Greetings to all. I'm looking for advise from those that have modified these particular drivers if possible.
I have 2 pair of these drivers, plan to leave one pair stock and modify the other to compare how much can be done to improve their sound. Will be using them as a stand alone speaker system in 2ch up to moderate music levels, no sub ( but avail ), no tweeter ( although I do have a pair of Optimus Linaeum ET-6 tweeters @ my disposal).Mind you I have no test equipment, and a no to low budget to work with. I have the drivers plus 2 full sheets of 3/4" particle board, screws, glue, polyfill etc. to work with.
With that being said, how would one go about the simplest approach to achieve the best results possible? As to the drivers themselves ; Remove dust cap and replace with a phase plug, keep or remove whizzer cone, dampen basket, perhaps dampen the cone ( dope, felt ) etc.
Type of cabinets; sealed, ported or other? No open baffles or bookshelf type please. My limit size wise would be something along the lines of 36"h x 12"w x 12" d. Livingoom is 13' x 16' w/9' ceilings.
I do not expect audiophile grade results from these , just a nice, reasonably smooth sound. Any/all suggestions would be greatly appreciated as this would be better than shooting in the dark with my lack of experience and components/materials I have to work with.
Thank you.
I have 2 pair of these drivers, plan to leave one pair stock and modify the other to compare how much can be done to improve their sound. Will be using them as a stand alone speaker system in 2ch up to moderate music levels, no sub ( but avail ), no tweeter ( although I do have a pair of Optimus Linaeum ET-6 tweeters @ my disposal).Mind you I have no test equipment, and a no to low budget to work with. I have the drivers plus 2 full sheets of 3/4" particle board, screws, glue, polyfill etc. to work with.
With that being said, how would one go about the simplest approach to achieve the best results possible? As to the drivers themselves ; Remove dust cap and replace with a phase plug, keep or remove whizzer cone, dampen basket, perhaps dampen the cone ( dope, felt ) etc.
Type of cabinets; sealed, ported or other? No open baffles or bookshelf type please. My limit size wise would be something along the lines of 36"h x 12"w x 12" d. Livingoom is 13' x 16' w/9' ceilings.
I do not expect audiophile grade results from these , just a nice, reasonably smooth sound. Any/all suggestions would be greatly appreciated as this would be better than shooting in the dark with my lack of experience and components/materials I have to work with.
Thank you.
GRS 8FR-8 Full-Range 8" Speaker Pioneer Type B20FU20-51FW
I think these are the so-called “replacement” for the discontinued Pioneer BOFU (B20FU20-51FW) driver.
This driver was made famous in the hugely successful BIB thread. You can always make those but they are big as the name implies.
If you want to play with driver tweaks, and compare with stock. Keep it simple - plain old bass reflex is fine. PE’s listing says about 1.75 cu ft tuned for 43 Hz. A box that is internal 1.75 cu ft is probably about 2.34 cu ft externally if using 3/4in thick material so it’s still a substantial size cabinet.
Use a simulator to calculate the vent length for circa 43Hz. Probably 2.5in dia vent.
I think these are the so-called “replacement” for the discontinued Pioneer BOFU (B20FU20-51FW) driver.
This driver was made famous in the hugely successful BIB thread. You can always make those but they are big as the name implies.
If you want to play with driver tweaks, and compare with stock. Keep it simple - plain old bass reflex is fine. PE’s listing says about 1.75 cu ft tuned for 43 Hz. A box that is internal 1.75 cu ft is probably about 2.34 cu ft externally if using 3/4in thick material so it’s still a substantial size cabinet.
Use a simulator to calculate the vent length for circa 43Hz. Probably 2.5in dia vent.
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Thank you for the reply.
I just took a look on the PE site @ the recommended ported tower design for this driver is 36"×10"×10" w/ 3 3/4"d x 7 5/8" l port. No information of material thickness or placement of driver and port on the baffle.
Any suggestions on placement and can the port face to the rear?
I just took a look on the PE site @ the recommended ported tower design for this driver is 36"×10"×10" w/ 3 3/4"d x 7 5/8" l port. No information of material thickness or placement of driver and port on the baffle.
Any suggestions on placement and can the port face to the rear?
Greets!
