Hi everyone, first time poster and first time speaker builder here. Apols if there are good answers to these questions in a thread already - if so, please link!
I'm planning to build some simple 2-way speakers for my first build, using pre-loved drivers that I have to hand (having previously picked up cheap). The drivers are:
I see this very much as a trial run/learning experience. I want to get the best result I can with these drivers, by playing with enclosure size/design (I'm not too limited in terms of size and I'm handy with MDF) and cross-over parameters. That's my plan, anyway! Of course, I'm not 100% certain at this point that i'll get good output across the spectrum with these drivers in a 2-way set up, so I'm prepared to change plan if i have to.
As a starting point, i want to measure the T/S parameters for the Philips 12" drivers, to enter into Vituix CAD software. The drivers are old (early 1970s) and i can't find the parameters online.
I have access to a DATS 2.0 testing system. The DATS gives me most parameters, but I'm missing a few that are the software needs - Sd, Pmax, Xmax, Rms
Given my end goal here, I was hoping i could just guesstimate reasonable values for the missing parameters, perhaps based on similar drivers or a rule of thumb etc. I realise this might sound naive and/or sacrilegious(!) but at least it'd allow me to get started.
So, I'd love some feedback on realistic estimates/ranges for those parameters, for the Philips drivers. OR - any advice on other ways to proceed?
cheers,
Steve
PS
Here are the parameters from the DATS:
Here's the Vituix window, showing the blank values that I don't get from DATS:
Here's a photo of the driver
I'm planning to build some simple 2-way speakers for my first build, using pre-loved drivers that I have to hand (having previously picked up cheap). The drivers are:
- Philips AD 1256/W8 (12" bass driver)
- Electro Voice T35 (tweeter)
I see this very much as a trial run/learning experience. I want to get the best result I can with these drivers, by playing with enclosure size/design (I'm not too limited in terms of size and I'm handy with MDF) and cross-over parameters. That's my plan, anyway! Of course, I'm not 100% certain at this point that i'll get good output across the spectrum with these drivers in a 2-way set up, so I'm prepared to change plan if i have to.
As a starting point, i want to measure the T/S parameters for the Philips 12" drivers, to enter into Vituix CAD software. The drivers are old (early 1970s) and i can't find the parameters online.
I have access to a DATS 2.0 testing system. The DATS gives me most parameters, but I'm missing a few that are the software needs - Sd, Pmax, Xmax, Rms
Given my end goal here, I was hoping i could just guesstimate reasonable values for the missing parameters, perhaps based on similar drivers or a rule of thumb etc. I realise this might sound naive and/or sacrilegious(!) but at least it'd allow me to get started.
So, I'd love some feedback on realistic estimates/ranges for those parameters, for the Philips drivers. OR - any advice on other ways to proceed?
cheers,
Steve
PS
Here are the parameters from the DATS:
Here's the Vituix window, showing the blank values that I don't get from DATS:
Here's a photo of the driver
Hi,
the Sd can be easily calculated, being the cone area: measure the radius of the cone, including half of the suspension. Knowing the radius, calculate the area.
The Pmax is 40W.
The Xmax, I guess could be +/- 3mm
Found this old catalogue: look at the suggested box for that woofer.
the Sd can be easily calculated, being the cone area: measure the radius of the cone, including half of the suspension. Knowing the radius, calculate the area.
The Pmax is 40W.
The Xmax, I guess could be +/- 3mm
Found this old catalogue: look at the suggested box for that woofer.
Hmm, apparently DATs calc'd effective diameter from Fs, Vas, so surprised it didn't go ahead and calc (Sd) = (10.12*2.54)^2*pi/4 = 518.94 cm^2, which falls in line with vintage spec 12".
Re Xmax, FWIW Altec and similar were rated from ~1.3 mm (guitar) - 3.8 mm (reflex, bass horn) (2.2 mm mean)
Re Xmax, FWIW Altec and similar were rated from ~1.3 mm (guitar) - 3.8 mm (reflex, bass horn) (2.2 mm mean)
Interesting for the timeframe or era this speaker is from.
The overall appearance Seems like it would be a rather decent performer for the time.
EBP is 32 so would be rather friendly in a sealed box
Assuming it is paper accordion edge on the stiffer side.
Likely would like a larger box.
Assume typical range for a 12" around 2 to 3 cubic feet
or 60 to 85 liters
Realistic design goal likely around 70 liters sealed
Not being negative. I just doubt the resonant frequency was
29 Hz when brand new. Probably closer to a typical accordion edge 12"
speaker around 45 to 50 Hz
So assume the suspension has loosened up a little over the years.
I would go sealed, but for a attempt at a Reflex.
Likely work with its current looser status. And keep the reflex
at typical 3 to 5 Hz below or above Fs or resonate frequency.
More likely above resonance around 32 to 38 Hz
in a smaller 55 to 65 liter box.
Crossover, just assume typical beaming of a 12" around 1300 to 1400 Hz
and 600 to 700 Hz be a reasonably crossover point for a 2 way to stay away from beaming
and likely typical upper frequency " break up" of a paper accordion type speaker.
Which obviously puts much demand on the High frequency driver.
So even typical 800 Hz 3rd order seems feasible to be more friendly
to less distortion in the High Frequency driver
3 way would guarantee less likely audible peaks at the upper end
and allow more typical 2nd order 300Hz and 3000 Hz crossover.
Otherwise I think a 2 way is a very fun idea. If the High Frequency
driver is capable of a realistic low crossover point to overcome
the directionality of a typical 12"
The overall appearance Seems like it would be a rather decent performer for the time.
EBP is 32 so would be rather friendly in a sealed box
Assuming it is paper accordion edge on the stiffer side.
