Magnetic Magnat MSG 60 tweeters - diyAudio
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Old 6th December 2013, 08:37 AM   #1
Rubba is offline Rubba  United States
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Default Magnetic Magnat MSG 60 tweeters

Magnat MSP 60 speaker investigations:

After a brief internet search while shopping at Goodwill, I purchased a pair of Magnat MSP 60 speakers. Post-purchase research revealed a weakness in the tweeter; they apparently don’t survive abuse. Also, the word “ribbon” in this manufacturer’s description is used to identify flat wound voice coil construction. I also found that drivers are shared with proven Dahlquist designs. Here’s a look:

Click the image to open in full size.

Once home, I checked for shorts then connected them to a test amp. Sound was disappointingly muffled with no output from the tweeters; a value of infinite ohms measured across them. I researched replacement factory tweets in an effort to decide if I should return them. Replacements proved to be cost prohibitive for my intentions and have limited (if at all) availability; let’s see if I’ve got a suitable substitute in my bag o’ tricks. If not, they go back to GW.

Recent acquisitions included two pairs of NOS surplus tweeters from Apex Jr. Speaker Stuff (Scroll to: Shielded Soft Dome Tweeter $14.95 a pair). One pair was intended to replace a failed pair of SARAS two-ways’ tweeters and another pair was spare.

After disassembly and analysis of the Magnat and the surplus tweeters’, an immediate, direct replacement method using inventory components was not evident. The Magnat tweeters are integrated into a 4x4”ish square frame about 3/8” thick, countersunk into the cabinet’s velvet-like motor board. The original tweeter frames would not easily accept my surplus tweets as replacements. Let’s see if they’re sonically compatible.

The Magnats’ nameplates indicate a “1.0 Watt” sensitivity value; apparently some detail was lost in translation, transcription or whatever. I checked the Magnat Wiki, Magnat Museum, and other internet sites; none identified an MSP-60 speaker’s efficiency value. One specific tweeter-search found a single posted request for information with lots of resource links and another post that was answered like: “PM me” and a replied “PMed” in a user’s group but no other information.

Let's dig in...

After my Magnat tweets were removed and laid on top of the cabinets I connected clip leads to jump the surplus tweets and test compatibility. Results were sizzling (intensely bright), average efficiency within the operational range of these surplus guys’ appears to be in the high 90s untitled and, I suspect, the Magnats reproduce SPLs the low 90s. Compatible?

I added 30 ohms series resistance to the tweeter crossover connections but it muffled the sound. I changed series resistance to 16 ohms and results were satisfactory, although a little bright compared to my reference speakers, Klipsch Cornwalls’, tonal balance. I ordered a pair of 20 ohm 25 watt resistors as permanent best-guess value replacements. For now, sound is good (excellent even!), so on to the physical compatibility issue; how to fit a round, flat peg into a square, recessed hole.

With a fried tweeter assembly in hand I visited the local hardware store. My intent was to find a simple, elegant solution for replacement tweeters into Magnat cabinet recesses. After several ideas and products were examined I found the lid of a 4x4x2 plastic electrical box, albeit overall smaller, dimensionally matched the tweeters’ receptacles screw spacing. Junction Box, 4" x 4" x 2" - antonline.com

Click the image to open in full size.

I identified other work-arounds that need resolution but this would prove feasible. I cut the new electrical box faceplates to accept our replacement tweeters. Other structural elements were also modified on the box lids to fit and seal our speaker application.

Click the image to open in full size.

Test fit drivers into the new frames and layout resistors for soldering after the finish is complete.

Click the image to open in full size.

A little paint and final details were sufficient to surpass the residing speakers’ aesthetics-preference so this stand-mounted black pair won an opportunity for placement testing.

The Magnats were moved into a 2.0 A/V living room environment, replacing a pair of modified AR 92s speakers without comparison…and sounded fine. I sensed no dramatic improvements but a similar, accurate, soulful presentation compared to my mental reference. I was never distracted by poor quality or any type of sound signature after several days of TV, BDs, CDs and radio. Preferred aesthetics closed the deal, a pair of AR92s speakers is on the market.

Click the image to open in full size.

