Some time ago I bought some SB drivers to build a small, high quality 2-way box with them.
They are the SB sb29rdnc-c000-4:
http://www.madisound.com/store/manuals/SB29RDCN-C000-4.pdf
and the SB sb12nrx25:
http://www.madisound.com/store/manuals/4_SB12NRX25-4.pdf
My idea was to use them to replace the drivers on an existing 2-way Sony back vented box, measuring 220mm H x 150mm W x 250mm.
The original mid-bass driver's rubber surround cracked, and I had no way to repair that where I live, in Brazil.
For now it's using an excellent Vifa mid-bass, but I would like to try an "all SB" project with above drivers.
Are there any DIY projects around using these drivers?
I don't have any simulation programs to load the driver's data in and have some idea on volume and theoretical xover. For the latter I wouldn't like nothing over 2nd order.
Would anyone like to try it?
They are the SB sb29rdnc-c000-4:
http://www.madisound.com/store/manuals/SB29RDCN-C000-4.pdf
and the SB sb12nrx25:
http://www.madisound.com/store/manuals/4_SB12NRX25-4.pdf
My idea was to use them to replace the drivers on an existing 2-way Sony back vented box, measuring 220mm H x 150mm W x 250mm.
The original mid-bass driver's rubber surround cracked, and I had no way to repair that where I live, in Brazil.
For now it's using an excellent Vifa mid-bass, but I would like to try an "all SB" project with above drivers.
Are there any DIY projects around using these drivers?
I don't have any simulation programs to load the driver's data in and have some idea on volume and theoretical xover. For the latter I wouldn't like nothing over 2nd order.
Would anyone like to try it?
Jeff Bagby designed the Sopranos which use the same woofer and the SB Acoustics SB26STCN tweeter. I had the SB29RDCN tweeter and asked him whether that tweeter could be used instead of the SB26STCN. Here was Jeff's response:
"If you want to use the SB29RDCN you are welcome to do so. To see the difference I switched out the SB29's in my Piccolos for the SB26 (yes, they do fit the exact same recess) and compared the response curves with the same crossover. To my surprise, their response curves were nearly identical except that the SB29RDCN was about 2-2.5dB more sensitive. Otherwise, the crossover summation and phase tracking was pretty much exactly the same. Part of the reason is because on an infinite baffle these are both fairly flat tweeters with a little lift at the top, and on the same baffle the diffraction response and its peak is the same too, so the same crossover slope and point work about the same.
If you want to build this design and substitute the SB29 then you will need to pad the tweeter down a couple of dB. One simple way to do this would be to simply add a 10 -15 Ohm resistor in parallel with the tweeter after the series resistor. However, you may want to play around with it to get the exact balance that sounds right you."
I never did build the modified version with the SB29, but it should work with Jeff's proposed modification. Here's the information on the sopranos: LINK
"If you want to use the SB29RDCN you are welcome to do so. To see the difference I switched out the SB29's in my Piccolos for the SB26 (yes, they do fit the exact same recess) and compared the response curves with the same crossover. To my surprise, their response curves were nearly identical except that the SB29RDCN was about 2-2.5dB more sensitive. Otherwise, the crossover summation and phase tracking was pretty much exactly the same. Part of the reason is because on an infinite baffle these are both fairly flat tweeters with a little lift at the top, and on the same baffle the diffraction response and its peak is the same too, so the same crossover slope and point work about the same.
If you want to build this design and substitute the SB29 then you will need to pad the tweeter down a couple of dB. One simple way to do this would be to simply add a 10 -15 Ohm resistor in parallel with the tweeter after the series resistor. However, you may want to play around with it to get the exact balance that sounds right you."
I never did build the modified version with the SB29, but it should work with Jeff's proposed modification. Here's the information on the sopranos: LINK
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There is a link in post #2 but here's another:
Various loudspeaker design suggestions
Jeff does hang out at techtalk.parts-express and meniscusaudio forums but he was very ill after a transplant which had complications. I've heard that he is recovering well so best left alone. Someone on those forums may be able to help you but his documentation has all the details and there's good advise on the tweeter swap in post #2.
Various loudspeaker design suggestions
Jeff does hang out at techtalk.parts-express and meniscusaudio forums but he was very ill after a transplant which had complications. I've heard that he is recovering well so best left alone. Someone on those forums may be able to help you but his documentation has all the details and there's good advise on the tweeter swap in post #2.
The Sopranos look exactly what I was looking for. Great suggestion!
I will try a closed box version, as I don't believe in ported speakers for DIY.
In fact the Sopranos is almost the same size as the speaker I want to replace. I may even try the speakers on that box, before building a new one.
Need to get the xover parts though. I would prefer to use an air-core inductor instead of the iron-core one Jeff proposes.
What's Bagby?
I will try a closed box version, as I don't believe in ported speakers for DIY.
In fact the Sopranos is almost the same size as the speaker I want to replace. I may even try the speakers on that box, before building a new one.
Need to get the xover parts though. I would prefer to use an air-core inductor instead of the iron-core one Jeff proposes.
What's Bagby?
Building it sealed will make it tonally unbalanced as you will lose the lower octave and get little below 100 Hz. The EBP for the driver shows it works best in a vented box.
