It does make sense from the troubleshooting point of view. As I mentioned before 120 is more suitable for a 2 way because of its lower Fs.
I’ve plugged the numbers provided by Dave in to Bass Box pro. It comes out weird. The average impedance of the 2 drivers wired in PARALEL is about 20 ohms. Can’t be correct. In addition, based on Dave’s limited data, impedance of each driver is 50 ohms, which is unheard of. I do suspect a problem with measurements but if they are correct, this drivers are insane and you would do a million times better with 6,5 Vifas or actually anything else that doesn’t have 50 ohms resistance.
The easiest thing you could do at this point is to measure the resistance of the voice coil with simple millimeter. This way we can troubleshoot it better. It’s easy. Disconnect the driver and measure the resistance between (+) and (-) on the driver. This would be your RE or DC voice coil resistance. Should be about 6 ohms if I had to guess.
I’ve plugged the numbers provided by Dave in to Bass Box pro. It comes out weird. The average impedance of the 2 drivers wired in PARALEL is about 20 ohms. Can’t be correct. In addition, based on Dave’s limited data, impedance of each driver is 50 ohms, which is unheard of. I do suspect a problem with measurements but if they are correct, this drivers are insane and you would do a million times better with 6,5 Vifas or actually anything else that doesn’t have 50 ohms resistance.
The easiest thing you could do at this point is to measure the resistance of the voice coil with simple millimeter. This way we can troubleshoot it better. It’s easy. Disconnect the driver and measure the resistance between (+) and (-) on the driver. This would be your RE or DC voice coil resistance. Should be about 6 ohms if I had to guess.
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planet10 said:
Something is definitely screwy with those numbers as I can assure you they do not have that kind of resistance or my amp would not be able to run them. Besides, if that were the case the speakers would sound terrible which they don't. They actually sound pretty good. I seem to remember that the SPL on these was around 90 or 91 acording to the Zetag engineer. What my speakers currently lack is real good articulation, or clairity in the upper mid frequencies. I suspect that the mistake was the use of the TC90 as opposed to the TC120. As pointed out, the 120 has a lower fs and is better suited to the 2 way design that I am using. The TC90 sounds good but thin especially in the lower treble/upper mid areas. I will measure the resistance on the voice coil and post.
fantfool said:
That is most likely mid-woofer related, and not anything to do with the tweeter.
dave
planet10 said:
Normally I would agree, but the x-over is designed to blend the woofer and tweeter rolloff within a certain frequency band. What I think I am hearing is the woofer portion, albiet not fully produding this frequency band, and the tweeter not being able to because of its limitations. With the lower fs of the 120, the hole that currently exists I think will be filled in.............at least I hope!
fantfool said:
Hi,
Do you have a schematic of the crossover? If not, do you know enough about crossovers to verbally describe it (ie: a second order, with ____cap and ___inductor - fill in the blanks with the values).
If you could measure the midwoofs DC impedance (Re), that would be useful.
How big did you say the box is?
MJL21193 said:
I have that data from the ones i measured at home -- from the posted impedance curve, around 6 ohms.
dave
planet10 said:
Going on these numbers, I calculate a 30 litre box (a little more than 1 cubic foot) is the ideal size for a vented box. Fb of 28hz, F3 of 38hz.
The calculated port length is too long though - 90cm.
This driver will most likely work much better in the same size sealed box. Fb of 48hz, F3 of 69hz.
fantfool said:
For vented? Similar results, I'm afraid. The port tube needs to be too long. The problem with these speakers for a vented box is their low VAS.
They might be suitable for passive radiators, but I've not modeled that.
If you mean two drivers in one sealed box, the box could be about 40 litres, with an Fb of 52hz and F3 of 65hz. This might be your bet bet.
fantfool said:
A tweeter can and does produce output through its fs, just as a woofer does.
Apologies for stating the obvious, but does it sound coherent with the polarity reversed?
Yep, the numbers are screwy.
Anyways, I just averaged based on Planet’s graph and guessed the impedance as 8 ohms. The numbers I get are similar to MJL’s. 44 liters ported MTM with Fb of 34hz. This gives 2 impedance humps at 20hz and 60 hz. Single 3” d port, 8 inches long. Box would be 22,3/4 by 14 by 8,3/4. Other dimensions could be used for as long as the volume is the same.
Close box MTM with targeted Qtc of 0.5 (I’d like to have a slightly over dampened center channel, box comes out to 45 liters with f3 of 78hz. Impedance has a single hump at about 50hz.
This is with driver connected in parallel.
Again, designing a proper crossover will require measurements. I know, you want to just swap the 90 for 120 but it’s not going to help. 90 could be crossed over slightly higher with this woofer, say between 2800hz and 3400hz with 4th order x-over and the woofer could be fine with 2nd order. Either tweeter will work, 90 is a bit harder to cross but not impossible.
We need Re and at list a description or a picture of the existing x-over.
Anyways, I just averaged based on Planet’s graph and guessed the impedance as 8 ohms. The numbers I get are similar to MJL’s. 44 liters ported MTM with Fb of 34hz. This gives 2 impedance humps at 20hz and 60 hz. Single 3” d port, 8 inches long. Box would be 22,3/4 by 14 by 8,3/4. Other dimensions could be used for as long as the volume is the same.
Close box MTM with targeted Qtc of 0.5 (I’d like to have a slightly over dampened center channel, box comes out to 45 liters with f3 of 78hz. Impedance has a single hump at about 50hz.
This is with driver connected in parallel.
Again, designing a proper crossover will require measurements. I know, you want to just swap the 90 for 120 but it’s not going to help. 90 could be crossed over slightly higher with this woofer, say between 2800hz and 3400hz with 4th order x-over and the woofer could be fine with 2nd order. Either tweeter will work, 90 is a bit harder to cross but not impossible.
We need Re and at list a description or a picture of the existing x-over.
R-Carpenter said:
No offense but I don't think those numbers are entirely accurate, at least based on what the Zetag engineer told me. Anyway, are the dimentions you list internal or external. My external main cabinet diminsions are about 11" X 15" X 39" but the bottom 12" I added for ballast so they are not part of the internal volume. I used 3/4" MDF and 1/4" oak veneer. There is considerable bracing inside, kind of a unique method too. I will post a drawing, some of which I did on autocad and some I got from him. Also, I tried to take a picture of the x-over which I am trying to attach. Not a great picture but see if you can determine what you were looking for. Well I can't attach because it's too big of a file. I will try again tomorrow. I tried to post a scanned copy of one of the drawings but it was too big also.
22x14x9=2772 cubic inches / by 1728 =1.6 cubic ft. = approximately 43 liters.
Find conversion calculators on net. There’s plenty.
All numbers are averaged for now till we get woofer measurements and x-over pick.
Find conversion calculators on net. There’s plenty.
All numbers are averaged for now till we get woofer measurements and x-over pick.
R-Carpenter said:
I get gross internal volume of 45.4 litres ... Zetags recommended MT box for the drivers i measured was about 13 litres.
DCR = 5.7 ohms
dave
I found my calcs and the internal volume not counting bracing etc was 25.5" X 11.75 X 9.5"= 2846.43 or 1.65 cu ft.
By the way when I was talking about the numbers not being right I was talking about the driver specs, not the box size.
By the way when I was talking about the numbers not being right I was talking about the driver specs, not the box size.
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