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ZLB Bookshelf Speakers

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Simon (niss_man) has designed and built these book shelf speakers and he has asked me to have a listen to them and then let him know my thoughts.  So, with my speaker reviewing training wheels on, here we go.


These ZLB (which stands for "Zeus Learner Bookshelf" speakers, I imagine any more refined model will get a name that rolls off the tongue a little easier) speakers have been designed by Simon as a project (and learning experience, hence the name) to see how well he can do on the first try and to see how certain design aspects can work when they are carried through to completion.  They have a 17mm MDF construction all the way around with a 3mm steel plate epoxied to each side, top and bottom, and a steel frame on the front for the drivers to screw in to.  The crossover is mounted on the rear interior and the rear board is screwed in place into a steel frame that is mounted around the interior edge. 

Some construction photos.


The drivers are a Scanspeak 18w/8434 woofer and a Dayton esoteric ES25nd-4.


As you can see from the pics above Simon has used a single bracing rod from side to side, it is also easy to see that they are rear ported.  Such an enclosure should be pretty rigid but still light enough to enable the speaker to be carried around without seriously straining your back.  


These speakers are a proof of concept exercise and Simon has emailed me a powerpoint presentation that he has put together that covers the reasons he has chosen this design and what the pros and cons of such a design and construction are.  It is interesting reading, although it does leave me in the dark a little with some of the terminology.


But how do they sound?  Well, I'm glad you asked.  With the similarities to some of Mike Lenehans designs and driver choice you may expect the ZLBs to sound fairly similar, and in some ways they do, but they also don't.  More details and clarification to follow (probably) but for now I'm going to put this first post up and give Simon a chance to correct me on anything before I move on to the sound side of things.


Back soon!

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Thanks Jeff. I can correct you on one thing, these have a 34mm front baffle (2 layers). These were designed for a course I am doing for the QAC (Queensland Audio Club). If I can get others excited about designing and building speakers then my goal will be achieved. I wasn't really expecting Jeff to post his experience with these on these forums but thats ok. Don't critique them to harshly I hope 😉. I grabed these drivers over a period of about a year (buy when I find a good deal). Woofer is the lower end of the scanspeak range (which for scanspeak is still very good) and the dayton tweeter was meant to be the highest end of their range with the "esoteric" moniker. The dayton tweeter had a manufacturing fault with the back section glued on with the terminals quite close to one of the screw mountings and so was sold (on ebay I think) cheaper than its original price tag so I grab them. They sat at my place for a couple of years before deciding to use them in this project. 

          As these were built to be a basic build (not overly expensive), I just used MDF with some plate for extra strength and anti vibration properties and used Jantzen capacitors with the help of Nigel (another QAC member)  from Speakerbug. I chose the MKP metalised polyprop's for their great bang to buck ratio. This is what I wanted, the speakers to have the greatest of bang for the buck that the universe has ever found.

         The panels were glued by some "Bote Cote" 2 part epoxy and a test sample kit of their undercoat and colour top coat. Not enough colour to finish them to the highest of standard, but good enough for these. The colour is a 2 part paint that is nice and hard. I used a roller to apply the top coat and since the liquid was very thin, it produced a textured finish. Yes and their are some design cues from Mikes speakers as well not that I ever expect these to sound the same, or even similar. The front baffle is the most interestingly shaped baffle I have made and is designed like that so as there are zero mirror image type reflections to the edges to try and get a better baffle diffraction out of this thing. 


Onto you Jeff

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Ah, that's right, double thick front baffle, I had forgotten that.  And don't worry mate, I don't need to be kind, these speakers of yours are doing a bang up job.


They've actually taught me a few things, or at least highlighted a few things that I probably should have already been aware of but wasn't.


Initially I noticed that the ZLBs had a more active treble than my S2Rs.  They were a little harder and a touch brighter, not enough to be a negative trait really just enough to sound more energetic.  I initially thought that the port might be letting out some treble that was bouncing off the back wall (when I took delivery of them the crossovers/back end was installed upside down, the result of some playing about beforehand) and indeed this hardness (an oversimplification but "hardness" will do for now) did drop away once I spun the crossovers about so that the port was back on the bottom of the speaker.  But it didn't disappear.

