I'm collecting candidates for a 3-way I want to build in the foreseeable future.
The design goal is (real) 93db efficiency (update: had to lower a bit to have more options).
-The tweeter is chosen and is my beloved scan-speak 7100-03 crossed pretty high (from 3k to 5k -I will experiment)
-Bass will be some sort of long folded TL tuned at 25hz to 200hz (absolutely NOT higher than 250hz). There is plenty of suitable drivers so this is not an issue. My current favourite is the 10" scan-speak Discovery.
-The mid is where life is and the doubts too
I decided that will be in closed box, well isolated from the LF.
The crossover between midrange and tweeter should be first order acoustic and the least amount of passive equalization should be used, where possible mechanical filtering.
Minimum impedance should stay well above 6 Ohm, unless the sensivity is so high that I can connect the drivers in series (as it is the case with the PHL).
Update: After some more research I decided to settle with this configuration:
A pair of midrange in MTM, ideal size between 4" and 6,5"
The single 8" option has been discarded.
Drivers marked with * are on paper the most suitable.
Drivers marked with - are decent alternatives.
Cost is limited to about 250€/speaker (since 4 are required).
The very scarce list of candidates so far includes:
6-6.5":
*Acoustic Elegance TD6H-8 (excellent driver 200-4k, a bit inefficient)
-Acoustic Elegance TD6M-8 (slightly less lowend than the H version, same 90dB)
-PHL (1120, successfully used 250-3k; other models???)
-Supravox 165GMF (excellent linearity usable above 5k, possible distortion around 2k)
-Audax 170Z0 (efficient, needs some EQ **NB: discontinued)
P.Audio SN6-100N (usable between 150 and 3,5k) - carbon fiber cone and neo magnet
P.Audio SN6-200F (150-3k) -more traditional paper cone and ferrite magnet
B&C 6MD38-8 (decent to 3.5k, lacking midbass)
18sound 8NMB420 (decent to 3.5k, lacking midbass)
smaller than 6":
*Scan-Speak 12MU/8731T00 (veery nice little driver capable of 200hz-over 5k, bit inefficient ofc)
-ATC 3" dome mid (good 350-5k, lacks low-end)
8":
*Jantzen JA8008 (ok 200 to 4k, smooth, no breakup)
Beyma 8M70v2 (usable up to 5k, good low-end, cheap)
PHL (2440/50, 2460, lack published data, which I'm searching)
The design goal is (real) 93db efficiency (update: had to lower a bit to have more options).
-The tweeter is chosen and is my beloved scan-speak 7100-03 crossed pretty high (from 3k to 5k -I will experiment)
-Bass will be some sort of long folded TL tuned at 25hz to 200hz (absolutely NOT higher than 250hz). There is plenty of suitable drivers so this is not an issue. My current favourite is the 10" scan-speak Discovery.
-The mid is where life is and the doubts too
I decided that will be in closed box, well isolated from the LF.The crossover between midrange and tweeter should be first order acoustic and the least amount of passive equalization should be used, where possible mechanical filtering.
Minimum impedance should stay well above 6 Ohm, unless the sensivity is so high that I can connect the drivers in series (as it is the case with the PHL).
Update: After some more research I decided to settle with this configuration:
A pair of midrange in MTM, ideal size between 4" and 6,5"
The single 8" option has been discarded.
Drivers marked with * are on paper the most suitable.
Drivers marked with - are decent alternatives.
Cost is limited to about 250€/speaker (since 4 are required).
The very scarce list of candidates so far includes:
6-6.5":
*Acoustic Elegance TD6H-8 (excellent driver 200-4k, a bit inefficient)
-Acoustic Elegance TD6M-8 (slightly less lowend than the H version, same 90dB)
-PHL (1120, successfully used 250-3k; other models???)
