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.Part Eleven

F.A.Q.

By all means send me email, but please let them be about the existing design and not about request to alter the design presented as is.

Reserve the right to retain editorial authority for the sake of clarity. Full names or personal links will not be given.


The following questions from Shane:

Resistors - 15 6.8 2.7 22 Ohms, Can you suggest a power value. Would 10W metal oxide 5% be suitable.

Minimum 5W is OK. I am not sure of the sound of Metal Oxide. I use Dale CW-5 5% series. I get them from Mouser Electronics, but it requires quantities to get reasonable value due to shipping cost. Use quality resistors known to have been accepted for good sound. A little searching online should find something suitable.

Is a laminated steel core or iron core type of coil suitable for the bass low-pass filter ?

I use laminated steel core from Jaycar Electronics - part LF1336,  A$14.50 each. they do the job nicely and cost is reasonable. Since the load seen by the choke is 16 Ohm nominal, 1R DC resistance would be equal to 0.25R when compared to 4 Ohm speaker/load. In the Elsinore it is less sensitive to DC resistance than almost any other design, neat eh?

Also, this also makes it less sensitive to core saturation, so while air core is good, a decent metal or powder works surprisingly well. They still need to be rated high power. Other choke coils should be air cored or audio grade foil types.

Capacitor C3 is 68uF and you specify "non-polar". I am intending to use SOLEN Fast Caps and a 70uF is available. Is this suitable ? Did you have in mind a non-polarized Electrolytic capacitor.

The value 68uF is a standard value, 70uF is not. It is just close enough, but I would be wanting to be out more than that. Yes, I use a standard 100V Bi-Polar, which is the same as Non-Polar. This part does not need to be all that expensive as it works near 600Hz to max effect and is sort of buffered by the series choke, way below the Tweeter's passband. But it is your money.

In the Mk3 cabinet design, the front-most panel is 18mm thick. The tweeter sits flush in the 25mm panel just behind it. Thus the cavity in front of the tweeter is 18mm. All the drawings pertain to a single box; do the felt drawings relate to a single box also?

If so, the front of the four layers of felt sits 6mm out of the cavity. OR are there only two layers of felt for each box; thus the felt is 6mm below the cabinet front?

Correct, it is 18mm. The Tweeter must be flush mounted. It is best that 830875 MidBass NOT to be flush mounted. I used a router for the Tweeter set to 4-5mm depth.

The felt I sourced was rated 6.4mm and I had in mind a three layer arrangement. But felt is a compressive material and in real life it was more like 8.5mm. That made it almost flush with the front panel proper with two layers - and I went with that. So check out the felt you will be using, and get something that is more than 6.4mm for real.
 

These were reasonable questions, not question requesting design changes, but about the existing design.


Hi Joe


Thanks for your response - i will have a go - have located the Peerless drivers in the US (cheaper than UK). Will go for MK3 without separate tweeter panel and let you know how I get on.

Best regards

Martin


Hi Martin.

Please note, use the drawings here: http://customanalogue.com/elsinore/elsinore_4.htm .

Then you will NOT need the Tweeter Panel as shown here:

http://customanalogue.com/elsinore/elsinore_18.htm

The construction will be much simpler and the end result the same.

Let me know if you had understood this as it may not have been clear on the website? http://customanalogue.com/elsinore/elsinore_18.htm is for those who have already made earlier Mk1 or Mk2 Elsinores.

The stuff on http://customanalogue.com/elsinore/elsinore_4.htm has been updated to reflect Mk3 approach.

Let me know.

Cheers.

Joe


Hi

Great website was looking to upgrade my speakers and had been looking for a nice pair of Yamaha NS1000. Now having second thoughts and very tempted to build a set of Elsinores.

Are you expecting to include cut out sheets for Mk3 on the website - rather than the inserted tweeter panel would a one piece panel work as well?

I wonder how the Mk3 speakers compare to the NS1000 - would the bass be as strong with peerless HDS 830875

Best regards, Goran

Hi Goran

Sorry, hadn't gotten around to doing the Cutting Sheets yet. (it is there now). I would do the MK3 without the inserted tweeter panel as the box construction is simpler by a fair margin, but both work quite well. Use the new Mk3 drawings (they have been updated) and Cutting Sheets.

The Elsinores are not bass shy and yes, IMO, the bass will better than NS1000, and that is no criticism of NS1000. The Elsinores have very low dynamic compression that will show up in the bass. In my room they are flat down to 30Hz and useful to 25Hz - I have subs here of more than just good quality, I just don't need to use them. It's not just the bass extension but also the sheer QUALITY of the bass. They are world class. Not my words, but others.

