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NPAD - New PA day!

Discussion in 'Amps [BG]' started by christw, Sep 17, 2013.


  1. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
    Hey all, today's my new PA day. I needed something to cover the PA duty when Mike upgrades the crossovers in my Big E 2x6's and had just pulled the Faital out of my Kustom cab for use in a Thunderchild 118 he's also making me. :)hyper:!!!)

    Anyways, I bought some MCM Custom Audio brand 12" mains, cheap stands, and an MCM Audio Select 55-2983 15" to retrofit into the Kustom for PA sub duty. Altogether cost me $200 including $12 tax, $10 shipping, and a $10 oscilloscope probe. I've got to say, after some fine tuning, I'm happy with the results. The mains left a bit to be desired with what sounds like a mid scoop with an annoying amount of high end sizzle when used for playing recorded music but hey, they cost $36 each. With the sub in there, you really can't tell.

    The MCM 55-2983 driver is really solid (and HEAVY!). It performs really well in that cab. It has less low midrange but more low end than the Faital had in that particular cab. I can't wait to break it in. I think it'd be great for bass guitar use with a midrange or some EQ work. I opted to turn off the midrange in my Kustom to use it as a sub. I'm better off letting the mains do the > 250 Hz lifting anyways.

    [​IMG]

    [​IMG]

    Reassembly of the Kustom with the adapter ring.

    [​IMG]

    [​IMG]

    The finished house/practice PA. There's an Ampeg SVT-BSP in the rack that runs to the board. I've got a little over 200w to each main and 250w to the sub. This whole thing performed admirably for how cheap it is. It sounds good and keeps thumping when you crank it LOUD. That's more than I can say for the PA in some local venues. I'm definitely happy with my bottom dollar purchase. :D

    [​IMG]

    The drum kit can wait for another day...

    [​IMG]

    The mess will also wait.

    [​IMG]
     
  2. modulusman

    modulusman

    Joined:
    Jan 18, 2004
    Location:
    montana
    Well as long as you don't inflict it on the paying public and leave it in your basement you should be good to go.
     
  3. JimmyM

    JimmyM Supporting Member

    Joined:
    Apr 11, 2005
    Location:
    Apopka, FL
    Disclosures:
    Endorsing: Ampeg Amps
    The wet blanket of modulusman strikes again. Must be awesome to be perfect.
     
  4. modulusman

    modulusman

    Joined:
    Jan 18, 2004
    Location:
    montana
    I'm not perfect Jimmy even if you think I am.:D I just don't understand why anyone would waste their money on crap speakers that are targeted for the DJ market. From what I could find online some of thei PA cabs cost less than a decent mic cord.
     
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  6. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
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    Use of this field for any other purpose is prohibited
    Um.....OP...how do those perform relating to your personal experience?

    I'm not filling your thread full of bullpiles. I'm genuinly curious. I've spec'd out a handfull of 15's for my PA cabs and the MCM is a strong contender. I'm mostly interested in the speaker's performance vs. what you were expecting given the specs and if you have more than one, do they seem consistent?


    My deal is this........I put my best woofers in my tops to run "good enough" without subs. If I had affordable 15's to replace there that could run acceptably well, I could make functiional subs out of my "good woofers"..

    I care not what any nametag brings. I'm only interested in the product, and how close that product may be to another of the same thing.

    Thanks,

    -Will
     
  7. lossfizzle

    lossfizzle

    Joined:
    Jul 8, 2013
    OK, I recently got a set of those MCM 12"s for a bandmate and spent a good number of hours tinkering with them, including taking them completely apart. I was surprised at how passable the woofer / competent the low end is for the price, but in my opinion anyone planning to play these out has GOT to get something to replace those piezo horn drivers right away. They are definitely the Achilles heel of those cabs. In stock form, the upper midrange is ragged / nasty and the high end of the spectrum simply doesn't exist, and it's impossible to EQ them to sound good.

    Naturally you'll also need something like a basic rolloff cap (or something more sophisticated) to cross over whatever proper driver you attach to the horns. There is nothing like a highpass filter in the box as the piezos don't need any. You'll still be doing pretty well on the total price with two new compression drivers and the basic highpass components.

    Also, these things are not the most efficient PA cabs the world has ever seen. I can't say at this point how much of that has to do with the aforementioned terrible piezos. As little as it costs (and as fast as it is) to retrofit them with better horns, I still think they're a heck of a deal. You're basically paying for the empty boxes at what they charge.
     
