Cant find Skram here, but even then dont know how would compare with data from rcf and 139db peak which probably doesnt mean much.
All I know tts uses 2x LF18N401 with icepower 1000asp for each 18”.
I guess they are comparable with Skram playing flat much lower but would still hope for few dB to justify the upgrade.
All I know tts uses 2x LF18N401 with icepower 1000asp for each 18”.
I guess they are comparable with Skram playing flat much lower but would still hope for few dB to justify the upgrade.
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Even with it's lower Fb, the Skhorn should be ~+6dB over the RCFTTS28a due to its larger box ( 680L vz 425L), more power, Sd and Xmax.
These measurements are at 2 meters so add +6dB for a one meter equivalent:
That's close to one Skram = 2 RCFTTS28a.
The Skram is half the Skhorn (~340L), so probably around equal output to one RCFTTS28a, other than it's having far more 30 Hz output.
Art
https://freeloudspeakerplan.rf.gd/pages/skram.htm?i=1
The current size is the original model. Adjust as you want for your driver.
The current size is the original model. Adjust as you want for your driver.
Attachments
@LORDSANSUI
Thank you for sharing address and managing on your database.
I have two Skrams that I builded last year. I was very surprised by the sound and wanted to add more units in the future.
By the way , It's too heavy to carry and setup by one person , so I want to make a scaled down 18" version of Skram cause I have 4 18sound 18LW1400 8Ohm.
Of course, I agreed that bass reproduction would be compromised compared to the 21“ version, and after considering the ease of transport by one person and the outdoor water resistance, I decided that the 18” version would be easier to use.
(As an acoustic team, I would like to start working on a 21-inch version as soon as we have the warehouse and manpower to do so.)
So, I have two questions.
1. Can't import freeCAD files to hornresp
I watched your all videos on your site Tutorial and try to import freeCAD files to hornresp.
I ran Skram-hornresp.FCMacro and import that .txt files to hornresp, but the error says "~.txt is not a valid record."
Is there something wrong with my method?
2.Differences between my Acoustical Power and your photo's
I couldn't import freeCAD files , so I tried put the same paramators on your photo.
I got the Acoustical Power graph , but it is not the same as your photo graph.
Is there any difference settings about my hornresp?
3.Calculation Process
What should be the first calculation for a new redesign?
Bassreflex for that 18woofer? or Front loaded Horn?
Thank you for sharing address and managing on your database.
I have two Skrams that I builded last year. I was very surprised by the sound and wanted to add more units in the future.
By the way , It's too heavy to carry and setup by one person , so I want to make a scaled down 18" version of Skram cause I have 4 18sound 18LW1400 8Ohm.
Of course, I agreed that bass reproduction would be compromised compared to the 21“ version, and after considering the ease of transport by one person and the outdoor water resistance, I decided that the 18” version would be easier to use.
(As an acoustic team, I would like to start working on a 21-inch version as soon as we have the warehouse and manpower to do so.)
So, I have two questions.
1. Can't import freeCAD files to hornresp
I watched your all videos on your site Tutorial and try to import freeCAD files to hornresp.
I ran Skram-hornresp.FCMacro and import that .txt files to hornresp, but the error says "~.txt is not a valid record."
Is there something wrong with my method?
2.Differences between my Acoustical Power and your photo's
I couldn't import freeCAD files , so I tried put the same paramators on your photo.
I got the Acoustical Power graph , but it is not the same as your photo graph.
Is there any difference settings about my hornresp?
3.Calculation Process
What should be the first calculation for a new redesign?
Bassreflex for that 18woofer? or Front loaded Horn?
Attachments
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Hello woolwool,
If I'm not mistaken, David updated Hornresp file to be imported so I will take a look and update the macro for you if this is the reason for the invalid format error.
The photo I shared was published by the author of this design, if the inputs are the same the output should be too. Looks to your input data they are different.
Will check if there are incorrect definition in the model within this weekend and give you a reply.
You could try scaling the model multiplying the dimensions for a specific percentage like 0,85 (85%) and start to fine tune from there, maybe the aspect ratio can change to get the optimum response from the 18" driver.
Hello LORDSANSUI,
Thank you for quick replying!
I didn't know some changes for hornresp by Update.
Recently I updated it for 57.30ver. Maybe that is what cause error.
