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post #1 of 71 Old 12-20-2016, 05:17 AM - Thread Starter
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Doug's Custom Marty sub thread

*** EDIT - Project complete, original first two posts moved down ***


The subs are complete, in place, and generating MIND BLOWING amounts of bass. Check out the last few posts for overall impressions!



Initial REW pulls, with iNuke barely configured and no treatments or EQ:


Comparing the new Marty pair with the two legacy subs from the "before" pic below:
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post #2 of 71 Old 12-20-2016, 05:24 AM - Thread Starter
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***EDIT - Moving down posts***
Hey everyone, this thread is all about consolidating all of the information for building my new subwoofers, across 2-3 different ones into a single concise location for the thought process from start to end.

First credit goes to @chalugadp whose thread MartySub FAQ pretty much sets the standard for a "How To" for building a ported sub. He does an awesome job of implementing and teaching a ported subwoofer cabinet he learned from @LTD02 . I started my research with this thread, which is a must read for anyone looking to build a well reviewed, great beginner, DIY sub.

After that, I really went down the rabbit hole on DIY. I had just finished my own dedicated HT build, and (intentionally) held opening night with some left-over speaker sets from a combination of Cambridge Soundworks and Bose; so now it was time to replace the entire front soundstage. First project was the new LCR, which were Fusion-15s from DIY Soundgroup, completed yesterday. That means that as of today, we're officially starting on a set of custom Marty subwoofers.

A Marty subwoofer is a design that was intended to make it easier for DIY-ers to build a sub from wood that was easily sourced and cut at a local big box home improvement store. That means: take a typical piece of MDF or plywood (4x8) and rip it into easily divisible pieces, and build a subwoofer. The original plans by LTD02 come in 4 sizes, ranging from Full to Micro, with a Full Marty looking like this:



For my room, I liked the idea of this, but decided I wanted something that fit my own custom soundstage better. I got lots of good advice on how to change it up, and eventually re-designed the entire soundstage, to look like this:



You can see a few different speakers there:
The 4 largest boxes are the "Large Custom Marty", that's what this thread will be building. They're shown in orange and green because I'll build two now (orange) and two later (green).
The 3 next sized (blue) are the "Small Custom Marty", those will be built later, and only if I need them.
The last 3 (orange) are the Fusion-15s, which perform LCR duty, and are already built. This picture below shows them in place on temporary stands, with the pathetic subs now performing duty 'til this thread is complete.



To start the process, I first measured up the soundstage, to see what would fit. It came out that I could fit a subwoofer that was 48" wide, by 84" tall, and get two of them between the LCRs comfortably. Now, for those of us that want to tune a ported sub as low as we can, with best bass, big cabinets are better. The two main problems with that for me are:
1) The cabinet would be HEAVY, since I'm making them out of Baltic birch
2) In addition to being heavy, it'll be an unwieldy nightmare to get up on the stage, back behind the screen wall.
To solve this (somewhat) I broke it down into the two stacks of two subs you see in the picture above.


At this point, it became necessary to model the sub, and since this post is becoming a monster, I'll start a new one for that...
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post #3 of 71 Old 12-20-2016, 05:29 AM - Thread Starter
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***EDIT: Moving down posts***


Ok, once I decided on the exterior size of the cabinet, time for some math and modeling!

If the box will be 48w x 40t x 20d, then we have to do some math to find the interior volume:

Using 3/4" Baltic birch (which is ACTUALLY 3/4), then a box which is 48 x 40 x 20 on the outside has to have the thickness of the boards subtracted. A front, back, top, bottom, left, right sides eat up some volume. We'll actually have two fronts, for added strength and rigidity (double front baffle), so that gives us interior dimensions of:
46.5 x 37.75 x 18.5 = 32474 cu in. Divided by 1728 = 18.79 cu ft for the interior dimensions

From that we have to subtract everything inside the box:
Width braces (8) 46.5 x .75 x 2 = .32 cu ft
Depth braces (8) 18.5 x .75 x 2 = .13 cu ft
Port = 38.35 x 26 x 2 = 1.15 cu ft
Port braces = (6) 38.35 x .75 x 2 = .2 cu ft
Driver = .25 cu ft (est)
That gives us a total of 2.06 cu ft that we have to remove from the interior space, with about 16.74 cu ft of internal volume. That's the first number we start with for our modeling software, to give us a well-tuned box. The Catch-22 for me is "how do you design the box for interior volume, when you need the interior volume of the box to design the port, which goes back to the interior volume of the box?!!?!" The short answer is that I did the math w/o the port, designed (as will be shown below), then fine-tuned the math. It took a couple of back and forths, then I got there.

