I started a thread a while back about an open-baffle TB W3-871S speaker that I toyed with. Since then I tried alot of other drivers, in many configurations, but kept coming back to the TB. I tried the TB driver in ported, sealed, TLs but here again I kept coming back to the W3-871S in an open-baffle, I like it THAT much.
Well, I wanted a small speaker, so I decided on a folded-baffle. I wanted it small to conserve space and so it wouldn't cost to much to use a real wood and not particle board or MDF, I ended up using solid birch. But while the mid-bass/midrange/tweeter combo had been settled on and I liked it so very much, all I needed was bass that was just as amazing and also, great (and I mean really amazing) bang for the buck.
I thought about using TLs, but stereo bass in a TL would just have to be too huge, I wanted LOW bass and an TL to go as low as I wanted would have to be enormous. And while a ported box could be made to go as low as I wanted, it would also have to be huge, and I never really liked the quality of a ported box. But, when I had originally toyed with the W3-871S in an open-baffle I used it with a cheap stryke 7" woofer, also in the open-baffle, the bass wasn't super low, but it was remarkably good. So I decided on dipole bass as well... As it turns out, it was a very good choice indeed...
Now, in the end the speakers measured 16" wide, 24" tall, and had two side 12" deep, a nice size for my room. Since they were to be this size, I didn't want a 15" woofer, it would have just been too large, I wanted 12", no smaller either. I searched for a long time to find a woofer with all the qualities I wanted in the price range I was looking in (under $100 CND each, ended up being $125 CND with shipping and tax and everything, I was very pleased). Yet, even in this price range I wanted a driver that seemed to be well built, a quality driver always seems to sound better, although isn't always more expensive.
I found a driver that was 12", had an xmax of 6mm one way (wich was good enough for me, it is being powered by a single-ended Class-A MOSFET amp, so it doesn't have power to push it past it's excursion, I believe that quality amplification really matters for the bass, not just the mids and highs). I wanted a rubber surround, low enough fs (ended up with 28Hz, good enough). It was the MCM 55-1465, it's well built, VERY well built for the money.
The only thing is, no bass driver would go deep in the "enclosure" I specified above. I knew this and had decided form the begining to use equilisation on the dipole rolloff. But I wanted a driver that would rolloff as slowly as possible, so luckily the driver I had my heart set on had a Qts that wasn't too high at all. It ended up rolling off at pretty close to 6dB/octave until a bit under it's fs, then it dropped.
So I implemented a 6dB/octave boost starting around the mid 20s, I get bass a bit lower than 30Hz, into the 20s, but after that it drops like a stone, but to me bass in the 20s is VERY low since it is flat down most of the way. I added a potentiometer before the gain stage in the equilisation so that if I place the drivers on the floor I can adjust the bass level, and also because I knew not how much gain to give the eq'ed bass. I implemented all this in the preamp/cross-over/dipole eq box, all together and I kept it as simple as possible. And I crossed over the fullrange driver 1st order at 150Hz, so the bass driver doesn't go high and the fullrange doesn't go anywhere near it's xmax, it barely moves.
The end result? Very, very nice. I have never heard bass this good, I can't stress that enough, it is a cheap driver, but cheap doesn't mean bad, it sounds amazing. And with a bass driver filling in the lower octaves, the W3-871S is really allowed to shine, and shine it does, ALOT. I've built numerous loudspeakers before and they all sounded great (well, most, there were flops), but this last system (the speakers can't really operate without the preamp/crossover and acceseries) really sounds much better, I atribute it alot to the dipoleness of it. Many threads have been started with people toying with dipoles lately, and it isn't hard to realise why when you've heard one.
Well, I've been re-listening to my colection now and I just thought I'd give an update to the growing design that started with my thread a little while back. Sorry for the length of this thread, I'll just post a couple pictures, and sorry for the picture quality, I was going to take better ones after, but the bateries in my camera died on me...
Well, I wanted a small speaker, so I decided on a folded-baffle. I wanted it small to conserve space and so it wouldn't cost to much to use a real wood and not particle board or MDF, I ended up using solid birch. But while the mid-bass/midrange/tweeter combo had been settled on and I liked it so very much, all I needed was bass that was just as amazing and also, great (and I mean really amazing) bang for the buck.
I thought about using TLs, but stereo bass in a TL would just have to be too huge, I wanted LOW bass and an TL to go as low as I wanted would have to be enormous. And while a ported box could be made to go as low as I wanted, it would also have to be huge, and I never really liked the quality of a ported box. But, when I had originally toyed with the W3-871S in an open-baffle I used it with a cheap stryke 7" woofer, also in the open-baffle, the bass wasn't super low, but it was remarkably good. So I decided on dipole bass as well... As it turns out, it was a very good choice indeed...
