Hey Antonio,
With regards to low level listening between the two I favor the 48"er.
One other significant difference, as you may have noticed on the drawings, between the two cabinets is the 31" port fires down and the low level sounds are 'bounced' into the room. It is very pleasing but you don't get that low level 'thump' in the chest with some music.
My 48"ers are ported directly out the front of the baffle. You wouldn't think it would make much of a difference but it does. I find that the low end on the 48"er has more energy and 'thump' compared to the 31". That's one of the reasons (the nice harmonic distortion GM mentioned earlier being the other) I like the 48"er better at low levels than the 31".
Certainly if you have the chance to listen to a nicely built pair do it. I'm sure you'll enjoy it. The other thing I was going to say was build them both!!
Have fun -
Bruce
With regards to low level listening between the two I favor the 48"er.
One other significant difference, as you may have noticed on the drawings, between the two cabinets is the 31" port fires down and the low level sounds are 'bounced' into the room. It is very pleasing but you don't get that low level 'thump' in the chest with some music.
My 48"ers are ported directly out the front of the baffle. You wouldn't think it would make much of a difference but it does. I find that the low end on the 48"er has more energy and 'thump' compared to the 31". That's one of the reasons (the nice harmonic distortion GM mentioned earlier being the other) I like the 48"er better at low levels than the 31".
Certainly if you have the chance to listen to a nicely built pair do it. I'm sure you'll enjoy it. The other thing I was going to say was build them both!!
Have fun -
Bruce
Bruce,
What you are saying is what I imagined somehow. However, I also thought that a bigger cabinet would require more volume for the sound to come alive than a smaller one since the driver would need to generate more pressure for the low frequencies to emerge. I do not know the theory or the mechanics involved and am just speculating. I'll try to do my homework but it would be interesting to hear some more expert opinions.
Next week I will try to listen to Nardis' 48's . It would be great if there was a Londoner with 31's to compare.
I know myself and am sure I will end up building them both, but at the moment that is too ambitious.
Antonio
What you are saying is what I imagined somehow. However, I also thought that a bigger cabinet would require more volume for the sound to come alive than a smaller one since the driver would need to generate more pressure for the low frequencies to emerge. I do not know the theory or the mechanics involved and am just speculating. I'll try to do my homework but it would be interesting to hear some more expert opinions.
Next week I will try to listen to Nardis' 48's . It would be great if there was a Londoner with 31's to compare.
I know myself and am sure I will end up building them both, but at the moment that is too ambitious.
Antonio
A Sanchez said:
If the cab is just a bigger rectangular box, you're right, but the point of pipe loading is to let it do the work, so actually takes less power for a given SPL, but the price you pay is increased distortion in the form of increasing delay of the driver and port signals with increasing length with the 31" being what I consider the max acceptable trade-off between pipe gain and excessive delay for this particular driver's specs.
GM
Colin said:
Correctomundo! Aspect ratios > ~9:1 add enough friction running towards aperiodic with increasing ratio, so in most cases the driver's depth limits how much you can 'pancake' them.
FWIW, my most popular designs were these except instead of a rectangular shape the baffle was 'bent' back to side firing vent(s) as required. IOW a simple vertical kerf on each side of the driver to 'break' the baffle back to whatever aspect ratio side firing vent(s) up to ~9:1 tuned it to minimize thickness at this point. Due to not having any elaborate test gear or design software, tuning was accomplished by starting with the sides brought ~ to an unfinished, unsecured point, then I would cut small, equal 'slices' off each side until I got a ~flat in-room response. Obviously time consuming and may render the speakers ~ useless if relocated, but with today's software you could design in removable vent ducts.
GM
hello,
After much reviewing I am strongly considering building the triangle 48er. Recent posts #54 and 55 - making the triangle wider - gives rise to a question:
I assume 'wider' refers to the baffle's external front face only, both the internal cross sectional area, maintaining the as-illustrated equilateral triangle, and volume remain the same? Also, although I promise not to "worry about that too much", a few inches, 12 inches, more?
Very generally, if the front face of the triangle 48er had surface curvature, are there any guidelines on this or with this design the front baffle should remain flat? I notice numerous commercial and some diy speakers have all manner of front baffle face surface geometry, grooves, etc., accompanied both by convincing as well as dubious claims of increased performance.
