#1. Be prepared to test the polyfill (looks like a lot to me, but is also a "giant" speaker). After all is not a sealed speaker, let it breathe. Adjust for the right amount. Overall it looks good to me. The objective is for the reflections of the sound not coming out of the port or through the woofer membrane. Should be used with the low-pass (sub crossover) of the plate amp anyway... note: some people (in the manufacture) have more experience with that than me. You can look at some experiences. What you are trying here is REDUCING Panel Vibration and not building a 2/3-Way.
Cabinet-damping
Loudspeaker construction
#2. Step response looks ok, but I don't know (from the top of my head what is (/yours) "minimum". Of course sealed (#6 Closed box) is better and a large BR has a nasty one (look at #1 Bass reflex Chebyshev). Your looks like a Bass reflex Butterworth or Optimal (Keibs) more like #2 or #3. You can notice a good rapport from 30/40ms, the driver is neutral and returns to it's neutral position.
Picture from pdf ""On the dimensioning of bass-reflex enclosures -- 1966_7_3_007-022""
#3. The design looks good with me. Usually with long ports you help with the bracing for support in the other end, from the baffle.
What ports are you using? I don't know?!
From the drawing:
If using 2x ports 2.75in = 7cm, length is 33.5cm = 13.189in (14-18" in the references)
If using 2x ports 3.6in = 9.1cm length is 59.5cm = 23.425in
This is about an efficient way of losing my time since you don't give any references for your ports internal diameter... 😀 😀
(Note: calculations for 102.7 L@24.0 Hz)
Another note, from post#7, with 200W the bigger diameter port is better (be careful the driver max is 160 watts), and you mentioned the low pass variable from 40 Hz to 150 Hz.
Cabinet-damping
Loudspeaker construction
#2. Step response looks ok, but I don't know (from the top of my head what is (/yours) "minimum". Of course sealed (#6 Closed box) is better and a large BR has a nasty one (look at #1 Bass reflex Chebyshev). Your looks like a Bass reflex Butterworth or Optimal (Keibs) more like #2 or #3. You can notice a good rapport from 30/40ms, the driver is neutral and returns to it's neutral position.
Picture from pdf ""On the dimensioning of bass-reflex enclosures -- 1966_7_3_007-022""
#3. The design looks good with me. Usually with long ports you help with the bracing for support in the other end, from the baffle.
What ports are you using? I don't know?!
From the drawing:
If using 2x ports 2.75in = 7cm, length is 33.5cm = 13.189in (14-18" in the references)
If using 2x ports 3.6in = 9.1cm length is 59.5cm = 23.425in
This is about an efficient way of losing my time since you don't give any references for your ports internal diameter... 😀 😀
(Note: calculations for 102.7 L@24.0 Hz)
Another note, from post#7, with 200W the bigger diameter port is better (be careful the driver max is 160 watts), and you mentioned the low pass variable from 40 Hz to 150 Hz.
Attachments
Last edited:
Hi Inductor,
thanks for the inputs.
1: I will incorporate suggestions given in the link (Troels) for cabinet damping. I will also try to get more info on cabinet damping of subs from internet,as i still have sufficient time until construction begins.
2:yep I didnt know the info on step resp. thanks for the info. My design does look optimal and within standard acceptable designs for a typical BR.
3. I will be using 2x2.75" internal dia ports(mentioned in drawing). the reason i kept the length from 14-18 inches as of now is to try with different lengths until i get best tuning at the time of construction( based on your earlier suggestion in post #14 😉 .
thanks for the inputs.
1: I will incorporate suggestions given in the link (Troels) for cabinet damping. I will also try to get more info on cabinet damping of subs from internet,as i still have sufficient time until construction begins.
2:yep I didnt know the info on step resp. thanks for the info. My design does look optimal and within standard acceptable designs for a typical BR.
3. I will be using 2x2.75" internal dia ports(mentioned in drawing). the reason i kept the length from 14-18 inches as of now is to try with different lengths until i get best tuning at the time of construction( based on your earlier suggestion in post #14 😉 .
regarding your notes,
the amp does have variable crossover from 40 hz to 150 hz. and regarding power, i will not using more than 50W anyway. I dare not as my wife/ neighbors will kill me.😉
regards
prasi
the amp does have variable crossover from 40 hz to 150 hz. and regarding power, i will not using more than 50W anyway. I dare not as my wife/ neighbors will kill me.😉
regards
prasi
Then you can use the smaller ports.
Regarding the 18" length ports, they don't fit in the 18" deep enclosures unless you make that dimension longer (Section A-A, Section B-B). Space also for the: "" For the internal insulation, I am planning to cover the internal walls with just one layer of 6 mm thick felt material ""
yep you are right , 18" long straight port wont fit inside the enclosure. but if i use 90 deg. bend after say about 12" , then they will. The rule of thumb, as I understand, is to keep any openings of port atleast a diameter away from walls.