I compared a single Magnat to an AR via amp balance control but the speakers’ efficiency delta proved this method scientifically incredible. The Magnat was much more efficient. Non-scientific compensation for level differences resulted in a definite “nice” (refined, accurate and LOUD) SQ for the Magnats compared to the ARs.
I love the Magnats without reservation.

Round 2: AR cap refresh? Comparison?
Click the image to open in full size.
I think they’ll never be as loud.

Thanks for all of your DIY posts that provided me insight to quality sound reproduction at reasonable prices.
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Old 7th December 2013, 12:17 AM   #2
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You could have bought my DQM-5 Magnat tweeter pair but I neglected to put them up for sale, didn't I. Sounds like decent quality soft domes sound alike, no? Level matching aside, what's the difference? Ferrofluid, rear chamber, what else?
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Old 16th December 2013, 02:08 PM   #3
Rubba is offline Rubba  United States
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Quote:
Originally Posted by phivates View Post
You could have bought my DQM-5 Magnat tweeter pair but I neglected to put them up for sale, didn't I. Sounds like decent quality soft domes sound alike, no? Level matching aside, what's the difference? Ferrofluid, rear chamber, what else?
I'm curious about the SQ difference between the stock tweeters and my implementation. Magnat's published frequency range indicates to 40kHz; some audiophools attribute extended frequency range to improved "air." Uncertain if the tweets I used go much past 20kHz but their rising response from 2k to 18k and high efficiency impressed me enough to try them.

A post linked from the tweeter sellers website includes a hobbyist's concerns about the ferrofluid in these tweeters, and in general. Since I disassembled one of the Magnat tweeters and one of the proposed replacements to investigate methods of implementation I also removed all fluid from the replacement. The task was simple so I cleaned both.

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Old 16th December 2013, 06:09 PM   #4
Rubba is offline Rubba  United States
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Default System Synergy

No option for playing vinyl with the existing Adcom tuner-line level pre and the tube preamps in my arsenal are undesirable (may be left on for days at a time) in this application. I found an HK 3270 for cheap and tried it in the current system consisting of a Sony Blu-Ray, SCHP-1001 as CD, AR92s speakers and Arjen’s 2020 T-Amp board with a modified SMPS. A Panasonic 50” plasma and AT&T U-verse box take care of TV audio source and video presentation. Cables are inexpensive AQs and home brew (18-strand Teflon CAT-6 braid speaker wire, white lightning, two-strand straight magnet wire and two-strand CAT-6 XLO-style interconnects).

I was immediately impressed with the HK receiver’s sound so decided to replace the existing pre and amp with it. Two support feet were broken and the inside was dirty so I cleaned the pots, blew out the dust and installed a couple of non-matching feet on the back, out of view.

Before I got to the TT project I found these Magnats. The recipient preferred the Magnats’ appearance compared to the ARs and sound was at least similar so they stayed while the TT project got started.

For $30 I tried an OmniMount Tria 1 B – 1 as a wall-mount turntable shelf. Amazon.com: OmniMount Tria 1 B - 1 Shelf Wall Furniture (Black/Dark Glass): Electronics Dimensions appeared adequate and looks are a match for the environment. Note that alignment modifications were required, the shelf sags. Could've also adjusted the TT feet but I didn't care for the shelf's leaning appearance.

I pulled my old HK T55C from storage, checked what I’d need to put it in service and assembled/ordered parts. After the belt arrived (I got the USA-made 25”) I found the AQ 707’s cantilever gave up; the spring is sprung; it barely tracked and I couldn’t find any information on this cartridge with a non-replaceable stylus. I did find similar-looking 404 and 606 cartridge examples and think I should have this one re-tipped. In the meantime I picked up a Grado red at Sounds Unique: Sounds Unique - Main an excellent Bay-Area audio resource! Got back and after Geo-disc cartridge alignment, setting the VTA (not for noobs) and tracking weight adjustment; the TT sounds good. The shelf is small. Published dimensions are a little misleading and maybe I shooda measured twice too. The table fits the shelf with a little overhang so it will work for now. The shelf is also more flexi than I like; maybe it won’t stay. Recommendations are welcome.

