Hi all,
My domestic life has demanded a down sizing of my open baffles. Its the overall footprint that gets in the way. I have a way forward with a flat baffle, but need some help please.
The current setup is an Eminence Beta 15 in a 40cm sq H fame powered by a Dayton plate amp with adjustable gain 40Hz - 180Hz crossover. Above is an Audio Nirvana super 8 full range, with just a mundorf 150Uf cap bypassed with a .002 auricap to reduce the low frequencies reaching the driver, driven by low powered SET valve amp. See pic
I can use the current dimensions of approximately 40in X 110in, as long as i park them flat against the wall when not in use. No U,W or H frames, simple flat baffle.
I run Linux, so dont have Edge, but what info would be needed. I searched for TS parameters of the AN8 and have two different figures; super 8 on commonsense
QES - 0.169
QTS - 0.162
QMS - 3.836
VAS - 66.495
BL - 11.84
super 8 elsewhere
QES - 0.184
QTS - 0.175
QMS - 3.38
VAS - 73.3
BL - 11.02
Eminence Beta 15A
(1) (2)
Fs 29.86 29.9547
Re 6.005 6.2121
Qes 0.588 0.5716
Qms 4.492 5.6258
Le 1.228 1.3023
Vas 399.26 393.7246
BL 11.51 11.9456
Cms 410.56um/N 404.8192
Mms 69.202 69.7348
Sens. 94.31dB@1W/1m 94.42
rms 2.89 2.33
So this is what i have to work with.
What is the current thinking for driver placement, would you off set the AN8 to inside or outside? Would the Beta 15 be best placed near the floor for floor loading or raised up for more dipole bass?
What about the top of the baffle, I went with a circular design because the imaging was better, but have always felt it robbed a lot of midrange. This might be a chance to correct this.
For imaging, would you round the top or leave it square? I plan to flare the rear of the baffle using a roundover bit.
I have some 5mm heavy rubber damping that i plan to glue to the rear to aid vibration damping.
A lot of questions I know 🙂
Many thanks
Ian
My domestic life has demanded a down sizing of my open baffles. Its the overall footprint that gets in the way. I have a way forward with a flat baffle, but need some help please.
The current setup is an Eminence Beta 15 in a 40cm sq H fame powered by a Dayton plate amp with adjustable gain 40Hz - 180Hz crossover. Above is an Audio Nirvana super 8 full range, with just a mundorf 150Uf cap bypassed with a .002 auricap to reduce the low frequencies reaching the driver, driven by low powered SET valve amp. See pic
I can use the current dimensions of approximately 40in X 110in, as long as i park them flat against the wall when not in use. No U,W or H frames, simple flat baffle.
I run Linux, so dont have Edge, but what info would be needed. I searched for TS parameters of the AN8 and have two different figures; super 8 on commonsense
QES - 0.169
QTS - 0.162
QMS - 3.836
VAS - 66.495
BL - 11.84
super 8 elsewhere
QES - 0.184
QTS - 0.175
QMS - 3.38
VAS - 73.3
BL - 11.02
Eminence Beta 15A
(1) (2)
Fs 29.86 29.9547
Re 6.005 6.2121
Qes 0.588 0.5716
Qms 4.492 5.6258
Le 1.228 1.3023
Vas 399.26 393.7246
BL 11.51 11.9456
Cms 410.56um/N 404.8192
Mms 69.202 69.7348
Sens. 94.31dB@1W/1m 94.42
rms 2.89 2.33
So this is what i have to work with.
What is the current thinking for driver placement, would you off set the AN8 to inside or outside? Would the Beta 15 be best placed near the floor for floor loading or raised up for more dipole bass?
What about the top of the baffle, I went with a circular design because the imaging was better, but have always felt it robbed a lot of midrange. This might be a chance to correct this.
For imaging, would you round the top or leave it square? I plan to flare the rear of the baffle using a roundover bit.
I have some 5mm heavy rubber damping that i plan to glue to the rear to aid vibration damping.
A lot of questions I know 🙂
Many thanks
Ian
Attachments
Hi,
A simple rectangular baffle will do the job, 20" / 50cm
wide, height to suit, I don't know the 8's best listening axis.
A couple of vertical angled rear ribs would do no harm.
