Realistic Mach 2 dilemma

Discussion in 'Hi-Fi Stereo Speakers' started by bigphil1, Jul 20, 2018.

  1. bigphil1

    bigphil1
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    Hi all. Just bought a pair of Realistic Mach 2 speakers and yes the woofers foam has deteriorated completely, this is also the case with the 5" mids. Can anyone recommend a good replacement please? Thanks Phil.
     
  2. lindsayt

    lindsayt
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    Speaker Repair Kit for Realistic Mach 2 15" with 5" Mid range Surrounds Mach II | eBay

    How much did you pay for the Mach 2's?

    When I've done refoams on 15" and 8" drivers I found the big trick was to make sure the voice-coil was central in the magnetic gap. I did it by glueing the surround to the cone, leaving it to dry then using my fingers to push the cone in and out and feeling for where it was rubbing. When I glued the foam to the cage it was always off centre on the cage in order to get the voice coil centred in the gap.

    If you do get voice coil rub, simply take the surround off the cage and do it again.

    Once you've got them repaired, you'll have a huge grin on your face for the sound quality per £ spent.
     
  3. bigphil1

    bigphil1
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    Thanks I paid £100 for the pair. I'm looking at changing the drivers completely, I think the spider dampers have failed aswell as they are very loose. I'm looking at some budget ones on EBay, you can get a pair for under £80. I'm not sure if they will be any good, they have sufficient specifications. Cheers Phil 2x QTX Sound QR15 PA Passive Drivers 500W Essex 5055839138436 | eBay.
     
  4. Ugg10

    Ugg10
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    You can’t just drop in any old speaker of the same size. Inside are some electrical components (crossover) that shape the signal to the bass/mid/high drivers ensuring the final sound is integrated together and are specific to the particular drivers used. You may be lucky, but unless you know the parameters (look up Small-Theil) of the original drivers then it is pot luck how it will sound.
     
  5. bigphil1

    bigphil1
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    Thanks, I'm quite new to this. What is Small-Theil? How would I find this out. All that is written on the original drivers is Woofer 3807 8ohms made in Korea and on the midrange is 1265 again made in Korea. Cheers Phil
     
  6. Ugg10

    Ugg10
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    Small Theil parameters define how will a driver works in different enclosures and how the driver can be integrated with others (simplistic explanation) and are used fir designing the crossover between speakers. The parameters include things like electrical and mechanical “stiffness”, resonant frequency, piston area, max excursion etc.

    So, your 15” driver is physically able to produce sound from pribably about 30hz up to about 5khz but past about 1khz the sound will be distorted so the crossover will filter out sounds above about 500hz with a steady roll off. Similar fir the mid, it may work down to 100hz but not very well so the crossover will slowly feed in the sound to about 500hz. The same between the mid and the tweeter at around 3khz. The electrical components (inductors, capacitors and resistors) are chosen and the circuit designed specifically for the performance of the drivers in the speaker (they also take into account the enclosure).

    This guy replaced them with Eminence Beta 15”. Realistic MACH TWO | Audiokarma Home Audio Stereo Discussion Forums

    There is also these designed as a replacement.
    "GRS RSRMO-8 Replacement Woofer for 15" Realistic Mach One 8 Ohm" from www.parts-express.com!
     
  7. bigphil1

    bigphil1
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    Thanks for that. I might go for the Eminence Betas they're on EBay and pretty reasonable. The GRS you mentioned, I did see these but they wanted $140 just for postage but they did look the part. I don't trust myself with refoaming them, my hands are like shovels. Do you know anyone or can you recommend somebody that can refoam speakers please. Thanks again Phil.
     
  8. lindsayt

    lindsayt
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    I'd expect the spider dampers to feel very loose if the surrounds have gone. Difficult to say without inspect them myself personally. But chances are, if you replace the surrounds they will sound as good as new. Laughably good for an all-in price of £150.

    Of course, you are quite welcome to re-engineer them as a DIY project.

    In which case if they were my speakers I'd be looking out for something like a pair of Altec 515's. Something that - with the right midrange unit and tweeters - would elevate this to above typical modern big-name £20,000 speakers.

    JBL have also done a lot of good 15" drivers that can be picked up used for reasonable money.
     

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