Well, I'm not going to try and push any theories here, my understanding is way below par to try and talk shop lol! I will just be thankful to receive good reliable guidance, and ty.
Remove excursion? Check
Remove sub from midrange? Check
I get that you don't like the PPSL but it increases headroom, to a level I find desirable, without having to use a vent, in space that takes up less space then using 2 front faced woofers. I think it causes a little phase issue judging by the response sums. Outside of that, theres nothing to dislike about it. HP the bs and iron out the wrinkles with eq. Supposedly I can fix the phase issue with DSP so it should perform much more like a front facing woofer when tuned properly.
Remove excursion? Check
Remove sub from midrange? Check
I get that you don't like the PPSL but it increases headroom, to a level I find desirable, without having to use a vent, in space that takes up less space then using 2 front faced woofers. I think it causes a little phase issue judging by the response sums. Outside of that, theres nothing to dislike about it. HP the bs and iron out the wrinkles with eq. Supposedly I can fix the phase issue with DSP so it should perform much more like a front facing woofer when tuned properly.
I did remember this configuration....when I visited it in simulation GD was not to my liking...but considering that phase/GD can be fixed. Can't hurt to take another look.
Thank you for explanation. Now I don't understand rear subs up to 200 Hz. Imho you will hear them.
Personally, I prefer front subs and other ways to solve room problems. I am using DBA.
There are front and rear subs planned. If I play up to 200hz, its possible I won't like them. 120hz is chosen by THX for good reason. The sub area will be carried by front and rear subs....A double bass array? =DBA. Doesn't this require front and rear subs? I guess the rear subs aren't increasing headroom at this point though.....
Of course they require
! But rears aren't audible. It may be better to use 3-4 feet of absorber on the back wall if possible.
Yea, best case, after much DSP and fiddling, it will work like a direct radiator.
The slot is simply a LP acoustic filter. It cannot increase headroom since that is limited by the passband response of the driver sans slot.
The increased accumulated sd of the 2 woofers involved, increase headroom, is what I was implying, yet it takes half of the area on the front baffle, due to the folding.
So the "area" facing you is an issue? I can't see how in your case that would mater very much.
Sorry I don't get how slots do anything positive. There are some small design issues that favor them but they are rare. Remember that I've built plenty 6th order bandpass designs before so I have a feeling for how they work. IMO the slot just makes everything more problematic.
To be fair, let me give you the quick and dirty of acoustic LP filters on drivers (what is known as a fourth order bandpass designs in the literature) - and that's what all of these are since the wavelengths are so long at the frequencies that you are talking about. The design comes down to a compliance coupled to a mass with some minimal damping. One can adjust the mass to compliance product to be whatever LP frequency I want, and then adjust the Q with different combinations of values keeping their product the same.
Now, since this is a passive filter placed over the driver, its passband cannot be greater than that of the same source in space without the filter - this sets the passband level. The acoustic filter can only add to this response level if the Q is >> 1, in other words a very high resonance. That can yield some narrow band efficiency increases at the passband edge, but it creates a resonance and all the audible problems associated with that.
The one exception to the above rules is that the upper and lower resonances can be brought together to yield a true passband increase in efficiency. But this yields a very narrow passband, with two close together resonances.
Using acoustic resonances becomes almost pointless with DSP as anything that you can do passive acoustically, you can do better electrically. I have not used any passive acoustic techniques since DSP.
Now, since this is a passive filter placed over the driver, its passband cannot be greater than that of the same source in space without the filter - this sets the passband level. The acoustic filter can only add to this response level if the Q is >> 1, in other words a very high resonance. That can yield some narrow band efficiency increases at the passband edge, but it creates a resonance and all the audible problems associated with that.
The one exception to the above rules is that the upper and lower resonances can be brought together to yield a true passband increase in efficiency. But this yields a very narrow passband, with two close together resonances.
Using acoustic resonances becomes almost pointless with DSP as anything that you can do passive acoustically, you can do better electrically. I have not used any passive acoustic techniques since DSP.
There is no other way to have the output from 2 18"s, facing you, on a face that is 32"x29". Also, the radiation area is completely summed due to the close proximity....all on a 32"x29" baffle, the height ends up at 43".....this allows the tweeter to be just about ear height, which is what I wanted.
Thats how I will approach the resonance,,, electronic filtering. The slot resonance isn't desirable but a casualty. Going from 1200cm2 to 2400cm2 Sd in an area that fits in the space I need to, is all.
It seems I just need to flatten phase, and then everything will be ok. Do you think it will be much more than this?
What about a drawing with dimensions, a listening position and a description? And measurements in the listening position))
DBA tread https://www.diyaudio.com/community/threads/my-double-bass-array-with-low-q-subs.392998/#post-7194206
From front wall and with corner speakers?! IMO it seems very, very close. And the lower longitudinal modes will be significantly excited
7' may be slightly close or normal.
Less orthodox, including different placement of front and rear sub(s), subwoofer arrangements can be used depending on the required upper frequency with same effect in bandwidth. If source sub(s) are at front wall and sink sub(s) are at rear wall, rear(s) inverted and delayed by room length.
REW RoomSim is a good toy, especially when compared to real measurements.
Last edited:
Most - thankfully not all, of today's pro drivers are designed for durability, power handling and small enclosures.
As a consequence Xmax and Mms have increased, resulting in lower Qts and, more importantly, lower η₀ .
'Coincidentally', my preferences for woofers also go hand in hand with low Le and GD.
Last edited:
I think you are saying to not vent this thing at the very least. I am partial to the 4th order bandpass myself, and if there ever was a good one, for a sub that can fit in your house, this is it. I think I solved the summing issue, without FIR, playing around with VituixCad. This would be a rough draft at best, and some of my struggle had to do with a time delay parameter misset. This is the type of crossing idea I had all along, I just wanted to be sure that I could create good summing through the whole woofer section. Of course in situ, everything changes, this is just practice I guess. Don't forget that the polar of the horn isn't true to life, but by 200hz it should be omni like on the vertical, so I think there is some truth to this ballpark sorta anechoic sim.
I think the vertical polar at crossing, could be improved.
My issue now is, the jbl 2". I need to make these holes an actual 2". I came up with a way to do that with a router and a flushing bit....The thing that has me perplexed is; how does one align all the holes? 3 holes, perfectly aligned, but you can't see them to align them.
The idea I had was to fix the horns to the stand, so that it can't move. Then I can mount the driver and take measurements? if I don't like what I see I can move the driver and remeasure. Looking down the horn to see if things are aligned isn't practical due to the size of the horn. Otherwise, these horn stands seem to be very well suited to the task.
Last edited: