Hello everyone.
A friend of mine owns a pair of Beveridge Model IIIs. He renovated the speakers quite extensively, remade the cardboard bezel, and they work well for the electrostatic part. The woofers, however, were in poor condition, and he had to replace them. He chose - because he did not want to spend too much money without knowing exactly which speakers to replace the originals with - speakers of much lower quality (4 x 10" SKYTRONIC Model 902.214 woofers whose specifications appear below). I picked the T/S parameters for the Skytronics and made a comparison with Dynaudio 24W75 which could be candidates for replacement, see attached file.
Now he would like to replace the Skytronics (equivalent Fenton speakers), because the bass is not as dry, tight and fast as the electrostatic membranes, naturally...
At his request, I made him an active filter kit from Rod Elliott, a Linkwitz-Riley with a slope of 24dB/octave, cutoff at 200Hz as it was originally. The bass channel is driven with a Hafler 220 amp and the ESL is driven by a Luxman tube amp (a kind of Luxman MQ-88uC).
The volume of each bass speaker is approximately 65 liters. For those who are not familiar with the Beveridge model III, each speaker has 2 woofers, one at the bottom which radiates downwards, the other at the top which diffuses towards the ceiling. The enclosure is bulky, high (more than 2m) and wide (a cylinder approximately 60cm in diameter).
As you could expect from an ESL, the mid-high is splendid. By comparison, the bass provided by current speakers is a bit slow and boomy. The speaker load is closed, and occupies a volume of approximately 65 liters per speaker.
I'm not an expert on speaker load calculations.
I would like to know how to proceed with this replacement, if someone has good ideas or experience?
I'm listening to you !
thank you so much.
Skytronic T/S parameters as I could find them (and Dynaudio 24W75):
A friend of mine owns a pair of Beveridge Model IIIs. He renovated the speakers quite extensively, remade the cardboard bezel, and they work well for the electrostatic part. The woofers, however, were in poor condition, and he had to replace them. He chose - because he did not want to spend too much money without knowing exactly which speakers to replace the originals with - speakers of much lower quality (4 x 10" SKYTRONIC Model 902.214 woofers whose specifications appear below). I picked the T/S parameters for the Skytronics and made a comparison with Dynaudio 24W75 which could be candidates for replacement, see attached file.
Now he would like to replace the Skytronics (equivalent Fenton speakers), because the bass is not as dry, tight and fast as the electrostatic membranes, naturally...
At his request, I made him an active filter kit from Rod Elliott, a Linkwitz-Riley with a slope of 24dB/octave, cutoff at 200Hz as it was originally. The bass channel is driven with a Hafler 220 amp and the ESL is driven by a Luxman tube amp (a kind of Luxman MQ-88uC).
The volume of each bass speaker is approximately 65 liters. For those who are not familiar with the Beveridge model III, each speaker has 2 woofers, one at the bottom which radiates downwards, the other at the top which diffuses towards the ceiling. The enclosure is bulky, high (more than 2m) and wide (a cylinder approximately 60cm in diameter).
As you could expect from an ESL, the mid-high is splendid. By comparison, the bass provided by current speakers is a bit slow and boomy. The speaker load is closed, and occupies a volume of approximately 65 liters per speaker.
I'm not an expert on speaker load calculations.
I would like to know how to proceed with this replacement, if someone has good ideas or experience?
- find the exact equivalent
- find a speaker that respects the characteristics of the original speakers
- find nearby speakers, even if it means modifying the cutoff frequency
- the idea is not to remove this bass from the speakers to replace it with an independent subwoofer (solution sometimes recommended)
I'm listening to you !
thank you so much.
Skytronic T/S parameters as I could find them (and Dynaudio 24W75):
Thanks @cvanc, this friend is a very meticulous woodworker... (as a nearly full-time hobby). I'll tell him, he'll be happy 😃
He added to the original 2 small red leds down the speaker to show when they are driven.
You can see on the photo the cabinet he builded himself for his system. All plain walnut.
Nice day!
He added to the original 2 small red leds down the speaker to show when they are driven.
You can see on the photo the cabinet he builded himself for his system. All plain walnut.
Nice day!
Hi there,
Your friend did a great job. I did something similar some time ago with my model III's. Rebuilt the crossover network and reversed a modification from a single Dynaudio 10" woofer that was supposedly a common mod back in the day. The original woofers were 16 ohms in parallel. The only woofers that I could find that met these requirements in recent times were musical instrument woofers from Italian mfr Faital. I ended up doing the math as you did and ended up with a pair of Morel 9" woofers that worked out well.
In the end I abandoned the internal woofers and went with a pair of modern REL subs that significantly improved the performance- as you know you can bypass the internal woofers and used and external setup with the III's. I did try Beveridge's RM3 active crossover with a pair of Roger Modjeski subs- but for me I liked the RELs better. It really is the way to go. You can passively crossover the panels with a small cap on the input to the amp and have the RELs slave to a second amp on the high side from a second output on your preamp.
Further, I ended up abandoning the step up in the Model IIIs and building a direct drive amp for the Model IIIs -- this was a game changer.
