Hi
What kind of tweeter is the best solution for Open Baffle / No Baffle?
1. A dipole tweeter ( open backside AMT or ribon )
2. Two dome tweeter one firing forward and one backward
3. Only one dome tweeter firing forward
If dipole tweeters what to look for?
If dome tweeters same level for back and front? With or without waveguide?
What about the dimensions of the tweeter? ( Wide or narrow?)
Crossover frequency as high or as low as possible?
Best regards Uwe
What kind of tweeter is the best solution for Open Baffle / No Baffle?
1. A dipole tweeter ( open backside AMT or ribon )
2. Two dome tweeter one firing forward and one backward
3. Only one dome tweeter firing forward
If dipole tweeters what to look for?
If dome tweeters same level for back and front? With or without waveguide?
What about the dimensions of the tweeter? ( Wide or narrow?)
Crossover frequency as high or as low as possible?
Best regards Uwe
You can also use a small full range driver as a tweeter. Here small means that the diameter is 3" or less. This gives you both front and back radiation.
I can not fully agree with your statement Charlie. First, many paper cone tweeters are closed back, (to limit lower range and to allow easy mounting in the same box as woofer... no need for subenclosure) second, and even if they are open in the back, due to the magnet in the back, the response is significantly different to forward fr response.
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It's no problem that you disagree, however, I think you are using a bit of a broad brush and misconstruing what I had in mind. I should have provided an example, so I will do that now.
One such driver that I am using in a 3-way, 80Hz-20kHz, open-baffle nude system (I have attached a pic for reference) is the Tang-Band W2-800SL:
Tang Band W2-800SL 2" Aluminum/Mg Full Range Speaker Driver
This driver has very good off-axis response up to about 15kHz and extension is to 20kHz or so, depending on how you want to look at the FR curves. This is because the radiating surface is really only about 1.5 inches wide, making more a member of the "tweeter" class than the typical "full range" driver. It's a unique driver in that SPL is relatively high (86-87dB/W) and distortion is relatively low. I cross over to it around 2kHz or so. This is about where it's own baffle peak is located. Once I use EQ to flatten the frequency response curve the result looks like the attached plot. Very, very nice.
Another driver in this vein is the Peerless PMT40N25AL01:
Tymphany PMT Series 40N25AL01 1-1/2" Aluminum Dome Micro Full Range Speaker 4 Ohm
This is a bit smaller with lower SPL/W sensitivity but distortion is very low. It's very affordable, too. I plan to use it in an upcoming OB system.
With regard to rear response not being the same as the front, I'm not a dipole purist. I just want freedom from the box. There is rear radiation, but as you mention is it not exactly the same as the front. I don't find this to be a problem.
Attachments
what about it?
yes, you can achieve the same polarity forward and back, but due to physical separation between the two membranes, off axis response will still be the mess...someone out there measured it...
is it important to have the same polarity? I do not think so, neither Siegfried Linkwitz nor John Krutke think so...
yes, you can achieve the same polarity forward and back, but due to physical separation between the two membranes, off axis response will still be the mess...someone out there measured it...
is it important to have the same polarity? I do not think so, neither Siegfried Linkwitz nor John Krutke think so...
Charlie, those 1.5" fullrange drivers with "relatively high" SPL are in reality pathetically inefficient in comparison to normal tweeters.
That Peerless you mention is 82dB...
Sensitivity85.3 dB 2.83V/1m
Sensitivity81.8 dB 1W/1m
Most planars, ribbons or air foils are well around 93 dB. In my humble opinion, they sound better as a tweeters.
That Peerless you mention is 82dB...
Sensitivity85.3 dB 2.83V/1m
Sensitivity81.8 dB 1W/1m
Most planars, ribbons or air foils are well around 93 dB. In my humble opinion, they sound better as a tweeters.
The Peerless PMT40 is definitely rather weak in terms of sensitivity. I would use this in a system that would go into a small room only. Output would be fine in that case. Keep in mind that it's being used only above the peak in the open baffle response, so I don't need to make up for the usual lower frequency losses.
On the other hand, the Tang Band W2 has sensitivity of around 87dB/W. Again, the way I am using it (above the baffle peak), I don't need to apply boost to flatten the frequency response. By EQ I was referring to flattening the response within the passband. This is just a few dB of EQing here and there.
