument, not a sine wave generator, it's not like all 480W from my amp are all going into a narrow frequency band.

Does anyone have any alternate driver suggestions?

Also, does anyone know which program is more trustworthy and why?

Due to the shelf port, adjusting the tuning of the box would not be easy. Based on the geometry described above, the box tuning is 53.5Hz or 50.6Hz depending on whether you trust Bassbox or WinISD, respectively.

I don't own any five string basses (nor do I have any plans of getting one) so I don't need the box to handle anything lower than E or the occasional song in drop D.

Thanks in advance for the help!
 
#2
I prefer Bassbox pro.
Before I used Bassbox I used Winisd until the moment than a pro cab designer told me that you can't trust WinIsd port calculations. I had to reduce by WinIsd calculated ports by around 1/3 in length to get the desired tuning. That's a very lot of deviation!
WinIsd also calculates very different system impedance curves. About an adequat cone excursion I can't tell anything how good WinIsd does this predictions. By the other hand it's very hard to predict how much power of the bass signal spectrum really hits a small bandwith like 60..70Hz for example. That's why I consider excurson vers amp power basically a little bit different than most folks do it.
IMO most importent paramter for excursion is the cab tuning itself. Excursion Power handling is mostly deminished by increasing tunings.

WinISD is only slightly different to bassbox pro in prediction of response curve by a given Vb and fb. That means WinIsd is good in prediction of response graphs, that's all.

btw
Eminence did all their cab designs by the use of bassbox pro (eminence designer)!
 
Last edited:
#3
Thanks for the response.
One thing I suppose I could check that the box tuning came out as predicted by Bassbox Pro. What is the best way to accomplish this?
I can think of two ways:
Look for the frequency that causes the lowest impedence; or
Put rice or something on the cone and find the frequency that causes the least cone excursion.
Is there a better way?
 
#4
Displacement always dominates power handling limitations for low frequency bass guitar applications. Electrical power and displacement limits are two different parameters.

I prefer BassBox pro as well.
 
#5
Some playing techiques on the instrument like excessiv damping techniques may generate sub lows which are way beyond the cab tuning. Those transients may in some circumstances reach full output potential of an amp. Sometimes it is a hard trade off of desired response and displacement handling.
 
#6
ThisBass said:
Some playing techiques on the instrument like excessiv damping techniques may generate sub lows which are way beyond the cab tuning. Those transients may in some circumstances reach full output potential of an amp. Sometimes it is a hard trade off of desired response and displacement handling.
Click to expand...
This is why it's essential IMO for modern, high powered amps to have a responsible and appropriate high pass filter. It's something the pro audio industry has known for decades.
 
#7
fdeck has cabinet design java app at his site. You can save the parameters in the url.
And there's some libs for using mathlab, or ltspice. Even Fusion360

Overall though, This is what MDF is for. Build a prototype in mdf, measure it, adjust the parameters to match the measured ones.
Later build the cabinet in good ply. You may find that you don't really need the fundamental for low E to have a good and bassfull sound.
 
#10
I think the GK already has a pretty aggressive HPF built in so long as the "5 string" button isn't pressed in. I agree that flat response down to the fundamental isn't necessary.
My other question: are there any suggestions for a good neo full range 12" that has a good Xmax and high sensitivity?
Thanks
 
#11
I bought these speakers about 10 years ago when I didn't know anything about speaker design (someone whom I thought knew what he was doing recommended them). I'm considering using them to build a pair of PA speakers for the jam room and putting something more appropriate in my bass cab.
 
#14
Here is where it gets really confusing:

Modeling the Deltalite 2512-II, Bassbox shows it can take 430W down to 50Hz, which is significantly better than the Delta Pro and the Kappalite 3012HO.

In WinISD, however, that same driver can only take 230W before becoming displacement-limited, which is significantly worse than the Delta Pro and the Kappalite 3012HO.

So, not only do they not match, but their results for certain drivers trend in different directions.

My conclusion so far: If I am to trust Bassbox Pro 6 (and many happy reviews here on Talkbass), the Deltalite 2512-II might be my best choice: it's not very expensive, efficient, light, and can handle more power than my Delta Pro's before becoming displacement-limited.
 
#17
Double check that your parameters were entered correctly on both software platforms. Also make sure the models are the same and any HPFs in the models are identical. May be just a simple error.
 
#18
agedhorse said:
Double check that your parameters were entered correctly on both software platforms. Also make sure the models are the same and any HPFs in the models are identical. May be just a simple error.
Click to expand...

That's a good point. It is very convenient to use Bassbox's extensive driver database, but I have already found several erroneous entries in it so it is a good idea to double check.
 

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