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Old 2nd December 2004, 02:18 AM   #1
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Default diyAudio Full Range Reference Project

Has anyone given some thought to the idea of a diyAudio Full Range Reference Project and groupbuy?

My thoughts were:

A modestly priced driver. Say the FE103/107 or FE126/127. The 40-1197 would have been a strong canidate if it was readily available.

The enclosure would be a simple t-line or folded pipe with dimensions that would allow the use of standard boards so that the woodworking was not scarry.

A simple BSC, a well documented webpage and of course rhe friendly and knowledgable in the forum.

This way, several of use could compare speakers to this reference project and discuss.

Anyway, it is just a thought.

Regards,
GM.
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Old 2nd December 2004, 06:28 AM   #2
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Not a bad idea... the FE127 seems a nice balance between bass & top... Tim Forman has been playing with them...

My preferred BSC is bi-pole :^)

dave
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Old 2nd December 2004, 12:50 PM   #3
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I think having a bipole FE127E folded pipe would be a good one. I know this takes away from one of the goals which is to describe a method for designing a BSC circuit. Perhaps the challenge would be to build a BSC circuit that could rival the bipole method used in the reference project. After all, the purpose of a reference project is to set a high bar that future builds are compared against, correct?
These are the initial numbers I come up with using Martin King's MathCAD worksheet .
L=40"
zDriver = 20"
zPort = 38"
So = 6.5" x 1.5"
SL = 6.5" x 12"
Density = .25
rPort = 1.5"
Lport = 4.0"
Driver parameters were taken from the published Fostex numbers and the drivers are wired in series.
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Old 2nd December 2004, 11:33 PM   #4
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Default GM-ML Voigt

Quote:
Originally posted by planet10
Not a bad idea... the FE127 seems a nice balance between bass & top... Tim Forman has been playing with them...

My preferred BSC is bi-pole :^)

dave
The BSC would help keep costs down and could serve as a BSC primer course for new builders.

A bipole 126/127 would be in the price range of a 166/167 and 206/207. At that price would a single 166 or 206 be money better spent?

I love the idea of the GM-ML Voigt

http://www.diyaudio.com/forums/showt...120#post519120

It can be very sharp looking and the use of standard size boards makes it an attrcative project for those who are not expert wood workers.

Perhaps something similar to the GM-ML Voigt with a FE103/107 or FE126/127 with BSC is a good idea.

Cheers,
GM.
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Old 2nd December 2004, 11:41 PM   #5
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Quote:
A bipole 126/127 would be in the price range of a 166/167 and 206/207. At that price would a single 166 or 206 be money better spent?
This causes many builders to shy away from bipoles. The advantage of the FE167E for the same price would be a gain of 10Hz lower BR at the cost of a larger cabinet. The reduced cabinet resonance and better bass control is gained in the bipole configuration along with increased power handling and increased SPL output.
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Old 3rd December 2004, 01:04 AM   #6
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Quote:
Originally posted by Timn8ter


This causes many builders to shy away from bipoles. The advantage of the FE167E for the same price would be a gain of 10Hz lower BR at the cost of a larger cabinet. The reduced cabinet resonance and better bass control is gained in the bipole configuration along with increased power handling and increased SPL output.

I don't understand how a bipole configuration provides equal increase in SPL across the entire frequency range. I would guess that the SPL increase in HF responce at the listening postion would be much less than the LF responce.

I would also think that the placement of a bipole in a room would be more critical, making it less versatile as it may not be suitable for some rooms.

Of course, these are just my thoughts. I have never actually heard a bipole.

Regards,
GM.
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Old 3rd December 2004, 01:11 AM   #7
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Quote:
Originally posted by gmilitano
I don't understand how a bipole configuration provides equal increase in SPL across the entire frequency range. I would guess that the SPL increase in HF responce at the listening postion would be much less than the LF responce.
actual on-axis SPL is the same at mid frequencies as a monopole, but there is no need to slice 3-6 dB off that for baffle step. The power response is doubled, and is uniform unlike a monopole. No ugly reative BSC components means a happier amplifier.

Quote:
I would also think that the placement of a bipole in a room would be more critical, making it less versatile as it may not be suitable for some rooms.
true... but not as critical as you might think... if you need a BSC circuit you aren't that close to the back wall anyway, a bi-pole will probably work fine

Quote:
Of course, these are just my thoughts. I have never actually heard a bipole.
I was skeptical at 1st to. Now i'm a convert.

dave
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Old 3rd December 2004, 02:19 AM   #8
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Quote:
Originally posted by planet10
actual on-axis SPL is the same at mid frequencies as a monopole, but there is no need to slice 3-6 dB off that for baffle step. The power response is doubled, and is uniform unlike a monopole. No ugly reative BSC components means a happier amplifier.
This is what I was thinking, the monopole and bipole would have the same on-axis SPL at mid to high frequencies. I guess what I don't understand is why the monopole would require a BSC and the bipole would not if the on-axis SPL at mid to high frequencies is the same for both configurations.

Quote:
Originally posted by planet10

I was skeptical at 1st to. Now i'm a convert.
The unfortunate part is that I will likely have to build a pair for myself to have a listen.

Cheers,
GM.
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Old 3rd December 2004, 02:31 AM   #9
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Quote:
Originally posted by gmilitano
This is what I was thinking, the monopole and bipole would have the same on-axis SPL at mid to high frequencies. I guess what I don't understand is why the monopole would require a BSC and the bipole would not if the on-axis SPL at mid to high frequencies is the same for both configurations.
Because in the monopole, the bass (ie below baffle-step) has as much as 6 dB less SPL than the bi-pole. The BSC circuit chops this (up to) 6 dB off the mid/highs so that they are equal to the lows. In a bipole there is no baffle-step.

Once a BSC filter is added the monopole has up to 6 dB less SPL than the bipole.

dave
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Old 3rd December 2004, 03:10 AM   #10
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Default W3-871S Bipole

Ok, I have been sold on the bipole. The increased SPL would be nice for those who have low power tube amps.

In addition to the FE127 bipole, perhaps a bipole W3-871S may also be an option.

The cost would be much lower with the TB driver. However, the TB driver has a relatively high Fs ~110Hz.

GM.
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