Also pl have a look at the following link.
vent tuning
It says the actual port length required to achieve a given tuning frequency is always lower than that suggested by calculations.Phew!!
Also pl have a look at the following link.
vent tuning
It says the actual port length required to achieve a given tuning frequency is always lower than that suggested by calculations.Phew!!
Hi Prasi, as requested I've had a look. I think what you have is a good balance. They will play low, have a nice gentle rolloff, look like they will handle your 40W target with no problem and also have a good step response for a speaker that is tuned this low.
I put your figures into unibox. I might tend to go for a slightly higher tuning freq of 25Hz (all other things remaining as you have them) but there is very little difference in reality. Slightly flatter with slightly lower F3 (but with ultimately steeper rollof) and possibly slightly better step response (though it is marginal).
The tradeoff is that the point where the driver excursion starts to increase rapidly is slightly higher.
Are you going to use the correction factor (as per Troels site) for the port length? I believe you took that into consideration with your first speaker from memory.
I've attached the spl comparison to show that there is really very little difference 🙂
Tony.
I put your figures into unibox. I might tend to go for a slightly higher tuning freq of 25Hz (all other things remaining as you have them) but there is very little difference in reality. Slightly flatter with slightly lower F3 (but with ultimately steeper rollof) and possibly slightly better step response (though it is marginal).
The tradeoff is that the point where the driver excursion starts to increase rapidly is slightly higher.
Are you going to use the correction factor (as per Troels site) for the port length? I believe you took that into consideration with your first speaker from memory.
I've attached the spl comparison to show that there is really very little difference 🙂
Tony.
Attachments
Hi Tony, thanks for the inputs.
regarding tuning, this time, I will tune with different lengths of port tube and then finalize the tuning based on actual bass response at site. I have not considered room gain effects as of now but somewhere I read that for most home environments, the room gain starts at about 1dB at 30 Hz upto about 7-9dB at 20 Hz. If we assume this as correct, then I might get flat frequency response down to 20 Hz at room conditions;-) (There is nothing wrong in dreaming, is there?).
The only issue with 25Hz tuning as you said is peak cone excursion will exceed the limit at lower frequencies (near 20Hz) and also there is a slight bump in dB of 0.49, which again can easily be neglected.
So to summarize, final tuning @ site, because it will be used at that place for life (sub's life not mine 🙂.
Regarding Troels correction factor, I will do that this time also. and hopefully it is applicable here also. But as said above, the tuning will start with theoretical port tube length and upto troels findings.
regards prasi
regarding tuning, this time, I will tune with different lengths of port tube and then finalize the tuning based on actual bass response at site. I have not considered room gain effects as of now but somewhere I read that for most home environments, the room gain starts at about 1dB at 30 Hz upto about 7-9dB at 20 Hz. If we assume this as correct, then I might get flat frequency response down to 20 Hz at room conditions;-) (There is nothing wrong in dreaming, is there?).
The only issue with 25Hz tuning as you said is peak cone excursion will exceed the limit at lower frequencies (near 20Hz) and also there is a slight bump in dB of 0.49, which again can easily be neglected.
So to summarize, final tuning @ site, because it will be used at that place for life (sub's life not mine 🙂.
Regarding Troels correction factor, I will do that this time also. and hopefully it is applicable here also. But as said above, the tuning will start with theoretical port tube length and upto troels findings.
regards prasi
Hi Tony,
Eureka!! Another find!!.
The seas subwoofer kit available at madisound is considered to be one of the best for home. here is the link. The Madisound Speaker Store and the link to enclosure design is here http://www.madisound.com/loudspeaker_specifications/L26ROY_SUBKIT_PORT.pdf
I did sim in unibox for this kit and it turned out be closely matching with kit specs, wrt F3 (use box Ql of 6). the only difference being the port tube length suggested by seas is 9.2inch length against unibox calculated 12.72". Guess what the ratio of actual versus calculated is 0.73. This means, the Troels findings are being used by OEMS,seasa atleast.
Eureka!! Another find!!.
The seas subwoofer kit available at madisound is considered to be one of the best for home. here is the link. The Madisound Speaker Store and the link to enclosure design is here http://www.madisound.com/loudspeaker_specifications/L26ROY_SUBKIT_PORT.pdf
I did sim in unibox for this kit and it turned out be closely matching with kit specs, wrt F3 (use box Ql of 6). the only difference being the port tube length suggested by seas is 9.2inch length against unibox calculated 12.72". Guess what the ratio of actual versus calculated is 0.73. This means, the Troels findings are being used by OEMS,seasa atleast.
