Scott, pull us back if we go too far from topic. 😉
How about silicone caulk for the adhesive with the weight of cement board supported by the cross braces or the bottom of the case?
My interest in accessibility was to explore options of stuffing/lining with fiberglass.
Regards
How about silicone caulk for the adhesive with the weight of cement board supported by the cross braces or the bottom of the case?
My interest in accessibility was to explore options of stuffing/lining with fiberglass.
Regards
Floor Loading
Thanks GM:
At what point does the gap between the bottom of the cabinet and the floor begin to impact the effect of the port.
I have been experimenting with stone as a base material and using various "leg" lengths. I expect there is a relationship with leg length and equivalent free air space. Could you discuss this a little for me.
Thanks
Thanks GM:
At what point does the gap between the bottom of the cabinet and the floor begin to impact the effect of the port.
I have been experimenting with stone as a base material and using various "leg" lengths. I expect there is a relationship with leg length and equivalent free air space. Could you discuss this a little for me.
Thanks
Strewth, where did all those posts come from? 😉
All interesting stuff (miserable pun intended. Many apologies.) that’s useful anyway, and a lot is applicable to the new sheet too I think.
Re the question on port positions, I tend to lift it up 3”-4” from the internal bottom of the enclosure as I find it generally seems to cut ripple in the lower-mids a bit whilst still coupling to the floor well. The driver I try to position to suppress the third harmonic if practicable, though I don’t invariably stick to that –depends on application. Up until Greg suggested these longer pipes, which I hadn't really considered before, I'd tended to do something similar to BB and restrict the height of the enclosure, in my case to an internal max of 45" as they don't dominate the room as much. Daft really as I've got 60" ML TQWTs and 68" tall BIB pipes in my room...
I’ve found in my own limited experience with floor-firing ports that the greatest differences seem to be between ½”-2” in adjusting the level of damping applied to the port. Most of this is still empirical as far as I know, as Martin has yet to look into them thoroughly –unless GM has come up with anything in this regard? I don't know if a relationship has been mathematicaly worked out yet or not, though I'd be delighted if it has! Personally, I like them. They can give a very clean, very fast, and very powerful boost, driving the vertical mode of the room. Possibly best not in corners though –that’s only my subjective opinion and experience in one room however.
Greg –I suspect the difference in our results is down to me filling in the blanks that Fostex don’t provide on their site / data sheet with the measurements taken from a pair after purchase that I was sent a year or so back. Since you mention even the IB curve is a bit different, that must be it. And I think I've just found it too -8" driver, right. The FE206E and 207E: 206cm^2 Sd. Nothing on the data sheet for the F200a and what I assume is a typo in the data I had: F200a Sd: 226cm^2. Groan. I should have picked up on that.
For what it’s worth, and in mine own defence, as Shakespeare would have it, the rest correlate very well –the drivers were only + / - around 1% off what Fostex says they are supposed to be (impressive) so I didn’t see any reason to disbelieve them. I’ll check again to make sure -I'm now suspicious of the other bits, like Bl if memory serves, that I used. But that's just excuses, which I hate, and I freely hold my hands up on that one; completely my fault. Well, I did say in the first post that I'd make some very stupid, and very public mistakes on a regular basis!
I know what you mean about having to present a flat response in the anechoic predictions –not ideal, but difficult to depart from without lengthy explanations about why the response is drooping etc. Perhaps something pre-written to be cut and pasted into a post… 😉 Out of interest (sorry if I’m asking a stupidly obvious question here!): how / what method do you use for calculating your MLTL designs etc?
Regards to all
Scott
All interesting stuff (miserable pun intended. Many apologies.) that’s useful anyway, and a lot is applicable to the new sheet
Re the question on port positions, I tend to lift it up 3”-4” from the internal bottom of the enclosure as I find it generally seems to cut ripple in the lower-mids a bit whilst still coupling to the floor well. The driver I try to position to suppress the third harmonic if practicable, though I don’t invariably stick to that –depends on application. Up until Greg suggested these longer pipes, which I hadn't really considered before, I'd tended to do something similar to BB and restrict the height of the enclosure, in my case to an internal max of 45" as they don't dominate the room as much. Daft really as I've got 60" ML TQWTs and 68" tall BIB pipes in my room...
