Hi guys ,
I am doing a project I have a 5 way linear phase active system
Using minidsp and 12ch amps
I have all focal utopia drivers , I just swapped into the focals and I came from a mix of dynaudio and stevens audio.
The stevens tweeter is a 1” soft dome with a back chamber.
The focal be has either a open back or a cap that makes it a sealed back. With open back fs is 250hz with the cap it’s 1500hz
That said , I installed the focals , all the drivers perform as expected except this tweeter. Coming from the stevens , I wish it had similar dispersion as the stevens. The stevens seems to have more energy in the forward lobe and had more equal energy as my listening position has unequal path lengths.
Making a back chamber for the focal would be a cinch. Super easy.
How do I know how big to make it and will it make it have similar dispersion as the stevens
Thanks in advance
I am doing a project I have a 5 way linear phase active system
Using minidsp and 12ch amps
I have all focal utopia drivers , I just swapped into the focals and I came from a mix of dynaudio and stevens audio.
The stevens tweeter is a 1” soft dome with a back chamber.
The focal be has either a open back or a cap that makes it a sealed back. With open back fs is 250hz with the cap it’s 1500hz
That said , I installed the focals , all the drivers perform as expected except this tweeter. Coming from the stevens , I wish it had similar dispersion as the stevens. The stevens seems to have more energy in the forward lobe and had more equal energy as my listening position has unequal path lengths.
Making a back chamber for the focal would be a cinch. Super easy.
How do I know how big to make it and will it make it have similar dispersion as the stevens
Thanks in advance
Ahh I didn’t know that .... maybe I’ll try with cap off
Thanks here’s a link to the driver lmk what you think I should do
https://www.focal.com/sites/www.focal.fr/files/shared/catalog/document/ft_utopia_tbm.pdf
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So if it won’t change dispersion..... what exactly is the point of low fs
If I take the cap off and run open back, will it affect power handling and will it affect anything else if I only need to cross over at 3K....
I’m using a shallow second order slope with a Q of .7
So it digs kind of far down but I don’t know I don’t know what I’m trying to ask I just liked the way that the soft dome sounded better as far as dispersion
This has amazing sound quality.... it’s just different..... maybe it’s just a tuning thing
If I take the cap off and run open back, will it affect power handling and will it affect anything else if I only need to cross over at 3K....
I’m using a shallow second order slope with a Q of .7
So it digs kind of far down but I don’t know I don’t know what I’m trying to ask I just liked the way that the soft dome sounded better as far as dispersion
This has amazing sound quality.... it’s just different..... maybe it’s just a tuning thing
Tis true.
Frankly wasn't sure what he was trying to tell us, so assumed the Focal was OB since it was the only way for it to cause problems since the tweeter is sealed.......
You're welcome, though didn't realize both are tweeters, so with no info on the Stevens and precious little for the Focal, can't really offer any suggestions, though normally the one with the wider dispersion would need a waveguide [WG] to narrow it up to match the narrower tweeter.
No clue what 'IAL' stands for, but I'd use the low Fs for a > 4 kHz 1st order XO.
Yes, it will affect power handling since excursion increases 4x/octave, hence the 4 octave minimum for the 1st order [250*2^4].
Okay so the stevens is a fs of 650hz
The focal with no cap is 250hz fs
So maybe I’ll try just the cap off first and see what it does
I think that IAL means Infinite baffle (guessing)
So what about the done shape , the focal is inverted M shape
Could that be affecting its dispersion a little ?
It’s not bad ..... actually the focal most might say is more accurate, I just wish it had the dispersion of the stevens but had the focal sound.....
Maybe it’s a lost cause and what I’m asking is wrong
As someone pointed out the back chamber doesn’t affect dispersion
The focal with no cap is 250hz fs
So maybe I’ll try just the cap off first and see what it does
I think that IAL means Infinite baffle (guessing)
So what about the done shape , the focal is inverted M shape
Could that be affecting its dispersion a little ?
It’s not bad ..... actually the focal most might say is more accurate, I just wish it had the dispersion of the stevens but had the focal sound.....
Maybe it’s a lost cause and what I’m asking is wrong
As someone pointed out the back chamber doesn’t affect dispersion
The main thing that affects the focals dispersion is that it's a metal dome. Fabric domes breakup in the upper octave and this gives them better off axis response. I'm not entirely sure what to expect from the inverted dome of the focal though.
Metal domes usually have phase shields in front of them, for protection and for improving their off axis response. The focal Be dome doesn't have this. You could try tilting the treble up to add some sparkle and see if that helps.
Metal domes usually have phase shields in front of them, for protection and for improving their off axis response. The focal Be dome doesn't have this. You could try tilting the treble up to add some sparkle and see if that helps.
You're welcome!
From down low to 'x' HF point defined by its VC diameter, all point source drivers are pistonic, so if both have 1" VCs, then both will be pistonic till ~ 13543/pi/1 = ~ 4311 Hz.
This is normally pretty obvious in the response plot as a notch, but is ~ centered in the ~ flat, drawn out 'm' shape in the response, so guessing the 'M' shaped dome is responsible, though judging by its off axis response, not much, if any, different than a dome except way up high where its shape is causing some severe eigenmodes across it [series of big peaks/dips], though with zero info on the Stevens I can't comment on it beyond it's probably a generic mobile audio design.
