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Wayne Parham's Pi 4 Build Thread

post #1 of 126
Thread Starter 
I decided to build a pair of Wayne Parham's Pi 4 speakers that I will eventually use in my home theater. In the meantime, I will be using them for mostly music listening in my living room.

For those who are not familiar with the design, it is a 2-way speaker that uses 15 inch woofers and compression drivers mated to horns. Wayne offers several grades of components depending upon the amount you want to spend. The speakers can be purchased as complete units or in parts for us DIY'ers. Wayne has been gracious enough to share his design plans to anyone who asks. I decided to go the more expensive route by using JBL 2226H woofers, B&C DE250 compression drivers, and quality crossover components.

I wanted more bass extension than the original design calls for so I decided to increase the cabinet size by approximately 1 cubic foot. This was achieved by increasing the height 7 inches. Due to the larger cabinet size, I am using a double-thick front baffle (1.5 inches vs. 0.75 of an inch per plan). This extra thickness will be added to the exterior of the cabinet. The overall dimensions are: 33.5 tall x 18.5 wide x 15 deep. I am also changing the number of ports, their location and dimensions. Further, I am going to recess the drivers.

One area that concerns me is the midrange frequencies leaking out of the ports and blurring the image. There does not seem to be much information on this phenomenon. I could have the ports exit at the rear of the cabinet which would virtually eliminate any problems due to the lag in time before it reaches the listener but I prefer to have them exit in the front. In order to mitigate any issues I plan on using extensive polyfill to absorb some of the back wave and a semi-solid window brace between the woofer and ports (I will post a picture of this in a few days).

Attached are my Sketchup model of how I envision the cabinet to look and a few simulations of the JBL 2226 (per plans vs. my larger cabinet).




post #2 of 126
Thread Starter 

UPDATE 6/25/2012:

 

I finally got around to measuring the Pi4 that I built. I did both inside and outdoor measurements.

 

http://imageshack.us/photo/my-images/189/pi4insidevsoutsidemeasu.jpg/

pi4 inside vs outside measurements.jpg
 

 

 

For anyone who plans on building these, additional information can be found at Audio Round Table (http://audioroundtable.com/forum/index.php?t=msg&th=12291&prevloaded=1&&start=0) .


Edited by nichol1997 - 6/25/12 at 6:31pm
post #3 of 126
Awesome, will you be doing any measurements?
post #4 of 126
i'm looking forward to your build.

you could place the horn centered over the woofer. the offset is only to accomodate the square port on the original design.

the suggested placement for 4pis is against a wall or in a corner. that is going to give you a little more bass under about 120hz than winisd predicts, as you will in less than 2pi space which is what winisd shows. there is another build around here by myggpower who built mid-bass modules using the 2226h and then turned them into speakers by adding a top horn.
http://www.avsforum.com/avs-vb/showthread.php?t=1139819
post #5 of 126
Thread Starter 
Quote:
Originally Posted by penngray View Post

Awesome, will you be doing any measurements?

I wasn't planning on doing measurements but a friend of mine does have the equipment to take them. It probably won't be for a while if I do decide to do it.
post #6 of 126
I think your title should be Modified build.

Putting Wayne's name on your spin of his speaker is misleading.
post #7 of 126
Quote:
Originally Posted by t6902wf View Post

I think your title should be Modified build.

Putting Wayne's name on your spin on his speaker is misleading.

um what? By modifying the box volume you think alters the design enough that it's no longer a Pi?
post #8 of 126
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

i'm looking forward to your build.

you could place the horn centered over the woofer. the offset is only to accomodate the square port on the original design.

the suggested placement for 4pis is against a wall or in a corner. that is going to give you a little more bass under about 120hz than winisd predicts, as you will in less than 2pi space which is what winisd shows. there is another build around here by myggpower who built mid-bass modules using the 2226h and then turned them into speakers by adding a top horn.
http://www.avsforum.com/avs-vb/showthread.php?t=1139819

I could center the horn but the baffles are already cut and mostly routed (will post pics sometime this weekend). Not a big deal aesthetically speaking since I will be making grills for them.
post #9 of 126
Quote:
Originally Posted by zero the hero View Post

um what? By modifying the box volume you think alters the design enough that it's no longer a Pi?