I’ve found in my own limited experience with floor-firing ports that the greatest differences seem to be between ½”-2” in adjusting the level of damping applied to the port. Most of this is still empirical as far as I know, as Martin has yet to look into them thoroughly –unless GM has come up with anything in this regard? I don't know if a relationship has been mathematicaly worked out yet or not, though I'd be delighted if it has! Personally, I like them. They can give a very clean, very fast, and very powerful boost, driving the vertical mode of the room. Possibly best not in corners though –that’s only my subjective opinion and experience in one room however.
Greg –I suspect the difference in our results is down to me filling in the blanks that Fostex don’t provide on their site / data sheet with the measurements taken from a pair after purchase that I was sent a year or so back. Since you mention even the IB curve is a bit different, that must be it. And I think I've just found it too -8" driver, right. The FE206E and 207E: 206cm^2 Sd. Nothing on the data sheet for the F200a and what I assume is a typo in the data I had: F200a Sd: 226cm^2. Groan. I should have picked up on that.
For what it’s worth, and in mine own defence, as Shakespeare would have it, the rest correlate very well –the drivers were only + / - around 1% off what Fostex says they are supposed to be (impressive) so I didn’t see any reason to disbelieve them. I’ll check again to make sure -I'm now suspicious of the other bits, like Bl if memory serves, that I used. But that's just excuses, which I hate, and I freely hold my hands up on that one; completely my fault. Well, I did say in the first post that I'd make some very stupid, and very public mistakes on a regular basis!
I know what you mean about having to present a flat response in the anechoic predictions –not ideal, but difficult to depart from without lengthy explanations about why the response is drooping etc. Perhaps something pre-written to be cut and pasted into a post… 😉 Out of interest (sorry if I’m asking a stupidly obvious question here!): how / what method do you use for calculating your MLTL designs etc?
Regards to all
Scott
Ed Lafontaine said:
Greets part deux to you too! 😉
Don't know if silicone has enough bond/sheer strength. The object of constrained layer damping is to grossly mismatch mechanical impedances via a super lossy 'bridge', so if one is rigidly mounted, the other can't be, ergo no, it can't be supported in any way to work properly.
GM
This product might be an alternative to attach backer board:http://audioalloy.com/b10-00_products.htmlEd Lafontaine said:
New topic - Stuffing and Lining Enclosures
I started a topic for stuffing and lining of enclosures, to accumulate both design and materials information...
http://www.diyaudio.com/forums/showthread.php?s=&threadid=71554
I started a topic for stuffing and lining of enclosures, to accumulate both design and materials information...
http://www.diyaudio.com/forums/showthread.php?s=&threadid=71554
Martin, how well does your software simulate terminated lines, such as those in the B&W Nautilus speakers?
I have never built and measured a terminated line. But all the math is the same as the open ended TL worksheets so I see no reason that an accurate SPL result would not be predicted.
Scottmoose said:
Greets!
My fingers temporarily got 'verbal' diarrhea. 😉
Ah, measured specs, that explains some of it, and I just noticed I only used 0.2 lbs/ft^3 stuffing density in the first 5th of the length, which would explain at least some of the extra roll off of your sims as I imagine your 0.25 lbs/ft^3 is down the entire length if you haven't changed the WS for more flexibility.
FWIW here's the specs I used:
Fs = 30 Hz
Re = 7.3 ohms
Lvc = 0
BL = 8.08 (calc'd)
Sd = 206 cm^2
Rs = 2.35 ohms
Vd = 98.96 L
Qed = 0.36
Qmd = 2.63
Qtd = 0.403 (auto calc includes Rs)
I tried explaining, but it mostly just provoked more explaining needing to be done, so gave up.
I use a combination of simplified 1/4 WL mechanical resonance and T/S vented alignment theory since I can't do the real math that MJK, etc. uses. Since CSA is proportional to length and driver position a function of both CSA and length, then for the longer ones I just lower Fp until the driver offset is at the desired height.
GM
SCD said:
Greets!
You're welcome!
Well, it's room position dependent and I never did any rigorous testing, but I derived a minimum gap formula for no obvious compression when well away from any boundaries that I use to get a first approximation:
Gm= (Av*(Dv*k*3))/Pb
where:
Gm = minimum gap
Av = vent area
Dv = vent diameter
Pb = base perimeter
k = flanged end: 0.425, free end: 0.307
e.g.:
both ends flanged, k = 0.425 + 0.425 = 0.850
one flanged, one free, k = 0.425 + 0.307 = 0.732
both ends free, k = 0.307 + 0.307 = 0.614
Ergo a typical round, square, or rectangular vent not too near an internal wall has a k = 0.732.
