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After enjoying the heck out of my Peerless STW350F subwoofer, I needed to change up a few things. Originally, I settled on about 3.5 cuFt net in a vented box tuned in the high teens; I debated much over what configuration to go with in this thread:
https://techtalk.parts-express.com/f...ial-alignments
.. and I eventually covered the build in this thread...
https://techtalk.parts-express.com/f...350f-enclosure
But a little while back, all of the gear was moved to a different room with a different layout. Unfortunately, that layout wasn't conducive to good bass with where the subwoofer needed to go. And the box was kind of big and little bit of an eyesore (to some, I'm told..) for where it was placed in the room. There were a few nulls from the space and placement that led me to be dissatisfied with the in room performance. The subwoofer certainly didn't underperform, I just needed to move the subwoofer and there weren't very many good places to put it. My options were limited, and the box limited that even more. I eventually snuck it to the back corner of the room, which yielded much better results, but still had some issues. One issue in particular was that now it was closer to seating area, so I could hear more of the mechanical noise produced by the behemoth motor with extensive venting.
Eventually, my better half decided that the room needed some bookshelves, and those bookshelves were going right where the sub was. So a new design was in order. Luckily, I've had some experience integrating subwoofers in to cabinetry, so after putting some bookshelf designs on paper, I had some rough starting dimension for a new enclosure. The dimensions for the base cabinet that would become the subwoofer are a little flexible, but for uniformity's sake, I tried not to vary more than a couple of inches. And instead of making maple-flavored sawdust first in the form of new bookshelves, I decided to make formaldehyde-flavored MDF dust first to make sure the new design would be satisfactory.
I decided to go with a trio of CSS Audio APR12 passive radiators. I purchased a few of them a while back when they had some B-stock units (should have bought more, darn it!) so I had them on hand. It was between the APR12's and Earthquake SLAPS M12's; the SLAPS M12 has more Xmax but doesn't support as much weight, white the CSS units handle MUCH more weight and appear to be more reputable (I struggled to find and official answer for the SLAPS M12 unit as one spec was kind of listed in the owner's manual, and another cautionary spec listed in some other documentation from the MFG via some interweb meanderings). It requires three or four APR 12's to do what two or three SLAPS units can do, so APR12's are definitely the more costly route.
From one of the threads above...:
"#E in Red - Quartet of CSS APR12 PR in 4 cu.ft
Tuning: 17.9 hz
F3: 16 hz
Power In: 750 watts
Vents: --
Filters: [email protected] Q1 Gain1
PR Wt: 1100 grams per PR
Strengths and weaknesses: Lowest tuning I could find with PR's. Adds significant cost for FOUR PR's. A pair or triplets of PR's could tune lower, but would limit SPL and amplifier input. Already limited amplifier input due to excursion limits of PR. NO PORT NOISE!!! A slightly sagging response which could be fixed with a HP filter @ 14 hz, Q of 1, but it would cost you 100 watts and some SPL (But not much as the sag would be gone). Best PR alignment I could find. Rolloff mimics a vented enclosure instead of the additional 6db/octave typical of other PR setups (like the two below).​"
​
I found that I could achieve approximately the same tuning with three passives instead of four by limiting power in to 750 watts without the PEQ, and only loading 800 grams or so on each passive. It gives a slightly drooping anechoic response (1-1.5 db from 35 to 18 hz). Since I haven't swapped out my crown XLS 1500 for the XLS 2000, or added a second XLS1500, I figured I would power both of the subs off of one amp, feeding them 525 watts each. That should keep PR excursion in check. The subwoofer itself doesn't care about over excursion. It laughed at the full power attack of the XLS1500 down to 10 hz where the amp choked.
Oh, did I say BOTH subwoofers?? Yup, you heard that right. We had TWINS!! I stashed away a second STW350F before they became endangered, and then NLA. So happy day for me
The next challenge was figuring out how to fit three passive 12" radiators and one giant 15" subwoofer in to a small box. I was aiming for as small as 2.4 cu ft (ideal sealed box was right around 2.2 cu ft), but unlike most subwoofer builds where you are almost compromising the extra box volume for a higher WAF, I actually had to add more volume to make it all work. In order to keep the passives and drive from interfering, I needed around a 20" wide baffle. In order to fit two passives height wise, I needed a 26" tall box. And to physically put the passives on the side of the box, I needed a minimum of a 13" deep box. So after some maths, a 26x20x13 box yields right around 3 cu ft gross. Subtract driver volume and I'm closer to 2.6 or 2.7 cu ft. That will work.
WinISD shows around an 18 hz f3 with tuning around 16 hz. That happens to be almost identical to the vented enclosure I was using, except a slightly sharper rollofff due to the passives being 5th order instead of 4th order. So, off to make some sawdust!
