You're probably right about a total in room response masking GD in many situations. But if you happen to listen nearfield (say while setting up the sub) you could probably pick it out. And then you'd know it was there... gnawing at your mind every time a kick drum ... kicks.
I think I'm also biased against vented subs because all cheap subs are vented and most cheap subs have terrible resonances, boomy, peaky responses, and probably a ton of group delay too. I associate BR designs in general with all the bad ones I've heard over the years, which may not be totally fair.
I use two sealed 18” subs in wadded 140 L cabs . I run these from 8-39 Hz and can get a response within 3-4db using one PEQ at the room resonance, only the room is modest size 5m x 5m x 2.65m I can get 106 db at 10HZ at the seating position with less than 20% distortion and 110db only 2% at 20 HZ. I use 12” subs from 40-80, they do overlap. I have no issue with volume on music or film. A tonne of headroom as I can hit 115 db at the main seating position with less than 5% disortion at 20 Hz I am over 3m away from the two 18’s
I get the reflex SPL point but no need for me
I get the reflex SPL point but no need for me
Sealed vs vented: Once you apply filters and eq to achieve equal response, values like group delay and phase will also be equal or in some cases worse.
Sorry about the bump, image from the article and a copy as PDF, from Claus Futtrup who changed companies from Seas to Dali in 2021.
http://www.cfuttrup.com
http://www.cfuttrup.com
Davids post about the general guidelines in the vast hornresp thread:
https://www.diyaudio.com/community/goto/post?id=5459880
https://www.diyaudio.com/community/goto/post?id=5459880
The MLP is the main listening position so this is a measurement at the centre seating position at the low end it’s quite consistent across the sofa, less so for the 12” subs
The room has a node at 34 Hz
The room has a node at 34 Hz
Here is a look at the three seats and a number of positions where I think it sounds really good in the room. I run the subs to 70 Hz or so this is 2x18 and 3x12. The 18 have a 48db/Octave DSP filter at 39 Hz and the 3 x12" have a 24db/Octave DSP at 24 Hz roll on these are rolled off by the plate amp and not digitally
I ended up with a lift at 34 and a little down turn from 30>20. This was a preference by ear, I can clean up the 34 bump but it seems to lose a bit too much energy and drive if I lift the 18's and add more to the sub 20 Hz it sounds a bit too heavy. I am still experimenting with settings. Obviously I blend in the subs with each channel and filter out the unecessary added db. all bar the LFE channel are over 80 db. I have a harmon like curve where most channels have a 6db lift or more from 20-70 Hz
I ended up with a lift at 34 and a little down turn from 30>20. This was a preference by ear, I can clean up the 34 bump but it seems to lose a bit too much energy and drive if I lift the 18's and add more to the sub 20 Hz it sounds a bit too heavy. I am still experimenting with settings. Obviously I blend in the subs with each channel and filter out the unecessary added db. all bar the LFE channel are over 80 db. I have a harmon like curve where most channels have a 6db lift or more from 20-70 Hz
If you want to compare, my driver is a BMS 18N862 in a 140L internal sales cabinet. It was the best I could find when looking at a few few modelling sites and had a deserved great rep for low bass. 19 mm Xmax etc
I'm thinking of putting the tuning tube pointing towards the floor, in the spot available from removing the marble block. They are 25mm. free .
There has been a lot of talk about the correct position of the tuning tube, but since this box is a prism, I don't see another way to locate it, should I not risk that it does not "vent" enough and raise the feet a little more?
There has been a lot of talk about the correct position of the tuning tube, but since this box is a prism, I don't see another way to locate it, should I not risk that it does not "vent" enough and raise the feet a little more?
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No, this driver is what I got at the time and I will not change it. Thanks for the intention.
It remains to clarify some details before making the decision, mainly the location of the tuning tube. I promised WAF that I would make the protection grids for all the cabinets in the living room, and I still haven't delivered, so every time children come to visit my house, it gets difficult.....
For this reason, the sub should not see a "hole" in the front!
And cover up that hideous round black 18" monster ! 😒
For this reason, the sub should not see a "hole" in the front!
And cover up that hideous round black 18" monster ! 😒
I took quite a bit of measurements of distortion in sealed and ported subwoofers. In a perfect case you gain 15db of output by going ported right at the tuning frequency while keeping distortion levels the same. However this bass output comes at the tuning frequency comes 10-20ms later than lets say an octave up (group delay) and the output of port usually takes longer to decay than the driver by itself. Is it worth it? For music I say no, a better option is to add a second driver and get 6db of added output across the board. For home theater or PA where you want to squeeze out the most SPL it's an option and with a very low tune the added group delay is less noticeable.
I think the 8-20 Hz does add a lot to film where the recording goes that low, and some music tracks it provides a lot of spatial cues and a feeling of realism. feet moving on a stage, the back of a guitar etc. It also seems to help solidify the image and gain believability even though no net is played.
I am sensitive to fractions on a Ms on timing when setting the subs are near correct, 0.5ms is notable when they are getting very close, seems bizarre and might be psychological
Regarding that, I must tell you that there are 2 subwoofers and being corner subwoofers they increase the gain even more (+++). In the attached graph you can see the location, the clumsy sketch is due to my lack of management of technical drawing programs, but you just have to imagine that being corners, the gain is even greater.
My expectation is to use the converted BR subwoofers without any DSP or EQ, I'll just drive the gain I feed them with the amp, which by the way has power to spare as I mentioned. I have had the previous experience with a monophonic 250 Watt plate amplifier (power to be shared between 2 subwoofers) and 2 vintage BR cabinets, and, although the most noticeable difference is that I had to place them behind my listening position (in the field near) and now I do it in the far field with power to spare.........they sound different! For me harmonics are missing, I can't find another explanation.
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