Home » Sponsored » Pi Speakers » 3 PI build (Building a pair of 3 Pi speakers)
Re: 3 PI build [message #79303 is a reply to message #79302] Wed, 05 February 2014 10:18 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
OK, next up. Finishing the boxes. I started with a coat of Zinzers oil based "Cover Stain" primer.
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I had planned to paint the plinth at the bottom of the baffle and the tops with a Black Lacquer. After experimenting with this on the tops I abandoned it for now. It did not go well and the odour was strong and persistent. I still may lacquer the tops. I painted them with the same finish as the rest of the box. I screwed them on without gluing them so I can change them out if I decide on a different finish. Perhaps in the summer when I can work outside i will try again.

I then applied 2 coats of Rustoleum Painters Touch flat black latex. I used a foam roller. Next I applied 2 coats of Varathane Diamond Coat satin with a good quality bristle brush. If you try to roll this stuff you get runs and air bubbles.


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Re: 3 PI build [message #79304 is a reply to message #78971] Wed, 05 February 2014 10:43 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
I next ran the wiring from the crossover up through a hole in the base. I sealed the hole with electricians putty on the bottom and silicone on the top. I used batt insulation on the backs, bottom and side nearest the port. I also placed a batt on the window brace between the horn and woofer. I covered the batts in the woofer section with a layer of quilt batting to prevent any fibres from getting out of the box. I remember demoing some speakers one time and the salesman decided to show off and play a track of some thunder at an extreme level. A big chunk of fibreglass blew out the port. Needless to say I didn't buy anything from them and have always wondered if any fibres are being pushed from a fibreglass insulated box in routine operation.
Note! The camera somehow got switched to image stabilization mode which resulted in low quality pictures here.

Batts in place. I cut away some of the insulation for the horn/driver to fit.
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Quilt batting added.
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I also installed some "affordable" spikes. Carriage bolts, nuts and washers. In this case the size is 3/8". If you are doing something like this make sure you allow clearance for bolts to extend up into the enclosure. I set up the enclosures for a upward tilt of about 3/4" from back to front. This should get the sound up high enough to not need any stands.

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So now we are ready to add the drivers.


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Re: 3 PI build [message #79305 is a reply to message #79304] Wed, 05 February 2014 11:10 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
For ports I am using some that I had around. They are flared at the front and tapered slightly in diameter. I had 4 of them. 2 used and 2 new. In order to get the correct box tuning I decided to experiment with the used set of ports. I used an average diameter for the port. This figure was about 10% larger than the stock 2.5". Since the port length formula has radius squared as a variable I squared 1.1 and came up with a figure of 1.2 x the stock length of 2.5" or 3". I cut the used ports to 3" and installed them as a starting point. I can then measure the tuning frequency and work from that figure to find a port length for the permanent installation.
Driver install was pretty straight forward. The BandC 250 came with hardware to install them on the horn. It didn't take long to get things finished.

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I decided to try the corners as a location for these. The room is 19' x 12.5'. I put them in the corners of the long wall angled at 45 degrees which seemed incredibly far apart. I am not using the subs at this point.
So... how do they sound. Different from what I was used to. It's early to make any judgements but one thing is obvious. Dynamics are stellar. I played Jonny Lang - I Am from the album Wonder This World. This track is very dynamic and I turned it up and was surprised to hear it play much cleaner than I'd heard it in the past. The vocals stayed clean where previously they would get nasty when even approaching these levels. The overall tonality is good with no obvious problems. Bass is tight and a bit thin down low, but the woofer is just breaking in and I am used to 2 subs being in the mix. I'll post more later on sound. It's very promising at his point.


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Re: 3 PI build [message #79321 is a reply to message #78971] Thu, 06 February 2014 10:59 Go to previous messageGo to next message
HPower is currently offline  HPower
Messages: 16
Registered: October 2013
Location: Newmarket, ON Canada
Chancellor
Hey Brian,

Great job on your 3PIs, looking good!!!

I like your use of the odds and sods with the mounting of your Xover boards and carriage bolt feet, but any Canadian worth his salt should have some Duck Tape in the mix. Razz

Can you say Red Green. Very Happy

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I still have not gotten to my 4PI build, our kitchen reno has decided to take up all my hobby time.
Hopefully in a month or so I can get to it.

Again, congrats on a nice job,
Tom


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The 3 most feared words in racing... "Powered by Honda"
Re: 3 PI build [message #79335 is a reply to message #79321] Fri, 07 February 2014 05:28 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
It's good to hear from you Tom. I've been wondering how your 4 build was coming along. I'm pretty happy with the sound of these but I don't know about the corner positioning. It works quite well for some music. However, for anything where an instrument is recorded hard to one side, such as in older jazz recordings, it puts those instruments way out there in the corners of the room. It's a bit odd and not what I'm used to. After logging a few hours on them I am most impressed with the dynamic range and the purity of the treble produced by the DE250/H290C combination. I have never had such clean HF reproduction. Never harsh or "bright" sounding.