Please go ahead and build them. The DIY constructors who have built them have only been full of praise. No disappointments and only better than expectation.

Let me know how you go.


I'm not sure which version to build. I already expect much work for building, the finish of veneer and slightly angled edges. Is the reason for MK3 only simplicity or better sonics ?

Definitely build Mk3. It is done for BOTH reasons. First it was done to get a better stitch at 7KHz to 8KHz - and then the whole speaker system stays minimum phase all the way up to 16KHz. The fact that it also made box construction easier was an extra benefit. Careful with those angled sides, it so make it no more than 6-7mm. Otherwise the diffraction effects will be different from those I compensated for.



Tubes with outside diameter of 90 mm are hard to get in Germany. Do you suggest any alternatives ? If not, what is the inner diameter of the tube.

The tube I use is 90mm outside and about 86-87mm inside. IF you use a slightly smaller diameter, the tube needs to be a shorter than 80mm.


IF the internal diameter is 80mm the L = 65mm

IF the internal diameter is 75mm the L = 55mm

IF the internal diameter is 70mm the L = 45mm

IF the diameter is in between, the above should give you a good idea. For example if between 75mm and 80mm then make L 60mm etc (this is called interpolation). I think 70mm is too small, but only use if you have to.

To be sure, if you know how to measure the box tuning (using a decent AC multimeter, a frequency meter, test amp and signal generator), then make sure the box tuning is near 33 Hertz. The danger of using too small diameter tube is that the peak velocity in the port is amplified. Larger port are better, but you are limited by something less than 100mm because internal bracing gets in the way. Get as reasonably close to that as possible.


And I figure the Mk3 crossover + box design assumes the HDS 810921/830875 combination. But if I have/decide to go with the PPB drivers in stead of the nomex ones, is it enough to return C2 to 3.9uF?

Correct on the first one. If using 830874 PPB plus new HDS tweeter, then increase both the resistor (to 3R9 or 4R) AND use 4.7uF - then you have the PPB version of the Mk3.

Mk3 MUST use HDS tweeter!!!


Hi Joe.

Clearly much work and experience are embodied in your Elsinore LS design which I have just come across when looking up the Peerless 830875 on the 'net...

I wondered at seeing the square-wave spikes and transient pulse reverse spike until I saw the crossover diagram with its reverse connected tweeter. I am aware of crossover phase changes upsetting an overall response at the crossover itself, but the transient and steady state responses are clearly 'at odds', and this puts me off.

Is there no way this can be corrected ?

Graham
 

Hi Graham

Don't be put off by this - everything is not always what it seems and there is something interesting going on here.

Much research has been done on this subject. What is not clearly understood is that a tweeter connected in phase, most of its output is actually NEGATIVE. The OPPOSITE is also true and that is why it is used. The tweeters rise time if 0.6 millisecond - it only shows up well beyond 10KHz. When this rise time is negative, the rest of the output is positive! Hard to believe but most of the tweeter's output is POSITIVE! The proof has been supplied, read on.

There is an extremely exhaustive explanation given here:

www.customanalogue.com/elsinore/elsinore_17.htm

I know some of it is rather technical, but an attempt has been made to make it least so. Even if you don't understand all of it, read it right through to the end and I think some of it will be clear, if not all the details.

The reason a reversed tweeter can be electrically out of phase is because the 90
phase shift which has incomplete summing of the acoustic output of the drivers, but by allowing phase shift by both drivers (complimentary phase) the tweeter is actually locked in phase acoustically when it is connected out of phase electrically. The alignment of the drivers must then compliment that arrangement.

The Elsinores - and this is measured - is minimum phase up to 16KHz. That is why it produces up to >1Khz square waves and this amazes so much that it augers disbelief. Too bad for the non-believers.

Yes, the fact that the tweeter is electrically out of phase does not show up until 16KHz.

The research of Linkwitz & Riley have made these facts well laid down - as you read between the lines the rule is get the phase right. But it is not widely known or understood, that can only happen when you invert electrically - them are the physics. The fact that L&R proposes 2nd and 4th order does not invalidate the facts even if they don't recommend 1st order. Fact are facts.

Read the page as it extols the virtue of acoustic phase as opposed to electrical phase (you cannot have both). The benefits are multiple.

Cheers.

Joe
 


Re Mk 3, is the rear tweeter stiffening panel still required, it makes it three inches?

