I really, really shouldn't stir up this old pot of bickering - but I just got a shock: the bloke who does all the speaker associated things in connection with WES Components in Sydney, THE place to get every last thing you could think of with regard to sensible DIY electronics - has hopped into bed with the devil - Bybee by name,.
Ribbon Speaker Kits
Obviously he reckons there's something going on - he's got nothing to gain by associating with "flooby dust" ...
That "Majestic" from 2014 looks right up your alley, in fact are you a ghost writer for Silicon Chip?
This mag is a real quaint throwback.http://www.siliconchip.com.au/Issue/2014/June
Last edited:
I have a local source for MDF up to 1 1/2" and 5' X 12' sheets, I don't speaker projects but just curious is 1 1/2" thickness useful or just overkill?
That "Majestic" from 2014 looks right up your alley, in fact are you a ghost writer for Silicon Chip?
Boggle. 1972 called and wants its DIY project back.
I'm no expert, just limited experience regaular guy. In my experience, regarding the baffle, which has to deal with like 90% of the generated mechanical energy, I finally used glued together 3 MDF boards, each 22 mm (app.0.87 inches) thick. This was our third go, started out with one, then tried 2 and finally settled on 3. Key reason - the thicker it got, the cleaner my bass lines worked. And of course, the heavier the whole box, its actual weight now (with everything inside is 28.2 kilos or app. 62 lbs for a nominally "bookshelf" format speaker, i.e. needs dedicated stands to be on the floor).
The other reason is that such thickness allows you to sculpture the sides and decrease refraction as in, for example, Avalon speakers.
Attachments
In my enclosure, i used 2 boards glued together. One MDF, one of less density. and a foil of lead covered by Blakson paint inside. it is a big mistake. It is very mat, but so heavy: i had troubles at each of my relocation.
It is way better, on my opinion, to put many cleats between walls inside the enclosure, to dump the walls. Or, and, to think at creating a vacuum between the walls that we can garnish with dry sand...
That is the way i should consider my next horns: two walls in resin filled with sand ? Massive wood is perfect, and good looking, but sooo expensive !
Makes me wonder whether the add should appeal to a grandfather or to a pedofile. (which can be one and the same)
Come sit on daddy's big and powerful Majestic, deary.
Scott,
I have built a bunch of cabinets with double layers of 1" mdf glued and screwed together for front baffles. As dvv says it does help damp the front panel and can be easily sculpted and when you consider all the cutouts of a multi-driver enclosure it does help to stiffen the front face. It does get real heavy fast though and as Eperado has just pointed out for most things I would use internal ribbing or complete panels with cutouts to attach all the walls together to stiffen the walls and even the face panel. Of course you end up cutting parts of those reinforcements out so the air can still move inside but if you look at some of the older ideas of honeycombed internal spaces that I think either B&W or B&O did years ago that would be the extreme. Plywood wood be stiffer by nature but the only plywood worth using is the imported Baltic Birch and then you still can stack layers to make it stiffer. As Christophe noted constrained layers with multiple density materials and even damping layers of some elastomer or fulled with sand has also worked for many who don't mind needing three people to move them. I have a friend who went as far as to use tension and compression rods in large PA enclosures to stiffen the enclosures. Some people won't work with mdf as the resin used to hold it all together is often a formaldehyde based resin and they think the dust is to toxic, I just wear a mask.
I have built a bunch of cabinets with double layers of 1" mdf glued and screwed together for front baffles. As dvv says it does help damp the front panel and can be easily sculpted and when you consider all the cutouts of a multi-driver enclosure it does help to stiffen the front face. It does get real heavy fast though and as Eperado has just pointed out for most things I would use internal ribbing or complete panels with cutouts to attach all the walls together to stiffen the walls and even the face panel. Of course you end up cutting parts of those reinforcements out so the air can still move inside but if you look at some of the older ideas of honeycombed internal spaces that I think either B&W or B&O did years ago that would be the extreme. Plywood wood be stiffer by nature but the only plywood worth using is the imported Baltic Birch and then you still can stack layers to make it stiffer. As Christophe noted constrained layers with multiple density materials and even damping layers of some elastomer or fulled with sand has also worked for many who don't mind needing three people to move them. I have a friend who went as far as to use tension and compression rods in large PA enclosures to stiffen the enclosures. Some people won't work with mdf as the resin used to hold it all together is often a formaldehyde based resin and they think the dust is to toxic, I just wear a mask.
I'm afraid the Lewis Carroll syndrome runs deep in things like Brit SciFi for instance.
Sy,
As you noticed the resonance up high in the Focal inverted dome tweeters is there in all the models, it just moves around in frequency. They even went as far as to add a little phasing plug hanging over the center to try and correct that. If you look in my posts about that driver you will see that I did mention the cavity that you have created in front of the dome, a very bad idea and more than likely the culprit in that resonance along with the use of Ti for the domes on the latest versions. I have old parts from the very first ones with Kevlar inverted domes and even those have this typical high end sound of nastys on top. If you ever take one apart you will see the way they are driving the dome from the back. the attachment point is at about 2/3 the diameter of the dome, supposed to be at the first nodal point to stop the cone from breaking up. I don't think that works in reality and if you just look at the force diagram and think about what they have done it really leaves the outer section of the dome kind of hanging in air like a Whizzer, that may also be contributing to this problem on the high end. I didn't have anything like a Kipple laser setup to look at the actual dome and see what was actually happening but the measurements surely don't lie. Focal does things like this throughout their line of devices, silly things for marketing that are supposed to be improvements but I think are actually some of the reasons I don't like the sound of their devices.
