What are the advantages and disadvantages of these different size drivers? If a 1.4" driver with a 3" voice coil falls in the middle of the 1" & 2" shouldn't it have the best of both worlds? Do smaller throat drivers image better? Do the higher frequency's break up sooner on 4" voice coils than on 1.75 voice coils. What are some of the best modern drivers for home hifi?
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Completely dependent on what horns you are using and how many channels (ways). Horns are very much bandpass devices.
In the right horn you could probably manage with a single 1.4"/1.5" covering the midrange and highs and a 15" below. With a 2", you would probably be looking for a tweeter solution pretty quick.
A single 1" will do you no good except for sole highs with at least two cone drivers below in my opinion. I have never heard an econowave with a 12" plus 1" in a Seos, but to me it seems that both the 12" and 1" are stretched too far.
It's hard to claim what's best, because you have to look at driver/horn combinations.
My preference is modern JBL 1.5" drivers for their price/quality/performance, but it all depends on choice of horn, how large you want to go, and how complex of a system you are willing to tackle.
In the right horn you could probably manage with a single 1.4"/1.5" covering the midrange and highs and a 15" below. With a 2", you would probably be looking for a tweeter solution pretty quick.
A single 1" will do you no good except for sole highs with at least two cone drivers below in my opinion. I have never heard an econowave with a 12" plus 1" in a Seos, but to me it seems that both the 12" and 1" are stretched too far.
It's hard to claim what's best, because you have to look at driver/horn combinations.
My preference is modern JBL 1.5" drivers for their price/quality/performance, but it all depends on choice of horn, how large you want to go, and how complex of a system you are willing to tackle.
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1) One disadvantage large diaphragm drivers is cost-larger drivers use more materials and are more expensive.
All high frequency compression drivers are limited to roughly the same excursion (about .75 mm one way before the diaphragm hits the phase plug) so large diaphragm drivers have an output advantage-a 3" diaphragm has about 3 dB more output than a 1.75", a 4" about 3 dB more than 3".
2) Yes.
3) No.
4) The break up modes of 4" are at a lower frequency than a 1.75", so the HF is not as "clean". The 4" has about 6 dB more output potential than the 1.75", so will have less distortion at lower frequencies, a trade off.
5)"Best" depends on many factors- crossover frequency and slope, SPL desired, frequency range, how much distortion you are willing to tolerate, are you willing to use equalization, what type of horn used, etc.
In general, the offerings from major manufacturers ( B&C, BMS, EV, JBL, TAD) are all decent, with the more expensive drivers being slightly "better".
In general I'd agree with Johan that using 4" diaphragms "you would probably be looking for a tweeter solution pretty quick", and for home use are a bit overkill unless a crossover lower than 500 Hz is desired.
You can actually listen to a variety of drivers using both dual sine wave tones and music in this thread:
http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html
I am enjoying the JBL 2435 drivers I have in my system, but I also use a super tweeter above ~10k to keep the directivity lower.
I'm not sure what you mean by 'image better'. If you're using horns you're probably going to end up with less spacious / more pinpoint imaging in general. Whether that is better is kind of a personal preference. If you use a driver with a smaller throat, you could use a horn that produced a wider pattern at high frequencies which would push you towards the more spacious end, but it's going to be an incremental thing. If you want very spacious imaging, you'd probably be better off going with a low directivity design, typically the opposite of horns.
I'm not sure what you mean by 'image better'. If you're using horns you're probably going to end up with less spacious / more pinpoint imaging in general. Whether that is better is kind of a personal preference. If you use a driver with a smaller throat, you could use a horn that produced a wider pattern at high frequencies which would push you towards the more spacious end, but it's going to be an incremental thing. If you want very spacious imaging, you'd probably be better off going with a low directivity design, typically the opposite of horns.
The imaging question on different size CDs isn't as clear cut as some lead us to believe. In fact the larger drivers do beam sooner.....significantly so to effect imaging in that there's a mismatch in directivity lower in frequency. What happens above the horn throats diameter is purely a function of the diameter itself........the horn is out of the equation at this point.
So what's output above 12khz is beaming in a 1", 10khz for a 1.4" and so on and so on.
