The "Elsinore Project" Thread

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planet10

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
Paid Member
...if has a 'filled' part that slows down the internal sound propagation...
Click to expand...

Joe,

Please do not propogate that myth. Bradbury has been shown wrong, the damping does not slow the speed of sound down.

It is true that the damping does increase the apparent volume of the box.Maximum amount is usually considered to be 20-30%.

somewhat more like a transmission line
Click to expand...

A 1/2 wavelength transmission line since the box is sealed. This is the case with alll tall-skinny boxws.

dave
 
Joe Rasmussen

Joe Rasmussen

Member
Joined 2003
customanalogue.com
planet10 said:
Joe,

Please do not propogate that myth. Bradbury...
Click to expand...

I could have worded things a lot better. But I wasn't really talking about damping, I was talking about the tuning of a vented box.

planet10 said:
It is true that the damping does increase the apparent volume of the box.Maximum amount is usually considered to be 20-30%.
Click to expand...

This is exactly what I meant, but again I was talking about the tuning and not about the damping. For example, I recall a test I did many years ago with a 10 Litre box that was tuned to 55Hz when lined and it dropped by quite a few Hertz (think it was more that 5 Hertz) when filled. That tells me that the apparent volume had increased because the same dimensions of the port has not changed, so an increase in apparent volume explains the lower tuning.

So there is a reduction in velocity (I should not have used propagation, but I just couldn't remember the word velocity at that moment) inside the box, this explains the apparent increase in volume because the volume will look larger to the driver. The fill has a resistive or lossy quality, this is also what a good TL will take advantage of.

That reminds me, and I don't miss taking an opportunity to point this out to even serious speaker designers, but the box tuning frequency of a vented box is independent of the driver, but in a sealed box the driver influences the sealed box frequency. So with a vented box, change the driver and the saddle frequency will not change, but of course the damping will.

Back to the choices made in the Elsinores, the idea is that this is a more resistive vented box than what you get in a conventional lined box. When you do this, you get that apparent increase in volume, makes the port dimensions less problematic (the port can become larger in diameter for the same length - a good thing) and more. But the bass also sounds better, each note better defined and delineated, the kind of sound that I like from a TL, except it is not a TL.

So I was not into any myth, just my own experiences.

Cheers, Joe
 
R

Ranchu32

Member
Joined 2013
I’m thinking about building the Elsinore’s and already have the Peerless tweeters and 4x SB17NRX35-8 from another build.

The woofers are now EOL and no longer available from any of the local distributors, but the recommended replacement, the SB17MFC35-8, are.

My question: is it advisable to mix ‘n match the NRX and MFC drivers, and if so, what’s the best way to go about it.

I can go out and buy 8x new woofers but I thought I’d ask first since the MFC’s I’ve got will be surplus to my needs if I go ahead with this build and can’t use them.
 
R

Ranchu32

Member
Joined 2013
Thanks zman, I missed that post from Joe, which confirms what I already suspected.

A friend and speaker builder has suggested I use the 2x Peerless and 4x SB17NRX to build a pair of MTM Elsinore's in smaller cabinets. They would sit on top of a pair of 12" woofers in separate (probably sealed enclosures) which would provide the bass reinforcement. Bass drivers would be powered from separate amps.

I don't want to take this thread OT but if anyone has tried something similar please send me a PM.
 
D

dmcgown

Member
Joined 2002
Getting Started...

Just received a package from Madisound yesterday with (8) SB17MFC35-8 woofers and (2) D2608/9130 dome tweeters, so now committed and starting on the project.

Still working on the planning on my cabinets. I am finding it easier to find 18mm Baltic Birch plywood locally than 1" MDF. I did a quick beam calc comparing the two materials, taking into account that Young's Modulus for 18 mm BB is around 10 GPa with the grain of the outer veneer, and 7.5 GPa across the grain (this is from a document from the Finnish Plywood Industry). MDF has a Young's modulus of around 3.6 GPa. Anyway, the calculated stiffness for a 1 meter length with the same load distribution is virtually the same between two materials (assuming the BB outer veneer grain runs longitudinally. (i.e. 18mm BB Ply = 1" MDF). Understand that MDF has better self damping, but I think a few mm of bitumen pads should help with that.

Excited to get started, I was pretty tempted by some of Troels Gravensen's designs, but I think that a decade+ long evolutionary design and alot of builder success stories outweigh designs quickly developed (although by all appearances and builder success stories, very nice designs as well).

