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High Pass Filter for bookshelves

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Mumbles202
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I plan to build some small bookshelves for a pair of PS95s. Idea is for small .11 ported enclosures with a 2" x 1" port that I want to pair with a subwoofer. I'd like to put in a high pass filter for the bookshelves to cutoff at about 100 Hz so the sub can take care of the low frequencies. What's the best way to go about it? 


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123Toid
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@mumbles202

I'm not in front of my computer right now, but I believe the PS95's have a natural roll off around 120hz (sealed). If it were me, I'd first check this out. If you can keep them sealed, you could save yourself the hassle. You would still want a baffle step correction circuit though.

https://www.youtube.com/123toid


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Mumbles202
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@123toid

Ok great. Thats good to know. I was thinking of running them ported initially and then building a Voxel to pair with it but sealed might work out perfect. Definitely would make the build easier. Baffle step would be to correct output levels? 


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123Toid
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@mumbles202

If that is the case, you could still make them ported and use this Lepai amplifier.  It has a built-in high pass at 100hz and is a 2.1 amplifier.  It is the exact one I use in the Dinas.  This would allow you to have the extended bass now and later when you build your Voxel.  In fact (not to sell you on the plans at all) but it would fit perfectly on the back of the voxel redesign I did not too long ago.  It also cuts down on port noise.  Anyway, back to the BSC.

As far as the the BSC goes, I did a video on it here, if you want a more thorough explanation.  But the basic premise is that you loose bass coming at you when you put it in a box.  Without a bsc you will have a tilted response with the highs tilting up about 6db higher than the lows and midrange.  If you watch the video, it shows you the basic starting point of how to design a bsc.  You can also use Xsim or PCD to figure it out.  If you end up coming up with something, we would be happy to look it over for you.  Or even help you design it.  It is only two to three components, so it is very cheap. 

https://www.youtube.com/123toid


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TVOR-Ceasar
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Acoustic Suspension (Sealed box) would work very well with the PS95. At 0.11 CuFt, the box would be tuned to 132 Hz. The -6 dB point would be 66 Hz, which pretty much follows the natural roll off of the driver anyway. Add the Voxel with the active Low Pass Nick links to and you can get it matched up nicely.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Mumbles202
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Thanks for the tips. The plan was either the 2.1 Lepai or the original Dayton DTA2.1 BT amp. I was actually thinking of using the slot Voxel that you designed @123Toid.

I'd want to use the BSC for either sealed or ported?


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Mumbles202
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This may be a stupid question, but when calculating the BSC and entering in the front panel size, if I intend to use a box with a 5" front (so really 4" of internal if I use 1/2" mdf) should I use 5 for the baffle size? 

 

And any issue using pine or another 1x material I might find at a local store? I know I have to account for added material in overall box dimensions but meant more in terms of the material itself. 


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Mumbles202
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I tried modeling this in WinISD and get the following:

winisd ps95

I tried it w/ basically the same settings (.11 vented w/ a 1"x3.3-4" vent) in BassBox but get this:

 

I was hoping for about a 8.25"x5"8" (LxWxD) for the external dimensions using .5" for the wall thickness.


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123Toid
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@mumbles202

You would use 5", wince the baffle step is calculated using the external dimensions. 

Pine is a soft wood and will resonate, typically creating bloated midrange.  If you plan to use Pine, I would consider lining the inside walls with 1/4" mdf.  Or step up to a hard wood or plywood.

ps95

When I look at the PS95-8, it looks really nice in a sealed enclose of .11 cubic feet.  Ported, isn't as nice of a look, but it can be done.  Just pay close attention to the port, you will need a decent sized one to take care of port noise. 

 

https://www.youtube.com/123toid


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Mumbles202
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Posted by: @123toid

@mumbles202

You would use 5", wince the baffle step is calculated using the external dimensions. 

Pine is a soft wood and will resonate, typically creating bloated midrange.  If you plan to use Pine, I would consider lining the inside walls with 1/4" mdf.  Or step up to a hard wood or plywood.

ps95

When I look at the PS95-8, it looks really nice in a sealed enclose of .11 cubic feet.  Ported, isn't as nice of a look, but it can be done.  Just pay close attention to the port, you will need a decent sized one to take care of port noise. 

 

Thanks for the reply. I think I'm going to give it a try with a sealed enclosure and see how I like it. Want to rear mount the driver but hopefully that won't be much of an issue.

I look into some hardwoods. I wanted to build the top/bottom/sides of wood and rhen match the face and rear mdf. Stain/seal the wood and then find a good way to paint the mdf. Just need to figure out some cuts using 45° cuts on the corner to get rid of any joint seems. 


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TVOR-Ceasar
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Point:

With the small size of the box and the desire to only use pine on the sides, plus the fact that you only need to be concerned with inner dimension resonance, the largest surface to contend with would be 7" x 7.25". If it is a concern, you could put an angled brace from about 1/3 the front toward about 5/8 the rear to reduce the possibility of those panels resonating at a lower frequency. The non-symmetrical spacing changes the resonant frequency of the "new" panel sizes. Doing this shifts resonance up higher where there is less energy to excite the panels.

If you use something like yellow pine instead of standard fir, it'll be a big step up since yellow pine is much harder than regular fir. How do I know? Ask me about the floors in my house (1908). Plus yellow pine has a much more distinctive graining than fir. 

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Mumbles202
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@tvor-ceasar thanks for tip. I was think of using Select pine from big box stores and joining some panels side by side to get a true 8". Then I wanted to do the sides/top/bottom in pine w/ 45° joints to keep the joints clean. Then using 1/2" MDF for the front and rear to mount the drivers. I'll try the trick for the bracing.

 

Is there a good way to determine the length of panels when you plan to have the joints like I want? Butt joints I'm fine with, but wanted to preserve the wood grain and just stain it so wanted the nicest looking joints. The inner dimensions will remain the same but trying to see if there is an easy way to determine the overall panel length so I can cut all the panels and glue them at once rather than having to stop and break out the tape between cuts.

 


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Mumbles202
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Thinking about maybe I'll just use Baltic Birch Plywood in 1/2". Solves the finish issue and should be less soft than the pine I think.


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TVOR-Ceasar
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That'll work AND give a really nice finish.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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123Toid
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@mumbles202

I use that a lot and love it. You can even buy veneer edge banding which is iron on. That way it'll look like solid wood. 

https://www.youtube.com/123toid


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