and the sound ?
Whether Granite or Corian, so long as it does the job it is fine.
It certainly looks good !
Is Corian difficult to cut, etc ... ?
And that new Morel mid-dome,
it has good Specifications, thus what about it do you particually like ?
I've not tried it, but may if I can get time to design a 3-way.
I hope your TL90 upgrade is sounding as good as you hoped,
or at least on the way to ...
Whether Granite or Corian, so long as it does the job it is fine.
It certainly looks good !
Is Corian difficult to cut, etc ... ?
And that new Morel mid-dome,
it has good Specifications, thus what about it do you particually like ?
I've not tried it, but may if I can get time to design a 3-way.
I hope your TL90 upgrade is sounding as good as you hoped,
or at least on the way to ...
Granite (corian) Baffles
Corian is very dense and works easily. I believe the material is well suited for baffle construction..and it comes in a large variety of colors and finishes. I had the "rough" shape cut by a local counter fabricator who has the skills and tools I lack. Simple drum sanding and mounting hole drilling was all I needed to make a very good fit. My one "mistake" was to not have them mirrored...no big deal.
RE: Morel EM1308 Midrange drivers. I bought them on specs and on reputation...and thus far I am not disappointed. The Radford woofer crosses around 500Hz so the extended low freq capability of this dome mid was a good fit. The sound quality is very good. Smooth and effortless. I'm sometimes hearing new musical nuances from my "old" source materials. Please understand that I have been able to listen for less than 2 hours so far...but my initial impressions are very favorable towards the new drivers. They are a keeper.
Corian is very dense and works easily. I believe the material is well suited for baffle construction..and it comes in a large variety of colors and finishes. I had the "rough" shape cut by a local counter fabricator who has the skills and tools I lack. Simple drum sanding and mounting hole drilling was all I needed to make a very good fit. My one "mistake" was to not have them mirrored...no big deal.
RE: Morel EM1308 Midrange drivers. I bought them on specs and on reputation...and thus far I am not disappointed. The Radford woofer crosses around 500Hz so the extended low freq capability of this dome mid was a good fit. The sound quality is very good. Smooth and effortless. I'm sometimes hearing new musical nuances from my "old" source materials. Please understand that I have been able to listen for less than 2 hours so far...but my initial impressions are very favorable towards the new drivers. They are a keeper.
Resonances of corian
I don't have the test equipment that would enable such resonance testing at this point. As my rebuild reaches completion I hope to get some folks from the regional audio society to do a few frequency sweeps of the system and fine tune from there.
(Meanwhile...your tas de bois furniture company looks like it could assemble some fantastic looking speaker cabinets ! Nice Work!)
I don't have the test equipment that would enable such resonance testing at this point. As my rebuild reaches completion I hope to get some folks from the regional audio society to do a few frequency sweeps of the system and fine tune from there.
(Meanwhile...your tas de bois furniture company looks like it could assemble some fantastic looking speaker cabinets ! Nice Work!)
Thanks, Ron.
The reason that I've asked is because I spend last 3 month testing different enclosures and materials for resonances and reflectance qualities. I've tried sandwiching materials and using cement type fillers and powdered glass. Corian wasn't something I had laying around but I will test a piece of Avonite later on.
The reason that I've asked is because I spend last 3 month testing different enclosures and materials for resonances and reflectance qualities. I've tried sandwiching materials and using cement type fillers and powdered glass. Corian wasn't something I had laying around but I will test a piece of Avonite later on.
Resonances & Materials
I am hardly an expert...but I read somewhere in these threads that someone built a transmission line enclosure from 2 inch thick concrete. The box still had vibrations. Looking for the perfect non-resonant / non-reflective material reminds me the old saying about physics.
The study of physics is the study of mass elephants on frictionless surfaces.
GOOD LUCK ! Happy Listening.
PS: TIP OF THE DAY : Go to http://www.soundkeeperrecordings.com/
Buy yourself a copy of " LIFT" You won't be disappointed.
