Yamaha HS80 Mod

Hi All

I'm keen to try and get a better, more accurate sound from my Yamaha HS80's and noticed someone has managed to do this here:

http://www.zenproaudio.com/yamaha-hs80m-zenpro-mod.aspx

This particular user is from the GS forum and as the site describes, the mod involves removing the limiter and replacing electro caps with WIMA/Panasonic low esr type as well as replacing the op-amps for Burr Brown 1642's. Unfortunately the only way to have this done is to either send your existing monitors in or buy a new pair from them and for people outside of the US who already have a pair, it's not really the best option.

Now, i'm not new to DIY but give me a schematic and I frankly have very little idea of whats going on. BUT I'd like to try and perform this mod with some guidance from here if possible.

Here's a copy of the schematic for the monitors:

http://dl.dropbox.com/u/3228830/HS80M_HS50M_Schematics.pdf

I'm sure a lot of guys here probably use these monitors as they're great value and have a very decent sound for the price (and no doubt translate very well in my experience) so I'm sure others will benefit!

Thanks!

Nobody?

If you want the mod they are advertising, you could pull the circuit board out and send it without the rest of the speaker. The shipping would be much cheaper. I would contact them and ask if that would be possible.
They are doing the mod for a very reasonable price I think. Since it is a surface mount board, it wouldn't be an easy beginner project.
I have hs80s and like them. I'm curious about the mod myself, but  I wouldn't expect the mod to change the sound significantly to replace the caps and opamps. Having several speaker options would be a better investment.

I think disabling the limiter is easy. Remove R622, which is labeled as a jumper, on the amp board.  It looks like the limiter does start to limit the driving voltage for the woofer once it exceeds 15v, which is kind of low for a speaker rated at 120watts. The limiter works by the speaker voltage going across the voltage divider of R621 and R619. The switching diodes (1ss133) will shunt voltage that exceeds there switching voltage, 0.6v. So for the voltage between R621 and R619 to be 0.6v or greater, the driving voltage to the speakers has to be greater the 15v, by ohms law. Once the switching diodes start conducting, the limiter circuit 'pulls' signal from the input to the power amp transistors.

If you try these with the limiter disabled, please report back on the results.

Having modded active speakers extensively before (Adam A7) and modded converters and consoles I would be cautious about this. It's easy to convince oneself of an improvement only to find out later that it actually was the opposite. It's especially difficult to test the mod in an active speaker scientifically (since there's no output where you can simply measure THD etc.). I'm not a big fan of the OPA1642 in general and didn't like it in EQs. Panasonic electrolytic caps in the signal path without a lot of bias don't sound that great to me either. The limiter is there for a reason, otherwise the manufacturer wouldn't bother implimenting it.

Also, in the end a budget active speaker involves so many compromises that it's not really worth to mod it IMO. Better get a good passive speaker and a quality amp. That's what I've ultimately ended up with.

Just my 2 cents.

Better get a good passive speaker and a quality amp. That's what I've ultimately ended up with.

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Agreed.  What passive speakers are you using? I recently added a pair of B&Ws to my monitoring. I still use the HS80s a lot, but find much more clarity and detail with the B&Ws (reverb, high end detail, etc...)
Don't expect bookshelf size nearfield monitors to sound great - they are supposed to provide a good reference.

dmp said:

What passive speakers are you using?

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NS-10s, a passive closed 3-way DIY speaker, Hypex amp, and also one of those Behringer Mixcube clones (sounding better to me than the Avantone speakers I had before).

Thanks for the replies!

So you think the mod won't be worth it? If it's anything better than factory I'm willing to take it on. I have plenty of experience with surface mount soldering so have no problems with the op-amp replacements.

I was thinking of removing the limiter to see how the sound is affected. You've made some valid points livingsounds but for a nearfield monitor that rarely goes over 75db, do you think it is necessary?

So if I was to remove the limiter, it's just a case of removing the R622 jumper and that's it?

BTW, dmp, they've already specified that international users are not able to ship the boards only in - only ship the complete speakers (in original boxes) OR buy a new set.

Ok, so I've removed the limiter. It does seem to have 'opened' up the sound a tad, separation and transients seem more obvious for the mids. Doesn't seem to have affected the high end much though.

Actually the low end seems deeper too..

Interesting - would it be easy to put in a switch to turn it on / off?
The limiter is only affecting the lows - the woofer.

Yes, easy to install a switch if you prefer. It's definitely done something to the low end as I can sense a different vibe to my own mixes as well as some of my favorite tracks.

I may pursue the rest of the mod, cap and op-amp replacements!

