.564 inches or millimeters? 😀 From what I'd seen of this driver before (with respect to linearity), it's not a driver I'd ever suggest (..but perhaps this is a vastly improved model?).
Considering the way the HiVi is loaded, and operation between 600 and 4kHz, as long as the high-pass for the driver is decent distortion should be low. It's a 2 inch 5 ohm driver. Remember - this isn't open baffle here. 😉 Parallel the drivers to 2.5 ohm and then add some resistance to meet the 4 ohm Neo 3 PDR open baffle (which is lower in eff.) - net result should be close.
Inches 😛
You know, there is another big benfit from using the HiVi back to back - the rearward radiation would be an exact copy of the forward radiation, something you don't find with a 'normal' 8' OB driver. It might be a major boon! Any idea if the flange is removable?
WRT the Neo3 sensitivity, I measured it yesterday, and found something interesting. I applied a 2.83Vpp 3000Hz sine wave, and at 1 meter, measured exactly 93dBSPL - but I think the normal sensitivity specification of XXdBSPL/2.83V/1m refers to 2.83Vrms - which would make the Neo3 96dB/2.83V/1m at 3000Hz, with NO baffles. Is that true about the 2.83V being a rms value? If so, its another reason to love the Neo3!
You know, there is another big benfit from using the HiVi back to back - the rearward radiation would be an exact copy of the forward radiation, something you don't find with a 'normal' 8' OB driver. It might be a major boon! Any idea if the flange is removable?
WRT the Neo3 sensitivity, I measured it yesterday, and found something interesting. I applied a 2.83Vpp 3000Hz sine wave, and at 1 meter, measured exactly 93dBSPL - but I think the normal sensitivity specification of XXdBSPL/2.83V/1m refers to 2.83Vrms - which would make the Neo3 96dB/2.83V/1m at 3000Hz, with NO baffles. Is that true about the 2.83V being a rms value? If so, its another reason to love the Neo3!
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93db? That's not the PDR version.. Open baffle the PDR should be hitting about 88 db at 3kHz. As to the eff. of the standard Neo 3 - don't know.
Btw, half inch in excursion ='s more than 13mm (..and I don't believe that - even peak-to-peak).
Sorry, I'm confusing things. I'm sure the Galaxy fellow meant mm.
And the Neo3 I'm using is the PDRW. If I'm doing my measurements wrong, I'd love to know how to do them correctly!
And the Neo3 I'm using is the PDRW. If I'm doing my measurements wrong, I'd love to know how to do them correctly!
Hi cuibono,
Thanks for the explanation of the off axis response things. However I have some other different POV on this.
First of all, I think the major differences are our system design goals. That leads everything else.
I've (also) played with some OB speakers. One of them had an 8" midrange (modified from a fullranger) + 8" plastic horn for HF and a 18" woofer:
(some more close-ups were posted here:
http://www.diyaudio.com/forums/showpost.php?p=1690331&postcount=32 )
This system had a very good tonal balance and very wide coverage (thanks to the HF waveguide). I could hear the sounds very clearly from 'the other' channel when standing just in front of 'this side'. The tonal balance, sound field and images were very stable across a wide area -- wider than the seating area. Overall this speaker had a very pleasing sound.
But of course it's not perfect (for me). I missed the dynamics, weight, and clarity of my previous big midhorns. I couldn't bring them back at that time (space limitation), so I used a bigger and much louder midrange instead. (The previously mentioned 8" mid was the bottle neck of the system, which had the lowest effeciency in the system.)
Here it is:
http://www.diyaudio.com/forums/showpost.php?p=1729031&postcount=515
(just cut a bigger hole on the previous baffle and stuffed in a modified 12" guitar driver)
A 12" mid (for home use) is somewhat outrageous, let alone an inherently distorting 'guitar driver', but I did like it very much (after the mods), more so than the previous 8 incher. Of course it's not perfect, either. Still ragged response, beaming... etc. you name it. The overall coverage of this system was not so consistent as the previous one. But even so, the sound field and imaging quality were actually still reasonable and acceptable, just within a smaller area. That's fine with me, because I don't need a perfect sound everywhere when I'm not in the main seating area.
