So I've got a couple older Polk 10" drivers sitting around and I'd like to build a vented push-pull slot loaded (PPSL) enclosure for them as something new. Since I've already got the drivers and the building materials all it will cost me is my time. I'll be using this sub for music and a little HT. The room it will be going in is pretty small (150 sq ft.)
I've attached a picture of what I've designed so far. The size is what will fit in my rather cramped room nicely. What I was like to know from the hive mind is if there is anything glaringly wrong with my design. It has 3 cu ft of internal volume and should be tuned to 32 hz. My biggest concern is since the enclosure is kinda tall I might get some weird quarter wave stuff going on. Any input will be greatly appreciated.
I've attached a picture of what I've designed so far. The size is what will fit in my rather cramped room nicely. What I was like to know from the hive mind is if there is anything glaringly wrong with my design. It has 3 cu ft of internal volume and should be tuned to 32 hz. My biggest concern is since the enclosure is kinda tall I might get some weird quarter wave stuff going on. Any input will be greatly appreciated.
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eh.
27hz was low enough for me.
That rolloff was 24db for the port and 12db for the filter.
30hz tone shook everything, but 20hz was gone.
Norman
27hz was low enough for me.
That rolloff was 24db for the port and 12db for the filter.
30hz tone shook everything, but 20hz was gone.
Norman
That's an interesting idea. I'll have to see how that will work out with my layout.
I would keep the drivers oriented "normally" and possibly widen and shorten the enclosure. I have used drivers vertically but it's best avoided when possible.
A "normal" driver mounting has the cones in a vertical orientation.
Cones mounted horizontally, as in the OP's drawing, tend to sag downward.
When the cone "sets" in a sagging position, Xmax on the downward portion of the signal is reduced.
Yes, thanks for the clarification- cone sag is my concern- Why introduce a potential problem?
Simple, Screw down the driver in a jig positioned vertically. Set up a micrometer probe bolted down to the basket, run the probe towards the dustcap, just touching (Maybe difficult to judge here). Zero the micrometer & tilt the whole assembly 90 degrees to horizontal forcing the cone to deflect the micrometer X distance. I'll think you'll find this is a non-issue.
Getting no resultant data will bring the "sag camp" out in force saying you botched the experiment.
________________________________________________________Rick........
Getting no resultant data will bring the "sag camp" out in force saying you botched the experiment.
________________________________________________________Rick........
Rick,
What is a non-issue?
Cone sag does not occur in minutes, but can be quite appreciable over months.
Cone sag is dependent on a number of factors, some speakers don't deform much, others are quite prone to sag.
Even when mounted upright (cone vertical, voice coil pointing forward) cone sag can be a problem.
Rotating the speaker 180 degrees can correct buzzing caused by the voice coil former sagging down.
Do you have any data to support this claim? Citations to research?
So your saying that the Qms of a driver changes "appreciably" over the course of a few months?.......so the calculations using Qts get thrown out the window because the value of Qms "goes south"?
_____________________________________________________Rick.........
So your saying that the Qms of a driver changes "appreciably" over the course of a few months?.......so the calculations using Qts get thrown out the window because the value of Qms "goes south"?
_____________________________________________________Rick.........
Citations? Data? Are you kidding me? How about practical experience? I didn't photograph the screwed up suspensions from some upfiring subs I had to "bring to true".....
Lowthers are specifically recommended to be rotated every so often because the suspension (a very low loss setup) sags, and that's in a front-firing setup.
There's no meaningful reason to orient them in such a way as to introduce this issue.
Additionally, the Qms doesn't need to change significantly with sag- in fact, it's not meant to in linear spiders, so you're not even asking the right question, the displacement longer-term of the voicecoil is the bigger issue.
Lowthers are specifically recommended to be rotated every so often because the suspension (a very low loss setup) sags, and that's in a front-firing setup.
There's no meaningful reason to orient them in such a way as to introduce this issue.
Additionally, the Qms doesn't need to change significantly with sag- in fact, it's not meant to in linear spiders, so you're not even asking the right question, the displacement longer-term of the voicecoil is the bigger issue.
Rick you might be interested in doing some reading, Art is not making this stuff up. Large drivers used to be the norm and flipping your drivers on a regular scheduled was considered good practice. People are lazy people don't want to read people don't even want to find out when it's on line to find for free. Small drivers with rubber and synthetic rubber suspensions don't have these issues to the same degree. Sag is real sag is a concern. Store a driver face up or down for a prolonged period of time and take a look. Best regards Moray James.
just make the box so that you can turn it around frequently 😀
but I have never mounted a driver playing up or down, and I never will
but I have never mounted a driver playing up or down, and I never will
Examples of cone sag are all over the internet.
There are even formulas to figure out if it will be a problem when selecting a woofer.
JBL cones are often cited for sag but I recall my EV-15L in stage monitors, which were transported with the cone facing up, and at around 30 degrees in use, would start to look like the sagging JBL 1500GTi below.
That is if they managed to survive long enough before the cones kinked or the voice coil was burnt 😀.
Art
There are even formulas to figure out if it will be a problem when selecting a woofer.
JBL cones are often cited for sag but I recall my EV-15L in stage monitors, which were transported with the cone facing up, and at around 30 degrees in use, would start to look like the sagging JBL 1500GTi below.
That is if they managed to survive long enough before the cones kinked or the voice coil was burnt 😀.
Art
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in severe cases of cone sag I suspect the drivers have been exposed to moisture for longer periods
I guess you know how it is with pro gear used a lot outdoors
and when big speaker setups are not in use, how the storage conditions may be
hifi conditions I expect would be different
I guess you know how it is with pro gear used a lot outdoors
and when big speaker setups are not in use, how the storage conditions may be
hifi conditions I expect would be different
Wow, this thread got a lot of activity all the sudden.
Pertaining to my original question, I changed the design and made it shorter, but much deeper. This got rid of the bend in the port and should eliminate any of the quater-wave issues I was worried about. I still have the drivers up-firing though.
Cone sag is something I haven't really thought about. These drivers have pretty light weight cones so I'm not overly concerned about it. If needed I can always pull them out and flip them over in the enclosure every so often.
Also if cone sag was such a huge issue how come like 90% of tapped horns have the drivers mounted in a near up-firing or down-firing position?
Pertaining to my original question, I changed the design and made it shorter, but much deeper. This got rid of the bend in the port and should eliminate any of the quater-wave issues I was worried about. I still have the drivers up-firing though.
Cone sag is something I haven't really thought about. These drivers have pretty light weight cones so I'm not overly concerned about it. If needed I can always pull them out and flip them over in the enclosure every so often.
Also if cone sag was such a huge issue how come like 90% of tapped horns have the drivers mounted in a near up-firing or down-firing position?
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