So, the next thing to do is actually DESIGN the box. For this I used WinISD, and a lot of help in my original thread. I won't try to teach it here, since there are a lot of YouTube videos that do a better job than I could, and threads here too. Short version, here's the graphs I'm working off now:
Starting with the box volume we arrived at above, and using my chosen subwoofer of a Dayton Ultimax 18", with 1000W of power from one of the iNuke6000DSP channels, we have the following expected performance, tuned for a 15Hz low:


Next you can see that I'm within Cone Excursion levels, and how I arrived at the port size:


Lastly you can see a single High-pass filter, and Port Velocity looking good:



All of that combines to make a box that looks like this:



Giving me the following cutlist, using 5x5 Baltic birch:



From there I went and got the wood I needed, and ripped it down to starting sizes. Pics and updates on the woodpile when I get home tonight...
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post #4 of 71 Old 12-20-2016, 05:30 AM - Thread Starter
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post #5 of 71 Old 12-20-2016, 07:01 AM
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All looks good to me. I doubt you'll need the smaller subs, but more is usually better.

The F15s seem high to me. Is your seating elevated? They're already on a riser and then on stands. The tweeters should be close to ear height unless you have tiered seating.
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post #6 of 71 Old 12-20-2016, 07:48 AM - Thread Starter
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Quote:
Originally Posted by Samps View Post
All looks good to me. I doubt you'll need the smaller subs, but more is usually better.

The F15s seem high to me. Is your seating elevated? They're already on a riser and then on stands. The tweeters should be close to ear height unless you have tiered seating.


Yeah, the thoughts on the smaller ones was "if I'm going to have to put the F15s on something, why NOT 3 more subs?"


They're sitting at what I thought was "middle of the screen height". I didn't know if the woofer or tweeter should be the absolute middle, so I just split the difference. I do have tiered seating, w/a 12" rise b/w the first and second row. Does that make my idea of "center of the screen to sound best" right or still wrong?
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post #7 of 71 Old 12-20-2016, 10:28 AM
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Are you positive your 3/4" baltic birch is actually 3 /4"? The 3/4" baltic birch I used in my recent projects has all been . 71" thick.

Your front wall design looks great! I bet you will be pleased with the results.

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post #8 of 71 Old 12-20-2016, 10:53 AM - Thread Starter
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Are you positive your 3/4" baltic birch is actually 3 /4"? The 3/4" baltic birch I used in my recent projects has all been . 71" thick.

Your front wall design looks great! I bet you will be pleased with the results.

You know, I'll have to bust out the calipers and measure. I just threw a tape next to it and looked to make sure it wasn't actually 5/8, I'd never have noticed a 4 hundredths of an inch difference.


Thanks, and BTW, I followed your JBL-blue main speaker build. Very impressive attention to detail, and I suspect that I'm about to feel your pain on moving something of their weight class!
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post #9 of 71 Old 12-20-2016, 12:57 PM
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Yes you are going to feel the pain, stacking them is going to be fun!!!!

End result will be worth it.

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post #10 of 71 Old 12-20-2016, 02:39 PM
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Quote:
Originally Posted by Samps View Post
The F15s seem high to me. Is your seating elevated? They're already on a riser and then on stands. The tweeters should be close to ear height unless you have tiered seating.
This may be an ignorant question, but can you turn them upside down to have the tweeters lower or would that make them unstable due to weight? Looks like a helluva wall you're building Doug.
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post #11 of 71 Old 12-20-2016, 04:40 PM - Thread Starter
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This may be an ignorant question, but can you turn them upside down to have the tweeters lower or would that make them unstable due to weight? Looks like a helluva wall you're building Doug.
Not ignorant, as I was reading I was thinking "Hmm, I wonder if they COULD be upside down?"