However I was listening to my Sansuis, for reasons that should be obvious (they're awesome!) at the time and eventually I thought that maybe I wasn't familiar enough with the Sansui combo (NRA and 917 cd spinner) to be certain of what I should be hearing so I decided to do a few swaps.  I was going to swap in a few amp old favorites anyway, so why not then.


The Sonneteer Orton was clean and clear in the top end, as expected but I thought it was a bit light in the bass.  This struck me as odd as the little Orton is actually nice and punchy if the speaker in use is easy to drive and not too inefficient.  It certainly doesn't leave me wanting for bass on the S2Rs (but it just can't manage much on the ML2).  This had me stroking my chin and muttering "Hmmmm" for quite some time.


OK, time for some strategy, if Simon did all his measuring with his own amps then surely if I haul out the Zeus then I will be listening to these speakers as he intended them to sound.  Makes sense, yeah?  So, out comes the Zeus Integrated.  And yep, there was certainly some extra energy in the treble, it makes for a more lively performance with any of the faster genres of music but I was hearing something else too.  A sort of sweetness to some of the mids and less bass than there should be. 

The Zeus integrated doesn't do "less bass than there should be" so something was up.  I'm now quite happy that I know what I'm getting from my interconnects, the Aurealis Dragons have yet to meet an amp they couldn't work well with.  But the speaker cables were my new Duelund 4 wire braid cables and it was just possible that I wasn't as used to them as I should be, they are fairly new after all.  So, out they went and in go the old favorite Redgum Audio Pipeline speaker cables, 7 AWG jumper leads that they are.

Yep, the bass was back in all its solid wonder, there was a little less sweetness on the vocals but in general everything was back to a more even balance.


The extra energy in the treble was still noticeable but it isn't a trait that is negative, just a little different to what I am used to.  It seems to accentuate the "foot tapping effect" of faster music that a completely black background and low noise floor can really damp down on.  There is also more resonance with electric guitar, it just feels more edgey, more feedbacky, more "played with wild abandon", and I like that, I really do.


I have yet to put the Burson PI-160 into action.  That will tell me more about the nature of the speaker box, the Burson can sound quite hard with some speakers and yet just a little bright with others.  I love it with the S2Rs but really dislike it with the ML2s, so we shall see what happens, hopefully this afternoon.  

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I actually did the initial driver measurements with the SKA GB150 amp (I didn't want to break my back carting the heavy Zeus amp to the garage). But I think what you have found is that these speakers are quite revealing of what you connect to them which is quite similar to the zeus amp as well. I use some Canare speaker cable here, which have that bit more fullness to the bass.

    Have you still got those fat taranui speaker cables laying around? They may be a good match as well.

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I actually did the initial driver measurements with the SKA GB150 amp (I didn't want to break my back carting the heavy Zeus amp to the garage). But I think what you have found is that these speakers are quite revealing of what you connect to them which is quite similar to the zeus amp as well. I use some Canare speaker cable here, which have that bit more fullness to the bass.
    Have you still got those fat taranui speaker cables laying around? They may be a good match as well.

Hey Niss Man,
what Caps and resistors did you use the the crossovers?

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I've always been a fan of having more information.  About pretty much everything.  Loved having a shelf of reference books back before the rise of the internet, still like having a shelf of reference books about things that don't seem to be found on the internet (industrial proprietary stuff, some times you can find it but mostly it isn't talked about).  These days while it seems that we have access to more information than we ever have before most of that info is tailored to us.  Made more palatable by its presentation, parred down to size so that anything too complex, too difficult to explain in a two page article, is dumbed down or glossed over and the story is about how cool it is or how much money this thing could make for its inventor. 

Shocking, but not too shocking, interesting but not actually informative, controversial sometimes but never revolutionary as you can't go giving people big ideas.  Playing it safe, but going to serious effort to make you think the thing you are reading or watching is anything but.


Just like the internet, there is a wealth of information on a track (song, cd, download, etc) and yet our audio gear tailors it before it presents it to us.  Filters, both digital and analogue, remove high end noise.  Amplifier typologies emphasize bass and roll off the treble.  And speaker crossovers, while they have to be used to balance the sound coming out of the drivers, are often used to do the same thing too.  


I know many people will say things like "If the design engineer was doing his job right then component X will make every instrument sound as close to reality as possible."  But realistically, the dollar rules and engineers do what they are told if that is what the job entails. 