On the other hand, the big midrange had its strong point very obvious. The adventage in dynamics were not only in loud passages, but also in the quiet. This makes the music more focused and touchable. I don't have to pay attentions, the details in the sounds grab me positively. By comparison, I had to grab the little sounds myself from the previous 8"er, they didn't come to me. Oh, I mean the quality of sounds, not the fore/aft of images. (English is not my native language, I hope you can understand me.)
When a proper toe in angle is applied, narrower directivity actually helps! When not in the center, you can hear more sound from the far side and less from the near, thus center images and the whole sound field are stable, also the tonal balance.
So, why wide directivity is needed? It's not good for off-center listening positions and unnecessary at the sweet spot. As to those not-beaming small drivers, oh well, ok, I'm bias against them.
As above, 12" midrange is somewhat outrageous and indeed bad directivity in its upper range. 8" would be a very good size as a whole. Smaller than 6.5", I'd guess the lost would be bigger than the gain, especially in an OB.
And no, I'm not a SPL guy. I listen very quietly, usually in conversation level only.
Just my 2c.
🙂
Thanks for the explanation of the off axis response things. However I have some other different POV on this.
First of all, I think the major differences are our system design goals. That leads everything else.
I've (also) played with some OB speakers. One of them had an 8" midrange (modified from a fullranger) + 8" plastic horn for HF and a 18" woofer:
(some more close-ups were posted here:
http://www.diyaudio.com/forums/showpost.php?p=1690331&postcount=32 )
This system had a very good tonal balance and very wide coverage (thanks to the HF waveguide). I could hear the sounds very clearly from 'the other' channel when standing just in front of 'this side'. The tonal balance, sound field and images were very stable across a wide area -- wider than the seating area. Overall this speaker had a very pleasing sound.
But of course it's not perfect (for me). I missed the dynamics, weight, and clarity of my previous big midhorns. I couldn't bring them back at that time (space limitation), so I used a bigger and much louder midrange instead. (The previously mentioned 8" mid was the bottle neck of the system, which had the lowest effeciency in the system.)
Here it is:
http://www.diyaudio.com/forums/showpost.php?p=1729031&postcount=515
(just cut a bigger hole on the previous baffle and stuffed in a modified 12" guitar driver)
A 12" mid (for home use) is somewhat outrageous, let alone an inherently distorting 'guitar driver', but I did like it very much (after the mods), more so than the previous 8 incher. Of course it's not perfect, either. Still ragged response, beaming... etc. you name it. The overall coverage of this system was not so consistent as the previous one. But even so, the sound field and imaging quality were actually still reasonable and acceptable, just within a smaller area. That's fine with me, because I don't need a perfect sound everywhere when I'm not in the main seating area.
On the other hand, the big midrange had its strong point very obvious. The adventage in dynamics were not only in loud passages, but also in the quiet. This makes the music more focused and touchable. I don't have to pay attentions, the details in the sounds grab me positively. By comparison, I had to grab the little sounds myself from the previous 8"er, they didn't come to me. Oh, I mean the quality of sounds, not the fore/aft of images. (English is not my native language, I hope you can understand me.)
When a proper toe in angle is applied, narrower directivity actually helps! When not in the center, you can hear more sound from the far side and less from the near, thus center images and the whole sound field are stable, also the tonal balance.
So, why wide directivity is needed? It's not good for off-center listening positions and unnecessary at the sweet spot. As to those not-beaming small drivers, oh well, ok, I'm bias against them.
As above, 12" midrange is somewhat outrageous and indeed bad directivity in its upper range. 8" would be a very good size as a whole. Smaller than 6.5", I'd guess the lost would be bigger than the gain, especially in an OB.
