Make sure all the seams are sealed and airtight.
A small pinhole will reduce the bass output considerably.
Something you have to mention to your carpenter.
A small pinhole will reduce the bass output considerably.
Something you have to mention to your carpenter.
Reinforcement is not necessary if 18 mm thick pine is used.
Fine-tune the size of the boards, giving priority to the internal volume and internal dimensions.
Adjustment of the sound absorbing material can be made later, either on the back or top board.
No gap is preferable, but I don't care about 0.5mm.
Is it possible to compile all impressions of the SB20FRPC30-8 here?
Advantages and disadvantages of this driver.
Which box, or which boxes have you used and listened to.
This may be the basis for the decision to purchase this driver.
Thanks in advance!
Advantages and disadvantages of this driver.
Which box, or which boxes have you used and listened to.
This may be the basis for the decision to purchase this driver.
Thanks in advance!
Good idea, Leif.
A few examples are allready show in this thread.
For myself mentoined the version in a 35l cab - driver pimped with a magnet. Works fine, x-over ist close to finished.
The 60l cabinet is still growing - hope to get it ready during Easter.
For those who are impatient or a little snoopy: take a breath here:
https://www.diy-hifi-forum.eu/forum/showthread.php?23075-Mal-wieder-ein-8-quot-FR-SB8FRPC30
The finished version will be presentet here.
A few examples are allready show in this thread.
For myself mentoined the version in a 35l cab - driver pimped with a magnet. Works fine, x-over ist close to finished.
The 60l cabinet is still growing - hope to get it ready during Easter.
For those who are impatient or a little snoopy: take a breath here:
https://www.diy-hifi-forum.eu/forum/showthread.php?23075-Mal-wieder-ein-8-quot-FR-SB8FRPC30
The finished version will be presentet here.
I'm using this driver in an OB configuration so can't tell much about the behavior as a woofer, but very much as a mid/high driver. And as such, they are great. Very clean sound with great mids and crisp and clear highs. My only issue is (maybe because of installing it many times during trials) some mechanical noise (maybe resonances?) from one of the drivers so I will replace it as soon as it will be available again from my source.
With that flat response you could use 1st order crossovers, if you are into that. I prefer 1st order crossovers but they are so very difficult to realize. Active is the way to go these days.
Yep.but at least, tweeter integration is easier than woofers at 1st order.
After seeing some reviews, them crossing as high as 8kHz, I would look into crossing between 5~8kHz now. It does look like a very good driver.
A few updates since my last post.
First I changed the baffle from pine to a slightly smaller version made from 18mm MDF and 'finished' with self-adhesive vinyl flooring incorporating a 2mm rubber layer - has resulted in much better looking (IMO) speakers that are acoustically more inert.
The most recent step was to add 2 x SB Acoustics SB20PFCR30-8 wired in parallel in each baffle. Myself and my son fitted them on Friday night and they are actively driven (in stereo) and low passed at about 130hz with a 12db slope.
These speakers no longer need any bass support from sealed box woofers and they have a lovely, tangible bass that sounds very much like real instruments. They produce excellent punch at low amplifier settings in the small office. Eventually they will be in a room twice the size (circa 3m X 5.5m). If need be I will run a pair of SB Audience Bianco OB 12s or even 15s in H frames off a plate amp to add a bit extra in the larger room.
I've tested them (full range driver only - no passive crossover) with an Arcam A18 (now set to flat) and an AVA Media Maestro 50 that produced great results. As said, the woofers are driven actively so just require slight tweaks with a room/amp change.
First I changed the baffle from pine to a slightly smaller version made from 18mm MDF and 'finished' with self-adhesive vinyl flooring incorporating a 2mm rubber layer - has resulted in much better looking (IMO) speakers that are acoustically more inert.
The most recent step was to add 2 x SB Acoustics SB20PFCR30-8 wired in parallel in each baffle. Myself and my son fitted them on Friday night and they are actively driven (in stereo) and low passed at about 130hz with a 12db slope.
These speakers no longer need any bass support from sealed box woofers and they have a lovely, tangible bass that sounds very much like real instruments. They produce excellent punch at low amplifier settings in the small office. Eventually they will be in a room twice the size (circa 3m X 5.5m). If need be I will run a pair of SB Audience Bianco OB 12s or even 15s in H frames off a plate amp to add a bit extra in the larger room.
I've tested them (full range driver only - no passive crossover) with an Arcam A18 (now set to flat) and an AVA Media Maestro 50 that produced great results. As said, the woofers are driven actively so just require slight tweaks with a room/amp change.
Attachments
Having finished aging the SB20FRPC30-8, I made an air recording of "The Pines of the Appian Way (last 2 minutes) - Eiji Oue".
Compared to the spectrum of the CD source, the sound pressure is at best up to 70Hz, which is the same level as the mid and high range.
The response is up to about 30Hz, but the sound pressure is about -15dB at 45Hz, -20dB at 30Hz, and -30dB at 20Hz.
I think this performance is sufficient for an 8inch full range.
Compared to the spectrum of the CD source, the sound pressure is at best up to 70Hz, which is the same level as the mid and high range.
The response is up to about 30Hz, but the sound pressure is about -15dB at 45Hz, -20dB at 30Hz, and -30dB at 20Hz.
I think this performance is sufficient for an 8inch full range.
The speaker part of my OB project with this driver is finished: I've added an SB Audience Bianco 15OB350 in its own baffle with small side wings. In combination with the existing 'towers' the system fills the room (7m X 3.5m approx) effortlessly.