The Neo3 is a great driver as long as you use it above about 3kHz IIRC. Other planars/ribbons are larger and the off-axis response is too rolled off IMO and I am not a huge fan of them in general. Both the W2 and the PMT40 use an inverted dome that results in pretty good off-axis response. I would not use just any old dynamic full range driver in this application, and even the best ones can't be more than 2-3" diameter or they, too, will have poor off-axis response.
Heil AMT - i.e. the genuine Great Heil? Heil AMT |
quite possibly the "best" wideband ribbon/diaphram driver ever?
not inexpensive, however
BTW, and OT - while as hard as I've tried over the past 50yrs of listening, I've never been a fan of headphones in general
http://esslabsusa.com/headphones/
anyone here have experience with them?
quite possibly the "best" wideband ribbon/diaphram driver ever?
not inexpensive, however
BTW, and OT - while as hard as I've tried over the past 50yrs of listening, I've never been a fan of headphones in general
http://esslabsusa.com/headphones/
anyone here have experience with them?
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one more thing about this phase issue...if back and forward are in opposite polarity, side cancelation happens, which is desirable thing, not throwing sound to the walls, keeping front signal free of early reflections
if your rear and front tweeter are the same polarity, its approaching omnipolar speakers, with too much early reflections
rear signal in dipolar speakers is not a problem when dipole is placed properly far from the wall, rear signal is significantly delayed and rereflected enough not to interfere with first arriving signal
here is where I stop
I partially agree with you - in that I don't think the rear radiation should exactly match the front, especially at higher frequency.
But that being said, I do think that smooth (albeit not constant !) directivity is a goal worth pursuing, especially when you're close to the front wall (<1m). Small fullranges (I use Visaton FRS8) typically drop like a bomb at the rear around 2kHz or so due to magnet size. That is anything but smooth directivity variation and is audible in terms of tonal balance - and the reason I use a dipole tweeter (Neo3).
I have used backside tweeters before getting a Neo3PDR. Backside tweeter is always more or less out of phase with the frontside. This leads to measurable differences in widely off-axis radiation, but it is very hard to hear any difference.
The benefit of two tweeters is that it is possible to attenuate the rearside one.
The benefit of two tweeters is that it is possible to attenuate the rearside one.
You can also attenuate a planar tweeter at the back by using a sheet of felt or other absorbing material. That's what I do. Works very well with the bonus of higher frequencies being attenuated slightly more.
Sounds reasonable. When I was running OB I was reluctant to do the tweeter thing. I notice Juhazi doesn't think it makes much difference.
When I decided to move to controlled directivity I couldn't reconcile where or how the dipole portion (assuming midrange) would fit into this picture.. both due to pattern and phase. Even if the rear wave is sufficiently delayed to make it separate the power response may be left wanting especially with a narrow tweeter.
^"I notice Juhazi doesn't think it makes much difference."
That was about double tweeters. I like the sound of Neo3PDR a lot more than pairs. I don't attenuate the rearside radiation now, this sounds fine in my room and to my old ears!
The difference of these modifications is easily seen in spl decay measurements (or csd if you like, with long window). Decay correlates well to what I hear/sense, even when on-axis is set to same curve!
That was about double tweeters. I like the sound of Neo3PDR a lot more than pairs. I don't attenuate the rearside radiation now, this sounds fine in my room and to my old ears!
The difference of these modifications is easily seen in spl decay measurements (or csd if you like, with long window). Decay correlates well to what I hear/sense, even when on-axis is set to same curve!
Beyma TPL 150 AMT , with back plate removed.On paar ,if not better ,than the Great Heil.
quite expensive, however
Well, assuming the 150H would be most directly comparable, the $480 USD price listed on usspeaker.com is 50% higher than the ESS Heils .
I wonder though, if the dipole pattern / waveguide action of the Heil might not have some advantages in some OB application?
I've not heard the Beymas, but have done a couple of builds with the Heils, and anything on the same or higher level of performance is quite a feat.
I wonder though, if the dipole pattern / waveguide action of the Heil might not have some advantages in some OB application?
I've not heard the Beymas, but have done a couple of builds with the Heils, and anything on the same or higher level of performance is quite a feat.
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