Likely would like a larger box.
Assume typical range for a 12" around 2 to 3 cubic feet
or 60 to 85 liters
Realistic design goal likely around 70 liters sealed
Not being negative. I just doubt the resonant frequency was
29 Hz when brand new. Probably closer to a typical accordion edge 12"
speaker around 45 to 50 Hz
So assume the suspension has loosened up a little over the years.
I would go sealed, but for a attempt at a Reflex.
Likely work with its current looser status. And keep the reflex
at typical 3 to 5 Hz below or above Fs or resonate frequency.
More likely above resonance around 32 to 38 Hz
in a smaller 55 to 65 liter box.
Crossover, just assume typical beaming of a 12" around 1300 to 1400 Hz
and 600 to 700 Hz be a reasonably crossover point for a 2 way to stay away from beaming
and likely typical upper frequency " break up" of a paper accordion type speaker.
Which obviously puts much demand on the High frequency driver.
So even typical 800 Hz 3rd order seems feasible to be more friendly
to less distortion in the High Frequency driver
3 way would guarantee less likely audible peaks at the upper end
and allow more typical 2nd order 300Hz and 3000 Hz crossover.
Otherwise I think a 2 way is a very fun idea. If the High Frequency
driver is capable of a realistic low crossover point to overcome
the directionality of a typical 12"
I had a sheet where I was playing around to see if I could figure out how to convert and see the relationships between parameters.
So I tried these equations just wondering if I could do it:
Rms = ( 2 * π * Fs * Mms) / (Qms * 1000)
Rms = Mms / (Qms * √(Mms*Cms))
Fs = 50 * π √( 1 / Cms * Mms)
Fs = 1 / ( 2 * π √(Cms * Mms) )
This worked reasonably well for the examples where I had a Rms value (from somewhere), but your measured numbers don't seem to play nice with this.
.
What does hitting the "Calculate T/S" button do?
So I tried these equations just wondering if I could do it:
Rms = ( 2 * π * Fs * Mms) / (Qms * 1000)
Rms = Mms / (Qms * √(Mms*Cms))
Fs = 50 * π √( 1 / Cms * Mms)
Fs = 1 / ( 2 * π √(Cms * Mms) )
This worked reasonably well for the examples where I had a Rms value (from somewhere), but your measured numbers don't seem to play nice with this.
.
What does hitting the "Calculate T/S" button do?
AD 1256/W8 has rather wide rubber surround, so I would guesstimate Xmax at 5-6 mm. For smaller displacement they would likely use accordion or even integrated paper surround. Pmax=40 W as stated in Philips application book.
Sd=(3.14xD^2)/4, where D is diameter as measured on the surround "summit". By Philips drawing D~=27 cm, so Sd=572 cm2.
However, you definitely need a mid if you don't want to cut 1-2 octaves from the region where our hearing is most sensitive. 1256/W8 is a pure woofer, Philips didn't even bothered to measure it higher than 1.2 kHz, implying preferred crossover point of about 600 Hz. T35 is old-school horn tweeter, designed to supplement larger mid horns, as in original Klipsh Heresy. Lowest possible crossover point is 3.5 kHz, and below 1.5 kHz they won't reproduce anything at all.
![T-35[1].jpg](https://www.diyaudio.com/community/data/attachments/1053/1053830-71d2562bdc2e12e55ce6638a556edba2.jpg?hash=cdJWK9wuEu "T-35[1].jpg")
Sd=(3.14xD^2)/4, where D is diameter as measured on the surround "summit". By Philips drawing D~=27 cm, so Sd=572 cm2.
However, you definitely need a mid if you don't want to cut 1-2 octaves from the region where our hearing is most sensitive. 1256/W8 is a pure woofer, Philips didn't even bothered to measure it higher than 1.2 kHz, implying preferred crossover point of about 600 Hz. T35 is old-school horn tweeter, designed to supplement larger mid horns, as in original Klipsh Heresy. Lowest possible crossover point is 3.5 kHz, and below 1.5 kHz they won't reproduce anything at all.
No, it is an early high-compliance "pure woofer" for 3-way acoustic suspension boxes of 50-80 l. Comparable to Acoustic Research AR-2AX woofer, only larger and with stronger magnet.
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In the Philips datasheet, the Fs is 19 Hz. I would ask Inland if the driver was properly breaked-in before measuring it.
The Re value is also high: did you measured it with a multimeter? I don't know if DATS measure it in DC as it should be measured.
Thanks everyone for your responses - much appreciated! Plenty for me to digest here.
The surround is rubber, as per the photos in VoxCelestial photos (and my photo below)
Ans yes it sounds like I'll need to go 3-way, as the t35 tweeter specs recommend crossover at 3.5khz or above. No surprise
Speakers should be well broken in - they're from an old Philips studio monitor. I'll try taking the DATS readings again
Thanks again!
The surround is rubber, as per the photos in VoxCelestial photos (and my photo below)
Ans yes it sounds like I'll need to go 3-way, as the t35 tweeter specs recommend crossover at 3.5khz or above. No surprise
Speakers should be well broken in - they're from an old Philips studio monitor. I'll try taking the DATS readings again
Thanks again!
Haven’t seen that one before, i do have a pair of similar 10”, but i did use a pair of the AD120xx in a subwoofer (with some driver tweaks)
These 12s will be VERY hard-pressed to reach the bottom of the T35. So yes a midrange is needed.
dave
These 12s will be VERY hard-pressed to reach the bottom of the T35. So yes a midrange is needed.
dave
Thanks again everyone for your help. I've decided to use one of these drivers to make a sub. Seems like a good project to start with! If that goes well I'll move on to a pair 2ways per my original plan. Anyway, much appreciated!