Ok, so my preference would be for sealed as I haven't made many enclosures (about 4 so far, 2 of which have been sealed) and to be honest calculating alignments etc isn't something I've spent much time on, as I love filter design and crossover networks have enough to keep me learning for years anyway... problem is that's only one part of the solution.
A while ago I purchased 5* SB acoustics SB15NRXC30-8 mid woofers.
My original plan was to use these in 5 2 way bookshelves however my situation has changed and I now only listen in stereo, I also now no longer have a subwoofer.
I've been considering buying a pair of sb12mnrx25 midrange units and building these into WWMT floorstanders instead of the sealed TM units I currently have.
So my questions are as follows:
>according to online calculators, these drivers are better ported, can someone explain to me if this is the case - what advantages/disadvantages and reasons there would be to conclude from these calculators, and then should I port the 7ltr 2-way WT enclosures I currently have? tuning is kindly already provided by madisound and fitting a suitably sized port would be easy. I'm very happy with the sound of them sealed but bass response is definately lacking.
>If I used the SB15NRXC in a standard 3-way enclosure I would aim to BSC at xo freq, the crossover models very nicely (though in fairness I'll probably buy a dlcp and go active from now on) however I was really hoping to achive enhanced bass response from two drivers in a sealed enclosure - is this plain wrong, is it possible with a large enough enclosure or will I encounter other problems.... or should I just port it?
If someone who is 'good at these things' could help I'd be so grateful!!
A while ago I purchased 5* SB acoustics SB15NRXC30-8 mid woofers.
My original plan was to use these in 5 2 way bookshelves however my situation has changed and I now only listen in stereo, I also now no longer have a subwoofer.
I've been considering buying a pair of sb12mnrx25 midrange units and building these into WWMT floorstanders instead of the sealed TM units I currently have.
So my questions are as follows:
>according to online calculators, these drivers are better ported, can someone explain to me if this is the case - what advantages/disadvantages and reasons there would be to conclude from these calculators, and then should I port the 7ltr 2-way WT enclosures I currently have? tuning is kindly already provided by madisound and fitting a suitably sized port would be easy. I'm very happy with the sound of them sealed but bass response is definately lacking.
>If I used the SB15NRXC in a standard 3-way enclosure I would aim to BSC at xo freq, the crossover models very nicely (though in fairness I'll probably buy a dlcp and go active from now on) however I was really hoping to achive enhanced bass response from two drivers in a sealed enclosure - is this plain wrong, is it possible with a large enough enclosure or will I encounter other problems.... or should I just port it?
If someone who is 'good at these things' could help I'd be so grateful!!
You won't get that. For lower bass, you'll need a ported box of 10L ~ 12L. From modeling, F3 is 50Hz.
Since you have 5 units, you may want to consider a 2.5 design. When done right, it'll beat a 2-way.
Regards
Mike
Hi mike,
was what I was suspecting
I did consider 2.5 way (WTW or WWT) but decided in the end I'd prefer the phase alignment of a 3-way. Plus going 3 way allows me to account for baffle step with the enhanced effieciency of the parallel woofers, remove the L-pads from the tweeter, use relatively cheap inductors, achieve a nearly perfectly flat impedance (5 to 6 ohms throughout, excluding woofer resonance imp) and very flat FR with no peaks... so most of my design goals for the crossover/baffle side of things, just wasn't sure of ported alignment. The cabinet would likely be about 30L though... I could of course fill the bottom with ballast if that can't be tuned nicely.
was what I was suspecting
I did consider 2.5 way (WTW or WWT) but decided in the end I'd prefer the phase alignment of a 3-way. Plus going 3 way allows me to account for baffle step with the enhanced effieciency of the parallel woofers, remove the L-pads from the tweeter, use relatively cheap inductors, achieve a nearly perfectly flat impedance (5 to 6 ohms throughout, excluding woofer resonance imp) and very flat FR with no peaks... so most of my design goals for the crossover/baffle side of things, just wasn't sure of ported alignment. The cabinet would likely be about 30L though... I could of course fill the bottom with ballast if that can't be tuned nicely.
