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Modify Peavie 18" Pro-Audio Reflex case to 34hz
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ViihdeJukat View Drop Down
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Joined: 13 November 2023
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    Posted: 13 November 2023 at 11:34am
I have 90s peavie 18" subwoofer encolosures with reflex channel. Images belov.

Installing 1000w rms 8ohm speakers: https://bishop.co.uk/products/18-subwoofer-driver-cast-alloy-1000w-rms-with-faston-terminals-woofer-bdp18-4-ohm - https://bishopsound.co.uk/products/18-subwoofer-driver-cast-alloy-1000w-rms-with-faston-terminals-woofer-bdp18-4-ohm

Key Features

  • Nominal Voice Coil Diameter: 4" / 102mm
  • Usable Frequency Range: -6dB 35 Hz - 1.0 kHz
  • Die-Cast Aluminium Basket
  • Magnet Weight: 125 OZ
  • 8 Ohm Impedance
  • Resonance Frequency Fs 34.8 Hz
    Mechanical Q Factor Qms 11.48
    Electrical Q Factor Qes 0.57
    Total Q Factor Qts 0.543

Material: 20mm or 2cm
The box is 65*75*63cm
The Sub inside diameters are 52*60*55cm + surround behind reflex channel that is 11*38cm.
The reflex is 50*9*24cm inside diameter.
If L channel added the subfooer inside dia changes by arround 13cm less space on behind and that surraund behind current reflex is used for the channel.

I have calculated that this channel is way too short for 34hz operation, and it is arround 60-70cm long channel that makes that. I just need some advice am I in correct path here? Should I also put 45 degree small strips on bottom and top corner to lesser airspace on corners? Also the bottom bord should it have 45 degree cut behind to make air move diagonally rather than 90 degreen turn?

Basically I need L channel there I can remove the current channel board and add my own channel board there. Nice that peavie made it so that it can be changed. So in order to do 70cm long I need about 44cm bottom which makes 48cm channel and then about 20cm board up to make that 68cm L channel inside. How ever I have seen in some cases they are making channel all the way to top board so that there would be 9cm channel also going down. What do you guys suggest here? Adding top 120hz resonator would mean on about 5cm path to front of the speaker about 10cm panel down and 5cm hole to front of the speaker on topside. That would make this bandpass case.

I was also suprised that they have used superfoam inside, all cases I have seen dont use at all foam inside. Is this really needed or does it have some benfit there?





Edited by ViihdeJukat - 14 November 2023 at 8:28am
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ViihdeJukat View Drop Down
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Points: 8 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ViihdeJukat Quote  Post ReplyReply Direct Link To This Post Posted: 14 November 2023 at 8:30am
Interesting, another webpage said that the channel need to be 60-70cm long. But winsdi says only 40 cm so that extending 15cm current is sufficient enough to switch focal point from 100hz region to 50-70hz and -3db at 34hz.

Edit, I got way off now. So we cant edit driver caractheristics but case resonates lower subs more high sounds. So I can model box all the way 20hz so that speaker essentially gets a bit louder on low notes?

Is that correct then I need to extend the channel going all the way to top board to give flatter response down to 20hz?


Edited by ViihdeJukat - 14 November 2023 at 9:40am
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Elliot Thompson View Drop Down
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Points: 5111 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 14 November 2023 at 1:27pm
The Logical thing to do is install the new speaker in the Peavey enclosure, listen to it and, come to a conclusion if it plays low enough for your requirements. Once you start butchering the enclosure, there is no turning back if you made a mistake. The foam is there to dampen the standing waves occurring based on how the original driver (Peavey) is reacting in the box at a particular frequency.

Do things one step at a time before you attempt to modify the enclosure.

Best Regards, 

 
Elliot Thompson
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ViihdeJukat View Drop Down
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Points: 8 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ViihdeJukat Quote  Post ReplyReply Direct Link To This Post Posted: 14 November 2023 at 9:39pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

The Logical thing to do is install the new speaker in the Peavey enclosure, listen to it and, come to a conclusion if it plays low enough for your requirements.


I have upper box already 1000w cone, and it is a bit highpass sound, I'd like to go lower to feel the thump. Basically I will try first doing maxx to 9cm from backwall  board. I can cut it smaller later if it's not good. Basically will use some silicone and screws to test first then add proper cluing later if all good.


Edited by ViihdeJukat - 14 November 2023 at 9:46pm
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