As an exercise at this stage, I am assessing the possibility of designing a big three way system based upon the Volt RV4564 18" Bass unit.
The bass driver will be used in a large reflex cabinet probably around 300 litres, tuned to around resonance. Their datasheet alludes to this possible alignment.
I might even consider a TL, but that might follow as part of the assessment process.
Selection of midrange drivers and tweeters is next.
Crossover will be passive third order as I like these and prefer modelling with them.
Tweeter is likely to be a top Scanspeak or Seas such as the 29TFF/W H1318 or the high end Crescendo T29 or more likely one of the Seas 35mm domes. As a lower cost I like the Audax TW034X0 which is sensitive enough. I already have these. Equalisation as part of the design process or TL loading will mean the tweeters specified will be a fine match.
Now comes to selection of the midrange.
Crossover point will likely be 300 Hz so this might rule out the big Volt dome unit. So likely to consider a cone unit but which one?
Using a third order APC reverse polarity BP filter means one gets back ~2.5 dbs of bandpass gain so this means that cone units of around 90 d/bw would be a fit.
The Seas MCA15RCY H1262 is a possible fit having a smooth response with minimal work required, it can handle a 300 crossover point fine, it works down to 100 Hz.
So now looking for suitable midrange candidates.
Simon
The bass driver will be used in a large reflex cabinet probably around 300 litres, tuned to around resonance. Their datasheet alludes to this possible alignment.
I might even consider a TL, but that might follow as part of the assessment process.
Selection of midrange drivers and tweeters is next.
Crossover will be passive third order as I like these and prefer modelling with them.
Tweeter is likely to be a top Scanspeak or Seas such as the 29TFF/W H1318 or the high end Crescendo T29 or more likely one of the Seas 35mm domes. As a lower cost I like the Audax TW034X0 which is sensitive enough. I already have these. Equalisation as part of the design process or TL loading will mean the tweeters specified will be a fine match.
Now comes to selection of the midrange.
Crossover point will likely be 300 Hz so this might rule out the big Volt dome unit. So likely to consider a cone unit but which one?
Using a third order APC reverse polarity BP filter means one gets back ~2.5 dbs of bandpass gain so this means that cone units of around 90 d/bw would be a fit.
The Seas MCA15RCY H1262 is a possible fit having a smooth response with minimal work required, it can handle a 300 crossover point fine, it works down to 100 Hz.
So now looking for suitable midrange candidates.
Simon
Hi Mate, welcome to the big-3-way universe
I walk a somewhat different concept (active crossover, 4th order Linkwitz Riley) but I already made my speaker selection, maybe it helps you too.
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The Faital mid looks very good on paper and is cheap.
Yepp.. they're 91dB sensi.. which - taken the ~90dB needs - suits this 3-way perfectly I think. SPL response very flat and reviews are very-very good for Faitals, these ones too. Question is if RMS power handling is enough for this application here (depending on xover freq. as well).
If we take 2 in series to distribute power - we stay at 91dB SPL and get to 16 Ohms.
If we take 2 in parallel again to distribute power - we get 97dB SPL and get to 4 Ohms.
(That's why I took 4 in parallel-series, each playing at 25% only while getting to 97dB SPL and staying at 8 Ohms alltogether).
But if the designer says he can stay within it's specs regarding power handling, 1 piece per side should be fine.
To be honest - I searched parts-express for the 'perfect' mids for my system. Main considerations were to be around 91dB SPL each (to try to match the tweeter's 98dB when connected in parallel) and flatness of frequency curve. There'll be enough other parameters like room which will more or less modify this flatness. There're MANY very good mids out there on this site, I checked them ALL (!!) .. also normal ones, also PA ones.. - these are THE BEST (for me).
If we take 2 in series to distribute power - we stay at 91dB SPL and get to 16 Ohms.
If we take 2 in parallel again to distribute power - we get 97dB SPL and get to 4 Ohms.
(That's why I took 4 in parallel-series, each playing at 25% only while getting to 97dB SPL and staying at 8 Ohms alltogether).
But if the designer says he can stay within it's specs regarding power handling, 1 piece per side should be fine.