IMHO a 5" midwoofer mates easily with a tweeter, adding a dedicated mid for a true 3 way design will only complicate it, adding unnecessary expenses (big coils and caps). It is doable however. If you opted for a 6.5" or larger midwoofer then things change drastically.
If your idea is to low pass the "woofer" at the baffle step frequency, to low pass the mid (not band pass) at the crossover frequency to the tweeter, you are doing a 2.5 way and not a true 3 way. In this case the design is easier with two identical woofers (as Mike suggested).
Ralf
If your idea is to low pass the "woofer" at the baffle step frequency, to low pass the mid (not band pass) at the crossover frequency to the tweeter, you are doing a 2.5 way and not a true 3 way. In this case the design is easier with two identical woofers (as Mike suggested).
Ralf
Yeah I know 5" drivers aren't ideal for bass duties but they're what I have "in hand" so I thought is should be worth a try. The model I've been working on is two 5" wired parallel with the 12m and a seas tweeter.
Crossovers are 4th order electronic
Crossovers are 4th order electronic
I don't know if you have seen SB Acoustic's own Elok design.
SB Acoustics :: Elok
It uses your bass drivers in an 20L or so MTM reflex.
SB Acoustics :: Elok
It uses your bass drivers in an 20L or so MTM reflex.
I would go with MTM 30 lit vented, Fb=40 Hz,
F3/F6/F10= 40/35/31 Hz. Sensitivity about 87 dB
with full BSC. A lowish XO point, depending.
http://www.tb-speaker.com/detail/1230_04/25-1933s.htm
F3/F6/F10= 40/35/31 Hz. Sensitivity about 87 dB
with full BSC. A lowish XO point, depending.
http://www.tb-speaker.com/detail/1230_04/25-1933s.htm
Many favor real woofers for real bass. 8" or 10" woofer? Side-Side counter force pair?
Have you found any clever T + M + real_W speakers that fit your room, fashion and sonic goals?
A sealed SB15NRXC30 with an F3~85Hz from a clever cabinet construction has:
--the best sound
--the best transient response
--the lowest intermodulatino distortion
--the lowest total distortion
--the best power handling
Selecting the proper tweeter, cabinet construction, and T-M crossover is required for:
--the best sound
--the smoothest controlled directivity function
--the least beaming and no lobes
--the best imaging from diffraction control
Have you found any clever T + M + real_W speakers that fit your room, fashion and sonic goals?
A sealed SB15NRXC30 with an F3~85Hz from a clever cabinet construction has:
--the best sound
--the best transient response
--the lowest intermodulatino distortion
--the lowest total distortion
--the best power handling
Selecting the proper tweeter, cabinet construction, and T-M crossover is required for:
--the best sound
--the smoothest controlled directivity function
--the least beaming and no lobes
--the best imaging from diffraction control
Attachments
Can you elaborate on what you mean by a clever cabinet construction?
Also I'm still a bit lost on the "best alignment" front... if a speaker is better suited to a ported design does that mean I wont gain as much of the advantages as from a sealed alignment as are potentially there?
I know nothing about alignments in terms of what happens if a speaker isn't used with the ideal.
In an ideal world I'd probably build build larger woofer 3 ways, but as I have to limit the bass within reasonable levels in my new flat I guess I want flat response down to about 100hz, followed by the shallowest possible roll off... which I hope to be able to do with sealed and 5" woofers...That said I'm really hoping for "useable"bass down to at least 40Hz... My last 3 ways were pretty much flat 30-16k, and I was astonished by how the extra bass extension really seemed to bring recordings to life, it really was a different listening experience
You could have your bassmids installed in a sealed box and enjoy
thin sounding speakers or you could have them installed in a vented
design and enjoy decent bass performance.
thin sounding speakers or you could have them installed in a vented
design and enjoy decent bass performance.
