The "Elsinore Project" Thread

Thought it best to consolidate the inquiries re the Elsinore Project into a single thread, so issues can be dealt here.

We are currently as of June 7th, 2024, up to page 298, click on this link.


March 1st, 2023. Elsinore Mk6 "ULD" Version. These are very expensive Purifi Audio "ULD" drivers.


There are three variations of the Elsinores:

The "MFC" uses arguably one of the best polycone drivers. Very high sensitivity.

The "NBAC" is the latest variation, uses the same driver but with black anodised aluminium cones. The "NBAC" requires a more powerful amplifier, roughly about double, but is still incredibly amplifier friendly, as all Elsinores are.

The "ULD" is the premium Elsinores, using extreme Purifi Audio drivers that are of the highest quality available. As high sensitivity as the "MFC" and around 20% more efficient. One manufacturer and friend has said that to manufacturer and sell the "ULD" would mean around $50.000 retail.

Nobody manufacturer make a speaker that measures anything like below:


This speaker looks like a resistor to the amplifier. As close as possible, above 25 Hertz, the amplifier will draw the same current at all frequencies. This makes the amplifier's output impedance largely cancelled out. These speaker can be driven by all amplifiers with an impedance from zero to infinity. They are also suitable for so-called current-drive which is becoming more common and has an increasing following. All Elsinore variations are suitable with amplifiers like Nelson Pass First Watt amplifier. This is the most amplifier friend speaker designer ever! Until somebody starts using this approach to speaker design.
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Let's get the ball rolling with PoorSound earlier inquiry.

PoorSound said:
i was talking about swapping the Vifa out of the original design i posted, with the Peerless HDS. Would that be a problem?

Go ahead and build the boxes. If you look at the website now, note it announces the updated Elsinore "Mk2" and the recommended drivers are different. The Vifa XT25 tweeter was judged less than ideal being a 4 Ohm in an 8 Ohm speaker system. That 4 Ohm is totally exposed because of the high sensitivity (if it was lower then a series padded resistor would have kept the Z higher). So the search went out for a compatible 8 Ohm tweeter and also one that was hopefully more than 91dB/2.83V.

You can still use the 6.5" HDS PPB but my preference in Mk2 uses the Nomex 830875 and, yep, you guessed it, Peerless HDS Tweeter. Not the older HDS but the newer 810921.

The crossovers only has resistor value changes to 6.5" drivers, but has a different hi-pass to the tweeter; same component layout but quite different values. It also includes a conjugate filter that not only flattens the large Z peak around 1KHz down to about 12 Ohm as well as greatly reducing the negative phase angle (electrical) caused by the tweeter's main coupling cap just below the crossover.

The Nomex version is also about 1dB more sensitive, is now a genuine 8 Ohm design and is largely within 6-12 Ohm above 100Hz. The system was modeled with amplifier output impedances as high as 3 Ohm, so SETs and zero-feedback tube PPs will have no problems and the amplitude (frequency) response is hardly modulated by the output Z.

This afternoon we heard the Reference 3a Veena speaker at Audiophile Society of NSW. The Veena is rated 89dB but the Elsinore was judged about 3dB more sensitive. This latest version is VERY easy to drive for a multi-way type speaker.

The new Peerless HDS tweeter is, IMO, a real honey. I hope the DIY fraternity takes it to heart. It is quite an improvement on the Vifa XT25. If any of you guys are considering using it, go for it! I have issues with the more expensive Scan-Speak/Revelator tweeters and I am not the only one. There are some published distortion figure I am sure others have seen, like Zaph's. The new HDS tweeter not only measures low distortion, it sounds that way.

I intend to do some distortion measurements of my own and compare it to other tweeters I have here including XT25.

Re movies: Build four of these and... whew! The SPL capability would be awesome. No need for subs, trust me, they have quite a wallop in the bottom. Modest power of 35W/ch in my room and a single pair are capable of concert level with ease, now four? Whoa!

Joe R.

PoorSound said:

I'm a little torn here! I have all the components (i decided not to mess with your design and go with the XT25.) I don't have the boxes built so i could possibly go with the Peerless tweeter...what do i need to do? what do i need to replace in the crossover? I was a little dissapointed i didn't get the use the Peerless HDS tweeter so i hope i can make this work! Will the Peerless still be horn loaded?

Also, Joe, while i get to talk to you here...
I got all my components from Solen. I copied your crossover completely , but they sent me one wrong component. i think it was an inductor. Your crossover has a L161.0, but solen sent me the L161.1. will this make an audible difference?

Thanks alot

1.1mH will not make a big difference, the parallel resistor, if changed, would make a bigger difference than the inductor.

Please note that the Elsinore Project is just that, a project. I can apologise for the changes being made, but hopefully you can see how things can go awry as things are in a state of flux. But with the Mk2 things should settle down.

The website needs to be updated and will be asap. The Mk1 still works absolutely OK, but Mk2 uses a better tweeter, is also more suitable for tubes whereas Mk1 is better off with Solid State or tube amps with lower output Z.