If I were going to lower them, it would be simple tho. Those boxes they're on are just 4 pieces of 2x12, screwed together w/3" screws and L-braces. I could prob take 'em apart, cut down the long sides, put 'em back together, and have everything back in place in about 15 mins. The hardest part would be moving each F-15 2x.
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post #12 of 71 Old 12-20-2016, 04:50 PM - Thread Starter
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More fun today. All of the pieces have been ripped down to width, and I'm in the process of cutting them down to length. This is what 8x BB looks like, after ripping it down, and that's a 48" drywall T-square for reference:



To answer your earlier question @NWCgrad :


Question: Does anyone know, or know where I can find, the dimensions for my cutouts on the Dayton UM 18"s?

(The one flaw with building the cabinet in preparation of the subs being delivered by Santa...)
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post #13 of 71 Old 12-20-2016, 04:57 PM
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post #14 of 71 Old 12-20-2016, 06:13 PM - Thread Starter
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Ok, so I should use the 462mm (18.2") and 422mm (16.6")? How trustworthy are those numbers?


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post #15 of 71 Old 12-20-2016, 06:16 PM
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I've had good luck with daytons specs but you might want to wait for someone with this driver to chime in. The hole cut is hard to fix if it's wrong.
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post #16 of 71 Old 12-20-2016, 06:18 PM
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Looking good. You're definitely going to have a significant sound improvement.
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post #17 of 71 Old 12-21-2016, 05:01 AM - Thread Starter
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Quote:
Originally Posted by Samps View Post
I've had good luck with daytons specs but you might want to wait for someone with this driver to chime in. The hole cut is hard to fix if it's wrong.
Lol, #truth!!

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Looking good. You're definitely going to have a significant sound improvement.
Thanks! And it's totally just a coincidence that the wall I'm building bears a striking similarity to your avatar, I swear!
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post #18 of 71 Old 12-21-2016, 10:29 AM
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Thanks! And it's totally just a coincidence that the wall I'm building bears a striking similarity to your avatar, I swear!
I don't lay claim to even my layout. I'm going to ask my brothers to help me lift the Stonehenges on top of the Cyclops subs. I hope to fix my computer before then so that I can take some measurements before I move them.
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post #19 of 71 Old 12-21-2016, 10:59 AM
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for a surface mount, non-recessed driver, all the 18's I've cut for in that mode use the 16.6-ish +/- dimension

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post #20 of 71 Old 12-21-2016, 11:56 AM
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I cut the boards for my Cyclops subs in the driveway (MDF has nasty dust/exhaust), and then I moved the pieces downstairs and glued them together there. These bad boys are gonna be sold with the house. While they lack significant depth, the length (49") and width (30") are unwieldy. If you plan to sand them down after construction, please keep that in mind. I used more finishing compound (spackling) than I should've assuming that I would've simply been able to sand it down. Unfortunately, that decision lacked the foresight necessary for the amount of dust that sanding vinyl spackling with an orbital sander would emit. Upon starting to sand down my cabs, I promptly regretted my liberal application of the spackling.
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post #21 of 71 Old 12-21-2016, 04:31 PM
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Doug,

I just measured a ultimax last week, for a project I'm working on....

Here's are the measurements.

Outside Frame measurement, actual dimension, measured with digital calipers = 18 3/16. So, if you you are flush mounting it, I'd make the hole size for the outermost most baffle 18.25 inches.

If you are not flush mounting, the Driver measures an actual 16 9/16, so Id make the cutout 16.6 inches, so you have the slightest bit of wiggle room.

hope that info helps / I'm looking forward to seeing you get this done and hearing your thoughts on your new setup.
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post #22 of 71 Old 12-22-2016, 11:06 PM
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hey doug,
looks like a fun project. just saw your thread. one thing that you might want to keep in mind is the air blowing out of the top set of subs on the screen might cause a little vibration in the screen depending on how close the subs are to it, the nature of the perforations, and of course the amount of wind being generated. :-) flipping the top cab so the port are at the top should keep most of the wind off the center of the screen.
also, someone else mentioned the f15's may be a little high if you aren't trying to shoot them over the front row to get to the back row. if yours is just a one row theater, and you can lower them down or even aim/tilt them down a hair, they may sound just a smidge better.
i suspect that once you are all up and running, the 4 big ported cabs and the triple 15" high sensitivity mains in your room will be more than "sufficient". ;-) then again...one never knows...