Yes, box volume ports....

Is it Wayne's or modified.

No big thing just trying to limit the confusion of people like me who read fast and may miss some details.
post #10 of 126
those things are only going to change bass extension; that's usually flexible in a design provided the person altering knows how to design around T/S parameters.
however changing baffle width and driver placement starts to actually affect the design, so that part may be construed as unapproved mods
post #11 of 126
Thread Starter 
Some of the parts:







And some progress:









I forgot how labor intensive it is to do the baffles. It took about 12 hours in total to router cutouts and ports.
post #12 of 126
post #13 of 126
I dropped over to Nick's place to discuss this project as I've been thinking about building the Pi 4s for my theater. Here is a picture of his planned bracing set up and the builder himself.

post #14 of 126
Well that concludes something for me... Everyone does better bracing then me

Nice build so far
post #15 of 126
maybe penn...but the baffles on your latest project were really, really, nice.

i kind of wonder how much bracing is required for a pro-audio type two-way, as the structural demands on the enclosure are no where near as large as those on high excursion, kilowatt, high mms subs.

in the pic, it looks like another offset horn though ports are below. why not center the horn if porting below?
post #16 of 126
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

maybe penn...but the baffles on your latest project were really, really, nice.

i kind of wonder how much bracing is required for a pro-audio type two-way, as the structural demands on the enclosure are no where near as large as those on high excursion, kilowatt, high mms subs.

in the pic, it looks like another offset horn though ports are below. why not center the horn if porting below?

The amount of bracing that I am doing might be overkill but I wanted to make sure that I have no regrets with this build. The wood for the bracing was leftovers anyway.

I am building a pair of them and both of them will have offset horns. I will center the horn in the baffle when I build the center channel.
post #17 of 126
Looks good! I am having trouble deciding between the 4pi & the 3pi. This is probably going to assist my decision.
post #18 of 126
Quote:
Originally Posted by nichol1997 View Post

The amount of bracing that I am doing might be overkill but I wanted to make sure that I have no regrets with this build. The wood for the bracing was leftovers anyway.

I am building a pair of them and both of them will have offset horns. I will center the horn in the baffle when I build the center channel.

Your bracing is great. My point was just me facing the facts that all builds have more bracing them I do, I will have to build a nother speaker or two with more bracing and check for differences.

Your build is great!
post #19 of 126
"I am having trouble deciding between the 4pi & the 3pi."

4 pi's. a couple inches or a couple bucks are not worth it. if you are concerned about front cross sectional area, build the 4 pi's to have a 45 degree angle.
post #20 of 126
Watching this thread with interest!
post #21 of 126
Quote:
Originally Posted by LTD02 View Post

"I am having trouble deciding between the 4pi & the 3pi."

4 pi's. a couple inches or a couple bucks are not worth it. if you are concerned about front cross sectional area, build the 4 pi's to have a 45 degree angle.

I was kicking around the idea of the 3pi's in smaller, narrower sealed cabinets because they are crossing over to a pair of 18's anyway. They model great with the TD12s's in about a foot & 1/2 of space each. I have to make these look nice because they are going in the living room......
post #22 of 126
Quote:
Originally Posted by robseyes View Post

I was kicking around the idea of the 3pi's in smaller, narrower sealed cabinets because they are crossing over to a pair of 18's anyway. They model great with the TD12s's in about a foot & 1/2 of space each. I have to make these look nice because they are going in the living room......

What Zilch said:

Quote:
Originally Posted by Zilch View Post

I just don't see the value in using 15" woofers for HT builds having subwoofers, and there clearly are compromises associated with them which are not, in my view, outweighed merely by prospects of seeding as a Johnson Award contender....
post #23 of 126
Hey Zilchster. I've been watching your ewave thread with MUCH interest. Thanks for all of your hard work!
post #24 of 126
Quote:


Originally Posted by Zilch
I just don't see the value in using 15" woofers for HT builds having subwoofers, and there clearly are compromises associated with them which are not, in my view, outweighed merely by prospects of seeding as a Johnson Award contender....

