Open Source Monkey Box


The Eminence Delta PRO 12-450A, needs large volume for a B4 alignment, because of its large Vas. Sensitivity of 99 dB half space is super.

More interesting is the Eminence Impero 12-A.
In 70 L cabinet and tuned at 48 Hz, F3 = 45 Hz. Sensitivity is 95.6 dB half space.
B4 alignment not met, a little more resonant, ripple +/- 0.5 dB.
With some source resistance added to the system (0.4E), the SPL becomes more and more flat and F3 lower too, around 43 Hz.
I like this driver for its very low mechanical losses, Qms = 13.81 !!
Its Mms is 83 gram, so it's a strong one, bass guitar driver.
 
The Eminence Delta PRO 12-450A, needs large volume for a B4 alignment, because of its large Vas. Sensitivity of 99 dB half space is super.

More interesting is the Eminence Impero 12-A.
In 70 L cabinet and tuned at 48 Hz, F3 = 45 Hz. Sensitivity is 95.6 dB half space.
B4 alignment not met, a little more resonant, ripple +/- 0.5 dB.
With some source resistance added to the system (0.4E), the SPL becomes more and more flat and F3 lower too, around 43 Hz.
I like this driver for its very low mechanical losses, Qms = 13.81 !!
Its Mms is 83 gram, so it's a strong one, bass guitar driver.

Is this woofer still available?
Edit: never mind found it.
 
I updated the list of woofer candidates at the end of the first post (you may need to scroll down).

I also did a quick AJ Horn simulation using the manufacturer specs (bass reflex, flat response into half space, ignoring amplifier output impedance and DC resistance of x-over parts). Please don't consider these simulations as the final answers on how to tune those drivers; they are just intended to serve as a basis to compare the drivers relative to each other in terms of their suitability for the Monkey Coffin.

I also listed the Qms, Xmax and Le parameters that are not directly related to the box tuning, but are still interesting indicators about the performance of the driver (high Qms means low mechanical losses, high Xmax means the driver can do loud bass without loosing countenance, and low Le may suggest lower motor-induced distortion).

Please suggest any additional driver candidates we have not yet discussed (or remind me of those that are missing in the list). While the general trend is towards a 12" wofer, I'd be especially interested in 10" drivers, too. Once the list is "complete", we can discuss and rank the various options.
 
I updated the list of woofer candidates at the end of the first post (you may need to scroll down).

Some of the woofers in the list are not suitable for this application, because of a Le which is too high to operate up to a few hundred Hz. Especially with a 3 inch midrange option in mind.
For example the Eminence Impero 12A has too much SPL fall off above 200 Hz.
To have a correct view on this aspect it is better to make a TSP model of the driver and evaluate that one. Sometimes you don't know how the SPL in the data sheet is measured. I will do that soon for the most interesting woofers.

Another point, IMO it looks interesting to do already a study of a complete speaker. That means three drivers in a monkey cabinet with X-over, modelling and simulating.
It gives a lot of information already like SPL, impedance, power, excursion, SPL max, required amplifier power at maximum excursion, off axis responses.
I thougth that it might be interesting to compare also a 3 inch midrange concept with a 6.5 inch one in such study.
It will give us a better view on X-over cost too. Afterwards we can design different types of X-over w.r.t. cost and choosing different drivers also.

Maybe some feedback first before giving more details about such study.

Already this, I have in mind for the study:
Woofer Faital PRO PR 320, midrange Volt VM752 or Acoustic Elegance TD6M and tweeter SB Satori Be TW29BN in a monkey cabinet W x H x D = 38 x 75 x 42 cm and LR4 X-over.

As an information:
Faital Pro PR320
Cabinet = 75 L and tuned at 42 Hz, F3 = 45 Hz and sensitivity = 97 dB half space
Qms=7.8, Xmax=±7.37 mm, Le=0.67 mH
IMO, the most interesting one out of the list at this moment. Not looked to the price yet.
 
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Some of the woofers in the list are not suitable for this application, because of a Le which is too high to operate up to a few hundred Hz. Especially with a 3 inch midrange option in mind.

That's a good point. Please note that I just copied most of the Le values in the list from the datasheets, and I honestly don't know how different manufacturers determine their Le values. For those drivers that did not have an Le value in their datasheets I estimated the Le value from the impedance curve (Z value at 1 kHz), and using Z² = Rdc² + (2pi x f x Le)² with f=1000 Hz. I am pretty sure the different values in my list should not all be compared directly. It would be much better to do proper simulations using the 1kHz and 10kHz impedance values (this is what AJ Horn does, and most drivers I looked at seemed to do okay; but I did not look at this very carfully yet). I would be surprised if many of those drivers would fail to go up to 500 Hz or so, because most of them are advertised as bass/mid drivers. In any case, I wouldn't ditch any of these drivers just from their listed Le value without looking at the actual impedance curves.