Bass response is strong and 'large' - to use a car analogy it's like the big driver produces lots of torque. Of course, this all helps higher frequencies too which sound very clean, and natural with excellent tone and body across the frequency range.
Everything is fully active using 5 channels of amplification (stereo amp + 3 desktop sub amps) which I'm sure helps, as does the sensitivity of the driver's.
Bass response is strong and 'large' - to use a car analogy it's like the big driver produces lots of torque. Of course, this all helps higher frequencies too which sound very clean, and natural with excellent tone and body across the frequency range.
Everything is fully active using 5 channels of amplification (stereo amp + 3 desktop sub amps) which I'm sure helps, as does the sensitivity of the driver's.
Attachments
I had the racetrack version of their mid woofers in OBs at some point. Mounted in MTM, where the T was a SB65.
Those racetrack are quite the performers, and I was able to add EQ to get them to reach 40Hz before starting to drop. They never showed any sign of struggling, staying clean and punchy. I believe those SB20 woofers to behave just as good.
Those racetrack are quite the performers, and I was able to add EQ to get them to reach 40Hz before starting to drop. They never showed any sign of struggling, staying clean and punchy. I believe those SB20 woofers to behave just as good.
Many thanks. It has been my first ’full range’ speaker project to date. An OB design mitigated some box speaker design issues but clearly involved its own challenges. Careful choice of woofers and dealing with the bass sections actively helped to address these challenges and the SB seems such a good full range driver that it will happily run full range with no filters or EQ, at least in my application.
I would love to measure the speakers at some point but unfortunately I don’t have any meaningful measurement equipment - just an I-pad app! I might change that at some point. At the moment I just listen to music I know well to set relative levels and when everything becomes a cohesive ‘whole’ tonally with instruments and performers localised and stable in the sound stage then I’m happy.
Perceval, the SB 20s exceeded my expectations. Not only do they visually match the FR (same chassis at least), they have a very natural and full bodied tone which adds real texture to instruments and they also have some punch as well when needed. They are quick in their responses and all for a very reasonable price!
Have you got any kind of crossover between the FR & woofers? I can’t find any info about that from your posts. Or I’m dumb and don’t understand what I’m reading. 🤷♂️
It's a fair question. The FR drivers do not have any crossover at all. When I did my measurements with the app I found that their response only started to drop off below 200hz due to the OB design. Research into OB bass loss indicated that this is correct given the width of this particular baffle. When run on their own they are clearly very bass light. Being an 8 inch driver they don't seem to need any protection from low frequencies (a smaller driver might need this).
The lower woofers have no passive crossover, instead each G2 amplifier has a variable crossover (40 - 300 Hz/12db slope), variable gain (set by dip switches) and adjustable volume. I currently have this set at roughly 150 - 160 Hz so for the SB20s. The Bianco, on its own amp, is currently set at about 55hz but I'm adjusting that.
The advantages of this set-up are:
1) I can adjust things to experiment and also to different rooms and stereo amps powering to FR drivers.
2) no efficiency loss due to a passive network.
3) I'd need to have more knowledge than I do to design a set in stone PR network.
4) any crossover that there is operates low down the fr range.
I considered investing in a mini dsp type set-up (I still might at some point) but, thanks to this particular combination of drivers and the way that OB bass interacts with the room I didn't think it was needed. I also wanted to keep the signal as 'pure' as possible and retain the ability to swap around the stereo amp powering the FR drivers.
Hope that helps.
I have attached an image of the amps. The middle one powers the Bianco. The other two the SB20s. I have also just ordered a high current 12volt power supply so that I could use my Genesis Four Channel Class A/B car amplifier instead. It has LP crossovers up to 200 Hz on all four channels so I will run it in stereo for the SB20S and bridged mono for the Bianco. It also has adjustable gain for front and rear.
The lower woofers have no passive crossover, instead each G2 amplifier has a variable crossover (40 - 300 Hz/12db slope), variable gain (set by dip switches) and adjustable volume. I currently have this set at roughly 150 - 160 Hz so for the SB20s. The Bianco, on its own amp, is currently set at about 55hz but I'm adjusting that.
The advantages of this set-up are:
1) I can adjust things to experiment and also to different rooms and stereo amps powering to FR drivers.
2) no efficiency loss due to a passive network.
3) I'd need to have more knowledge than I do to design a set in stone PR network.
4) any crossover that there is operates low down the fr range.
I considered investing in a mini dsp type set-up (I still might at some point) but, thanks to this particular combination of drivers and the way that OB bass interacts with the room I didn't think it was needed. I also wanted to keep the signal as 'pure' as possible and retain the ability to swap around the stereo amp powering the FR drivers.
Hope that helps.
I have attached an image of the amps. The middle one powers the Bianco. The other two the SB20s. I have also just ordered a high current 12volt power supply so that I could use my Genesis Four Channel Class A/B car amplifier instead. It has LP crossovers up to 200 Hz on all four channels so I will run it in stereo for the SB20S and bridged mono for the Bianco. It also has adjustable gain for front and rear.
Attachments
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Thing is... even though your FR drops at about 200Hz, it doesn't mean that it isn't trying to reproduce lower frequencies.
By adding at the minimum, a cap, you will help it free itself from trying to reproduce the lower frequencies, and it will in turn clean up the performance greatly higher up.
By adding at the minimum, a cap, you will help it free itself from trying to reproduce the lower frequencies, and it will in turn clean up the performance greatly higher up.