8inch coaxial hifi speaker build
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Category: Plans
Forum Name: New Projects Forum
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URL: https://forum.speakerplans.com/forum_posts.asp?TID=69822
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Topic: 8inch coaxial hifi speaker build
Posted By: biotec
Subject: 8inch coaxial hifi speaker build
Date Posted: 13 August 2012 at 10:50pm
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Here's my latest project, Two cabinets to house a single 8inch volt coaxial speaker each FR220.1. These will be going into my motorhome, on brackets (which I've yet to make), and will be able to swivel 180degrees so that they can point into the cab when I'm driving and into the back when I'm parked. The nuts for the brackets are mounted at the centre of the rear curve, and so I can mount the speakers as close to the the wall as possible. I got the drivers a year or so ago from Punchy but never got round to doing anything with them until now. The drivers sim best in small enclosures so these are a 9.5 litre net internal volume. I will tune them to about 65hz. The cabs will probably sound acceptable without a sub, but I've got an efficient 300w beyma 15" which I can fit into a void space so that will be used to add a bit of low end. I had a load of 6.5mm plywood left over from another job so these boxes are built from that. All panels are double layered (13mm) except the baffle which is 3 layers. To do the curve I kerfed the ply at 8mm centres, leaving just over one laminate. I didn't realise the importance of bending along the grain, and so on the first cabinet, the outer curved piece was cut the wrong way. Consequently the panel cracked along several of the kerfs and so I had to use lots of filler to get it smooth. I had planned on bonding the curved sections with thickened epoxy resin but after experimenting with PVA I realised it would be more than strong enough. Still got to paint and fit the hardware but much of the hard work is done. I've put about 2 days into them so far. The large recess on the top and bottom is for a 20mm threaded top hat for the brackets. The two smaller holes on the top are for two 30mm ports (which will be about 90mm long), and the hole on the bottom is for the speakon.      ------------- me so horny, me love you long throw. |
Replies:
Posted By: dlyxover
Date Posted: 13 August 2012 at 11:05pm
great build  ------------- Lignum_ww@icloud.com GNKaudio@icloud.com |
Posted By: ermita
Date Posted: 13 August 2012 at 11:09pm
 nice work . |
Posted By: mk2_ginger_biscuit69
Date Posted: 13 August 2012 at 11:19pm
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beautiful!
------------- ''Remember that the object of a subwoofer is to enhance the output of your main speakers, not overpower it'' ''Dubstep - an elongated electronic fart'' |
Posted By: RUS
Date Posted: 13 August 2012 at 11:39pm
 [/QUOTE] thats where my sewing machine lid went  sorry mate there very nice im sure them two will sound prety loud in the motorhome. |
Posted By: biotec
Date Posted: 14 August 2012 at 12:29pm
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thanks all, here's a closeup of the kerfs, you call also see the filler where I set the triming bit to low in the router and the bearing dropped into the port hole.  I would say that this is pretty close to the minimum bending radius you can achive using this technique. The radius is 120mm and you might be able to get it 10-20mm smaller. You could possibly go further if you cut the kerfs into the last laminate, but you'd be removing so much material that unless you filled the slots with resin you'd be weakening the wood considerably. I had a load of 6.5mm birch to use up, so this tehcnique worked well for me, but given the choice I would rather layer up 3 or 4mm sheets. These cabinets are small (266x266x273) and I still had to cut 100 kerfs per box, for a bass horn or larger mid-top this would be a slow painfull process. Incidently I was pretty shocked out how inflexible the 6.5mm birch py was without kerfing it. Minimum bending radius was in the order of several feet. ------------- me so horny, me love you long throw. |
Posted By: darkmatter
Date Posted: 14 August 2012 at 12:51pm
| Bootiful! |
Posted By: Vert
Date Posted: 14 August 2012 at 7:15pm
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Like that mate ------------- Box builder, pm for quote |
Posted By: boycey
Date Posted: 15 August 2012 at 8:24pm
very cute, i got a pair of those off punchy and built some reflex trapezoids tuned to 50hz (at the recommendation of markie) for them. absolutely love them. these should be the dogs, look forward to seeing the inevitable follow up sub project  ------------- the only thing more dangerous than a person who doesn't give a f**k is a person who gives a sh*t. |
Posted By: biotec
Date Posted: 24 August 2012 at 2:37pm
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I've got both painted now but have only had time to load the driver and fit the hardware to one of them. I'll probably load the other and build the wall brackets this weekend if there's a break in the weather. I've got some 40x8 flat bar to make the brackets with but I'm not sure whether it'll be rigid enough in the way I plan to mount it. If necessary I'll grab some 40x12 to stiffen it up. I did one coat of primer, 3 coats of undercoat, and 3 coats of satin. The finish is pretty smart and it'll fit in nicely with the white interior I'm putting in my truck.    I had a chance to listen to the one I loaded yesterday. I haven't installed the headunit or amps in the truck yet so I tested it off a Crown DC300 in my house. First impressions are great, the sound is awesome and f*ck me does it go loud. I may have tuned it a little high as it doesn't go as low as I expected, at a guess I'd say it starts rolling off about 70hz, but I'll play around with the ports this weekend. Playing it alongside one of my bookshelf hifi speakers, it sounds clearer, without the boomy bass and missing midrange that a lot of small hifi speakers have. It doesn't go as low but the hifi speaker was making death noises when the coaxial still had 12db of gain! I threw most of one side of the DC300 into it and I got scared before it showed any signs of distress. Two in the truck will be able to go louder than I'll ever need for sure. Here's a brief video to give you an idea of the sound. The camera mic was distorting when I got too close. Appologies for the wonky view and explicit music! I ahdn;t realised the track was quite so offensive untill I listened back! http://s51.photobucket.com/albums/f374/nickbiotec/Jim%20the%20Truck/Coaxial%20Hifi%20speakers/?action=view¤t=VIDEO0011.mp4" rel="nofollow">  ------------- me so horny, me love you long throw. |
Posted By: SamV
Date Posted: 24 August 2012 at 7:14pm
| Great job! Pretty little cabs. |
Posted By: jbl_man
Date Posted: 25 August 2012 at 11:36am
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Love the curved ply Nick,really lovely job.
------------- Be seeing you. |
Posted By: kevin tyler
Date Posted: 25 August 2012 at 11:40am
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wow! good job
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Posted By: Edd Jordan
Date Posted: 03 September 2012 at 12:19am
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really like the look of those cabs have been thinking about doing a curve on a pa cab for a while was the how hard was it todo the curve? ------------- I do a sideline in ply wood wheels. |
Posted By: biotec
Date Posted: 19 April 2013 at 4:36pm
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readded images ------------- me so horny, me love you long throw. |
Posted By: jerronimo
Date Posted: 21 April 2013 at 4:53pm
| Aircraft plywood is specifically made for bending. |
Posted By: biotec
Date Posted: 22 April 2013 at 3:26pm
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I didn't have any aircraft plywood to hand! You can buy flexible birch, which I guess is just layered up with the grain all going in one direction. Aircraft plywood is probably lighter, maybe spruce, so not as good accoustically. ------------- me so horny, me love you long throw. |