There are a lot of good recommendations given to you. All the designs, from 2-way, 2-way w/subwoofer, MTM, 2.5 way and 3-way can sound outstanding if they are well designed.
However, you should decide based on your needs, like room size, your musical taste (ex some people like a lot of bass, some like loud etc), budget and wife/girlfriend/companion tolerance.
Here's a 2.5 way prototype that I just finished working on. Uses 2 units of HiVi M5a and a Vifa XT25. Box is simple to construct. XO not too complicated. Full passive, only one amp needed. Slim with small footprint. Low cost. And best of all, excellent performance.
Will it beat a speaker with a 12" woofer for bass? No. Goes down to about 50Hz (F3). 40Hz is probably -6dB. But it beats the hell out of a 3-way where mid-bass detail is concerned. Can I extend it down to 40Hz or below. Sure, but it gets complicated and cost shoots up. Can I do a wwmt, no problem but again cost goes up and I would have to seal up the mid. What I'm after is simple box construction and lowest total cost. If I can get the performance up to my expectations, I have met my goals.
However, you should decide based on your needs, like room size, your musical taste (ex some people like a lot of bass, some like loud etc), budget and wife/girlfriend/companion tolerance.
Here's a 2.5 way prototype that I just finished working on. Uses 2 units of HiVi M5a and a Vifa XT25. Box is simple to construct. XO not too complicated. Full passive, only one amp needed. Slim with small footprint. Low cost. And best of all, excellent performance.
Will it beat a speaker with a 12" woofer for bass? No. Goes down to about 50Hz (F3). 40Hz is probably -6dB. But it beats the hell out of a 3-way where mid-bass detail is concerned. Can I extend it down to 40Hz or below. Sure, but it gets complicated and cost shoots up. Can I do a wwmt, no problem but again cost goes up and I would have to seal up the mid. What I'm after is simple box construction and lowest total cost. If I can get the performance up to my expectations, I have met my goals.
Attachments
Many favor real woofers for real bass. 8" or 10" woofer? Side-Side counter force pair?
Have you found any clever T + M + real_W speakers that fit your room, fashion and sonic goals?
A good 3-way build with a real woofer can be used for many years in many different homes. Just reduce(equalize, smaller inductor) the bass level in this home. The 5" SB15NRX is a midrange well suited for a no-lobe 2Khz LR2 or LR4 crossover. -- Highly Recommended.
Most audio textbooks provide a comparison of transient response in a sealed enclosure vs. a ported enclosure. For sealed enclosures, textbooks compare square wave transients for a Qtc= 0.5 "critically damped" vs. a Qtc=0.57 "minimal ripple Bezel" vs. a Qtc=0.7 "maximal flat" Butterworth alignment. This graphical data is convincing, hearing the differences between sealed box alignments is compelling. Plucked strings. Drum rim-shots. Piano Forte'
"Clever cabinet construction" looks great, sounds great, and solves key challenges:
1) time alignment between different depth drivers.
---stepped baffles?
---slanted baffles?
---tweeter baffle wave guide?
---otherwise...solve with putting delay into Xover?
2) Edge diffraction
---large radius on edges?
---beveled edges?
---sphere like B&W?
---driver off-center placement?
3) center-to-center distance between drivers to control lobes
---ideal goal is C-to-C is shorter than Xover freq quarter wavelength
---physically small neo-tweeter?
4) controlled internal absorption of rear cone energy
---Owens 705 Fiberglass board?
---diffusion panel?
5) reduced panel resonances by
---H and V internal crossbracing?
---goo dampened panel-on-panel?
XXX) many more.... copy the best!
Have you found any clever T + M + real_W speakers that fit your room, fashion and sonic goals?
A good 3-way build with a real woofer can be used for many years in many different homes. Just reduce(equalize, smaller inductor) the bass level in this home. The 5" SB15NRX is a midrange well suited for a no-lobe 2Khz LR2 or LR4 crossover. -- Highly Recommended.
