Based on the frequency response graph of the FE108 below, what 1st order crossover point (just a capacitor) do you think I should try as a starting point? I forget if you choose a 15K xo point if that means it will be -6db at that point or what?
http://www.fostex.com/speakerparts/pdf/FE108Sigma.pdf
http://www.fostex.com/speakerparts/pdf/FE108Sigma.pdf
Based on the frequency response graph of the FE108...
i'd start around 10k (2 uF on an 8 ohm T) and then shrink it from there.
Althou the technique i find most useful is to start with a cap i know will be too small and keep increasing it bit by bit until the T starts getting in the way, then back it off a bit.
dave
i'd start around 10k (2 uF on an 8 ohm T) and then shrink it from there.
Althou the technique i find most useful is to start with a cap i know will be too small and keep increasing it bit by bit until the T starts getting in the way, then back it off a bit.
dave
The second part of the question is something I have wondered too. When you say the crossover point is 10k does that mean where the curve starts sloping down? I assume so, but a 10k crossover point between 2 drivers means where the two lines cross-right? Usuallly this is a notch between the two. right?
Variac said:
You want both to be down 3 dB at the XO point, but it isn't a 2-dimensional problem, since as you go off axis the larger cone will be rolling off sooner.
That is why in the end you have to listen.
dave
Brad,
Which tweeter are you planning on using? I want to do something similar with my FE204's, but haven't decided on a tweeter yet.
Just curious...
🙂
Which tweeter are you planning on using? I want to do something similar with my FE204's, but haven't decided on a tweeter yet.
Just curious...
🙂
I found an interesting tweeter that I'm considering using with my Fostex 208's. The easiet way to see specs is go to Madisound
http://www.madisound.com/ then select catalog then vifa.html then MG 27T G29-04
This is a dome tweeter that has a wide resonance up to 96 db from about 11k to 22k. Others have told me that the 4 ohm impedence is no big deal because it is such a tiny load on the amp and will in fact make it even more efficient. I only need the range from 11k up so it seems like it might work.
Will a tweeter like this sound bad in the resonance band?
It is unusual to find a dome with this kind of efficiency- in fact the trick is that I only want that narrow resonant band. Waddayouthink?
http://www.madisound.com/ then select catalog then vifa.html then MG 27T G29-04
This is a dome tweeter that has a wide resonance up to 96 db from about 11k to 22k. Others have told me that the 4 ohm impedence is no big deal because it is such a tiny load on the amp and will in fact make it even more efficient. I only need the range from 11k up so it seems like it might work.
Will a tweeter like this sound bad in the resonance band?
It is unusual to find a dome with this kind of efficiency- in fact the trick is that I only want that narrow resonant band. Waddayouthink?
lawriebuck - Pray tell, do you want to add a tweeter to your Fostex FE 204's because they lack treble, seem dull, and percussions don't float out into the room?
Variac said:
But only on axis. It is falling like a rock off axis. I have some Vifas that claim 97 dB, don't have them to hand so can't tell you what model. It is semi-horn loaded.
dave
Mr. Planet, I was biased in favor of the dome because I thought it would have good dispersion.
Is the Fostex FT17H better in this regard? It seems to roll off about 7 dB at 30 degress off center up to 20k.
Thanks
Is the Fostex FT17H better in this regard? It seems to roll off about 7 dB at 30 degress off center up to 20k.
Thanks
Variac said:
Good point. I took the 2 factory graphs and scaled the fostex to match the Vifa. The top is the straight comparison -- the fostex is more efficient. The bottom is level shifted so that we can compare the curves. And if we make the assumption that the curves in the Vifa are for the same angles as the Fostex, they are actually pretty close.
To get better HF dispersion you need to go to a smaller dome -- and i haven't run across any 10-14 mm units that boast 97 dB.
Chris and i did find that even with a simple conical horn (thickness of the baffle) on a specific 14 mm unit we had to pad it down about 3 dB vrs using it as a straight radiator.
dave
Attachments
Hey Dave,
Thanks for doing the work to compare these two.
I note you expanded the scale for the Fostex vertically too.
As you have clearly noticed, Fostex tends to compress the vertical axis on their curves.
I now have a suspicion that this of axis response is pretty typical for most tweeters. I wonder about the Vifa ring radiator?
not efficient enough for me though.
I guess the dome might work. I like the fact that I wouldn't have to pad it down, plus it's different for a high eficiency speaker to have a dome, and maybe smoother to 30 degrees off center.
Any idea what Audax the Hammer now uses? any other high efficiency cheapish tweeter ideas. Any info on piezos-their quality might be as good as any at these very high frequencies.
Thanks for doing the work to compare these two.
I note you expanded the scale for the Fostex vertically too.
As you have clearly noticed, Fostex tends to compress the vertical axis on their curves.
I now have a suspicion that this of axis response is pretty typical for most tweeters. I wonder about the Vifa ring radiator?
not efficient enough for me though.
I guess the dome might work. I like the fact that I wouldn't have to pad it down, plus it's different for a high eficiency speaker to have a dome, and maybe smoother to 30 degrees off center.
Any idea what Audax the Hammer now uses? any other high efficiency cheapish tweeter ideas. Any info on piezos-their quality might be as good as any at these very high frequencies.
theoracle said:
Yeah, that's about it...!
I am using them in some Voigt pipes at the moment, and there is a severe lack at the frequency extremes that annoys the hell out of me.. Imaging is good but it's still too boxy for me.
The plan is to build Linkwitz Phoenix subs, running active, and add a tweeter to the FE204 on an open baffle, with a first order passive XO.
