The below was instructions on Techtalk on how to attain VAS from DATs V2 when the you need to add more weight on the driver with the added mass method.
1. Take your first TS measurement. Let say you come up with a Fs of 50Hz. Deduct 25% off this value, which would give you 37.5Hz.
2. Add weight slowly while repeating the TS measurement until you obtain a Fs of about 37Hz.
3. Take the weight off the woofer, and do a normal TS measurement.
4. Add the weight back on, then perform the Vas measurement. If the weight is still insufficient, add additional weight in small increments until DATS is happy.
5. Hope this helps.
It seems like there is no in-between the original Fs and say 70% less. My tweeter is a paper cone vintage tweeter which is very stiff and I can't manage to get the VAS. I tried the above method but unfortunately once you put a weight on it reduces the Fs by about 80% and any amount of weight less than the one i had just put gives you the original Fs.
I can't find any other info no how to attain the VAS with teh DATs V2, the methods are not in any instruction other than the added mass method. Is there a way to guess it? Or can anyone tell me more about vintage paper cone stiff tweeter Fs is about 1300?
I never thought my first speaker design will be attempted on vintage speakers but it is the way it is. And Im a little stuck on deciding on the tweeter cabinet.
As it plays pretty low I am guessing it will need a cabinet? Small one im guessing....
1. Take your first TS measurement. Let say you come up with a Fs of 50Hz. Deduct 25% off this value, which would give you 37.5Hz.
2. Add weight slowly while repeating the TS measurement until you obtain a Fs of about 37Hz.
3. Take the weight off the woofer, and do a normal TS measurement.
4. Add the weight back on, then perform the Vas measurement. If the weight is still insufficient, add additional weight in small increments until DATS is happy.
5. Hope this helps.
It seems like there is no in-between the original Fs and say 70% less. My tweeter is a paper cone vintage tweeter which is very stiff and I can't manage to get the VAS. I tried the above method but unfortunately once you put a weight on it reduces the Fs by about 80% and any amount of weight less than the one i had just put gives you the original Fs.
I can't find any other info no how to attain the VAS with teh DATs V2, the methods are not in any instruction other than the added mass method. Is there a way to guess it? Or can anyone tell me more about vintage paper cone stiff tweeter Fs is about 1300?
I never thought my first speaker design will be attempted on vintage speakers but it is the way it is. And Im a little stuck on deciding on the tweeter cabinet.
As it plays pretty low I am guessing it will need a cabinet? Small one im guessing....
T & S parameters are useful measurements to be used in evaluating bass speakers and aiding enclosure design. I see no benefit in trying to derive a Vas figure for a tweeter and in any case, the majority of tweeters have the rear of the diaphragms enclosed . The only exceptions are vintage models such as the Wharfedale Super 3 series. Adding a weight to the usual delicate cone of a tweeter is not advisable either.
Thank you, I had a feeling hence why I asked if someone can tell me more about vintage tweeters. Its not a wharfedale and it doesn't have an open back.
But if its playing the mid frequencies(well, I will measure and see if I need a dedicated mid driver) would it need a enclosure? This is where I am stuck on. Or can a two or three litre enclosure be okay?
I have the woofers enclosure size once I get figure out the tweeters enclosure size I can mock up a cabinet with chipwood and take measurements.
Anyway, a few more tips regarding a paper tweeter with a Fs of 1300 would be really appreciate it.
If it's a closed back type, no, it doesn't require a sub-enclosure. The closed back already provides that. You could add one anyway, purely to isolate the driver structure from some vibration caused by the LF driver, but I doubt it would make any audible difference in this case.
The 'normal' recommendation would be to cross the tweeter above its FS. Therefore you will not really be playing midrange frequencies through your tweeter.
Try to get a piece of scrap wood about the size of your intended baffle, mount the tweeter with no enclosure and measure it. Then add a tiny enclosure to the tweeter and re measure to see if the bottom end of the response develops a peak. (edit: it wont because it has a sealed back, I wrote this reply before the last 2 posts)
Cheers,
Rob.
Try to get a piece of scrap wood about the size of your intended baffle, mount the tweeter with no enclosure and measure it. Then add a tiny enclosure to the tweeter and re measure to see if the bottom end of the response develops a peak. (edit: it wont because it has a sealed back, I wrote this reply before the last 2 posts)
Cheers,
Rob.
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The issue that I believe you are trying to understand is whether an enclosure is likely to raise the resonant frequency of the open back cone tweeter. This is not a problem as there is very little effect unless the rear enclosure is made very small i.e. less than 0.5 litre. To avoid standing waves within the tweeter's frequency range the enclosure should be made as deep as possible and it should be filled with a suitable absorbent wadding.