Hi all,
can somebody answer me this... How low a subwoofer should go (in Hz) in a typical Hi-Fi home set up before it starts to sound overwhelmingly boomy? Somewhere I had read that the typical room gain is about 1 dB at 30 Hz and goes upto 8-9 dB at 20Hz.
I did a sim in the wooferbox and circuit designer with dayton SPA 250 plate amp and Although my box alone F3 is 25Hz, with a second order high pass filter centered at 20Hz of the plate amp, the new system F3 is nearly 29Hz. will this system be ok for the home use considering the room gain?
reg
prashant
can somebody answer me this... How low a subwoofer should go (in Hz) in a typical Hi-Fi home set up before it starts to sound overwhelmingly boomy? Somewhere I had read that the typical room gain is about 1 dB at 30 Hz and goes upto 8-9 dB at 20Hz.
I did a sim in the wooferbox and circuit designer with dayton SPA 250 plate amp and Although my box alone F3 is 25Hz, with a second order high pass filter centered at 20Hz of the plate amp, the new system F3 is nearly 29Hz. will this system be ok for the home use considering the room gain?
reg
prashant
Hi Tony,
I am also exploring the option of using following driver for my sub project. I have done the sim for both in unibox and they are quite close. I just wanted to have your opinion on which driver is more suitable.
Model: Dayton Audio SD315A-88
URL: Dayton Audio SD315A-88 12" DVC Subwoofer
For reference, my current design is based on the following driver.
Model: Dayton Audio SD270A-88
URL: http://www.daytonaudio.com/index.php/sd270a-88-10-dvc-subwoofer.html
regards
prashant
I am also exploring the option of using following driver for my sub project. I have done the sim for both in unibox and they are quite close. I just wanted to have your opinion on which driver is more suitable.
Model: Dayton Audio SD315A-88
URL: Dayton Audio SD315A-88 12" DVC Subwoofer
For reference, my current design is based on the following driver.
Model: Dayton Audio SD270A-88
URL: http://www.daytonaudio.com/index.php/sd270a-88-10-dvc-subwoofer.html
regards
prashant
Hi Tony,
I am also exploring the option of using following driver for my sub project. I have done the sim for both in unibox and they are quite close. I just wanted to have your opinion on which driver is more suitable.
Model: Dayton Audio SD315A-88
URL: Dayton Audio SD315A-88 12" DVC Subwoofer
For reference, my current design is based on the following driver.
Model: Dayton Audio SD270A-88
URL: Dayton Audio SD270A-88 10" DVC Subwoofer
regards
prashant
I am also exploring the option of using following driver for my sub project. I have done the sim for both in unibox and they are quite close. I just wanted to have your opinion on which driver is more suitable.
Model: Dayton Audio SD315A-88
URL: Dayton Audio SD315A-88 12" DVC Subwoofer
For reference, my current design is based on the following driver.
Model: Dayton Audio SD270A-88
URL: Dayton Audio SD270A-88 10" DVC Subwoofer
regards
prashant
Depends...
Depends on the room dimensions, I have had my 15" DVC in storage for five years as it is too much for my small living room. The two 8" in my main system are more than adequate. Low tuned subs do not sound boomy but can make everything in the house that is not nailed down rattle.
Depends on the room dimensions, I have had my 15" DVC in storage for five years as it is too much for my small living room. The two 8" in my main system are more than adequate. Low tuned subs do not sound boomy but can make everything in the house that is not nailed down rattle.
Thanks a lot... I guess it would be ok for my room. if things start rattling, I will turn the sub off..
Hi Prasi, as I said I'm not really experienced with subs. A quick look at the specs tells me that the 12" is a higher efficiency unit, but that it doesn't look like it will go as low.
My old three ways had 12" high efficiency drivers in them, but I changed them out for 10" vifa W26WR-09-08's which were quite a bit less efficient, but the improvement was quite large.
I've recently done some measurements (to aid in integrating with my MTM's) of those three ways bass response and it is actually quite awful. Massive hole around 70Hz. It was my first "build" which used the existing (very poor) cabinets with a new baffle and ports. I did not know then what I know now about alignments. I tuned for low as I could get. F3 around 30Hz...
I need to make new cabinets for those drivers. I think in the right box they will sound very nice indeed.
Tony.
My old three ways had 12" high efficiency drivers in them, but I changed them out for 10" vifa W26WR-09-08's which were quite a bit less efficient, but the improvement was quite large.
I've recently done some measurements (to aid in integrating with my MTM's) of those three ways bass response and it is actually quite awful. Massive hole around 70Hz. It was my first "build" which used the existing (very poor) cabinets with a new baffle and ports. I did not know then what I know now about alignments. I tuned for low as I could get. F3 around 30Hz...
I need to make new cabinets for those drivers. I think in the right box they will sound very nice indeed.
Tony.
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