Hi,
I have build some time ago speakers with fostex ft17H tweeters. The tweeters have a 6db filter @ 10khz and have a l-pad wich gives about -2db, to match the other driver wich is 96 - 97 db 1w/1m. With low volume they are ok, But on louder volumes they tend to hurt my ears, especialy if there's is for example a triangle in the music. Very sharp, resonanting sound. It isn't the amplifier or cd player.
Are there people who have the same tweeter and had the same problem? Mabey the 6db cuttof isn't sharp enough and the driver hase brake up problems? First I thought it were my ears, but a friend experienced the same.
any help is appreciated.
Regards,
Anne.
I have build some time ago speakers with fostex ft17H tweeters. The tweeters have a 6db filter @ 10khz and have a l-pad wich gives about -2db, to match the other driver wich is 96 - 97 db 1w/1m. With low volume they are ok, But on louder volumes they tend to hurt my ears, especialy if there's is for example a triangle in the music. Very sharp, resonanting sound. It isn't the amplifier or cd player.
Are there people who have the same tweeter and had the same problem? Mabey the 6db cuttof isn't sharp enough and the driver hase brake up problems? First I thought it were my ears, but a friend experienced the same.
any help is appreciated.
Regards,
Anne.
Can you describe your speaker in more detail? What is the other driver?
It sounds to me like the supertweeter is crossed to low. Using a 1.0 or possibly a 1.5uF high pass capacitor is more typical with a driver like the FT17. A crossover at 10kHz will probably require a steeper crossover.
Also, is the other driver *really* 96 db? I suspect that it isn't, especially after the baffle step. Only measurement can tell for sure.
GB
It sounds to me like the supertweeter is crossed to low. Using a 1.0 or possibly a 1.5uF high pass capacitor is more typical with a driver like the FT17. A crossover at 10kHz will probably require a steeper crossover.
Also, is the other driver *really* 96 db? I suspect that it isn't, especially after the baffle step. Only measurement can tell for sure.
GB
Eminence beta 12lt in a 4 cubic feet reflex enclosure. like the afterburner thorsten loesch suggested or poor mans hammer dynamics s12.
Seems the tweeter should sound ok, since several people found it an improvement over the original tweeter used in the hammer dynamics speaker. I've used a zobel on the beta 12lt like the one suggested at the afterburner site.
Mabey I play louder then most people do? I love to hear music once in a while at realistic levels (95-100db peak @ listening spot).
Anne.
Konnichiwa,
Actually, the Betal 12 LT has a 4-6db boost in the range between around 1KHz and 5KHz which needs to be equalised, a RLC parallel circuit should be used in series with the Beta 12LT, I'd suggest 8R2, 0.65mH and 8.2uF fir starters. The resultant driver has then around 95db/W/m sensitivity in the midband with a -6db point around 8KHz. I suspect you omited the RLC equaliser and hence the upper midraneg is 6db boosted, which invariably make sthe sound shouty.
You then need to attenuate the FT17H by around 5-6db to match the sensitivity of the Woofer and you need a crossover that is 6db down at 8KHz, which implies a -3db point of 16KHz. So I would recommend a 2R2 Resistor and 1uF Capacitor in series as first cut. This will have the FT17H with around 95db @ 16KHz slowly rising to it's full SPL which in tunr slopes off above 20KHz, so the result should be a more extended response.
The result should be more pleasant.
Sayonara
Anne said:
Actually, the Betal 12 LT has a 4-6db boost in the range between around 1KHz and 5KHz which needs to be equalised, a RLC parallel circuit should be used in series with the Beta 12LT, I'd suggest 8R2, 0.65mH and 8.2uF fir starters. The resultant driver has then around 95db/W/m sensitivity in the midband with a -6db point around 8KHz. I suspect you omited the RLC equaliser and hence the upper midraneg is 6db boosted, which invariably make sthe sound shouty.
You then need to attenuate the FT17H by around 5-6db to match the sensitivity of the Woofer and you need a crossover that is 6db down at 8KHz, which implies a -3db point of 16KHz. So I would recommend a 2R2 Resistor and 1uF Capacitor in series as first cut. This will have the FT17H with around 95db @ 16KHz slowly rising to it's full SPL which in tunr slopes off above 20KHz, so the result should be a more extended response.
The result should be more pleasant.
Sayonara
OK, first, I'd strongly suggest a coat or two of dammar varnish.
KYW makes a good point in that it is likely that much if not most of the harsh treble is coming from the peaks of the 12LT.
IMO, the supertweeter should be padded down even more, like 10db. Looking at the Beta12LT FR charts, it looks closer to 93db than 97 to me. Besides, if this is out in the room rather than flush against a wall, there will be some additional apparent treble 'gain' from the baffle step.
I finally gave up on my 12LT - or more accurately - tweaked it to death. It finally ended up with no whizzer and a piezo for the highs.
FWIW, I found the beta12LT most pleasant and natural by far in a TQWT. Besides the bass being punchier and more effortless than a bass reflex, the midrange seemed clearer and more natural. Line length was 64" IIRC.
GB
KYW makes a good point in that it is likely that much if not most of the harsh treble is coming from the peaks of the 12LT.
IMO, the supertweeter should be padded down even more, like 10db. Looking at the Beta12LT FR charts, it looks closer to 93db than 97 to me. Besides, if this is out in the room rather than flush against a wall, there will be some additional apparent treble 'gain' from the baffle step.
