Why don't you do the mix yourself? This is diyAudio!? You could even do different mixing ratios. Golden ratio anyone? 😉
I’m in Canada and just went to a mattress/upholstery supplier and bought Dacron that was a similar thickness/weight to what Joe posted on his website. I’m in Canada.
Ha ha, I think doable for poly-fill to some extent, but not so easy to make "bonded" type DIY mixed batting. 😉
"Golden Ratio" - LOL.
Joe & Co.:
I'm in the U.S. and built four pairs of Elsinores with friends. We couldn't find the 75mm (3") thick wool/dacron material that Joe had suggested, so we used a combination of Ultratouch denim insulation (50mm / 2" thick) sourced from Home Depot, and bonded Dacron (25mm / 1" thick) sourced from Meniscus Audio. Inexpensive and the two are doing an excellent job.
Regards,
Scott
P.S.: Joe, we're waiting anxiously for news of the Hamlets. There's a lot of pent-up demand for a bookshelf-sized speaker with the Rasmussen touch!
I haven’t built Elsinores but would use a mix of ultratouch felt for walls near the driver and acoustastuff for any volume fill.
Wool is a lot of work and you really need a spare washing machine and a carder to prep it.
I can get as much raw sheep's wool as i want from the local old sheep’s home.
dave
Wool is a lot of work and you really need a spare washing machine and a carder to prep it.
I can get as much raw sheep's wool as i want from the local old sheep’s home.
dave
When I run out of the wool-blend I have here, I will likely use the Polymax polyester. It should work. In my soundroom I recently had to get the carpet replaced as it was twenty years old and it was a wool-blend. But you can't get that anymore, so I went for a slightly thicker underlay and only slighter thicker shag carpet... in the end I was very satisfied with the result. Yes, it was all polyester. So there you go.
See attachment below, it comes from this website:
R3.0 Bradford™ Polymax Thermal Ceiling Insulation Batts
It is also used in walls to insulate against sound, like you would in sound booths. I also notice it is made of 80% recycled product, a good thing in my book. It looks highly teased (very thin fibres) and that is the key to its thermal properties. After all, inside the speaker boxes this is designed to turn acoustic energy into heat.
Keep in mind that basically you want most of the rear of the cabinet behind the main brace to be filled, but not with too high density. In front of the main brace, you want to cut it into 25mm approx thickness and line the side and tops internally. It is not brain surgery to figure it out. What it does is make the box look more resistive than what it would normally a lined vented box. Measurements indicate that the internal 75 Litres volume now behaves more like 100-110 Litres, and this is the effect we are aiming at.
But keep sharing what you are using, local knowledge and all that. If you have built Elsinores successfully, then especially share.
Cheers, Joe
See attachment below, it comes from this website:
R3.0 Bradford™ Polymax Thermal Ceiling Insulation Batts
It is also used in walls to insulate against sound, like you would in sound booths. I also notice it is made of 80% recycled product, a good thing in my book. It looks highly teased (very thin fibres) and that is the key to its thermal properties. After all, inside the speaker boxes this is designed to turn acoustic energy into heat.
Keep in mind that basically you want most of the rear of the cabinet behind the main brace to be filled, but not with too high density. In front of the main brace, you want to cut it into 25mm approx thickness and line the side and tops internally. It is not brain surgery to figure it out. What it does is make the box look more resistive than what it would normally a lined vented box. Measurements indicate that the internal 75 Litres volume now behaves more like 100-110 Litres, and this is the effect we are aiming at.
But keep sharing what you are using, local knowledge and all that. If you have built Elsinores successfully, then especially share.
Cheers, Joe
Attachments
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Polymax availability
Hi Joe,
You can buy Bradford Polymax (Product Code 126362) as a special order through Bunnings Warehouse too. It works out slightly cheaper than through the insulation supplier you mention.
Cheers
Hi Joe,
You can buy Bradford Polymax (Product Code 126362) as a special order through Bunnings Warehouse too. It works out slightly cheaper than through the insulation supplier you mention.
Cheers
Good to know. I will keep that in mind too.
Here is the PDF file:
https://www.bradfordinsulation.com.au/-/media/bradford/files/polymax-thermal-datasheet.pdf
Note the part that says: "Ingredients: Organic, long chain synthetic polymer"
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North American source for Acoustastuff
Dampers: Acousta-Stuff by the pound
And any Canadians want some i have way more than i’ll ever use. It is already across the border.
dave
Dampers: Acousta-Stuff by the pound
And any Canadians want some i have way more than i’ll ever use. It is already across the border.
dave
Thanks Dave. Pretty sure that this is long fibre polymer. The world is being taken over by polymers. 😕
http://www.madisound.com/pdf/acousta-stuff.pdf
Interesting that they say on the webpage "Recommended for sealed speaker enclosures." This is because the convention is to fill sealed boxes and line vented boxes. The idea of making the vented box more resistive (with fill) is only gradually catching on with designers. I know one famous French designer who does this as well and it takes on the characteristics of a transmission line (TL) rather than a classic reflex box. The Elsinores sound more like TL than most other speakers. This kind of bass seems to breathe into the room in a very satisfying way. Playing around with positioning does of course effect this.