Mount the driver in mirror image pairs centered on
7.5 inches from one edge (12.5 the other edge)
and 20 inches (or 10 inches) from the top.
The former is your best bet to go a little lower.
There lots of other things you can do but I'd be just guessing.
I'd surmise the bass end needs passive line level EQ for more
bass boost to work well, or more crudely if you have power
to spare a series high power resistor to increase driver Qts.
Qts(new) = Qts(old) * (Re + Rs) / Re
Where
Qts(new) is the new Qts
Qts(old) is the old/original Qts
Re is the DC resistance of the voice coil
Rs is the series resistance between the amp and the driver
http://www.quarter-wave.com/OBs/OB_Design.pdf
rgds, sreten.
Multiply the numbers by ~ 1.1 for 22" wide, ~ 1.2 for 24" wide.
Wider is always better for OB's but I'd guess 60cm is the limit.
A simple rectangular baffle will do the job, 20" / 50cm
wide, height to suit, I don't know the 8's best listening axis.
A couple of vertical angled rear ribs would do no harm.
Mount the driver in mirror image pairs centered on
7.5 inches from one edge (12.5 the other edge)
and 20 inches (or 10 inches) from the top.
The former is your best bet to go a little lower.
There lots of other things you can do but I'd be just guessing.
I'd surmise the bass end needs passive line level EQ for more
bass boost to work well, or more crudely if you have power
to spare a series high power resistor to increase driver Qts.
Qts(new) = Qts(old) * (Re + Rs) / Re
Where
Qts(new) is the new Qts
Qts(old) is the old/original Qts
Re is the DC resistance of the voice coil
Rs is the series resistance between the amp and the driver
http://www.quarter-wave.com/OBs/OB_Design.pdf
rgds, sreten.
Multiply the numbers by ~ 1.1 for 22" wide, ~ 1.2 for 24" wide.
Wider is always better for OB's but I'd guess 60cm is the limit.
Last edited:
You can't possibly park them "flat against the wall". The basket and magnet assembly will stick out anyway. Are you sure you will not be allowed to box-in that "ugly" rear side of the dipole? 😉
If someone would push accidently against the OB from the back side, the OB might very well fall on its face - desaster! So you need something sticking out from the front to keep the OB safely upright. Did you consider some slim "unvisible" legs, where people will trip over and fall? 😕
You see - having a H frame of at least 30 cm (front to back) depth is not a sinister assault against a beautiful environment, but a question of safe survival. 😀
Could we start from there?
Rudolf
If someone would push accidently against the OB from the back side, the OB might very well fall on its face - desaster! So you need something sticking out from the front to keep the OB safely upright. Did you consider some slim "unvisible" legs, where people will trip over and fall? 😕
You see - having a H frame of at least 30 cm (front to back) depth is not a sinister assault against a beautiful environment, but a question of safe survival. 😀
Could we start from there?
Rudolf
Hi, and thanks for your input.
Rudolf, sorry, the whole point is to get rid of the H frame.....
I really am trying to make it look very simple and slim, and out of the way when not in use.
I do take your point regarding stability and falling over, I will be looking for solutions and any suggestions other than a box to sit them on are very welcome 😉
I was having a senior moment and mixed my imperial up, the dimensions are meant to be approximately 40cm X 110cm not inches, Doh!
Thanks sreten.
I have found the AN8 sound best with the whizzer at ear height, but that might be because of the circular baffle?
With the Beta 15 connected to a separate sub amp, can i not just turn up the wick instead of adding a resistor etc? I have gain available and a bass boost option.
Thanks so far
Ian
Rudolf, sorry, the whole point is to get rid of the H frame.....
I really am trying to make it look very simple and slim, and out of the way when not in use.
I do take your point regarding stability and falling over, I will be looking for solutions and any suggestions other than a box to sit them on are very welcome 😉
I was having a senior moment and mixed my imperial up, the dimensions are meant to be approximately 40cm X 110cm not inches, Doh!
Thanks sreten.
I have found the AN8 sound best with the whizzer at ear height, but that might be because of the circular baffle?
With the Beta 15 connected to a separate sub amp, can i not just turn up the wick instead of adding a resistor etc? I have gain available and a bass boost option.