As you noticed the resonance up high in the Focal inverted dome tweeters is there in all the models, it just moves around in frequency. They even went as far as to add a little phasing plug hanging over the center to try and correct that. If you look in my posts about that driver you will see that I did mention the cavity that you have created in front of the dome, a very bad idea and more than likely the culprit in that resonance along with the use of Ti for the domes on the latest versions. I have old parts from the very first ones with Kevlar inverted domes and even those have this typical high end sound of nastys on top. If you ever take one apart you will see the way they are driving the dome from the back. the attachment point is at about 2/3 the diameter of the dome, supposed to be at the first nodal point to stop the cone from breaking up. I don't think that works in reality and if you just look at the force diagram and think about what they have done it really leaves the outer section of the dome kind of hanging in air like a Whizzer, that may also be contributing to this problem on the high end. I didn't have anything like a Kipple laser setup to look at the actual dome and see what was actually happening but the measurements surely don't lie. Focal does things like this throughout their line of devices, silly things for marketing that are supposed to be improvements but I think are actually some of the reasons I don't like the sound of their devices.
Christophe,
The comment about using two skins and filled with a secondary material was the basis of my early work on horns along with the shape of course and this started as two skins of fiberglass with a urethane low density filled center. It was a pain to accomplish this as the foam expansions had to be controlled so the two skins had to be held in tooling to hold their shape while the foam expanded, a real pita. This is what led me to using high density urethane foam for my horn designs, this creates two solid skins with a foamed center that is filled with gas in each cell, it is as close to wood as I have been able to create but doesn't have the natural strength of an organic material like wood does with the fibrous reinforcement. That was part of my original patent back in the mid 1980's. Now I don't do the patent thing as I would rather just keep what I am doing as a trade secret and not divulge why I am doing what I do. Still using and working with urethane foams though, I haven't found a better solution than that for real production of parts.
The comment about using two skins and filled with a secondary material was the basis of my early work on horns along with the shape of course and this started as two skins of fiberglass with a urethane low density filled center. It was a pain to accomplish this as the foam expansions had to be controlled so the two skins had to be held in tooling to hold their shape while the foam expanded, a real pita. This is what led me to using high density urethane foam for my horn designs, this creates two solid skins with a foamed center that is filled with gas in each cell, it is as close to wood as I have been able to create but doesn't have the natural strength of an organic material like wood does with the fibrous reinforcement. That was part of my original patent back in the mid 1980's. Now I don't do the patent thing as I would rather just keep what I am doing as a trade secret and not divulge why I am doing what I do. Still using and working with urethane foams though, I haven't found a better solution than that for real production of parts.
I remember too those long pages of Carter Brown* where his detective Danny Boyd describes in details his hifi system playing some Sinatra LP, while the blonde on the couch...
At this end, did this quest for hifi just an attempt to get the best girl trap ?
Is John Curl a dangerous sexual maniac and Jack Bybee the keeper of his favorite swingers club?
That should explain his quest for extended range tweeters. Teens ears, usually, can hear very high frequencies....
* Looking at his biography, i found that he worked two years as a sound engineer for the British Gaumont in his young years.
Last edited:
My bad, I grew up with Robot Archie by Ted Cowan.
(I blame him for ending up with bar room fractures by hitting aluminum street lamps. As the saying here goes, only a donkey never hits the same lamp twice)
[J.C. Mode on]
In fact, I realize that Carter Brown has had a great influence on my life.
I read his novels during masses, having replaced the missal pages by his owns.
That is probably what decided-me to chose the career of hifi designer instead of the one of the French republic president.
I turned quickly towards that of a sound engineer, when i saw in movies all these groupies under the mixing desks.
[/J.C. Mode off]
Who could really care about high fidelity?
In fact, I realize that Carter Brown has had a great influence on my life.
I read his novels during masses, having replaced the missal pages by his owns.
That is probably what decided-me to chose the career of hifi designer instead of the one of the French republic president.
I turned quickly towards that of a sound engineer, when i saw in movies all these groupies under the mixing desks.
[/J.C. Mode off]
Who could really care about high fidelity?
Last edited:
Do they care ?
The only technically correct way i know for high SPL is highly directive horns, that you can multiply to extend the covered volume. creating a virtual emissive source point. Even there, you will have accident if you stay right in the middle of the angle of two adjacent horns at some frequencies.
http://www.electrovoice.com/sitefiles/product_images/XLC_hang_Pantages.png
Reason why so many companies tried to build coaxial speakers to null the distances between the sources at the crossover point.
Last edited:
dvv,
Do a little research on line arrays and you will quickly come to understand some of the problems of using two tweeters operating at a distance from each other. Comb filters are subtractive and additive in nature depending on distance and frequency. I would never consider two dome tweeter on the same enclosures a good idea. If you can not reach the spl level you desire it is time to look for a different tweeter or a different type of device such as a compression driver that will have little problem making massive spl level. The other solution but it brings its own problems along with the increased output is a waveguide and dome tweeter, problem is they increase gain in the lower frequencies and rapidly drop in output as frequency rises so require completely different crossover networks and attenuation circuits.
Do a little research on line arrays and you will quickly come to understand some of the problems of using two tweeters operating at a distance from each other. Comb filters are subtractive and additive in nature depending on distance and frequency. I would never consider two dome tweeter on the same enclosures a good idea. If you can not reach the spl level you desire it is time to look for a different tweeter or a different type of device such as a compression driver that will have little problem making massive spl level. The other solution but it brings its own problems along with the increased output is a waveguide and dome tweeter, problem is they increase gain in the lower frequencies and rapidly drop in output as frequency rises so require completely different crossover networks and attenuation circuits.
- Status
- Not open for further replies.