Mackie HR824, repair or rebuild?

[Citizen]

So I have recently acquired a gaggle of three HR824's which are, despite some serious cosmetic issues working and putting out sound.

They came as a working pair and a spare with the main woofer missing.

They came from an events company(stages, sound systems, live events etc).

I initially thought that they were good, both the complete ones powered on and sound great but lack any serious bass but i put this down to the woofers not having dust caps and hence the sealed cabinets not being airtight, on further inspection one of the drivers rubber surround has perished in parts, I ordered some 8" rubber surrounds that said 196mmOD(from amazon) but were a few mm short and don't fit.

I thought it best to remove the woofer and get a good look at the cabinets, unfortunately the previous owner has painted all the boxes with a thick black gloss paint and by the looks of it put the(woofer/tweeter) surround back into the cavity before the paint was dry, anyways I got it out with some considerable force and it made a right mess of the cabinet, it is still usable but is now taken back to the MDF.

I really would like to keep and maybe refurbish these speakers as the amps/tweeters/passive radiators are all good, in fact they are in fantastic condition given they are more than twenty years old.

So what to do with the driver, glue it and hope the rest of it does not give out anytime soon, take the rubber surround off and put a new one on or replace the driver?

The driver is a funny size, Mackie say 8.75" but it is really just an 8", the OD is 227mm, screw hole is 218mm the rubber surround is 196mm.

Oh what to do, if i can't find a replacement driver or rubber surround I do still have the amps which are very tasty units and could be bolted to the back of a good hifi speaker box or even build a box in the same fashion as the Mackie box.

I will post up some pics later of when I took it apart.

All suggestions welcome, thanks.

 

[AwesomeSauce2015]

Given what you said, it seems like the woofer is toast.
I wouldn't recommend trying to repair it unless you can get the correct parts - Not just the right size, but the right material parameters.
The surround is part of the woofer's mechanical system, changing it out with something not matched to the original surround will change the woofer parameters which will screw up whatever tuning Mackie did on that speaker.

My recommendation would be to either source new replacement woofers, of the same model as what was in there originally. You may be able to find a recone kit, but I wouldn't bet on it.
If you can't find replacement parts, then I guess you could harvest the tweeters for parts, but the amps and passive radiators are probably tuned specifically to work in that speaker, and reverse engineering them to work in a different design will probably be more trouble than they are worth.

 

[jamescarter1982]

coufl we see some photos I read there was some adjustment of the amps wonder if that included crossover point etc?

 

[Citizen]

coufl we see some photos I read there was some adjustment of the amps wonder if that included crossover point etc?

Sure will get them up shortly.

 

[Citizen]

Given what you said, it seems like the woofer is toast.
I wouldn't recommend trying to repair it unless you can get the correct parts - Not just the right size, but the right material parameters.
The surround is part of the woofer's mechanical system, changing it out with something not matched to the original surround will change the woofer parameters which will screw up whatever tuning Mackie did on that speaker.

My recommendation would be to either source new replacement woofers, of the same model as what was in there originally. You may be able to find a recone kit, but I wouldn't bet on it.
If you can't find replacement parts, then I guess you could harvest the tweeters for parts, but the amps and passive radiators are probably tuned specifically to work in that speaker, and reverse engineering them to work in a different design will probably be more trouble than they are worth.

The woofer seems fine and works(moves vertically and does not rub) but it is just the foam and dust cap, I do wonder if I should just get some speaker glue and run it until it gives up but I would also be willing to give the re foaming a go rather than abandon the whole lot, I learn best through experience so maybe I do it just to practice as I have nothing to lose and an experience to gain.

 

[AwesomeSauce2015]

Looking at those pics, I am going to have to go with my original statement that unless you can get replacement surrounds (designed to be used with those drivers!) and dustcaps, then those woofers are useless.
If you want to try repairing them, then look for part kits for those specific drivers, as using random parts will probably mess up the sound.

 

[Citizen]

Some more pics.