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My miniOnkens make the box more resistive thru the use of a long high ratio vent.
Same idea, different approach.
dave
Indeed, that damping can be achieved with tuning, but what benefits can you expect in say, a normal vented box?
I believe that the idea for a vented box is that lining only will not interfere with the port. Lining is safe to do and adding fill is not. So that rule has stuck.
But you can still design with fill and get the result you want (a better one in my book), just make sure the fill is not close to the vent. Any obstruction there will cause the vent to become aperiodic - it will behave like a sealed box with a leaky vent. Some designers actually go for that. But the Elsinores slows the velocity down before it gets to the vent, which must not have any obstruction near it. Then it works really well.
But you can still design with fill and get the result you want (a better one in my book), just make sure the fill is not close to the vent. Any obstruction there will cause the vent to become aperiodic - it will behave like a sealed box with a leaky vent. Some designers actually go for that. But the Elsinores slows the velocity down before it gets to the vent, which must not have any obstruction near it. Then it works really well.
I was only saying this recently - Design your own speaker from scratch discussion thread
The Elsinores will not behave like a transmission line. The distributed woofers make sure of that.
I didn't say it was a TL, but I take your point. I have built my share of TLs, but now don't consider their complexity worth it. I found another way - and I know that there are a few other designers out there who are doing the same.
I remember a discussion many years ago about what is the difference between a TL that has a reflex action at the port end and that of a vented box. The difference is difficult to define and I took a neutral position. All working TLs have vents. Some are lined only and I consider them to be more vented than TL. Then you have filled TL, but they still have a port. The fill slows down the velocity by a significant degree before it gets to the port. These seems to have less bass, but they are better in many other ways.
What I am saying is that slowing down the velocity inside a vented box before it gets to the port, that the difference becomes even less defined. Where the driver is located, that is of less importance. I have now done resistive vented designs for at least 20 years and the result has always been welcomed - how can you get out that kind of bass with a speaker the size of a mini-monitor like LS3/5A? Well, I did.
It works and I have some ideas as to why. That's all. The vent seems to couple to the air in a better way, in the same way that a filled TL does.
If anybody wants to try it: Calculate the box as if you were going to used it lined, but use fill instead, not too dense. Keep fill away from the port opening internally. Figure out what the port frequency will be (the Fb Helmholtz frequency) as if lined. Now mount the driver and see that the Fb has dropped in frequency. Listen to it and if you want, experiment with different vent lengths, but chances are, you won't need to, in my experience. Does this sound different from the usual vented design? You bet!
Cheers, Joe
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The damping changes the tuning, as we've been saying, and that's to be expected. It can/should be compensated by tuning the port.
You wouldn't be conflating the action of a mass-loaded transmission line? Velocity as you describe it here is a modal consideration. Consider the point at which the Elsinores are acoustically small...
Maybe another thread would be the place to discuss this?
You wouldn't be conflating the action of a mass-loaded transmission line? Velocity as you describe it here is a modal consideration. Consider the point at which the Elsinores are acoustically small...
Now consider what happens at modal frequencies, the story is very different and the distribution of the woofers has a significant effect.
Maybe another thread would be the place to discuss this?
Not now. Got enough balls in the air right now. I think we may be talking about different things, so not conflating anything, at least not in my mind.
BTW, in a sealed box the tuning is a product of box volume and the driver. If you have any reflex action, as in a vented box (the saddle frequency) is only dependant on the box and independent of the driver. Mind, only the frequency, everything else can be different, including damping. But many TLs do have that saddle.
It's been twenty years plus and I know that there have been developments and I am not up on them, to be honest. I do remember one area that a good TL had a nice quality, that at moderate volume they still seemed to fill the room with bass. I can now do that without all that complexity. So I have left TLs behind.
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BTW, in a sealed box the tuning is a product of box volume and the driver. If you have any reflex action, as in a vented box (the saddle frequency) is only dependant on the box and independent of the driver. Mind, only the frequency, everything else can be different, including damping. But many TLs do have that saddle.
It's been twenty years plus and I know that there have been developments and I am not up on them, to be honest. I do remember one area that a good TL had a nice quality, that at moderate volume they still seemed to fill the room with bass. I can now do that without all that complexity. So I have left TLs behind.
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