-Supravox 165GMF (excellent linearity usable above 5k, possible distortion around 2k)
-Audax 170Z0 (efficient, needs some EQ **NB: discontinued)
P.Audio SN6-100N (usable between 150 and 3,5k) - carbon fiber cone and neo magnet
P.Audio SN6-200F (150-3k) -more traditional paper cone and ferrite magnet
B&C 6MD38-8 (decent to 3.5k, lacking midbass)
18sound 8NMB420 (decent to 3.5k, lacking midbass)
smaller than 6":
*Scan-Speak 12MU/8731T00 (veery nice little driver capable of 200hz-over 5k, bit inefficient ofc)
-ATC 3" dome mid (good 350-5k, lacks low-end)
8":
*Jantzen JA8008 (ok 200 to 4k, smooth, no breakup)
Beyma 8M70v2 (usable up to 5k, good low-end, cheap)
PHL (2440/50, 2460, lack published data, which I'm searching)
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Telstar, I think you have a love square here
What do you love more:
~94db/watt efficiency,
OR your Scan-Speak 7100 playing at 3+KHz,
OR good polars and controlled directivity,
OR 1st order Xovers ? ? ?
The current trend in speaker design is to avoid lobing in the polar response, and to have a smooth controlled directivity shape function from bass to treble.
To avoid lobing, the center-to-center distance of ALL speakers operating over the crossover frequency should ideally be less than (wavelength/4) , and at the worst case less than (wavelength/2) . For an M-T-M this wavelength/(4-->2) spacing applies to the M-T and M-M distances. Hence, great M-T-M typically use a low frequency steep slope Xover(~1.4KHz with 3rd or 5th order acoustic slope) and 3"-4"M mounted as close as possible. A small tweeter like the SB29RDNC fits MTM rules, as it can be crossed low and has 0.5mm Xmax.
To use a high'ish efficiency large'ish diameter(7"-8") midrange will also demand a steep slope low Xover frequency small tweeter like the SB28RDNC, or a waveguide to control directivity.
I think you must break your "love square" to have a great speaker. It may even end up as a lower efficiency 4-way to showcase the ScanSpeak 7100.
What do you love more:
~94db/watt efficiency,
OR your Scan-Speak 7100 playing at 3+KHz,
OR good polars and controlled directivity,
OR 1st order Xovers ? ? ?
The current trend in speaker design is to avoid lobing in the polar response, and to have a smooth controlled directivity shape function from bass to treble.
To avoid lobing, the center-to-center distance of ALL speakers operating over the crossover frequency should ideally be less than (wavelength/4) , and at the worst case less than (wavelength/2) . For an M-T-M this wavelength/(4-->2) spacing applies to the M-T and M-M distances. Hence, great M-T-M typically use a low frequency steep slope Xover(~1.4KHz with 3rd or 5th order acoustic slope) and 3"-4"M mounted as close as possible. A small tweeter like the SB29RDNC fits MTM rules, as it can be crossed low and has 0.5mm Xmax.
To use a high'ish efficiency large'ish diameter(7"-8") midrange will also demand a steep slope low Xover frequency small tweeter like the SB28RDNC, or a waveguide to control directivity.
I think you must break your "love square" to have a great speaker. It may even end up as a lower efficiency 4-way to showcase the ScanSpeak 7100.
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Why do you need an 8" or 6" if you are crossing 200 -250 Hz to the bass? 5" drivers should be fine down to 200Hz, and will certainly allow a higher crossover frequency before beaming.
Actually you are going to need some very efficient midbass drivers to get your 95db once you take baffle step into consideration, which I see the beyma and supravox are! However the supravox has an re of 5.5 ohms, and you would need two of them in paralell (taking baffle step into consideration) to get your target of 95db) which would bring you down to less than 3 ohms minimum impedance.... My MTM's have lows of 2.7 ohms at around 200Hz -300 Hz.... and they are nominally 8 ohm drivers with re around 5.6 ohms.
Tony.
Actually you are going to need some very efficient midbass drivers to get your 95db once you take baffle step into consideration, which I see the beyma and supravox are! However the supravox has an re of 5.5 ohms, and you would need two of them in paralell (taking baffle step into consideration) to get your target of 95db) which would bring you down to less than 3 ohms minimum impedance.... My MTM's have lows of 2.7 ohms at around 200Hz -300 Hz.... and they are nominally 8 ohm drivers with re around 5.6 ohms.
Tony.
Because I don't like the sound of small transducers in the midrange, and especially in the midbass. Besides, I didn't find any good 5" driver, none that would go low to 200hz in acoustic suspension or (even worse for LF efficiency) open baffle.