Thanks so far
Ian
You can see the response of the Beta 15 in a 50 cm wide baffle in this paper. A 40 cm wide OB would make the driver 1-3 dB less efficient at very low frequencies.
Rudolf
I wouldn't off set at all.
Near the floor, definetely.
TSP tell us nothing about the midrange response or radiation pattern of such a driver. Look what others did with the AN8 and follow them - or get into measurement 😉
That is next to nothing. If you have the Beta and the AN8 on the same baffle, you need some good bracing to keep the OB from vibrating too much.
Rudolf
Hi Rudolf,
50cm wide and Beta 15 near the floor it is.
I have looked for other OB projects with the AN8 not much to go on, I don't have any indication of the radiation pattern.
Just asking for best practice / guesses 🙂
I was going to use some oak laminated MDf + rubber but I can by 12mm ply in 2400mm sheets, so would using two sheets glued together, 24mm be a better solution?
What about baffle shape then?
Thanks
Ian
50cm wide and Beta 15 near the floor it is.
I have looked for other OB projects with the AN8 not much to go on, I don't have any indication of the radiation pattern.
Just asking for best practice / guesses 🙂
I was going to use some oak laminated MDf + rubber but I can by 12mm ply in 2400mm sheets, so would using two sheets glued together, 24mm be a better solution?
What about baffle shape then?
Thanks
Ian
Having experience with these drivers and a lot of OB's, I would at least go
with Sreten's comments about the baffle size - 20" wide as a minimum and
get as much baffle height below and above as you can reasonably put up with.
😎
with Sreten's comments about the baffle size - 20" wide as a minimum and
get as much baffle height below and above as you can reasonably put up with.
😎
Thanks Nelson,
I will be using a width of 20" or 50cm this side of the pond 😉
The plywood sheets are 1220mm X 2440mm, so will try a height of 1220mm.
Where would you locate the AN8 , at ear height?
What is your experience of the of the radiation pattern, off setting and etc?
Many thanks
Ian
I will be using a width of 20" or 50cm this side of the pond 😉
The plywood sheets are 1220mm X 2440mm, so will try a height of 1220mm.
Where would you locate the AN8 , at ear height?
What is your experience of the of the radiation pattern, off setting and etc?
Many thanks
Ian
Hi,
122cm height indicates centred on 10" from the top is
more workable. Typical ear height is around 3ft seated.
Assuming 36" and 24" wide :
Driver is mounted centred 9.5 inches (and 14.5 inches)
from the sides.The height would be 5ft, 150cm, 1.5m.
You can optionally lose 12" off the height, but not as good.
Assuming 36" and 20" wide :
Driver is mounted centred 7.5 inches (and 12.5 inches)
from the sides.The height would be 4ft 4", 142cm.
You can optionally lose 10" off the height, but not as good.
If height is 1120mm and width is 500mm then centred on
200mm from one side and 300mm the other and 250mm
from the top is best though more hieght would be better.
I wouldn't skimp on the extra height, it smooths response.
rgds, sreten.
122cm height indicates centred on 10" from the top is
more workable. Typical ear height is around 3ft seated.
Assuming 36" and 24" wide :
Driver is mounted centred 9.5 inches (and 14.5 inches)
from the sides.The height would be 5ft, 150cm, 1.5m.
You can optionally lose 12" off the height, but not as good.
Assuming 36" and 20" wide :
Driver is mounted centred 7.5 inches (and 12.5 inches)
from the sides.The height would be 4ft 4", 142cm.
You can optionally lose 10" off the height, but not as good.
If height is 1120mm and width is 500mm then centred on
200mm from one side and 300mm the other and 250mm
from the top is best though more hieght would be better.
I wouldn't skimp on the extra height, it smooths response.
rgds, sreten.
Last edited:
A few years ago I designed a notch filter for Ians AN8 to flatten the dipole peak. Would that be an acceptable alternative to the offset?
Rudolf
Rudolf
Hi,
Proper offsets just smooth the dipole peak, they don't eradicate it.
If your lucky a 1st order electrical high pass can work well with the peak.
rgds, sreten.
Personally I'd halve the capacitors in the filter section of the sub
plate amplifier to give a far more usable range for this application.