I am hardly an expert...but I read somewhere in these threads that someone built a transmission line enclosure from 2 inch thick concrete. The box still had vibrations. Looking for the perfect non-resonant / non-reflective material reminds me the old saying about physics.
The study of physics is the study of mass elephants on frictionless surfaces.
GOOD LUCK ! Happy Listening.
PS: TIP OF THE DAY : Go to http://www.soundkeeperrecordings.com/
Buy yourself a copy of " LIFT" You won't be disappointed.
Mid-range Cross-over
500 Hz is too low to cross to the Morel EL 1308 !
I am wondering if your short period listening has been only at fairly low Volume levels ?
Other than with some extraordinary cross-over circuit, there will be quite noticeable distortion of the lower frequencies sent to the Morel if it is driven even moderately hard, let alone to high volume level,
or are you listening in a very small room where sound seems loud with low drive levels ?
As well as distortion, there is likelihood the 1308 will be damaged if it is driven hard in the octave below 500Hz.
Have a look at the Specifications/Data sheet for the 1308.
See the large peak in the Impedance Plot centering on its Fs of 320Hz, and the Impedance does not drop to magnitude able to accept a standard x-over till above 800Hz.
Basically what happens is that the electrical interaction between the components in the x-over network and the higher than design spec. Impedance occuring so close to the x-over frequency cause the driver to receive significantly greater signal than would be the case if flat impedance {of the design magnitude} though that area.
Even if your x-over has an impedance compensation notch filter centered on 320Hz, 500Hz is still too low to cross to the 1308.
Look at its specified Xmax, +/- 1mm, that is a very small displacement, quite sufficient for higher frequencies but not for much magnitude of output in the 500Hz region.
Rule of thumb is to cross over at least 1 octave above the Fs of a driver,
and usually 2 octaves above, unless there is some type of Impedance Compensation or mechanical Damping of the Fs' impedance.
For example, the Dynaudio D-28/2 has FerroFluid in its magnet coil gap which causes substantial reduction of what would be an impedance peak at its Fs.
Look on its Spec./Data sheet and you will see the Impedance Plot has only a slight hump at about 1kHz.
This is result of the FerroFluid damping.
Thus the D-28/2 can be got to work with a standard x-over,
presuming one does not cross too low, and how low is "too low" depends on the Slope of the x-over Filter.
For the 1308 I would apply an electrical impedance compensation, and then use a 4th Order x-over at about 650Hz so as to have signal down 24dB at Fs.
Using a Linkwitz/Riley type 4th Order, the signal would be down 6dB at 650Hz, thus the +/- 1mm excursion will cope there.
You can cross over higher than 650Hz, and then use a lower slope filter if you want to, but impedance compensation will still be necessary,
because when you get high enough above the Fs caused impedance slope-down you will then be close to the Voice-coil Inductance caused impedance slope-up,
see from above 1.5kHz region on the Impedance Plot.
There is a range where the 1308 can be crossed to the tweeter.
Studying the Frequency Response Plot, including reference to the 30 degrees off-axis plot, 5kHz or slightly above looks best for a simple x-over, but it could be crossed as high as 6.5kHz, with audible results depending on the Vertical Axis that one listens on.
It could be crossed lower than 5kHz, but crossing lower is more audibly detectable as discontinuity between the mid and treble,
albeit dependant on the type of recordings one primarily listens to.
What cross-over circuit are you using ?
And, what is your Woofer ?
Do you have any Specifications/Data, or Plots for the woofer ?
ronzeman said:
500 Hz is too low to cross to the Morel EL 1308 !
I am wondering if your short period listening has been only at fairly low Volume levels ?
Other than with some extraordinary cross-over circuit, there will be quite noticeable distortion of the lower frequencies sent to the Morel if it is driven even moderately hard, let alone to high volume level,
or are you listening in a very small room where sound seems loud with low drive levels ?
As well as distortion, there is likelihood the 1308 will be damaged if it is driven hard in the octave below 500Hz.
Have a look at the Specifications/Data sheet for the 1308.