Now, in the end the speakers measured 16" wide, 24" tall, and had two side 12" deep, a nice size for my room. Since they were to be this size, I didn't want a 15" woofer, it would have just been too large, I wanted 12", no smaller either. I searched for a long time to find a woofer with all the qualities I wanted in the price range I was looking in (under $100 CND each, ended up being $125 CND with shipping and tax and everything, I was very pleased). Yet, even in this price range I wanted a driver that seemed to be well built, a quality driver always seems to sound better, although isn't always more expensive.
I found a driver that was 12", had an xmax of 6mm one way (wich was good enough for me, it is being powered by a single-ended Class-A MOSFET amp, so it doesn't have power to push it past it's excursion, I believe that quality amplification really matters for the bass, not just the mids and highs). I wanted a rubber surround, low enough fs (ended up with 28Hz, good enough). It was the MCM 55-1465, it's well built, VERY well built for the money.
The only thing is, no bass driver would go deep in the "enclosure" I specified above. I knew this and had decided form the begining to use equilisation on the dipole rolloff. But I wanted a driver that would rolloff as slowly as possible, so luckily the driver I had my heart set on had a Qts that wasn't too high at all. It ended up rolling off at pretty close to 6dB/octave until a bit under it's fs, then it dropped.
So I implemented a 6dB/octave boost starting around the mid 20s, I get bass a bit lower than 30Hz, into the 20s, but after that it drops like a stone, but to me bass in the 20s is VERY low since it is flat down most of the way. I added a potentiometer before the gain stage in the equilisation so that if I place the drivers on the floor I can adjust the bass level, and also because I knew not how much gain to give the eq'ed bass. I implemented all this in the preamp/cross-over/dipole eq box, all together and I kept it as simple as possible. And I crossed over the fullrange driver 1st order at 150Hz, so the bass driver doesn't go high and the fullrange doesn't go anywhere near it's xmax, it barely moves.
The end result? Very, very nice. I have never heard bass this good, I can't stress that enough, it is a cheap driver, but cheap doesn't mean bad, it sounds amazing. And with a bass driver filling in the lower octaves, the W3-871S is really allowed to shine, and shine it does, ALOT. I've built numerous loudspeakers before and they all sounded great (well, most, there were flops), but this last system (the speakers can't really operate without the preamp/crossover and acceseries) really sounds much better, I atribute it alot to the dipoleness of it. Many threads have been started with people toying with dipoles lately, and it isn't hard to realise why when you've heard one.
Well, I've been re-listening to my colection now and I just thought I'd give an update to the growing design that started with my thread a little while back. Sorry for the length of this thread, I'll just post a couple pictures, and sorry for the picture quality, I was going to take better ones after, but the bateries in my camera died on me...
Congrats,
these must be the first „bookshelf-size“ dipols I see in my life.
Your original thread about the Tangbands in an open baffle helped me start into OBs myself. And there seems no way back.
Still I am wondering how you could place the TB so near to the baffle edge. Guess it´s no more than 12 cm distance. Following Linkwitz´ theories you should suffer from a heavy dropping in SPL downward from ~1200 Hz. Do you have measurements of the system?
I am asking because I want to cut off some of the „overhead“ of my open baffles for aesthetic reason, but don´t know how much I can risk before compromising the frequency range.
Rudolf
these must be the first „bookshelf-size“ dipols I see in my life.
Your original thread about the Tangbands in an open baffle helped me start into OBs myself. And there seems no way back.
Still I am wondering how you could place the TB so near to the baffle edge. Guess it´s no more than 12 cm distance. Following Linkwitz´ theories you should suffer from a heavy dropping in SPL downward from ~1200 Hz. Do you have measurements of the system?
I am asking because I want to cut off some of the „overhead“ of my open baffles for aesthetic reason, but don´t know how much I can risk before compromising the frequency range.
Rudolf
Actually the TBs are about 15cm from the side, but there is a 30cm side panel on each side of the baffle. I tried placing the W3-871S on many test baffles to see if there were any problems, the final position was where I liked it best (both for looks and for sound). Unfortunately I haven't taken full measurements yet, I'll have to do that, but I'm just so busy listening to all my music again.