And no, I'm not a SPL guy. I listen very quietly, usually in conversation level only.
Just my 2c.
🙂
It doesn't have a lot of Xmax, but for the intended BW/peak SPL it has enough if the two I messed with awhile back are typical. I've no experience with earlier ones, but IIRC others were horn loading them with open back chambers due to a Qts >1.0 plus it had a stepped response for mating to short horns in stage monitors, so would indeed be a poor choice for OB.
GM
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Looking again at the sims, this driver may have enough volume displacement for loud listening if used from 700Hz. It will be the HD profile that makes or breaks it. But thanks for recommending it, it is an interesting driver - I don't know how I missed it at PE. Its cheap enough to buy one and find out.
CLS, thanks for the nice post! Your speakers look interesting, and I can tell we are both making an "audio journey". Someday I will try horns, but for right now I want to take OB as far as possible. Dynamics are something I'm concerned with, and require special attention with OB's. Thanks for you input!
I'm interested in the smoothest directivity because I find it benefits tonality, both at the listening position, and in the rest of the room. Also, I am a SPL guy - I record acoustic and amplified music, and my primary goal it recreating a listening experience as close to the original as possible - listening loud is the best! (but not for your neighbors friendship..)
I'm very interested in doing my measurements right - please let me know where I'm going wrong if I am. I'll try and detail how I measuered the Neo3 PDRW's dBSPL at 3000Hz.
1) Using a computer as a generator, I get a 3000Hz sine wave. This goes into the preamp, then power amp, and of course Neo3.
2) Using my Tek scope, I adjust the preamp gain to get 2.8V peak to peak across the drivers terminals (please see note below about this voltage).
3) I set my calibrated WM-61a electret test mic at 1m from the driver. The mic has an integrated preamp, and has been measured to have an output of 199.2mV/Pa.
4) I measure the peak to peak voltage at the output of the mic preamp. I then plug this into the equation dBSPL = 94 + 20log(mV/199.2)
Pretty straightforward huh?
The note about #2 - my guess is that sensitivity specified as XXdBSPL/2.83V/1m is using 2.83Vrms, not 2.83Vpp, like I do in step #2. If I used the Vrms value (which would be 4Vpp), I would get a final dBSPL of 3dB higher compared to 2.83Vpp.
So doing this, I got 96dBSPL/2.83Vrms/1m at 3000Hz with no baffle. Too good to be true?
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Fair enough.
If "the smoothest directivity" is the main goal, how about WG for 1kHz and up + cardioid below? I think that combination will give you the SPL much more easily than full dipole.
I've read some remarkable measurements in that mega WG thread and the significant cardioid works by MBK here somewhere....
If "the smoothest directivity" is the main goal, how about WG for 1kHz and up + cardioid below? I think that combination will give you the SPL much more easily than full dipole.
I've read some remarkable measurements in that mega WG thread and the significant cardioid works by MBK here somewhere....
Hi,
I like the idea of a 4-way to minimise driver beaming. But then the problem is the dipole peak will not be optimised. Let's take 8" along with 4" as example. Crossed at 400Hz the 8" response is fine, but the 4" will be uneven due to the baffle width. Unless the baffle shape narrows (a triangular baffle?)
re: waveguide, I think the problem will be the change of polar response, being dipole at lower frequency and forward directional upwards. The brain do not accept this and the auditory scene may not be trustworthy according to the brain. Unless there are 2 waveguide back-to-back perhaps. I have tried using 10" waveguide (forward only) and the sound scene peculiarity is immediate, although timbre etc. may be correct. Just like using single tweeter.
I like the idea of a 4-way to minimise driver beaming. But then the problem is the dipole peak will not be optimised. Let's take 8" along with 4" as example. Crossed at 400Hz the 8" response is fine, but the 4" will be uneven due to the baffle width. Unless the baffle shape narrows (a triangular baffle?)
re: waveguide, I think the problem will be the change of polar response, being dipole at lower frequency and forward directional upwards. The brain do not accept this and the auditory scene may not be trustworthy according to the brain. Unless there are 2 waveguide back-to-back perhaps. I have tried using 10" waveguide (forward only) and the sound scene peculiarity is immediate, although timbre etc. may be correct. Just like using single tweeter.