P.S. I put the duct tape on the inside for better WAF!
Re: 3 PI build [message #79338 is a reply to message #79335] Fri, 07 February 2014 07:49 Go to previous messageGo to next message
HPower is currently offline  HPower
Messages: 16
Registered: October 2013
Location: Newmarket, ON Canada
Chancellor
" P.S. I put the duct tape on the inside for better WAF! "

Good call!!!

I have my Cornscalas in a 20' x 15' room, speakers on long way about 3' from side wall and 2' into room which puts the front-center of the speaker about 12' a part and main seating position 11' from each speaker.
This gives me a nice wide sound stage with no noticeable hole in the middle.

Even when I had my previous KHorns in the 20' corners I was getting a similar good soundstage.
I would suggest moving your 3PIs closer together, yes you will probably lose some bass response with them out of the corner, but you should improve your side to side imaging.
I know PWK suggested using a center channel in mono to help imaging with wide corner placements but I never have tried that technique.

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This shot shows how my CSs are place in relationship to my 20' corners... about the same for the left speaker that is not completely in pic.
Hopefully trying some different positioning will get you where you want to be.

Yes, horn speaker do excel in the dynamics.
I love the way hons sound, a real "live sound"!

I am sure your 3PIs and my 4PIs (once I get them built) will be equally enjoyable in this regard.
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The 3 most feared words in racing... "Powered by Honda"
Re: 3 PI build [message #79340 is a reply to message #78971] Fri, 07 February 2014 08:17 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
Tom, your system and room look great! I see you have some interesting items damping the tops of your Cornscalas! I've never experienced horn loaded tweeters in my system. They are not harsh or strident at all, just the opposite in fact. I had the subs on last night and have got them dialed in pretty close by ear. I'm going to get out my DEQ2496 and measurement mic and see what's up in the bass. I want to give the woofers a little more break in time. I re tightened the mounting bolts last night and they had loosened off a bit. Gasket compression I guess. I need to measure the port tuning frequency so I can determine the proper port length for the permanent install. I hope to get the grill frames done on Saturday.


Re: 3 PI build [message #79411 is a reply to message #78971] Wed, 12 February 2014 05:21 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
Update:
I've been experimenting with placement on the long wall. I can't seem to get the sound I want in that configuration. This is nothing new. I've never been happy with any setup with the speakers along that wall. I'll try putting them in the corners of the short wall.
The grill frames are biuilt, painted and the magnets installed. The fabric is going on tonight if I have time.
Re: 3 PI build [message #79465 is a reply to message #79411] Sun, 16 February 2014 15:03 Go to previous messageGo to next message
BFP is currently offline  BFP
Messages: 48
Registered: May 2009
Baron
Got the grills done and have continued to experiment with placement. The grills are simply a frame of 1/2" MDF 2" wide on the top and sides and 3" wide on the bottom. They are simply butt joint glued together and painted flat black. The fabric and magnets/ friction discs were added and they do the job just fine.


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I have abandoned trying to get decent sound on the long wall. Even with the speakers moved in to 11ft. apart I still could not get a decent centre image unless I sat right in the middle. Moving a foot to the side would pull the sound to the speaker. I also had my chair against the wall which never seems to work well IME.
I put them in the corners firing up the long dimension of the room where I could sit further back. This seemed to create the stable image that they are supposed to produce. I placed my subs in the opposite corners behind the listening seat. This provides excellent deep bass and integration with the PI 3.
I got a chance to check the port tuning and it was lower than spec at 26.5 hz. I cut the ports down to just under 2" and got a tuning of 29.8hz which is right where it should be. I do wonder if I have too much insulation in the boxes. I used rock wool batts that are 3" thick and are designed for acoustic duty. At 2.5lb/cu.ft. they are slightly denser than regular fibreglass or rock wool which I believe are around 2lb.
I may have to talk to Wayne about measuring the impedance values to determine if I have too much insulation in the box.
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Re: 3 PI build [message #79478 is a reply to message #79465] Mon, 17 February 2014 16:52 Go to previous messageGo to previous message
Wayne Parham is currently online  Wayne Parham
Messages: 18706
Registered: January 2001
Illuminati (33rd Degree)

There is a write-up about measuring T/S parameters in the link below:
Of course, now days, with some of the automated measurement devices, you can literally get these specs with just a few clicks of the mouse and a test box or some weights (like coins taped on the cone). But the process and the formula that show what's going on "under the hood" are in that post, which may prove interesting.

Here's another post with useful T/S formula:
And two posts that show formula for Helmholtz (bass-reflex box) resonance, and how it is manifested in the impedance curve:

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