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Similost's Speaker Build - Watch this space for lots of laughs.

James,

I don't want to dampen your enthusiasm, but you might want to save yourself some trouble and try building these up with standard ports before you cut big holes for PR's. From some quick sims in WinISD, I don't see any way for a PR15 to work with a TD15M in any size box, at any weight. The tuning is just too low. They won't add any appreciable output to the speaker, the response might as well be that of a sealed box. Maybe that was the reason the original owner never got these parts built up together?

I agree with dnewma that 120 liters / 40 Hz-ish would work OK, a bit bigger bigger would be better, and would add that that tuning would be easily done with standard ports. Sell off the PRs to defray the cost of the rest of the project, or use them in a dedicated sub project later on.

Should you ever build or buy a sub to go with them, the volume you have would be very good as a sealed box (or a ported box with optional Zilch-plugs - can't do that with a passive). You'd be -6 dB at around 56 Hz, -3 at 80, but it should be clean and tight, and hard to get wrong.

Just my opinion, of course. Your ears may vary!

Bill
 
A valid point. Simi, at this point we're guessing about your PR. I'm just using some numbers that came out of the sim program and are pretty generic.

If you tune to 40Hz you're looking at a single 6" dia x 5 1/8" long port.

If you want to play around with the PR, then by all means do so. But it would probably be easier and safer, especially for the cab, to go ported. Not saying a PR won't work or trying to talk you out of it, just pointing out.
 
And the hole for the port could be enlarged later for a PR, but obviously not the other way around. Are PRs more forgiving than tuned ports?

Boy, that 15 looks like it's going to play well right past 1K Hz. I wouldn't have thought that, and I've been assuming that 'laid back' mids may be a fault with the ewave when large woofers are used. I guess not. With the way the graphs look, low bass extension won't be on your menu, so a subwoofer may be in your future anyway. A nice sounding sub adds a lot, I never listen to music with mine off.

Those are great looking cabinets, btw. I'm reminded of some vintage looking cabs my dad has offered to me that I need to go get before they go bye bye.
 
OK.. I can accept the fact the PR won't work in this case. I just figured one, since I have them, might as well use them.. and two, I have no room in the front baffle to put ports with this driver and the horn..

So let me ask this... can the port be put in the rear of the speaker? If so, do I have to keep it very far off the wall? They will be in corners of the room angled in..

Yes, these speakers will play well up to 4000hz supposedly.. 2khz very easily...

I'll have to see what's gonna happen with these, as far as needing a sub..
 
A port can be just about anywhere on the cabinet as long as there is space for it to move air. Corner loading would allow more than enough space.

4000khz is on axis, I certainly wouldn't use it in that application. 1200-1500hz is where it's extreme off axis starts to fall off, that's realistically where you want to be. If you are using a waveguide with 60 degree dispersion, bumping that up to 2khz is reasonable.
 
Yeah.. on axis for the 4k.. I did know that, but neglected to say that.. I am going to cross this at 1200..

I guess I'll end up getting a big hunk of PVC and porting it on the rear...
 
RayW said:
A valid point. Simi, at this point we're guessing about your PR. I'm just using some numbers that came out of the sim program and are pretty generic.

If you tune to 40Hz you're looking at a single 6" dia x 5 1/8" long port.

If you want to play around with the PR, then by all means do so. But it would probably be easier and safer, especially for the cab, to go ported. Not saying a PR won't work or trying to talk you out of it, just pointing out.
Click to expand...

So Ray, I've been trying to run all these numbers through Unibox, and WinISD, and I'm thinking about changing my nick to Completely-lost.. I think I see the light a little, but it is port size and length that is throwing me...

So if I use the length and diameter you are stating here, then the box will be tuned to 40hz and I won't risk over excursing the driver correct? So at 35hz, how far rolled off db wise will I be?

I sure wish I had just a little bigger box... I had already pointed at my Peavey boxes, but my wife nixed that idea.. Part of the deal was, I could build what I wanted cost wise in these boxes because my wife likes the looks of them.. so I'm making do, just like she is..

Is there any room to tune it a hair lower, or is 40hz my safest point?
 
similost said:
They will be in corners of the room angled in..
Click to expand...
I wouldn't assume they will be angled in until you listen to them. Mine sound better squared to the wall. Another option for the port is the bottom since they are raised off the floor 3.5". If you add legs they will be higher and will raise the CD closer to ear level when seated.
 
Nah.. my wife isn't going to go for the legs.. I also don't want to cut a hole in the bottom since that part isn't easily replaceable.. I don't want to cut the original back either, so I am just going to make a new back since I have to fit in a terminal cup, and two l-pads..
 
similost said:
So if I use the length and diameter you are stating here, then the box will be tuned to 40hz and I won't risk over excursing the driver correct? So at 35hz, how far rolled off db wise will I be?
Click to expand...

Looks to me like you could tune it down to 30Hz without giving up much in the way of excursion limited power handling. However, it also doesn't look like the low end performance is going to change all that much either. The f3 and f6 numbers go up and the knee where it starts to really drop off goes down a hair. You might get a few more Hz out of the low end but it's not going to be a lot.

If you're going with PVC you can experiment pretty easily. Just cut your hole so that it's a friction fit and you can start with a long port (30Hz tuning would be about 13 1/2") and cut it down and see what happens. From the graphs it looks like you're not going to be in trouble anywhere around there.
 
I found the bottoms of my Barzilay cabs to be cheap particle board. The risers on them is (was) also.

Mine were water damaged, so I cut the bottoms (feet?) off with a circular saw. I'm going to add another board to the bottom as the particle board that is there doesn't look all that sturdy to me.

The 4.5 cu ft cabinet size is why I've been sticking to 12" woofers.

I will most likely add some legs to mine, and I like the bottom port idea.

Never thought about corner placement, thought it'd look strange.

Also I used Howards on mine and they look great as is!

Also I thought the passive radiator might help Simi with the over excursion problem vs a port.

Its not difficult to have another set of baffles for the back. Build one with a port and one with a passive radiator. I'm paying $6.50 a piece for 2x2 baltic birch plywood in 3/4" @ Lowes.

I think in so far as simplicity is concerned the port is easier, but I would not abandon the passive radiator idea yet. Especially given your excursion limitations.
 
I will cut a back to try the PR's in it just for grins and to see what it sounds like, BUT, if I get the tuning too low, I do risk damaging the woofer if i push it too hard..
 
Thanks Ray. I appreciate it... I don't know that I really want to try tuning down to 30hz, but I think I could try a little longer port than the 5 1/8 or what ever it was, and see if I can notice any difference in sound.. Sounds like I'm really not going to gain much... I guess these drivers are what they are, and I'm trying to get something out of them they just aren't going to put out..
 
I know even less than Similost, but am really learning here. How will damping material affect the low frequency in this application?
 
tensleep said:
I know even less than Similost, but am really learning here. How will damping material affect the low frequency in this application?
Click to expand...

Good question.. I know it affects it, but not sure how, as in what it does.. adds or detracts...
 
Simi, you could add a small extension box to the back of the cabinet and get another cubic foot or two. Just build a 5 sided shallow box to hang on the back where the backs originally were. You could make the sides slope in even so it wouldn't show too much. :yes:
 
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