  8. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
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    Endorsing: J Worrell Bass
    Because these cost $36 each, were local enough for 1 day ground shipping, and provided me an upgradeable platform for budget PA mains with some tinkering.

    The mains? They're in severe need of an upgrade to be respectable. DJ's and teenage "metal" bands would be into these in their stock form but most of use ask a little more from our PA. The blatant gap in the midrange between the woofer/tweeter kills me. So does the sizzle up around 8-10k.

    I stuck the 15" in my W bin Kustom. That application isn't the best to really judge a speaker. For the cab it was in it performed admirably-a bit like a stiffer, slightly less sensitive Kappa Pro 15A. (It isn't close to broken in yet though.) So far I think it has a great performance to price ratio but to say anything more would just be conjecture.

    Sounds like a good idea. I think these woofers would be a great candidate for doing that on the cheap. The MCM mains themselves are better left as boxes to fill or a practice PA than a gigging PA. I just can't specifically speak for the 15's performance in a traditional PA cab. I do believe that to see a significant improvement in performance over that speaker, I'd be in at least twice as deep.

    PS - Coupon code AFC909 gets 15% off. :hyper:


    I noticed the same issues. What model woofer do they run? What did you replace them with? I was originally thinking I'd need to do a crossover/HF upgrade to fix that midrange dip and sizzle. The fact that it's a piezo explains a lot though.

    I agree with you there. They're just as good as the junk I could buy anywhere and at a lower price point. With a proper HF and crossover I think the mains would be a passable PA for small shows if not a little light on the bass.
     
  9. modulusman

    modulusman

    Joined:
    Jan 18, 2004
    Location:
    montana
     
  10. DerTeufel

    DerTeufel

    Joined:
    Nov 11, 2011
    Location:
    Wildomar, CA
    I say tinker away. I'd be interested in reading about your results.
     
  11. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
    I'm well aware of their quality. My goal was to put something together that'll function and take abuse for the foreseeable future without me worrying about it and I have that. I don't care who fiddles with my PA now! :D

    I did some disassembly on the cab to see what I have...

    The woofer is unknown and unmarked. It doesn't match anything in the MCM catalog. There was one broken mounting stud and one cracked mounting stuf on the horn. Horn dimensions are 11 3/8" x 4 3/8" outer and 9 1/4" x 3 1/4" cutout with 1 3/8" 4 screw mounting pattern. Finding a replacement horn might be a pain. Thankfully I can glue the studs back together.

    [​IMG]

    [​IMG]

    Small crossover in here. 3.3 µF cap is visible. For an 8 ohm 1st order split this puts the crossover between 4250 and 4300. No wonder there's an upper mid gap. I'm thinking I'd need an L pad to properly match woofer/tweeter sensitivities, a lower crossover, and new HF/midrange driver to make this a giggable small PA.

    [​IMG]
     
  12. Rockin Mike

    Rockin Mike Supporting Member

    Joined:
    May 27, 2011
    It's nice to have a separate PA in the house for rehearsal.
    Tearing everything down for a gig and setting it all up again afterward is a hassle.
    Sometimes it doesn't get done, and rehearsals get postponed.

    So I say, good on you.
     
  13. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
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    I'm going to address how I'd upgrade these speakers. I'll bypass all of the Pyle junk offered on the market when looking at upgrading components. I've found their specs and ratings to be dishonest and their products to be underwhelming.

    Tweets

    This Goldwood horn should fit in the standard cutout: http://www.parts-express.com/pe/showdetl.cfm?partnumber=270-095

    Here's my top pick for a replacement tweeter: http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-525

    The tweet would need a 3rd order crossover at 2.5k which is quite easy to build with the aid of online calculators. I would need to pad it.

    Woofers

    This is my top pick if I were to replace the woofer would probably be this Dayton PA model: http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-032

    I'd like to opt for the cheaper MCM model but it doesn't like these boxes. http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-2982-/55-2982


    Costs

    Boxes - $36 x 2 = $72
    Tweets - $30 x 2 = $60
    Horns - $ 7 x 2 = $14
    PE Dayton Woofers - 65.5 x 2 = $131
    Crossover bits - ~$30 x 2 = $60
    Total - 168.5 x 2 = $337

    Modeling!

