PBC mounting
I decided to use the EAR flexible standoffs instead of aluminum, I thought effect of expansion/contraction would be nil. They were only $2 each on a non audiophile site. I know Al know standoffs are only $0.36 each but I'm havin fun. I'll be soldering tomorrow.
Oh, I'm using a crosswise and front to back brace. I happen to have round 3/8" Dia. steel rod and it will be perfect. I'll mill a small channel were they cross so both will be in contact with the bottom panel. No tiny L brackets to deal with.
I decided to use the EAR flexible standoffs instead of aluminum, I thought effect of expansion/contraction would be nil. They were only $2 each on a non audiophile site. I know Al know standoffs are only $0.36 each but I'm havin fun. I'll be soldering tomorrow.
Oh, I'm using a crosswise and front to back brace. I happen to have round 3/8" Dia. steel rod and it will be perfect. I'll mill a small channel were they cross so both will be in contact with the bottom panel. No tiny L brackets to deal with.
Fun is important.
Dang! I've never had anyone reinforce a chassis with rebar before. I guess there's a first for everything.
Since you appear to be into over-engineering and have access to a milling machine, you could mill an ISO grid bottom from a chunk of aluminum. Just saying...
Tom
My shop
I can make just about anything. My shop includes a large Bridgeport milling machine, three lathes, vertical and horizontal saws and precision inspection equipment including a granite surface plate flat w/in .00005. There is also a 2 ton and 12 ton press and an assortment of other equipment. My stock runs from Al to Zr.
I was an approved vendor making aerospace parts for a short while. That was no fun...I might as well have not been retired. I stopped doing work for large companies.
I had set up my shop after I retired and have designed and made custom parts for everything from Corvettes to Harleys. I've repaired/restored antiques, jewelry, equipment for tree service companies and many other types of equipment. I'll make almost anything. I also will make dimensional drawings and help with patent ideas. I can also make very small parts.
I can make just about anything. My shop includes a large Bridgeport milling machine, three lathes, vertical and horizontal saws and precision inspection equipment including a granite surface plate flat w/in .00005. There is also a 2 ton and 12 ton press and an assortment of other equipment. My stock runs from Al to Zr.
I was an approved vendor making aerospace parts for a short while. That was no fun...I might as well have not been retired. I stopped doing work for large companies.
I had set up my shop after I retired and have designed and made custom parts for everything from Corvettes to Harleys. I've repaired/restored antiques, jewelry, equipment for tree service companies and many other types of equipment. I'll make almost anything. I also will make dimensional drawings and help with patent ideas. I can also make very small parts.
Tom,
First of all I don't think of 3/8" Dia. rod as rebar. I just happen to have quite a bit and no small L brackets or small Al channel material. 15 minuets to mill the small recesses and drill the holes. Easy and I like using what I have in stock.
kevinahcc20, what would you use? Or do you think the 1/4" sag is nothing to be concerned about?
First of all I don't think of 3/8" Dia. rod as rebar. I just happen to have quite a bit and no small L brackets or small Al channel material. 15 minuets to mill the small recesses and drill the holes. Easy and I like using what I have in stock.
kevinahcc20, what would you use? Or do you think the 1/4" sag is nothing to be concerned about?
No worries, man. I just couldn't get the image out of my mind.
Is any of your gear CNC controlled?
Tom
I started the shop with a small German lathe, a drill press and horizontal/vertical bandsaw about 12 years ago. I got tired of kneeling on the cellar floor or in the driveway with a hand saw or electric drill when things needed repairing. When that wasn't enough I would go to small local machine shops.
Ten years ago I decided to enlarge and, besides making a little cash, I've fixed more things for myself than I can count. No more production type work/deadlines and its fun.
Ten years ago I decided to enlarge and, besides making a little cash, I've fixed more things for myself than I can count. No more production type work/deadlines and its fun.
And the joy of working with ones hands. Something wonderfully meditative about that.
Can I ask for an opinion on if this amplifier would be an ideal amp to power my dads Magnaplanar mgIIIa speakers?
I'm thinking of doing him something nice and building him an amp for his speakers. He has an old crappy amp imho and I would like to build something and put it in a great chassis too. This amp has my interest and would like to hear some opinions on pairing it with a pair of Maggie's. The mgIIIa recommends 100wrms @8ohms.
