Dave-
Now I did it with you 🙄
I'll have to see if "Paint" has that option (thats what I "paste" into).
Leave it to a graphics guy to get all "your graphs are fuzzy" on me 😀
-Casey
Now I did it with you 🙄
I'll have to see if "Paint" has that option (thats what I "paste" into).
Leave it to a graphics guy to get all "your graphs are fuzzy" on me 😀
-Casey
Dave-
Here ya go...GIF images (clueless as to the bit count) of the response and, excursion with .33lb ft^3 in the last leg of the line...
Definitely better than the jpg's. Thanx for settin' me straight.
-Casey
Here ya go...GIF images (clueless as to the bit count) of the response and, excursion with .33lb ft^3 in the last leg of the line...
Definitely better than the jpg's. Thanx for settin' me straight.
-Casey
valveitude said:
8-bit... but there is only 3-bits of information in the image so it only added 900 bytes to the files size.
dave
454Casull said:
454, aka. Big guns....😉
This was WAAAAY long ago when I was a kid, we had 2 strokes with a stinger pipe (expansion chamber with a long terminis as a restriction). You are correct, improved velocity, but we thought it was backpressure sensitive as well.? Not being an Enganeer, only a Contractor I was never schooled in physics. I defer to your knowledge...
Thanks Ron
Greets!
They were/are. Just like a MLTL, etc., you use the vent length and stuffing to fine tune the system's Fb and Q, aka gain BW, for a muffler/expansion pipe is a low pass filter and without a certain amount of back pressure you don't get good intake loading/exhaust scavenging (aka volumetric efficiency).
Regardless, we're not talking about guns, where normally you want to maximize muzzle velocity, but about reducing velocity (vent mach) at the 'muzzle' (terminus) while maximizing gain BW.
GM
They were/are. Just like a MLTL, etc., you use the vent length and stuffing to fine tune the system's Fb and Q, aka gain BW, for a muffler/expansion pipe is a low pass filter and without a certain amount of back pressure you don't get good intake loading/exhaust scavenging (aka volumetric efficiency).
Regardless, we're not talking about guns, where normally you want to maximize muzzle velocity, but about reducing velocity (vent mach) at the 'muzzle' (terminus) while maximizing gain BW.
GM
Thanx 😉 Now I can pretend I'm in a shop, instead of a foo-foo fabric store (better for my fragile self esteem).."could you hand me that tool?".
-Casey
GM-
You've really put a "bug" in my noggin with this one 🙂.
I believe I have a grasp of the basic principle, partially "shorting" the line by allowing some of the back wave to cancel the front wave, but I'm trying to figure out where the "knee" of the downward trend would occur. If it's the same as open air, wouldn't that start the attenuation up in the lower mid's?
I'm trying to decide if I want to set up my baffle to make this method of tuning easier. In principle it sounds more apealing to me than "choking" the line.
-Casey
You've really put a "bug" in my noggin with this one 🙂.
I believe I have a grasp of the basic principle, partially "shorting" the line by allowing some of the back wave to cancel the front wave, but I'm trying to figure out where the "knee" of the downward trend would occur. If it's the same as open air, wouldn't that start the attenuation up in the lower mid's?
I'm trying to decide if I want to set up my baffle to make this method of tuning easier. In principle it sounds more apealing to me than "choking" the line.
-Casey
Greets!
We're talking about a resistive pressure leak, ergo tiny, so no pure dipole action. If you want more tunability, then mount the driver on a separate adjustable baffle with a chamfered driver mtg. hole in the main baffle to create a larger/longer 'vent'.
GM
We're talking about a resistive pressure leak, ergo tiny, so no pure dipole action. If you want more tunability, then mount the driver on a separate adjustable baffle with a chamfered driver mtg. hole in the main baffle to create a larger/longer 'vent'.
GM
GM-
As is typical, your suggestion is a hell of a lot more elegant than the contraption I was dreaming up🙄. Something to be said for your years of experience 😉
So were not talking dipole cancellation, but rather leakage. OK then, in your estimation were would you suspect the "knee" of the roll off to begin? I imagine this point would be dynamic, and follow the degree to which it's leaking to some extent, but you probably have a good idea of the "range".
-Casey
As is typical, your suggestion is a hell of a lot more elegant than the contraption I was dreaming up🙄. Something to be said for your years of experience 😉
So were not talking dipole cancellation, but rather leakage. OK then, in your estimation were would you suspect the "knee" of the roll off to begin? I imagine this point would be dynamic, and follow the degree to which it's leaking to some extent, but you probably have a good idea of the "range".
-Casey
Planet10 has a site I visit from time to time. Dave (Thanks, Dave!) has recently added a site (its much more than a page...ok, it includes eye candy)...anyway, something that assures me I'm not out on this limb by myself...I mean people actually think about this stuff and find ways to deal with it...
Look at this. They call them fillets/carrots. They are used for tuning a cabinet that is already built. That has got to be such an elegant means to an end....and its just one tid bit...
click on over
They can be found here: http://www.frugal-horn.com/daleks.html
Ahhh, GM has shared a nugget as well. Class in session!
Look at this. They call them fillets/carrots. They are used for tuning a cabinet that is already built. That has got to be such an elegant means to an end....and its just one tid bit...
click on over
An externally hosted image should be here but it was not working when we last tested it.
They can be found here: http://www.frugal-horn.com/daleks.html
Ahhh, GM has shared a nugget as well. Class in session!
