Ok, so I found an article on tweeter position on the RJB Audio site that was written in a way to make it easily comprehended, for me anyway.
Now as far as my mid to tweeter distance i'll keep those as close as possible to keep them within 1w/l of the possible xover point. But I was doing the calcs for my tweeter position and left to right the position appears to be almost perfect. At 105mm from the closest side multiplying that by 1.6 I get 168mm, my distance to the other side is 165mm so I couldn't ask for much better there. My vertical distance of 90mm down from the top doesn't work though, and I've come up with 65mm down which gives 65x1.6= 104, and 65x2.6=169, so those figures seem to equal up pretty close to my left and right measurements.
Can anyone help me out with some reading on woofer positioning though, i've done a few searches and come up with nothing, GM suggested getting them low down but how low is low enough, can I remove that chamber right at the bottom and have the port just of the bottom with the woofers directly above that so the the edge of the lowest woofer is essentially 6-7" from the base of the cabinet. Or am I better having them up higher, closer to the mid, but then again how big a gap is acceptable to leave between the upper woofer and mid.
Thanks again guys.
Luke
Now as far as my mid to tweeter distance i'll keep those as close as possible to keep them within 1w/l of the possible xover point. But I was doing the calcs for my tweeter position and left to right the position appears to be almost perfect. At 105mm from the closest side multiplying that by 1.6 I get 168mm, my distance to the other side is 165mm so I couldn't ask for much better there. My vertical distance of 90mm down from the top doesn't work though, and I've come up with 65mm down which gives 65x1.6= 104, and 65x2.6=169, so those figures seem to equal up pretty close to my left and right measurements.
Can anyone help me out with some reading on woofer positioning though, i've done a few searches and come up with nothing, GM suggested getting them low down but how low is low enough, can I remove that chamber right at the bottom and have the port just of the bottom with the woofers directly above that so the the edge of the lowest woofer is essentially 6-7" from the base of the cabinet. Or am I better having them up higher, closer to the mid, but then again how big a gap is acceptable to leave between the upper woofer and mid.
Thanks again guys.
Luke
Greets!
I was starting to write a response to your previous post when a notification popped up, so this is as far as I got:
"Well, there's the golden ratio and acceptable room ratios are acoustic ratios, so two of the three can be used, ergo Google is your friend, returning these threads with others linked to:
http://www.rjbaudio.com/Audiofiles/tweeter diffraction.html
http://forum.studiotips.com/viewtopic.php?p=5570
That said, this issue apparently is still debated/ignored and/or dealt with using the time honored felt ring on this cone/dome forum: http://techtalk.parts-express.com/showthread.php?t=212899
So your baffle is ~7.18" wide? The posted sketch says ~10.63", implying a ~287 Hz eigenmode which in turn implies a 574 Hz driver/baffle edge eigenmode."
Moving right along.............
Hmm, I hadn't actually read that website till now, but historically AFAIK a golden ratio offset would be calc'd 270*0.618 = 166.86, so the other side is 0.618 of it and 2.618 across the span, making your posted dims nowhere near a golden or acoustic ratio. The distance to the top can then be any odd ratio.
I haven't played with any software though, so can't comment on which of the two ways is likely to measure best, just that it seems to work well when the tweeters are offset to the outside and that when I've put drivers close to an edge it doesn't sound right over a wide (~8 ft across is my acceptable minimum) 'sweet spot'.
Woofer layout is no different if the baffle's wide enough to offset them.
WRT vertical location, like I said, it's XO point/slope dependent and ideally spaced <1/4 WL away, so assuming a 300 Hz/2nd order, then the Hf - 12 dB would be at 600 Hz and ~13560"/4/600 = ~5.65" and since you have dual drivers their acoustic center would be midway between them, so this isn't physically possible with a narrow flat baffle unless the woofers are either placed on the sides and/or rear of the cab. Stretching it out to 1 WL puts it down ~22.6", so still well clear of the bottom, ergo no floor loading benefits.
All things considered then, I recommend putting them as close as you can to the mid driver and it is what it is. If nothing else, in a relatively tall tower it pushes the floor bounce frequency down to where it will probably get 'lost' in the room's modes if there's no coffee table or other reflective surface between the speakers and listening position to bounce off of first.
Yes, you can delete the XO chamber and placing the drivers at the extreme top and vent at the extreme bottom will maybe generate some TL loading to reduce vent length if you don't elbow it up, but 'coil' it around the bottom. Post a new layout and I'll check it.
