Once I got my hands on famous Visaton AL 170 and needed to
work out what kind of box and what inner volume should a friend
of mine build to achieve good results basswise.
Altough manufacturer provides all relevant data, I still prefer to do it
myself because you never know what production changes may have
been introduced.
There is a saying that picture speaks 1000 words , so there you have
them attached.
If one ever feels the need to build just by relying on data published, in
case of Visaton at least, better think twice. Nothing dramatic but it could
make one think there is something wrong with BR principle, because
factory data are ideal so to say and yet it turned out in my case not to
be so. For the ones wanting to do their own graphs, txt files provided.
Wish you all the best in New Year !
work out what kind of box and what inner volume should a friend
of mine build to achieve good results basswise.
Altough manufacturer provides all relevant data, I still prefer to do it
myself because you never know what production changes may have
been introduced.
There is a saying that picture speaks 1000 words , so there you have
them attached.
If one ever feels the need to build just by relying on data published, in
case of Visaton at least, better think twice. Nothing dramatic but it could
make one think there is something wrong with BR principle, because
factory data are ideal so to say and yet it turned out in my case not to
be so. For the ones wanting to do their own graphs, txt files provided.
Wish you all the best in New Year !
Attachments
What specific object or objects did you use for the "added mass" calculations?
Myself, I used American Nickels...as the American nickel is certified as weighing exactly Five Grams.
Measuring T/S parameters can be tricky........Have three individuals measure one specific driver for their T/S parameters & you will get three different set of values.
_________________________________________________Rick............
Myself, I used American Nickels...as the American nickel is certified as weighing exactly Five Grams.
Measuring T/S parameters can be tricky........Have three individuals measure one specific driver for their T/S parameters & you will get three different set of values.
_________________________________________________Rick............
T-S parameters are not fixed values. The numbers you get actually depend on the method used to get them. I would EXPECT different measurements to give different numbers.
Having said that, the numbers should not be wildly different. An Fs supposed to be 38 should not become 66! That is simply a defect-probably assembled with the wrong spider as Baseballbat hypothesizes. Since that is a free air measurement, your added mass doesn't matter. Return the drivers. Qtc=0.7 will only ever make a horribly boomy vented box.
Having said that, the numbers should not be wildly different. An Fs supposed to be 38 should not become 66! That is simply a defect-probably assembled with the wrong spider as Baseballbat hypothesizes. Since that is a free air measurement, your added mass doesn't matter. Return the drivers. Qtc=0.7 will only ever make a horribly boomy vented box.
Baseball: Both of the drivers were broken in because I got
them second hand and the former owner had them for couple
of years. So I guess that qualifies for breaking in. Inspection
was made at normal room temperature. It was definitely the
suspension.
head: It is a little late for returnig the drivers. I got rid of
them already. Bought them for cheap, resold them the same way.
Am a fan of Visaton and used to work with:
W250S-8; W250-8; W200S-8; AL 200; AL 170; W170S-8;
WS 17E-4; W130S-8; FRS 8; G25FFL, G20FFL; MHT 12
I guess that was on account having the store in my neighborhood.
I have always appretiated and admired german engineering ability
and skills. Would not hesitate to buy again if in need.
them second hand and the former owner had them for couple
of years. So I guess that qualifies for breaking in. Inspection
was made at normal room temperature. It was definitely the
suspension.
head: It is a little late for returnig the drivers. I got rid of
them already. Bought them for cheap, resold them the same way.
Am a fan of Visaton and used to work with:
W250S-8; W250-8; W200S-8; AL 200; AL 170; W170S-8;
WS 17E-4; W130S-8; FRS 8; G25FFL, G20FFL; MHT 12
I guess that was on account having the store in my neighborhood.
I have always appretiated and admired german engineering ability
and skills. Would not hesitate to buy again if in need.
certainly not conventional but I can see some advantages. Lower distortion would be I think the main reason you would do it, but getting it to play a bit lower (say 200 hz instead of 300 or 400) without the early rolloff of a sealed enclosure may be another. Worse transient response is a tradeoff, but if crossed high enough maybe this is less of an issue? (which kind of defeats the second reason)
I've found when measuring drivers that the program used can give very different results for FS with some drivers. Only some, not sure what it is that causes high FS readings on just some drivers with some software. Speaker Workshop gives high readings on my SB 4" drivers but REW is right on factory specs. If I measure my Vifa 10" both programs give the same result.
Tony.
I've found when measuring drivers that the program used can give very different results for FS with some drivers. Only some, not sure what it is that causes high FS readings on just some drivers with some software. Speaker Workshop gives high readings on my SB 4" drivers but REW is right on factory specs. If I measure my Vifa 10" both programs give the same result.
Tony.
I agree 100 % with you tinitus, only I'm pretty sure AL 170
is more than just a midrange.
not with the 65Hz Fs
either your measurements are off ... or the factory have got drivers with changed surround and spider, without knowing
T/S parameters are curves, not scalars, what you get when you measure depends on where you measure.
Lojzek, what kind of measurig kit are you using?
Here is an example, FE127 i measured using Fuzzmeasure and then the same driver measured by Mark using his factory kit.
dave
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They are almost the same!
Baseballbat has it right. The ONLY parameter that is significantly different is Cms. ALL the other deviations are a direct consequence of this ONE difference (check the formulas!). And Cms is the LEAST relevant parameter of all, when calculating a BR alignment.
What you should be concerned with are VAS*Fs^2 (which determines optimal box volume for a given desired extension) and Fs/Qt (which leads to Fb).
If you calculate those, you'll see that the two sets of values (declared vs. measured) produce the same results, within a very small margin of experimental error.
T/S parameters may be the most widely misunderstood things in DIY audio!
Marco
Baseballbat has it right. The ONLY parameter that is significantly different is Cms. ALL the other deviations are a direct consequence of this ONE difference (check the formulas!). And Cms is the LEAST relevant parameter of all, when calculating a BR alignment.
What you should be concerned with are VAS*Fs^2 (which determines optimal box volume for a given desired extension) and Fs/Qt (which leads to Fb).
If you calculate those, you'll see that the two sets of values (declared vs. measured) produce the same results, within a very small margin of experimental error.
T/S parameters may be the most widely misunderstood things in DIY audio!
Marco
Fs does NOT determine a driver's bass response. Fs/Qt does that. I suggest doing some more reading...
M.
Not an issue at all for F > 50Hz - do the simulations (in the exact same box! e.g. 35L tuned to 38Hz) and look at the resulting Group Delay for F>50Hz!
Would that be 20 degrees Celcius ? I also have great experience with Visaton drivers , cant imagine that fs is that much of . Give REW a try and do another measurement , its free , and see if you get the same results , would be interesting ! Did you measure the drivers horizontal or vertical ?
Cheers ,
Rens
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