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Old 14th March 2013, 11:07 PM   #1031
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Quote:
Originally Posted by drewh1 View Post
scottmoose - I hope you can uncover the specs for the met with 200a, that would be so helpful - Also still curious about the volume when using a brace - do i need to increase it to accomodate the space taken up by the brace?
If I can't find it, I'll do an optimised one for you.

Re the brace, good question. Technically yes (and ditto for the volume taken by the driver for that matter) but in practice it's rarely an issue unless it's particularly extreme, in which case the box design can be adjusted to compensate. As a rule, I put a mild fudge-factor into most designs anyway for this & other considerations.
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Old 14th March 2013, 11:50 PM   #1032
drewh1 is offline drewh1  United States
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crap - I just double checked and realized the 200a is only 90db at 1 watt. I need at least 96 - 97 db for the SET. So that leaves me with the 206en in 8". or the 208esigma. I am sure it is in the thread but what is the need for the added resistance with the 208?

Apologies for my oversight.
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Old 15th March 2013, 04:11 AM   #1033
drewh1 is offline drewh1  United States
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I think I got my question answered reading the posts. The 4 ohm resistor apparently helps with bass response by providing some additional DF for SS amps. Paul Joppa commented that since the 2a3 SET I am building has its own 3.5 ohms of output resistance, it would likely not be needed. sound right? so at this point, I am leaning towards the 208eZ, or maybe the 168eZ, mainly cabinet size trade off.
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Old 15th March 2013, 09:44 AM   #1034
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Spot on re whether any SR is required & needing to account for the output impedance / DF of the amplifier.

Glad you pointed it out while I was asleep; I was going to look into an F200a box this morning, but I'll shift it to an ESigma. FWIW, the 208 would be my pick, although it was designed to be used with a helper tweeter from ~10KHz upward. No bad thing; it does what it does well, the tweeter does what it does well, everyone happy. The 168 theoretically gets higher by itself, but the top end isn't much to write home about.
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Old 15th March 2013, 03:35 PM   #1035
drewh1 is offline drewh1  United States
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That time difference is always helpful! BTW, I am 60 years old and have been destroying my hearing my entire life. Thus 14k is out of my audible range anyway. Life gets much simpler as we get older, in some ways at any rate.
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Old 16th March 2013, 04:58 PM   #1036
drewh1 is offline drewh1  United States
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everything seems to point to the 208eZ as the best choice for me, so at this point the plan is build Met with 208eZ - There are specs on the Metronome chart for it - are they accurate? or have you re-modeled it since? I assume the 0 measurement in S0 means the front and back just meet there. Could look cool if mitered well.

Thanks again for your help.
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Old 17th March 2013, 10:44 AM   #1037
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Assuming a high output impedance amplifier, revised Met. for the 208ESigma.

L = 68in
St = 4in x 3in
Sl = 12in x 10in
Zd = 34in
Vent = 4in diameter x 1in long.
Line top, back & one sidewall with 1in acoustic fiberglass or similar & adjust this & duct length to suit. Stock it's a flat alignment tuned to Fs as you can see. The downward firing vent will give some damping effect depending on how large you make the legs & the surface it's standing on.
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File Type: png 208Met.png (49.3 KB, 378 views)
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Old 17th March 2013, 05:01 PM   #1038
drewh1 is offline drewh1  United States
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cool - that's a large beast huh! thanks for running that. I'm working on the amp right now and will let you know how the speaker project progresses.
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Old 1st April 2013, 08:37 AM   #1039
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If you are not adverse to a SS amplifier you might try the new Marantz which has current feedback (and not voltage).
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Old 11th April 2013, 02:31 PM   #1040
tnargs is offline tnargs  Australia
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Hi everyone, are there any suggestions for the dimensions of a Metronome to bipole with the ACR Swiss (Fostex) FE-103S (Sigma) driver?

I have 4 of these drivers and a Metronome bipole looks like a good project.

Driver parameters are:

Fs 79 Hz
Re 7.3 ohm
Z 8 ohm
Qms 2.8
Qes 0.29
Qts 0.26
Vas 6.2 litre
Mms 2.9 g
SPL (1W/1m) 92 dB
Sd 55 cm2
Rms 0.55 kg/s
Cms 1.43


Thanks if anyone can help or advise me.
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