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3 Way Build - DIY

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3 Way Build - DIY

Postby bra10n » 13 Mar 2018 13:29

3 Way, Vented Box

Hi all,

Like others on here, I recently looked at several reputable 3 Way speaker plans on the web but have decided to choose my own drivers and now I’m getting close to finalising a plan to build a 3 way speaker using the following drivers;

Tweeter - ScanSpeak Revelator 1” Ring Dome R2904/700000
Mid Range - Dayton Audio 2” Dome Midrange RS52AN
Woofer - Dayton Audio Esoteric 7” ES180TiA

Enclosure is 28L or < 1 cu ft with Fb tuned to 32Hz, single port and rear facing. Even though the tweeter and mid chosen are sealed units I still want to isolate them from the main enclosure so a small dedicated chamber of their own it is. While this is not a large speaker they will resemble a small floorstanding tower when completed.

I’m using a local species, Acacia, which I can buy in panels in a jointed lamella configuration. This should see a considerable increase in overall panel stiffness when compared to similar type wide boards.

I plan to use these with an active crossover and a multi-channel amp (Class D) with one dedicated channel per driver. For this to be successful I believe I need only get the driver mountings, box size and construction right. Baffle step I can address with the DSP but I’ll round-over the edges for good measure anyway. Drivers will be centre aligned.

I look forward to sharing my progress,

cheers
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Re: 3 Way Build - DIY

Postby rewfew » 13 Mar 2018 18:45



Yes, that's what it takes to diy your own speaker design. I've never had the kahunas to attempt such an undertaking. Just followed plans. Good luck and send many pictures. The acasia wood should look beautiful.
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Re: 3 Way Build - DIY

Postby wolfie62 » 13 Mar 2018 22:08

You should have good success with this since you don't have to mess with passive crossovers. Just adjust your amp sensitivity to your drivers. Once you get your box alignment tested, drivers mounted, you should be in speaker Nirvana!!
Often....invention is the mother of necessity.
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Re: 3 Way Build - DIY

Postby bra10n » 14 Mar 2018 04:41

Thanks for the replies.

I have one concern and that is the voids left at the base of each tower. Commonsense tells me if the boxes are quiet then there's little chance of hearing anything from the spaces. Instinct is to leave them open at the bottom with perhaps a double layer thickness for the bottom of the woofer enclosure?

Thoughts...

cheers
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Re: 3 Way Build - DIY

Postby wolfie62 » 14 Mar 2018 16:41

Not sure what you mean. Box not sealed at the bottom? Pics or sketch?
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Re: 3 Way Build - DIY

Postby bra10n » 15 Mar 2018 01:28

Apologies for not making this clearer.

The bottom section of the tower is simply an integrated stand (for cosmetic reasons). Hence the base of the speaker enclosure volume itself sits approximately 200 mm (8"0) off the ground. Hope that's clearer...
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Re: 3 Way Build - DIY

Postby bra10n » 24 Mar 2018 10:25

Made a start today cutting panels and got to work with the router on only a couple of panels. Will likely finish up machining the remaining pieces by mid week. Will post up some pics then.
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Re: 3 Way Build - DIY

Postby bra10n » 27 Mar 2018 06:29

Not a lot of time today but got this done.
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Re: 3 Way Build - DIY

Postby bra10n » 30 Mar 2018 12:27

Now with the carcass done I can get onto the fun bits
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Re: 3 Way Build - DIY

Postby wolfie62 » 30 Mar 2018 23:15

Western or red cedar? That’s a very soft wood! Are you going to line with internal MDF panels for strength and to kill resonances and prevent splitting?
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Re: 3 Way Build - DIY

Postby bra10n » 31 Mar 2018 00:46

Hi Wolfie,

This is neither Western or Red Cedar but Acacia. Regarding it's strength notice that each panel is constructed from slip-jointed lamellas as can be seen on the front panel in the above pic. No need for an internal lining for strength (MDF has little strength really) or ply for that matter. Corners are 45 deg joints and are solid. The rebates you see are for the vertical dividers/bracing between the sides and the baffle, which is glued and screwed. The baffle contacts the front edges of the sides but is in a sense 'floating' at the front face. The rear edges of the baffle are rebated and sit between battens which have also been rebated into the sides. So theoretically all vertical edges are indeed strengthened but this is just a by-product of construction. What's not seen is the vertical brace which will be used to provide the woofer a solid mounting and will tie the top and bottom panels.

Here's a pic of the rear of the woofer support...
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Re: 3 Way Build - DIY

Postby wolfie62 » 31 Mar 2018 01:25

Properly designed and constructed, MDF has great strength and is very largely inert, stable, and predictable in all directions from changes in humidity and temperature. It has no voids. By the very fact of rings, real wood has great variation in strength, growth from humidity and temperature changes.

On my iPhone, your wood looks just like cedar!
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Re: 3 Way Build - DIY

Postby bra10n » 31 Mar 2018 05:12

wolfie62 wrote:...By the very fact of rings, real wood has great variation in strength, growth from humidity and temperature changes.


Wolfie please remember that this panel is not a conventional wide timber board. All you say is true otherwise regarding strength and natural variation. To give you some perspective, I counted a side panel to have 30 lamellas (7 strips wide). We can agree to disagree though on the merits of MDF... :shock:

PS I know things look better on an iPhone :mrgreen:
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Re: 3 Way Build - DIY

Postby wolfie62 » 31 Mar 2018 13:53

Ok. I’m with you now! Laminated thin strips of acacia to build the solid panels!

I take back my reservations! That should be very strong, inert, and stable!

But I swear, your panels look just like patch-worked panels of red cedar from my phone!

Sorry for the digression, carry on!!
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Re: 3 Way Build - DIY

Postby bra10n » 31 Mar 2018 21:59

All good Wolfie :D

Leads nicely onto a question re cabinet damping...

I had every intention on lining the woofer enclosure with a heavier vinyl layer (1.74g/cm3) compared to the panel (0.5g/cm3) between the front and rear battens and the rear panel, top and bottom. This would be like a strip 60% of the width of each panel glued down the middle but I'm now reconsidering this mass loading and whether this will be of any benefit or in fact detrimental. There will be a degree of CLD damping benefit due to the flexible glue layer between the vinyl and panel but the main thing is I feel this will lead to a lowering of the cabinet's resonant freq. Any thoughts?

Keep in mind the benefit of any CLD effect will IMO be very minimal; CLD is more than laminating different materials together. If anything I want to try and push these frequencies upward.

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