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Pro 4 + seven midhorn and tweeter [message #50982] Thu, 19 April 2007 21:00 Go to next message
beto1 is currently offline  beto1
Messages: 36
Registered: May 2009
Baron
Hi,
has some of you a picture of an hybrid Pro 4 + seven midhorn and tweeter?
Has this arrangement the tweeter in the bass bin or will better in the seven style?(not necerarelly with wooden horn at first, I guess)
Best regards and thanks in advantage,
Beto

Re: Pro 4 + seven midhorn and tweeter [message #50997 is a reply to message #50982] Mon, 23 April 2007 15:18 Go to previous messageGo to next message
Paul C. is currently offline  Paul C.
Messages: 218
Registered: May 2009
Master
Hi, Beto... I am presently building 3 pair of Pi speakers.

(1) I am building a pair of 4pi Theatres for my own use.

(b) I am building a pair of 4pi Theatres for my older son for his library/office/listening room,

(iii) and building the 7pi-18's for his living room.

Presently he does not have two adjacent corners to use the 7pi corner horns as designed. What Wayne suggested to me was to build bass bins identical to the 4pi Theatre cabinets, same ports, but simply put the Eminence Magnum HO 18's in these cabs instead of the Theatre's Delta 15's.

Presently I am in the process of cutting wood for three pair of cabinets 36" H x 24" W x 18" D. I will also build the proper 7pi-18 bass corner bins for my son to later simply remove the woofers and crossover from the 4pi bins and put into the corner horn bins.


Re: Pro 4 + seven midhorn and tweeter [message #51003 is a reply to message #50997] Mon, 23 April 2007 16:28 Go to previous messageGo to next message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron
Hi Paul:

What kind of wood are you using for all those speakers and where did you get it? I've been pricing baltic birch and getting prices of over $200 for A/A and around $80 for BB/BB in 4x8 sheets (looking in the San Jose area).

Thanks,
tim

Re: Pro 4 + seven midhorn and tweeter [message #51004 is a reply to message #51003] Mon, 23 April 2007 16:57 Go to previous messageGo to next message
Paul C. is currently offline  Paul C.
Messages: 218
Registered: May 2009
Master
11-ply birch veneer cabinet grade ply, I pay about $48/sheet.

Re: Pro 4 + seven midhorn and tweeter [message #51005 is a reply to message #51004] Mon, 23 April 2007 17:07 Go to previous messageGo to next message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron
Thanks - is it void-free? Wayne has been counselling me to be careful about buzzing caused by debris trapped inside the voids in the ply I got from Home Despot.

tim


Re: Pro 4 + seven midhorn and tweeter [message #51007 is a reply to message #50997] Mon, 23 April 2007 18:50 Go to previous messageGo to next message
beto1 is currently offline  beto1
Messages: 36
Registered: May 2009
Baron
Hi Paul,
thanks for answer.
I am returning to this proyect so most of the conclusions are on the forum. In the meantime I have done some other DIY proyects and upgrades.
I believe that I wil use JBL 2226H instead of the 18" JBL, but I like to use a midhorn. I guess I will obtain the most of mid fq and bass extension this way. Since I do not have corners to place properly the pro seven Pi, I have take Wayne advise to use the Pro 4 formula, but with 3 drivers. I have a tube SET amp and one of its wonderful characteristic is the gloious mids. So, I supose that I have to build the seven Pi mid enclosure and just add to the top of the 15" JBL and Eminence tweeter, both in the same enclosure.
On those days I have watch some render or picture with the tweeter horn outside the bass bin, so that's why I'm wondering wich way is the better solution, but I can't find it now.
Also, dis you know how much low extension I can get if I use the 18" in this configuration (bass+ tweeter and the mid horn)?
Do you beleive that baltic birch was better sounding material than MDF? Here I just can get marine or normal pine plywood (plenty of voids) , not baltic birch, so I will use MDF.
Best regards,
Beto
p.s. wich technique are using to cut and stick each panel?

Re: Pro 4 + seven midhorn and tweeter [message #51009 is a reply to message #51005] Mon, 23 April 2007 19:52 Go to previous messageGo to next message
Paul C. is currently offline  Paul C.
Messages: 218
Registered: May 2009
Master
As far as I can tell, yes.

Re: Pro 4 + seven midhorn and tweeter [message #51010 is a reply to message #51007] Mon, 23 April 2007 19:59 Go to previous messageGo to next message
Paul C. is currently offline  Paul C.
Messages: 218
Registered: May 2009
Master
Ply is lighter and stronger than MDF. With very large and heavy drivers MDF does not hold up well. I just find ply to be the better material. For you, MDF is probably the better choice.

I have a plywood cutting jig I made that works well. Click the attached link. You will have to click on each image icon to view the photos if you are not registered at that site.

I use aliphatic wood glue with bats and screws, screwed from the inside so they don't show. I cover the ply edges with "birch tape". Then sand, stain, and apply several coats of hand rubbed tung oil.



Re: Pro 4 + seven midhorn and tweeter [message #51014 is a reply to message #51010] Tue, 24 April 2007 09:53 Go to previous messageGo to next message
beto1 is currently offline  beto1
Messages: 36
Registered: May 2009
Baron
Hi Paul,
thats on the mechanical side, buts what about the sonic properties?
Well, whatever to be the answer, I can-t get baltic birch plywood here. Maybe I can use as a front panel, to get a strong hold for heavy drivers, a pine board with finger joint technic, to get a better material for mechanical issues.(or maybe some other wood)
regards,
Beto

Re: Pro 4 + seven midhorn and tweeter [message #51015 is a reply to message #51014] Tue, 24 April 2007 10:39 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18677
Registered: January 2001
Illuminati (33rd Degree)

The main thing here is we don't want voids. Actually, it isn't the void that concerns me so much as the debris that can be contained in the void. That will cause buzzing. Separated plys can buzz too. Those are the things we are trying to avoid.

If the cabinet you are building is labor intensive or has a fine wood finish, then it would probably be a costly disappointment if a buzz developed and you had to scrap the box. Buzzes can develop years later, when plys separate or debris breaks loose inside a void. Sometimes, if a buzz develops, a small hole can be drilled in the cabinet interior into the section of the wood where the void or ply separation is. You can sometimes inject glue into the hole and repair the damage, fill the void or reattach the plys. But it's probably better to reduce the risk of failure, starting with a high-quality wood to begin with.


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