Speaker mods

[drummerman]

The speaker baffle is a fairly important part of the cabinet. It is there to provide a solid foundation for the driver without adding additional vibration. Thing is, everything vibrates just not necesseraly at the same frequencies.

I guess at worst you have a front baffle which is the same thickness as the rest of the cabinet and which is simply screwed or glued on. Add the inevitable screw fix method of the driver/baffle interface and there is plenty of scope for mechanical interaction.

Along with the Usher I use a couple of elderly but lovely MS speakers regularely. They are fantastic as the xover is minimal intrusive and a lot of attention has been paid by the original MS company with Robin Marshal to develop drivers which integrate with each other rather than the usual buying drivers of an
OEM or a few well known other companies and then design a crossover around it to get around the driver integration issue.

In essence, these were made to measure speakers rather than off-the-peg.

They've also moulded the Mid-Bass driver (solidly) to the composite plastic baffle! Depending which way you look at it, that is either a negative or clever. - Blow one and you need a whole baffle but it does take the wood screws away from the driver basket (although they are still used to secure the baffle to the cabinet).

As much as I love the tight bass, open imaging, rythmic drive and good power handling of these speakers (MS10iPearl, MS20iPearl) there is always room for improvement andI've tackled the areas where cost-saving has been evident (This was a budget speaker rather than 'esoterica');

Thickness of the enclosure walls is average, bracing consists of one inner baffle, running the height of the enclosure to which the front baffle is fixed to with the necessary cut-out for the drivers. In addition there are a few triangular pieces of wood near the corners of the enclosure to add a modicum of stiffness. Damping material is one piece of fibre wool which covers the rear-baffle and crossover which is attached to the speaker terminal plate.

Some time ago, I've rewired the speakers (all of them, inluding Ushers) using good quality copper cable for the mid-woofers and a thinner, silver plated cabling for the (metal) tweeters. Luckily I didn't
at that time hardwire everything but used spades against my own judgement (I had a feeling I was going to do more so de-soldering numerous times was impractical).

Anyways, I have added an additional two, slender internal cross braces to the MS10's. I then added egg carton foam to the remaining top, bottom and side walls. In addition I have used round foam pads of increasingly reduced diameter (think cone) to reduce backward radiation towards the cone of the bass driver basket outriggers, four in all.

These easy to do changes have made the sound even less boxy and reduced sound radiation back through the cone. Result is better texture and cleaner transients.

Move forward a couple of months and off comes the front baffle again. - Whilst stiff and 'relatively' resonance free, there are handy stiffening cross braces and compartmentswhich divide the composite front panel (and even the bass driver outriggers). I got some PVA glue and filled every bit I could, inserting stainless steel nuts everywhere which are now covered by the glue.

Result is a very inert and solid front baffle, pretty much 'dead' to knuckle raps.

I then cut some gaskets for both the entire front baffle and tweeter (to further isolate that unit, it is fitted conventionally to the front) out of bonded cork which I got cheaply in my local craft store.

I dont claim miracles but the sound now has even better and more solid imaging and transient response. This is more obvious as volume increases but even at low listening levels there is a composure and fine musical detail that just wasn't there before and it was a pretty decent speaker to start with.

I love hifi. Next come the MS20's for the same treatment.

regards

 

[Crossie]

Nice write up. Any chance of some pictures of your handiwork?

Cheers.

 

[drummerman]

Will be a pleasure. Give me a few days and they will be up. My phone (camera) should be back by the weekend.

JD, if you read this, perhaps a DIY section could be made? - I think I did ask once before but it probably got lost.

regards

 

[altruistic.lemon]

I agree, cabinet design is paramount, and cheaper designs do skimp on bracing/ cutting unwanted resonance.

The BBC papers on the LS3/5a are in some ways th seminal work on cabinets and materials, though a bit outdated now.

By the way, you might want to think about using epoxy to stiffen the cabinets. I haven't tried it yet, but will be ripping my first attempts, the LS3/5a clones, to pieces soon and intend to then. Logic says it should work, and may remove the need for some bracing. I get headaches working out internal volumes taking into account bracing!

