Blown Mackie Thump 15-A - Worth Fixing

[mountainmike]

Hi all,

I jave a pair of Mackie Thump Th-15a speakers - about 10 years old - that appear to be blown - all lows distort through them above 12 o'clock volume; highs and mids still sound great. No noticeable tears or damage to the 15" drivers.
Assuming the 15's are blown are they worth replacing?
If they are worth replacing what do you recommend I use to replace them?

Thanks all!
Mike

 

[sergeauckland]

If both drivers distort, unless they have both been overdriven, it's possible that the suspension has sagged. If you gently push the cones, can you feel any roughness, rubbing of the voicecoil? If so, it may be possible to turn the driver over by 180deg so that any sag in the suspension corrects itself. With both having failed, it's unlikely that it's just suspension sag, but of course possible, and it's an easy no-cost repair if it works.

S

 

[JayGilb]

Hi all,

I jave a pair of Mackie Thump Th-15a speakers - about 10 years old - that appear to be blown - all lows distort through them above 12 o'clock volume; highs and mids still sound great. No noticeable tears or damage to the 15" drivers.
Assuming the 15's are blown are they worth replacing?
If they are worth replacing what do you recommend I use to replace them?

Thanks all!
Mike

If the woofer amps are functional, they may be worth replacing. Something like a Eminence Alpha-15A ($140-150 USD) would probably be a suitable replacement woofer. Slightly higher RMS ratings than the original woofer.
They're a decent PA speaker and a few DJs I know use them as well as some small local bands.

 

[DVDdoug]

The speaker and cabinet are tuned together (especially ported speakers) so ideally you should replace them with exact replacements.

Otherwise you can measure/estimate the cabinet volume and port dimensions, and plug those along with the Thiele/Small parameters of potential replacement speakers into WinISD (or similar software) to predict the performance.

 

[robwpdx]

Both have the same symptom? Is your source good? I do not remember if those were biamped or triamped, so the crossover, LF amp, or power supplies could be weak. Or as others have suggested mechanical aging of the 15" driver.

People sell replacement amp modules, but they are almost as expensive as a used speaker. Sometimes you can find videos of people fixing amps, what usually goes wrong, and what to check. The schematics are online.

People go in and out of PA speakers so sell them used. As long as you can test them, use your judgement.

Mackie still makes the SRM450, and the old Italy-made ones run a long time, I just saw someone playing them. After Italy, the switched to China manufacturing. Some people like the JBL EON, I had some EON 2 15", but I don't know the current lineup. The longer the original warranty, the more likely a used one will run longer.

You could always sell them for parts.

 

[mountainmike]

All - thanks for all your responses - I am learning a ton here about pro-audio which is really helping me improve the sound of our performances!

Here is a little more background and what I found with more testing:

• I picked up these speakers used last week. They tested great with a Shure 58 through my small Mackie 12-FX board. It wasn't until a few days ago I was able to test my 4-string basses through the board to simulate a low-frequency test. That's when I discovered the problem of distortion at low frequencies on both speakers.
• I tested with 3 Fender basses, all passive: A MIM Fender Jazz 1999; a MIM Fender Precision 2003; a MIJ Fender Jazz 1993.
• Basses tested 2 ways:
  • Through my ProCo DB-1 DI box - ground lift engaged, into channel 1 or 2 of the Mackie 12-FX board.
  • Through a Fender Rumble 100 amp (2022) - DI out to channel 1 or 2 of the Mackie 12-FX board.
• The distortion occurs on any note on the E string and some on the A string of the basses - low-frequencies.
• I've used a variety of XLR cables to eliminate that as a cause.

Further testing with my Mackie 12-FX board:

• If I enable the 75Hz low cut button on the utilized channel - cutting frequencies below 75Hz -little distortion if any.
• I ran this low-frequency sound test through the speaker - stereo headphone out on my Behringer controller hooked to my computer into a XLR into the speaker XLR input:

Using the low frequency tester I get heavy distortion starting at 60Hz.

