# SA-8 V.3 enclosure analysis help



## allthewayne (Mar 4, 2013)

I built a box for my SA-8. Overall I'm pretty happy with the output. I do have a couple questions that I'm hoping someone can help me with.

I didn't mount the sub in the center of the box airspace. It is a wedge shaped slot port box that fits under the rear seat of my f150. Looks like this.










What effects would offsetting the driver from center like that have?


Two calculators have my tuning at 34-35hz, but the sugar/salt test with a sweep puts me at 27-28.... I have some pretty heavy port noise at that low hz though. Its chuffing, but also making some other noise... unloading maybe? It's like a flapping/chuffing. However, doing some after-math on my box I think I botched my port area. Rule of thumb is 16in²/ft³, so I should have 11.8in².... but I have 8.5in² ... :worried: This is probably why my port noise is worse than I expected, but could it be having other effects on things?

Slot port is angled across the top, cause of the wedge. It's avg like 4.75"x1.79"x25.5". 

Also, do I measure this red space in my port length measurement?













Box measures in at 0.94 ft³, minus the port which is 0.123ft³, minus the sub displacement which is .08ft³. For a total of 0.737ft³.

So my main question is did offsetting the driver from center like that lower my tuning? Even though the sugar sweep test looked like it was around 27-28hz... the actual output doesn't agree with that.. It sounds more like the best reponse is around 33-35hz...Or is my small port area messing with that?....

Lots of questions here.. thanks in advance to anyone that can help.


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## SHAGGS (Apr 24, 2011)

Placement across the front won't effect tuning.
Port does seem small and is likely the cause of your chaffing.
Yes, the tail end of the port (red) counts for length.
Are you using a subsonic filter?


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## Grinder (Dec 18, 2016)

This ^^^^^ 


Also...

According to: Port Length Calculator your cabinet is at 32 Hz (not including the additional red-area length, which would bring it lower still). 

While (or because?) I'm no expert, I've always ended up with a somewhat lower tune than WinISD and calculators would suggest; and I've heard this from others as well. Between this seemingly common discrepancy, and the extra unmeasured red-area length of your port, your real-world tune is what I would expect.

While modeling (with WinISD, for example) would be best, here is a vent area calculator that takes amplifier power into account as well (which should be more accurate than a cabinet volume based rule of thumb): https://docs.google.com/spreadsheets/d/1VREceNxz9YOcFlI8O_TG62-4O-l3Q2IjD5qsEkVVh28/edit#gid=0

According to ^this^ calculator, you've got slightly more than half the minimum area required at 750 watts.

Also, angled/smooth corner transitions and flared vent openings (both inner and outer) help to reduce the audible chuffing effect of high vent velocities.

Also bear in mind that high vent velocities, due to less than optimal vent area, will limit output potential accordingly.


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## allthewayne (Mar 4, 2013)

I'm going to have to rebuild this box.

I'm using the subsonic on my amp, I played a test tone at 25hz and just increased the filter until the chuffing/slapping stopped. This seems to have negatively effected my low end above that hz as well, around 30-32hz, which is to be expected. I tried to offset this with gain but the higher 40-50hz ranges didn't like this and was obviously clipping.

I am using high level inputs from my factory B&O amp in my F150. I've measured a voltage change of 50% (!!!) coming from those wires... can't believe that ****...I'm running an SAE-600D. I can dial the voltage to 30v, and watch it sweep all the way down to 15v on a 50hz 0db test tone. Gross. I'm going to have to chop it all out and run my MS-8 after all.

Before I had a multimeter I ran the gain at 100% because I misunderstood the high level inputs. My dust cap got fairly hot, and I could smell the wood glue coming from the box (It had just cured the day before). In one particular instance where I was trying to find the limits of this lil guy, I smelt something a little nastier, for about 10 seconds. The smell came quick and I backed her off right away, then came to my senses and turned down the gain. Could it have been easier to get some coil smell on break in? First time the glue's been heated? Or do you guys think I did damage? The sub still plays 100% from what I can tell.

The 25.5" measurement of my port length includes the red area.

Sucks to have to rebuild this thing, It was a ***** to shim the sub mounting surface on an angle so that the top would fit on. Had to sand a small recess into the top as well to allow clearance for the magnet. I kinda expected to have to do a revised version of the box, but not for this reason. I wonder what I read that made me botch the port area so bad  .