I would not entertain the built in subs at all for the IIIs as in this day and age - outboard good quality subs are so much better. YMMV. Good luck.
Your friend did a great job. I did something similar some time ago with my model III's. Rebuilt the crossover network and reversed a modification from a single Dynaudio 10" woofer that was supposedly a common mod back in the day. The original woofers were 16 ohms in parallel. The only woofers that I could find that met these requirements in recent times were musical instrument woofers from Italian mfr Faital. I ended up doing the math as you did and ended up with a pair of Morel 9" woofers that worked out well.
In the end I abandoned the internal woofers and went with a pair of modern REL subs that significantly improved the performance- as you know you can bypass the internal woofers and used and external setup with the III's. I did try Beveridge's RM3 active crossover with a pair of Roger Modjeski subs- but for me I liked the RELs better. It really is the way to go. You can passively crossover the panels with a small cap on the input to the amp and have the RELs slave to a second amp on the high side from a second output on your preamp.
Further, I ended up abandoning the step up in the Model IIIs and building a direct drive amp for the Model IIIs -- this was a game changer.
I would not entertain the built in subs at all for the IIIs as in this day and age - outboard good quality subs are so much better. YMMV. Good luck.
Thanks for your detailed response, @kcin. You're right, 16Ω in // for the 2 original woofers. I'm aware of the Morel speakers quality, even if they're not cheap. Some CAW938 like this one could be a candidate, I thought. Or, as I already mentioned it, a double pair of 24W75 Dyns (I've got one pair in stock that would reduce the difficulty to find them all).
I agree with the REL sub bass speakers, they're really good. I've got 2 small Quake myself, which sound great with my small pair of Apogee Centaur Minor. But my friend would like to use the IIIs as they are, and also the room is not so big nor practical to add 2 more speakers !
Well, we'll go on talking about the different possibilities. Maybe he'll need first to go through the steps you took yourself, and try a double pair of good woofers before going later to subbass external speakers... Versus the old configuration (2 amps with the passive internal crossover), the active crossover (and the same 2 dedicated amplifiers) already brought, to my ears, some improvement in clarity and musical scene presentation (both width and deepness). We parted the right speaker from the wall at the same time so I'm unsure which change added some benefit to our perception.
Indeed, very pleasant speakers to hear anyway. I had some Audiostatics 300 a long time ago (still have them but they they need new mylar foils) and it reminded the ESL airy and imaging quality of the foils they had.
Enjoy!
I agree with the REL sub bass speakers, they're really good. I've got 2 small Quake myself, which sound great with my small pair of Apogee Centaur Minor. But my friend would like to use the IIIs as they are, and also the room is not so big nor practical to add 2 more speakers !
Well, we'll go on talking about the different possibilities. Maybe he'll need first to go through the steps you took yourself, and try a double pair of good woofers before going later to subbass external speakers... Versus the old configuration (2 amps with the passive internal crossover), the active crossover (and the same 2 dedicated amplifiers) already brought, to my ears, some improvement in clarity and musical scene presentation (both width and deepness). We parted the right speaker from the wall at the same time so I'm unsure which change added some benefit to our perception.
Indeed, very pleasant speakers to hear anyway. I had some Audiostatics 300 a long time ago (still have them but they they need new mylar foils) and it reminded the ESL airy and imaging quality of the foils they had.
Enjoy!
Thanks @kcin. You mean that before having the Morels in the Bev the woofers in place were the Dyns? I'm not fully fluent in English so I'm unsure I understand well, sorry for that.
And yes you're right, he placed his Bev the conventional way (read conventional for speakers). But his room is not the most suitable for listening anyway... and he could not place them on wall sides in direction to the listener's ears. So they remain. We improved a little bit by separating one of them from the wall to which it was against (and more important, from the corner). We'll see how this could be improved... moving maybe? 🤔
And yes you're right, he placed his Bev the conventional way (read conventional for speakers). But his room is not the most suitable for listening anyway... and he could not place them on wall sides in direction to the listener's ears. So they remain. We improved a little bit by separating one of them from the wall to which it was against (and more important, from the corner). We'll see how this could be improved... moving maybe? 🤔
@perelman your English is far better than my French! We are taught Quebecois French here in Canada- it is an official language-- until Grade 8 then it is voluntary in high school and beyond. I am afraid I still am not very fluent.
Yes , sometime ago there was a modification where 1 Dynaudio woofer in the top position was used and there were holes bored through the internal cabinet structure to allow the volume of air to be continuous from top to bottom in the woofer chamber. Conventionally, there are two separate chambers , one for the top woofer and one for the bottom in a hemholtz configuration. I reversed this modification and used two Morels as noted. Finally, I adopted 2 separate REL S3 subs.
Yes , sometime ago there was a modification where 1 Dynaudio woofer in the top position was used and there were holes bored through the internal cabinet structure to allow the volume of air to be continuous from top to bottom in the woofer chamber. Conventionally, there are two separate chambers , one for the top woofer and one for the bottom in a hemholtz configuration. I reversed this modification and used two Morels as noted. Finally, I adopted 2 separate REL S3 subs.