No less than 50wrms @8ohms, and max of 200wrms @8ohm.
My gut is telling me yes. And if so, would one for ea speaker be sufficient, and will the psu power two? I looked at someone's build and it appears that is the case. I think I can afford this, depending on cost of the BOM for each build.
Thanks to those who can offer some advice and opinions !!!
I'm thinking of doing him something nice and building him an amp for his speakers. He has an old crappy amp imho and I would like to build something and put it in a great chassis too. This amp has my interest and would like to hear some opinions on pairing it with a pair of Maggie's. The mgIIIa recommends 100wrms @8ohms.
No less than 50wrms @8ohms, and max of 200wrms @8ohm.
My gut is telling me yes. And if so, would one for ea speaker be sufficient, and will the psu power two? I looked at someone's build and it appears that is the case. I think I can afford this, depending on cost of the BOM for each build.
Thanks to those who can offer some advice and opinions !!!
I'm not familiar with that model Maggie, but I do have a set of Mini-maggies on my desk-top. I can't speak directly to the suitability of the Mod86, but what I do know is I had to swap out my Parasound HCA-1000A (200 Wrms into 4 ohms continuous, 45 Amp peak per channel, 775 VA toroid) for a Krell KAV-500 (240 Wrms into 4 ohms with a 1KVA toroid). The Parasound kept going into protect mode (shutdown) on loud passages.
The User's Guide for the Magnaplanar MG III A can be found here (.pdf).
I skimmed through the manual and found warnings about the fragile tweeter section. It appears it's protected by a 2.5 A fuse. The Modulus-86 can deliver at least 7 A, so it would appear to have plenty of power.
Also note that the drivers are specified as purely resistive. 4 Ω for the bass and 3 Ω for the tweeter. 3 Ω is pushing it on the MOD86, but from what I've seen in the lab, the MOD86 will be able to drive it.
At 83 dB SPL (1 W, 1 m) the Magnaplanar are not efficient. Still with 65 W into 4 Ω, the MOD86 provides enough power to hit over 100 dB SPL at 1 m.
I would build two amps per speaker. One for the woofer and one for the tweeter. You can drive them from one Power-86. I'm using one Power-86 to power four MOD86 boards in my amp for my LXmini speakers. If you choose to go that route, I'd get a 300 VA transformer (Antek AS-3222 would be perfect).
Tom
I would not use the minimum recommended power for any speaker.
I would be tempted towards the maximum recommended power.
Since the speakers are rated as 4ohms the chosen amplifier must be capable of driving a 2r0 dummy load to maximum power and preferably able to drive a 1r3 dummy load for a couple of seconds without triggering any limits or overheating or shutting down.
That would point me towards a nominal 150W into 4ohms, at least 270W into 2ohms and preferably >450W into 1ohm.
I would be tempted towards the maximum recommended power.
Since the speakers are rated as 4ohms the chosen amplifier must be capable of driving a 2r0 dummy load to maximum power and preferably able to drive a 1r3 dummy load for a couple of seconds without triggering any limits or overheating or shutting down.
That would point me towards a nominal 150W into 4ohms, at least 270W into 2ohms and preferably >450W into 1ohm.
My own experience with Magneplanars
Either follow Andrew's lead, or bi-amp as Tom suggests. When I had a pair of Magneplanars in the early 1980s, my 40w/channel amp was entirely inadequate. A Carver M400 did the trick, but the sound was not the best. However at that point in my career that was all I could afford (the amp was free with the speakers, bought used from a friend).
Either follow Andrew's lead, or bi-amp as Tom suggests. When I had a pair of Magneplanars in the early 1980s, my 40w/channel amp was entirely inadequate. A Carver M400 did the trick, but the sound was not the best. However at that point in my career that was all I could afford (the amp was free with the speakers, bought used from a friend).
Why? I'm curious which references you have to suggest that those numbers are anything other than marketing?
For a reactive load, you have a point, though I'd encourage you to show the math that led you to your specific resistance recommendations. In case of the Magnaplanar I disagree with your recommendation. The speakers are purely resistive.
Tom
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