Hey everyone. So I just got done completely rebuilding my Carver Amazing speakers along with a pair of custom made 1k watt mono blocks to power them. They do sound absolutely amazing but do lack a little on the very bottom end. Plus, they are over 30 years old and finding the original 12” drivers in good condition is getting harder and harder.
My crazy idea is to build two towers the same height as my Amazings (66”) using four PE GSR 12SW-4HE in each tower, kinda like the old Infinity ISRs from back in the day. These drivers have a low FS, decent Xmax and are pretty cheap. I’d be powering them with a 2 X 850 watt amp. My goal here is to get as flat of a response as I can down to the lowest frequency possible.
I used WinISD and came up with a 15cft ported enclosure with the port tuned to 20hz. That give a flat response down to 21 hz or so without exceeding Xmax on the power I have. The port would be pretty big (16.75 X 5.5 X 32”) to keep port velocity down but size isn’t really a concern here.
Overall internal space with port, bracing and Wd would be almost 18cft.
So am I missing anything here and how do you think they would sound. These will be strictly two channel music subs. Open to feedback.
My crazy idea is to build two towers the same height as my Amazings (66”) using four PE GSR 12SW-4HE in each tower, kinda like the old Infinity ISRs from back in the day. These drivers have a low FS, decent Xmax and are pretty cheap. I’d be powering them with a 2 X 850 watt amp. My goal here is to get as flat of a response as I can down to the lowest frequency possible.
I used WinISD and came up with a 15cft ported enclosure with the port tuned to 20hz. That give a flat response down to 21 hz or so without exceeding Xmax on the power I have. The port would be pretty big (16.75 X 5.5 X 32”) to keep port velocity down but size isn’t really a concern here.
Overall internal space with port, bracing and Wd would be almost 18cft.
So am I missing anything here and how do you think they would sound. These will be strictly two channel music subs. Open to feedback.
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If you really need 18 cubic feet of sub.
And realize how big that is.
Just 2 of them with 100 watts is likely around 105 dB
So stereo pair would be 4 woofers.
Already overkill and will never see more than 70 or 140 watts.
Winisd wont calculate shared wall ports.
It will be too long, and the velocity goals probably
No where near 800 watts.
Correction factor for WinIsd is normal K= .732
and up too K=.850 for flarea = no shared walls.
Slot port has poor efficiency, shares 3 walls
K = 2.227
Winisd wont calculate it
Use a program that can adjust Correction factor
like Virtuix Cad. Will be way shorter
The port can be smaller, system will never see 850 watts.
Nobody runs 120 dB of 800 watts.
The main speakers I take wild guess dont do much more than max SPL 108 or 110 dB
at high distortion, and listening levels are more like 88 to 98.
Something 4 subs would do with 50 to 70 watts of actual real power.
And something 2 subs could do no problem or 2 on each side or 4x.
Would get louder than the main speakers easily.
Depending on the music, dont care to argue sub bass
is 30 Hz to 80 Hz and most of it is actually 40 Hz
when people think its " deep" 20 Hz
So 6 or 8 cubic feet is already overkill but more feasible max size.
With way less speaker. And would use just normal accurate flared round ports.
No junk triangle or slot ports.
Woofer Fs is around 22 to 27 Hz in real life. So reflex will be the same.
No matter how big the box is. Tune is the same. Climbs when they heat up.
So huge pretty transfer functions in WinIsd mean nothing in real room.
Drivers mounted above 29" height and big old floor and big old ceiling. Means the same
old huge 80 to 100 Hz dip that you get in room and a big old 50 to 60 Hz bloom.
that people swear is " 20 Hz"
I just build normal boxes and keep woofer low low low to the ground plane.
Not 33 or 54 inches in the air. And big old room response dip.
And realize how big that is.
Just 2 of them with 100 watts is likely around 105 dB
So stereo pair would be 4 woofers.
Already overkill and will never see more than 70 or 140 watts.
Winisd wont calculate shared wall ports.
It will be too long, and the velocity goals probably
No where near 800 watts.
Correction factor for WinIsd is normal K= .732
and up too K=.850 for flarea = no shared walls.
Slot port has poor efficiency, shares 3 walls
K = 2.227
Winisd wont calculate it
Use a program that can adjust Correction factor
like Virtuix Cad. Will be way shorter
The port can be smaller, system will never see 850 watts.
Nobody runs 120 dB of 800 watts.
The main speakers I take wild guess dont do much more than max SPL 108 or 110 dB
at high distortion, and listening levels are more like 88 to 98.
Something 4 subs would do with 50 to 70 watts of actual real power.
And something 2 subs could do no problem or 2 on each side or 4x.
Would get louder than the main speakers easily.
Depending on the music, dont care to argue sub bass
is 30 Hz to 80 Hz and most of it is actually 40 Hz
when people think its " deep" 20 Hz
So 6 or 8 cubic feet is already overkill but more feasible max size.
With way less speaker. And would use just normal accurate flared round ports.
No junk triangle or slot ports.
Woofer Fs is around 22 to 27 Hz in real life. So reflex will be the same.
No matter how big the box is. Tune is the same. Climbs when they heat up.
So huge pretty transfer functions in WinIsd mean nothing in real room.
Drivers mounted above 29" height and big old floor and big old ceiling. Means the same
old huge 80 to 100 Hz dip that you get in room and a big old 50 to 60 Hz bloom.
that people swear is " 20 Hz"
I just build normal boxes and keep woofer low low low to the ground plane.