I finally gave up on my 12LT - or more accurately - tweaked it to death. It finally ended up with no whizzer and a piezo for the highs.
FWIW, I found the beta12LT most pleasant and natural by far in a TQWT. Besides the bass being punchier and more effortless than a bass reflex, the midrange seemed clearer and more natural. Line length was 64" IIRC.
GB
Wow, I'm using the FT17H down to about 6kHz. It's not the best tweeter I've heard, but I think it does OK. I've been thinking of trying a different tweeter for a while now, and maybe it is time to start looking at that again. I have a 2nd order electrical filter on it, if that makes any difference.
Were you referring to the tweeter or the Eminence woofer?
Were you referring to the tweeter or the Eminence woofer?
Thanks.
Has anyone ever damar'd a tweeter? I tried it once on a phenolic diaphragm, can't say I really heard a difference. The varnish just sort of dried on the diaphragm, there didn't seem to be anything for it to soak into. Maybe it was already doped with something. Anyway, I couldn't find an easy way to take the FT17H apart. If I decide to try a different tweeter, I'll probably try tweaks to this tweeter first. I decided not to try any tweaks on my PR170M0 (added duct seal to the basket legs, but that's all), the chances of ending up with something worse than what I have now seem very high.
Has anyone ever damar'd a tweeter? I tried it once on a phenolic diaphragm, can't say I really heard a difference. The varnish just sort of dried on the diaphragm, there didn't seem to be anything for it to soak into. Maybe it was already doped with something. Anyway, I couldn't find an easy way to take the FT17H apart. If I decide to try a different tweeter, I'll probably try tweaks to this tweeter first. I decided not to try any tweaks on my PR170M0 (added duct seal to the basket legs, but that's all), the chances of ending up with something worse than what I have now seem very high.
Of course I was referring to the Beta12LT woofer.
But sure, I've dammared a tweeter.
I found that a couple very thin coats of dammar on focal Ti tweeters removes 90% of the 'edge' they have. It didn't change FR significantly within my measurement capabilities at the time. I presume it took down the ~17khz breakup peak down a bit. It's very easy to do with a fine brush. I tested first on some cheap Dayton PE Ti tweeters. Those are very good BTW.
I still think the problem here is mostly the Eminence's breakup region, combined with mismatched levels. NO way is 2db attenuation enough.
There may be some baffle step issues as well.
GB
But sure, I've dammared a tweeter.
I found that a couple very thin coats of dammar on focal Ti tweeters removes 90% of the 'edge' they have. It didn't change FR significantly within my measurement capabilities at the time. I presume it took down the ~17khz breakup peak down a bit. It's very easy to do with a fine brush. I tested first on some cheap Dayton PE Ti tweeters. Those are very good BTW.
I still think the problem here is mostly the Eminence's breakup region, combined with mismatched levels. NO way is 2db attenuation enough.
There may be some baffle step issues as well.
GB
I'd also consider that the FT17's FR extends almost to 50K. Using this in loud situations can cause some uncomfort. I'm not saying that this is the original problem, but I have run some Piezo's in some monitors that went to 30K, and noticed that they took some 'getting used to'. I wouldn't say they hurt my ears, but were a bit uncomfortable at first at loud levels and i know that it was due to the extended frequency. I use Beta 12LTs in my monitors (different ones) with 94 db Motorla horn tweets. I choose the 94 db as they seemed more natural to my ear with the 12LTs at higher listening levels. The Beta's don't have an x-over, and the tweets just a simple 1st order (don't remeber at what point) so having an adjustable L-pad for different listening levels might be a good idea. I use an active eq set at a +3db hump at 400Hz, a -3 db hump at 1.25K Hz and a +2 db hump around 8K Hz. This adjustment is not from measurement, but by ear, and I've alway been complimented about the sound when I take the system out. I know that I tend to want less high end when I listen to loud levels and don't mind having the high end be a little more present when listening to more 'normal levels'. I guess this is why I don't use my 12LT Monitors at home system 
-D.
-D.
I've shellac'd the whizzer on my beta12lta and have to say that the integration with the FT17h is much better.
I'm a little slow to do the same to the main cone as the shellac may be a little hard. Greb B talks of using amber shellac which is a little softer, and then on small cones.
I just have some commercial Rustins Button polish which says it contains pure shellac. It has worked well with the tweeter, does any one know if its worth the risk with the main cone?
I'm a little slow to do the same to the main cone as the shellac may be a little hard. Greb B talks of using amber shellac which is a little softer, and then on small cones.
I just have some commercial Rustins Button polish which says it contains pure shellac. It has worked well with the tweeter, does any one know if its worth the risk with the main cone?
My preferred doping scheme for a large wideband is shellac on the whizzer and dustcap, and dammar on the main cone.
Shellac on the main cone of a big driver can dry too hard, and make it ring like a bell.
This stuff has a lot to do with personal preference. It's tough to beat experimentation...
GB
Shellac on the main cone of a big driver can dry too hard, and make it ring like a bell.
This stuff has a lot to do with personal preference. It's tough to beat experimentation...
GB
John Sheerin said:
That's weird if it was an on axis measurement, given it's specs. Fit's the specs for 30 degree off axis though.
http://www.madisound.com/ft17h.pdf
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