I'm not the one to ask for this info.. sorry. 😱
Its been several *years* now that I've had good measurement capability. For me it was just a matter of learning the software and keeping reflections 2 meters away. I never did discreet freq. measurements with the system - always a "swept" signal that started from what ever low freq. I wanted (often 500 Hz) and up to 20 kHz. (..the sonic equivalent of an ear-cleaner.)
Though I'm not certain - Parts Express has them listed as 90 db average WITH a closed back. This is spot-on with Zaph's measurement of the PDR.
Also:
http://www.audiocircle.com/index.php?PHPSESSID=1p2p0grg5irdaamamrmcfcnardld07as&topic=36426.20
I'm very poor in describing audio terms, the best I could explain is there is a missing chunk of frequency. Although measures flat and the timbre is correct. The best way to demonstrate this is to use back-to-back tweeters, then turning off the rear one on and off. Once identified it is easily identified in all types of non-uniform polar response speakers, boxed ones included.
SL's best explanation is that this is psychoacoustics. The brain will ignore rear reflection if the spectrum is the same, but not when some spectrum is missing.
I use completely separate baffles, each of a size specifically tailored to put the peak above the pass band. It also makes aligning the acoustic centers easy.
I think this is the basis of power response - and this is also why I'm going to lengths to get as regular a response off axis as possible. Sound emanates from a loudspeaker at all directions, and then become reflections that our ear/brain integrate for a substantial period of time. If the reflected sounds don't have the same spectral balance as the original direct sound, things starts sounding 'unusual'. I'm trying to avoid that. As far as I know, it is impossible for a box speaker to have the same off axis frequency response (albeit lower SPL) as on axis (say, from 50 to 10kHz). This is possible for omnis and dipoles, although not easy.
Hmmm....
Looks like the situation in my recent system is in the worst. WG'ed tweeter + semi-open back midhorn + dipole bass. :lol: Oh, well....
When just setup, the midhorn was open back, so a major part of the whole spectrum was dipole (sort of, back wave of the midhorn is relatively much weaker... ). But I remember the midrange sound was awfully smeared - vocals were all over the place, almost covering the whole wall. Then it got much better when I covered the back with felt.
Maybe some more experiments this weekend...
Looks like the situation in my recent system is in the worst. WG'ed tweeter + semi-open back midhorn + dipole bass. :lol: Oh, well....
When just setup, the midhorn was open back, so a major part of the whole spectrum was dipole (sort of, back wave of the midhorn is relatively much weaker... ). But I remember the midrange sound was awfully smeared - vocals were all over the place, almost covering the whole wall. Then it got much better when I covered the back with felt.
Maybe some more experiments this weekend...
I'm using an 18sound 6ND430 on an open-baffle with good results.
Xmax +/- 5 mm.
Can be used lower than you need.
Efficiency in your band is about 92 dB if I remember correctly.
David
Xmax +/- 5 mm.
Can be used lower than you need.
Efficiency in your band is about 92 dB if I remember correctly.
David
I don't know enough about cardoid, but I'd guess it is difficult to get it regular over a large range.
I'm interested in pro drivers, I just wish they were closer to $50 rather than $150. Anyone know of sub-$100, 95dBspl 6" pro drivers with at least 1.5mm Xmax and well behaved distortion? How does the Alpha6a do loud? I'm sure there have been a few threads about this around here, I just can't find them.
If I read correctly, cardioid is actually the ideal speakers. Unfortunately true cardioid is difficult (impossible) to build due to different acoustic behaviour at different frequencies?
Seems like Dipole and omni are the path of least resistance to have a uniform radiator?
Seems like Dipole and omni are the path of least resistance to have a uniform radiator?
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