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Double 10" Sealed Enclosure Advice please

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Jack1991 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2020 at 8:21pm
Right i think i got it. I have gone for a square slotted port heres a photo of the style i would potentially like to make the mid range box, but with the slot on the bottom instead. The sizes i have put in WINISD is just for 1 speaker enclosure. As i want to make sure i understand and got it correct.

Not shown in the photo but i have also put the high pass filter on too @ 100hz


 
Doesnt have to be square slotted. Happy to have round ports and different shape enclosure. Just for example to check i understand it correctly now?


Edited by Jack1991 - 15 April 2020 at 11:58am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Peter Jan Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2020 at 5:19pm
Looking good  Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2020 at 5:26pm
Originally posted by Peter Jan Peter Jan wrote:

Looking good  Thumbs Up

I assume by that i have done it correctly Peter! 😀




Edited by Jack1991 - 15 April 2020 at 5:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2020 at 7:00pm
I have read how you need to be ALOT more precise when building ported enclosures, compared to sealed.

I like to be as precise as i can woth things in general but i would like to know exactly how close you do need to be realistically when building a ported enclosure? Is it say within 1 to 2cm³  or is it a bit more leanient than that?

I imagine its hard to out an exact number on it but if i can get a rough idea
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 15 April 2020 at 7:21pm
Hi there is some leeway more than 1 cm... But more prominently there will be some differences from sim to reality.
Enclosure Shape, effective shape of port and placement in the box, actual driver T/s parameters will have an effect and change the tuning a bit.

Good practice would be test the enclosure before sealing it so you can check and adapt the port once measured , often this means shortening the duct as usually the port acts as it was longer than in the sim thanks to nearby walls.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2020 at 8:16am
Cool okay thanks. Because i was thinking things like speaker cable and speakon socket does that need to be measured and taken into consideration aswell? I would assume so.

Actually i just thought, i will have a look on winisd adding & subtracting a few cm³ and see what the overall result is. 🙂👍🏼


Edited by Jack1991 - 16 April 2020 at 8:18am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Peter Jan Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2020 at 10:13am
Volume is indeed always net volume, so you have to take into account all these things that take up space inside the cab. Barhandles, the speaker(s), bracing and the BR port(s). Do a rough calculation of all these things when determining the final cab size. It does certainly not listen to a few cm³ even a liter doesn't do all that much.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2020 at 9:31pm
Right fairly sure i got this correct now. Would be grateful if someone could check it to make sure i am correct though. I have completely changed the driver & box design from yesterday and also gone with a round port instead.

The photo with the design on is exactly to size. Just without the top on obviously so you can see inside. It has a 10cm port, 11.5cm long.

I have made each chamber 26.695 Litres as this includes displacement total of driver/port/cable etc.

I dont know what 'Alignments' is on WinIsd. So i selected the top one which is called QB3. I also tried Chebychev too and it made no difference. So went with QB3 in the end.

I am going to use a Passive Crossover to go from the Mids to the Tops. I havent accounted for that yet on winisd as i wanted to ask, is that just add in a low pass filter at 2.5khz the crossovers point, or is there more to it than that?

Also is it better to have a steep or shallow roll off? My instinct is shallow would be better but im not sure?








Edited by Jack1991 - 17 April 2020 at 12:18pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Peter Jan Quote  Post ReplyReply Direct Link To This Post Posted: 17 April 2020 at 9:06pm
Originally posted by Jack1991 Jack1991 wrote:

Right fairly sure i got this correct now. Would be grateful if someone could check it to make sure i am correct though. I have completely changed the driver & box design from yesterday and also gone with a round port instead.
The photo with the design on is exactly to size. Just without the top on obviously so you can see inside. It has a 10cm port, 11.5cm long.
I have made each chamber 26.695 Litres as this includes displacement total of driver/port/cable etc.

Seems correct all the way.
BR ports can be anywhere, just make sure the cab can be placed with the port(s) fairly free at all times ( not against a wall or something ).
The center panel can be left out, doesn't make make any difference or cut out some wood to save some weight, so it still acts as bracing. makes it also easier for cabling inside.
Probably cover all sides with a layer of damping material, as it is a mid cab and very likely needs some damping to avoid cab resonances/standing waves inside the cab.