For example, a 4" dia. vent in the bottom of a 12" o.d. square cab:
(((4^2*pi)/4)*(4*0.732*3))/(4*12) = 2.3" min.
GM
Is this the same man who said in the previous post to me that he can't do 'real' math? Oh, my aching head! My math education at school was apalling -I grew up in a time and went through a school where we were taught nothing of any interest or value; I'm only just learning some of the more useful things now, through reading posts by Martin, yourself etc. Perhaps I should go and buy a textbook and try learning some of the stuff I wasn't taught!
Best
Scott
Best
Scott
Hi Scot
You mentioned that you have measured
TS datas (more accueate then manufacturer noted...)
of Lowther PM6C, provided by mr Martin
Can You post the TS datas
I am interested in same model...
You mentioned that you have measured
TS datas (more accueate then manufacturer noted...)
of Lowther PM6C, provided by mr Martin
Can You post the TS datas
I am interested in same model...
PM6C (brand new)
fs = 57.1 Hz
Re = 6.8 ohms
Qes = 0.37
Qms = 2.89
Qts = 0.33
Vas = 50.3 liters
BL = 7.76
SPL (1w 1m) = 95.8 dB
PM2C (brand new)
fs = 65.4 Hz
Re = 6.9 ohms
Qes = 0.31
Qms = 2.96
Qts = 0.28
Vas = 38.1 liters
BL = 9.13
SPL (1w 1m) = 97.2 dB
Martin also notes that in his experience the T/S parameters of Lowther drivers do not change with break-in, but the C series are really nice drivers.
Best
Scott
fs = 57.1 Hz
Re = 6.8 ohms
Qes = 0.37
Qms = 2.89
Qts = 0.33
Vas = 50.3 liters
BL = 7.76
SPL (1w 1m) = 95.8 dB
PM2C (brand new)
fs = 65.4 Hz
Re = 6.9 ohms
Qes = 0.31
Qms = 2.96
Qts = 0.28
Vas = 38.1 liters
BL = 9.13
SPL (1w 1m) = 97.2 dB
Martin also notes that in his experience the T/S parameters of Lowther drivers do not change with break-in, but the C series are really nice drivers.
Best
Scott
OT, but amusing nonetheless: there is actually a term for this, coined by some jesuitically trained lawyers in new york -- "logo-rhea"GM said:
OT related, I sometimes suffer from 'dysflexia', the tendency ot interchange cahracters when typing.
I have a similar problem, but it's usually related to a bottle of something mellow and red... ;-)
Hi...
Scott
Thank You very much for Lowther TS
*
By the way I have long experience with MJK sheets
I think that the software is the etraordinarry for
Voigt pipes design...
I rearrange (interface mostly) of TL-sectios for use to design
the folded Viogt Pipes, and added Hyperbolic-Exponential flare to
Back Loaded Horn sheet...
I send those sheets to mr. MJ King last summer...
*
You can look at some projects in gallery at MJK site.
Scott
Thank You very much for Lowther TS
*
By the way I have long experience with MJK sheets
I think that the software is the etraordinarry for
Voigt pipes design...
I rearrange (interface mostly) of TL-sectios for use to design
the folded Viogt Pipes, and added Hyperbolic-Exponential flare to
Back Loaded Horn sheet...
I send those sheets to mr. MJ King last summer...
*
You can look at some projects in gallery at MJK site.
I've just been informed by Martin that Part 2 of the sheet I'm currently running, although optimised for rectangular baffles, can also provide a good approximation of the baffle-step response of a driver mounted on a trapezoidal baffle, like his own ML TQWT design. Oh happy days...
A few observations to come over the next day or two on driver and port postions since I've been trying out some of Martin and Greg's suggestions / comments.
Zoran -I take it those neat Dynaudio based jobs and that RCA monster are yours then? Very impressive indeed!
Cheers
Scott
A few observations to come over the next day or two on driver and port postions since I've been trying out some of Martin and Greg's suggestions / comments.
Zoran -I take it those neat Dynaudio based jobs and that RCA monster are yours then? Very impressive indeed!
Cheers
Scott
Scottmoose said:
Monster RCA... Olsen's baby?
Are you seeing those on Zoran's site? (i'm 3 browsers deep and i can't find anything that works with it)
dave
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