Yes if you consider crossover slope like a linkiwtz crossover given the best radiation pattern...
For @Joe Rasmussen a photo of a typical French village with the church, cows in the pasture in the background of the photo. The location in the area call "haut bugey".
We all need to sort out what is broke and requires fixing.
If it ain’t broke don’t fix it.
First thing to note about the SB17 POLY driver is the low X Max.
A frequency sweep shows increasing Harmonic Distortion at lowering frequencies.
Multi-tone Tests show interaction between low frequencies and mid-frequencies causing Inter-Modulation Distortion. To my ears this is the worst.
The “Fix” for excursion caused distortions is turning down the Watts and / or using a high pass filter to limit the voice coil excursion.
There are other issues at the crossover frequency between Mid-Range to tweeter. Also there are preferences.
Some people choose to focus on selecting a crossover frequency maximizing the smoothness of Directivity.
Others have a favorite tweeter with a cone shaped horn / waveguide that they are attached to.
Added note:
I do not care all that much about directivity while I am sitting near the speakers on my bench.
Thanks DT
I agree you are in control of crossover induced lobing. For a single driver though it won't suppress breakup, and the type of filter doesn't change that.
Shure you can do that.
It will also cause comb filtering with off axis nulls and dead spots.
Thanks DT
Indeed. That is the point I was making when Directivity was brought up.
[We must not confuse Directivity in a single driver and Directivity in a multi-driver system situation.]
Hence I said that LR4 (and the L stands for Linkwitz) multi-driver system, would sort out the Directivity as they tend to cross them over @2KHz and even lower. From an acoustic view, the lower the crossover frequency, then for several reasons acoustic wise works. Being -24dB one octave above also sorts out the 'horn effect' that is predominantly on axis, is now well suppressed. In SoundEasy LR4 crossovers around 2KHz are not that hard to do. They are also extremely common these days.
To me, LR4 do acoustic side of things like Directivity and 'horn effect' very well. But I put the emphasis on the electrical.
I even think the 1st order fan boys is getting something wrong (now all sides will hate me, lol). The classic step response proposed by them, and making all drivers in-phase (electrically) and essentially Butterworth crossovers. They sum at -3dB (it should be -6dB) and this means that the tweeter's off axis response is now only half as helpful in filling off axis response and overall not so good. The tweeter's power handling is also compromised.
What I am basically saying is that the 1st order guys points to this response as the key to better sound of 1st order (and I agree that 1st order has the potential to sound better:
This acoustic step response is claimed to be the reason for better sound.
I disagree. I think the real reason why it sounds better is because 1st order crossovers suppress the Ei impedance modulations of the main driver and less due to the tweeter which I consider compromised by Butterworth.
But I use 1st order and sum -6dB, use a waveguide that means a massively smaller value on the tweeter as well as LC null on its Fs. These are largely electrical solutions. Then there is one more electrical solution: EQ the sum current flat with frequency. How that suppresses those Ei impedance modulations is less obvious, but it does because where the system impedance is highest, there is more current going through the LCR used to EQ current. You have to analyse this one to figure it out and why it works. But then again, the im-practical solution of current-drive has it major benefits in stopping Ei impedance modulations
So I am basically claiming that you get the same benefits of current-drive, but you get it with voltage-drive as well. That's great news because current-drive is just not the way to go. Sorry Esa, but here we are not on the same page. And finally, you get an amplifier that could not be friendlier to tube amps, so all bases are covered.
Back briefly to Directivity, if all is understand by the above, you will see very clearly that I have not ignored it. Both LR4 and my crossover, both sum at -6dB and that gives them both a plus in Directivity. But I would admit that LR4 methodologies will be better. One good, the other possibly better. Electrically, one is very much better.
So I am even drawing a connection between the claimed better sound for 1st order fan boys and the current-drive fan boys. The potential better sound in both are actually connected to the impedance stability of the drivers.
Not a single driver. But in a system? I would say yes.
Oh yes!!!
Paramount!
How low frequencies? Below 100Hz? That is not unexpected. But I am not ignoring.
True. It's a trade-off and one that the designer must decide. Also, 2.5-Way systems helps. Lots of Sd surface area a la Elsinores. The SB17 poly in this configuration works very well indeed. As builders what they think of the bass and that some say they hardly need subs. And they go loud with ease.
Please read my post a few minutes back, I would be interested... Again, there are things that the speaker designer must weigh up. I have developed my design philosophy with much careful thought.
Oh yes, and this has become an increasing dominating issue. I think the topic is important, but if you chase it too hard you may be missing out elsewhere. Directivity is an acoustic issue, I am chasing something more important to me, but not discounting it of course.
Waveguide has seen a big emergence lately. To most it is the potential acoustic properties that appeal. Such as lowering the crossover frequency is likely to make Directivity look good. Longer wavelength I am told, is a good thing. Overcomes beaming of the midrange driver.
But in the Elsinores you see a different approach to using waveguides. I keep the crossover relatively high. I want reduce distortion and hence stay with a higher crossover. This combined by the 'waveguide' gain (5dB typically) at 3KHz means a smaller series value capacitor. And the higher 3KHz itself already means that I am using a lower value. I end up with a capacitor value getting closer to 25% - so 1.8uF versus 6.8uF. Almost four times the reactance between the amplifier terminals and the tweeter terminals.
I don't know how much the above two posts means to you? I can only hope that some of it makes sense. If it is not completely understood, then please remember, it took me a long time to get there myself.
I am fascinated by this trade-off between the electrical and acoustical. I am definitely in a minority camp. But I should be judged by my end designs, you said it yourself, that's what matters!!!
I don't disagree with that.
I may have read that and misunderstood it. I thought initially you said it was about the inductance and I said it was paramount. I now realise you were talking about Xmax as being low in the SB17MFC35-8 driver. In fact it is very average for this class of driver. But the rest of the comments were OK, about the need to control excursion at LF.
Hello,
Using the distortion limited methods in IEC 60268 Xmax is ~ 5.6mm p-p. That is 10%+ distortion at Fs.
It is about the need to control excursion at LF.
Thanks DT
The current standard defines "the voice-coil peak displacement at which the "linearity" of the motor deviates by 10%. Linearity may be measured by percent distortion of the input current or by percent deviation of displacement versus input current. Manufacturer shall state method used. The measurement shall be made in free air at fS."
https://www.klippel.de/fileadmin/_migrated/content_uploads/AN_04_Peak_Displacement_Xmax.pdf
How does that figure compare with other competing 6 inch midwoofers? (Fairly typical would be my guess, if we're not spending Purifi money.)
Also, I've been modelling the Elsinore in Basta. (Not perfect, I know, but still interesting.) My sim suggests that at 105 dB at 1m, you'll only exceed 5.6mm p-p excursion below about 33 Hz. Not too bad?
Also, I've been modelling the Elsinore in Basta. (Not perfect, I know, but still interesting.) My sim suggests that at 105 dB at 1m, you'll only exceed 5.6mm p-p excursion below about 33 Hz. Not too bad?
I was in Geneva in 2014 and not too far from there to the west. We went south into Italy via Little Saint Bernard's Pass (my favourite for being where Hannibal crossed). Just the two of us in an Audi Quattro sportwagon, a great driving car and especially in the mountains.
Right, and since this thread is about Elsinores and its users/constructors, they can attest to surprisingly low excursions in real life. I came across an *interview with a French loudspeaker designer who said that his speakers had a port, but it was not a reflex design as the port was primarily designed to reduce cone excursions. From what he said and a bit of reading between the lines, it was clear that he was doing what I was doing. Use a lot of fill, try 60% or a bit more, then tune a little lower than you would otherwise and then check what the design does. This approach also seems to help keep the port more quiet. If you have an idea why this is so, then please tell, It seems to relate to the fact that the fill makes the alignment more resistive and is this a less complicated way to get the sound of a transmission line with a lot less complications? It sounds like a good transmission line. And get a good amp to explore it.
