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Old 14th March 2011, 03:39 PM   #1
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Default Bofu is gone, but how about this?

The pioneer bofu is gone and I'm looking to try a g chang or curvy chang build. I'm looking for a cost effective alternative.

PE has this woofer from pioneer:
Pioneer B20GR30-51F 8" Butyl Surround Woofer

It specs out a little different from the Bofu (qts) but is quite efficient and looks to have a very similar motor structure.

I noticed on this forum that a lot of guys have removed the whizzer cone and added a helper tweeter to the Bofu anyway.

So my question is three fold:

1) Is this a suitable alternative to the Bofu assuming the use of a tweeter?

2) Are there other alternatives that are cost effective for the g chang or curvy chang?

3) What tweeter would I use as a good match?

I know that GRS has a "Bofu type" driver on PE, but I have no experience with GRS.

I'm also aware that this is essentially a two way post in the full range section, but this seemed like the place to ask considering I talking about building a chang.

Thanks in advance.
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Old 14th March 2011, 04:56 PM   #2
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Not a bad idea at all to find another driver that would work in the Chang. And yes, it was typically implemented with a tweeter anyway. But i'd bet that Pioneer driver will be gone too in time. Did i read somewhere that Pioneer is not going to sell raw drivers anymore? I am not sure if that's the case.
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Old 14th March 2011, 05:10 PM   #3
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I haven't heard that. These seem to me to be in a great price range, have great reviews and look heavily built.

I'm no expert on what T/S parameters I need to pay attention to specifically for the chang.

Any help would be appreciated.

On a side note I'm also thinking of re-creating my first pair of good speakers with these woofers just for fun. Dahlquist M-905.
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Old 14th March 2011, 06:22 PM   #4
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Quote:
Originally Posted by hooligan72 View Post

I'm no expert on what T/S parameters I need to pay attention to specifically for the chang.
When looking at T/S the most important are Fs, Qt, Vas. Use the Fostex FE207e as a baseline.

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Old 14th March 2011, 09:17 PM   #5
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qts is right on
vas is about 13l different
fs is off by 8hz

What do you think?
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Old 14th March 2011, 09:39 PM   #6
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That puts Vas within ~20% higher. It would suggest that the driver is still within the envelope. It may well give a bit of a bass boost. A little more damping might b called for.

You should give it a go.

dave
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Old 14th March 2011, 10:11 PM   #7
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I'm thinking about the HiVi SD1.1-A for the tweeter. It seems to have the required efficiency and range. It is also reviewed very well over at PE.

Oh yeah, it's cheap too.

I'll keep looking. I think Vifa has some candidates as well that may be in budget.
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Old 15th March 2011, 03:03 AM   #8
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Default Another alternative

Depending on your local price you could also consider the Visaton BG20

8"
92dB
8 ohms
Qts 0.44 (higher is better for OB?)
Fs 38 Hz
Vas 3.88 cu ft

You will need a tweeter, but you'd planned for that anyway.

cheers

Doug
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Old 15th March 2011, 03:13 AM   #9
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You're going to need more than a super tweeter with that woofer. Even though its frequency response goes out there, you can be sure it doesn't sound very good above maybe 1KHz. Go and look at the frequency response graph. Even if it did have a smooth extended frequency response, it would still beam like crazy in the higher frequencies. Get a tweeter that can crossover low, like maybe 2KHz.
http://www.parts-express.com/pdf/290-042.pdf

Quote:
Originally Posted by hooligan72 View Post
The pioneer bofu is gone and I'm looking to try a g chang or curvy chang build. I'm looking for a cost effective alternative.

PE has this woofer from pioneer:
Pioneer B20GR30-51F 8" Butyl Surround Woofer

It specs out a little different from the Bofu (qts) but is quite efficient and looks to have a very similar motor structure.

I noticed on this forum that a lot of guys have removed the whizzer cone and added a helper tweeter to the Bofu anyway.

So my question is three fold:

1) Is this a suitable alternative to the Bofu assuming the use of a tweeter?

2) Are there other alternatives that are cost effective for the g chang or curvy chang?

3) What tweeter would I use as a good match?

I know that GRS has a "Bofu type" driver on PE, but I have no experience with GRS.

I'm also aware that this is essentially a two way post in the full range section, but this seemed like the place to ask considering I talking about building a chang.

Thanks in advance.

Last edited by AEIOU; 15th March 2011 at 03:16 AM.
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Old 15th March 2011, 02:44 PM   #10
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The visiton b 20 looks interesting and fits within efficiency and FS. Vas is almost double though. The driver also specifies that it is geared towards pro sound. That makes me wonder about low spl bass response.

Any other recommendations?

Thanks for the post on the PE test results on the pioneer woofer. It does seem mildly ragged over 1500hz and rather terrible over 2000hz. I knew I would need more than a helper tweeter for something like this.

What what do you think of the HiVi tweeter listed above? Any alternatives?

I am under the impression that the benefits of the chang designs are primarily under 2000hz in which case crossing at 2000hz seems like the ticket.

Any feedback welcome? Thanks.
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