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## allthewayne (Mar 4, 2013)

Thanks for that calculator Grinder. Using that, and a 33hz tune, I was able to redesign my port for 18.5in² in a way that will still fit the space I have by extending it as shown in the photo. 










33hz should be a good compromise for this little SA-8 if I'd like a little more low end hey? With that big port area I should be safe at that hz?

Any problems with a "slot" port being shaped like this?


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## JCsAudio (Jun 16, 2014)

AlltheWayne, I do not like slot ports as much anymore ever since I tried my first Precision Port from Parts Express. They’re easy to tune and better for sound quality in my opinion. I changed my SA-12 from a slot port design to a precision flared round port design and also did the same for my Alpine SWS 10 in my van, and like them better. They also seemed to have a slight edge in SPL too. 

Just some food for thought as you figure this out. At least your port is straight so I think that helps. I also still have my SD3 10 in a box very similar to yours and like that one so it’s all subjective I guess.


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## allthewayne (Mar 4, 2013)

Nevermind... with that added port area I'd need a 56" port. Back to the drawing board... To keep my net volume I guess I'll have to bend the port after all... although I might just stick it outside the box though, seems like it'll be a lot easier and it's under my seat anyways so...


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## allthewayne (Mar 4, 2013)

V8toilet said:


> AlltheWayne, I do not like slot ports as much anymore ever since I tried my first Precision Port from Parts Express. They’re easy to tune and better for sound quality in my opinion. I changed my SA-12 from a slot port design to a precision flared round port design and also did the same for my Alpine SWS 10 in my van, and like them better. They also seemed to have a slight edge in SPL too.
> 
> Just some food for thought as you figure this out. At least your port is straight so I think that helps. I also still have my SD3 10 in a box very similar to yours and like that one so it’s all subjective I guess.


Using a 4" port? So an area of 12.5in² ? Is that going to cut it? If so I might try and retrofit a tube into my current box.. although it will be a bit of a challenge. Any of the good aero ports with their large flares is going to be tough.


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## Grinder (Dec 18, 2016)

allthewayne said:


> Using a 4" port? So an area of 12.5in² ? Is that going to cut it? If so I might try and retrofit a tube into my current box.. although it will be a bit of a challenge. Any of the good aero ports with their large flares is going to be tough.


There would be a VAST reduction in port noise (partly due to the increased area, but mostly due to the inner and outer flares), and a significant improvement in output potential

If you do go this route, you're gonna need at least one extra tube and a couple connecting rings (to extend the port past 17"): https://www.parts-express.com/cat/s...eca:matches(.,"P_Searchable","1")]&PortalID=1

Also, be sure to use this port length calculator (as flared ports need to be a bit longer than non-flared ports, to account for the wider flared area): 
Products Menu


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## allthewayne (Mar 4, 2013)

Grinder said:


> That would be a VAST improvement in terms of port noise - partly due to the increased area, but mostly due to the inner and outer flares.
> 
> If you do go this route, you're gonna need at least one extra tube and a couple connecting rings (to extend past 17"): https://www.parts-express.com/cat/s...eca:matches(.,"P_Searchable","1")]&PortalID=1
> 
> ...


So with that calc I use the gross box volume minus sub displacement, not accounting for what the port will take up, seeing as I don't know the length until I enter the values, or is it net?


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## Grinder (Dec 18, 2016)

allthewayne said:


> So with that calc I use the gross box volume minus sub displacement, not accounting for what the port will take up, seeing as I don't know the length until I enter the values, or is it net?


It is net. You must account for vent displacement.


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## allthewayne (Mar 4, 2013)

Grinder said:


> It is net. You must account for vent displacement.


Roger, thanks.


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## JCsAudio (Jun 16, 2014)

Allthewayne, I use a 3” diameter precision port for my 10” subwoofer and a 4” diameter precision port for my SA-12 and have no port noise in either setup. I would think a 3” precision port would be more than enough for that SA-8. The kit comes with instructions on how to calculate the port length and if I can find the time, I may be able to use Bassbox Pro to model it for you. 