Above the Fs so I am guessing it will be in the 2000hz at the lowest point higher the better. I know it also depends on the 10 inch woofers highest frequency range, and I won't know what that it till I measure it in a enclosure.
This was my next question and you have answered it. I was going to ask can I just measure it in an open baffle...
This could be a test I do, good idea...
Cheers,
Rob.[/QUOTE]
[/QUOTE]
You don't need to do the last test if the tweeter has a closed back, it will not make any difference.
Try pm'ing 5thElement, he has a soft spot for old school paper tweeters.
Rob.
Thanks, I know the basics of absorbing standing waves in behind the tweeter.
The main reason i have been asking is because the owner wants the tweeter in a separate box so curious how I should make that but I will make it deep like you mentioned and about 1 litre. But I can always leave it in an open baffle as well right?
Thanks for that! I will get in contact. Appreciate it mate!
I don't know if having my first job with vintage drivers is a good thing or bad. But between us or shall I say the new skool guys it makes it easier because many of these vintage guys only listen to poorly designed(not always don't kill me) vintage speakers. Gives me more room to move if I make a mistake or can't get the flattest frequency curve.
It is a closed back tweeter; there are much better tweeters available these days. I would suggest that you will need a midrange speaker if you are using a 10'' bass speaker in the design mix.
Tell me about it I have tried subtly advising my friend that technology and driver technology has advanced so much your better off with new drivers. but vintage guys are obsessed with vintage drivers
I think he does have a mid he wants me to add to mix.
Ultimately, can anyone recommend whether the tweeter should be in the same cab as the 80 llitre woofer or its fine if its in a separate enclosure? If I can put in separate enclosure a couple litres will be fine?
Lastly, can I put it on an open baffle?(sorry I am not versed with open baffle stuff but I am guessing its an option) But it might aesthetically look nice in a open baffle type baffle...
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The typical closed back paper cone tweeter is mounted in the same enclosure as the woofer and in many cases a plethora of other speakers. In most case it is mounted on the inside of the cabinet to effect an airtight seal with the front panel. Since there is no rear radiation to deal with it does not really matter if you mount it in a cabinet or on a baffle. If you are going to use a midrange speaker then it may be easier to utilise an open baffle arrangement. Appearances and placement are major concerns in a speaker re-build and if you are doing this work for a friend then you need to show him sketches of the proposed model.
I think you need to go back to him and have a proper discussion as to what he wants and expects.
Also discuss what you are capable of doing.
Discuss what is realistically achievable.
Write it all down.
Otherwise I can see this being more of a fustercluck than it already is.
Just to make it crystal clear:
If the closed back tweeter is to be placed in a separate box, then that box can be any convenient size or shape. Same goes for an open baffle.
Equally, it can safely be placed in the main woofer enclosure.
Originally he didn't want a crossover, I convinced him otherwise. I am presuming even a basic crossover will work better than no crossover at all.
I understand the difficulties in designing a crossover, but I will give it a shot, I don't want to be deterred. Of course I have to be realistic worst case I can get someone to help me with the crossover modelling(even if it has to be payed). Then I could do the tweaks myself, I would(should) be capable of understanding what changes it might need...
I will mock it up in the appropriate enclosure with his aesthetic design in mind. Take my measurements, make a FRD file(and ZMA) drop it in crossover modelling software and start the process.
Once I have a descent frequency curve I will try it out. I know its not a simple as than but it should give him a half descent speaker considering the drivers are at least 30 years old. Actually, seeing that most of his speakers are old vintage speakers(i have to admit they sound great) it might be a design that has taken more variables in consideration than the rest of his speakers. I know wishful thinking, but its what makes me tick...
Given those rust holes in the back casing the owner might actually be right in asking for an enclosure, I am guessing, but they might not be airtight any more. I have seen it happen a couple of times
Proper designed XO perhaps not but at the minimum a vintage speaker would have had a capacitor in series with the tweeter. There might even be a "rule of thumb" for what capacitor size to go with what cone diametre but I've not seen one but the smaller the diametre of the cone the higher the Fs and therefore the smaller the capacitor value.
I have a few old XO boards on my bench if you like I'll see what the values were on some Akai and Yamaha from the 70s
I have a few old XO boards on my bench if you like I'll see what the values were on some Akai and Yamaha from the 70s
If corrosion has produced open holes in the back casing then they should be filled/covered with epoxy. The correct response of the tweeter will depend on its cone working into the small, sealed volume of the back casing. I would not simply place the leaky tweeter in a larger, substitute enclosure.
If the impedance of the tweeter is 4 ohm then a series 3.9uF polypropylene capacitor would be a reasonable first choice to act as a minimal crossover..
If the impedance of the tweeter is 4 ohm then a series 3.9uF polypropylene capacitor would be a reasonable first choice to act as a minimal crossover..