Originally posted by Jack1991 Jack1991 wrote:

I dont know what 'Alignments' is on WinIsd. So i selected the top one which is called QB3. I also tried Chebychev too and it made no difference. So went with QB3 in the end.

There's not much difference between QB3 or Chebychev allignment, but there is more with the other allignments. It all depends what the purpose of the cab is going to be, to choose one or the other as a starting point, but it doesn't matter what you start with as you can tweak volume and tuning around at will.


Originally posted by Jack1991 Jack1991 wrote:

I am going to use a Passive Crossover to go from the Mids to the Tops. I havent accounted for that yet on winisd as i wanted to ask, is that just add in a low pass filter at 2.5khz the crossovers point, or is there more to it than that?

You can put a lowpass filter in WinISD to get the general idea visually, but WINISD isnt meant for that. You need to have a lowpass on the midspeakers and an highpass on the tweeter/horn-driver.
Depending on the used components ( their sensitivity ) you need to attenuate one or the other to match them loudness-wise, usually the highs are the loudest as they tend to be more sensitive than larger cone speakers.


Originally posted by Jack1991 Jack1991 wrote:

Also is it better to have a steep or shallow roll off? My instinct is shallow would be better but im not sure ?

Passive filters are to be calculated on the specific speaker components, especially their impedance at/around crossover point. No speaker(s) are exact 8 Ohm (or 4 Ohm or ... ) over their entire range. The speakers connected to passive crossovers are an integral part of that crossover circuit, so speaker impedance ( impedance curve comes in handy here ) has to be accounted for.
Active filters, like the ones in your Pioneer amp, don't have that impedance "problem" to consider.
Shallow or steep is not a matter of one being better than the other by definition. What is used when or where or why, depends on many considerations. The simplest form ( 6dB/octave slope ) meaning the least amount of components, sometimes does it just fine, when speaker components can take it. A woofer or mid speaker doesn't mind "too much" highs from a technical standpoint, sound can be another thing though. High speakers ( tweeter or horn/driver ) on the other hand are not made to support lower frequencies, so their crossover frequency and/or slope steepness comes into play. Other than that, what sounds best at what crossover frequency can also be a factor, but power capability at what frequency always has to come first.
In this case I don't think there's all that much power involved, so a simple crossover could just be the ticket, since highs ( nor mids ) are not going to be used at an inch of their life at any time.
Crossover at 2,5kHz is pretty high too, so highly unlikely you will need a steep highpass for the highs and can get away with the simplest form of crossover. Basically a coil in series with the mids and a capacitor in series with the highs if you don't count the attenuation for the highs. That attenuation is going to take one or two resistors.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2020 at 9:27am
Perfect all makes sense thanks again Peter! 😀👍🏼 

Oh okay cool i thought each speaker needed its own chamber. Seeing as it doesnt i will leave the centre panel out and just reduce the depth slightly to make up the difference. It will make it easier to line the insides then too.

And yes i was thinking of lining the internal walls with this 30mm 'egg box style' foam which i have seen others use. I do not need to account for this displacement when calculating internal box volume though do I? 




Edited by Jack1991 - 18 April 2020 at 9:49am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2020 at 9:46am
Personally I'd leave the centre panel intact, as it being there provides two benefits…
1.    It adds structural stiffness to the enclosure; this helps shift panel flex/resonance up where it’s less disruptive.
2.    If the centre panel is not fitted or has holes within it and you have a driver fail open circuit the tuning of the system shifts dramatically, this can result in the driver becoming unloaded  allowing the driver to reach or exceed ”x-damage” resulting in two dead drivers. However if the panel is fitted you effectively have two separate cabinets and so the failure of a driver doesn’t result in the remaining driver becoming unloaded and subsequently failing.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 18 April 2020 at 10:41am
Cool okay yeh that makes sense too. Thanks 

How about the egg box lining displacement? Or do I not need to account for that as its like a open cell, rather than solid mass?
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