I would go with the largest port you can fit. Use this calculator to help you figure out the length you need based on the diameter you choose. Products Menu


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## Grinder (Dec 18, 2016)

I went ahead and modeled the SA-8v3 D2 in WinISD, at 0.737 ft.^3, 35 Hz, 600 watts (as per your SAE-600D). 

Bearing in mind that this thread is in the SPL Forum, I'm under the impression that this is primarily an SPL application. And based on my admittedly non-expert impression of WinISD response curve results for this driver (along with Sundown's own words), this appears to be an SPL driver. 

If maximum SPL is what you're after, you're going need at least 20 in.^2 (for vent velocity of 22 m/s or less). If you're primarily concerned with eliminating chuffing, a 4" Precision Port should do the trick (at just over 34 m/s). However, I do not a recommend 3" vent, which pushes WinISD velocity results up to nearly 62 m/s, which would (reportedly) seriously reduce output potential ...if not produce some level of chuffing as well (I suspect that it would, but really don't know).

FWIW, I've run a WinISD calculated 42 m/s in Precision Ports, with zero noise (though I'm far more concerned with SQ than SPL).


Response/SPL:









Corresponding 4"/12.57 in.^2 vent velocity:


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## JCsAudio (Jun 16, 2014)

Awesome information Grinder and thank you.


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## allthewayne (Mar 4, 2013)

Grinder said:


> I went ahead and modeled the SA-8v3 D2 in WinISD, at 0.737 ft.^3, 35 Hz, 600 watts (as per your SAE-600D).
> 
> Bearing in mind that this thread is in the SPL Forum, I'm under the impression that this is primarily an SPL application. And based on my admittedly non-expert impression of WinISD response curve results for this driver (along with Sundown's own words), this appears to be an SPL driver.
> 
> ...


Yes, thanks a bunch for this Grinder, much appreciated. I need to figure out how to use winisd.

Would you mind running that again at .7 ft³ and 33hz? I can stick 21.5" of port inside my box, so that knocks it down to .7ft³ even. However, I will probably just use pipe from the hardware store and flare myself because I can't fit the Precision port flare inside my box anyways. That being said, should I follow the recommendation above to use the calc from the precision port website to calculate port length? Because if that's the case I get a 42.5" port length.. 

Am I risking some port noise by tuning lower with the 4 inch port?

Sorry for all the questions...


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## JCsAudio (Jun 16, 2014)

allthewayne said:


> Yes, thanks a bunch for this Grinder, much appreciated. I need to figure out how to use winisd.
> 
> Would you mind running that again at .7 ft³ and 33hz? I can stick 21.5" of port inside my box, so that knocks it down to .7ft³ even. However, I will probably just use pipe from the hardware store and flare myself because I can't fit the Precision port flare inside my box anyways. That being said, should I follow the recommendation above to use the calc from the precision port website to calculate port length? Because if that's the case I get a 42.5" port length..
> 
> ...


You cannot use the precision port calculator for regular round ports; it wont be the same. Attached is a file from Bassbox Pro showning .7 @ 35 Hz and .737 @ 35 Hz. The program suggests .244 at 40 Hz for High fidelity and same size at 31.52 for higher output down lower.

The red line is the .7 box.


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## allthewayne (Mar 4, 2013)

V8toilet said:


> You cannot use the precision port calculator for regular round ports; it wont be the same. Attached is a file from Bassbox Pro showning .7 @ 35 Hz and .737 @ 35 Hz. The program suggests .244 at 40 Hz for High fidelity and same size at 31.52 for higher output down lower.


Sorry .244, that's Port Volume?

I would put 1" flares on the port.


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## JCsAudio (Jun 16, 2014)

allthewayne said:


> Sorry .244, that's Port Volume?
> 
> I would put 1" flares on the port.


That is the box volume noted as Vb of .244 cu ft. Attached is a 31.5 tune and 40.5 tune. Note: none of these are actually buildable without installing a lot of the vent outside the box because a 4" vent requires a very long port. If you give me all the external sizes of your box than I can model it better and even give you cut sizes to build a new one but its a little bit of work.


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## allthewayne (Mar 4, 2013)

V8toilet said:


> That is the box volume noted as Vb of .244 cu ft. Attached is a 31.5 tune and 40.5 tune. Note: none of these are actually buildable without installing a lot of the vent outside the box because a 4" vent requires a very long port. If you give me all the external sizes of your box than I can model it better and even give you cut sizes to build a new one but its a little bit of work.