    The MCM boxes are tuned to 52 Hz. Volume is 3085 in^2 with 2 ports of 2.875" diameter and 4.875 length. With the Dayton drivers I get a flat signal with -3dB at 55 Hz and -10 dB at 40 Hz.

    The MCM drivers have bump between 60 Hz and 200 Hz. It peaks at 2.8 dB at 80 Hz. The -3dB is at 52 Hz and -10 dB at 39 Hz. If I extend port length to 7.5 inches, I get a 45 Hz tuning frequency and reduce the hump down to a 1.6dB. Frankly, I think this driver is best left to a BIG cab or BG use.
     
  14. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
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    Perhaps if I stenciled some cork-sniffer name on there it would sound better?

    I just want something that works for a second set of practice/loaner PA cabs, the cheaper the better. I could just stick Betas in there but you can almost get 2 MCM's for the price of one of those and Betas are already very affordabke.

    Like I said, the cheaper the better. I just wonder how close the actual drivers come to the datasheet specs.
     
  15. will33

    will33

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    My PA cabs are roughly 3.5,cu.ft. tuned 48-50hz. I already cut some around 200hz to clear up vocals/make lyrics understandable. A bump there wouldn't be doing me any favors for vocal use, but would make them good bass guitar drivers....if they have enough top.
     
  16. christw

    christw Get low!

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    Nahhh. The mains sound a bit like you're listening down a hallway. With some judicious EQ work they could probably be made a lot more presentable.

    For practice/loaner duty they'd be great. That's why I bought them. The overall quality of sound isn't super high but they're passable if you work with them.

    As far as the mains go, I'd say they're probably good for 100-150w RMS without a high pass on the lows and should be used with a proper subwoofer if you're running kick or bass through them. I think their lowest usable frequency at high volume would be around 200 Hz. Their upper limits seem to be dictated by the piezos. Overall, for $80 they'll hurt your hears and annoy the neighbors and sound okay doing it but only okay. Sensitivity specs seem close to accurate. I'll run some sine waves through them after class and check for peaks/dips.

    I'm a wee bit unclear...Are you looking at woofers for your mains, spare mains on a budget, or both? The MCM mains in their stock condition are hardly boomy. Their low end is pretty subdued. I'd say more than anything they're piercing.
     
  17. christw

    christw Get low!

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    So, because I'm insane I pushed everything to it's limits. The mains should be high passed between 150 and 250 Hz. The higher the better. Their xmax is pretty low and their power handling is definitely excursion limited. I stand by the previous 100-150w RMS limit. Anything more will fry the crossover, kill the piezo, or cause woofer over excursion. (The crossover does not protect the piezo from bass heavy signals!) The single MCM 15" in the W bin Kustom outperformed the pair of mains by far under 320 Hz. (I didn't feel a need to go any higher than that.) Given the box that it's in, the 15 performed admirably when fed a 40 Hz sine wave and limited to about 270w RMS. I own several hodge podge home audio systems that'll give me a better 40 Hz than the mains though. I think they need a dedicated sub to perform as a full range standalone system. Pole mount them on top of some of those MCM 18's, add in a cheap power amp, rent it out for a few months... Profit! ;)

    FWIW, in regular bassist terms I'd say these are worthless for low bass (40-80 Hz), sad in the lower of the low mids (80-320 Hz), lacking a little bit somewhere in the midrange (500 Hz ish), a bit aggressive in the upper mids (1-2k), scooped in the low treble (3-5k), and have ice picky in the high treble (8+k). For $36 each I think they're worth it though. As long as I'm manning my hodge podge PA I can make it sound proper. It's sort of like the one friend everyone has who have who drives a total jalopy but enjoys fussing with the quirks.
     
  18. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
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    After some practice and a lot of playback while cleaning the basement I can say that these are good for a junker/loaner/practice system. They will get by for vocals in a live situation but I wouldn't use them for much else. The woofer efficiency seems to be significantly lower than that of the tweet accounting for the weak low end, the seeming midrange deficiency, and the ice pick treble. I'm not sure they're something I'd give my stamp of approval to. They're more like something that'll make due when there's nothing better around, like the boxed wine of PA gear. (They don't even come with a cork to sniff!) That was why I purchased them though. I can't really be disappointed. They'll do. ;)

    Edit: ran some 20-20k sweeps. WOW are they inconsistent. I'd hate to see those sweeps on paper. These are worth what I paid but not a dime more! Like I said, they'll do. :D
     

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