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post #23 of 71 Old 12-22-2016, 11:14 PM
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also, i see you are planning on running the um18. usable excursion on that one is closer to 28-30mm or a little higher, so no worries about bottoming out in the peak excursion region above the tuning point. also rated power is 1kw rms. spec'd that way the driver can handle short bursts of much more without cooking itself, so long as it isn't extended duration sine waves or something similar. many folks are running that driver on the 6000dsp with no limiter and no problem. a limitation on that amp is the current that it can pull from the wall. 10 amps per channel is about it before it starts 'complaining'. you probably won't hit that unless you are going for demo type stuff with tons of content right near/on the tuning frequency or if you tend to run your bass crazy hot.
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post #24 of 71 Old 12-23-2016, 04:18 AM - Thread Starter
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hey doug,
looks like a fun project. just saw your thread. one thing that you might want to keep in mind is the air blowing out of the top set of subs on the screen might cause a little vibration in the screen depending on how close the subs are to it, the nature of the perforations, and of course the amount of wind being generated. :-) flipping the top cab so the port are at the top should keep most of the wind off the center of the screen.
also, someone else mentioned the f15's may be a little high if you aren't trying to shoot them over the front row to get to the back row. if yours is just a one row theater, and you can lower them down or even aim/tilt them down a hair, they may sound just a smidge better.
i suspect that once you are all up and running, the 4 big ported cabs and the triple 15" high sensitivity mains in your room will be more than "sufficient". ;-) then again...one never knows...
Wow, thanks for the input! I dig the idea of flipping the top sub, I'll have to check the measurements to see if that will put it above the top of the screen or right at the top.
It's a two row theater, and the MLP may be up for debate right now. I originally planned for front center to be MLP, but I'm finding that I actually prefer back center. I'm just now getting into REW and my acoustic treatments, and I've been doing all my measurements with the back row as MLP.
I don't think it'll be sufficient, I strongly suspect that I'll need some near-field subs either embedded in the side walls or behind the back row.

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also, i see you are planning on running the um18. usable excursion on that one is closer to 28-30mm or a little higher, so no worries about bottoming out in the peak excursion region above the tuning point. also rated power is 1kw rms. spec'd that way the driver can handle short bursts of much more without cooking itself, so long as it isn't extended duration sine waves or something similar. many folks are running that driver on the 6000dsp with no limiter and no problem. a limitation on that amp is the current that it can pull from the wall. 10 amps per channel is about it before it starts 'complaining'. you probably won't hit that unless you are going for demo type stuff with tons of content right near/on the tuning frequency or if you tend to run your bass crazy hot.
Thanks for the info on the um18s. I haven't even opened the manual for the 6000 yet, but I'll keep that in mind. I have a dedicated 20A circuit with a power conditioner (Furman Elite 20), so I should be able to set them up right. Worst case scenario: The main house panels are about 10' away from the server rack.
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post #25 of 71 Old 12-23-2016, 10:17 AM
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Wow, thanks for the input! I dig the idea of flipping the top sub, I'll have to check the measurements to see if that will put it above the top of the screen or right at the top.
It's a two row theater, and the MLP may be up for debate right now. I originally planned for front center to be MLP, but I'm finding that I actually prefer back center. I'm just now getting into REW and my acoustic treatments, and I've been doing all my measurements with the back row as MLP.
I don't think it'll be sufficient, I strongly suspect that I'll need some near-field subs either embedded in the side walls or behind the back row.


Thanks for the info on the um18s. I haven't even opened the manual for the 6000 yet, but I'll keep that in mind. I have a dedicated 20A circuit with a power conditioner (Furman Elite 20), so I should be able to set them up right. Worst case scenario: The main house panels are about 10' away from the server rack.
It won't be sufficient. You'll want something nearfield. You may also want something near for ULF and a couple nearfield MBMs. Hope you have space. We'll convince you whether you need it or not. @LTD02 helped me with my Cyclops subs and my nearfield MBMs, so he's definitely the one to consult.
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post #26 of 71 Old 12-23-2016, 06:00 PM - Thread Starter
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Originally Posted by VicTorious1 View Post
It won't be sufficient. You'll want something nearfield. You may also want something near for ULF and a couple nearfield MBMs. Hope you have space. We'll convince you whether you need it or not. @LTD02 helped me with my Cyclops subs and my nearfield MBMs, so he's definitely the one to consult.
No doubt, I can already tell that I'm going to need at least 2 more 15s.