Components will be, and are, made to attempt to appeal to as large an audience as possible (so as to make as much money as possible) and that will mean they will be made to sound as appealing as they can be.  Or, to put it the way I prefer to put it, they will try to make sure that their component sounds as un-annoying as possible.  Clear up the treble, roll it off so that it doesn't sound hard, harsh or bright, dial in a little more bass, and a little more mid bass because that's what most people want.  Maybe a touch of warmth as well, why not, most people will miss it and those that do spot it may just like it so it can't hurt. 

Remember the four letter word company that starts with a B?  They're popular for two reasons, and only one of them is marketing.  The other is the lack of a severe negative reaction to the sound of their products.


I’m going somewhere with this, hang in there, all will become clear eventually.


So, when we try to system match, what happens when we put together a source/amp/speaker combo where the designers of each all attempted to roll off the treble in their own way?  Or, what happens when the designers of each all attempted to boost the bass, or warm up the mid range?  Disappointment, that’s what.  (or bass heavy, treble light mush, I guess you could call it that too)

Audio components, just like the internet, are capable of displaying a massive amount of information but we often don’t get to hear it because it is presented to us in a modified way.  




Go the DIY path and there is a much greater degree of control over just how much of that audio information is allowed through to the listener.  


So, whether by deliberate intention or as a result of measurements taken and design decisions made, these ZLBs let through a lot of information in the treble region.  And I love them for it. 


I made a comment in an earlier post regarding the Burson PI-160, I wasn’t sure if the Burson would pair well with the ZLBs.  Was fairly certain it wouldn’t work too well actually but it just might tell me something interesting so it was definitely going to be tried out. 


Holy percussive perfection Batman, does the Burson pair well with the ZLBs.  I spent three days in audiophilic bliss with the pair and loved every minute of it.  The expressive treble nature of the ZLBs really let the fast and crisp nature of the Burson out to play.  Drums were just plain brilliant, tight, strong and crisp with a sharp leading edge and a trailing slap prior to the skin bouncing back, loved it.  (we’re talking Luxman L507u territory here, the combo is that good!)  stick taps and mettle brushes came through so musically and so lively.  I haven’t heard a combo that was just that much plain fun to listen to since I had Leema’s first Pulse in the flat. 


There is also a really addictive edge/glare/feedbackish effect on electric guitars too, damn! 

Vocals are good, other instruments are almost as good as guitar and drums, soundstage is nice (but more fun than nice, it is just so lively and vibrant) but pinpoint accuracy is sacrificed for excitement levels and fun factor.  


For light to hard rock this is an excellent combo, and I think I will use the Burson for the final evaluation on the strength of my enjoyment of the last few days.


There is nothing wrong with letting the treble out to play when designing speakers, you just need an amp that will do the same thing. 


Next up is the Xindak, I’ve got it warming up (and in turn the room warming up around it) at the moment.  It sounds very good, more solid than the Burson certainly, but not quite as much fun to listen to.








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And yet still pretty good in the fun to listen to department.  There is a little bit of tingle (of the delightful kind) to higher pitched piano that I don't recall hearing from the Xindak on the S2Rs.  More texture on the vocals as well, I was of the opinion previously that the pre side of the Xindak was letting down the power side (and actually had plans to mod it to see what I could get out of it in pre improvements) but now I'm not so sure, maybe it is just that it wasn't a good combo with the S2Rs.


Those bass drivers must be pretty stiff though because the bass levels I'm hearing here are only barely single-stick-of-dynamite-level explosive and the Xindak comes close to having a megaton yield on the S2Rs.  They will certainly benefit from some running in.


Not enough pics in this thread, so here's the Xindak at work.


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The more pics and reviews the better. I like the jumper leads. Will you be trying a redgum amp with these Jeff?  

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I don't have a redgum amp any more mate, moved on that RG120ENR a while back.

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I've been running the ME240 on the ZLBs for a few days now.  Better balanced than anything before it, might have the best vocals yet, and percussion has an addictive sort of bounce to it.  It feels both eager to please and highly dynamic.


Damn, didn't take a pic.  I'll have to make up for it later.

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Will be nice to have a listen next Saturday in your home. I wonder which amp you will suprise me with. I will cart the Denon S10 ii cd player up with me as well.

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15 minutes ago, niss_man said:

Will be nice to have a listen next Saturday in your home. I wonder which amp you will suprise me with. 

You mean "amps" right?  :)

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