So I've been looking into building a pair of tower speakers, and have been primarily focused on the Scanspeak Reference Plus, as seen here:
I've just a few questions, if there is anyone here who happens to have any experience with this speaker, or knows any of the specs:
I've read on the forum that the impedence of this speaker can dip below 3 Ohms, can anyone confirm this? I did a search for impedence curves but couldn't find anything.
Also, the schematic for the crossover includes an "optional" LRC in the crossover section for the woofer:
Audio Components - Scan-Speak - Reference Line
Does anyone know what the purpose of the optional LRC is, and what effects it will have acoustically?
I'm planning on doing a build of this speaker, hopefully beginning within the next few weeks. Will be modifying the cabinet purely for asthetic reasons - I want to do a curved cabinet build, would also like to make the baffle completely vertical instead of being tilted (I've read that the sonic differences may be undetectable, but am not completely sure if this is true). I also plan on trying different baffles - the speaker plan has one with rounded corners, I'd like to try one the same size but with square corners and see if I can detect the difference.
This will be my first speaker build so any suggestions or comments on the hardware are welcome. The speakers will be used primarily for music but also for HT.
An externally hosted image should be here but it was not working when we last tested it.
I've just a few questions, if there is anyone here who happens to have any experience with this speaker, or knows any of the specs:
I've read on the forum that the impedence of this speaker can dip below 3 Ohms, can anyone confirm this? I did a search for impedence curves but couldn't find anything.
Also, the schematic for the crossover includes an "optional" LRC in the crossover section for the woofer:
Audio Components - Scan-Speak - Reference Line
Does anyone know what the purpose of the optional LRC is, and what effects it will have acoustically?
I'm planning on doing a build of this speaker, hopefully beginning within the next few weeks. Will be modifying the cabinet purely for asthetic reasons - I want to do a curved cabinet build, would also like to make the baffle completely vertical instead of being tilted (I've read that the sonic differences may be undetectable, but am not completely sure if this is true). I also plan on trying different baffles - the speaker plan has one with rounded corners, I'd like to try one the same size but with square corners and see if I can detect the difference.
This will be my first speaker build so any suggestions or comments on the hardware are welcome. The speakers will be used primarily for music but also for HT.
Hi Ephai, the lower woofer is crossed over at a low frequency. The filter is acting close to the woofers natural low end cut off and the woofer is electrically behaving badly at that point (like all do). The LCR is to ensure that the effect isn't passed on to the crossover filter.
The reality may be different when you consider that the low frequencies involved are being dominated by the room, and not the speaker....
I suspect that if you tried a plain baffle, and then covered it with carefully positioned damping material, you'd find almost the same differences.
The sloped baffle is there to time align the drivers so phase is kept in check on each. It may be the xover is also accomodating the intentional sloping; so be careful with your vertical BB idea if intending to employ the xo shown at the SS site.
I don't have experience with the whole speaker, but know the single drivers pretty well. It's basically a 2-way system, with an integrated subwoofer.
The tweeter is already a veteran, but a good one. The upper bass is also quite "old", but has a smooth warm midrange, precise.
As said, the lower bass is a "subwoofer", and is cut fairly low. Means the XO frequency is close to the drivers Fs in its enclosure (it's higher than freefield), and with the impedance peak the 15mH inductor has an interaction with the high impedance at Fs. The result is that the low pass doesn't cut properly at the desired frequency, and even boosts the frequencies around 80-100Hz, which results in a boomy (upper) bass. IMO I would consider the LCR not as an option but as a necessary integrated element. If the bass is then too tight, you may vary the 3.9 ohms resistor to a higher value, there is no harm to the sound or speaker.
I'd keep the baffle tilted - helps the phase group response. The rounded corners generally are helpful to avoid diffractions from the tweeter, but since the tweeter has a concave shaped metal front, and the dome itself is recessed, this tweeter is less sensitive to corner perturbances than its "smaller" brother, the D2905/9700 for instance, with its a totally plane surface.
Some tipps: the 2.2mH is quite high value, somewhat typical for Dutch or German designs, don't hesitate to go down to 1.8mH for a more forward (or less laid back) midrange. Also, 3.9µF is a small value; I used to filter the 9900 with 8.2µF and 0.22mH on the same 18W8546.
Good choice of a speaker and drivers though!
Have fun
- daniel
Thanks for all of the replies, a lot of great info here. 🙂
I see, so the purpose of the optional LCR would be to smooth out the driver's impedance curve near the crossover point. Thanks again for the info here, Allen's crossover sticky was very helpful in gaining a basic understanding of crossover design.
Alfetta - thanks for the info on capacitor / inductor values, I will definitely be doing some experimentation here.
I'm not quite sure yet about what to do about the slanted baffle. As stated, the desire for a completely vertical baffle is purely for looks - and with curved cabinet sides it would simplify the construction. Dublin's idea of attaching the speakers to stands may be my best option here.
