Have here a nice and cheap pair of GRS 8FR-8 drivers and like to put them in a simple cabinet.
Data sheet GRS 8FR-8:
Resonant frequency fS 39 Hz
Electrical Q QES 0.46
Mechanical Q QMS 2.94
Total Q factor QTS 0.40
Suspension equivalent air volume VAS 64 litres
DC resistance RE 7.02 Ω
Voice coil inductance LE 1.28 mH
Maximum linear excursion Xmax ± 3 mm
Efficiency η₀ 0.81 %
Efficiency bandwidth product EBP 84
Overall diameter 203.2 mm
Baffle hole diameter 184.1 mm
Mounting depth 98.4 mm
Diaphragm material Paper
Voice coil diameter 38.1 mm
Magnet Ferrite
Proposal:
Data sheet GRS 8FR-8:
Resonant frequency fS 39 Hz
Electrical Q QES 0.46
Mechanical Q QMS 2.94
Total Q factor QTS 0.40
Suspension equivalent air volume VAS 64 litres
DC resistance RE 7.02 Ω
Voice coil inductance LE 1.28 mH
Maximum linear excursion Xmax ± 3 mm
Efficiency η₀ 0.81 %
Efficiency bandwidth product EBP 84
Overall diameter 203.2 mm
Baffle hole diameter 184.1 mm
Mounting depth 98.4 mm
Diaphragm material Paper
Voice coil diameter 38.1 mm
Magnet Ferrite
Proposal:
Attachments
You have the bracing running the less optimum direction.
And given the aspect ratio of the box it will be an ML-TL, not a reflex, which means the sim is not accurate.
dave
And given the aspect ratio of the box it will be an ML-TL, not a reflex, which means the sim is not accurate.
dave
Hi dave,
Can you please explain your comment?
Please indicate what you think is optimal. 😉
Comment on the concept drawing with the correct dimensions what is going on in your brain.
Thank you.
Can you please explain your comment?
Please indicate what you think is optimal. 😉
Comment on the concept drawing with the correct dimensions what is going on in your brain.
Thank you.
Guidline 1: braces should be placed such that the subpanels created by the brace should have an aspect ratio larger than the panelbeing braced.
This is clearly not the case in your design, where the aspect ratios are all less. You want to push resonances up in frequency where they will be less likely to get excited.
A reflex box is assummed to be “close" to a cube. As one dimension grows a quarter-wave resonance starts across the longest dimension. Your box is tall enuff vrs width/depth that it will be an ML-TL. The end-loaded driver and vent will maximize the quarter-wave effect.
dave
This is clearly not the case in your design, where the aspect ratios are all less. You want to push resonances up in frequency where they will be less likely to get excited.
A reflex box is assummed to be “close" to a cube. As one dimension grows a quarter-wave resonance starts across the longest dimension. Your box is tall enuff vrs width/depth that it will be an ML-TL. The end-loaded driver and vent will maximize the quarter-wave effect.
dave
Hi dave,
Can you please explain your comment?
Please indicate what you think is optimal. 😉
Comment on the concept drawing with the correct dimensions what is going on in your brain.
Thank you.
Can you please explain your comment?
Please indicate what you think is optimal. 😉
Comment on the concept drawing with the correct dimensions what is going on in your brain.
Thank you.
The braces should run vertically. I also take the opportunity to brace the driver/baffle against teh back of the box as well as top and bottom. Braces runnign parallel to the baffle should truncate such that they are not directly behind the driver.
And if you want to model the box you need to use a proper modeler that will handle quarter-wave designs.
dave
And if you want to model the box you need to use a proper modeler that will handle quarter-wave designs.
dave
Vertical braces are unnecessary for this driver.
The grain of the side panels runs vertically.
Don't worry mate. 😉
The grain of the side panels runs vertically.
Don't worry mate. 😉
What? That has little to do with it. And if you are using quality plywood (recommended) each ply has the grain running 90° to the ones next to it.
Grain implies solid wood, something i do not recommend if you do not know what you are doing. Still has little impact on the most effective bracing.
dave
Grain implies solid wood, something i do not recommend if you do not know what you are doing. Still has little impact on the most effective bracing.
dave
Last edited:
Typing, not spelling. I took Grade 11 Math instead of typing 10 — at the time the rationale wa sthat i would not have to use a typewriter. Boy was i wrong.
dave
dave
Take a look at some of the enclosure designs posted in the libraries below that Dave and Scott Lindgren have accumulated over the past couple of decades, many of which I’ve built myself. They should give you a better visualization of the bracing topology he’s suggesting.
http://frugal-phile.com/
http://www.wodendesign.com/Free.html
edit, actually it just occurred to me that many of Scott’s drawings lack the specific bracing details, but IIRC make reference to including such.
http://frugal-phile.com/
http://www.wodendesign.com/Free.html
edit, actually it just occurred to me that many of Scott’s drawings lack the specific bracing details, but IIRC make reference to including such.
A reasonable example to illustrate from the A26ReViz planset (https://www.diyaudio.com/community/threads/seas-a26-devore-style-build.369124/)
dave
dave
'Birds of a feather'! My mom made it plain to me and all concerned that no son of hers would ever be a secretary! So continued along a 'jack o'trades, master of none' career only to wind up in an engineering position that required copious written docs of various types to be typed by the secretarial pool and later do it all myself on a computer system, though with all that came before being eventually uploaded, so all I had to do was 'tailor' it to the current project.
