I see this Beta 8A is a mid bass driver. what is the cross over freq between it and the tweeter ?
PS: I am following your way into enable tech... Now this is quite interesting stuff 🙂
PS: I am following your way into enable tech... Now this is quite interesting stuff 🙂
Looking at the graph I posted on the previous page (this is the mid driver WITH its crossover - 0.5mH coil I think) we're 5 or 6 dB down at about 4khz acoustically. Electrically it should be about 2khz or so but for whatever reason it hasn't worked that way. Quite possibly this is due to the effects of my baffle step correction filter which precedes the series coil.
I know you are using it as a mid driver but according to spec I got on the net it was developed for use as bass or mid bass driver. http://eminence.com/pdf/beta-8a.pdf
I was just wondering why this choice of driver...🙂
I was just wondering why this choice of driver...🙂
High sensitivity, paper cone, big magnet, old-school roll type surround, cheap price and a couple of quite strong recommendations, including of Panomaniac here. I wanted an 8" for the balance between power handling, beaming (large driver problem) and that sense of ease and naturalness that seems to come from larger drivers. To some it's a small mid but to me it seems a logical choice in some ways, in a 3-way design. Another thing was this size seemed to give choices in crossover frequency, particularly when used with a compression driver in a waveguide. I chose this pairing so I could potentially use crossovers between 1khz and maybe 6khz or so, depending on what my ears tell me I need.
Simon, I completely agree with you on the choice of this driver. Something about paper cones, big magnets and all those other things you mentioned, that gets the music out better than anything else. As a bonus, it is cheap, manufactured by a reputable company, is easily available. Also, it has very quick and smooth roll off in the HF. Very important.
Wow! that's a very flat and wide frequency range for a xover'ed 8"er on such a narrow baffle you have -- down to almost 70~80Hz range nearfield. (for your seat in front of the desk😀 )
I looked several pages back and found this:
http://www.diyaudio.com/forums/mult...baffle-eminence-skytronic-26.html#post2283076
Step back a little, it seems the acoustic xover point falls in the 150~200Hz range. Am I right? Your midrange is still very wide band.😀
I looked several pages back and found this:
http://www.diyaudio.com/forums/mult...baffle-eminence-skytronic-26.html#post2283076
Step back a little, it seems the acoustic xover point falls in the 150~200Hz range. Am I right? Your midrange is still very wide band.😀
To be honest the crossover point in the bass is a bit hazy but it seems to work well enough for now. When that part goes active I could try steeper slopes, though I'm not sure that will be very useful as there's nothing nasty to remove there. I sort of feel that a wide overlap might hide the fact the mid is paper and the woofers are plastic (each with their own signature), but I could be quite wrong.
I can't wait to try BudP's EnABL and other tweaks, I just need to find the always-tacky glue he uses to quell a resonance the Beta 8a has. I can do the pattern rings for now though.
I can't wait to try BudP's EnABL and other tweaks, I just need to find the always-tacky glue he uses to quell a resonance the Beta 8a has. I can do the pattern rings for now though.
Thank you for the XO Simon.
It is interesting that I used almost the same values for the Supravox 215 RTF 64 in a OB design.
contour filter (4.7mH // 14r)
0.39mH series coil
aprox 5r lpad
I did not use the series cap and the zobel.
PS
Please let us know about the special glue.... I guess I could use some to restore my old peerless mids 🙂
It is interesting that I used almost the same values for the Supravox 215 RTF 64 in a OB design.
contour filter (4.7mH // 14r)
0.39mH series coil
aprox 5r lpad
I did not use the series cap and the zobel.
PS
Please let us know about the special glue.... I guess I could use some to restore my old peerless mids 🙂
Wow, almost exactly the same! I don't know if this glue is available in the UK but I'll try to find a substitute if not.
I painted some EnABL pattern rings onto my Beta 8s yesterday. I've listened and found the sound more open and detailed and more dynamic, but with more emphasis on the resonant top end the Beta 8s have. Today I procured the "2 way glue" needed to treat the back of the cone to remove the emphasis these drivers have.