Joe R.
Please note that this material is a preview of what is yet to appear on the website.

Here are my provisonal notes on tweeter selection.

The following were based on the Nomex version, but also applies to
PPB version.


Has flattest response, especially on axis, but suffers from poor
off axis response above 10KHz. Also lacks sensitivity in comparison
to the other three. While rated at 4 Ohm, in reality it is a 3 Ohm
Tweeter. The over-all impedance drops to below 4 Ohm above 5-6KHz.
This can cause the response to droop down from 2-3 KHz with high
impedance amps (some are up to 3 Ohm) Not a problem with power amps
that have low output impedance, such as solid state. Also push-pull
tube amps that use feedback to get output impedance well below 1
0hm. Price is reasonable but more than DX but less than HDS.


Not as flat response as XT but does NOT suffer from weak off axis
above 10KHz as much. It is also ABOUT 2dB more sensitive. It was
hoped to help keep the impedance higher than the XT. Approximately
the same 3 Ohm but added padding to bring down should help. But
in reality that did not work out. Price is lower than XT but it
has some advantages and disadvantages, I do over-all consider it
as good as XT. Take your choice.


Warning: More expensive, has least best response and similar
exaggerated HF as DX but better off axis response than XT. The
reponse suffers from a narrow lack of energy centred around 6KHz.
This can largely be fixed with a minor addition to the Diffraction
Wedge. Both XT and DX encorporate Ring Radiator in the outer
surrounds. The HDS surround is large than normal but no Ring
Radiator. This is the likely explanation for the 6KHz dip and
it is related to diffraction effects. But it can fixed by adding
two pieces of felt.

But advantages include arguably significantly lower distortion
than the other two AND it is rated 8 Ohm (again in reality 6 Ohm)
and sensitivity high, near that of DX. These two combined means
that impedance only drops to 6 Ohm. As a speaker system where
the impedance does not drop below 5.6 Ohm it can then be rated
as an 8 Ohm speaker system.

Another advatage is the electrical phase angle is even more benign
than the other two, making the speaker system even more easy to
drive. Finally, the voice coil is not driven as hard and the 'in
situ' temperatures will be a lot lower than the other two. But it
also contributes to the lower measured distortion AND less dynamic


Here are the new Impedance and Electrical Phase plots:



As can be seen, the impedance stays well within the 12-6 Ohm envelope. The lowest phase angle is -10 degrees just above 2Khz where Z is 8 Ohm. As stated before, it's when a low phase angle coincides with low Z at the same frequency, this is where amplifier demands become unacceptable. What we have here is a benign load and good system efficiency and sensitivity above 90dB.

Joe R.
HDS Tweeter rules this roost!

PoorSound said:
Well its taken care of! I phoned Solen and had them send out the newest Peerless HDS tweeter and component parts.

Are you still using the Horn with the new tweeter?


Re 'horn' the answer is yes, and please keep the dimensions as shown. The acoustic centres of the top three drivers match with respect to 2.5M to 3M within millimetres, and the predicted response relies on getting the same dimensions and shape around the drivers.

Re the HDS tweeter I spent a number of hours yesterday measuring the distortion of the three tweeters I have tried in the Elsinores, the HDS, Vifa XT25 and Vifa DX25. I note that these three are also measured on Zaph Audio's website. I did THD, IMD and 2nd to 5th order graphs (similar to Zaph's, but using Clio rather than his SoundEasy). There is a reasonable correlation with Zaph's results and mine, and can confirm the HDS not only sounds lower distortion but also measures that way.

I will post graphs and numbers here asap. They will eventually be posted on the website as well but will appear here first.

Should be of interest to others whether they are considering building the Elsinore or not. The HDS deserves to be used by others IMO.

One thing I would appreciate feedback is C11, whether there is a preference between 3.9uF or 4.7uF. At the "factory" the former was considered more accurate but 4.7uF may be commercially better as it adds something to the presence region.

BTW, you are the 14th person I know of that either has built or are in the process of building the Elsinores. Thought you'd like to know. :)

Joe R.
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right on!

My dad used to have a set of Koss speakers...they were built with peerless drivers. they discontinued the tweeter, but it was also used in Polk Audio was the rectangular one, i can't remember the model #.
anyways, we built a 3 way speaker using that tweeter, a Peerless dome mid, and an 8" CSX Peerless woofer. they sound pretty good! we built those about 7 years ago so i wanted something different, and stumbled upon your website. my dad and i both fell in love! i'm building a set and if they are what we expect them to be, he's going to build a set as well.

i'm really excited about them. my concern at this point is the port seems somewhat small...will that make a big difference?
Keep up the enthusiasm...

PoorSound said:
right on!

i'm really excited about them. my concern at this point is the port seems somewhat small...will that make a big difference?

Keep up the enthusiasm...