David
 
Z

zman01

Member
Joined 2011
David,

Have you recalculated the cabinet dimensions for 18mm thickness material? My understanding is that the baffle width of has to be maintained. So if you want to maintain 280mm external cabinet width with 18mm ply, you will end up having 7+7=14mm extra internal width as each ply is 7mm thinner than the default 25mm. So internal volume will increase.

Also some of the internal braces will become thinner with 18mm ply, resulting in a little more cabinet volume.

Joe, any comments?
 
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D

dmcgown

Member
Joined 2002
I plan on maintaining external dimensions, and taking up the internal volume increase via bitumen pads. The only case is the interior brace, which may cause me to slightly reduce the cabinet depth, though the fact that the area/volume of the brace is less due to the cutouts, there should not be much overall reduction necessary.
 
OZmOZis

OZmOZis

Member
Joined 2015
9

90TSIAWD

Member
Joined 2014
dmcgown said:
Just received a package from Madisound yesterday with (8) SB17MFC35-8 woofers and (2) D2608/9130 dome tweeters, so now committed and starting on the project.

Still working on the planning on my cabinets. I am finding it easier to find 18mm Baltic Birch plywood locally than 1" MDF. I did a quick beam calc comparing the two materials, taking into account that Young's Modulus for 18 mm BB is around 10 GPa with the grain of the outer veneer, and 7.5 GPa across the grain (this is from a document from the Finnish Plywood Industry). MDF has a Young's modulus of around 3.6 GPa. Anyway, the calculated stiffness for a 1 meter length with the same load distribution is virtually the same between two materials (assuming the BB outer veneer grain runs longitudinally. (i.e. 18mm BB Ply = 1" MDF). Understand that MDF has better self damping, but I think a few mm of bitumen pads should help with that.

Excited to get started, I was pretty tempted by some of Troels Gravensen's designs, but I think that a decade+ long evolutionary design and alot of builder success stories outweigh designs quickly developed (although by all appearances and builder success stories, very nice designs as well).

David
Click to expand...

I did a Search and found two potential places that carry 1" MDF around Baltimore. If i can get around to giving them a call ill let you know.
 
Joe Rasmussen

Joe Rasmussen

Member
Joined 2003
customanalogue.com
Ranchu32 said:
Would be great to find out if the uncoated version is a drop in replacement.
Click to expand...

It should be fine, even when the coating is applied it is very light. So I would certainly use it if available. I do think they only made a limited number of these.

I should point out that there is an aspect of the Elsinore design that makes this possible when the three possible drivers can be used, that they have share identical 'motors' and chassis. The extremely low inductance is shared by those three drivers is especially a critical factor. This makes them very predictable in the critical area. So not all is lost with the original NRXC driver becoming increasingly unavailable. This is caused by the fact that the newer NRX2C driver has a much heavier cone, this lower sensitivity/efficiency and also causes an increase the Q of the driver, even though it too used the same motor system.

So we need not yet say that we cannot continue the EL6 well into the future.

.
 
P

pguerin

Member
Joined 2010
dmcgown said:
Just received a package from Madisound yesterday with (8) SB17MFC35-8 woofers and (2) D2608/9130 dome tweeters, so now committed and starting on the project.

Still working on the planning on my cabinets. I am finding it easier to find 18mm Baltic Birch plywood locally than 1" MDF. I did a quick beam calc comparing the two materials, taking into account that Young's Modulus for 18 mm BB is around 10 GPa with the grain of the outer veneer, and 7.5 GPa across the grain (this is from a document from the Finnish Plywood Industry). MDF has a Young's modulus of around 3.6 GPa. Anyway, the calculated stiffness for a 1 meter length with the same load distribution is virtually the same between two materials (assuming the BB outer veneer grain runs longitudinally. (i.e. 18mm BB Ply = 1" MDF). Understand that MDF has better self damping, but I think a few mm of bitumen pads should help with that.

Excited to get started, I was pretty tempted by some of Troels Gravensen's designs, but I think that a decade+ long evolutionary design and alot of builder success stories outweigh designs quickly developed (although by all appearances and builder success stories, very nice designs as well).

David
Click to expand...


Hi David,


FYI I've build my Elsinore with 19 mm MDF and bitumen pads.
I've reduced depth of the boxes from 380 mm to 360 mm to keep the same internal volume.


BR, Pascal
 

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