OB 3-way with Alpha 15a & ribbon - what midrange driver? - diyAudio
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Old 16th January 2009, 12:53 PM   #1
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Default OB 3-way with Alpha 15a & ribbon - what midrange driver?

I have a pair of OB speakers with Eminence Alpha 15a and Fostex FE207E drivers crossed over at about 300Hz. These sound very good but I'm keen to build something a bit better.

I love the OB bass and lower mid, but the FE207E gets a bit rough in the upper mids and HF. It also beams a lot at HF.

I'm keen to build something better and like the idea of an open-back ribbon to open up the top end. Something like the B&G Neo3 PDR looks good to me... what do you guys think?

Should I stick with the FE207E as a midrange driver or change this for something else?

I had a first order crossover with the old speakers but I realise I'll probably have to go for 2nd order to ensure the ribbon is protected. I think this means I should also change to 2nd order for the bass to mid crossover - is this right?

Any advice/experience would be appreciated.
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Old 16th January 2009, 01:14 PM   #2
tinitus is offline tinitus  Europe
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It all depends on how high you plan to use your woofer, but from what I hear in here it will play quite good lower mid

Further a ribbon wont like to be crossed too low, so you need mids that goes high

With a tandem of Visaton FRS8M you might get surpried, and they are cheap at 11 EUR

Monacor SPH-176 might work very nice

Monacor SP-6/100PRO is another interesting altternativ, very similar to the above, but carbon cone and higher sensitivity
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Old 16th January 2009, 01:50 PM   #3
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Default Re: OB 3-way with Alpha 15a & ribbon - what midrange driver?

Quote:
Originally posted by sharpi31

I'm keen to build something better and like the idea of an open-back ribbon to open up the top end. Something like the B&G Neo3 PDR looks good to me... what do you guys think?

but I realise I'll probably have to go for 2nd order to ensure the ribbon is protected.
The Neo3 pdr can handle 10 microF, simple electrical first order but this do not mean you have a first acoustic order carachteristic , exerpt you cross very high.
Anyway I agree with tinitus a little mid is better for those kind slopes.

What is your sensitivity target? I think you can have some very good
4" extended range, to say TB 1337SA for example ( work very well together neo3pdr) if you can live with about 86-87 dB speaker

Cheers,
Paolo
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Old 16th January 2009, 02:47 PM   #4
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I own a pair of CSS FR125SR and also a pair of TB W4-1320SD, but hadn't thought of using these as the sensitivity is so much lower than the Alpha 15a and the ribbon.

Ideally I'd like to keep the efficiency around 93dB or higher so I could use a 2.5Wpc tube amp as well as my UCD180HG power amp.

The FE207E would be sensitive enough, but maybe a little rough for use as a dedicated midrange driver...

Something like the FE126E could be good. No whizzer so probably a bit cleaner in the mids than the FE207E - also a smaller driver so less beaming. The efficiency is still good at 93dB...

I'd like to pick crossover points that are well within the clean range of the drivers. With a 11dB notch filter on the Alpha 15 (between 1.2KHz and 3.5KHz) this driver could easily be used up to 750Hz-ish. Of course it could be crossed over lower if this made more sense.
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Old 16th January 2009, 03:14 PM   #5
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Is it the Alpha 15 93dB after BSC and equalization? I do not think.

Cheers,
Paolo
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