Not 33 or 54 inches in the air. And big old room response dip.
Thank you for your response. Sorry it’s taken me so long to respond. I downloaded Virtuix Cad and have been playing with it as well.
Thank you for pointing out that shared walled ports are shorter in length. I honestly didn’t know that even though I have been building them for years doing car audio. I love learning new stuff about this hobby and in my case what I do for a living.
I know this project is a little over the top, but that’s kinda the fun of it, just to try it and see what happens.
Using the new software and tinkering a bit, I did get the air space included port, driver and bracing displacement down to about 13.25cft and would on paper still play flat down to 21hz with a 3dB boost at 20Hz and still keep port velocity and excursion within limits.
I’m 52 yo but still love some “spirited” listening, Im guessing more spirited than most, but not driving things into distortion. In my home theater my mains are a pair of highly modified Definitive Technology BP2000TLs on 1600 watts. They are capable of 120dB+ without any audible distortion or amps going into clipping.
As for my big Carvers, they are stupidly inefficient but they say they can do 113dB in stock form and my mono blocks are just a tad over 1100 watts a piece. Bob Carver recommends 1000 watts each. The crossovers are their weak link so I make new ones with bigger and better parts and that really helped. I will have to put a meter on them this weekend and see what they do.
Again, I know this is complete overkill, but to me that’s half the fun of it. Try something crazy and see how it works out. Thank you again for your input, it definitely helped!
Thank you for pointing out that shared walled ports are shorter in length. I honestly didn’t know that even though I have been building them for years doing car audio. I love learning new stuff about this hobby and in my case what I do for a living.
I know this project is a little over the top, but that’s kinda the fun of it, just to try it and see what happens.
Using the new software and tinkering a bit, I did get the air space included port, driver and bracing displacement down to about 13.25cft and would on paper still play flat down to 21hz with a 3dB boost at 20Hz and still keep port velocity and excursion within limits.
I’m 52 yo but still love some “spirited” listening, Im guessing more spirited than most, but not driving things into distortion. In my home theater my mains are a pair of highly modified Definitive Technology BP2000TLs on 1600 watts. They are capable of 120dB+ without any audible distortion or amps going into clipping.
As for my big Carvers, they are stupidly inefficient but they say they can do 113dB in stock form and my mono blocks are just a tad over 1100 watts a piece. Bob Carver recommends 1000 watts each. The crossovers are their weak link so I make new ones with bigger and better parts and that really helped. I will have to put a meter on them this weekend and see what they do.
Again, I know this is complete overkill, but to me that’s half the fun of it. Try something crazy and see how it works out. Thank you again for your input, it definitely helped!
Greets!
Vented net volume (Vb) (L) = 20*80.41*0.43^3.3 (Ft^3 = 99.26 L/~28.31685 = 3.505 ft^3
Vented box tuning (Fb) (Hz) = 0.42*22*0.43^-0.96 = 20.76 Hz
F3 (Hz) = 22*0.28*0.43^-1.4 = 20.1 Hz
Playing with these calcs in Hornresp with a 99.26*4 = 397 L/~28.31685 = 14 ft^3 = 64.5" i.d. x ~375"^2 i.d. tube with a single summed driver at the pipe's center I get a well stuffed (QL = 3) Xmax limited 400 W = ~120 dB/m/20 - 200 Hz where its high inductance rapidly rolls it off, so ignoring room gain add another ~6 dB/pair.
Unfortunately, it's full width duct vent area needs to be at least a 10" dia. area (506 cm^2/78.43"^2) to get vent mach down to ~ 18 ms/20 Hz which I can only approximate a length to begin experimenting with.
Vented net volume (Vb) (L) = 20*80.41*0.43^3.3 (Ft^3 = 99.26 L/~28.31685 = 3.505 ft^3
Vented box tuning (Fb) (Hz) = 0.42*22*0.43^-0.96 = 20.76 Hz
F3 (Hz) = 22*0.28*0.43^-1.4 = 20.1 Hz
Playing with these calcs in Hornresp with a 99.26*4 = 397 L/~28.31685 = 14 ft^3 = 64.5" i.d. x ~375"^2 i.d. tube with a single summed driver at the pipe's center I get a well stuffed (QL = 3) Xmax limited 400 W = ~120 dB/m/20 - 200 Hz where its high inductance rapidly rolls it off, so ignoring room gain add another ~6 dB/pair.
Unfortunately, it's full width duct vent area needs to be at least a 10" dia. area (506 cm^2/78.43"^2) to get vent mach down to ~ 18 ms/20 Hz which I can only approximate a length to begin experimenting with.
I have played around with those GRS 12SW-HE's and they are honestly not that good of a subwoofer. They have itty bitty 2" voice coils, and do not handle much power. I had one of them in my truck in a 1.5cf sealed box getting 250 watts and it developed a rattle after about a month of usage. They just don't sound good, either. I think something is going on in either the suspension or the motor that creates some distortion. Take a peek at my screenshot of the actual measurements I pulled from one, and you can see a lot of wobble on the impedance curve. I would not recommend these.
![GRS 12SW - 4HE specs comparison [measured vs published].PNG](/community/data/attachments/1126/1126327-2239734968a9540801797ff6ddc918c8.jpg?hash=IjlzSWipVA)