Ed-
Thanx for the tip, I'll be heading that way shortly.
GM-
One more Q (for now😉), what would you estimate the widest gap could be, in other words how deep should I cut the baffle?
-Casey
Thanx for the tip, I'll be heading that way shortly.
GM-
One more Q (for now😉), what would you estimate the widest gap could be, in other words how deep should I cut the baffle?
-Casey
Greets!
Yeah, the early designers didn't miss a trick, using semi-transparent driver surrounds (or no surround at all!) to ~aperiodically load to non-optimum size cabs.
Right, highest pressure first, which is broadband, so a general shelving, similar to series resistance, ergo the 'knee' begins at Fp and shifts upward with increasing gap until true dipole cancellation occurs.
GM
Yeah, the early designers didn't miss a trick, using semi-transparent driver surrounds (or no surround at all!) to ~aperiodically load to non-optimum size cabs.
Right, highest pressure first, which is broadband, so a general shelving, similar to series resistance, ergo the 'knee' begins at Fp and shifts upward with increasing gap until true dipole cancellation occurs.
GM
Ed,
Those look a lot like the balast(s) put into Kayaks to help decrease the volume of possible water intrusion . Not like I know anything about falling out of one. 🙂
Ron
Those look a lot like the balast(s) put into Kayaks to help decrease the volume of possible water intrusion . Not like I know anything about falling out of one. 🙂
Ron
Dave, Ed, et al-
I have been trying to listen carefully to all the suggestions I've been given regarding the desired response of my TL. I went to the site Ed linked to, and just looked at Scottmoose's "Shadow" plot in Cal's horn thread..now I'm really confused. The horns in the link that Ed gave have a very flat response from the 200hz down to the "knee", and the "Shadow" has a very flat response all the way down, except for a slight droop on the last octave.
The confusion comes from being told that my uber-flat response curve would manifest itself into a "bloated" presentation once room gain was factored in, yet the designs I mentioned would appear to have similiar responces, and they were designed by people that seem to know a heck of a lot more than I do, and by all reports, sound great.
What am I missing?
-Casey
I have been trying to listen carefully to all the suggestions I've been given regarding the desired response of my TL. I went to the site Ed linked to, and just looked at Scottmoose's "Shadow" plot in Cal's horn thread..now I'm really confused. The horns in the link that Ed gave have a very flat response from the 200hz down to the "knee", and the "Shadow" has a very flat response all the way down, except for a slight droop on the last octave.
The confusion comes from being told that my uber-flat response curve would manifest itself into a "bloated" presentation once room gain was factored in, yet the designs I mentioned would appear to have similiar responces, and they were designed by people that seem to know a heck of a lot more than I do, and by all reports, sound great.
What am I missing?
-Casey
An externally hosted image should be here but it was not working when we last tested it.
I've brought the response plot of the Shadow (2 Extremis) over here to confirm this...I do see ~ 7-8 dB change from 20-40 hz, and maybe 4 dB from 40-80. The response does fall around 12 dB. Is this the view you refer to?
Ed Lafontaine said:
Just about right if you are counting on 6 dB/octave (or a bit less) room gain below 80 Hz.
Casey can adjust his line to get similar response, but the big gain in Shadow is the reduction in excursion so the bottom octave is not as excursion limited.
dave
Ed-
Thats the one. To my eye, that looks like around -4dB at 30, and -9dB at 20. My line shows flat (more or less), at 30, and -10db@ 20. I guess the desired bass cut isn't as deep as I first believed.
Dave-
Though I agree the limiting of excursion is desireable, I'm not sure how critical it is with the Extremis. I have read in a couple places in this forum that they are near impossible to bottom. One report had the driver sitting open air with over 300 watts feeding it, another had 2 in a dipole with 1000w..neither case bottomed the driver(s).
Basically I'm not so nervous as I was. Peeling back the 30 hz point a few dB is a simple matter of extending the current rate of stuffing to the throat of the flare.
-Casey
Thats the one. To my eye, that looks like around -4dB at 30, and -9dB at 20. My line shows flat (more or less), at 30, and -10db@ 20. I guess the desired bass cut isn't as deep as I first believed.
Dave-
Though I agree the limiting of excursion is desireable, I'm not sure how critical it is with the Extremis. I have read in a couple places in this forum that they are near impossible to bottom. One report had the driver sitting open air with over 300 watts feeding it, another had 2 in a dipole with 1000w..neither case bottomed the driver(s).
Basically I'm not so nervous as I was. Peeling back the 30 hz point a few dB is a simple matter of extending the current rate of stuffing to the throat of the flare.
-Casey
Greets!
Sniff.... must be nice living in a house with this much gain..... sniff. I don't measure but 3-4 dB with them stuffed in the corners and there's no appreciable room gain using the SLM's lowest frequency band (20 Hz). If you have all this room gain, why do you need much driver excursion headroom? I never did in corner loads or the few basement rigs that had a near perfect 2nd order slope like in some vehicles.
Anyway, we put this issue to bed awhile back, so I don't understand the confusion.
GM
Sniff.... must be nice living in a house with this much gain..... sniff. I don't measure but 3-4 dB with them stuffed in the corners and there's no appreciable room gain using the SLM's lowest frequency band (20 Hz). If you have all this room gain, why do you need much driver excursion headroom? I never did in corner loads or the few basement rigs that had a near perfect 2nd order slope like in some vehicles.
Anyway, we put this issue to bed awhile back, so I don't understand the confusion.
GM
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