165 GMF SUPRAVOX
Yes, you are right, I didnt consider baffle step yet.
If I choose the Supravox I would connect them in series. In the case of the Beyma 8M70v2 I may go for parallel (3.15 min Re), but I need to run some simulations first. An 8-incher is easier to beam and also more problematic for the polar response. Compromises.
But The 8M70 is VERY tempting due to the low price, and I have had good results with beyma in the past, so I could just try a pair, and if i dont like it move on with a different transducer, like the smaller supravox.
If I get 94dB instead of 95 is still fine, cause that's the efficiency of the tweeter above 2khz, but I cannot trust published specs, which tend to be too optimistic regarding efficiency. AFAIK series connection doesnt add the classic 3db, but would still help the low registers. A hourglass shape for the baffle top part is probably ideal.
And there is also the tempting option of the double tweeter (also in series, which bring Re to a comfy 7,4 ohm) like for instance in Dynaudio confidence speakers
Dynaudio Confidence C4
Dynaudio DDC
but I haven't listened to such configuration. The alternative to keep the Re high is to add a rear-firing second tweeter, which can work if I choose a high XO point. Anyway, I like these speakers to be an easy load and efficient since there will be only 20W class-a to power them.*
*Note: the bass section (25-250hz) will be separately amped and should be a long TL like PMC.
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if you like the array design then you can also look at copying one of these designs.
http://www.pbnaudio.com/
they use mostly all Scan Speak drivers from what I can tell. However, I believe that the majority of them are rated more around 92 db.
http://www.pbnaudio.com/
they use mostly all Scan Speak drivers from what I can tell. However, I believe that the majority of them are rated more around 92 db.
Well stereophile had the EPS rated at 92db. I dont know about the others. and you can see the Illuminator drivers in some of them.
Good luck though, I was trying to go for a similar efficiency in a speaker with a small TMW monitor but have lowered my expectations.
I am going use the ScanSpeak 4" 10F from approx 500hz to 3.5khz and the ScanSpeak 8" 22W to fill in down below and then probably the Seas 22TAF for the tweeter which will be about 87-88 db sensitive. I just couldnt get very high sensitivity with the size requirements I am working with. The only other option would be to go with a 8" Coaxial and another 8" woofer to cross to the coaxial before the midrange driver starts to color the highs too much.
Good luck though, I was trying to go for a similar efficiency in a speaker with a small TMW monitor but have lowered my expectations.
I am going use the ScanSpeak 4" 10F from approx 500hz to 3.5khz and the ScanSpeak 8" 22W to fill in down below and then probably the Seas 22TAF for the tweeter which will be about 87-88 db sensitive. I just couldnt get very high sensitivity with the size requirements I am working with. The only other option would be to go with a 8" Coaxial and another 8" woofer to cross to the coaxial before the midrange driver starts to color the highs too much.
I have tried 8" fr in OB: lacking at the top and at the bottom. I had to raise the crossover point to 300hz with a very steep slope (I guess equal to 48db). In OB at the very least 2x 8" are required, but I think I'll go with closed box this time and pretty slim baffle =high WAF).
A pair of the above cited supravox 6" MTM seems the best option at the moment. Their price is ok too (double of the beyma but still affordable).
A pair of the above cited supravox 6" MTM seems the best option at the moment. Their price is ok too (double of the beyma but still affordable).
On a slim OB, if single 8" starts rolling off at 400Hz, two 8" will start rolling of at 400Hz too. So what is the point?
If you want to cross lover, you either need a bigger baffle or active EQ.
MTM is hard to implement and expensive too.
If you pick a high eff mid, you can do with just one per channel.
In a closed box, single Supravox or PHL 6" should match fine with your tweeter.
If you want to cross lover, you either need a bigger baffle or active EQ.
MTM is hard to implement and expensive too.
If you pick a high eff mid, you can do with just one per channel.
In a closed box, single Supravox or PHL 6" should match fine with your tweeter.
Yes, but two drivers reinforce the emission in all their range, including <400hz, as they have a bit more baffle space, i suppose. I have more margin to play with mechanical filtering.
From my old sims, rolloff was around 350hz, so you are spot on with 400hz for a narrower baffle (25-30cm). But probably I wont go OB this time.