Seriously?! .244 ?! That's like a third of my current box and seems very very small. Sundown themselves recommend .5-.75? Why so small?


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## JCsAudio (Jun 16, 2014)

allthewayne said:


> Seriously?! .244 ?! That's like a third of my current box and seems very very small. Sundown themselves recommend .5-.75? Why so small?


It was what Bassbox Pro program suggested when I choose the option for it to do that so don’t put much faith in it. I’m going to guess Sundown can’t fit a vent in a box any smaller. For reference my JL Audio microsub with the 8W3v3 subwoofer was installed in a box just .35 cu ft tuned to 35 Hz by JL Audio. It’s only an 8” subwoofer after all. I normally put a 10” in a ported box around 1 cu ft such as the Alpine and Sundown SD3 10 I own.


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## Grinder (Dec 18, 2016)

Precision Ports’ calculator compensates for their own ports’ flared area. Non-flared ports would be commensurately shorter (by something on the order of half the length of the flared portion(s), IIRC). Use this for non-flared ports: Port Length Calculator

Per Precision Ports’ calculator: 
1a) .7 ft^3 at 34.6 Hz = 3” x 21.5” flared port (59.6 m/s)
2a) .7 ft^3 at 34.6 Hz = 4” x 38.5” flared port (33.5 m/s)

Per WinISD:
1b) .7 ft^3 at 34.0 Hz = 3” x 21.3” non-flared port (58.3 m/s)
2b) .7 ft^3 at 33.0 Hz = 4” x 41.3” non-flared port (32.8 m/s) GREEN

If you’ve only got 21.5” for a tube vent, and you want to keep all of that length within the cabinet, you’re stuck with 1a or 1b.

If you can locate the remainder of the vent (beyond 21.5”) outside the cabinet, then 2a or 2b would be preferable in terms of both output and vent noise.

At .7ft^3 you should have zero chuffing with a 4” Precision Port at any tuning. Lesser flaring will be accordingly less effective at reducing chuffing, so do the best you can in this regard.

.244 ft^3 is simply out of the question in terms of useful vent area and/or plausible vent length …while any such “High Fidelity” recommendation would seem to be very much at odds with the SPL design goals and capabilities of this driver (though, apart from vent noise issues, it seems OP has yet to weigh in on their own design goals/preferences in this regard). For example:

.244 ft^3 at 40 Hz = 3” x 46.4” non-flared port (34.5 m/s) BLUE

.244 ft^3 at 31.5 Hz = 3” x 76.2” non-flared port (30.5 m/s) RED

Bear in mind that, at a given vent area, vent velocity goes more or less hand in hand with cabinet volume and SPL (i.e. less cabinet volume = both lower SPL and vent velocity).

Response/SPL:









Vent velocity (m/s):


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## JCsAudio (Jun 16, 2014)

If you give me dimensions A, B, C, and D, than I can model up any box you want with cut sizes. Also, give me an idea of the limits of your dimensions so I can play around with it. Just playing around with this sub some more I think Sundowns recommendations work best. Attached are two models with a vb of .5 cu ft and .8 cu ft (blue) for your comparison, and I used 3" flared port vents. Even with 3" flared ports I am having a hard time fitting them inside the box so again, I need those dimensions to play around with it.

Attached are the two PDF files for these boxes with all the details.


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## allthewayne (Mar 4, 2013)

Grinder said:


> Precision Ports’ calculator compensates for their own ports’ flared area. Non-flared ports would be commensurately shorter (by something on the order of half the length of the flared portion(s), IIRC). Use this for non-flared ports: Port Length Calculator
> 
> Per Precision Ports’ calculator:
> 1a) .7 ft^3 at 34.6 Hz = 3” x 21.5” flared port (59.6 m/s)
> ...


Grinder and V8, your time is very much appreciated.

I agree this .244 business seems ridiculous. I want the output, and will stick with 0.7ft³. However the response of that blue line looks really nice, if only the peak was at 28hz instead of 45hz. Is this possible? 

I'm fine with the port sticking out of the box, It's all under the rear seat and I'd rather get the absolute best performance I can out of it. At this point I'm going to cut the top off this box, remove the slot port and throw a tube in it.

