Hi All,
in the following I would like to describe my way to my first ob construction (and at the same time my first own speaker construction ever). After building two boxes I became aware of a thread here - the Manzanita. I built it and it happened - the OB bug bit me, it is a great speaker!
After that - it always has to be bigger - I also built the Manzanita Ultra.
But we didn't become friends, this speaker didn't fit my space, my music, my listening habits, etc.
In particular I like the open way of playing, the room, the stage, I haven't heard anything like that from conventional speakers, up to the high four-digit price range... I still tried to listen to music with conventional speakers, but something was missing... That was the point where I decided to make my own OB construction. And if possible, it must have a high sensitivity in order to be able to operate it with enough reserve with First Watt amps without any problems.
So, enough of the introduction...
Right from the start it was clear to me that it had to be a woofer-full-range combination, i.e. a 2-way system (the xo is easy there... I thought). At the same time I found a thread about the new SB Acoustics SB20FRPC30-8. Cheap enough so I ordered it straight away and two days later I installed them - in a TL box that was absolutely not designed for this speaker. I just wanted to know how the speaker sounds, approximately. And what I heard made me happy, to put it briefly.
The next step was to install it in an OB - I used that of the Manzanita Ultra. But since the Manzanita´s woofer is not very sensitive (at least compared to the SB FR with 92 dB), a new woofer was needed. Based on a recommendation, the choice fell on the SB Audience 12" OB, which is intended for OB applications. "Quickly" built an xo - low pass, high pass, 6 dB/octave, done... and it sounded terrible
There was a lack of... everything. And the measurement confirmed it...
To improve the highs I added a tweeter, of course the xo had to be redesigned quite a bit.
At first it sounded good (in the upper range), but the longer I listened, the more unbearable it became...
The lack of bass was also very clear... so I figured a second, larger woofer might help (yes, it can, but not in the way I thought).
After a short search, the Eminence Alpha 15A was delivered - and that's when things really got going. I guess I've built countless baffles out of cardboard and if it sounds bearable, also out of foam... with and without wings, with big and small ones, or even with asymmetrical wings, but it didn't really work out. After a while the bass was okay - far from good, but okay. But there were big problems in the xo, because I treated the 15" and the 12" woofer separately, with different (high) crossing frequencies. And the mids... absolute no go...
There are no pictures from this phase, that was more doggedness than conscious action
Of course I also changed the xo every time... I didn't even get to measure it because I usually didn't like what I heard.
That was the point where I thought "what were you thinking, or even imagining?" But I didn't want to give up.
So - read, read, read was the motto. And most importantly, understand what works and what not. And why. @Pano helped me a lot with his contribution - many thanks
The most important thing was to lower the crossing frequency. Originally I crossed at about 1 kHz - that's incredibly high, even if that seems to be okay according to the specification of the drivers. But it is not. And that was one of the keys. First I decided to switch the two woofers in parallel (gain in output) and then I lowered the crossing frequency to around 120 Hz - and it was like a revelation. There was also the almost endless trial and error with and without wings, different wing shapes, heights, depths, etc... until a certain size and shape proved to be right (better: to be the best for this configuration).
But the revelation was only partial..., the mids didn't want to appear.
I stared at the circuitry of the xo in the SIM - and then inverted the full range. Wow, the fr response became "smooth as glass".
Put into practice quickly.
With two different full range drivers.
The MarkAudio Alpair 12P was added to the SB as an alternative, because I didn't really like the high-frequency range of the SB (on paper). So it started with the full range again. Cardboard baffle with different positions; middle, right, left... I'm still not sure which is the better option, but these are minor things compared to the start...
Currently the 12P is in break-in, the SB is now centrally positioned, and I like it.
And now the speakers sound incredibly good. For real. The best of all wives (she has nothing, zero, niente, nada to do with this hobby or with music) has heard all my speakers so far and yesterday also the "new ones"... and she said - "wow, they are them best of all, but far the best".
The feeling of pride came on
I took measurements today - I like the fr response
And finished a version of the baffles with the router. They are made of 18 mm MDF, in this version with decentralized placement for the Alpair 12P.
Yes, three-piece baffle. One of the findings was that - if the gap is not larger than 4-5 mm - the sound is better (for me).