If you're worried of losing frequency response, just do what I did, try it on a test baffle. If you don't want to use wood I saw someone else on the forum once use cardboard as a test baffle, could be a good idea...
If you're worried of losing frequency response, just do what I did, try it on a test baffle. If you don't want to use wood I saw someone else on the forum once use cardboard as a test baffle, could be a good idea...
Thanks JoeBob,
actually I was only worrying about the distance from the TB to the top of the baffle. Did you find a HUGE difference between the actual position and some other placement nearer to the center of a board? Or was it more a matter of taste?
I will keep an eye on your postings - in case you find time to take some measurements.
Happy listening.
Rudolf
actually I was only worrying about the distance from the TB to the top of the baffle. Did you find a HUGE difference between the actual position and some other placement nearer to the center of a board? Or was it more a matter of taste?
I will keep an eye on your postings - in case you find time to take some measurements.
Happy listening.
Rudolf
T/S parameters
Hello Joebob,
Looks like a great project!!
Do you have the T/S parameters for the woofer?
Have you compard it to other high quality woofers besides the Strike you mentioned?
Do you think its posible to match the levels of the units pasively?
Hope you can help us out.........
CO
Hello Joebob,
Looks like a great project!!
Do you have the T/S parameters for the woofer?
Have you compard it to other high quality woofers besides the Strike you mentioned?
Do you think its posible to match the levels of the units pasively?
Hope you can help us out.........
CO
Found these on-line don't know how accurate they are. Small measurements were taken with voice coils in parallel.
55-1465
Voice Coil Resistance RE = 6.47 ohms per coil
Resonance Frequency fS = 28.1 Hz
Total Quality Factor QTS = 0.326
Electrical Quality Factor QES = 0.374
Mechanical Quality Factor QMS = 2.52
Volume Compliance VAS = 4.80 cubic feet
We decided to use a vented-box enclosure for the woofer. For its design, we assumed the box quality factor QL = 7. From the QL = 7 design chart, the vented-box design data for QTS = 0.326 is as follows:
Helmholtz Tuning Ratio h = 1.21
Compliance Ratio alpha = 2.24
Cutoff Frequency Ratio q = 1.41
With the above data, the woofer enclosure parameters can be calculated as follows:
Enclosure Volume VB = VAS/alpha = 2.14 cubic feet
-3 dB Cutoff Frequency f3 = q * fS = 39.6 Hz
Helmholtz Frequency fB = h * fS = 34 Hz
55-1465
Voice Coil Resistance RE = 6.47 ohms per coil
Resonance Frequency fS = 28.1 Hz
Total Quality Factor QTS = 0.326
Electrical Quality Factor QES = 0.374
Mechanical Quality Factor QMS = 2.52
Volume Compliance VAS = 4.80 cubic feet
We decided to use a vented-box enclosure for the woofer. For its design, we assumed the box quality factor QL = 7. From the QL = 7 design chart, the vented-box design data for QTS = 0.326 is as follows:
Helmholtz Tuning Ratio h = 1.21
Compliance Ratio alpha = 2.24
Cutoff Frequency Ratio q = 1.41
With the above data, the woofer enclosure parameters can be calculated as follows:
Enclosure Volume VB = VAS/alpha = 2.14 cubic feet
-3 dB Cutoff Frequency f3 = q * fS = 39.6 Hz
Helmholtz Frequency fB = h * fS = 34 Hz
Well, where did you find those? I know there was a site on the net that had measurements taken on that woofer, they were almost the same to those given to me by MCM. I no longer have the email from them (got deleted long time ago) but if you email MCM asking for such parameters they'll give them to you with no problems.
As it is now I'm only using one voice coil, the second is used for the motion feedback to the amp. My EQ is very simple, by itself the woofer will start to rolloff at first order until about 30Hz then the slope steepens and drops off, so I've implemented a 1st order low-pass with a -3dB point of I do believe 32Hz, this takes care of the rolloff until 30Hz, which is enough for me, of course, there must be gain, which I added, a gain of 5-6 above the fullrange landed it just right, I tweaked that value alot until I found what I liked for my room.
I toyed with a second pole on the woofer but I found that this way it rolls off around the 100-200Hz mark and this makes it perfect to crossover with the fullrange at 150Hz. Trying to get deeper bass wasn't practical and it greatly complicated the circuit.
As for matching them passively, well you'd have to attenuate the fullrange by quite a bit, since I use a gain of 5 on the woofer, then if you have no gain you'd have to attenuate the fullrange by an equal amout of dB, it's possible, but that'd burn up some power in resistors.