My goals are a 60/40 split of SPL/SQ. I listen to everything except country. 75% of my vehicle listening is low heavy bass rap or electronic. But, I need to be able to throw on some Tool, Max Richter, Local Natives, Ben Howard etc and have it sound good. I want to still have decent output at 25hz if possible. I'm actually debating tuning it to 28-30hz.. cause what do I get, about 3 usable hz below tuning before she unloads? 

I guess what I'm saying is I'd rather a wider playable range over a narrow range of huge SPL. But.. I want that range to start low.

Lower hz needs more power to generate the same db, right? So tuning lower makes sense? I guess I need to learn how to use this software so I can play with how much high end I lose by tuning so low.

I think my plan is to put a 44-45" 4" tube in this current box, with a coupler on the external portion and shorten it until I like what I hear?

I could spend all day modeling it in the software, but I already have a good 0.7ft³ box, I know I want to use a 4" port and a couple feet of it is going to stick out, so I might as well just go for it. haha.


Side question:

When it comes to flaring the internal part of the port, what is the best approach if the top and bottom of the box will contact the port? Should I flare the tube, stick a brace a few inches back from the flare, and then cut the flare flat on the top and bottom so it JUST fits in, and then like silicone the seams where the plastic contacts the wood? My only other option would be to put a bend in and turn the port toward the front of the box to allow more clearance. (cause it's a wedge shape).

Thanks again guys. This thing is pretty impressive as is, I can't wait to hear it with the proper port area!


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## JCsAudio (Jun 16, 2014)

See my responses in red.



allthewayne said:


> Grinder and V8, your time is very much appreciated.
> 
> I agree this .244 business seems ridiculous. I want the output, and will stick with 0.7ft³. However the response of that blue line looks really nice, if only the peak was at 28hz instead of 45hz. Is this possible? The high fs in my opinion is what is making it difficult to get the curve flat below the fs. I'm no expert here but I have noticed this a lot when modeling other drivers and I tried a box on my Alpine at 25 Hz Fb and it sounded muddy. That driver has an fs of 35 hz. I went back to a 34 Hz tune and it sound awesome now.
> 
> ...


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## Grinder (Dec 18, 2016)

I would echo much of this ^^^^^

Adjustable port length (and Vb, via added displacement) in conjunction with in-car experimentation is the best way forward. Even if you don't achieve the results you're after, you'll be a lot closer in the end, and you'll learn a whole lot in the process. According to WinISD, smaller Vb will reduce Fb peak, while higher Fb will also flatten response of this driver. Here's a great thread on Fb and cabin gain (as you probably don't need as low an Fb as you think) https://www.diymobileaudio.com/foru...ven-cabin-gain-reality-do-we-need-low-fs.html


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## JCsAudio (Jun 16, 2014)

IDK if you are open to changing drivers but I own the love my SD3 10 and have it ported. Look at the comparison between the SD3 10 vs that SA 8 in the graph. I'm willing to bet this gets just as loud if not louder than the SA-8 (but check with Sundown) and it is all SQ. Love, love, love mine!

Box spec for this SD3 10 is .98 net tuned to 32.5 Hz.

Edit: adding the same SD3 10 sealed in light blue so you can see comparison in .8 cu ft sealed.


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## Grinder (Dec 18, 2016)

Based on apparent height of OP's cabinet, there doesn't appear to be adequate vertical height (or horizontal clearance) for a 10"

If it were me, and if I could afford it, I might be looking to replace this driver with one that would seem to be more in line with my SQL preferences. However, I might be equally inclined to hold-off and experiment, and learn whatever I could ...and in the end, perhaps even end up with something that I'd be quite pleased with.


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## allthewayne (Mar 4, 2013)

Grinder said:


> Based on apparent height of OP's cabinet, there doesn't appear to be adequate vertical height (or horizontal clearance) for a 10"
> 
> If it were me, and if I could afford it, I might be looking to replace this driver with one that would seem to be more in line with my SQL preferences. However, I might be equally inclined to hold-off and experiment, and learn whatever I could ...and in the end, perhaps even end up with something that I'd be quite pleased with.


This is correct, I can't fit the 10 or I would have for sure gone that route.

I'm happy with the SQ and performance of the SA. Will report back when I get time to rework the port. Thanks again for you guys help!


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