Yes indeed, it is linked to distortion. Before that standard I heard that 'effective' was Xmax plus 15% (x2), was nominally said to add 1% distortion. It is a long time ago, so memory is a little foggy, but it was something like that.
*PS: The mag was Stereophile for sure, but I forget the brand.
Hello,
The Elsinores have changed over the years, they have had several different drivers.
Over the iterations of the Elsinores this thread is as much about speaker design as speaker building.
In the case of Elsinores the speaker has multiple drivers to reduce the cone excursion. It is not just cone excursion, it is also about net force applied to the total area of the cone(s).
The driver motor(s) apply Force to the cone(s). The air pressure in the enclosure apply force to back of the the cone(s) in opposition to the force applied by the driver motor(s). We think of this as back pressure, similar to the concept of back EMF. The force applied to the cone(s) is the sum of the force applied by the driver motor(s) and the back pressure internal to the speaker enclosure.
A resistive port is instrumental in reducing the enclosure back pressure and flattening the impedance curve.
We agree that generous stuffing and a resistive port do good things.
Thanks DT
Added Notes:
As sound travels the length of a stuffed "transmission line" it takes time and the sound level is attenuated. The stuffing is resistive and slows the speed of transmission.
We often make pressure microphone measurements inside enclosures.
Yes, fairly well summed up. Thank you for that. But the first boxes all were updatable as we went along.
I am kind of divided about that.
This thread was firstly for those who just wants to build. But when it comes to design and theory, but behind the scenes I am told that even if they don't understand it all, they do understand some of it and also that there is something behind it beyond just stuffing a box with drivers. So there are theories and design philosophies at work, the rationale behind it all. But I have tried to keep the discussion centered around Elsinores.
That has always been at the centre, and this: Take an 8R driver with 90dB sensitivity @2.83V (1W). Now take two drivers and put them in parallel and you will double the current and thus 2W is nominally drawn. You have gone from 354mA up to 708mA. Measure the dB-SPL at 1m and you have jumped from 90dB to 96dB. Since you can account for 3dB, that means you have gained 3dB. What it we were to put the two drivers in series? Now we will draw half the power and the current halved to 177mA. That is now 0.5W. Now measure our dB-SPL and we find it to be 90db-SPL. We have not gained dB-SPL, but we have achieved at half power and thus again we have 3dB because it is not 87db-SPL.
Now comes the key, what if we were to use four drivers in series-parallel? Now we would still be at 1W and now our dB-SPL would be 96dB-SPL and we have gained a genuine +6dB-SPL.
Wind the array back to the original 90dB-SPL, we now only need 1/4W to drive it and 62.5mW per driver!
Those are beautiful numbers and that was the initial impetus to design the Elsinores. Yes, low excursion and also cool running voice coils.
Just a correction, I described the alignment to be resistive, not the port. Making the port resistive would make it aperiodic and that is not the aim here. The fill must be kept away from the port.
The Elsinores before and after current EQ:
[Eight components are required, two LCRs and an RC Zobel]
To be honest, some time ago I stumbled across something that I know works and those who have ended up with other designs of mine (not DIY) have pretty universally praised the bass quality. Use almost as much fill as is reasonably possible, not too high density, but avoid fill interfering with the rear of the port and airflow near it. Now tune it lower than you would otherwise? Since you have figured out your volume and got an idea what the tuning will be with a normal lined alignment. But when you have measure it, it will be tuned to a lower frequency because the fill of the box makes the volume look as if it was larger. For example, with the Elsinores, it is actual 75L approx, but now tunes as if it was as much as 100-110L. You may be inclined then to shorten the port to compensate. But I suggest that you try it as it is. You think it will be over-damped, but might sound like it is.
You can of course still play around with the Fb tuning and shorten the port. Season to taste, as they say. When I say resistive alignment then I am not even even sure how technically correct that is. But it is a recipe' and I don't mind others try it and report back. It gives consistent results in my experience.
Can an existing speaker be modified and not change the box tuning element, the port? Yes, this has been tried several times and with good effect.
Agreed. But it also works for reflex type boxes which are a lot easier to make than transmission. And I like what a good transmission line does.