To be honest - I searched parts-express for the 'perfect' mids for my system. Main considerations were to be around 91dB SPL each (to try to match the tweeter's 98dB when connected in parallel) and flatness of frequency curve. There'll be enough other parameters like room which will more or less modify this flatness. There're MANY very good mids out there on this site, I checked them ALL (!!)
.. also normal ones, also PA ones.. - these are THE BEST (for me).
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I also love fullrange sound, however my musical taste doesn't allow me to use a pair for everything.
To the VOLT: I would rather think about the freq. response. A fancy looking driver with interesting design but no big wonders here: crossing at 300Hz and we're already on the roller coaster long before.. I would consider another kind of 18" monster with a somewhat more flat response into mids.
To the VOLT: I would rather think about the freq. response. A fancy looking driver with interesting design but no big wonders here: crossing at 300Hz and we're already on the roller coaster long before.. I would consider another kind of 18" monster with a somewhat more flat response into mids.
I also love fullrange sound, however my musical taste doesn't allow me to use a pair for everything.
To the VOLT: I would rather think about the freq. response. A fancy looking driver with interesting design but no big wonders here: crossing at 300Hz and we're already on the roller coaster long before.. I would consider another kind of 18" monster with a somewhat more flat response into mids.
Me too. But It might work when taking room gain into account, still it is far from flat.
I would use this one.
FaitalPRO | LF Loudspeakers | 18FH500
Just added my Dayton and an Eminence Omega Pro-18A into WinISD. Adding this Faital too, looks very interesting, let's see how curves look. Also a very nice woofer (I overlooked due to 99dB and I need 96-97 but it gets less anyway.. I give it a try).
Well, taken ALL parameters into account, things get interesting:
- the Daytons are the least linear (being still very linear, just saying)
- the Eminence has the most flat freq. response, beats all 3
- the Faital is pretty-much the same like the Eminence, but maxSPL is calculated and shown 96dB instead of 99 as stated by manufacturer
Dayton - $90
Eminence - $210
Faital - $345
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- the Daytons are the least linear (being still very linear, just saying)
- the Eminence has the most flat freq. response, beats all 3
- the Faital is pretty-much the same like the Eminence, but maxSPL is calculated and shown 96dB instead of 99 as stated by manufacturer
Dayton - $90
Eminence - $210
Faital - $345
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The Dayton looks nice. Strong motor but high Le.
The Eminence is far from flat and has low xmax. also low spl in the bass region.
As for me I don't see Eminence in the same league as Faital.
Well I also checked Faital 18HP1060 now and you can forget it.. at least based on Thiele-Small and WinISD even less linear than the Dayton.
I don't know how the Eminence factory data is measured, they have less SPL on the bottom, I agree. But in WinISD it performs pretty insanely-well in the simulation.
As I change volume, or tuning freq, or both, I simply cannot do that much with the others like with the Eminende Omega PRO-18A. At the end (for me) matters how a driver is performing in a baffle.
*confused now a bit*
I don't know how the Eminence factory data is measured, they have less SPL on the bottom, I agree. But in WinISD it performs pretty insanely-well in the simulation.
As I change volume, or tuning freq, or both, I simply cannot do that much with the others like with the Eminende Omega PRO-18A. At the end (for me) matters how a driver is performing in a baffle.
*confused now a bit*
The 18HP1060 is a great driver.
You need to take both into account.
FR of the enclosure and the FR of the speaker.
In your brain just add both curves together.
And the Eminence will perform far worse than the other 2 in the real world.
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I thought these WinISD curves simulate a speaker with the given drivers when IEC-measured open-air in that config TOGETHER - at least based on numbers.
At the very same volume/tuning freq the the 18HP1060 is doing crazy things compared to all the others. A "peak" (actually back to 0) SPL at 27-28Hz. Better said: a -3dB dip maxing at 45Hz. It needs to be configured differently to produce a more flat response and at the end the room for playing with SPL vs. how deep it goes near-linear is less.
Dayton - red
Eminence - magenta
Faital 18FH500 - black
Faital 18HP1060 - that crazy green
All at 518 liters / 26.46Hz tuned below resonance freqs to extend response, I can live with some (not much but some) flat-dip at around 45Hz. Here the Eminence excels, see selected bold magenta line.