I want to sort out the tweeter first, so any suggestions are welcome. My initial idea is to try the FT17H.
Lawriebuck
🙂
lawriebuck - I too wondered about a tweeter, and looked for the model on the Hammer 12 site - to no avail. The treble was sold to me as 'accurate' and 'who would bother with tweeters' I can't think what I could have done wrong, I can't rationalise the following/ hype from full-range enthusiasts to what I've been hearing - CD and LP
And now I'll mention the harshness and distortion that prevents any sort of volume before my ears wince in discomfort. Not all connections are soldered yet, around the speaker wiring, but I can't see that doing much harm after a few weeks. (Run in time is 70-100 hrs approx)
My box is 3.2 cu ft (90 litre) reflex with reasonable bass. It's the rest I'd like to improve - a lot!
Planet 10 - show yourself and take arms!
theoracle
And now I'll mention the harshness and distortion that prevents any sort of volume before my ears wince in discomfort. Not all connections are soldered yet, around the speaker wiring, but I can't see that doing much harm after a few weeks. (Run in time is 70-100 hrs approx)
My box is 3.2 cu ft (90 litre) reflex with reasonable bass. It's the rest I'd like to improve - a lot!
Planet 10 - show yourself and take arms!
theoracle
theoracle said:
If you are not using solid core speaker cable, give it a go... it's pretty good at ameliorating the harshness but I guess this is amp dependent also....
I thought I would put my FE204's into some BR cabinets, but then decided to go to an open baffle set up after hearing a Linkwitz sub at OzAudio's house... very nice fast transparent bass. It's a lot more difficult to put together, but the instructions on Linkwitz's web site seem easy enough to follow. I don't know how it's going to end up, but that's part of the fun , isn't it?
planet 10 - a slight jibe at you (call to arms) You are one of many who convinced me to go the full-range route, but it has not been a happy experience - so far.
lawriebuck - sorry for the delay in replying, I'd be amazed if solid core would largely fix it, but wont close my mind off to it.
I'm using a Naim Nait 3 as the amp (this has sounded fine with a number of usually 2-way speakers) and a Philips CDR-778 cd player
I'ts so hard to figure what others are used to listening to and what their expectations are. But it sure isn't the lo-fi this is!
I notice Dick Olsher has a correction filter to enable the Fostex FE208 sigma to be listenable (used as open baffle) with a 15" sub
Cheers for now
P.S. it isn't fun when it's the grocery money
the oracle
lawriebuck - sorry for the delay in replying, I'd be amazed if solid core would largely fix it, but wont close my mind off to it.
I'm using a Naim Nait 3 as the amp (this has sounded fine with a number of usually 2-way speakers) and a Philips CDR-778 cd player
I'ts so hard to figure what others are used to listening to and what their expectations are. But it sure isn't the lo-fi this is!
I notice Dick Olsher has a correction filter to enable the Fostex FE208 sigma to be listenable (used as open baffle) with a 15" sub
Cheers for now
P.S. it isn't fun when it's the grocery money
the oracle
theoracle said:
Ha Ha Ha! I am sure we can all relate to that, don't feel too bad!😀
The NAIT3 is a lovely little amp. Naim reccommend against solid core, the best cable then is probably their own NAC A5, or whatever it's called. This is good cable for the price anyway.
I am getting some prices and avail. on the FT17H Fostex tweeter from an Australian supplier. I plan to fiddle with them a bit to see what I can achieve, but as for the lower octaves, I think active bass is the only way to go. From what I have read, and in my (so far) limited experience, I think it is folly to expect meaningful bass from these "Full-range" drivers.
Perhaps someone else could comment on your Amp/Speaker interaction? I know Planet10 has had a bit of experience with Naim amps with Fostex drivers....
🙂
theoracle said:
I'm a firm beleiver that the best full-range systems often end up being 3-way with the FR covering 100-150 Hz up to 10k+. Some of the really good FRs will allow you to not add a helper tweeter at the top. I have made some quite lengthy posts on this subject.
But i do enjoy a good FR even with limited extension on the top & the bottom. My recent Pacific NW GeekFest efforts are really quite pleasant but have nothing below 100 Hz.
dave
planet 10 - Unfortunately, we can't hear what each other is hearing (only 10,000 miles!) but it can't be this distortion as the volume and musical complexity rise. Regardless of any other welcome positive attributes, the harshness and fatiguing nature can actually discourage a listen, I was most surprised.
Part of my 'quality' test is a non audiophile sat down and subjected to a song or 2 (someone that does like music) and see how long they last, without chatting or asking to turn it down, most enlightening.
the oracle
Part of my 'quality' test is a non audiophile sat down and subjected to a song or 2 (someone that does like music) and see how long they last, without chatting or asking to turn it down, most enlightening.
the oracle
Oracle,
I haven't received my FE208EZ yet, but others have told me the old 208 needs the notch filter the be listenable. The Basszilla is one place to find the filter, but there are other mentions of other filter versions online.I don't think you have specifically stated if you have the 204 or 208. I you have the 208, the Basszilla notch is probably essential. If the sound seems distorted then that must be something else........
The new FE 208EZ also has a peak in about the same place- just a different shape. I'm gonna try the old filter on mine.
I haven't received my FE208EZ yet, but others have told me the old 208 needs the notch filter the be listenable. The Basszilla is one place to find the filter, but there are other mentions of other filter versions online.I don't think you have specifically stated if you have the 204 or 208. I you have the 208, the Basszilla notch is probably essential. If the sound seems distorted then that must be something else........
The new FE 208EZ also has a peak in about the same place- just a different shape. I'm gonna try the old filter on mine.
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