super tweet xo for Fostex FE108S ???

Status
Not open for further replies.
Jump to Latest
#25
Tipping the drivers back is probably more effective to compensate for the rising rate of response without messing up imaging?

Heres's a wild idea that I just heard about on another thread

http://www.murata.com/speaker/tw/pdf/es103.pdf

It's a piezo tweeter rated from 15k to 100k response!
Anyone know the price? 15kH might not be low enough!!
Also would require a separate amp because it's efficiency is only 90 dB -maybe use a gainclone? Dave, I know you've tried piezos. It seems to me even the cheap ones might be OK at the 10k and up range. Any opinions?
 
#27
Hello All,
I am now in the same boat as the rest of you "Full Rangers" (tm)
Thats the hard ridin' division of Dave's Frugalphile (tm) army.
I just received my pair of Fostex FE208ESigma drivers from Madisound

They have about 6 pair left. At $175 ea. they are a bit pricey, but MAN , they have quality written all over them! The cast basket is beautiful. I have always felt (with no practical experience) that whizzer cones are an undamped menace, ( I know about the foam ring under trick) ,and since I am planning to use a tweeter I am not bothered that these roll off a bit lower than some full range speakers. Instead of a whizzer cone they have a whizzer dome. Interestingly, the spider has a scaled up cloth version of similar design to the cone surround. It is lumpy, not accordian pleated like most speakers. Dave mentioned in another thread that these have a truckload of design in them and it really shows. How do they sound? So far just hooked to a mid fi receiver on an FM station, voices sound VERY natural. Further reports when my wife leaves the house and I can pull them out again. 😉

OK I DO have a question: Remember the Vifa dome MG 27T G29-04 that Dave plotted a page ago against the Fostex 17 horn tweeter? I am still considering it because it seems to roll off a bit smoother, albeit maybe a bit more off axis and it is less efficient, but that is the appeal, maybe it matches the efficiency of the FE 208 E sigma well enough that an Lpad is not needed or at least very small value resistors,


BUT there is a problem. The FE208 is rated about 96 dB/watt/meter according to it's graph. It is an 8 ohm driver.
The MG 27T is rated about 95-96 dB 2.83 V /meter at 10k and is 4 ohm. I was told by someone I trust that since I am crossing over at 10,000 hz, the 4 ohm tweet will put very little stress on the amp and will coexist fine with the 208. My impression has been that being 4 ohm might give me another 3 db efficiency too.

Please comment, the 2.83v vs. 1 watt ratings have me confused.
 
#28
Variac said:
The MG 27T is rated about 95-96 dB 2.83 V /meter at 10k and is 4 ohm. I was told by someone I trust that since I am crossing over at 10,000 hz, the 4 ohm tweet will put very little stress on the amp and will coexist fine with the 208. My impression has been that being 4 ohm might give me another 3 db efficiency too.

Please comment, the 2.83v vs. 1 watt ratings have me confused.
Click to expand...

This is one of those misleading specs... 2.83 V into 4 ohms is 2W so these are really 92-93 dB 1W.

If you have a SS amp that doubles its power into 4 ohms you should be OK on the loudness level. If you are using tubes you are out of luck.

dave
 
#29
Thanks Dave, I was planning to use my Son o Zen if ever finished, so my understanding is that it does not put out more power at lower impedences, so I think the domes don't work. Nice to eliminate another option..

I think the argument for the 2.83 V spec is that it does respresent the behavior of the vast majority of amps (solid state amps that put out more current to lower impedences) , so maybe it isn't deceptive for most people. (or maybe I have this wrong too)

🙄
 
#30
Variac said:
I think the argument for the 2.83 V spec is that it does respresent the behavior of the vast majority of amps (solid state amps that put out more current to lower impedences) , so maybe it isn't deceptive for most people. (or maybe I have this wrong too)
Click to expand...

I think it is just plain misleading -- marketing. The majority of amps thing is BS. Most HT amps (which if not the largest sector in amp sales already, will be soon) do not want you to even hook up 4 ohm loudspeakers (so they don't have the current capability) and tubes amps don't. It is probably that only a select set of amps approach doubling their power into 4 ohms.

dave
 
#32
Since Ed says he measured the Horns (w/FE108s) at -3db at 17K. I had experimented with caps all the way down to 2.2uF for a crossover of 18K (4ohm), and things are sounding better but still too bright.

Then, it just hit me today perhaps why....

The ATD LeRibbon is a 4 ohm tweeter rated at 91db and the Fostex FE108S is 8 ohm rated at 92db.

Because the tweeter is 4 ohms, it's going to play much louder at the same volume setting than the 8 ohm driver (run in parallel) right? Sorry, that's probably obvious to you speaker designers out there.

So how do I figure out the right resistor network to pad down the tweeter?

... again, I'm just trying to add a little air to the Horns without messing up the mids.

thanks, -Brad-
 
#34
planet10 said:
I think it [giving speaker sensitivity ratings @ 2.83 Volts instead of @ 1 Watt] is just plain misleading -- marketing. The majority of amps thing is BS. Most HT amps (which if not the largest sector in amp sales already, will be soon) do not want you to even hook up 4 ohm loudspeakers (so they don't have the current capability) and tubes amps don't. It is probably that only a select set of amps approach doubling their power into 4 ohms.

dave
Click to expand...

It should be said that good solid state power amps these days are expected to put out high current. Also, there is something of a trend for amps to be 6 ohms, to be equally at home at 4 ohm or 8 ohm.

Still, I don't like the spec. I think this 2.83V rating is mostly there to pass off a 4 ohm speaker as being 3 dB more sensitive than it really is.
 
#35
I'm running a push-pull 300B amp at ~20-30w/ch but may be migrating to a lower powered SET soon.

I guess I'll just have to tune it by ear. Mybe stick a pot on the tweet and then measure the R when it sounds right and then replace the pot with a resistor. Is just a resistor in series with the tweet good enough, or do you need some kind of "L" configuration (pad?) ???
 
#36
The other thing I don't get is when I measure the (static) resistance of the LeRibbon tweeter, it's zero ohms! And I checked my meter, it's working fine. How can this be? If this is the way a ribbon tweeter is supposed to be (how it works), then how do you design a crossover with/for it?
 
#40
the guy at e-speakers told me to try 0.5uF for an XO near the 17-18K I want. Boy was my 2.2uF WAAAYYY off !!!
He wouldn't tell me how he came up with that value, but he did say the LeRibbon tweeter has a transforer in series with it - which explains the ~zero resistance it has.
 
Status
Not open for further replies.
Top Bottom