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But it's interesting what you tell these being box resonances only. So what you're saying is that these speakers resonate the box a little differently and I still have to take their free-air resonance according to datasheet into account ? Weird.
At the very same volume/tuning freq the the 18HP1060 is doing crazy things compared to all the others. A "peak" (actually back to 0) SPL at 27-28Hz. Better said: a -3dB dip maxing at 45Hz. It needs to be configured differently to produce a more flat response and at the end the room for playing with SPL vs. how deep it goes near-linear is less.
Dayton - red
Eminence - magenta
Faital 18FH500 - black
Faital 18HP1060 - that crazy green
All at 518 liters / 26.46Hz tuned below resonance freqs to extend response, I can live with some (not much but some) flat-dip at around 45Hz. Here the Eminence excels, see selected bold magenta line.
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But it's interesting what you tell these being box resonances only. So what you're saying is that these speakers resonate the box a little differently and I still have to take their free-air resonance according to datasheet into account ? Weird.
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Of course you need to.
The free air response of the speaker is the baseline so to speak.
Add on top of that the FR of the enclosure and you have the response outdoor in free-field of the speaker in the box.
If ported also take into account port length, cross section and position.
Port in close proximity of the speaker will sound better. The shorter the port the better (more precise) it will sound. Also slot ports sound better. Slot ports shouldn't be smaller than 1 inch in width. I suggest at least 1/3 Sd preferably more (especially for high xmax drivers) for port cross sectional area.
Regarding box volume if it is too big the speaker can't compress the air anymore and the box will be almost useless, power handling will suffer also.
Hmm. WinISD tells: WinISD is a freeware program that allows one to use driver specifications to model how this driver will act in a specific alignment [sealed, ported, passive radiator etc..)] given a certain volume and/or port size. - From this I thought it's already providing me a free-air combined response and no need to look at both datasheet curves and box curves here.
For the port I simply input data and follow the instructions:
Along side the previously listed if you are using a ported alignment the 'Rear Port - Air Velocity' tab will be of importance to you. This will show you how fast the air will be moving into and out of the port. The lower the better. To decrease this number the port surface area must be increased, but as you do this you also decrease the level at which the port resonates. Due to this a balance act must be had where you minimize port air velocity [at its fastest 20-25m/s should be accepted] and keeping first port resonance out of audibility range. If you plan on crossing your subwoofer over at 80Hz with a 4th order crossover [typical of modern receivers] having first port resonance modeled at or above 120Hz is safe an explanation can be found here of why this is 'safe'. There are two reasons why port air speed is important. If it gets too high it will create port chuffing [audible and annoying noise from the port] as well as port compression [there is too much impedance to airflow caused by the port resulting in nonlinear performance at high SPL].
There's also a port geometry study but that's way too complicated to take into account as well. I'll just use nicely rounded ones on both ends. Size will be enough, at least 1/3 Sd when using 1 port, at least 1/4 Sd when using 2 ports.
Box volume - I don't care. The program tells me what to plan and I do it accordingly.
Btw if the Eminence has such a bad slope towards deep freqs according to database, we would have to design a box in WinISD which is compensating this effect with a huge peak in the bass section - so that when my brain adds both curves they compensate eachother out to linear (in theory). But this is not the case: everybody is trying to design boxes with already-linear resonance freq so I assume when a calculation/design/curve is ready by a program or website, we don't need to imagine or add anything: the box and the driver inside together produce what you see in the curves.
For the port I simply input data and follow the instructions:
Along side the previously listed if you are using a ported alignment the 'Rear Port - Air Velocity' tab will be of importance to you. This will show you how fast the air will be moving into and out of the port. The lower the better. To decrease this number the port surface area must be increased, but as you do this you also decrease the level at which the port resonates. Due to this a balance act must be had where you minimize port air velocity [at its fastest 20-25m/s should be accepted] and keeping first port resonance out of audibility range. If you plan on crossing your subwoofer over at 80Hz with a 4th order crossover [typical of modern receivers] having first port resonance modeled at or above 120Hz is safe an explanation can be found here of why this is 'safe'. There are two reasons why port air speed is important. If it gets too high it will create port chuffing [audible and annoying noise from the port] as well as port compression [there is too much impedance to airflow caused by the port resulting in nonlinear performance at high SPL].