 

[Citizen]

Looking at those pics, I am going to have to go with my original statement that unless you can get replacement surrounds (designed to be used with those drivers!) and dustcaps, then those woofers are useless.
If you want to try repairing them, then look for part kits for those specific drivers, as using random parts will probably mess up the sound.

I don't really care for mm precision, they are a twenty year old pair of monitors that I don't want to consign to the rubbish heap, I will figure a way to either repair or re-purpose the components but seem shame to not give it a go, thanks any ways.

 

[jamescarter1982]

are the amps all working I always wonder if these amps could be reused somehow with different drivers . if the drivers were happy crossing over in the same points. I have a pair of esi near 08 that I don't really like the tweeter of I thought maybe an half decent tweeter then maybe a passive filter might be needed on the tweeter after the amp to help it into Shape .

 

[robwpdx]

I believe those Mackies used a closed loop feedback system on the woofer. There are two methods: use current feedback or use a motion sensor with its own wires back to the plate amp. The idea is to use negative feedback to cancel out harmonic distortion. You can easily find the schematic online.

If you can, you want to preserve that feedback system or reinstall it if it has been removed. You might ask Mackie, and if they no longer service them, they may suggest 3rd party repair techs and driver replacement parts.

Good luck. I have my speaker apart for a woofer replacement and my old amp just died, I need to find a 5W 68 ohm resistor and a fuse to start. I'm confident I can fix both!

 

[jamescarter1982]

so it's a bit like a servo system on a sub ?

 

[robwpdx]

so it's a bit like a servo system on a sub ?

Yes. Mackie had it on some of their PA speakers as well. Mackie was started by a Boeing engineer and they haven't been swallowed by Harman-Samsung. Velodyne had it on some of their models. There are independent techs which repair the Velodyne feedback plate amps. Velodyne exited audio to focus on their LIDAR business for self-guided and crash-evading cars. Rythmik Audio sells current feedback servo subs ASR has tested.

 

[jamescarter1982]

interesting info I wonder is the sa1532 one of those that used this system that's a speaker that always interested me

 

[Citizen]

are the amps all working I always wonder if these amps could be reused somehow with different drivers . if the drivers were happy crossing over in the same points. I have a pair of esi near 08 that I don't really like the tweeter of I thought maybe an half decent tweeter then maybe a passive filter might be needed on the tweeter after the amp to help it into Shape .

Yes this is the back up plans, I have several nearfield monitors lying around here and also just picked up a load of PA equipment, two pairs of Tannoy i8 an i12, a pair of tannoy reveal 8d's, old speaker are nearing the bottom of their value cycle before they will start to accumulate once again so everything is dirt cheap at the minute, also scored a pair of these this afternoon for an absolute steal and would love to hook up either the Mackie amps or the reveal 8d amps as they have some pretty serious eq options.

These are the 7900 2046 drivers found in the system 800.

https://soundmaster.ua/media/blfa_files/CMS8TDC_Colour.pdf

I believe those Mackies used a closed loop feedback system on the woofer. There are two methods: use current feedback or use a motion sensor with its own wires back to the plate amp. The idea is to use negative feedback to cancel out harmonic distortion. You can easily find the schematic online.

If you can, you want to preserve that feedback system or reinstall it if it has been removed. You might ask Mackie, and if they no longer service them, they may suggest 3rd party repair techs and driver replacement parts.

Good luck. I have my speaker apart for a woofer replacement and my old amp just died, I need to find a 5W 68 ohm resistor and a fuse to start. I'm confident I can fix both!

Yes there are the servo type amp and was wondering how they get the info for the loop, maybe it is a sensor built into the board, way above my pay grade buy still willing to see if it works.

Mackie don't support this model anymore but might hit them up, think it is a bit of a nonstandard size woofer, although I am tempted to get a couple of used behringer truth b2031a's as they are cheap as chips and plenty full and they are a direct rip off of the HR824 and even have the same size 8.75" driver that might just slide in, worth a pop for sure, no doubt it will be an inferior driver but if it works then it might be ok just to get them running.