Comparing to other woofers, well I like it alot, and I prefer this solution to most woofers I've heard, but I haven't had the chance to compare it to different woofers in dipole configurations. I can't afford expensive woofers and I can only hear them in other peoples systems, and while they sound good, I much prefer the sound of my dipoles. As for if an expensive woofer would sound better in place of my cheaper one, I'm betting it would, but by how much...
As it is now I'm only using one voice coil, the second is used for the motion feedback to the amp. My EQ is very simple, by itself the woofer will start to rolloff at first order until about 30Hz then the slope steepens and drops off, so I've implemented a 1st order low-pass with a -3dB point of I do believe 32Hz, this takes care of the rolloff until 30Hz, which is enough for me, of course, there must be gain, which I added, a gain of 5-6 above the fullrange landed it just right, I tweaked that value alot until I found what I liked for my room.
I toyed with a second pole on the woofer but I found that this way it rolls off around the 100-200Hz mark and this makes it perfect to crossover with the fullrange at 150Hz. Trying to get deeper bass wasn't practical and it greatly complicated the circuit.
As for matching them passively, well you'd have to attenuate the fullrange by quite a bit, since I use a gain of 5 on the woofer, then if you have no gain you'd have to attenuate the fullrange by an equal amout of dB, it's possible, but that'd burn up some power in resistors.
Comparing to other woofers, well I like it alot, and I prefer this solution to most woofers I've heard, but I haven't had the chance to compare it to different woofers in dipole configurations. I can't afford expensive woofers and I can only hear them in other peoples systems, and while they sound good, I much prefer the sound of my dipoles. As for if an expensive woofer would sound better in place of my cheaper one, I'm betting it would, but by how much...
Dual passive woofers on full size baffle?
Hi,
I dont know what the efficiency is of the woofer. If you think my idea is possible then i should investigate it some more. I was thinking of using a fully passive configuration on a full size baffle so i wouldnt need the bass lift that much. The woofer must be near the the efficiency of te full range of 87 dB TB? your talking of using resistors on the FRange?. Maby i could even add a second woofer.
How are the dynamics of the whole? I have horns now and i love the dynamic sound. Can the TB handle a little abuse? I think i'll get a few extra for that price.
Thanks,
CO
Hi,
I dont know what the efficiency is of the woofer. If you think my idea is possible then i should investigate it some more. I was thinking of using a fully passive configuration on a full size baffle so i wouldnt need the bass lift that much. The woofer must be near the the efficiency of te full range of 87 dB TB? your talking of using resistors on the FRange?. Maby i could even add a second woofer.
How are the dynamics of the whole? I have horns now and i love the dynamic sound. Can the TB handle a little abuse? I think i'll get a few extra for that price.
Thanks,
CO
I just got the following specs from the techs at MCM:
Item# 55-1465 WOOFER 12" MCM POLY PAPER
Size 12.000 IN
Mount Width 12.000 IN
Cutout Diam 11.000 IN
Mount Depth 5.500 IN
Magnet Weight 42.000 / OZ
Voice Coil Diam 2.000 / IN
Cone Material PP POLYPROPYLENE
Surround Material RB RUBBER
RMS Watts 100
Peak Watts 200
Imp/Ohm 8.00
SPL (db) 93.00
Frequency Rsp 20-3K
Free Air 28.00 HZ
QES .328
QMS 3.130
QTS .298
VAS 7.200 CF
RE 13.000 OH
XMAX 5.000 MM
Item# 55-1465 WOOFER 12" MCM POLY PAPER
Size 12.000 IN
Mount Width 12.000 IN
Cutout Diam 11.000 IN
Mount Depth 5.500 IN
Magnet Weight 42.000 / OZ
Voice Coil Diam 2.000 / IN
Cone Material PP POLYPROPYLENE
Surround Material RB RUBBER
RMS Watts 100
Peak Watts 200
Imp/Ohm 8.00
SPL (db) 93.00
Frequency Rsp 20-3K
Free Air 28.00 HZ
QES .328
QMS 3.130
QTS .298
VAS 7.200 CF
RE 13.000 OH
XMAX 5.000 MM
JoeBob said:
Serow said:
I dont know about PP drivers... on some brands i have heard a "plasticky sound" on transients. I thought they were paper. Is it a mix of PP and paper?
Does anyone know what the moving mass and inductance parameters are?
Joebob,
if i use two woofers of 93 db wont i have 96 db compared to the 87 db of the TB ? Thats a big differance. One woofer might be enough?
Thanks to all,
CO
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