If you know higher efficiency mids, with a NON-rising FR please list them.
PHL maybe, but if i don't see at least the FR, I wont pick one, since they declare only 5-6khz as upper range, which translates in 3k max 1st order filter. PHL drivers do have one advantage, though: they exist in 16Ohm version.
Probably yes, thanks
I have to study about baffle step and whether one or two drivers are better (to my ears).
I'll wait a few weeks for more suggestions.
when looking at the baffle step, plan for a 3-4db reduction in overall efficiency, so to reach your target of 95db efficiency you need 98-99db to start with for the drivers covering the baffle step region (ie your midbass drivers!) If you crossover at your baffle step frequency to your bass drivers you can then level match for the bass. To get a baffle step frequency of 200Hz you are going to need a wide baffle!
The other way to look at it is that all drivers must be 98-99db efficient and you do line level baffle step compensation. This though ups the ante for ALL of the drivers efficiency wise
Depending on the placement of the speakers you may need more or less baffle step compensation, but 3-4db is a good ballpark figure to plan on.
Tony.
The other way to look at it is that all drivers must be 98-99db efficient and you do line level baffle step compensation. This though ups the ante for ALL of the drivers efficiency wise
Depending on the placement of the speakers you may need more or less baffle step compensation, but 3-4db is a good ballpark figure to plan on.
Tony.
Thanks, Tony. This helped.
So I definitely need two 93dB midranges or a 98-99 one.
Therefore PHL 6" which are 98-100db gets back on frontline, but I need to find one driver from their production with satisfactory FR in my used range.
There is also the PHY-HP H21 LB 15 (added to the first post), which is 8" and most suited in OB (0.59 Qts), anyway I'm pretty sure is well over 300€ price, and for OB I fond the need for more cone are = two of them => out of budget.
Bass will be active at line-level, because it's absolutely impossible to find a <=12" with low Fs and high efficiency, the TL will be tuned at 25hz and I want an Fs of around 20hz. My favourite bass drivers atm are the scan-speak Discovery either 10" or 12".
If i wanted to go all passive, bass response would terminate at 35hz in the best case unless i use some 15" pro driver and still it wont go as low as the scanspeak (or a peerless).
I dont want to equalize but maybe a little has to be done either at the bottom or the top of the midrange freq window.
I can accept a 250hz XO, but not a 300hz this time.
If basta! simulates normal baffle step, IIRC about 40cm are required for 250hz.
I second the recommendation for the FST. High efficiency, controlled upper breakup and will work down to 250-300 Hz with a steep xover. It's distortion profile also suits being crossed over high, which is incidentally what B&W designed it for. You will need a notch at 3.5kHz for the one peak/fly in the ointment, but all wider bandwidth/high efficiency drivers are going to require some response shaping if crossed high.
Note that first order electrical crossovers do not often give first order acoustic slopes. Lots of Dynaudio loudspeakers use first order acoustic slopes but often have very complex crossovers in order to achieve them.
Note that first order electrical crossovers do not often give first order acoustic slopes. Lots of Dynaudio loudspeakers use first order acoustic slopes but often have very complex crossovers in order to achieve them.
I correct myself, that would be 45cm, which is a little much for WAF, so probably I have to compensate.
I'll check the 2 drivers recommendations tomorrow.
Thanks
It's pretty good up to 4khz, but I cannot use 90db. I had checked all scan-speak catalogue as first thing since I'm mating their tweeter.
These are already two things that I don't want to do. I hate those peaks in the voice range and a notch would be mandatory. Add that LF response is almost insufficient for even a 2nd order xo at 250hz.
Efficiency data I have to extrapolate from the graph attached above, but it should be at least 97db for making this driver viable for me. I checked cost and I can't buy 2 per speaker.
There are very few wideband that do not require equalization, such as Volt (too inefficient but otherwise perfect for the job) and the 7" EMS that I listed in the first post -it may beam but it's the only full range I know off that is naturally smooth. But it's lacking of spl in the low-end of my used range.
Thanks for this advice. I will commission the XO realization to somebody much more expert than yours truly, once I finalized the drivers and rough shape of the speakers.
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