Presented below is a new 2-way mini monitor featuring Seas ER18RNX mid-woofer and Scanspeak Discovery D2608/9130 HDS tweeter (formerly Peerless HDS 810921).
ER18 RNX is a paper reed cone 7” mid-woofer from Seas Prestige line. It has a relatively smooth response and mild break-up at 4.5 kHz. It also has a copper sleeve on T-shaped pole piece which translates into lower distortion in the lower midrange. This driver has a good bass extension upto 45 Hz (-3db) in a smallish 14 litre vented enclosure. But this mid-woofer has to be crossed as low as 1600 Hz as distortion of this driver rises above that 1000 Hz. So Scanspeak Discovery HDS tweeter has been selected for the design.
I have used 15 AWG steel laminate for the main woofer inductor and 18 AWG air core elsewhere. All capacitors are polymer based and resistors are metal film type. You can swap R3 and R4 if you find the speakers little bright.
The enclosure is Madisound MD14 back ported with no tweeter offset. The port is 2” flared port 7” long.
You can also build your own enclosure with 1” MDF. External box dimension should be 8.5” (w) x 12” (d) x 16” (h) and the port is to be placed right behind the tweeter.
This is a decent performing mini monitor with good bass extension which generally not found on any loudspeaker of this size. Midrange is nearly as good as my Rediscovery tower. Drivers are relatively cheap. This is a budget high end audio.
ER18 RNX is a paper reed cone 7” mid-woofer from Seas Prestige line. It has a relatively smooth response and mild break-up at 4.5 kHz. It also has a copper sleeve on T-shaped pole piece which translates into lower distortion in the lower midrange. This driver has a good bass extension upto 45 Hz (-3db) in a smallish 14 litre vented enclosure. But this mid-woofer has to be crossed as low as 1600 Hz as distortion of this driver rises above that 1000 Hz. So Scanspeak Discovery HDS tweeter has been selected for the design.
I have used 15 AWG steel laminate for the main woofer inductor and 18 AWG air core elsewhere. All capacitors are polymer based and resistors are metal film type. You can swap R3 and R4 if you find the speakers little bright.
The enclosure is Madisound MD14 back ported with no tweeter offset. The port is 2” flared port 7” long.
You can also build your own enclosure with 1” MDF. External box dimension should be 8.5” (w) x 12” (d) x 16” (h) and the port is to be placed right behind the tweeter.
This is a decent performing mini monitor with good bass extension which generally not found on any loudspeaker of this size. Midrange is nearly as good as my Rediscovery tower. Drivers are relatively cheap. This is a budget high end audio.
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Good work Suman.
I have been looking to build a center channel speaker to match my scanspeak 9900/8530k01 main bookshelf speakers. I am weighing the madisound rediscovery kit (which they pointed me to when I asked for suggestions!) but building it in a sealed md14 box instead of the towers. Since I'm crossing over to a sub around 50Hz I don't need much low end. The reason for the smaller box is that I only have about 9" of height between the screen and stand, so I would lay it on the side.
Even though your Opus Mini is designed from the start for the smaller md14 box, I think I'd prefer going with the rediscovery kit due to the better value and better drivers.
I'm still looking at different options, also considering the Zaph/Madisound sr71 which seems to have more of a following but perhaps not quite as high quality drivers. I'm also considering the parts express Usher based UA701MK kit, but concerned about quality control on those drivers. The advantages of these kits are that baffles are available precut.
What do you think about the idea of building your rediscovery kit in an md14 enclosure instead of the opus mini?
I have been looking to build a center channel speaker to match my scanspeak 9900/8530k01 main bookshelf speakers. I am weighing the madisound rediscovery kit (which they pointed me to when I asked for suggestions!) but building it in a sealed md14 box instead of the towers. Since I'm crossing over to a sub around 50Hz I don't need much low end. The reason for the smaller box is that I only have about 9" of height between the screen and stand, so I would lay it on the side.
Even though your Opus Mini is designed from the start for the smaller md14 box, I think I'd prefer going with the rediscovery kit due to the better value and better drivers.
I'm still looking at different options, also considering the Zaph/Madisound sr71 which seems to have more of a following but perhaps not quite as high quality drivers. I'm also considering the parts express Usher based UA701MK kit, but concerned about quality control on those drivers. The advantages of these kits are that baffles are available precut.
What do you think about the idea of building your rediscovery kit in an md14 enclosure instead of the opus mini?
Building Rediscovery in a 14 litre enclosure (even if sealed) is not a good idea. You can do it 20-22 litre sealed.
SUMAN JANA
Member
Joined 2003
Member
Joined 2003
Hello again. I was just looking at the ReDiscovery at Madisound and I noticed that the crossover that you've come up with for the D2908 is strikingly similar to what I came up with for my speaker a few years back. I used the Peerless 8" HDS woofer instead though which is now NLA.
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Hello,
Why did you choose for the d2608 9130 and not for the ER18DXT (Seas dxt-tweeter) or the Zaph SR71 (Seas 27TDFC) ?
Andréas from France
Why did you choose for the d2608 9130 and not for the ER18DXT (Seas dxt-tweeter) or the Zaph SR71 (Seas 27TDFC) ?
Andréas from France
Old thread, but re:"This driver has a good bass extension upto 45 Hz (-3db) in a smallish 14 litre vented enclosure" - only if you BSC the bejasus out of it & pay with efficiency...
I prefer to add a helper woofer, but then it's not a bookshelf...
I prefer to add a helper woofer, but then it's not a bookshelf...
I would thank you for the response. But the difference between this 3 designs is NOT the midwoofer (Er18rnx) but the tweeter.
Thanks Andréas
Thanks Andréas
Hi Andréas,
Crossing a tweeter at 1.5 kHz is very low and there are not many drivers which really are suitable for. The ScanSpeak D2608/913000 (Peerless HDS 810921) is a very good choice, because it is known for very moderate harmonic distortions below 2 kHz and large excursion capability of +/- 0.5 mm. Whether the Seas 27TBCD/GB/DXT and 27TDFC would do as well is debatable and I don't want to decide on that.
Crossing a tweeter at 1.5 kHz is very low and there are not many drivers which really are suitable for. The ScanSpeak D2608/913000 (Peerless HDS 810921) is a very good choice, because it is known for very moderate harmonic distortions below 2 kHz and large excursion capability of +/- 0.5 mm. Whether the Seas 27TBCD/GB/DXT and 27TDFC would do as well is debatable and I don't want to decide on that.
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Use the notch on the woofer per ER18DXT & you can cross over higher, 2.5KHz works well with Seas 27TBCD
Hello, sure post is six years old but I'm working around these two drivers and I've found it. Please, would you tell me what's the simulator you used? I've made a scratch using Boxsim and using your same crossover schematic and values results are quite different.
Thank you very much.
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