Measured specs are way different than published plus can be way different from driver to driver, though one thing in common is that ideally it needs a much larger vented cab than you have room for, so short of measuring them and/or using them sealed, will need some sort of semi-aperiodic venting to smooth it out: 8" GRS 8FR-8 Full-Range Drivers - need help with 48" cabinet design! -Techtalk Speaker Building, Audio, Video Discussion Forum
GM
Measured specs are way different than published plus can be way different from driver to driver, though one thing in common is that ideally it needs a much larger vented cab than you have room for, so short of measuring them and/or using them sealed, will need some sort of semi-aperiodic venting to smooth it out: 8" GRS 8FR-8 Full-Range Drivers - need help with 48" cabinet design! -Techtalk Speaker Building, Audio, Video Discussion Forum
GM
Unless otherwise specified, dims are normally i.d. [inside].
High aspect ratio cabs should have the driver, vent at an odd pipe harmonic, i.e. from top [i.d.]*0.21, 0.349, 0.424, 0.698, 0.848 on down to the bottom for the vent being the most common, so with a short floor- stander, 0.21 is most common, though 0.349, 0.424 yielding the smoothest response with the least amount of stuffing, but considering this driver's specs you'll probably need a significant amount regardless.
GM
GM, thank you for your input and links provided.
As you mentioned manufacturers published t/s parameters compaired to actual/tested data is sufficiently different. Cab recommendation mentioned above is from PE. Not clear if this was derived from manufacturers specs.
Apparently my original thinking of cabinet plans have changed albeit not by much and in full undersanding that it is not an optimal choice. Moving a few thing around the living room the largest floorstander that can be used in my case is 37"h x 12"w x 16"d external, yielding internal volume of approximately 2.74 cu ft., not taking into consideration for a double front baffle running 24" in length, one window brace intersecting @ bottom of double baffle, and of couse the driver. Cabinets can be placed up against the wall and spaced11 ft apart.
I was not set as to what type of enclosure I wanted to build from the onset, just no bookshelves or ob. If this requires a sealed cabinet due to my limited size requirements so be it. Lol.
I do have 4 lbs of polyfill @ my disposal, perhaps fill upper 2/3 of cabinet and possibly try a ported configuration? Again as stated in my original post I do have a sub and tweeters that can be used to round out the overall sound.
I do apologize for my lack of knowledge therefore giving little information for anyone to make any solid recommendations but again any and all input is appreciated.
As you mentioned manufacturers published t/s parameters compaired to actual/tested data is sufficiently different. Cab recommendation mentioned above is from PE. Not clear if this was derived from manufacturers specs.
Apparently my original thinking of cabinet plans have changed albeit not by much and in full undersanding that it is not an optimal choice. Moving a few thing around the living room the largest floorstander that can be used in my case is 37"h x 12"w x 16"d external, yielding internal volume of approximately 2.74 cu ft., not taking into consideration for a double front baffle running 24" in length, one window brace intersecting @ bottom of double baffle, and of couse the driver. Cabinets can be placed up against the wall and spaced11 ft apart.
I was not set as to what type of enclosure I wanted to build from the onset, just no bookshelves or ob. If this requires a sealed cabinet due to my limited size requirements so be it. Lol.
I do have 4 lbs of polyfill @ my disposal, perhaps fill upper 2/3 of cabinet and possibly try a ported configuration? Again as stated in my original post I do have a sub and tweeters that can be used to round out the overall sound.
I do apologize for my lack of knowledge therefore giving little information for anyone to make any solid recommendations but again any and all input is appreciated.
You're welcome!
Those cabs are for the Pioneer, though in doing a simple 'classic' reflex [vented] alignment for it loaded with the 8FR there's no difference that additional stuffing can't overcome except in group delay where it 'rings like a 10 penny nail struck with a ball peen hammer', so the vent would ideally need stuffing too, reducing deep bass response of course and the bigger the cab to regain it/offset its higher Qts the worse it will perform overall in comparison unless more heavily damped.
In short, go for the tower/MLTL tuned to < 40 Hz for an 80 Hz XO and stuff to 'taste' all the way to the bottom if need be.
