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Acoustic 406 2x15 w/Faital 15PR400

#5
abarson said:
Why would you add ports to a cabinet that is already slot ported?

Here's a drawing with dimensions I found on a different forum:
Click to expand...
I seem to remember the slot port being inadequate for the combination of speaker/cabinet volume, but like I said, this stuff doesn’t really make sense to me. I DO know that just throwing any speaker in any cabinet can be disappointing or even disastrous. I’m just looking for advice on how to make these speakers work as efficiently as possible in this cabinet (insulation, ports, etc.) and if it’s even really feasible.
 
#8
Low End Curse said:
I seem to remember the slot port being inadequate for the combination of speaker/cabinet volume, but like I said, this stuff doesn’t really make sense to me. I DO know that just throwing any speaker in any cabinet can be disappointing or even disastrous. I’m just looking for advice on how to make these speakers work as efficiently as possible in this cabinet (insulation, ports, etc.) and if it’s even really feasible.
Click to expand...

I had an old Acoustic 406 cab many years ago that I loaded with a couple EV DL-15B cast frame speakers that were about the same vintage as the cabinet. The port in the cab was actually pretty close for those speakers, but my guess is the Faitals will have significantly different Thiel-Small parameters than the original speakers had, whatever they were. Take care in sending low frequency through them at much volume as you have it now. If the port is terribly wrong for the Faitals (which is not unlikely), the unloaded Faitals might go to xmax plus tax….:woot: In my experimenting, ports on old cabs were usually too small for modern speakers, which might keep you from destroying the Faitals, but that’s definitely not a guarantee….
 
#11
James James said:
This here is a perfect example of that person in the crowd who wants to be picked so they can shine. Therefore I will ask the question.......What is the math??
Click to expand...
Arjank provided the answer, but here’s the approximate math behind it:

[This invalid link has been removed]
 
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#12
Quick throw together in WinISD based on the data given, looks like a 33Hz tune, 300W total before hitting Xmax above tune and port air speed is modest. Looks OK to me, but I spent less than a minute on it.

You'd be advised to put in a HPF at maybe 40Hz to stop overexcursion from random signals below tune.
 
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#14
agedhorse said:
Rule number 1, don’t trust the results from WinISD without verifying with another method.
Click to expand...
I don't, I have other software I know I can rely on, but that's all I have at the moment as the main PC is crated for the move and I have a crappy 6yo Celeron laptop to use.
I'm just saying, at first glance it doesn't look terrible. I've modelled up other preferred driver subs before that have been a whole lot worse.

And the OP is getting the answer he paid for.
 
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#15
agedhorse said:
Rule number 1, don’t trust the results from WinISD without verifying with another method. Ajank’s results reinforce this suggestion.
Click to expand...
For calculating the port length I don't use WinISD because it's not very accurate. Boxsim on the other hand takes the position of the port into account which affects the port tuning. Btw. it's a very easy tool to use.

upload_2022-6-7_16-28-12.png
 
#18
Snert said:
How do you get a port height of 6.6cm when it's 1 5/8"
Click to expand...

You're absolutely right, mistake on my side :banghead:, it's 43mm.
The tuning frequency will then be a bit lower, approx 35hz.

Below a simulation of two 15PR400's in 190 liters tuned to "35hz" (sim software AJhorn gives 37hz), not bad, but when pushed (800 watts) there's a powerdip around 50hz so keep that in mind. Up until 300 watts (red line) there's no powerdip.
Shortening the port length by approx 2 1/2" would give the optimal tuning (approx 42hz) for the 15PR400 in that cabinet volume, it will slightly increase efficiency between 50 - 70hz and slightly reduce the powerdip.
If you keep the drivers in that cabinet you could remove 2 1/2" from the shelf to shorten the port.

upload_2022-6-7_17-42-12.png
 
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#19
Low End Curse said:
Hi everyone, I’ve had this acoustic 406 cabinet loaded with Faital 15PR400’s for quite a while, and I’m just getting around to using it. I’m curious about how efficient this speaker/cab is and if I should do anything like adding ports or anything? I figured there are folks on here way more knowledgeable than myself. Thanks!
Click to expand...
I'm old so I remember cabinets that really sounded good from the late 60's and 70's. This cabinet was a good sounding cabinet along with the Sunn 200S and Acoustics 18" folded horn and Ampegs 8X10 or their 2-15. None of us knew about the math we just heard the sound and made up our minds. I have this cabinet although I don't use it because of the size.
 
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