Is this normal behavior? Should I assume that these speakers are simply unable to handle lows under 75Hz ?

 

[Slayer]

I have you physically inspected the woofer yet? If the woofers are toast, when you push in the woofer, listen for some scratchy noise.
If the woofers look after inspection and the woofer cone push method doesn't produce any scratching, then your problem most likely is in your audio chain.

 

[mountainmike]

I have you physically inspected the woofer yet? If the woofers are toast, when you push in the woofer, listen for some scratchy noise.
If the woofers look after inspection and the woofer cone push method doesn't produce any scratching, then your problem most likely is in your audio chain.

Hello,

Yes - I inspectors the woofers - they look great - no crunchy sounds or resistance when I flex them. No rips, repairs or anything. They are in near-perfect condition.

I'm thinking that when working with these speakers I'll just need to enable the hit filter on the board ( 75Hz cut button ) and watch my gains as these just don't seem to like a lot of heavy lows. Otherwise they are super powerful.

The low-frequency test eliminated anything that was in my old audio chain - I just took the headphones out of my Behringer U-Phoria interface right into the XLR input of the speaker and I get no problems until the frequency drops below 70Hz - then I get distortion.

Does this sound reasonable? Should 15" PA speakers reasonably work down to 70Hz frequency and then you limit them there are add subs ?

 

[fpitas]

https://mackie.com/img/file_resources/Thump12A_Thump15A_OM.pdf

Response graphs with SPL are near the end of the manual.

 

[mountainmike]

https://mackie.com/img/file_resources/Thump12A_Thump15A_OM.pdf

Response graphs with SPL are near the end of the manual.

Actually my Thump is much older - 400 watts. I'll check the manual I have.

 

[mountainmike]

All - I spoke with the pro audio head engineer at a local music store chain - he says that given the track record of this model and these speakers, and the distortion at steady lows inputted and at the frequency (under 70Hz) it sounds like these speakers are just wearing out and suffering from age and should be replaced.

I'll reach out to US Speaker and see what they recommend.

 

[DVDdoug]

I picked up these speakers used last week. They tested great with a Shure 58 through my small Mackie 12-FX board. It wasn't until a few days ago I was able to test my 4-string basses through the board to simulate a low-frequency test. That's when I discovered the problem of distortion at low frequencies on both speakers.

You MIGHT be "asking too much" from these speakers... Do they sound OK with regular recorded music?

Most pro/PA subwoofers are tuned down to around 40Hz (about the lowest note on a standard bass) but these speakers are probably tuned a bit higher.

You tend to lose efficiency the farther-down you extend the frequency response. Even 40Hz is a compromise but it's generally a good compromise if you want to fill a large venue with deep-strong bass that you can feel in your body. Home theater & studio subwoofers often go lower but you don't need as much output for a home environment.

I don't know much about bass guitar amplifiers/cabinets but if they are like guitar amplifiers they are designed to "sound good" when over-driven/saturated so you can probably get more sound out of a 15-inch woofer with that kind of set-up.

 

[mountainmike]

All - @DVDdoug was right. I brought these into an authorized repair center and they deduced the same - these are fine speakers but without a Sub you can't get down much under 60Hz.

Thanks all for your help from this total newbie!

 

[tmtomh]

All - @DVDdoug was right. I brought these into an authorized repair center and they deduced the same - these are fine speakers but without a Sub you can't get down much under 60Hz.

Thanks all for your help from this total newbie!

It's an interesting speaker - and based on the manual @fpitas shared, "Thump" is definitely the right name for these - that's a crazy bass hump they have. But at the same time, I noticed that the SPL capability of the woofer, high as it is around 90-100Hz, drops like a rock, very quickly, under about 60-70Hz.

And as you say, yours are a much older model. So yours might be slightly less capable than the current spec in that lower bass region.

 

[coonmanx]

I know this is an older thread but Parts Express has quite a few 15" pro woofers for sale.