Attachments
Those pressed steel frame 'spokes' of Beta 8 look pretty wide. Some close reflections would occur here and cause colorations.
Some felt pads can reduce that quite effectively.
Some felt pads can reduce that quite effectively.
The paint is Testors Polly Scale Model & Hobby Paint. I chose Rust colour. EdLafontaine of this forum sells EnABL kits which include a pot of paint, the Microgloss (often used with EnABL patterns), a pen handle and nibs/tips to go with it. It's like a fountain pen for paint. He ships worldwide.
CLS - I added some furniture pads under every spoke but perhaps I can go further and improve on that.
The Beta 8A seems to want to be modified a lot 😀
CLS - I added some furniture pads under every spoke but perhaps I can go further and improve on that.
The Beta 8A seems to want to be modified a lot 😀
You may want to coat the dome on the Beta 8 with 2way, after you coat the backside, from pattern to basket. You may even end up with a single coat over the whole cone backside with a second layer, or even three, between the pattern and surround.
This is a very lively speaker!!!!! Just damp out the Raleigh wave resonance until it is gone, you won't loose a noticeable amount of power and the mids will become astonishing.
This is a very lively speaker!!!!! Just damp out the Raleigh wave resonance until it is gone, you won't loose a noticeable amount of power and the mids will become astonishing.
Those mids are already starting to come away from the speakers quite nicely. I'm excited about how it could sound with further work. I should get painting that funny glue on tomorrow. I will start with the rear as prescribed, listen and then consider coating the done. I appreciate the advice given here.
Simon Hi
Just had an OMG moment !
How did you do that ?
I'll read from the start of the thread and no more questions till I have.
Well one more...are there pics of the completed speaker somewhere in amongst this lot ?
Got your mail thanks - replied with pics
Cheers
Just had an OMG moment !
How did you do that ?
I'll read from the start of the thread and no more questions till I have.
Well one more...are there pics of the completed speaker somewhere in amongst this lot ?
Got your mail thanks - replied with pics
Cheers
Sorry I've been slow to update, I've been away. I'll try to get a decent up-to-date picture the speakers tomorrow.
I've posted my impressions of the mid driver treatments as a whole (all done now - PVA dots, Microgloss, EnABL, 2-way glue, pads on spokes, Electron Pools & basket grounding) in the EnABL thread: http://www.diyaudio.com/forums/mult...ng-impressions-techniques-54.html#post2321655
In truth it's really mostly the gloss and 2-way glue, and less so the Enable (and much less so the other things) that have transformed the Beta 8As.
Since I posted the comments in the other thread I've brightened the top end by reducing the parallel resistor in the L-pad circuit by about 0.4R (should give 1dB or so extra top end). The sound on the CDs I've tried so far is very pleasing!!
Tomorrow I may get some fresh tweeter measurements and then make those spacers I need to make the Eminence tweets sit in the right place. Only then can I fairly judge the worth of the APT-50 drivers placed in 8" waveguides.
I've posted my impressions of the mid driver treatments as a whole (all done now - PVA dots, Microgloss, EnABL, 2-way glue, pads on spokes, Electron Pools & basket grounding) in the EnABL thread: http://www.diyaudio.com/forums/mult...ng-impressions-techniques-54.html#post2321655
In truth it's really mostly the gloss and 2-way glue, and less so the Enable (and much less so the other things) that have transformed the Beta 8As.
Since I posted the comments in the other thread I've brightened the top end by reducing the parallel resistor in the L-pad circuit by about 0.4R (should give 1dB or so extra top end). The sound on the CDs I've tried so far is very pleasing!!
Tomorrow I may get some fresh tweeter measurements and then make those spacers I need to make the Eminence tweets sit in the right place. Only then can I fairly judge the worth of the APT-50 drivers placed in 8" waveguides.
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