sorry guys, haven't taken much interest in improving on the ss15 design -- it just works so well for my intended goal. I've found in reverberant spaces (gyms) that a gentle roll off from 60-40hz and a steep high pass at 40hz actually helps in the bass department. I have what I can subjectively say is 'cleaner' bass vs if I try to eq to flat. (testing 2.83v@1m) I've been known to add a couple db eq at 45hz, but only a couple, I don't try to get absolutely flat. I still get that really low satisfying bass feel, without some of the mud.
Unfortunately for a single sheet design -- it is a see-saw. Cabinet volume -- there is no replacement for displacement, hoffmans iron law, etc... When I try to maximize cabinet volume, I reduce the amount of wood available for interior panels, which limits the length of the horn, which limits the Fc. So to go lower, requires a smaller cabinet, which reduces overall spl.... and then figuring out how to cut it all out of a 4x8 sheet... It's kind of a maddening process...
you are all welcome to help me improve it..... (being serious here) I would appreciate the suggestions.
1.5 sheet = + aprox 3dB ... or 1/2 octave lower
take your pick
Even a couple inches that will give extra length will drop more dB than it will give that low extension you are looking for... As I said before you got the max efficiency out of an sheet already I think and maybe its time to move on (just a suggestion).
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no need to be sorry. You have already contributed an enormous database to the Forum. Thanks.
Hi Y'all,
You can obviously improve on the documentation of the SS15, but making a meaningful difference in the output is not going to be easy, and you'll be leaving the single sheet concept behind. Also, looks like everytime you lower the F3 you will increase the excursion for a given input voltage.
Here is a 300L with a short coupling duct from throat chamber to S1/S2, by no means a single sheet:
Regards,
You can obviously improve on the documentation of the SS15, but making a meaningful difference in the output is not going to be easy, and you'll be leaving the single sheet concept behind. Also, looks like everytime you lower the F3 you will increase the excursion for a given input voltage.
Here is a 300L with a short coupling duct from throat chamber to S1/S2, by no means a single sheet:
Regards,
Thanks djim: Your encouragement is always appreciated.
I agree at this point the ss15 design would most likely be spl diminished by trying to get more 40hz. If I could get a couple more db at 40-45hz, all else equal -- I would love to have it. I just don't know how to get there.
I've also tried other drivers in this cabinet, and haven't found any other driver that does more on the same input power. Any of the places that wholesale eminence sell the 3015lf for less than $110, so in terms of bang for the buck.. I sure can't find a better priced option.
So, either cabinet design or driver choice -- I agree -- I think the ss15 is about as good as it gets with the parameters that I originally set out.
(there's this little part of me... that is never satisfied however.....)
that's what hornresp is for. You didn't mention the specific driver, but the hornresp for the ss15 is documented in this thread -- play around with drivers and if you find a winner, please post it.
Actually Jbell, it was your encouragement to join posting in the first place. Funny thing is I don’t post all findings as it doesn’t seem 'useful' around here. Sometimes I get the feeling some among us prefer to use their energy and knowledge to show somebody’s mistake instead of using their abilities to improve or find the correct answers...
Anyway, as you said yourself "I've also tried other drivers in this cabinet, and haven't found any other driver that does more on the same input power." Of course you can’t find that driver. The max volume displacement of the 3015LF is matched to the SS15 for the balance between usable frequency and SPL. Any change will cost…
Every driver has a maximum air displacement. This max air displacement can be used for max dB (efficiency) and usable freq. response (bandwidth) and both factors are linked to the volume of a system. More volume gives more efficiency and freq extension until the max air displacement of the driver is used (effective loading). From that point the efficiency factor or the freq extension will start to drop.
Therefore I’m saying leave the SS15 as it is. It gives max efficiency in a best ratio between volume and low frequency and economics (driver and one sheet). I know you looking for that fraction more low freq extension (like many others including myself). Like Oliver I also think it doesn’t look possible within the limitation you set out yourself. So that’s the reason why I think to move on and make new standards for another JBell winner. Oh and believe me I have watched this SS15 all over and over and... and over....
I well be making 8 of the SS15's the only changes will be to try and decrease the restriction at the last bend and make it out of 3/4" ply, so the over all box will be somewhat bigger. I will start a sketchup tomorrow and will post my progress.
Will this put me in the running for a Mars Bar?
Andy
Will this put me in the running for a Mars Bar?
Andy
That will be me
.. I'm building four, and after a few more hours of work, they will be ready for paint and overall finish .. Really looking forward to it ! Results will be reported as soon as they are alive!Thanks tb46; I will look at that, but I was thinking of just dropping the bottom some. I have the change the hole box anyway to make it out of 3/4" ply and may add 1 or 2 inchs to all sides. This may make the path lenght a little longer so I will have to re-sim it too.
Anyway I will be using more than one sheet, maybe 1 and 1/4 or 1 and 1/2 sheets.
Andy
What I see as the "slight" limitation of the ss15 and similar 1sheet designs is restricted LF extension has been adopted as a compromise to maintain high usable SPL.
In a domestic situation high usable SPL is not usually the problem.
A flat response is similarly not a problem if some room gain is taken into account in the smaller and medium size rooms.
The low Q type of response, similar to a Bessel response, rather than a Butterworth works well in domestic listening.
I see some solution to the need for extended LF as a longer path length which will extend the response but as with all compromises reduce the max SPL at the lower frequencies.
If this reduced SPL were to follow the Bessel Q then we could end up with a better reproduction bass speaker for domestic listening.
A 1.5sheet design is still not big and for those wanting/needing more SPL simply stack a second 1.5sheet box alongside.
This is quite different target from Jbell's original brief.
If there is interest in such a domestic extended LF 1.5sheet TH with Bessel Q rolloff, it should probably be discussed in a new thread.
The question is
"is there interest?"
In a domestic situation high usable SPL is not usually the problem.
A flat response is similarly not a problem if some room gain is taken into account in the smaller and medium size rooms.
The low Q type of response, similar to a Bessel response, rather than a Butterworth works well in domestic listening.
I see some solution to the need for extended LF as a longer path length which will extend the response but as with all compromises reduce the max SPL at the lower frequencies.
If this reduced SPL were to follow the Bessel Q then we could end up with a better reproduction bass speaker for domestic listening.
A 1.5sheet design is still not big and for those wanting/needing more SPL simply stack a second 1.5sheet box alongside.
This is quite different target from Jbell's original brief.
If there is interest in such a domestic extended LF 1.5sheet TH with Bessel Q rolloff, it should probably be discussed in a new thread.
The question is
"is there interest?"
For a 'domestic situation' you are very correct, spl isn't the issue -- cabinet size and LF response typically are.
Room modes are dominant... but not as dominant as 'others' who get to dictate how big the subs can be that are built and brought in from the garage.....
For that situation, I think couple of mike's design is about perfect. Reed Exodus Anarchy 25hz Tapped Horn - AVS Forum
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The dominant one
likes my pair of JBL control 1 Pro in the lounge... but would prefer something smaller.
Bose cubes are clearly made for...
...wait a moment, must not think sexist thoughts!
If doing a rebuild, you could sneak in a thicker wall or lower ceiling with a tapped horn in it. Might do some 'sound' renovation work when my fiance is away for 3 weeks this summer.
likes my pair of JBL control 1 Pro in the lounge... but would prefer something smaller.
Bose cubes are clearly made for...
...wait a moment, must not think sexist thoughts!
If doing a rebuild, you could sneak in a thicker wall or lower ceiling with a tapped horn in it. Might do some 'sound' renovation work when my fiance is away for 3 weeks this summer.