Most audio textbooks provide a comparison of transient response in a sealed enclosure vs. a ported enclosure. For sealed enclosures, textbooks compare square wave transients for a Qtc= 0.5 "critically damped" vs. a Qtc=0.57 "minimal ripple Bezel" vs. a Qtc=0.7 "maximal flat" Butterworth alignment. This graphical data is convincing, hearing the differences between sealed box alignments is compelling. Plucked strings. Drum rim-shots. Piano Forte'
"Clever cabinet construction" looks great, sounds great, and solves key challenges:
1) time alignment between different depth drivers.
---stepped baffles?
---slanted baffles?
---tweeter baffle wave guide?
---otherwise...solve with putting delay into Xover?
2) Edge diffraction
---large radius on edges?
---beveled edges?
---sphere like B&W?
---driver off-center placement?
3) center-to-center distance between drivers to control lobes
---ideal goal is C-to-C is shorter than Xover freq quarter wavelength
---physically small neo-tweeter?
4) controlled internal absorption of rear cone energy
---Owens 705 Fiberglass board?
---diffusion panel?
5) reduced panel resonances by
---H and V internal crossbracing?
---goo dampened panel-on-panel?
XXX) many more.... copy the best!
Hi Linesource,
Thanks for your input. You've pretty much said what I was starting to conclude - as much as I love the idea of a single driver covering the 'critical' listneing frequencies in a 3-way, the problems of centre-to-centre distance at the higher xo frequency are going to lead to lobing that's gonna annoy me - no matter what happens, I move around my listening environment, a speaker that sounds great in one place but not another isn't acceptable.
Additionally, it wasn't looking like it would solve my main problem with this set up... and that was the lack of bass. the logical thing to do was drop in some larger woofers... and that leads very quickly to the zaph audio design: Zaph|Audio - SB12.3 3-Way Tower
That design shows a good system can potentially be made using sealed enclosures and a single additional 12" woofer, It uses the same 4 midwoofers I have on hand, and integrating with my Seas 27TDFC tweeters instead would not be a challange at all.
My main objections to going with that design are as follows:
1. I haven't modelled it yet so not yet familiar, and I don't know that it meets my own personal design criteria, particularly in relation to phase and impedance.
2. It's possibly the ugliest looking loudspeaker I've ever seen, so I'd want to re-design the whole thing to an extend... new cabinets, new xo.
3. I really dislike the idea of a series resistor with the midwoofers...
I should mention that I currently have these drivers crossed LR4 1.5kHz. It's lower than I'd like but what I could do with the combination of half-decent inductors and caps I had hanging around. If I went 3-way I'd be tempted to go with 180/1.8 xo.
Points 2 and 3 above also mean I'm considering a pair of 8/10" woofers instead.
There is a difficulty in that these will be my home speakers for the foreseeable future, all the options have benefits - copy zaph, just add my own bass or go for the original 3-way idea. The worst is making sure I don't end up making 10 different cabinets along the way. At least if I 'copy' zaph I can start by just building some MTM cabinets.
Probably too late to try and think this through straight
Thanks for your input. You've pretty much said what I was starting to conclude - as much as I love the idea of a single driver covering the 'critical' listneing frequencies in a 3-way, the problems of centre-to-centre distance at the higher xo frequency are going to lead to lobing that's gonna annoy me - no matter what happens, I move around my listening environment, a speaker that sounds great in one place but not another isn't acceptable.
Additionally, it wasn't looking like it would solve my main problem with this set up... and that was the lack of bass. the logical thing to do was drop in some larger woofers... and that leads very quickly to the zaph audio design: Zaph|Audio - SB12.3 3-Way Tower
That design shows a good system can potentially be made using sealed enclosures and a single additional 12" woofer, It uses the same 4 midwoofers I have on hand, and integrating with my Seas 27TDFC tweeters instead would not be a challange at all.
My main objections to going with that design are as follows:
1. I haven't modelled it yet so not yet familiar, and I don't know that it meets my own personal design criteria, particularly in relation to phase and impedance.