Also, better to brace using vertical board risers on edge with horizontal boards on edge or closet rod to tie them together rather than the airflow restrictive 'window pane' or similar bracing schemes to maximize any damping on the vent from the tower's 1/4 WL TL pipe action.
GM
Those cabs are for the Pioneer, though in doing a simple 'classic' reflex [vented] alignment for it loaded with the 8FR there's no difference that additional stuffing can't overcome except in group delay where it 'rings like a 10 penny nail struck with a ball peen hammer', so the vent would ideally need stuffing too, reducing deep bass response of course and the bigger the cab to regain it/offset its higher Qts the worse it will perform overall in comparison unless more heavily damped.
In short, go for the tower/MLTL tuned to < 40 Hz for an 80 Hz XO and stuff to 'taste' all the way to the bottom if need be.
Also, better to brace using vertical board risers on edge with horizontal boards on edge or closet rod to tie them together rather than the airflow restrictive 'window pane' or similar bracing schemes to maximize any damping on the vent from the tower's 1/4 WL TL pipe action.
GM
Dave, thank you for the info and attached pic. As posted above I was looking to perform various treatments and compare to some stock drivers.
I would imagine the pattern and placement of treatment is optimal to it's performance? To say one should strictly adhere to the above? I understand the GRS is not the same driver ( Pioneer ) but close enough in these areas of the cone/whizzer that breakup as to not freelance too much?
Regarding phase plugs had you tried different shapes ( bulb/mushroom/other) before keeping the bullet shape ?
I do realize my drivers are of the entry leve type and can only expect so much. Just looking to get a baseline if possible. Any insight from your vast experience would be greatly appreciated.
Again thank you for the info and pic (truely worth a thousand words)
I would imagine the pattern and placement of treatment is optimal to it's performance? To say one should strictly adhere to the above? I understand the GRS is not the same driver ( Pioneer ) but close enough in these areas of the cone/whizzer that breakup as to not freelance too much?
Regarding phase plugs had you tried different shapes ( bulb/mushroom/other) before keeping the bullet shape ?
I do realize my drivers are of the entry leve type and can only expect so much. Just looking to get a baseline if possible. Any insight from your vast experience would be greatly appreciated.
Again thank you for the info and pic (truely worth a thousand words)
I have not played with a lot of shapes for phase plugs. IIRC the BOFU used the Visaton B200 plugs. Cone was puzzlecoated, then EnABLed. Whizzers got a GM massage. Baskets duct-sealed. Maybe, cotton felt on the inside of the basket legs.
I did them a long time ago, EnABL2 might (likely) move the ring placement.
dave
I did them a long time ago, EnABL2 might (likely) move the ring placement.
dave
From a 2000? write up of a RS 40-1354 vented tower system [aka MLTL nowadays]:
"Radio Shack 40-1354 modded by trimming off the gasket flush with the metal frame lip, 3/4" thick polyfil stuffed between cone/whizzer and held in place with a rubber band, epoxied magnet assembly to the frame, added a foil star to the center of the dustcap (much good natured wise-cracking over this), damped the frame with gutter/drain/roof foil backed repair tape, used resilient caulk to install 3/4" polyfil squares to the inside of the frame legs, and added thinned rubber cement on bell lip of the whizzer after softening them with my fingers."
GM
Happy Christmas Eve all.
I could not get to starting the cabs this weekend so I decided to start working on the drivers. In my haste to start SOMETHING on these I inadvertently cut a whizzer off. So I decided to repeat my mistake on the other. Lol. Then I attacked the dustcaps.
So not having a clue as to Modpodge/water mix I tested on a sheet of poster board. I ended up with a 4:1 solution that did not distort my test sample.
I could not get to starting the cabs this weekend so I decided to start working on the drivers. In my haste to start SOMETHING on these I inadvertently cut a whizzer off. So I decided to repeat my mistake on the other. Lol. Then I attacked the dustcaps.
So not having a clue as to Modpodge/water mix I tested on a sheet of poster board. I ended up with a 4:1 solution that did not distort my test sample.
Working on the phaseplugs. I already cut 1/2" of its length and inserted wooden dowel inside. I need to increase dia so as to leave a smaller concentric gap to the voice coil. Attatch washer and paint. PVC pieces parts (that's all I have to work with)
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