I have no idea why, maybe the resonances of the individual baffles don't influence the other drivers.
Well, of course it's not finished yet. But I'm incredibly happy. I started at the beginning of November and there were phases where things looked bad.
At the end of this contribution, the current status of the xo - not quite finished yet (as you can see, not only the SB and the 12P are taken into account, but also the Sonido SWR250, which I will be ordering shortly).
This is so much fun.
The journey will continue
in the following I would like to describe my way to my first ob construction (and at the same time my first own speaker construction ever). After building two boxes I became aware of a thread here - the Manzanita. I built it and it happened - the OB bug bit me, it is a great speaker!
After that - it always has to be bigger - I also built the Manzanita Ultra.
But we didn't become friends, this speaker didn't fit my space, my music, my listening habits, etc.
In particular I like the open way of playing, the room, the stage, I haven't heard anything like that from conventional speakers, up to the high four-digit price range... I still tried to listen to music with conventional speakers, but something was missing... That was the point where I decided to make my own OB construction. And if possible, it must have a high sensitivity in order to be able to operate it with enough reserve with First Watt amps without any problems.
So, enough of the introduction...
Right from the start it was clear to me that it had to be a woofer-full-range combination, i.e. a 2-way system (the xo is easy there... I thought). At the same time I found a thread about the new SB Acoustics SB20FRPC30-8. Cheap enough so I ordered it straight away and two days later I installed them - in a TL box that was absolutely not designed for this speaker. I just wanted to know how the speaker sounds, approximately. And what I heard made me happy, to put it briefly.
The next step was to install it in an OB - I used that of the Manzanita Ultra. But since the Manzanita´s woofer is not very sensitive (at least compared to the SB FR with 92 dB), a new woofer was needed. Based on a recommendation, the choice fell on the SB Audience 12" OB, which is intended for OB applications. "Quickly" built an xo - low pass, high pass, 6 dB/octave, done... and it sounded terrible
There was a lack of... everything. And the measurement confirmed it...
To improve the highs I added a tweeter, of course the xo had to be redesigned quite a bit.
At first it sounded good (in the upper range), but the longer I listened, the more unbearable it became...
The lack of bass was also very clear... so I figured a second, larger woofer might help (yes, it can, but not in the way I thought).
After a short search, the Eminence Alpha 15A was delivered - and that's when things really got going. I guess I've built countless baffles out of cardboard and if it sounds bearable, also out of foam... with and without wings, with big and small ones, or even with asymmetrical wings, but it didn't really work out. After a while the bass was okay - far from good, but okay. But there were big problems in the xo, because I treated the 15" and the 12" woofer separately, with different (high) crossing frequencies. And the mids... absolute no go...
There are no pictures from this phase, that was more doggedness than conscious action
Of course I also changed the xo every time... I didn't even get to measure it because I usually didn't like what I heard.That was the point where I thought "what were you thinking, or even imagining?" But I didn't want to give up.
So - read, read, read was the motto. And most importantly, understand what works and what not. And why. @Pano helped me a lot with his contribution - many thanks
The most important thing was to lower the crossing frequency. Originally I crossed at about 1 kHz - that's incredibly high, even if that seems to be okay according to the specification of the drivers. But it is not. And that was one of the keys. First I decided to switch the two woofers in parallel (gain in output) and then I lowered the crossing frequency to around 120 Hz - and it was like a revelation. There was also the almost endless trial and error with and without wings, different wing shapes, heights, depths, etc... until a certain size and shape proved to be right (better: to be the best for this configuration).
But the revelation was only partial..., the mids didn't want to appear.
I stared at the circuitry of the xo in the SIM - and then inverted the full range. Wow, the fr response became "smooth as glass".
Put into practice quickly.
With two different full range drivers.
The MarkAudio Alpair 12P was added to the SB as an alternative, because I didn't really like the high-frequency range of the SB (on paper). So it started with the full range again. Cardboard baffle with different positions; middle, right, left... I'm still not sure which is the better option, but these are minor things compared to the start...
Currently the 12P is in break-in, the SB is now centrally positioned, and I like it.
And now the speakers sound incredibly good. For real. The best of all wives (she has nothing, zero, niente, nada to do with this hobby or with music) has heard all my speakers so far and yesterday also the "new ones"... and she said - "wow, they are them best of all, but far the best".