2. It's possibly the ugliest looking loudspeaker I've ever seen, so I'd want to re-design the whole thing to an extend... new cabinets, new xo.
3. I really dislike the idea of a series resistor with the midwoofers...
I should mention that I currently have these drivers crossed LR4 1.5kHz. It's lower than I'd like but what I could do with the combination of half-decent inductors and caps I had hanging around. If I went 3-way I'd be tempted to go with 180/1.8 xo.
Points 2 and 3 above also mean I'm considering a pair of 8/10" woofers instead.
There is a difficulty in that these will be my home speakers for the foreseeable future, all the options have benefits - copy zaph, just add my own bass or go for the original 3-way idea. The worst is making sure I don't end up making 10 different cabinets along the way. At least if I 'copy' zaph I can start by just building some MTM cabinets.
Probably too late to try and think this through straight
A few quick thoughts..
Common reasons to use MTM
1) Higher SPL/watt from 2*M
.....27TDFC tweeter is only 91db sensitivity and has large diameter face plate.
.....Need 94db sensitivity SB29RDCN neo with further trimmed smallest possible face plate
.....some beaming is expected... 3-lobe directivity problem common....comb filtering in worst designs
.....A shallow baffle waveguide can allow lobe-free lower Xover freq with expensive dome. not for everyone
2) MTM and WMTMW approximate point souce with quarter wave spacing
.....requires 3"M with small face plate, plus 94db SB29RDCN with trimmed smallest possible face plate
.....ceiling vs. floor interaction can tilt/affect point source illusion
A well executed TMW can provide the most coherent sound in a small room, but must accept 86db sensititivy because SB15 covers some narrow-cabinet baffle step. Look over reducing 27TDFC face place, or SB29RDCN with trimmed smallest face plate.
Sony flagship SS AR1 uses TM-WW 1" dome + 5" Revelator M + two 8" Revelator woofers
SB17NRXC35-4 are often used with two SB23NRXS45-8 plus the 4-ohm SB29RDCN neo for high dynamics when a 4-ohm amp is available.
http://www.diyaudio.com/forums/multi-way/212738-sb-acoustics-3-ways.html
SB23NRXS45-8 are great woofers at a great price. time to buy.
Maybe for TMW, or full TM-WW like Sony SS AR1.
Common reasons to use MTM
1) Higher SPL/watt from 2*M
.....27TDFC tweeter is only 91db sensitivity and has large diameter face plate.
.....Need 94db sensitivity SB29RDCN neo with further trimmed smallest possible face plate
.....some beaming is expected... 3-lobe directivity problem common....comb filtering in worst designs
.....A shallow baffle waveguide can allow lobe-free lower Xover freq with expensive dome. not for everyone
2) MTM and WMTMW approximate point souce with quarter wave spacing
.....requires 3"M with small face plate, plus 94db SB29RDCN with trimmed smallest possible face plate
.....ceiling vs. floor interaction can tilt/affect point source illusion
A well executed TMW can provide the most coherent sound in a small room, but must accept 86db sensititivy because SB15 covers some narrow-cabinet baffle step. Look over reducing 27TDFC face place, or SB29RDCN with trimmed smallest face plate.
Sony flagship SS AR1 uses TM-WW 1" dome + 5" Revelator M + two 8" Revelator woofers
SB17NRXC35-4 are often used with two SB23NRXS45-8 plus the 4-ohm SB29RDCN neo for high dynamics when a 4-ohm amp is available.
http://www.diyaudio.com/forums/multi-way/212738-sb-acoustics-3-ways.html
SB23NRXS45-8 are great woofers at a great price. time to buy.
Maybe for TMW, or full TM-WW like Sony SS AR1.
Attachments
Linesource,
As always really appreciate your input, it gets the brain turning in the right direction (s).
Interesting that you didn't comment on the Zaph SB12.3...
Tweeter sensitivity... my hope was to run the tweeter with no L-Pad at all and use the series resistance of a 4th order electronic xo with the SB15's to achieve an overall sensitivity of around 91dB for the system. A wave guide of some kind isn't out of the question at all, but it means I need to go down another route of learning/design/simulation before I'll have a clue what I'm really doing with it.