PS: This resistive alignment also has another benefit, the potential port noise seems very well behaved.
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Hello,
The stuffing changes the acoustic properties of the interior of the speaker enclosure. The cognitive view of the stuffed transmission line helps me picture the compression and rarefaction of the wave passing through the length of the duct or volume of the enclosure.
The compression and rarefaction is a adiabatic process of heating and cooling. With the added stuffing fibers there is more mass to heat and cool, It takes time and some energy is lost to heat in the process. There is reduced velocity and amplitude. Damping? It does not matter so much if there is some stuffing material that spills into the port if the size and length of the port is adjusted to taste.
There is a story to tell with measurements and listening.
Thanks DT
For the readers:
https://en.wikipedia.org/wiki/Adiabatic_process
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Yep. And it's the time factor that is the result that matters.
May I add a few things here that certainly supports that view, that slowing down the velocity results in an apparent volume being different from the actual 75L volume, behaving like 100-110L because can be confirmed when looking at the port dimensions. These should be tuning the box closer to 40 Hertz, but it will drop at least 5 Hertz and a bit with fill. I don't have full control over the fill that is used out, but I give instructions where to put it and that causes that drop in frequency. Thankfully there seems to be at least some latitude here, if you get at least that 5 Hertz drop and possibly a bit more, it works quite well. Use fill that is not to dense, I use 270gr per 20L volume (I just measured a sample I have here and that happens to be an exact 20L).
So that increase in apparent volume is the proof that velocity is slowed down and seems to be caused by the process you have stated.
Re damping, that applies more above LF and into the midrange. The large internal volume is also great for the midrange, but even here volume is probably as more if not more important for the midrange. This is based on the experiments that I have seen others do. Before the Elsinores I designed a number of designs where the midrange driver was open baffle. The Elsinores being 2.5-Way means a large internal volume and 100L apparent well damped volume, very little energy is pushed back into the cone, and I see that preventing time smear and more.
Some time ago I played around with this and found that it took very little port interference, especially inside, to collapse the reflex action (Helholm resonator) and the enclosure went aperiodic. That was my experience. The saddle and twin peaks collapsed and replaced with a single peak.
I don't have the full story, I have a partial one. But doing this seems to bring the bass out of the box in a way that reminds me of transmission lines, which I have built going back some time. The added fill should make the alignment sound more damped but it doesn't sound more damped. In fact, it makes the bass sound more powerful, and it is as if the air of the room is being more effectively coupled to the output of the speaker. But this is more observation than science.
Hello Joe and All.
For insomnia there is a bookshelf next to my my night stand, lately there is a copy of the 1954, "Acoustics" text by Leo L. Beranek. There are many references in the text about the acoustics of enclosures filled with air and "a soft lightweight material...". Take a look at page 220 for a discussion of how velocity and the effective volume of the enclosure is changed by the addition of stuffing.
As soft as a pillow it put me to sleep.
For the readers:
https://www.scribd.com/doc/197277181/Acoustics-L-Beranek
Look up 'porous material' in the index.
I do not claim to have the full story either.
I suspect that the effect of the enclosure is reduced by the resistance of the added "soft lightweight" stuffing, allowing the air of the room to effectively couple with the output of the speaker.
The boxy sound of the enclosure is removed.
Thanks DT
I could have written that. Yes, it's like there is a more efficient mechanism for coupling air.
Does anybody have any recommendations for DIY 2way speaker build?
Looking to add some rear speakers for Movie nights. Currently have the mk6 Elsinore and a Hamlet for a centre. Been happy with that setup for movies for the last 10 years.
I thought about making two more hamlets but a bit too bulky for the living room and the wife 😂
Looking to add some rear speakers for Movie nights. Currently have the mk6 Elsinore and a Hamlet for a centre. Been happy with that setup for movies for the last 10 years.
I thought about making two more hamlets but a bit too bulky for the living room and the wife 😂
Sounds like we need a 2-way Elsinore surround speaker.
I think that a SB17 or even the smaller brother SB15 Poly Cone mid-bass paired with the original tweeter would be a good start.
Thanks DT