I've been kind of tossing around in my head the idea of doing a speaker project "inspired by..." the Harbeth 40.1.
At present I have a pair of Rogers LS7T speakers that I like rather a lot, except that their low frequency output can't really keep up with the dynamics they're able to reproduce in the mids and highs.
Rogers Speakers - Rogers LS7
Rather than do the sensible thing and add a pair of subwoofers, I was thinking of harvesting the drivers from the Rogers, adding a 12" woofer, and putting them all in new boxes. A 12" + 8" + dome is the same format as the Harbeth Monitor 40.1, a speaker I happen to admire very much, although its price, even used, is far beyond my means.
I'm thinking that one of the 12" woofers from the Seas/Scan/Vifa/Tymphany/Peerless/SB family of drivers ought to fit the plan. (I'm not fishing for you guys to do my homework and pick one for me... 🙂)
I know I won't be able to just plop the Rogers crossovers into a new system and expect it to work. For one thing the wider baffle will require different baffle step compensation. I do have some ability to make measurements, since I run SmaartLive at my "day job".
The Monitor 40.1 cabinet dimensions are 750mm H X 432mm W X 400mm D (approx. 29.5" x 17" x 15.75"). I imagine I'd copy the height and width, and let the depth fall wherever the woofer's volume requirements take me. One thing that concerns me is that the Rogers are rated at 88dB/1W/1M sensitivity; the Harbeths are rated at 84dB, so a 12" woofer that would match the Rogers drivers' sensitivity would likely require a larger enclosure. I might be better off looking at 10" units?
I could also be convinced to abandon the idea of trying to re-use the Rogers components and just start with all-new stuff.
Anyway I just wanted to throw these ideas out there, comments and criticism are welcome.
At present I have a pair of Rogers LS7T speakers that I like rather a lot, except that their low frequency output can't really keep up with the dynamics they're able to reproduce in the mids and highs.
Rogers Speakers - Rogers LS7
Rather than do the sensible thing and add a pair of subwoofers, I was thinking of harvesting the drivers from the Rogers, adding a 12" woofer, and putting them all in new boxes. A 12" + 8" + dome is the same format as the Harbeth Monitor 40.1, a speaker I happen to admire very much, although its price, even used, is far beyond my means.
I'm thinking that one of the 12" woofers from the Seas/Scan/Vifa/Tymphany/Peerless/SB family of drivers ought to fit the plan. (I'm not fishing for you guys to do my homework and pick one for me... 🙂)
I know I won't be able to just plop the Rogers crossovers into a new system and expect it to work. For one thing the wider baffle will require different baffle step compensation. I do have some ability to make measurements, since I run SmaartLive at my "day job".
The Monitor 40.1 cabinet dimensions are 750mm H X 432mm W X 400mm D (approx. 29.5" x 17" x 15.75"). I imagine I'd copy the height and width, and let the depth fall wherever the woofer's volume requirements take me. One thing that concerns me is that the Rogers are rated at 88dB/1W/1M sensitivity; the Harbeths are rated at 84dB, so a 12" woofer that would match the Rogers drivers' sensitivity would likely require a larger enclosure. I might be better off looking at 10" units?
I could also be convinced to abandon the idea of trying to re-use the Rogers components and just start with all-new stuff.
Anyway I just wanted to throw these ideas out there, comments and criticism are welcome.
I'll be following this closely, I've been flirting with the idea of trying a classic 3 way like this. I think it would be fun to try. I've got some old kenwoods that came from japan in the 70's that I use in the garage where I do my building and every time I see them I get the idea of making a more modern version with a proper crossover.
That 40.1 looks like a great speaker and the reviews seem positive, but $13,000? I expected to see diamond rings taped to the driver magnets on the internal picture. Are the crossover coils made of solid gold?
That 40.1 looks like a great speaker and the reviews seem positive, but $13,000? I expected to see diamond rings taped to the driver magnets on the internal picture. Are the crossover coils made of solid gold? 
If that pic is yours (is that your new speaker?), do you have the 12" already? Good/nice project, but you will be scraping the Rogers 🤐. Do you like the sound of the 8" driver for a keep, instead of buying new drivers.(?)
There are nice 10" (not many...). But if the Harbeth Monitor 40.1 is a 12" I would go with that idea. I have a diy speaker with a 10", but it plays with a 5" mid.
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All pictures are "found on the internets".
I do have a pair of Rogers LS7Ts just like the ones in the picture. And IF I harvest drivers from them, I'll not scrap anything or do any irreversible damage, 'cause if I do the project and it doesn't turn out well, I can always put the Rogers back together.
No I don't have the 12"s yet.
Interesting how Harbeth recesses their mid unit, very odd .........
I think it had to do with the way the original mid mounted tothe cabinet for the LS5/3A combo. It was a front-gasket design. Looks appeal, and I bet it was continued for that reason alone.
Later,
Wolf
Interesting how Harbeth recesses their mid unit, very odd .........
I've never understood why, but all the BBC monitor speakers had rear-mounted woofers, and Harbeth have continued that feature with their Monitor series. The Compact 7 and HL5 have front-mounted woofers though, and I think these two models, along with the Monitor 30, share the same 8" woofer, which is also used as the mid in the Monitor 40.
Spendor, who also come from a BBC background, rear-mount some of their woofers and front-mount others. And Rogers used a similar 8" poly to mine in their Studio 1 speaker, rear-mounted, whereas my LS7s are front-mounted. I would think there would be measurable diffraction from that step-back, but who knows?
Wow, take a pretty good size space to do those justice. Probably a $2,000 project.
I always preferred two way designs because they seemed more crisp and coherent to my ears. Be fun to hear those...........nice of them to share all that r & d with the DIY community.
![IMGDEAD]](https://www.diyaudio.com/forums/[IMGDEAD]http://i61.tinypic.com/xkzlvd.jpg[/IMGDEAD])
Re:"I might be better off looking at 10" units?" - cabinet size starts to get tooo big once you get past 10"... It sound like you just need a bit more bass oomph, the easiest way is to add .5 way woofers (make them as stands for the existing boxes). The key decision is sensitivity of the drivers (if you're not bi-amping), for .5 way woofers you'd need them to match the existing Rogers woofers, if you plan to go the full 3 way hog, you'd need to pick drivers that are ~ 3dB more sensitive
The 12" woofer Harbet used was a Vifa M30 model, but I think thy have switched supplier now or builds it in-house now.
Close enough, but probably better (the PRELUDE, that is). Only difference is the cabinets. Harbeth use thin-wall cabinets.
It was a fun build. Will be activated very soon. No passive will ever see the inside of theses boxes. Used 10" Seas Prestige and is tuned for 34. I'm not a big forum person anymore. Do everything on my HI-FI FB nut groups.
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