From down low to 'x' HF point defined by its VC diameter, all point source drivers are pistonic, so if both have 1" VCs, then both will be pistonic till ~ 13543/pi/1 = ~ 4311 Hz.
This is normally pretty obvious in the response plot as a notch, but is ~ centered in the ~ flat, drawn out 'm' shape in the response, so guessing the 'M' shaped dome is responsible, though judging by its off axis response, not much, if any, different than a dome except way up high where its shape is causing some severe eigenmodes across it [series of big peaks/dips], though with zero info on the Stevens I can't comment on it beyond it's probably a generic mobile audio design.
Car audio, right? where are they placed and where are they aimed at?
Making a printed back chamber could give you some aiming opportunity.
I used Vifa ring radiators in my door cards, a tweeter not known for wide dispersion. So I made a small waveguide slightly aimed to match left and right off axis angles... smoothly shaped to limit diffraction.
Tweeter is XT25 SC90-04
I had it printed at Shapeways with SLS. Not cheap but better quality and more durable than with home filament printers.
Making a printed back chamber could give you some aiming opportunity.
I used Vifa ring radiators in my door cards, a tweeter not known for wide dispersion. So I made a small waveguide slightly aimed to match left and right off axis angles... smoothly shaped to limit diffraction.
Tweeter is XT25 SC90-04
I had it printed at Shapeways with SLS. Not cheap but better quality and more durable than with home filament printers.
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Aye thanks for the help.... yes I think this is what I want
I went to bed thinking what the others were saying.... woke up , and I was like ... the stevens tweeter has this little lip on it ..... I wonder if... then your post...
Of course that’s it.... yes. That lip is a tiny wave guide. The focal doesn’t have that... I just need to make one.
So there pushed way far back into the dash board (yes a car!) and the focal is shooting HF into the glass...and I can hear it reflect and pull the image. Idk why I didn’t think of that... (which another person gave me half the clues)
So... if this tweeter shape won’t let me put a 1” waveguide and the shape of the tweeter is not round but a bit oval.... so will I make a bigger flare or put it over the hole...
Could I just make a small ring out of acrylic and round all edges and place it around the dome....
That way I can keep the aesthetics. It only needs to narrow the top frequencies
And a back chamber should let it play lower without impedance problems in the crossover.....???
How will the waveguide change the impedance? Will eq fix any subsequent peaks ?
The stevens is hardly generic lol
It’s made by Eric stevens , he designs speakers for a whole bunch of high end manufacturers. His horns are world famous for car audio and they are absolutely stellar drivers , I posted a link to the Facebook page that has specs. Just click read more to see specs
OK, never heard of him, though lost interest in DIY mobile audio after DIYing a [4 chnl], somewhat Quadraphonic full-range system + woofer in my late wife's then brand new 'loaded' '70-1/2 split bumper Camaro SS.
It's performance was so far above what folks were doing at the time, especially after installing a Cadillac VHS tape system later on, that 'we' often paid more attention to the music than the driving to the point where all I was able to salvage was the tape deck and its super rare [I was told after ~giving it away] rear axle/disc brake system; so between our experience and the ongoing obnoxious 'boom-box' cars of today, two good reasons IMNSHO to severely govern the performance of such systems.
Regardless, without any useful info to answer your question [T/S specs, response plots with off axis measurements and/or polars], no way but to assume a generic ~1" mobile audio dome tweeter and now knowing its app/location, my 'knee - jerk' WG response was the most correct solution. ;)
I imagine you probably had some passive time alignment using hundreds of resistors amd caps and coils (lol) :-p kidding
That sounds like a fun car to do a system in , I would love to have one with under dash horns and some 8s in the kick panels !
Yeah so i put some foam on the glass right above the tweeter and it’s a million times better ...
I think , I’ll actually just leave it now and do a custom mount that recess the entire tweeter into the dash , on axis , so it’s 90deg plane is blocked from glass , I think then it will be just fine ,
I super appreciate everyone’s help and ideas!!!!
It’s sounding really good !!!
No, 1st order two ways physically aligned 'close enough' using a Radio Shack horn + 5.25" 'full-range' driver and yes, the under dash horns were real crowd pleasers, both in its 'strangeness' and especially its 'life-like' presentation that drew them to it.
I would have used 8", but not enough space front or back to keep them close to the offset horns. Front-to-back 'balance' was a pair of 'high' power adjustable pots and the sub's XO was from a magazine [pg 56/62]: https://worldradiohistory.com/Archive-Poptronics/70s/1970/Poptronics-1970-06.pdf
I forget the rest of the components used, an 'all things electronics guru' friend that talked me into doing it found them at the local junkyard, mod/install them.
Cool! Yes, one can work wonders with damping, but assumed blocking the windshield/windows in any way wouldn't be legal.
I would have used 8", but not enough space front or back to keep them close to the offset horns. Front-to-back 'balance' was a pair of 'high' power adjustable pots and the sub's XO was from a magazine [pg 56/62]: https://worldradiohistory.com/Archive-Poptronics/70s/1970/Poptronics-1970-06.pdf
I forget the rest of the components used, an 'all things electronics guru' friend that talked me into doing it found them at the local junkyard, mod/install them.
Cool! Yes, one can work wonders with damping, but assumed blocking the windshield/windows in any way wouldn't be legal.
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