​
​
https://techtalk.parts-express.com/f...ial-alignments
.. and I eventually covered the build in this thread...
https://techtalk.parts-express.com/f...350f-enclosure
But a little while back, all of the gear was moved to a different room with a different layout. Unfortunately, that layout wasn't conducive to good bass with where the subwoofer needed to go. And the box was kind of big and little bit of an eyesore (to some, I'm told..) for where it was placed in the room. There were a few nulls from the space and placement that led me to be dissatisfied with the in room performance. The subwoofer certainly didn't underperform, I just needed to move the subwoofer and there weren't very many good places to put it. My options were limited, and the box limited that even more. I eventually snuck it to the back corner of the room, which yielded much better results, but still had some issues. One issue in particular was that now it was closer to seating area, so I could hear more of the mechanical noise produced by the behemoth motor with extensive venting.
Eventually, my better half decided that the room needed some bookshelves, and those bookshelves were going right where the sub was. So a new design was in order. Luckily, I've had some experience integrating subwoofers in to cabinetry, so after putting some bookshelf designs on paper, I had some rough starting dimension for a new enclosure. The dimensions for the base cabinet that would become the subwoofer are a little flexible, but for uniformity's sake, I tried not to vary more than a couple of inches. And instead of making maple-flavored sawdust first in the form of new bookshelves, I decided to make formaldehyde-flavored MDF dust first to make sure the new design would be satisfactory.
I decided to go with a trio of CSS Audio APR12 passive radiators. I purchased a few of them a while back when they had some B-stock units (should have bought more, darn it!) so I had them on hand. It was between the APR12's and Earthquake SLAPS M12's; the SLAPS M12 has more Xmax but doesn't support as much weight, white the CSS units handle MUCH more weight and appear to be more reputable (I struggled to find and official answer for the SLAPS M12 unit as one spec was kind of listed in the owner's manual, and another cautionary spec listed in some other documentation from the MFG via some interweb meanderings). It requires three or four APR 12's to do what two or three SLAPS units can do, so APR12's are definitely the more costly route.
From one of the threads above...:
"#E in Red - Quartet of CSS APR12 PR in 4 cu.ft
Tuning: 17.9 hz
F3: 16 hz
Power In: 750 watts
Vents: --
Filters: [email protected] Q1 Gain1
PR Wt: 1100 grams per PR
Strengths and weaknesses: Lowest tuning I could find with PR's. Adds significant cost for FOUR PR's. A pair or triplets of PR's could tune lower, but would limit SPL and amplifier input. Already limited amplifier input due to excursion limits of PR. NO PORT NOISE!!! A slightly sagging response which could be fixed with a HP filter @ 14 hz, Q of 1, but it would cost you 100 watts and some SPL (But not much as the sag would be gone). Best PR alignment I could find. Rolloff mimics a vented enclosure instead of the additional 6db/octave typical of other PR setups (like the two below).​"
I found that I could achieve approximately the same tuning with three passives instead of four by limiting power in to 750 watts without the PEQ, and only loading 800 grams or so on each passive. It gives a slightly drooping anechoic response (1-1.5 db from 35 to 18 hz). Since I haven't swapped out my crown XLS 1500 for the XLS 2000, or added a second XLS1500, I figured I would power both of the subs off of one amp, feeding them 525 watts each. That should keep PR excursion in check. The subwoofer itself doesn't care about over excursion. It laughed at the full power attack of the XLS1500 down to 10 hz where the amp choked.
Oh, did I say BOTH subwoofers?? Yup, you heard that right. We had TWINS!! I stashed away a second STW350F before they became endangered, and then NLA. So happy day for me
The next challenge was figuring out how to fit three passive 12" radiators and one giant 15" subwoofer in to a small box. I was aiming for as small as 2.4 cu ft (ideal sealed box was right around 2.2 cu ft), but unlike most subwoofer builds where you are almost compromising the extra box volume for a higher WAF, I actually had to add more volume to make it all work. In order to keep the passives and drive from interfering, I needed around a 20" wide baffle. In order to fit two passives height wise, I needed a 26" tall box. And to physically put the passives on the side of the box, I needed a minimum of a 13" deep box. So after some maths, a 26x20x13 box yields right around 3 cu ft gross. Subtract driver volume and I'm closer to 2.6 or 2.7 cu ft. That will work.
WinISD shows around an 18 hz f3 with tuning around 16 hz. That happens to be almost identical to the vented enclosure I was using, except a slightly sharper rollofff due to the passives being 5th order instead of 4th order. So, off to make some sawdust!
​
​
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