There's good and bad news on today's progress.

First off, got all the sides prepped w/their handle cutouts, so they're all ready for assembly:



More good news:
I got a really good looking baffle cut out, to the specs I got, and ready for the port:


The bad news is that I cut out 4 baffles (2x fronts each, 2 speakers), and that's the only one that isn't wrong.
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post #27 of 71 Old 12-23-2016, 06:11 PM - Thread Starter
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I just made my final tweaks to WinISD for the last layout, updated the graphics in the second post, and could use a set of eyes for a sanity check.

@LTD02 since you're the man @ this, I'd really appreciate it if you could let me know if I missed something, before I build and install the port...
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post #28 of 71 Old 12-26-2016, 04:17 AM
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looks pretty good so far. just a few minor bits:
- the cab volume calculation appears to have been for a 26"x2" port, so with a 2.5" port cab volume will be a hair lower.
- the port boards appear to be 26" wide in your cut plan. the port was modeled as 26" in winisd. since there are sides and braces, the effective width of the port won't be the full 26". so if you want the performance of a 26" port, then the actual port boards would need to account for the space lost to the vertical braces and to the sides of the port. so with 3 port braces and 2 port sides, 5 x 0.75" =3.75" needs to be added to the total width of the port boards.
- for a slot port, the effective length of the port is a little longer than the actual measured length of the port itself. for your cab, this works out to roughly 5 inches or so. so if winisd indicates to build a port 39" long, then when you actually build it, built the port 34" long. otherwise your tuning will come in lower than your target.
i haven't double checked all of the measurements, but the size of the cab and the port (with the adjustments in the previous two points) look pretty much on target.
also, don't drive yourself too crazy over getting everything exactly perfect. if the final cab ends up being tuned +/- 1 hz off target, don't worry about it, it will still perform great.
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post #29 of 71 Old 12-26-2016, 04:32 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
looks pretty good so far. just a few minor bits:
- the cab volume calculation appears to have been for a 26"x2" port, so with a 2.5" port cab volume will be a hair lower.
- the port boards appear to be 26" wide in your cut plan. the port was modeled as 26" in winisd. since there are sides and braces, the effective width of the port won't be the full 26". so if you want the performance of a 26" port, then the actual port boards would need to account for the space lost to the vertical braces and to the sides of the port. so with 3 port braces and 2 port sides, 5 x 0.75" =3.75" needs to be added to the total width of the port boards.
- for a slot port, the effective length of the port is a little longer than the actual measured length of the port itself. for your cab, this works out to roughly 5 inches or so. so if winisd indicates to build a port 39" long, then when you actually build it, built the port 34" long. otherwise your tuning will come in lower than your target.
i haven't double checked all of the measurements, but the size of the cab and the port (with the adjustments in the previous two points) look pretty much on target.
also, don't drive yourself too crazy over getting everything exactly perfect. if the final cab ends up being tuned +/- 1 hz off target, don't worry about it, it will still perform great.
This is exactly what I was looking for, thanks!

- I did change the port height, when I adjusted internal volume from 14 to 16.75 cf, and forgot to adjust the vol, good catch
- I was thinking about the end pieces for width, but not the middle ones effecting tuning, thanks!
- Is this difference in effective length of the port due to the corner where it goes from horizontal (along the bottom in my case) to vertical (along the back) at the bend? I was thinking about this the other day and was going to ask. It sounds like the answer is "just shorten the back 5"?
- I'll get it to as close as I can, but that last statement answers one of my last questions: What happens if I'm off by an inch or two? It sounds like it'll just change the tune a Hz or so?

Thanks again for the feedback!
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post #30 of 71 Old 12-26-2016, 04:44 AM
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the difference in path length vs model is from how the air behaves as it leaves the subwoofer itself (and how the air enters the main part of the sub on the inside from the port). your length calculation that runs down the center of the port is the correct way to measure it. the corner/bend, perhaps surprisingly, has an almost insignificant impact on tuning.


if you are off by an inch or two on the port, that won't matter at all.

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