To have a correct view on this aspect it is better to make a TSP model of the driver and evaluate that one. Sometimes you don't know how the SPL in the data sheet is measured. I will do that soon for the most interesting woofers.

Yay! Looking forward to this!

Another point, IMO it looks interesting to do already a study of a complete speaker. That means three drivers in a monkey cabinet with X-over, modelling and simulating.
It gives a lot of information already like SPL, impedance, power, excursion, SPL max, required amplifier power at maximum excursion, off axis responses.
I thougth that it might be interesting to compare also a 3 inch midrange concept with a 6.5 inch one in such study.
It will give us a better view on X-over cost too. Afterwards we can design different types of X-over w.r.t. cost and choosing different drivers also.

Maybe some feedback first before giving more details about such study.

Yes, an "early model" will be useful to establish a common understanding of what we're doing, and it will show us where we're going wrong.

Already this, I have in mind for the study:
Woofer Faital PRO PR 320, midrange Volt VM752 or Acoustic Elegance TD6M and tweeter SB Satori Be TW29BN in a monkey cabinet W x H x D = 38 x 75 x 42 cm and LR4 X-over.

As an information:
Faital Pro PR320
Cabinet = 75 L and tuned at 42 Hz, F3 = 45 Hz and sensitivity = 97 dB half space
Qms=7.8, Xmax=±7.37 mm, Le=0.67 mH
IMO, the most interesting one out of the list at this moment. Not looked to the price yet.

This is all very much in line with my view, except that I am not a fan of steep filters. I agree about the Faital PR320. Within the 12" camp, the D.A.S. 12P also looks very good to me (higher Qms), and the Beyma SM212 is also not bad (but lower Qms). Within the 10" camp, the Beyma SM-110/N looks interesting, and possibly also the Fane Sovereign Pro 10-300SC.
 
The 12PR320 would be fine, and I like the SM212 from Beyma.

And another vote against steep filters. better to have even response and smooth transitions.

I am questioning the availability of the D.A.S.

Edit#57:
IMO the Fane Pro 10-300SC has no place here, will struggle a bit at 40hz below.
 
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This is all very much in line with my view, except that I am not a fan of steep filters. I agree about the Faital PR320. Within the 12" camp, the D.A.S. 12P also looks very good to me (higher Qms), and the Beyma SM212 is also not bad (but lower Qms). Within the 10" camp, the Beyma SM-110/N looks interesting, and possibly also the Fane Sovereign Pro 10-300SC.

The D.A.S. 12P Le is higher than the one of the Faital PR320, therefore I preferred the Faital more. But I will make TSP models of both to compare the mid frequency SPL.
Beyma SM212 is ok, but indeed Qms is lower. I also prefer high Qms.
I can start some study with one of these three to start with and afterwards driver types can always be modified.

Steep x-over yes or no, let's discuss that later, I am already at 5th order elliptical :).
 
The 12PR320 would be fine, and I like the SM212 from Beyma.

And another vote against steep filters. better to have even response and smooth transitions.

I am questioning the availability of the D.A.S.

I already sent an email to D.A.S. Audio asking for availability. There are also a few webshops that seem to sell it. For example:
DAS AUDIO 12P - Sonidos Online
Haut-parleur DAS 12P, 8 ohm, 320 mm

IMO the Fane Pro 10-300SC has no place here, will struggle a bit at 40hz below.

Why do you think so? I guess it's one of the better options in the 10" camp, but maybe I am missing something.
 
The D.A.S. 12P Le is higher than the one of the Faital PR320, therefore I preferred the Faital more.

Ok, here's a quick comparison using AJ Horn (black is the Faital 12PR320, red is the D.A.S. 12P). Box tuning as given in the list of the first post. AJ Horn models the effect of the voice coil impedance using the impedance values at 1kHz and 10kHz (taken from the curve charts). I'd say forget about the Le spec values. The D.A.S. actually seems to extend a bit higher than the Faital...
 

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  • faital_12PR320_DAS_12P.png
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Then you see it's out of spec, less than 92dbw/45hz.

Edit:
I seriously doubt you'll hear any 40-45hz sounds at all from that design, such a sharp roll off often has the by-product of lots of phase issues at port resonance, efficiently nulling sounds under a certain point. Even if you can measure the sound, I doubt you'll hear much of it. I doubt there's much sound anyone can hear under 47hz looking at that response chart.

Edit2:
Or maybe it's me who misunderstood, I thought we where going for 45hz 92dbw or more. If the goal is something different please tell me.
 
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Agreed, the Fane does not really go beyond 45Hz at the level we want. It's just one of the better 10" options in the list.

In my list I tuned all drivers+boxes to such a sharp roll of. As I wrote before, I am not saying these are the best ways to tune. These sims are just to compare the drivers with each other.

What exactly is the "good/bad" criterion related to phase shift? Is it the max. value of the group delay? Or is it how smooth/sharp group delay changes with frequency?