I was hoping that crossing relatively low (LR4 1.8k) would prevent as much of the lobing issues as I could with centre to centre spacing... are these drivers just to big to get anywhere near "good"?
At the moment the 27TDFC's are crossed LR4 1.5k with single SB15's in the 2-ways, bearing in mind my main issues are: Lack of bass extension, lack of sensitivity, lack of peak SPL, everything points to WMTMW if I can make it work. It would be a shame to have to lose the seas tweeters as money isn't unlimmited, but they're great tweeters so sure they'll find a home no matter what happens.
I've been playing with a few construction ideas so will come back with renderings next week when I've done this poxy literature review. Goind to school at this age was certainly a questionable decision!
As always really appreciate your input, it gets the brain turning in the right direction (s).
Interesting that you didn't comment on the Zaph SB12.3...
Tweeter sensitivity... my hope was to run the tweeter with no L-Pad at all and use the series resistance of a 4th order electronic xo with the SB15's to achieve an overall sensitivity of around 91dB for the system. A wave guide of some kind isn't out of the question at all, but it means I need to go down another route of learning/design/simulation before I'll have a clue what I'm really doing with it.
I was hoping that crossing relatively low (LR4 1.8k) would prevent as much of the lobing issues as I could with centre to centre spacing... are these drivers just to big to get anywhere near "good"?
At the moment the 27TDFC's are crossed LR4 1.5k with single SB15's in the 2-ways, bearing in mind my main issues are: Lack of bass extension, lack of sensitivity, lack of peak SPL, everything points to WMTMW if I can make it work. It would be a shame to have to lose the seas tweeters as money isn't unlimmited, but they're great tweeters so sure they'll find a home no matter what happens.
I've been playing with a few construction ideas so will come back with renderings next week when I've done this poxy literature review. Goind to school at this age was certainly a questionable decision!
Hi nannoo,
I have a german DIY-article from Udo Wohlgemuth by using these Mid-woofers for a nice wall-speaker. http://www.lautsprecherbau.de/Wallstreet-3-und-4
Probably this will help you for your design...
I have a german DIY-article from Udo Wohlgemuth by using these Mid-woofers for a nice wall-speaker. http://www.lautsprecherbau.de/Wallstreet-3-und-4
Probably this will help you for your design...
Hi,
Yeah seen that before but good to look at it again, really highlights that I'm just not going to get the bass response I'm after from these drivers, sealed or ported it just won't dig low. problem is I'm in as flat so need the option to dissengage/re-engage the bass. I'm starting to think some kind of bass box with a MTM/TM on top is going to be best, with some way to easily engage/disengage the bass, including the high pass filter on the tops.... more thought is going to be needed...
Yeah seen that before but good to look at it again, really highlights that I'm just not going to get the bass response I'm after from these drivers, sealed or ported it just won't dig low. problem is I'm in as flat so need the option to dissengage/re-engage the bass. I'm starting to think some kind of bass box with a MTM/TM on top is going to be best, with some way to easily engage/disengage the bass, including the high pass filter on the tops.... more thought is going to be needed...
I have to say, I'm finding more and more MTMWW designs and am rapidlt leaning in that direction. I have to ask though, does anyone know what's going on with the high end wilson audio gear? it seems they all feature a combination of bass woofers of different form factors, are these in a .5 way configuration or what's the deal??
Getting the full "virtual point source" directivity from a WMTMW requires that the tweeter be at ear level... 39" - 42" in most seating. You would end up with ~60" tall x ~12" wide speakers. Perhaps you could unfold a cardboard box and cut a 60" x 12" baffle to get some idea how big-speaks will integrate into your room. Could work if you have a large flat screen on the wall.
You could fold down this cardbard baffle to 43" to mimic a TM-WW Sony AR1-SS
You could fold down this cardbard baffle to 43" to mimic a TM-WW Sony AR1-SS
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