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Old 19th February 2014, 08:12 PM   #1
cubdog is offline cubdog  United States
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Default Best 8in FR with Eminence Alpha 15a

I'm planning to build some OB speakers using two Alpha 15s per side. Approximate baffle dimensions will be 25x50. Is their any consensus as to the best 8 inch FR driver to use with the Eminence? I've looked at Betsys, A.N. Super Cast 8, Fostex FE206 EN and a few others. I think I'm leaning towards the Audio Nirvana but I'm wide open to other suggestions in this price range.

I have never build any speakers and I'm, unfortunately, pretty ignorant to the mechanical working of speakers and their design. Sorry if this has been touched on before. I've read a lot of the OB threads which has both enlightened and confused. I just haven't seen if there is a clear cut favorite 8 in driver and why. Thanks.

cubdog
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Old 20th February 2014, 12:25 AM   #2
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I think you are on the right track and will end up with an great sounding system. Currently, I am listening to the TB 1808 on top of a single Alpha 15 and it sounds terrific. The TB has a sonic character (a bit forward and very detailed) but can sound very realistic with good recordings. The Betsy and any Fostex should also be great. I never heard any of the AN drivers but I'd imagine they are very good too.
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Old 20th February 2014, 12:44 AM   #3
xrk971 is offline xrk971  United States
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I would go with a smaller full range on top to reduce beaming that 8 in drivers may have. A 4 inch or smaller full range will have much better uniform polar response.
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Old 20th February 2014, 02:19 AM   #4
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The Tang Band 8 inch fullrangers have very good dispersion! Excellent drivers, one of the best I've heard!

Larry
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Old 20th February 2014, 03:07 AM   #5
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I'm with xrk on driver size. The biggest i'd go would be Alpair 10p.

I've heard all the 8" mentioned except the Cast 8" (which i would like to), the stamped basket ones were quite dissapointing.

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Old 20th February 2014, 03:54 AM   #6
ScottG is offline ScottG  United States
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Quote:
Originally Posted by xrk971 View Post
I would go with a smaller full range on top to reduce beaming that 8 in drivers may have. A 4 inch or smaller full range will have much better uniform polar response.
+1


For value with a single driver I'd select the 4 ohm version (TC9FD-18-04) of the Vifa/Peerless TC9FD18-08 in the more recent version of the "Manzanita".

For something with greater efficiency I'd go with 4 of the 16 ohm version (TC9FD15-16) wired in parallel.
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Old 20th February 2014, 01:01 PM   #7
xrk971 is offline xrk971  United States
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+1 on the TC9FD as a full range top for an OB. Here is a measurement of the Vifa in an OB with XO at about 300 Hz. It has very nice response and HD is about -50dB.

Click the image to open in full size.

More info in the "Cheap and FAST OB" thread.
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Old 20th February 2014, 01:55 PM   #8
cubdog is offline cubdog  United States
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I had not thought about using anything smaller than an 8 inch driver. I know a couple of guys who use 8 in drivers with great success. Plus there are quite a few examples of this configuration online.

Does anyone know size driver was used on the Jamo OB? Or for that matter what does Emerald Physics use. I believe they use 15in Eminence drivers.

I'll definitely look into using a smaller full range. I want to do this right the first time if possible.

cubdog
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Old 20th February 2014, 07:32 PM   #9
ScottG is offline ScottG  United States
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Quote:
Originally Posted by cubdog View Post

..Does anyone know size driver was used on the Jamo OB? Or for that matter what does Emerald Physics use. I believe they use 15in Eminence drivers..

cubdog
I think the Jamo (909 & 907) was using a 4.5" driver with a tweeter (..and no rear tweeter for a dipolar effect).

It also had problems relating to the baffle and the midrange because they didn't off-set the driver on the baffle:

Jamo Reference R 907 loudspeaker Measurements | Stereophile.com

(..it's the 1 kHz "dip" from the baffle).

Emerald has used both coaxial drivers and just horns/waveguides for higher freq.s.

BOTH designs are not at all simple as far as crossovers go.



The Edge can show you baffle modeling effects with an open baffle (and it's easy to use):

Tolvan Data


Note that there are problems if you don't "chamfer" the rear of the driver's "opening" as I've mentioned here (with a technique to avoid complex router-work/chamfering):

Ultimate OB Gallery


Below are some good off-set driver examples with (IMO) good aesthetics:
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Old 20th February 2014, 08:02 PM   #10
cubdog is offline cubdog  United States
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Quote:
Originally Posted by ScottG View Post
I think the Jamo (909 & 907) was using a 4.5" driver with a tweeter (..and no rear tweeter for a dipolar effect).

It also had problems relating to the baffle and the midrange because they didn't off-set the driver on the baffle:

Jamo Reference R 907 loudspeaker Measurements | Stereophile.com

(..it's the 1 kHz "dip" from the baffle).

Emerald has used both coaxial drivers and just horns/waveguides for higher freq.s.

BOTH designs are not at all simple as far as crossovers go.



The Edge can show you baffle modeling effects with an open baffle (and it's easy to use):

Tolvan Data


Note that there are problems if you don't "chamfer" the rear of the driver's "opening" as I've mentioned here (with a technique to avoid complex router-work/chamfering):

Ultimate OB Gallery


Below are some good off-set driver examples with (IMO) good aesthetics:
Thanks for the information. Regarding the chamfering, I planning to use 1 inch oak planks for my baffle. I have no tools, or skills for that matter. Hopefully whoever I hire will understand this chamfering technique. I'm sure I'll be asking more questions.

cubdog
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