There's also a port geometry study but that's way too complicated to take into account as well. I'll just use nicely rounded ones on both ends. Size will be enough, at least 1/3 Sd when using 1 port, at least 1/4 Sd when using 2 ports.
Box volume - I don't care. The program tells me what to plan and I do it accordingly.
Btw if the Eminence has such a bad slope towards deep freqs according to database, we would have to design a box in WinISD which is compensating this effect with a huge peak in the bass section - so that when my brain adds both curves they compensate eachother out to linear (in theory). But this is not the case: everybody is trying to design boxes with already-linear resonance freq so I assume when a calculation/design/curve is ready by a program or website, we don't need to imagine or add anything: the box and the driver inside together produce what you see in the curves.
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^^Negative.
The software does not and can not take the real free air response of the speaker into account which is your baseline for any professional design.
Also in my opinion the Eminence is out of the question for a good design. Xmax is too low. It will distort early and kill itself when pushed hard below 40 Hz.
The software just displays the FR of the enclosure.
And even then if you add box FR and speaker FR and then build your "theoretical perfect" box the result can still be optimized by tweaking here and there. short the port(s) a little. Add damping. Optimize port shape and geometry, etc. But let the ear be the final judge.
A really good (optimal) box takes a lot of time even if you use software.
Software is just some sort of direction or guideline and not the optimum.
Well, there're plenty of measurements combined with the Thiele-Small parameters which help a box designer software calculate how your complete speakers might behave in some aspects - like freq response.
Let's have a look at a very simplified drawing around this theory: if I understand you correctly, I'd need to design a box with a freq response like below, to get a flat result, for a speaker like on the left ? Free air of course.
My baseline is then the manufacturer's datasheet, I look at the measurements, red line. I design my box then accordingly (blue line), taking the 'inverse' of red line 'til flat.. and I should be good overall. Not perfectly, but somehow closer than without the simulation sw. Right ? In theory.
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But noooooo - we don't design complete speakers like on the upper-right sketch to get such a curve.
With all of the others I agree, except with that, what a speaker designer program is showing me (not accurately but it gives a good reference point if I'm shooting at the right direction at all or will completely miss the target).
'Cause you tell me I should consider speaker's own freq. curve and modify the end result with that in my brain. I think it's already done by the software, with the help of Thiele-Small parameters and tons of mathematical equations which come partly from theory and partly from experience. The software is able to assume the drivers own curve indeed, not exactly of course but approximates it from mass, areas, suspension stiffness, etc.... so at the end of the day if I design a speaker with a linear freq response and measure it in the middle of a golf club at 1m giving it 2.83V into 8 Ohms at sea level 20 °C no wind and it's f* quiet, I think I should get more or less (in that you're right, it's not exact) what I planned, a somewhat-linear curve in the region what matters.
At that point if I measure this completed speaker I will definitely NOT add speaker frequency curve once more with my brain 'cause it's included in the box design calculations, that's why I use software to free my brain of the task of an op-amp-like signal combiner
However what I would take into account and would use brain capacity are:
- how far I place the boxes from my walls inside the room, sides, behind
- to estimate/measure/hear how this modifies my overall freq response
- how high I lift them from the ground
- rotating them - or better not ? (horizontal dispersion)
- direct the drivers or better not ? (vertical dispersion - see MTM & other theories)
- crossover types and their effect on SPL, phase, group delay, ringing, soundstage (hell yeah), imaging - Mr. Linkwitz could teach us a lot about these all ..
.
.
.
- weighing all these with a number and adjusting the whole setup beginning with the biggest number
.. kind of giving prios 'cause ALL parameters cannot be adjusted perfect. So back to Eminence: f* expensive. I appreciate your input saying they're crap but this is just 1 opinion. During the next years I might gather some more inputs about these and as the number of samples increase (let's call it "Eminence evaluation sample rate") I might be always a bit closer to a real fact if they're really thaaat bad or not. Until than - a fat "thank you".
Back to the plots:
1. I don't believe all manufacturers measure their speakers and plot their curves the same way
2. I believe they might apply little or even more cosmetics as well so at the end what an enthusiastic DIY-er builds might be a complete mess - or even not. But luck plays a strong factor, especially with environment and everything else in mind.
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