Thank you.
After much reviewing I am strongly considering building the triangle 48er. Recent posts #54 and 55 - making the triangle wider - gives rise to a question:
I assume 'wider' refers to the baffle's external front face only, both the internal cross sectional area, maintaining the as-illustrated equilateral triangle, and volume remain the same? Also, although I promise not to "worry about that too much", a few inches, 12 inches, more?
Very generally, if the front face of the triangle 48er had surface curvature, are there any guidelines on this or with this design the front baffle should remain flat? I notice numerous commercial and some diy speakers have all manner of front baffle face surface geometry, grooves, etc., accompanied both by convincing as well as dubious claims of increased performance.
Thank you.
Hi dsb,
You are correct, maintaining the cross-section area and other internal dimensions is critical. You can be as 'artistic' as you like with the external part of the cabinet.
The front baffle on my 48"ers is 1" thick and 23" wide. Some people will say a 1" baffle is overkill, but I had the wood and it looks great! You can make the front baffle as wide as you like. I think wider makes it better.
Can't help you much about the curved front baffle. Sounds interesting though.
Stay warm -
Bruce
You are correct, maintaining the cross-section area and other internal dimensions is critical. You can be as 'artistic' as you like with the external part of the cabinet.
The front baffle on my 48"ers is 1" thick and 23" wide. Some people will say a 1" baffle is overkill, but I had the wood and it looks great!
You can make the front baffle as wide as you like. I think wider makes it better.Can't help you much about the curved front baffle. Sounds interesting though.
Stay warm -
Bruce
GM,
Did you use the published specs for the GM48 & GM31?
This data just in from a sampling of the latest 100 from Sweden
http://www.diyaudio.com/forums/showthread.php?postid=1426136#post1426136
higher Vas, lower Q, lower Vas than spec
dave
Did you use the published specs for the GM48 & GM31?
This data just in from a sampling of the latest 100 from Sweden
http://www.diyaudio.com/forums/showthread.php?postid=1426136#post1426136
higher Vas, lower Q, lower Vas than spec
dave
Greets!
I just used the published specs at the time and bumped up Qes/Qts a little bit to account for VC heating since JG's small monitor measured pretty much dead on and TJ's TL simmed good using them. For sure, I find it hard to believe that any of these alignments would be popular based on how they sim with these latest specs.
GM
I just used the published specs at the time and bumped up Qes/Qts a little bit to account for VC heating since JG's small monitor measured pretty much dead on and TJ's TL simmed good using them. For sure, I find it hard to believe that any of these alignments would be popular based on how they sim with these latest specs.
GM
dsb said:
Greets!
Right, though the internal angles can be changed as long as the CSA is at least as large as spec.
WRT curvature, consider the size of the WLs involved. A 100 Hz WL has a ~21.6" radius, so even if it was ~21.6" wide measured on the 'flat' it wouldn't have that great of a curvature acoustically as far as higher frequency wave launch was concerned.
Where curvature plays a role in superior performance is reducing standing waves amplitude or getting rid of them altogether and the funky shapes some cabs have are addressing this issue. Here you have to work with the 1/2 WL length size of two end points, so our ~21.6" baffle is going to be slightly longer over its surface or ~308 Hz wide, so to reduce its standing wave amplitude considerably we have to round over the edges with a 7" radius, leaving a curved center section that now looks ~flat, though as far as the 100 Hz wave launch is concerned it still looks relatively flat acoustically.
GM
Hi,
Back to the project.
Last week I paid a visit to Nardis' who very kindly offered me the chance to listen to his pentagonal 48’ towers. I was very impressed by the speakers, which by far exceeded my expectations. Nardis has very high quality equipment and I would be happy if the drivers perform half as well with my set up. The pentagons look very elegant and I am sure the smaller panel areas and having no parallel sides are an important plus in sound quality, but at this first stage I prefer not to get into the trouble of cutting and assembling that design, which is a bit tricky.
I have decided to go for the 31’ version. Since I am new to this and do not have much parameters to compare, I believe it is better to start by getting used to the design which is more “pure”. In any case after listening to Nardis' 48’s I can see that there should also be plenty of bass power for my needs and room size with the 31’version . My current B&W 601s have frequency response down to 70hz and I already feel is quite a lot. So if I get down to 45hz with the 31’s that should be more than enough for me (at least for now).