I'm appriciate for your kindness help to check it.
Thank you for quick replying!
I didn't know some changes for hornresp by Update.
Recently I updated it for 57.30ver. Maybe that is what cause error.
I'm appriciate for your kindness help to check it.
Thank you for an advising , I will try to rescale and check it!
Hello @woolwool
Find below some feedback that may help you.
Regarding why the inputdata I shared in the post #145 is not providing the same output: I can't fully answer this questions because the Ricci's website is not available anymore so couldn't double check if that image was the original one published by the design author nor if there was any changes in the data. It worth to mention that the "Lossy Inductance" feature was enabled in that simulation, you can confirm that looking into the variable Le that is green colored (newer hornresp versions = red colored). You could try to find the semi-inductance parameter for the driver B&C 21SW152-4 and run the simulation again to see you reach the same output. Read the link belwo for more information about semi-inductance parameters.
In addition, that Skran input looks strange and I would discard and not trust on it. See pag.1 from attached PDF presentation for detail.
In the pag.2 you can see how FreeCAD model was defined. The front horn has two parallel walls and one angled one, so the expansions are the same by math rule and in this case two segments is the best way to represent it in order to get good accuracy. All the other parameters are correct and the model is working properly.
Regarding box size in case of 21" driver, see below the comparison from that data I have from original Skram vs FreeCAD model:
Skram Dimensions: 24"x32"x36" (609.6mm x 812.8mm x 914.4mm)
FreeCAD Dimensions: 610mm x 813mm x 915mm
Take a look in the pag.3 to see a comparison of different simulations input and related output.
Regarding hornresp error while importing TXT file created by the macro, it's due to the Hornresp Update 5730-250309 and the end correction changes, See the link below for more information. Not all information are explicitly indicated by David once those posts are more like a summary.
Take a look in the pag.4 to get more detail about how the end correction changes affect the inport/expor txt file and how to fix the macro. You can change txt file directly or download updated macros from the attachment.
If you disable end correction from the port, once this is how the design is, you can find further improvement in the SPL response and improve model accuracy. See pag.5.
For others design changes and simulation accuracy improvement see pag.6
Find below some feedback that may help you.
Regarding why the inputdata I shared in the post #145 is not providing the same output: I can't fully answer this questions because the Ricci's website is not available anymore so couldn't double check if that image was the original one published by the design author nor if there was any changes in the data. It worth to mention that the "Lossy Inductance" feature was enabled in that simulation, you can confirm that looking into the variable Le that is green colored (newer hornresp versions = red colored). You could try to find the semi-inductance parameter for the driver B&C 21SW152-4 and run the simulation again to see you reach the same output. Read the link belwo for more information about semi-inductance parameters.
In addition, that Skran input looks strange and I would discard and not trust on it. See pag.1 from attached PDF presentation for detail.
In the pag.2 you can see how FreeCAD model was defined. The front horn has two parallel walls and one angled one, so the expansions are the same by math rule and in this case two segments is the best way to represent it in order to get good accuracy. All the other parameters are correct and the model is working properly.
Regarding box size in case of 21" driver, see below the comparison from that data I have from original Skram vs FreeCAD model:
Skram Dimensions: 24"x32"x36" (609.6mm x 812.8mm x 914.4mm)
FreeCAD Dimensions: 610mm x 813mm x 915mm
Take a look in the pag.3 to see a comparison of different simulations input and related output.
Regarding hornresp error while importing TXT file created by the macro, it's due to the Hornresp Update 5730-250309 and the end correction changes, See the link below for more information. Not all information are explicitly indicated by David once those posts are more like a summary.
Take a look in the pag.4 to get more detail about how the end correction changes affect the inport/expor txt file and how to fix the macro. You can change txt file directly or download updated macros from the attachment.
If you disable end correction from the port, once this is how the design is, you can find further improvement in the SPL response and improve model accuracy. See pag.5.
For others design changes and simulation accuracy improvement see pag.6
@LORDSANSUI
I'm very thankful for your kindly support.
I can open Hornresp files by freeCAD!
I would like to try to check SKRAM's parametors by following your guide.
Best regards , Have a good day!
I'm very thankful for your kindly support.
I can open Hornresp files by freeCAD!
I would like to try to check SKRAM's parametors by following your guide.
Best regards , Have a good day!