GM
I was starting to write a response to your previous post when a notification popped up, so this is as far as I got:
"Well, there's the golden ratio and acceptable room ratios are acoustic ratios, so two of the three can be used, ergo Google is your friend, returning these threads with others linked to:
http://www.rjbaudio.com/Audiofiles/tweeter diffraction.html
http://forum.studiotips.com/viewtopic.php?p=5570
That said, this issue apparently is still debated/ignored and/or dealt with using the time honored felt ring on this cone/dome forum: http://techtalk.parts-express.com/showthread.php?t=212899
So your baffle is ~7.18" wide? The posted sketch says ~10.63", implying a ~287 Hz eigenmode which in turn implies a 574 Hz driver/baffle edge eigenmode."
Moving right along.............
Hmm, I hadn't actually read that website till now, but historically AFAIK a golden ratio offset would be calc'd 270*0.618 = 166.86, so the other side is 0.618 of it and 2.618 across the span, making your posted dims nowhere near a golden or acoustic ratio. The distance to the top can then be any odd ratio.
I haven't played with any software though, so can't comment on which of the two ways is likely to measure best, just that it seems to work well when the tweeters are offset to the outside and that when I've put drivers close to an edge it doesn't sound right over a wide (~8 ft across is my acceptable minimum) 'sweet spot'.
Woofer layout is no different if the baffle's wide enough to offset them.
WRT vertical location, like I said, it's XO point/slope dependent and ideally spaced <1/4 WL away, so assuming a 300 Hz/2nd order, then the Hf - 12 dB would be at 600 Hz and ~13560"/4/600 = ~5.65" and since you have dual drivers their acoustic center would be midway between them, so this isn't physically possible with a narrow flat baffle unless the woofers are either placed on the sides and/or rear of the cab. Stretching it out to 1 WL puts it down ~22.6", so still well clear of the bottom, ergo no floor loading benefits.
All things considered then, I recommend putting them as close as you can to the mid driver and it is what it is. If nothing else, in a relatively tall tower it pushes the floor bounce frequency down to where it will probably get 'lost' in the room's modes if there's no coffee table or other reflective surface between the speakers and listening position to bounce off of first.
Yes, you can delete the XO chamber and placing the drivers at the extreme top and vent at the extreme bottom will maybe generate some TL loading to reduce vent length if you don't elbow it up, but 'coil' it around the bottom. Post a new layout and I'll check it.
GM
You're right of course, I know better than to post when I'm tired and thought all I'd done is preview it, so I could vet it before posting later in the morning after some rest. Factor in that I'm in a more than usual time 'crunch' and all I could 'see' at a glance was that 105 mm wasn't anywhere near 0.618 of 270 mm, so time for me to bow out of the forums for the most part as this isn't the only dumb-*** mistake I've made recently due to being so preoccupied.
Good luck with the project!
GM
Good luck with the project!
GM
I hope you don't bow out, as you and the others who have replied to my thread have been great, you've made me think about my design more and helped me track down the info I need, as thinking I know what I need to take into consideration is one thing knowing what I need to consider is another. Plus the issue aswell that comes in that sometimes is not knowing the correct terms to search by, and sometimes you need replies from people to help point you in the right direction to find what your after.
Last edited:
Ok so using the advise from contributors to this thread and the links provided and a bit of material I've managed to find on google, I've come up with this for the cabinet design. As you can see the drivers are all offset, and grouped closely together. I've also still got the port at the base, though I may end up using two ports side by side at the base. Ideally I'd like to keep them in the front portion of the cabinet, so I'd have to put a 90deg bend in, as they come through the front baffle. I'd also most likely end up with more holes in the braces, those braces shown are 25mm mdf like the rest of the cabinet, but I'm thinking it would be fine to make them out of 18mm?
Anyway here are the pics, what do you think of this latest version?
Anyway here are the pics, what do you think of this latest version?
Attachments
Well looks like it's the above design then! Though I will refine the bracing design, as I feel it's a bit over the top and probably quite airflow restrictive, i'll most likely take out some of it in the lower end of the cabinet where cabinet vibration is not so likely to be affected by the driver, i'm also going to pick up a roll of lead from the hardware store with which to line the cabinet. I've also decided to go with an active xover rather then passive as I feel attempting my first passive for a project of this size was a probably quite a bit of over confidence on my behalf, and in reality a Behringer DCX2496 and a few more chip amp channels is probably going to be cheaper lol. I'm also quite comfortable with active xovers etc.. my car HU has a built in 3-way xover, selectable 6, 12, 18, or 24db LR, time alignment and level control on all 6 channels, as well as a 11 band Parametric EQ.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.