Could the reason why Yamaha implemented a limiter be solely for the purpose of saving themselves from RMA's from consumers pushing the levels too high? I've read that the MSP7's don't have one on the boards and are supposed to be a step up from the HS80's.

Could the reason why Yamaha implemented a limiter be solely for the purpose of saving themselves from RMA's from consumers pushing the levels too high?

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Let us know if you blow your speakers today 
Seriously... it may be that the speakers perform better as a mixing reference if the power to the woofers is reduced as the speakers are pushed to higher levels. I don't know. I'm really interested to put in a switch and try it though.
If I were to make a quick comparison, when I flip through the 4 options I have for monitoring, the hs80s have a lot of low end, less definition in low mids, a lot of mids and mid highs, but little high detail.
For example, I can't readily tell the difference between a .wav an mp3 - but on my B&Ws, mp3s are very noticeable.

Hehe, i don't think they'll blow but if they do, reason to upgrade!

You're pretty spot on about your description of the sound from the HS80's. Mid and mid-highs are certainly up there, the high end is rather harsh and unclear I've found too. The general sound seems to be clouded too I've noticed. I'm not sure what's causing this but it's fairly obvious and it's something that the Zenpro mod claims to clear up. That's why I'm rather curious about the mods as I actually picked up this muddy phenomenon a few weeks after buying the monitors.

Hi, i'm doing the mod with the chips i have on my stash. I the first to chips in each monitor with lme49722 and a opa1642 on mid eq and room control section.
I did the limiter snip and signal path caps with Pana FM's.
So much better sounding now, the bass is more extensive and natural and highs begin to became liquid instead of rough.

Loving so mucha that i'm thinking of swapping all opamps. In order to finish the mod in both speakers i only have 8 of the opa1612 type or ne5532 type.

Are 1612's less stable than 1642's? Worse sounding?
Same question for the NE5532.

thanks.

That's great xefe, I'm still only up to the limiter snip.

Any info on which caps you used exactly? Do you have any plans to replace any more, maybe some WIMA's? Also, how come the combination of op-amps? Still trying to decide on which to use myself.

I'd really like to get rid of that 'blur' that the Zenpro mod claims to remove.

The OPA1612 have something weird going on in the high end. The NE5532 sound great, but you need to solder a 100nf quality ceramic cap between the +/- rails to prevent it from exibiting it's own peculiar oscillation. Douglas Self advices not to bypass them to ground.

For the EQ I would suggest OPA2132 or (slightly worse) OPA2134. The OPA1642 I don't care for very much to be honest.

Never used the LME49722, but the LME49720/LM4562 are the go-to bipolar op amps where maximum transparency is required IMO.

Oscillation is something to watch out for here, the original op amps have a very low slew rate and don't require much attention. Depending on the op amp used additional local PSU decoupling may have to be applied. Better op amps should provide an audible improvement, the 4558 IMO is great in things like analog drum machines to get some punch and roll off transients, but not really studio grade material where tranparency is called for.

It might help to use better caps (NGO/COG ceramics) in the feedback path if inferior ones are used, but with surface mount components this might be hard to do.

For the filtering caps polystyrene sound best IMO if you can fit them, nex best are mica, polypropylene, metalized pp in this order. There are a lot of differences between brands and product lines though. There are also mylar and electrolytic caps in the signal path that could be upgraded with higher quality ones, I like Elna Silmic II for reasonably inexpensive audio grade electrolytics, and would probably use polyprobypylene for the mylar ones where they fit.

If I were to mod this speaker I would (judging from the schematics and my experiences with similar circuits) use a 5532 for the first and the last (IC101 and IC104) op amp and OPA2132 for the rest.

You can read some of Douglas Self's "The Design of Active Crossovers" online via google, it deals with all the relevant questions in a very accessible way.

thanks!

can you explain me your options? why the 5532 instead of 1642 or 1612 and why only on woofer out? (ic104)

xefe said:

thanks!

can you explain me your options? why the 5532 instead of 1642 or 1612 and why only on woofer out? (ic104)

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From my experience the 5532 generally sounds best in the signal path (when the necessary precautions are taken) and the 2132/2134 sounds best for EQ. Ultimately i didn't like what the 1612 and 1642 did to the sound.

Many of these new op amps look great on paper and measure very well, but something isn't right about how they sound and how it influences the recording process. At first they may sound clearer, or punchier, or livelier etc., but the end result doesn't sound good. With many 1612 in the monitors you might find everything to sound too bright or punchy and end up with dull mixes.

The LM4562/LME49720 (same thing) sounds very good, but in the end I still prefer the 5532.