 

[davedotco]

Sounds like fun, I used to love projects like this though sadly I no longer have the space.

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

That would be an interesting project!

 

[Crossie]

DIY is the way to go for VFM.

 

[char_lotte]

Interestingly one of the tech guy's I know has started to build his own speakers at work.

Only managed to have a quick chat with him so far but it strangely alluring...

 

[drummerman]

@ A/lemon; That sounds interesting. Where did you manage to get the drivers from for your LS3/5a clone? - Epoxy is probably another good idea. To completely dampen something you need to cover it in some material many times the weight of the item to be damped ... . I think the best we can hope for is to shift the resonance frequencies to a place which is not so obtrusive and get rid of the nastiest blips. I was careful not to apply to much damping, a tiny bit of reasonably controlled resonance is handy with a small speaker otherwise it could end up sounding flat and dead. I got no means of measurement so its all done by the ears of yours truly, for better or worse but most things are reversable ... with a little bit of effort. As it happens, the small MS10 has worked out splendidly and I currently got Brubeck on vinyl on. - 'Far more Drums' has to be heard to be believed.

I dont think one solution fits all so there is plenty of scope for experimentation. I know that Totem use no damping materials in some of their products other than bitumen paint, Spendor use the thin wall principle with damping pads etc

@davedatco; Without getting to sentimental I agree, Epos made some very nice speakers and they tackled some the most common issues with interesting ideas. The minimal crossover and bespoke/in house developed drivers are part of that, as is a very nice metal tweeter.

@crossie; You're right. Apart from the personal involvement and knowledge gained about what you use DIY is a great way of doing things cheaper. I have worked on amplifiers, re-built my first turntable and cobbled on speakers. It has not always been successful and you need to get the tools first but I have not regretted any of it, quite the opposite. - I'd still like that McIntosh system though.

regards

 

[GSB]

JD, if you read this, perhaps a DIY section could be made? -

regards

+1

 

[chebby]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

 

[steve_1979]

Nice write up. Any chance of some pictures of your handiwork?

Cheers.

+1

Sounds interesting. I'm looking forwards to the pictures.

 

[Nelly]

JD, if you read this, perhaps a DIY section could be made? -

regards

+1

me too modded my own actives sound great would love a diy thread

 

[davedotco]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

You need to do a little research on what crossovers actually do, taking in such factors as level matching, bandpass filtering, time alignment, driver eq and the rest. If you are building an integrated system, ie where the crossover is specific to that particular speaker, then all these factors can be taken into account, irrespective of whether the crossover is active or passive.

In the example under discussion the TX818 crossover does pretty much all of these things except the driver eq, so the output from the drivers will be unmodified. For this to work in a hi-fi speaker you need to have drive units that have a response that is flat and smooth thoughout the operating range and that can be expensive if we are talking about OEM units.

There are a few speakers that are built diferently from the rest, Robin Marshalls designs for Monitor Audio, Epos, and MS are a good example as they use drive units purpose built for each speaker model.

These drive units have, by design, the correct response for the job and require no eq and minimal crossovers, so such designs are ideal for active experiments using the TX818.

 

[drummerman]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

Chebby, I think I would want a speaker for which I had accurate measurements for each drive unit (think Scanspeak etc) before I'd start to convert to active. I dont know if these are available for the MS but I have not seen any.

regards

 

[davedotco]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

Chebby, I think I would want a speaker for which I had accurate measurements for each drive unit (think Scanspeak etc) before I'd start to convert to active. I dont know if these are available for the MS but I have not seen any.

regards

I am not sure how much help accurate measurements would be in this instance, you would need to be able to design your own crossover with all the requisite eq for the drive units or at the vey least fing an electronic crossover with user programmable dsp to do the job.

This is why the MS speakers are ideal for experiments of this kind. As you point out the drive units are specific to that particular speaker and already have a response that is flat across their operating range. The drive units need no eq and minimal crossover, in many of Robin Marshal's designs the bass driver is driven full range, the upper frequency roll off being dictated by the design of the unit itself.