So what's output above 12khz is beaming in a 1", 10khz for a 1.4" and so on and so on.
"In fact the larger drivers do beam sooner"
Depends on how the throat and phase-plug are designed.
Obtain a JBL 2431 or 2435 and examine, the phase-plug is flush with the front of the driver.
The 2432 has a thin spacer to cause a resonance in the top 1/3oct (the others mentioned sound better).
Depends on how the throat and phase-plug are designed.
Obtain a JBL 2431 or 2435 and examine, the phase-plug is flush with the front of the driver.
The 2432 has a thin spacer to cause a resonance in the top 1/3oct (the others mentioned sound better).
It depends on many more factors and on one's priorities...
I'm afraid it is not as simple...
Answers to your questions depend on many other factors, beside throat and voice coil diameter.
Among these:
1) presence or lack of an internal conical throat, and - if present - design thereof:
this contributes to determining the frequency beyond which the driver will 'beam' in pretty much all horns/waveguides (except those with a 'pinched' throat that rely on diffraction to widen the beamwith - but these are IMHO best avoided anyway...);
2) compliance of the surround and size of the back-chamber:
both of these influence the resonance frequency and hence the driver's usable lower frequency range (provided that the horn onto which it is mounted is large enough...)
3) diaphragm material and mass:
these will affect two things:
a) the high frequency mass break point, beyond which the driver requires equalization, which can be either electrical - for 'constant directivity' horns/waveguides - or mechanical - as brought about by 'classical' exponential/hypex/tractrix horns, which lead to some 'beaming' in at least one plane;
b) the frequency beyond which the diaphragm 'breaks up' and is no longer pistonic. This frequency is typically ~12kHz in the 1" exit CDs and ~6kHz in 2" exit CDs... but the exact frequencies vary, and especially in the case of Be-diaphragm CDs can be almost one octave higher.
So, all this considered, there can be no clear-cut answers to your questions.
As an example, a few 'old style' 1" drivers with deep magnets, long and slow-flare internal throats, compliant surrounds and large back-chambers, coupled to conventional exponential horns with a cut-off frequency (Fc) of ~400Hz are perfectly happy when used down to ~800Hz and can mate well with a suitable 15" woofer.
Drivers of this type have become as rare as hen's teeth, however. Examples would be JBL's 2426, Fostex D1400 and TAD TD-2001.
The former two have titanium diaphragms, and this, coupled to the top-octave beaming caused by the long internal throat, means that they are better used as mid-range drivers below ~7-9kHz, with a supertweeter taking over beyond that [*]
The TAD otoh sports a Be diaphragm, and as a results works quite well in two-way systems from 800Hz all the way up to 20kHz - provided you can live with the same kind of beaming beyond ~9kHz.
Most modern 1" drivers, instead, have 'pancake' magnets, short or non-existant internal throats and 'fast-flare' phase plugs, stiff surrounds and vestigial back-chambers.
These are best coupled to waveguides or high-Fc horns and used as tweeters > 1.5kHz.
They don't beam quite as much in the HF, but they can't mate well with large direct-radiating woofers, and ideally require an 8"-10" midrange cone to ensure a smooth directivity match. Also, while their throat geometry minimizes top-octave beaming, in most cases the uppermost frequencies are still produced by the diaphragm working in 'break-up' mode, and will therefore not sound as 'smooth' as a properly designed super-tweeter.
Similar considerations apply to 1.5"-exit and 2"-exit drivers too...
In the end, there is no single 'perfect' solution. Pick your poison and live with the compromises it entails....
[*] for my personal choice of compromises, see: Project | Homebuilt Hi-Fi - A user submitted image showcase of high quality home built hi-fi components.
Marco
I'm afraid it is not as simple...
Answers to your questions depend on many other factors, beside throat and voice coil diameter.
Among these:
1) presence or lack of an internal conical throat, and - if present - design thereof:
this contributes to determining the frequency beyond which the driver will 'beam' in pretty much all horns/waveguides (except those with a 'pinched' throat that rely on diffraction to widen the beamwith - but these are IMHO best avoided anyway...);
2) compliance of the surround and size of the back-chamber:
both of these influence the resonance frequency and hence the driver's usable lower frequency range (provided that the horn onto which it is mounted is large enough...)
