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Peerless STW-350F Potential Alignments

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  • Peerless STW-350F Potential Alignments

    Per other discussions on the Peerless STW-350F, I decided to post some of the possible alignments for this amazing driver. My models are by no means all-inclusive, and if you take a step back before nit-picking for a few hz extension, or a few more dB, they can look very similar. I've taken the liberty of correcting the models with DSP for a smooth response with a nicely shaped rolloff. I limited the DSP corrections to two inputs: a HP filter and single band parametric EQ.

    Also, I tweaked the models until I maxed out a limiting factor: either the 1550 watts available from my Crown XLS 1500 (with the exception of the sealed model which I "used" the XLS2000 I have on the shelf), PR excursion and/or weight limit, or vent air speed of ~20m/s for a "reasonably sized vent" at half power. The last limiting factor has some wiggle room as to what is considered reasonably sized and the vent could be increased, but I tried to keep port self-resonance above 100 hz (which is considered by many to be too low, but for this purpose, I used it as the limit). Of note - by employing a HP filter that changes the sub 15hz FR by a virtually imperceptible amount, Xmax NEVER became the limiting factor.

    What I've found is that this appears to be an incredibly versatile driver! Each of the alignments, IMO, has it's own advantages and disadvantages. Typically, the biggest difference is going to be enclosure size. So here's what I've got. Hopefully, my pics of Transfer Function Magnitude, SPL, Cone Excursion, Rear Port Air Velocity, and PR Cone Excursion will show up.

    Now, I just have to decide which box to build first...

    #A in AquaMarine - Factory recommended 4.6 cu.ft vented enclosure
    Tuning: 18 hz
    F3: 16hz
    Power In: 1000 watts
    Vents: [email protected] 4" x 42.67
    Filters: None

    Strengths and weaknesses: A superb blend of SPL and low end extension. Box size is quite reasonable but a touch larger than most other alignments, vents aren't horribly long (can easily be converted to a slot port that fits in a cubed enclosure). No DSP required. I'm blown away by how good this looks for a factory recommended enclosure. It could take more power with the tradeoff of increased port velocity.

    #B in Green - Quasi-LLT in 8 cu.ft enclosure

    Tuning: 13 hz
    F3: 12 hz
    Power In: 1100 watts (1200 watts possible)
    Vents: [email protected] 4" x 4" x 60
    Filters: [email protected] hz Q:1, [email protected] Q1 Gain2db

    Strengths and weaknesses: Absurd low end response for a 15, IMO. Flattens out easily with minimal EQ. Limited by amp power using necessary EQ, but maintained virtually the same SPL as #A with better extension. Largest box of the bunch, but still not huge. Vents would still fit inside a cubed box by folding it. Cone excursion is very high at full power but still below Xmech.

    NOTE: if you follow the LLT design philosophy, you will notice that this meets most of the criteria for an LLT, with the exception of the enclosure size not be ginormous. The BIG advantage of this is shifting the port tuning to the infra-sonic range; notice that even though at full power the port velocity is ~40m/s, it is pushed way down in the spectrum where you are very unlikely to get full power bursts. Also, the vent speed is only ~12m/s at 20 hz and above - at full power!! At that point, the driver is still contributing a large amount of the sound instead of the port. Plus, did we mention the awesome extension?

    #C in Blue - Sealed for a QTC of .707ish in 1.87 cu.ft

    Tuning: --
    F3: 18 hz
    Power In: 320 watts (but requires 2000+ watts with boost!!!!)
    Vents: --
    Filters: HP--, [email protected] Q2 Gain10db!!

    Strengths and weaknesses: Tiny box!! This is smaller than most tower speakers! Still has an amazing FR response suitable for HT, almost matching the vented response. The big downsides are that it requires much more power and DSP to get there, and the total SPL is nearly 6db below the other alignments. But it still reaches 109 db and is capable of more before reaching Xmech - albeit requiring gobs and gobs of power. IT appears that 5000 watts of input power could put this sealed enclosure closer to on par with the vented alignments...

    #D in Light Blue - Small 3.5 cu.ft enclosure

    Tuning: 20 hz
    F3: 18 hz
    Power In: 1000 watts
    Vents: [email protected] 4" x 4" x 58
    Filters: None required but a [email protected] Q0.9 works very well to limit excursion below 15hz while raising F3 a tad.

    Strengths and weaknesses: A great blend of SPL and extension - a tad higher SPL (115db above 25hz) and a tad less extension than the other two vented enclosures, but in a much smaller box. Still gives a sub-20hz f3 with a softer knee. Vents are about the same as the 8 cu ft enclosure but doesn't tune as low (obviously). If you don't have the room for a bigger cabinet, this looks like a viable option. With the vents, driver, and minimal bracing, this would be a 21" cube, methinks. Even though this is a "compromise" vented alignment, it's really not...

    #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).

    #F in Pink - Pair of Slaps M12 PR in 4 cu.ft

    Tuning: 18.85 hz
    F3: 17.5 hz
    Power In: 1000 watts
    Vents: --
    Filters: [email protected] Q.95
    PR Wt: 500 grams per PR

    Strengths and weaknesses:Has some of the same limitations as the APR12's, but with some advantages. Plays a DB or two louder than the APR12's due to larger PR excursion, but won't tune as low due to limited amount of mass that can be placed on the PR. NO PORT NOISE!!! Still has great overall FR response but rolls off faster due to the steeper PR natural rolloff combined with the HP filter needed to keep the PR's happy.Lowest cost PR design as it only requires two less-expensive PRs.

    #G in Purple - Quartet of Slaps M10 PR in 4 cu.ft

    Tuning: 19.11 hz
    F3: 17.8 hz
    Power In: 1400 watts
    Vents: --
    Filters: [email protected] Q0.909, [email protected] Q1 Gain1
    PR wt: 450 grams per PR

    Strengths and weaknesses: Slightly smaller box and higher tuning to control PR excursion. Requires four PR's instead of two but capable of more power and SPL but with a sharper rolloff like the M12 setup. NO PORT NOISE!!!

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    • #3
      Even though you didn't ask, I vote for light blue (+ $ave the PR expen$e ! - gotta love that).


      • #4
        Maybe I should turn this in to a vote since I can't decide what to do. I might just have to build a couple of these designs and see what I like best. I guess it's a good thing to have several options for alignments instead of 'this driver really only works well is enclosure X'. Last night I disassembled my HT18 in a 24.5" cubed enclosure which will go to a friend's house. The smaller box would help me sneak a pair of them in to the house...


        • #5