I somehow knew somebody was going to ask this question. The answer is YES!

By making the 25mm Sub Front Panel ONE piece, I have actually weakened it. I know it doesn't look obvious.

Much of the construction and bracing is based on thinking by R&D at KEF during the Fincham/Cook era. In fact Raymond Cook used to show that longitudinal bracing was superior to lateral and/or edge mass load/bracing. He did this during talks and showing how different panels audibly sounded with different types/methods of bracing. The rules are simple once understood. It is understanding mass versus stiffness. Longitudinal bracing where the brace is off centre (asymmetrical) is better than lateral bracing. Bracing the edges of a panel is totally ineffective. That means the joins of the box have little bracing value.

The original box design meant that the Tweeter was mounted where the box has its greatest strength and rigidity as well as concentrated mass. The Tweeter Panel was set behind two 43mm thick panel, the small dimension of the panel and the lateral (front to back stability) was rated good under those conditions. It is 230mm by 200mm and 25mm thick. Try to make that bend or bow. The more 'cubic' the shape the harder it will be to excite. Whereas the same amount of the same material made thin and larger in other dimensions, will vibrate like crazy. They will both have the same mass though. It is mass AND stiffness that counts.

The two 43mm thicknesses in front of it means lateral mass AND stiffness is high. Simple really.

Making the 25mm Sub Front Panel a single piece and mounting the tweeter on it meant greater potential longitudinal bowing (like a violin) of the Front Panel. This causes the lateral stability of the tweeter is weakened, it is more likely to move to and fro. The tweeter operates at frequencies where the wavelengths are small - that tweeter must be as stable as possible and not move backward or forward. Or you lose information and 'focus'. Time smear is the result.

Also, it means the internal volume will stay the same, although this is of lesser account.

Hope that is clearer.
 


In your experience can I drive these with 25w per channel valve amps?

Absolutely. In fact a 25 Watt amp with these speakers sound like 100 Watt with other typical speakers. The Elsinore goes LOUD with not so many Watts. I use mine with 30 Watt tube amps - and I have power to spare.

Hans Hammerbauer in Switzerland tried the 18 Watt Vacuum State DPA-300B amps ($16,000) rated 18 Watts and found that was plenty in an average room. That just makes the Elsinores an even better bargain.
 


Hi Joe,

I am interesting in building the Elsinore loudspeaker. Please provide some clarity on the wave guide wedge. This the wave guide used on the final design.

My understanding was it assisted in using a low crossover point and provided the right acoustic load. Mk3 appears not to use the waveguide? Yes/No..

Hi Ian

Aligning the impulse/step response to line up properly, so that the point at which the Tweeter's impulse goes positive and lining that up in time when the impulse of the MidBass driver also goes positive - necessitated that the tweeter mounted about 29mm behind the MidBass' mounting flange to mounting flange. The correction amounts to about 60microSeconds - which means the Elsinores end up being minimum phase to about 16KHz.

Hence the waveguide is now shallower and it was decided to use felt. It also made Mk3 box construction simpler. I like the idea of waveguides, but the time alignment was more important. It is still a shallow waveguide. Interestingly, there is evidence that waveguides actually helps build up off axis response - the tweeter beams less. This shallower waveguide still does that.

If you haven't read this more recent page, then this will explain further the rationale behind the time alignment, especially towards the end of the page:

http://customanalogue.com/elsinore/elsinore_17.htm

BTW, if you are in Sydney, please come around for a closer look and listen. You are most welcome. The number of people building the Elsinores continues to increase, but the proof is in the listening. Most speakers sounds like toys in comparison as speakers that produce real scale (whether small or large) are either rare and/or expensive.

Cheers.

Joe
 


Hello Joe.

Just ran across your design on diyaudio.com. Looks really great; I am thinking about giving it a try. I would choose the Nomex woofers and the HDS tweeter or maybe a seas excel or Fountek ribbon. My main question - would I use the same crossover if I wanted to turn the drivers so that the cut sides are vertical, and therefore could go with a narrower baffle? I would keep the box volume the same by making it deeper. (name with-held)

(Take the following in the right spirit and do not be discouraged building the Elsinores as is.)

Hi

Please avoid asking these kinds of questions. I am a designer for hire and simply can't afford the time re-designing the Elsinores all over again with different drivers and other changed parameters. It is a gift - and a valuable one at that - and you have permission only to build a personal pair and NOT FOR PROFIT. The design is provided as is - the complexities are enormous and the variables uncountable. I cannot predict many changes you may have in mind and have not the time or inclination to sort out even a small number of them, out of necessity and sanity.