See the large peak in the Impedance Plot centering on its Fs of 320Hz, and the Impedance does not drop to magnitude able to accept a standard x-over till above 800Hz.
Basically what happens is that the electrical interaction between the components in the x-over network and the higher than design spec. Impedance occuring so close to the x-over frequency cause the driver to receive significantly greater signal than would be the case if flat impedance {of the design magnitude} though that area.
Even if your x-over has an impedance compensation notch filter centered on 320Hz, 500Hz is still too low to cross to the 1308.
Look at its specified Xmax, +/- 1mm, that is a very small displacement, quite sufficient for higher frequencies but not for much magnitude of output in the 500Hz region.
Rule of thumb is to cross over at least 1 octave above the Fs of a driver,
and usually 2 octaves above, unless there is some type of Impedance Compensation or mechanical Damping of the Fs' impedance.
For example, the Dynaudio D-28/2 has FerroFluid in its magnet coil gap which causes substantial reduction of what would be an impedance peak at its Fs.
Look on its Spec./Data sheet and you will see the Impedance Plot has only a slight hump at about 1kHz.
This is result of the FerroFluid damping.
Thus the D-28/2 can be got to work with a standard x-over,
presuming one does not cross too low, and how low is "too low" depends on the Slope of the x-over Filter.
For the 1308 I would apply an electrical impedance compensation, and then use a 4th Order x-over at about 650Hz so as to have signal down 24dB at Fs.
Using a Linkwitz/Riley type 4th Order, the signal would be down 6dB at 650Hz, thus the +/- 1mm excursion will cope there.
You can cross over higher than 650Hz, and then use a lower slope filter if you want to, but impedance compensation will still be necessary,
because when you get high enough above the Fs caused impedance slope-down you will then be close to the Voice-coil Inductance caused impedance slope-up,
see from above 1.5kHz region on the Impedance Plot.
There is a range where the 1308 can be crossed to the tweeter.
Studying the Frequency Response Plot, including reference to the 30 degrees off-axis plot, 5kHz or slightly above looks best for a simple x-over, but it could be crossed as high as 6.5kHz, with audible results depending on the Vertical Axis that one listens on.
It could be crossed lower than 5kHz, but crossing lower is more audibly detectable as discontinuity between the mid and treble,
albeit dependant on the type of recordings one primarily listens to.
What cross-over circuit are you using ?
And, what is your Woofer ?
Do you have any Specifications/Data, or Plots for the woofer ?
Resonances in materials
Have you seen the published results for the Aerolam cabinet walls Celestion used years ago for their SL 600 and SL 700
{or SL 6000 and 7000, I have forgotten how many 00s!} ?
Wharfedale used similar in their 708 model about that time.
I'll Post more about resonances when I have sufficient time to.
They cannot be completely eliminated, but can be reduced in both magnitude any number if one chances upon the optimum choice and thicknesses of materials for the "sandwich" !
R-Carpenter said:
Have you seen the published results for the Aerolam cabinet walls Celestion used years ago for their SL 600 and SL 700
{or SL 6000 and 7000, I have forgotten how many 00s!} ?
Wharfedale used similar in their 708 model about that time.
I'll Post more about resonances when I have sufficient time to.
They cannot be completely eliminated, but can be reduced in both magnitude any number if one chances upon the optimum choice and thicknesses of materials for the "sandwich" !
A few details
Wow Alan ! That's a ton of analysis. Thanks.
Again...The morels are sealed (closed) units and sit in the same chamber as the woofer. I could not identify a better midrange that is sealed. Also the efficiency was about right too.
The system woofer is the Radford BD25 (circa 1975) No specs avail. The crossover is the Radford FN12-A (configured for use with the original TD3/2 tweeter (by Peerless).
Alan Cohen provided me with the following info / details: There is a schematic at http://homepage.mac.com/planet10/TLS/classics/images/RadfordXO.gif
Treble section 4th order 24dB/octave high pass
Mid section 2nd order 12 dB/octave bandpass
Bass section 2nd order low pass.