It would sound very thin and light as you would only get upper bass but you could add a sub to get the missing lower end.
It would sound very thin and light as you would only get upper bass but you could add a sub to get the missing lower end.
I looked better at the crossover photo, and Jeff used a 15 watt for the 2.0 ohm and 10 watt for the 6.2 ohm resistors.
Now I'm trying to find these parts, on eBay if possible.
I am also considering a different approach. I bought this class D power amp, which is being very praised for its audio quality:
TPA3116 HIFI Class 2.0 Stereo Audio Digital Amplifier Advanced 2X50W Breeze Amp 656112245688 | eBay
They are small and affordable, so why not assemble an active system using one amp for each 2-way speaker?
My idea is not to use an active crossover before the amp, but use discrete parts at each amp input, as high pass and low pass filters, to feed bass-mid and tweeter drivers.
Then I can compare how they both sound.
What do you think of the idea?
Now I'm trying to find these parts, on eBay if possible.
I am also considering a different approach. I bought this class D power amp, which is being very praised for its audio quality:
TPA3116 HIFI Class 2.0 Stereo Audio Digital Amplifier Advanced 2X50W Breeze Amp 656112245688 | eBay
They are small and affordable, so why not assemble an active system using one amp for each 2-way speaker?
My idea is not to use an active crossover before the amp, but use discrete parts at each amp input, as high pass and low pass filters, to feed bass-mid and tweeter drivers.
Then I can compare how they both sound.
What do you think of the idea?
A 15W resistor is overkill, even 10W could be. I'd buy 10W ones and forget about them.
My main problem with the Sopranos crossover is that it uses some components pretty impossible to find, at least here in EU, as they are not part of the standard 12 value series.
The 6R2 value could be obtained with 2x 12R in parallel, the 2R could be substituted by a 2R2 one, or by 2x 1R in series if you're nitpicking, while the 0.35mH coil is a little on the high side to be easily substituted by a 0.33mH one.
For the bigger coil you could use an air core instead of an iron core, but in order to have a similar small DCR an air core would be very big and thus expensive (1.4 or 1.6 mm wire). You won't easily fit this half Kg monster in that small cab.
And about your last idea, you can create an active crossover (*) if you are able to replicate the filter transfer functions that you can find here, just before the crossover schematic: Introducing the Sopranos - Meniscus Audio Forum
I bet you'll have a hard day to replicate the transfer functions only with discrete components.
Ralf
(*) DSP or discrete, if you are filtering before the amplifier then it is an active crossover
My main problem with the Sopranos crossover is that it uses some components pretty impossible to find, at least here in EU, as they are not part of the standard 12 value series.
The 6R2 value could be obtained with 2x 12R in parallel, the 2R could be substituted by a 2R2 one, or by 2x 1R in series if you're nitpicking, while the 0.35mH coil is a little on the high side to be easily substituted by a 0.33mH one.
For the bigger coil you could use an air core instead of an iron core, but in order to have a similar small DCR an air core would be very big and thus expensive (1.4 or 1.6 mm wire). You won't easily fit this half Kg monster in that small cab.
And about your last idea, you can create an active crossover (*) if you are able to replicate the filter transfer functions that you can find here, just before the crossover schematic: Introducing the Sopranos - Meniscus Audio Forum
I bet you'll have a hard day to replicate the transfer functions only with discrete components.
Ralf
(*) DSP or discrete, if you are filtering before the amplifier then it is an active crossover
You are right about the resistors: both can be 10W. The .35mH coil I found on eBay. The 1.2mH air core is a bit expensive on eBay, but I found it cheaper in India, and not so large: 25 mm H x 54 mm D. Resistance is 0.5 ohm though.
At UK's Falcon Audio they have an affordable and small 1.2mH ferrite core type:
Audio Crossover Inductor 1.01mH - 1.20mH HP071 from Falcon Acoustics, The Leading Supplier of DIY Hifi Components.
No DSP for me, just resistors and capacitors. I'll probably have help from a professional speaker designer friend of mine for designing the active filter. If not I'll just go with the passive xover.
I was speaking of air core coils with the low DCR required. Those are really huge and expensive. If you plan to use a higher DCR coil you should also use a different resistor in the tweeter path.
I don't know about you, but for me the main cost problem is the shipping. So I try to buy from one single shop.
I'm not trying to discourage you from the active path, but you should consider those facts: you have a speaker designed by a very competent guy, IMHO it will be very hard to come to a different and better outcome. Besides that the filter transfer functions needed aren't really straight ones, I don't think you can replicate them without DSP. For me the only sensible path is to build the speaker with the correct passive components.
Ralf
I would need more curves to learn more about the speakers, and SB does not provide phase curves, for instance. They are essential for designing the active filter.
Measurements from the speakers on the actual box used are also essential. The mfg FR curves do not mean much.
I wonder if someone, from Voice Coil for instance, did test and measure these speakers.
Measurements from the speakers on the actual box used are also essential. The mfg FR curves do not mean much.
I wonder if someone, from Voice Coil for instance, did test and measure these speakers.
All you need are the transfer functions if you're trying to duplicate Jeff's cross over with a low level (before amp version) crossover. As Ralf said, it's much easier to duplicate transfer functions with DSP, but it can be done with passive components.
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