Zilch there are great advantages to 15" woofers running up to 700Hz or so. I own those TD12S drivers and I have had the big towers with 8" woofers. Its just a simple mater of SPL and dynamics, I have that now when all those smaller drivers failed.

15" woofer does not automatically conclude they are only for lower frequencies. Many of the higher end custom HT rooms have those 12s and 15s in the main speakers because they simply outperform the smaller drivers.

I wonder what compromises exist with the JBL high end drivers or even AE speaker 15" woofers...which we run in your favorite designs up to 2KHz.
post #25 of 126
Quote:
Originally Posted by robseyes View Post

Hey Zilchster. I've been watching your ewave thread with MUCH interest. Thanks for all of your hard work!

The DIY speakers game has clearly changed, and I'm mostly pleased to be part of making that happen.

Quote:
Originally Posted by penngray View Post

I wonder what compromises exist with the JBL high end drivers or even AE speaker 15" woofers...which we run in your favorite designs up to 2KHz.

Patience, Grasshopper, you are on the path of many discoveries....
post #26 of 126
hey z., there are reasons for 15"s other than "johnson awards". first, there is distortion. larger woofers have less distortion because of less cone movement, ceteris paribus. second, the lower frequency matching of directivity gets the woofer out of the way before the region where we are most sensitive to frequency direction cues. third, cone profiles can matter. not sure what is going with this one, but both dr. g. and nick mckinney (designer of aespeakers td15m) indicate that the 15"s just plain sound better than the 12" versions, though the 12"s are a close second. fourth, 15"s have been accepted as the ideal bottom end of a two way since the 1930's...iconic. you know this. even today, jbl employs a 15" in the k2. well, i'm not going to argue because we can both point to many examples of successful implementations 12" or 15" and so we aren't going to get anywhere.

nichol, i recall reading on the parham forum about somebody who built 4pi's but thought the horn resonated and colored the sound. the solution employed was to wrap the back of the horn with clay or something like that. after doing so, the opinion changed to very positive. like i said, i forget who or where it was, or i'd post a link. just something you may wish to look into.
post #27 of 126
here is the info from some old notes of mine:

"My first impression yesterday was disappointment with a 'plasticky' coloration from the treble that spoiled the sound and I was filled with regret over abandoning the wood horns. I decided to try damping the H-290s even tho' there was limited success doing that to Altec 811s some years ago. And these horns aren't even 'cowbell' aluminum. I completely covered the outsides of the horns with M-D rope caulk, $4 bucks a package. It made a fantastic difference, completely eliminating the coloration. This is a mandatory tweak for anyone using the H-290 in whatever speaker."

http://www.pispeakers.com/catalog/pr...68beb6bbca7857
post #28 of 126
I got my DE250's in the mail yesterday. Was kind of surprised to not see some sort of screen like the D220i's have?
And had a "doh" moment when I realized they are bolt on, so I can't swap them onto my JBL econowaves to have a quick listen.

Wish I could start my pi4 build, but I'm still trying to bust out my bathroom remodel. Sanding the tape/mud today. Hope to start 2nd coat tomorrow.
post #29 of 126
Thread Starter 
Added more screws to the baffle:


Note the Kreg tool plug:


Bracing:


Back panel with recessed connection jacks:


Sanding sealer applied to interior surfaces:
post #30 of 126
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

here is the info from some old notes of mine:

"My first impression yesterday was disappointment with a 'plasticky' coloration from the treble that spoiled the sound and I was filled with regret over abandoning the wood horns. I decided to try damping the H-290s even tho' there was limited success doing that to Altec 811s some years ago. And these horns aren't even 'cowbell' aluminum. I completely covered the outsides of the horns with M-D rope caulk, $4 bucks a package. It made a fantastic difference, completely eliminating the coloration. This is a mandatory tweak for anyone using the H-290 in whatever speaker."

http://www.pispeakers.com/catalog/pr...68beb6bbca7857

LT,
Thanks for the heads up. I did a thorough search before starting this project and remember coming across this post in regards to adding the rope caulk to the backside of the horn to kill resonances. So last week I picked up 4 boxes of this stuff:

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