Having built these TL speakers in 1975 and lived with them ever since...I have long ago spent my concentration on the music more than the equipment. I very much appreciate your comments and recommendations which might help getting the most out of my system
Wow Alan ! That's a ton of analysis. Thanks.
Again...The morels are sealed (closed) units and sit in the same chamber as the woofer. I could not identify a better midrange that is sealed. Also the efficiency was about right too.
The system woofer is the Radford BD25 (circa 1975) No specs avail. The crossover is the Radford FN12-A (configured for use with the original TD3/2 tweeter (by Peerless).
Alan Cohen provided me with the following info / details: There is a schematic at http://homepage.mac.com/planet10/TLS/classics/images/RadfordXO.gif
Treble section 4th order 24dB/octave high pass
Mid section 2nd order 12 dB/octave bandpass
Bass section 2nd order low pass.
Having built these TL speakers in 1975 and lived with them ever since...I have long ago spent my concentration on the music more than the equipment. I very much appreciate your comments and recommendations which might help getting the most out of my system
One word, Phenolic 
You probably could work with it at home, but it would make short work of most carbide bits and blades. I'm having some Linen and Paper Phenolic baffles cut, and it's actually cheaper than I thought it would be.
Here's some info to peruse http://www.indplastic.com/
You probably could work with it at home, but it would make short work of most carbide bits and blades. I'm having some Linen and Paper Phenolic baffles cut, and it's actually cheaper than I thought it would be.
Here's some info to peruse http://www.indplastic.com/
TurboFC3S said:
WOW coincidence!
I just got in from the garage where I was rough trimming my Phenolic baffles to size.
The rest of the enclosure is mostly PVC...
Attachments
While no expert, I've tried to do my homework and look not only at the speaker industry, but other area's for further information on the reduction of vibrations. First, I think people need a good solid, and repeatable method of measurement, which is pretty tricky. Then you have to decide, do I want to extinguish the energy as fast as possible, or just move it out of the audio band, as the two seem to be somewhat exclusive. Of course, a solid mixture of both approaches is best, but it often seems like enclosure walls which do not hold onto energy have higher resonate frequencies.
Taking from other industries, its rather easy to see that constrained layer dampening is by far the best solution for this. It seems like a balance of stiffness and hardness is one important factor. This can be achieved by layering solid wood and mdf, or mdf and chip board, or mdf and plywood. It can also be further enhanced by layering in plastics, especially very stiff plastics like phenolic, or even by adding metal. This seems to help reduce the transmission of energy from inside the box out, or from one part of the box to another, but in and of itself, isn't enough.
Then you have bracing, from my own measurements, reviewing lots of stereophiles measurements, reading various AES papers, I have come to the conclusion that uber bracing is much more effective than uber thick baffles. I'm not saying that both aren't good, but a 6" concrete baffle isn't as effective as a 3/4" baffle with a lot of bracing added.
Another important property of a box is having the ability to evacuate the energy by changing its form from physical vibrations to heat. The most common way is the use of "dampening" materials. Tar based pads, poly fill, all of these turn vibrations into heat, and really are an important additional piece.
Ok one last bit here, there seems to be much debate over how a driver should be mounted for best vibration control. Most people seem to agree that isolating smaller drivers, say tweeters and midrange's, from the larger bass speakers is a good thing. However some feel that using something like a soft foam gasketing material is not a good thing, since the driver then has no vibration ground to evacuate energy, and must do so through its own faceplate and enclosure. This has led to some companies mounting the larger bass drivers to the rear baffle, and the front drivers to the front baffle. I'm not fully convinced that works, as I think the larger woofer will still radiate energy to the upper range drivers. Plus, I'm not completely convinced that the effort has any real impact on sound. While reducing cabinet resonances is very important, I'm not so sure that ensuring that a cabinet has no vibrations to speak of is that important.
Corian is a fine material to use, I would recomend adding a constrained layer of something stiffer like aluminum or steel. None the less, just being secured against the wood box could offer a fine enclosure with great energy evacuation and absorption properties.