Last edited:
Hi all,
Thanks Sreten for the info on the new dimensions, 112cm height, 50cm width.
Rudolf, you helped me very much in the old circle thread, Danny put me on the circular baffle route that helped with the imaging / soundstage, but it got very confusing in the end. I ended up with the basic configuration here, and just got on with the listening until now.
So, back to the questions...
With 112cm height, 50cm width and the AN8 positioned as Sreten suggested, do i need a notch filter of any other passive components.
Im not sure modding the plate amp is the way to go unless you can steer me through it.
Great link from Dynablaster, very good woodwork, way skilled!
Many thanks
Ian
Thanks Sreten for the info on the new dimensions, 112cm height, 50cm width.
Rudolf, you helped me very much in the old circle thread, Danny put me on the circular baffle route that helped with the imaging / soundstage, but it got very confusing in the end. I ended up with the basic configuration here, and just got on with the listening until now.
So, back to the questions...
With 112cm height, 50cm width and the AN8 positioned as Sreten suggested, do i need a notch filter of any other passive components.
Im not sure modding the plate amp is the way to go unless you can steer me through it.
Great link from Dynablaster, very good woodwork, way skilled!
Many thanks
Ian
Hi All,
Reading through some of site regarding circular baffles, Electro-acoustic models
the expected +6 dB dipole peak, when the rear wave adds fully to the front radiation at 838 Hz for the D = 8" circular baffle. would this have been causing me problems in the existing baffle, would that have affected the mid range?
Dont want to make the same mistakes if possible.
Thanks
Ian
Reading through some of site regarding circular baffles, Electro-acoustic models
the expected +6 dB dipole peak, when the rear wave adds fully to the front radiation at 838 Hz for the D = 8" circular baffle. would this have been causing me problems in the existing baffle, would that have affected the mid range?
Dont want to make the same mistakes if possible.
Thanks
Ian
Hi,
Your circular baffle will give a very bad baffle peak and ripple
compared to the properly offset rectangular case. The latter
will also extend the driver downwards more, the tall option
of the options I outlined the most, and the tall option will
have the smoothest peak and the lowest ripple.
The circular baffle is a bad option in all respects IMO.
You may get away wth a first order on the 8" that flattens
the baffle peak and rolls off below the peak. You may get
away with a passive line level 1st order filter on the feed
to the plate amplifier, into the unfiltered input if it filter
does not go high enough to meet the 8", but carefully
reread MJK's article on the effects of the baffle peak
on the effective x/o frequency of the lower 15".
Note that you will need the passive line level filter
in one form or another to get decent low bass.
See : Baffle Step Compensation
Readjust values for say 10dB and a much lower frequency.
Omitting VR1 and output between the cap and R is low pass.
rgds, sreten.
Your circular baffle will give a very bad baffle peak and ripple
compared to the properly offset rectangular case. The latter
will also extend the driver downwards more, the tall option
of the options I outlined the most, and the tall option will
have the smoothest peak and the lowest ripple.
The circular baffle is a bad option in all respects IMO.
You may get away wth a first order on the 8" that flattens
the baffle peak and rolls off below the peak. You may get
away with a passive line level 1st order filter on the feed
to the plate amplifier, into the unfiltered input if it filter
does not go high enough to meet the 8", but carefully
reread MJK's article on the effects of the baffle peak
on the effective x/o frequency of the lower 15".
Note that you will need the passive line level filter
in one form or another to get decent low bass.
See : Baffle Step Compensation
Readjust values for say 10dB and a much lower frequency.
Omitting VR1 and output between the cap and R is low pass.
rgds, sreten.
Last edited:
I now have the ply wood 112cm height, 50cm, and found 18mm for the same price. so will be 36mm thick.
I will go with sreten's suggested off set.
Still not sure what to do with the crossover, I re read the MJK doc, not clear what i should do.
Many thanks
Ian
Ian,
Where are you going to place the AN8 on that baffle? With that info I could try to find a xover combination in the MJK worksheet.
Thanks Rudolf,
I was going to use the suggested:
If height is 1120mm and width is 500mm then centred on
200mm from one side and 300mm the other and 250mm
from the top is best though more hieght would be better.
I may have a chance to start the woodwork today, I was going to cut the driver holes first.
Thanks, Ian
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