Then if I ever decide to go with an active set up, I can just remove the stands and use the active crossovers to do the time alignment. 😀 (though I might be getting in a bit over my head here)
On the overall impedance of the set up - could I just construct an impedance curve with Excel, using the standard formulas for Z and the impedance curves of the individual drivers? Or is this not worth my time?
I have 2 amps available to drive the speakers. One is an Adcom GFA-555 (200W x 2 @ 8 Ohms). It is stable down to 4 Ohms in stereo but below that I'm not sure. Otherwise I have a Butler Audio TDB 2150 (car audio amplifier, 150W x 2 @ 4 Ohms). The Butler is stable down to 2 Ohms stereo, if required.
Thanks again for any replies. I'm a noob so forgive me, I've probably got some cocamamie ideas here. 😀
I see, so the purpose of the optional LCR would be to smooth out the driver's impedance curve near the crossover point. Thanks again for the info here, Allen's crossover sticky was very helpful in gaining a basic understanding of crossover design.
Alfetta - thanks for the info on capacitor / inductor values, I will definitely be doing some experimentation here.
I'm not quite sure yet about what to do about the slanted baffle. As stated, the desire for a completely vertical baffle is purely for looks - and with curved cabinet sides it would simplify the construction. Dublin's idea of attaching the speakers to stands may be my best option here.
Then if I ever decide to go with an active set up, I can just remove the stands and use the active crossovers to do the time alignment. 😀 (though I might be getting in a bit over my head here)
On the overall impedance of the set up - could I just construct an impedance curve with Excel, using the standard formulas for Z and the impedance curves of the individual drivers? Or is this not worth my time?
I have 2 amps available to drive the speakers. One is an Adcom GFA-555 (200W x 2 @ 8 Ohms). It is stable down to 4 Ohms in stereo but below that I'm not sure. Otherwise I have a Butler Audio TDB 2150 (car audio amplifier, 150W x 2 @ 4 Ohms). The Butler is stable down to 2 Ohms stereo, if required.
Thanks again for any replies. I'm a noob so forgive me, I've probably got some cocamamie ideas here. 😀
Hello, at the beginning I would like to say hi, my name is Artur and I am new to this forum. I have completed both projects - Scan Speak reference monitor and reference plus. Very good drivers were used in these projects. The 2905/9900 is one of the best tweeters ever made. Kevlar midbass 8546-01 gives a very sweet sound, in my opinion it is even better than 8545-00, although a bit more difficult to apply. The 8545 is a loudspeaker used in many projects by builders around the world. In this particular application it is cut very low and acts as a subwoofer. At this volume it gives very low bass and a good impulse response. So the speakers are great, but the crossover is terrible! Both the Scan Speak reference Monitor and Reference Plus have a very recessed midrange, and the treble is definitely too loud and tiring for the ears. I took a long time to fine-tune the crossover, and had to make a few modifications for all drivers. I would like to share my experience with people who are going to build these speakers.
2.2 mH for the voice coil is way too high, so the sound is recessed. I tried with lower values and in the end I got the best result with a 1.8 mH coil and a 5.6 Ohm resistor in parallel.
As for the Revelator, a slight modification also should also be made here. The 3.9uF capacitor is far too low. 4.7 uF should be used and the 0.82 mH coil should be replaced by 0.56 mH. This speaker sounds way too loud, so the 4.7 Ohm resistor should be replaced with a 5.6 Ohm resistor.
In the case of reference plus you also need to modify the crossover for the woofer. As mentioned above, the LCR filter is a must-have for the 8545-00, otherwise the upper bass is a bit too loud. However, with this filter there is not enough bass for my taste. Fortunately, scan-speak has made a new version of this driver with kapton. It is marked 8545-K00 and its impedance curve is much more friendly. It can be used without an LCR filter and then it shows what it can do. This is a great bass driver, I do not know a better 18cm that would produce such excellent bass. I hope you find this information useful.
Best Regards,
Artur
2.2 mH for the voice coil is way too high, so the sound is recessed. I tried with lower values and in the end I got the best result with a 1.8 mH coil and a 5.6 Ohm resistor in parallel.
As for the Revelator, a slight modification also should also be made here. The 3.9uF capacitor is far too low. 4.7 uF should be used and the 0.82 mH coil should be replaced by 0.56 mH. This speaker sounds way too loud, so the 4.7 Ohm resistor should be replaced with a 5.6 Ohm resistor.
In the case of reference plus you also need to modify the crossover for the woofer. As mentioned above, the LCR filter is a must-have for the 8545-00, otherwise the upper bass is a bit too loud. However, with this filter there is not enough bass for my taste. Fortunately, scan-speak has made a new version of this driver with kapton. It is marked 8545-K00 and its impedance curve is much more friendly. It can be used without an LCR filter and then it shows what it can do. This is a great bass driver, I do not know a better 18cm that would produce such excellent bass. I hope you find this information useful.
Best Regards,
Artur
Hello Artur, wecome to the forums and thank you for the information. As this is an older thread, it's uncertain when the responses will come and the thread starter hasn't been by in a while.
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Thank you very much. However, These speakers sound much better than they look. It's really worth building them !