Taking from other industries, its rather easy to see that constrained layer dampening is by far the best solution for this. It seems like a balance of stiffness and hardness is one important factor. This can be achieved by layering solid wood and mdf, or mdf and chip board, or mdf and plywood. It can also be further enhanced by layering in plastics, especially very stiff plastics like phenolic, or even by adding metal. This seems to help reduce the transmission of energy from inside the box out, or from one part of the box to another, but in and of itself, isn't enough.
Then you have bracing, from my own measurements, reviewing lots of stereophiles measurements, reading various AES papers, I have come to the conclusion that uber bracing is much more effective than uber thick baffles. I'm not saying that both aren't good, but a 6" concrete baffle isn't as effective as a 3/4" baffle with a lot of bracing added.
Another important property of a box is having the ability to evacuate the energy by changing its form from physical vibrations to heat. The most common way is the use of "dampening" materials. Tar based pads, poly fill, all of these turn vibrations into heat, and really are an important additional piece.
Ok one last bit here, there seems to be much debate over how a driver should be mounted for best vibration control. Most people seem to agree that isolating smaller drivers, say tweeters and midrange's, from the larger bass speakers is a good thing. However some feel that using something like a soft foam gasketing material is not a good thing, since the driver then has no vibration ground to evacuate energy, and must do so through its own faceplate and enclosure. This has led to some companies mounting the larger bass drivers to the rear baffle, and the front drivers to the front baffle. I'm not fully convinced that works, as I think the larger woofer will still radiate energy to the upper range drivers. Plus, I'm not completely convinced that the effort has any real impact on sound. While reducing cabinet resonances is very important, I'm not so sure that ensuring that a cabinet has no vibrations to speak of is that important.
Corian is a fine material to use, I would recomend adding a constrained layer of something stiffer like aluminum or steel. None the less, just being secured against the wood box could offer a fine enclosure with great energy evacuation and absorption properties.
Since we've gone on a complete tangent here, I might as well keep it going
Here's one little secret I've found through experimentation, and confirmed with accelerometer measurements. Don't make one big box and then brace it ... instead make multiple smaller boxes and then glue them all into one enclosure. Of course you'd cut out the necessary walls so they act as one volume once glued up.
I tried this with a 1.4 cu/ft floorstander using a Peerless 830884 and it turned out incredibly well. I made two cabs, one with this construction and one more traditional and used the accelerometer on both. I had trouble finding any resonant areas on the 'multi-box' cabinet, but the standard box was pretty much as expected, with resonances all over any large panels.
It takes some precision to get all the smaller boxes to perfectly line up, but a little wood filler and a lot of sanding get the job done! If a whole panel was a 32nd or so off I'd just lay cover that panel with veneer. Once you get all the panels even, glue 'em up and veneer over the whole thing.
Here's one little secret I've found through experimentation, and confirmed with accelerometer measurements. Don't make one big box and then brace it ... instead make multiple smaller boxes and then glue them all into one enclosure. Of course you'd cut out the necessary walls so they act as one volume once glued up.
I tried this with a 1.4 cu/ft floorstander using a Peerless 830884 and it turned out incredibly well. I made two cabs, one with this construction and one more traditional and used the accelerometer on both. I had trouble finding any resonant areas on the 'multi-box' cabinet, but the standard box was pretty much as expected, with resonances all over any large panels.
It takes some precision to get all the smaller boxes to perfectly line up, but a little wood filler and a lot of sanding get the job done! If a whole panel was a 32nd or so off I'd just lay cover that panel with veneer. Once you get all the panels even, glue 'em up and veneer over the whole thing.
Some good suggestions here. I have thought the idea of using a cabinet within a cabinet decoupled with a medium such as sand as an idea worthy of trying. The question is how to you completely decouple the inner cabinet from the outer cabinet as the drivers would ideally be connected to the inner cabinet?
BTW, phenolic is very expensive
BTW, phenolic is very expensive
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