This speaker goes very loud with 50W and using that as a basis for calculating vent mach should be about 0.16 at that power. But we did try a 300W amplifier and found no real world problem. Also, this is a rather sub-tuned vent with a peculiar effect. The Fb is 34-35Hz but the max output of the vent is below 30Hz. The whole alignment is rather like a sealed box but with the vent limiting sub 30Hz excursion. It's output is not maxed to the full. I have spoken to a couple of other designers about this affect and the port actually acts as a 'brake' on low frequency excursion. So far it is an observed effect and it needs looking at some more. But in the meantime there is no reason why not to use it.

I am not sure if you are familiar with/heard of the Duntech Crown Princess speakers (sealed). They have about the same foot print but way taller. Yet the rather smaller size Elsinore have way more bass extension and sheer bass power (and nowhere near as power hungry). BTW, Duntech is still a going concern here in Sydney and are working on new models for the US/Canadian market. I am on good terms with them.

Joe R.
Oops sorry i just realized i wasn't very clear with my post.

Solen sent me a small port tube...quite a bit smaller than the one in your design. i was just checking to see if that will make a difference in sound. the port tube is only 2"! Seems quite small to push that much air through it.

Thanks for all your help!
PoorSound said:

Solen sent me a small port tube...quite a bit smaller than the one in your design. i was just checking to see if that will make a difference - Seems quite small to push that much air through it.

Thanks for all your help!

Your local hardware store should have some 90mm PVC tubing used in plumbing, or try a plumbing supply store?

I too have not been able to find a ready-made port down here in Oz. There is a 100mm gap between the two vertical braces (rear panel) so that limits the size to that. Could use 3" or 80mm, but the length would need to be shorter to tune box to 35Hz and will also mean a significant increase in vent mac and possible noise.

I will post tweeter distortions of Peerless HDS, Vifa XT25 and DX25 either late today or tomorrow latest.

Joe R.
Looking forward to it Joe!

for the port..i'm going to try this small one and see how it sounds. if it sounds funny i'll just make the hole bigger and use the port outta my old speakers. they are a decent size. not exactly sure what the measurements are off the top of my head.

i went and purchased my polyfill today. i'm hoping my boxes will be done by next week.

i'm using a Behringer A500 power amp, being fed by my Harman/Kardon AVR330 receiver. I beleive the amp is rated for 160watts at 8ohms. How do you figure they will sound? i know you said i don't need a sub but i already have a 15" :)
Elsinore Tweeter Distortion Tests

Elsinore Tweeter Distortion Tests

So far three Tweeters have been tried in the Elsinore speakers. It started with Vifa XT25 and became the basis for Elsinore Mk1. There were concerns however as this is a 4 Ohm Tweeter and rated at 91dB. As the Elsinores are very sensitive and the main driver array is 8 Ohm, there will be little padding down of the XT25 tweeter to raise Z. In the final result it gets as low as 3 Ohm.

Then Vifa DX25 was tried. As this is also 4 Ohm but rated at 93.5dB, it was thought this might bring the in-system Z up (more padding), but in reality it was not that much of an improvement.

Sound wise I even felt that it was better than XT25. It doesn't die as much off axis as XT25, it is cheaper and just a little better sonically IMO.

Then it became a serious search for an 8 Ohm tweeter. I realised that the new Peerless HDS was 8 Ohm and also 93dB rated. Like others, I came across Zaph Audio's acclaim and his tests were indicating that it was better than Seas Millenium on the basis of those tests.

Once the HDS was integrated (took a couple of weeks) and just as hoped for, the 8 Ohm system Z was attained. But more than that, this is a superior tweeter sound wise, no doubt about that.

So how do the test?

The following graphs use colours to identify which tweeter, so:

XT25 is RED



Let's start with THD Graphs 1KHz




CONCLUSION: This is a fairly difficult test, but appropriate as the tweeter we are seeking needs to have good bandwidth and the XT25 with low Fs=500Hz you would think would be the winner. NO! The HDS is easily the winner.

Joe R.
Individual Harmonic versus Frequency Graphs







Please note that these are referenced measurements, so in dB terms you can actually calculate the individual harmonic distortion at any frequency in percentage terms. Just use the usual 20Log type calculations.

CONCLUSION: No surprise, the HDS is clearly the winner.

OK. There you have it. I invite any comments on the above. What is quite sure in my mind, the HDS is a class above the other two and the cheaper DX would be my choice over the XT. The overall pattern is consistent through all the tests and the ranking obvious.

Joe R.
Joined 2005
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Thanks for publishing your findings Joe. They correlate very well with Zaph's, which is always reassuring.

The 810921 sure looks like a winner, across the board.

Although the low end of the XT25 leaves a little to be desired, above 3Khz it looks cleaner than the DX25. The limited dispersion can be an advantage, or disadvantage, depending on your design goals.

Have you run similar comparisons with the Peerless midwoofers? eg. HDS vs Nomex, vs PPB?


PS. The new Altronics catalogue is showing a tasty new 1" dome tweeter waveguide...