 

[jiggyjoe]

I have converted my ms20i pearls to active drive and as davedotco said easy to do with this speaker.

Very simple crossovers, inductor on bass feed to roll off the high frequencies and bypassed capacitors on the tweeter feed to roll off the low frequencies.

Sound between active and passive drive is not that different to be honest, The active speaker is a bit more tighter through the bass but not as good as the passive through the mid and treble.

I suppose this could be due to the extra electronics of the electronic crossover in the signal path so adding some 'character' to the active speakers sound.

maybe active drive using digital dsp crossovers would sound cleaner,

I dont think its worth going active unless you have big 3 way speakers, and then i think i would leave the passive network to the mid and treble and just run the bass driver active.

 

[davedotco]

I have converted my ms20i pearls to active drive and as davedotco said easy to do with this speaker.

Very simple crossovers, inductor on bass feed to roll off the high frequencies and bypassed capacitors on the tweeter feed to roll off the low frequencies.

Sound between active and passive drive is not that different to be honest, The active speaker is a bit more tighter through the bass but not as good as the passive through the mid and treble.

I suppose this could be due to the extra electronics of the electronic crossover in the signal path so adding some 'character' to the active speakers sound.

maybe active drive using digital dsp crossovers would sound cleaner,

I dont think its worth going active unless you have big 3 way speakers, and then i think i would leave the passive network to the mid and treble and just run the bass driver active.

To be honest, it is morelikely to be the (non) effect of the inductor which may well tame the inband response of he bass unit by reducing the output around the point the cone srarts to break up.

The more expensive ES14 had a better behaved bass driver and needed no inductor to modify it's inband response, an even better subject for activation if you can find a pair.

 

[jiggyjoe]

Given that the epos es11 and 14 have no crossover components on the bass drivers they are actively driven. Only a single capacitor is used on the tweeter to protect it from low frquencies.

I have heard them sounding great on naim and exposure amps.

I think drive units have come along way in the last 10 to 15 years and the newer metal and ceramic drivers just dig up so much more detail than the old polypro drivers from then.

I really want to build a nice 2 way floorstander using accuton drivers, but man they are pricey.

 

[davedotco]

Given that the epos es11 and 14 have no crossover components on the bass drivers they are actively driven. Only a single capacitor is used on the tweeter to protect it from low frquencies.

I have heard them sounding great on naim and exposure amps.

I think drive units have come along way in the last 10 to 15 years and the newer metal and ceramic drivers just dig up so much more detail than the old polypro drivers from then.

I really want to build a nice 2 way floorstander using accuton drivers, but man they are pricey.

the only problem I encountered with the ES14 was a slight harshness in the midrange, I put this down to the fact that the tweeter still had considerable output in the mid due to the slow roll of of the simple 1st order capacitive filter.

Similarly the bass driver was putting out more high mid than would be ideal, hence the thought that an active crossover would be of considerable benefit.

FWIIW, the Onix OA 21 amplifier was a particularly fine match with these speakers, much better than the more expensive options you mention, sadly they disapeared sometime in the early/mid 90s.

 

[drummerman]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

Chebby, I think I would want a speaker for which I had accurate measurements for each drive unit (think Scanspeak etc) before I'd start to convert to active. I dont know if these are available for the MS but I have not seen any.

regards

I am not sure how much help accurate measurements would be in this instance, you would need to be able to design your own crossover with all the requisite eq for the drive units or at the vey least fing an electronic crossover with user programmable dsp to do the job.

This is why the MS speakers are ideal for experiments of this kind. As you point out the drive units are specific to that particular speaker and already have a response that is flat across their operating range. The drive units need no eq and minimal crossover, in many of Robin Marshal's designs the bass driver is driven full range, the upper frequency roll off being dictated by the design of the unit itself.

Both tweeter and mid/bass driver will still have a break-up mode, no matter how beningn no?

The fixed phase plug is a good thing though as it prevents the usual phase cap/dome acting like an ad-hoc tweeter.

regards

 

[davedotco]

On another thread someone mentioned that his Onkyo TX818 A/V amplifier has built in electronic crossovers and plenty of power amplifiers to properly bi-amp suitable speakers.