3) diaphragm material and mass:
these will affect two things:
a) the high frequency mass break point, beyond which the driver requires equalization, which can be either electrical - for 'constant directivity' horns/waveguides - or mechanical - as brought about by 'classical' exponential/hypex/tractrix horns, which lead to some 'beaming' in at least one plane;
b) the frequency beyond which the diaphragm 'breaks up' and is no longer pistonic. This frequency is typically ~12kHz in the 1" exit CDs and ~6kHz in 2" exit CDs... but the exact frequencies vary, and especially in the case of Be-diaphragm CDs can be almost one octave higher.
So, all this considered, there can be no clear-cut answers to your questions.
As an example, a few 'old style' 1" drivers with deep magnets, long and slow-flare internal throats, compliant surrounds and large back-chambers, coupled to conventional exponential horns with a cut-off frequency (Fc) of ~400Hz are perfectly happy when used down to ~800Hz and can mate well with a suitable 15" woofer.
Drivers of this type have become as rare as hen's teeth, however. Examples would be JBL's 2426, Fostex D1400 and TAD TD-2001.
The former two have titanium diaphragms, and this, coupled to the top-octave beaming caused by the long internal throat, means that they are better used as mid-range drivers below ~7-9kHz, with a supertweeter taking over beyond that [*]
The TAD otoh sports a Be diaphragm, and as a results works quite well in two-way systems from 800Hz all the way up to 20kHz - provided you can live with the same kind of beaming beyond ~9kHz.
Most modern 1" drivers, instead, have 'pancake' magnets, short or non-existant internal throats and 'fast-flare' phase plugs, stiff surrounds and vestigial back-chambers.
These are best coupled to waveguides or high-Fc horns and used as tweeters > 1.5kHz.
They don't beam quite as much in the HF, but they can't mate well with large direct-radiating woofers, and ideally require an 8"-10" midrange cone to ensure a smooth directivity match. Also, while their throat geometry minimizes top-octave beaming, in most cases the uppermost frequencies are still produced by the diaphragm working in 'break-up' mode, and will therefore not sound as 'smooth' as a properly designed super-tweeter.
Similar considerations apply to 1.5"-exit and 2"-exit drivers too...
In the end, there is no single 'perfect' solution. Pick your poison and live with the compromises it entails....
[*] for my personal choice of compromises, see: Project | Homebuilt Hi-Fi - A user submitted image showcase of high quality home built hi-fi components.
Marco
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"Is there any existing 2.5'' or 3'' exit throat ?"
Community EM280 (2.8"), EM282 (2.8"), M4 (4")
"Also, is there any diaphragm bigger than 4'' ? "
Community M4 (7")
All are midrange.
http://www.communitypro.com/sites/default/files/EM280_spec.pdf
Emilar and Renkus Heinz SSD5600, but they are quite scarce.
Community EM280 (2.8"), EM282 (2.8"), M4 (4")
"Also, is there any diaphragm bigger than 4'' ? "
Community M4 (7")
All are midrange.
http://www.communitypro.com/sites/default/files/EM280_spec.pdf
Emilar and Renkus Heinz SSD5600, but they are quite scarce.
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"Add the Adamson M200 and JBL CMCD."
Cone driven horns, not sure where one would want to draw the line here.
"JBL 2490 "
Large throat, but only a 4" coil.
A 2" aluminum diaphragm, a 0.7" throat, on a 4' 100hz horn.
https://www.youtube.com/watch?v=fYhpRlY_EfM
Horrible JBL monitor
https://www.youtube.com/watch?v=wNFK4w9NgoM
Quad 57
https://www.youtube.com/watch?v=wv5D9i7FW2E
Cone driven horns, not sure where one would want to draw the line here.
"JBL 2490 "
Large throat, but only a 4" coil.
A 2" aluminum diaphragm, a 0.7" throat, on a 4' 100hz horn.
https://www.youtube.com/watch?v=fYhpRlY_EfM
Horrible JBL monitor
https://www.youtube.com/watch?v=wNFK4w9NgoM
Quad 57
https://www.youtube.com/watch?v=wv5D9i7FW2E
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