I already have the drivers and I just have to decide about the design:
One option is to do the 31’ using the baffle size applied by Jim Griffin with his mini monitors and his 46’ Jordan MLTL version (7.5’) as this would allow me in the future to add the Aurum Cantus G2Si using Jim’s crossover configuration, which is a proven design. I will obviously keep the original CSA intact.
Since I have some problems with WAF, another option is to copy DIAR’s design http://kotiweb.kotiportti.fi/~w439893/DIY/Jordan/Jordan1/ which in my opinion has the most elegant looks as the narrow (only around 6') baffle produces, aesthetically, very nice proportions, by increasing the depth in order to keep the original CSA. From what I have learnt the problem with this design would be that Jordan’s perform better with wide baffles. But, would you think there would be a clearly noticeable difference between 6 and 7.5 inches?
Another thing I was thinking was to build the bottom window at the back instead of the front. I thought this may help to have more room interaction and possibly more room gain on the lower frequencies by trying different locations. Would anyone think this could be counterproductive?
Your comments will be again very appreciated.
Best regards
Antonio
Back to the project.
Last week I paid a visit to Nardis' who very kindly offered me the chance to listen to his pentagonal 48’ towers. I was very impressed by the speakers, which by far exceeded my expectations. Nardis has very high quality equipment and I would be happy if the drivers perform half as well with my set up. The pentagons look very elegant and I am sure the smaller panel areas and having no parallel sides are an important plus in sound quality, but at this first stage I prefer not to get into the trouble of cutting and assembling that design, which is a bit tricky.
I have decided to go for the 31’ version. Since I am new to this and do not have much parameters to compare, I believe it is better to start by getting used to the design which is more “pure”. In any case after listening to Nardis' 48’s I can see that there should also be plenty of bass power for my needs and room size with the 31’version . My current B&W 601s have frequency response down to 70hz and I already feel is quite a lot. So if I get down to 45hz with the 31’s that should be more than enough for me (at least for now).
I already have the drivers and I just have to decide about the design:
One option is to do the 31’ using the baffle size applied by Jim Griffin with his mini monitors and his 46’ Jordan MLTL version (7.5’) as this would allow me in the future to add the Aurum Cantus G2Si using Jim’s crossover configuration, which is a proven design. I will obviously keep the original CSA intact.
Since I have some problems with WAF, another option is to copy DIAR’s design http://kotiweb.kotiportti.fi/~w439893/DIY/Jordan/Jordan1/ which in my opinion has the most elegant looks as the narrow (only around 6') baffle produces, aesthetically, very nice proportions, by increasing the depth in order to keep the original CSA. From what I have learnt the problem with this design would be that Jordan’s perform better with wide baffles. But, would you think there would be a clearly noticeable difference between 6 and 7.5 inches?
Another thing I was thinking was to build the bottom window at the back instead of the front. I thought this may help to have more room interaction and possibly more room gain on the lower frequencies by trying different locations. Would anyone think this could be counterproductive?
Your comments will be again very appreciated.
Best regards
Antonio
t-head said:
T-head,
Do you have GM's 31' MLTL? the thing with the 31' version is that as a matter of fact the port fires downwards and I am just intending to move the window to the back, which might not make much difference. I imagine that few inches would not much difference in terms of baffle size, except maybe for very well trained ears
Antonio
Antonio,
No, I have the JLMs from Carolina Audio. 36"x6.5"Wx6A"D. I imagine the design internals similar to the triangular design on Jordans site. Quarter-wave, 3x folded design with rear-firing rectangular port.
http://rthack.tripod.com/KOTA/Page_7.html
wider baffles do assist bass, but I have not found the difference huge...Good Luck with your build!
t
No, I have the JLMs from Carolina Audio. 36"x6.5"Wx6A"D. I imagine the design internals similar to the triangular design on Jordans site. Quarter-wave, 3x folded design with rear-firing rectangular port.
http://rthack.tripod.com/KOTA/Page_7.html
wider baffles do assist bass, but I have not found the difference huge...Good Luck with your build!
t
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