Clearly the relatively simple crossover can not equalise driver irregularities but a speaker such as those you mention or, my favourite Epos ES14, which have purpose made drivers and minimal crossovers would be ideal.

Ok, so my Mordaunt Short MS20i Pearl speakers have removable bridges to allow bi-wiring or bi-amping.

I go out and score myself an Onkyo TX-NR818 with all this DSP & electronic x-over gubbins and enough seperate amp modules to have one dedicated to each of the four drivers.

Do I rip out the speaker's own crossovers (and have a true active set-up with seperate amps and electronic crossovers built into the Onkyo receiver) or leave them in place and have some kind of conventional bi-amped system with a bit of DSP thrown in?

How would this work?

[EDIT] It's ok. They explain both approaches here...

http://websupport.onkyo.net/digitalprocessingxover/technology02.html

...missed that bit.

Hmmm. So it seems a true active topology is just one of the available modes (so long as the old crossovers are removed and the drivers are directly wired to their respective terminals).

I think I ought to do a bit more research on this and drop Onkyo a line or two on whether any old - modified - two-way (like my MS20i Pearls sans crossovers) would be ok or whether a specific brand/type of 'crossover-less' loudspeakers have to be used in order to be compatible.

Chebby, I think I would want a speaker for which I had accurate measurements for each drive unit (think Scanspeak etc) before I'd start to convert to active. I dont know if these are available for the MS but I have not seen any.

regards

I am not sure how much help accurate measurements would be in this instance, you would need to be able to design your own crossover with all the requisite eq for the drive units or at the vey least fing an electronic crossover with user programmable dsp to do the job.

This is why the MS speakers are ideal for experiments of this kind. As you point out the drive units are specific to that particular speaker and already have a response that is flat across their operating range. The drive units need no eq and minimal crossover, in many of Robin Marshal's designs the bass driver is driven full range, the upper frequency roll off being dictated by the design of the unit itself.

Both tweeter and mid/bass driver will still have a break-up mode, no matter how beningn no?

The fixed phase plug is a good thing though as it prevents the usual phase cap/dome acting like an ad-hoc tweeter.

regards

Absolutely, as mentioned in my last post.

The point is not that they do not have breakup modes but what specifically you are going to do about it, even with acurate response graphs.

But then I could be selling you short, maybe under that fine dress lurks a highly competent electronic/audio engineer, I think you should come clean DM.

 

[chebby]

How will a TX-NR818 'know' what active crossover/DSP parameters to apply when presented with a crossover-less pair of speakers? Will it analyse them in some way? Or does the human have to enter information from driver manufacturer's data-sheets and other info like cabinet dimensions and cabinet type?

 

[davedotco]

How will a TX-NR818 'know' what active crossover/DSP parameters to apply when presented with a crossover-less pair of speakers? Will it analyse them in some way? Or does the human have to enter information from driver manufacturer's data-sheets and other info like cabinet dimensions and cabinet type?

You have to set the crossover frequency from one of the dozen or more available and set the levels for each band along with any correction for baffle alignments, the Onkyo websight says you can do all of this though it does not show how.

Equalising each drive unit is not offered, unsurprisingly at this level, though I believe some pro crossovers use programmable dsp to do just that.

 

[chebby]

How will a TX-NR818 'know' what active crossover/DSP parameters to apply when presented with a crossover-less pair of speakers? Will it analyse them in some way? Or does the human have to enter information from driver manufacturer's data-sheets and other info like cabinet dimensions and cabinet type?

You have to set the crossover frequency from one of the dozen or more available and set the levels for each band along with any correction for baffle alignments, the Onkyo websight says you can do all of this though it does not show how.

Equalising each drive unit is not offered, unsurprisingly at this level, though I believe some pro crossovers use programmable dsp to do just that.

So would you say - from your expert point of view - that this is just a worthless gimmick or that Onkyo are on to something?

 

[davedotco]

I think it is pointless for all but a handfull of diy enthuiast.

Any crossover, passive or active, really needs to be specifically taylored for individual speakers and I think this is essential for critical use.