 

[jamescarter1982]

what Is that an 8inch ceiling speaker
. what's your impressions of the i12 always interested in that one I believe it was .ade by fane for tannoy ?

 

[Citizen]

what Is that an 8inch ceiling speaker

Yes, edited with details above.

. what's your impressions of the i12 always interested in that one I believe it was .ade by fane for tannoy ?

I have not yet had a chance to hook it up but it looks impressive, not too impressed by it specs(70hz cuf off, this is the cross over so it has a bit more range than that) but is is a mid pa speaker, could only get one of them but on the look out for another as i think they will be really sweet, especially if I can get something like a hypex plate amp, they look awesome though.

 

[robwpdx]

Yes this is the back up plans, I have several nearfield monitors lying around here and also just picked up a load of PA equipment, two pairs of Tannoy i8 an i12, a pair of tannoy reveal 8d's, old speaker are nearing the bottom of their value cycle before they will start to accumulate once again so everything is dirt cheap at the minute, also scored a pair of these this afternoon for an absolute steal and would love to hook up either the Mackie amps or the reveal 8d amps as they have some pretty serious eq options.

These are the 7900 2046 drivers found in the system 800.

https://soundmaster.ua/media/blfa_files/CMS8TDC_Colour.pdf

View attachment 285345View attachment 285346


Yes there are the servo type amp and was wondering how they get the info for the loop, maybe it is a sensor built into the board, way above my pay grade buy still willing to see if it works.

Mackie don't support this model anymore but might hit them up, think it is a bit of a nonstandard size woofer, although I am tempted to get a couple of used behringer truth b2031a's as they are cheap as chips and plenty full and they are a direct rip off of the HR824 and even have the same size 8.75" driver that might just slide in, worth a pop for sure, no doubt it will be an inferior driver but if it works then it might be ok just to get them running.

The board / plate amp is the receptor of the motion sensor. I believe Mackie attached an accelerometer sensor to the cone or the piston. There would be wires from the sensor on the woofer back to the plate amp. There would be separate driver wires from the amp. So 4 wires from the plate to the speaker. It is possible earlier owners may have done things to eliminate the sensor. Look around for photos from other 824 owners showing the sensor and wiring.

Rythmik uses a 2 wire system where the plate amp extracts the current and uses that as feedback. I don't think, but it is possible Mackie, used 2 wire. I have followed their designs for several years. Ask their technical support.

 

[jamescarter1982]

yeah they do look impressive I've always fancied one of those . I've got a pair of 12inch tannoy lynx but somebody had taken one driver out and replaced it with some random crap. was on the look out for a second driver until my dad damaged the one good one moving stuff around in his garage I was so pissed it sounded nice as well . where are you picking this stuff up from are you in the UK? a city I'm guessing London or Birmingham?

 

[Citizen]

The board / plate amp is the receptor of the motion sensor. I believe Mackie attached an accelerometer sensor to the cone or the piston. There would be wires from the sensor on the woofer back to the plate amp. It is possible earlier owners may have done things to eliminate the sensor. Look around for photos from other 824 owners showing the sensor and wiring.

There is no tell tale wires coming from the speaker to the amp so must be on the board and run from a control voltage would be my guess or might be just a phase reversal of the outgoing signal, as I said I do not know to much of this.

where are you livking this stuff up from are you in the UK? a city I'm guessing London or Birmingham?

Bristol is home so just local stuff really, facebook marketplace is a real gem for folks not knowing what they have or just want £50 for those old speakers in the garage...

 

[jamescarter1982]

ah OK do you repair stuff and keep it for yourself or something like that ? I really like all kinds of audio I've collected some nice stuff and sold some I wish I hadn't. I'd really like to design my own speakers I've got so many ideas it's just difficult learning the programmes etc . trying to get jriver working on my laptop atm almost had a breakthrough tonight lol now it's crashed have you made any speakers of your own or have any pionters you could give me ?