Sound from the system has improved immensely. Flexibility has also improved with the addition of a vinyl source and owner (musician) is impressed with results.

Click the image to open in full size.

I must reiterate, the HK 3270 and Magnat speakers are sleepers. I’d never expect a modern-ish, entry two-channel receiver to perform at this level and the speakers surpass my expectations. I paid less than $100 for these components and I’d be able to live with them…eh, if I had to.

Sony Playstation One Consoles are wonderfully neutral sources and can still be found on the cheap; SCHP 1001 and SCHP 5501 (USA) only, please. Disconnect the output, throw in a film cap and resistor and you’ll be in awe. Playstation as CD-player

This turntable is mostly-functional and, in this environment, may not benefit from extensive, recommended modifications [url=http://www.audiokarma.org/forums/showthread.php?t=272086[/url] but after I tweaked the VTA the auto stop function cuts off short (an unforeseen VTA-associated mechanism misalignment). Since I have to go back for an adjustment I may export the PS ala Frank Van Alstine; Just Modded my HK T55C table to Van Alstine's Outboard PS Mod and... it doesn’t look too difficult.

OK, that’s a lot to digest. If I upgrade any of the sources I’ll post in appropriate, existing threads. I don’t consider this system modification evolutionary but revolutionary. Previously lifeless and dull, is now incredibly exciting; the right music will invite toe-tapping to break-dancing responses. I welcome comments, questions and recommendations. Thanks for lookin!

Last edited by Rubba; 16th December 2013 at 06:33 PM. Reason: HTML code misuse
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Old 16th December 2013, 06:49 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

If your guessing a two resistor L-pad that maintains tweeter impedance is far
better than 20R series, as that is guaranteed to be wrong for the treble x/o.

4 ohm tweeters can easily be L-padded to 8 ohm when dealing
with lots of attenuation, though if the mids are 4 ohm, L-pad
the tweeter to 4 ohm if you can't find the tweeters ohm value.

20R in series with the treble x/o or the driver will completely
misalign it, you should L-pad the driver for 4 ohm or 8 ohm.
(Typically treating the tweeter as 3R or 6R)
As it is it is certain to be very wrong.

rgds, sreten.
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Last edited by sreten; 16th December 2013 at 06:59 PM.
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Old 19th December 2013, 07:27 PM   #6
Rubba is offline Rubba  United States
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Quote:
Originally Posted by sreten View Post
Hi,

If your guessing a two resistor L-pad that maintains tweeter impedance is far
better than 20R series, as that is guaranteed to be wrong for the treble x/o.

rgds, sreten.
Thanks sreten! I researched and found some information about L-pads. I think I have enough parts to try one tomorrow. It will be interesting to hear and identify the effects of tweeter misalignment.

The new tweeters are labeled 4 ohm nominal, manufacturer identifies MSP-60 system impedence as 4 and 4-8 ohms. I'll measure the drivers and use those numbers to calculate L-pad values.
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Old 19th March 2014, 10:06 PM   #7
Rubba is offline Rubba  United States
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Hey sreten!

Using the tweeter specs and a couple of online calculators, I found several resistor combinations that were close to off-the-shelf high power resistor choices to achieve my target attenuation. Unfortunately, available resistors were as much as a few hundredths (maybe tenths) off of prescribed values.

After modification, sound is similar but low metallic sounds (not so much the high resonant sheen) from cymbals have more definition. Striking sounds seem to have more body. High frequencies seem less congested or more open (hope this isn't audiophoolia).

Should I match exact values or am I at a point of diminishing returns? Intended modifications were planned to occur within the crossover circuit board which is apparently glued to the speaker cab. The external L pad solution is win-win in this regard but matching exact values may require additional and potentially complex combinations of resistance. OTOH, I could strip and modify all crossover network HF components to streamline the circuit.

Added a Velodyne VA1012X Subwoofer to the mix. Great for movie effects but the Magnats were doing great with most modern prerecorded music on their own. Sound is reminiscent of visits to '80s shops that carried A/D/S speakers demonstrated with quality amplification.

Anyone is welcome to recommend a concise thread or tutorial that explains crossover network alignment ins and outs.

Thanks!
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