Yay!
Am I correct to assume this is the first Jeff Bagby speaker design that will be tested here on ASR? Or has there been others?
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Build of Bagby Mandolin speaker
- Thread starter RickS
- Start date
Am I correct to assume this is the first Jeff Bagby speaker design that will be tested here on ASR? Or has there been others?
OP
- Thread Starter
- #43
OP
- Thread Starter
- #44
Am familiar with their heritage, but am busy with Directiva and funding it.
May have to hope for a loaner or see if there is enough interest to fund a build.
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OP
- Thread Starter
- #46
yes
Great. 
I haven’t used that tweeter either. Apparently it’s been updated with a new metal faceplate.
as you commented bigger woofers and bigger boxes make for a bigger and better sound, at least when 2-way traditional boxed speakers are concerned.
Do you have all those speakers from your build list still, to compare?
I’m really looking forward to the Klippel NFS rotato-gram.
Really appreciating your work.
I haven’t used that tweeter either. Apparently it’s been updated with a new metal faceplate.
as you commented bigger woofers and bigger boxes make for a bigger and better sound, at least when 2-way traditional boxed speakers are concerned.
Do you have all those speakers from your build list still, to compare?
I’m really looking forward to the Klippel NFS rotato-gram.
Really appreciating your work.
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Hi Wolf,
what do you cosndier are the strong points of this design?
I’ve never heard it, but knew that it had certain design targets.
OP
- Thread Starter
- #49
Great.
I haven’t used that tweeter either. Apparently it’s been updated with a new metal faceplate.
as you commented bigger woofers and bigger boxes make for a bigger and better sound, at least when 2-way traditional boxed speakers are concerned.
Do you have all those speakers from your build list still, to compare?
I’m really looking forward to the Klippel NFS rotato-gram.
Really appreciating your work.
This speaker is with @amirm and is queued up to be tested.
Honestly, to that point, The Continuums had the lowest HD of any design Jeff had done, top down to about 100Hz. Jeff said so himself on numerous occasions, and to me on premise at his place. The smoothness is almost glossy it's so good, and other than the BBC-inspired midbass voicing, it was flat in response. Bass was not its strong point, but in the vocals and treble they were astonishingly clear. I might even build a pair since I have the drivers on hand. They are a reference that should be appreciated.
That is high praise given your speaker design experience.
beagleman
Major Contributor
OP
- Thread Starter
- #55
Welcome to ASR!
You may be right on the diffraction but the question is how much? Even without diffraction being factored, modeling suggests that the crossover needs to be lower. The review nearfields suggest this too.
OP
- Thread Starter
- #56
While the design did not call for it, to reduce any speculation (and still had my 7/8" roundover bit in the router), here is the difference between the rounded edge and not...
Red trace is before (not rounded) and green is after (7/8" round). Clearly at this point, diffraction is NOT a significant contributor to the 3k Hz dip as you can see the response barely changed.
Red trace is before (not rounded) and green is after (7/8" round). Clearly at this point, diffraction is NOT a significant contributor to the 3k Hz dip as you can see the response barely changed.
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If you make on axis and 30 degrees off axis measurement and the hole at 3kHz doesn't start to fill in (which would surprise me) then you can conclude that you don't have a problem with diffraction and attribute it to poorly engineered crossover or drivers.
What you've tested there enables us to see how much edge diffaction makes of the whole diffraction profile of that baffle with tweeter at that specific position.
What you've tested there enables us to see how much edge diffaction makes of the whole diffraction profile of that baffle with tweeter at that specific position.
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OP
- Thread Starter
- #58
You have a point on overall diffraction. This was a quick test just before I move on to other things. Am working on another Directiva build and was planning to repurpose the Mandolin cabinet. I removed the drivers and it is being readied for baffle removal.
Aside from the box tuning (which can be modified to builder’s taste), it is not my intention to redesign any of the DIY kits I have built. While there is clearly a more target rich opportunity to enhance commercial speakers, I would rather spend my efforts on more forward looking designs.
Hi Rick,
interestingly I recently discovered a problem with one of Jeff Bagby Revolution Mini 1/4 cu ft speaker; almost by accident.
I was taking in-room measurements of this speaker, to compare it to my Purifi 0.7cu ft (vented Fb:35Hz) design. Really just for kicks.
Apart from the wild swings up and down under 300Hz in my room for the L vs R speaker placement, a very curious thing turned up in the Revolution Mini that didn’t occur in my Pure Millennium 2 way.
One of my Revolution Mini speakers had a hole at 3Khz, similar to this Mandolin.
I didn’t think the room could affect this. After a lot of troubleshooting, I tracked it down to one shorted capacitor(!) in my HP filter for the tweeter.
I was shocked because
a) I’d not heard this 3Khz hole when listening; at least not with both speakers together
b) I’m not sure when the cap was shorted- a faulty cap from new, or during use (~1 year old speaker)
Had I run a full impedance trace of both speakers when I built them I would have detected the mismatch.
Among other things it highlights the dangers of DIY speakers- apart from building things incorrectly (really easy to do; plenty of times in the past I have I’ve done all kinds of boneheaded things) but without basic measurement tools (Dayton Audio Tester System; or similar) I would have have detected this.
I’m sharing this with you since I know Jeff seemed to prefer an acoustic LR4 1.8Khz crossover for many of his 2-way designs, with an 2nd order on his woofer leg and 3rd order on tweeter leg.
Do you have another tweeter to compare to?
Did the Mandolin/2 speaker come with a published impedance trace? I wonder how else you can check whether it’s a tweeter issue or crossover issue? Do you have another tweeter or crossover to compare to?
interestingly I recently discovered a problem with one of Jeff Bagby Revolution Mini 1/4 cu ft speaker; almost by accident.
I was taking in-room measurements of this speaker, to compare it to my Purifi 0.7cu ft (vented Fb:35Hz) design. Really just for kicks.
Apart from the wild swings up and down under 300Hz in my room for the L vs R speaker placement, a very curious thing turned up in the Revolution Mini that didn’t occur in my Pure Millennium 2 way.
One of my Revolution Mini speakers had a hole at 3Khz, similar to this Mandolin.
I didn’t think the room could affect this. After a lot of troubleshooting, I tracked it down to one shorted capacitor(!) in my HP filter for the tweeter.
I was shocked because
a) I’d not heard this 3Khz hole when listening; at least not with both speakers together
b) I’m not sure when the cap was shorted- a faulty cap from new, or during use (~1 year old speaker)
Had I run a full impedance trace of both speakers when I built them I would have detected the mismatch.
Among other things it highlights the dangers of DIY speakers- apart from building things incorrectly (really easy to do; plenty of times in the past I have I’ve done all kinds of boneheaded things) but without basic measurement tools (Dayton Audio Tester System; or similar) I would have have detected this.
I’m sharing this with you since I know Jeff seemed to prefer an acoustic LR4 1.8Khz crossover for many of his 2-way designs, with an 2nd order on his woofer leg and 3rd order on tweeter leg.
Do you have another tweeter to compare to?
Did the Mandolin/2 speaker come with a published impedance trace? I wonder how else you can check whether it’s a tweeter issue or crossover issue? Do you have another tweeter or crossover to compare to?
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OP
- Thread Starter
- #60
No, no published impedance trace. I did check the Mandolin crossover to make sure it was fully working though. I did try to sim the design in VCAD and it did replicate the dip in a simple model using the SB curves. So, I am fairly confident that the crossover is most of the problem.
Since seems unlikely Jeff messed up, the driver changes must have impacted the design more than expected. As Meniscus continues to market, seems they should own the situation, but Mark has not demonstrated any interest in addressing.
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