Ribbons? They won't work in this design as they rarely have enough bandwidth to suit here.

Narrower baffle? Diffraction and step response compensation now won't work with existing crossover. Your tonal balance could be all wrong. Any ideas how critical the width of the cabinet is? More than a few millimetres could create a different balance. Would you suggest a boat with a narrower keel to a boat designer? He might suggest it would sink, right?

Different tweeter? All acoustic measurements needs to be remade of all drivers and remodelling the crossover, and only if the tweeter has the right characteristics. You are asking me to buy the driver and crossover components? And then spend dozens of hours in integrating the new tweeter? I cannot afford to respond to every whim and the results may not even be up to scratch.

Any other questions? Please think first what you are asking, OK? If somebody gave you a present, would you have thought it good manners to make suggestions after the fact. I suspect you wouldn't.

So, bottom line. Either build a design or build a disaster. But if you stick to the plan, chances are you will be overjoyed by the results and no headaches for anybody.

Thank you.

Joe R.

Hi Joe. No, you got me wrong - I would never think of asking for more ! I think that your providing the info that you already have is awesome for the amateur looking to build a pair of speakers..

Fair enough. If anybody wants to make changes, it is no longer my design, but theirs (go right ahead - but don't put my name to it). If I recommend design changes it is my reputation that is on the line and I have a lot more to lose. I have always retained a right to veto a design when dealing with people in this business. IF I recommend something I have to be right (at least satisfied in my own mind). This is not vanity but hard-headed reality. I did not make the world the way it operates.
 


Although I am a audio nut, I know almost nothing about speaker design (as you can probably tell by my question).. I was just asking a question about how the design would work if I narrowed the front baffle. Thanks very much. Best regards,

An Example of a Single Development Cycle

Re baffle, this actually changes the frequency response MAJORLY. Even bevelling the edges will change the response as will any change to the front baffle.

The reason I did NOT specify bevelled edges is because not all home constructors are able to do a good job of that. If this was a commercial design I would have liked bevelled edges. But ANY changes to the front baffle (or anything else) means pulling out and setting up a bunch of equipment, disconnecting the crossover, measure the acoustic responses of ALL drivers, both far-field and nearfield, ON axis and OFF axis sets. Put away equipment (space is always a premium), merge farfield and nearfield files and reconstructions with the electrical measurements of drivers (which also must be done IN-box) into complex transfer characteristics files of each in-situ driver - complete Hilbert-Bode transforms (a strict mathematical relationship between amplitude and phase) from accurate calibrated data. And at this point we have only started. ONLY NOW CAN WE reconstruct the overall  project file and start the analysis. Want to count the hours so far... ???

Now we make the required changes to the crossover (and if the required parts are not to hand that means spending money). Then we pull out all the equipment again to check and verify that our modelling is correct. You must always start with the HARDWARE (calibrated measurements of the 'bits'), then move into SOFTWARE (reconstructions and modelling) and then finally back to HARDWARE to complete/verify the development LOOP.

Often some fine tuning is still required (not just listening, yet to come), such as in-room 1/3rd and 1/6th octave pink noise. As with the last change of tweeter - to the current HDS tweeter - this showed up that there was still possibly too much energy in the presence region. Going back to the modelling showed that the component that had the single largest effect on this area of the response, was the main series capacitor to the tweeter. Other components in combination would also do the trick, but there were other complications. It was decided that the cap had to be tweaked VERY carefully.

The speakers were hauled to a different locations and with other trusted ears and we did fine tune that - it resulted in a cap value reduction. It was decided that we should go for no artificial boost in the presence region, and YES, at lot of commercial speaker DO exactly that and even horrendously priced ones. But the Elsinores now utterly avoid it and is better because of it. In OUR opinion (yes, there is a BUNCH of people involved, but I have the chief design responsibility).

I just want to give an idea of the process involved - and I will be posting this, or the substance of it, in the FAQ page (that is why I have spent a bit more time on this than I would otherwise have)...

Please don't feel discouraged in building the Elsinores. You will benefit from a huge amount of work, not only upon my shoulders but also the help I have received kindly from others.

And you can always say to your fellow listeners that you had a sparring match with the designer.   :-)

Cheers.

Joe R.


 

 

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Last modified: Monday June 08, 2015

Just had a terrible thought. If "intelligent design" is unscientific, then who will design our audio equipment?