The feeling of pride came on
I took measurements today - I like the fr response
And finished a version of the baffles with the router. They are made of 18 mm MDF, in this version with decentralized placement for the Alpair 12P.
Yes, three-piece baffle. One of the findings was that - if the gap is not larger than 4-5 mm - the sound is better (for me).
I have no idea why, maybe the resonances of the individual baffles don't influence the other drivers.
Well, of course it's not finished yet. But I'm incredibly happy. I started at the beginning of November and there were phases where things looked bad.
At the end of this contribution, the current status of the xo - not quite finished yet (as you can see, not only the SB and the 12P are taken into account, but also the Sonido SWR250, which I will be ordering shortly).
This is so much fun.
The journey will continue
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Super work and thanks for the write up. You are learning just like the greats learned how to do OB, but trying, mocking up baffles, experimenting. You are now getting a good sense of what works and why it works. 
Looking at your crossover gave me a start. What is the value of that inductor??? Then I realized you live in a comma separated land.
Looking at your crossover gave me a start. What is the value of that inductor???
Then I realized you live in a comma separated land.
Thanks @grindstone and @nicoch58
Nicoch, you mean two Biancos instead of one Alpha? So 3 Biancos? Well, I started in a different direction, so I can't say much about that. I know that the Alpha and the Bianco have different parameters, but I think the interaction is very good. The -3dB point is at about 50 Hz, and I can live with it.
I forgot to mention that I also tried the D'Appolito configuration, but I didn't like the significantly reduced height of the stage, even with tilted speaker. Another point that I have noticed since yesterday is the ongoing improvement of the drivers. Especially the Alpha and the FR are developing further and I will have to tweak the xo (the FR is getting louder and louder and therefore "too much").
Nicoch, you mean two Biancos instead of one Alpha? So 3 Biancos? Well, I started in a different direction, so I can't say much about that. I know that the Alpha and the Bianco have different parameters, but I think the interaction is very good. The -3dB point is at about 50 Hz, and I can live with it.
I forgot to mention that I also tried the D'Appolito configuration, but I didn't like the significantly reduced height of the stage, even with tilted speaker. Another point that I have noticed since yesterday is the ongoing improvement of the drivers. Especially the Alpha and the FR are developing further and I will have to tweak the xo (the FR is getting louder and louder and therefore "too much").
Looks like you've got something almost modular there. A frame with means to swap in / out different panels; I'm pretty sure there's even a commercial product that does it. Sounds like you'd also benefit from DSP for future research purposes of course.
And here's to all those wives that dont give a ---- about any of this - but can easily confirm or deny what actually sounds good, never the less!
And here's to all those wives that dont give a ---- about any of this - but can easily confirm or deny what actually sounds good, never the less!
Yes, modular in terms of using different FR drivers, as I wrote earlier; I have another baffle for/with an Alpair 12P. I know there is a commercial product too with separated baffles for the drivers, but they have a different configuration of the drivers. At the beginning I had one big baffle - as I wrote -, but after several trials with I-don't-know-how-many baffles I ended up with a multi-part baffle. My speakers have much bigger wings with a straight shape and a much simpler support frame.
Hey... it sounds like self defense but I knew that there will be comparisons because of the similarity.
DSP... I have to take a look on this later, because I don't have any.
Hey... it sounds like self defense
but I knew that there will be comparisons because of the similarity.DSP... I have to take a look on this later, because I don't have any.
DSP provides the opportunity to mess with crossover frequencies, slopes (orders), sometimes delays - etc - at the type of a number on a GUI. So you can experiment to your hearts content and when you find just the right combination that sounds how you want - then cast it to an RLC crossover network. That part doesnt happen just like that, as you already know, but the discovery part is much less painless.
The kicker is, for DSP each driver needs its own amp. So you'd need a six channel amp for the DSP box to drive for your 3 way, if you want to listen in stereo. (For measurement only, 3 channels would do). The reason why hardware speaker crossovers are still used? No one wants six channels of amplification when two would do.
Yeah, it's a good idea, I never thought of DSP in this direction. In fact I would only need two stereo/dual mono power amps (and soon I will have the second and third and fourth finished, so it's not an issue), because it's only two way, the two woofers are parallelled.
