# 2 way using a 12" Designs



## 1Michael (Nov 2, 2006)

Does anyone have a link for a DIY 2way using a 12" bass driver and appropriate tweeter? Thanks.


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## fractile (Mar 15, 2009)

I don't know of specific plans, but could suggest looking into using a Tannoy co-axial 12". I recently upgraded to a pair of 10" Tannoys and have come to appreciate the understated neutrality (if that makes sense).

The 12 and 15"(?18) Tannoys are going for around $1000/ea on ebay, so it wouldn't be a budget project. And I don't know the availability of recone kits for these, like there is for the 10", or if they have rubber surrounds that maybe would not require it. 2¢


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## fractile (Mar 15, 2009)

I'd intended to include this link for a perspective on the whole concept: http://www.manleylabs.com/containerpages/ml10a99.html


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## 1Michael (Nov 2, 2006)

Those are going to be out of my price range, but I will keep looking!


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## fractile (Mar 15, 2009)

In case you're still studying this project, I discovered some relatively inexpensive coaxial drivers from a company called P.Audio. For 12" speakers, this would be the BM-12CXA or BM-12CX38. What caught my attention is that the pictures of these looked very similar to the Tannoy design, which I consider to be the closest to ideal for a dual concentric speaker, prior to the new Genelec design in the 8260A active monitor.

The two BM-10CXA's I ordered arrived today. Initial inspection shows some basic similarity and distinct differences to what I've seen of the Tannoy SGM-10 speakers in my Manleys. The paper cone has a polymer-coated cloth surround, instead of rubber, and is uniform thickness (thinness), compared with the pulpy back of the SGM-10,which I understand helps prevent cone-mode breakup. The P.A speaker cone probably has a polymer binder in the paper, to serve this purpose. The only technical info I've found so far is the spec sheet, and browsing through the replacement parts catalog and websites like commonsenseaudio.com .

The high-frequency horn has what I'd describe as a cylinder with an abrupt flared bell at the end, instead of the straight cone of the SGM-10. It has been described as cast aluminum (which I assume the SGM-10 is) and is about 1mm thick, compared with ~3mm. I'll have to see how these sound. 

My initial testing/application will be as a center surround speaker pair with open-baffle packages and simple capacitor cross-over. The high frequency driver goes down to 500Hz. From what I understand a cross-over between 500 and 850, compared to ~1k will help maintain coherence of vocals.

I'll have to get a grip on design of LC high-pass networks. Once I get a ballpark understanding I can probaly test with the box of high-voltage variable aluminum plate capacitors I picked up a while back.

I also got a deal on a pair described as NOS Fostex RP-60 (6") dual-concentric monitors, due to arrive maybe tomorrow. The RP-60 is listed as a consumer version of the professional RM-765. The picture of these did show a teakwood veneer cabinet and front adjustment knobs and a horn-loaded tweeter; not the dome tweeter I saw in pictures of what was called a RP-60. The configuration of the woofer and tweeter look like the third closest to ideal next to Tannoy and Genelec. We'll see...

The Fostex's are intended as #4&5 of a 5.1 system, the P.A initially as a center. If the P.A's work they could be replicated and replace the Fostex's, which become my NS-10's.

What got me started on this was a contemplation of getting a Tannoy Gold LSU/HF/12/8 Majorcca for a center speaker. "Signature" aspects of integration with my SGM-10 and various reading about 10 vs. 12" cones (cone-mode breakup and vocal timbre) got me looking around and thinking. So I decided to try a contemporary technological substitute/replacement/test.


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