There is something wrong with the design/construction/mic or whatever as the SB20 should not be dropping at 150Hz like that, and should not require that much EQ down low, which as you noticed, induces a lot of distortion.
Are they still measured laying on the floor, or on stands as they should be?
Are they still measured laying on the floor, or on stands as they should be?
The cabinets spent a whole night under heavy weights. I measured it once again at 1 meter and then EQ'd it properly this time. It seem to have fixed issues I was having in the 100 to 200Hz region. Does that mean I probably had a leak, and I probably fixed it now?
I'm pretty happy with how linear the response is now.
How are these distorsion numbers? I don't really know what to make of them. Distorsion is naturally higher below 200Hz because that's where I corrected the otherwise droopy response I was getting in that area, but it sounds right to my hear. Maybe a tad smudged, but also large and expansive, which is a good thing to me. Otherwise, what's the point of large cabinets?
My bad, didn't see your post. Indeed there seem to be something wrong when I first measured it. Here are todays measurements after some fixes to the cabinet. The measurements were done with the speaker on a stand and some weight on top of it. The cabinet is really light and needs some added weight.
Orange line is EQ and blue line is not EQd. It seems to have removed that massive dip in the 200Hz region.
I do.
i am sensitive to distortions, and looking at post 104, that’s way too much.
you are trying to beat the driver into a shape it does not want to be naturally.
i am afraid I need to repeat this: there is something wrong either with the design or the construction.
a vented box should give you in the high 50s. There’s no way it would start dropping at 200Hz.
One more thing, you’ve built and measured one box/driver only, right?
Maybe just maybe, it’s the driver. Swap the other driver in your box to see if it behaves the same. lets see if it’s not a defective driver.
PS glad we’ve resolved the floor bounce. One step at a time.
i am sensitive to distortions, and looking at post 104, that’s way too much.
you are trying to beat the driver into a shape it does not want to be naturally.
i am afraid I need to repeat this: there is something wrong either with the design or the construction.
a vented box should give you in the high 50s. There’s no way it would start dropping at 200Hz.
One more thing, you’ve built and measured one box/driver only, right?
Maybe just maybe, it’s the driver. Swap the other driver in your box to see if it behaves the same. lets see if it’s not a defective driver.
PS glad we’ve resolved the floor bounce. One step at a time.
When I measure the speaker, I have to crank it up much higher than I actually listen to. Playing a sub-100Hz at that volume makes the cabinet rattle, which is being picked up by the mic. This could explain the added distorsion. When I listen to it at normal level, it doesn't rattle.
Another possible explanation is that at the moment, the driver is screwed directly to the XPS, which is less than ideal. Maybe the seal around the driver is imperfect? It's something I've been meaning to fix, but I don't have the materials at hand to do so.
I'll get started on the second speaker tomorrow, with a much better glue and with some more experience regarding bracing. I'll also add something between the driver and the baffle, like foam rubber or something to maximize the seal, and I'll report back.
I've checked what baffle step looks like on a frequency response, and mine looks oddly in line with that, could that just be it?
Try gluing small pieces of wood behind the XPS for the screws to bite into. That will keep the driver snug in place, not just hanging from foam.
Any driver with heavy EQ down below will add distortion, not just the XPS cabinet rattling, but driver distortion as well.
The graphs you showed looked like it was a leak from the cabinet, losing pressure and not using the port as intended.
I have sim'd that driver and it looks like a really nice response, so there's something amiss here.
The drop at 200Hz is not baffle step loss.
Any driver with heavy EQ down below will add distortion, not just the XPS cabinet rattling, but driver distortion as well.
The graphs you showed looked like it was a leak from the cabinet, losing pressure and not using the port as intended.
I have sim'd that driver and it looks like a really nice response, so there's something amiss here.
The drop at 200Hz is not baffle step loss.
You live you learn...
I'll get started on building the second one tomorrow. I'm going to improve on every aspects and then will measure it. It's probably due to poor building techniques and wrong glue for the purpose. I'll make the next one squeaky clean, caulked and precise.
I'll get started on building the second one tomorrow. I'm going to improve on every aspects and then will measure it. It's probably due to poor building techniques and wrong glue for the purpose. I'll make the next one squeaky clean, caulked and precise.
Not must has changed in speaker design since the 1930’s.
A good large speaker box made of soft wood then veneer with hard wood. You buy veneer from places like Home Depot. Here box I just purchased for $29.00 24X96.
I will respectfully disagree here.
True the "physics" has has been the same and has not changed over the years, but our understanding of it, and the tools that are available now (like simulations) have greatly improved.
Drivers' research on materials and performance has also improved quite a bit.
In 1960's they talk about baffling forwarded speaker in a smaller speakers boxes.
On the side most do not want a big box speakers in there family room.
Just go to big box store and the sale person with tin ear 👂 can till the difference Good luck.
Dave
I finally got around to building the second cabinet. I implemented lessons from building the first one, and I also bought a new glue. It's so much better than PVA in every way. It sets really quickly, it's very strong, it can fill large gaps, can act as a sealant, and also remains sorta flexible, which I'm sure is doing some sort of job absorbing vibrations along the way.
Here are the measurements for the second speaker, corrected with Equalizer APO. As you can see, the distorsion is much, much lower than the first box I built, and the speaker is also somewhat able to dig even deeper (almost usable to 25-30-ish Hz).
Compared to the first box:
Overall, I'm very happy. Thanks again @Scottmoose for supplying me with the design.
Thing is... These are wayyy too big for my small room. So they might just move to the living room in the future, and be replaced by a second build, which, given the drivers I've been amassing, is shaping out to be a 2-way bookshelf-ish Synergy horn with a Planar tweeter crossed to 2 paralleled 8" bass drivers per horns.
Here are the measurements for the second speaker, corrected with Equalizer APO. As you can see, the distorsion is much, much lower than the first box I built, and the speaker is also somewhat able to dig even deeper (almost usable to 25-30-ish Hz).
Compared to the first box:
Overall, I'm very happy. Thanks again @Scottmoose for supplying me with the design.
Thing is... These are wayyy too big for my small room. So they might just move to the living room in the future, and be replaced by a second build, which, given the drivers I've been amassing, is shaping out to be a 2-way bookshelf-ish Synergy horn with a Planar tweeter crossed to 2 paralleled 8" bass drivers per horns.
And a family photo to show them off. The stands are obivously temporary. I needed them slightly propped and angled upward to align with ear level. Right next to the tiny studio monitors I was using up until now.
Hi, I’m also using this driver in a cabinet I have almost built up with internal dimensions of 11”x11”x35”. My hope was to build a MLTL similar to what Zu has done with Omen series speakers , just with a 8” driver.
I have read most other threads that have mentioned this driver and many concerning MLTL design along with MJK’s site. I just don’t have access to the worksheets or Hornsrep and would rather not use “rules of thumb” to determine driver and port placement.
I’m estimating the driver being placed somewhere between 20-23% down from the top of the line and port approximately 4-5 “ up from the bottom.
Could someone please let me know if I’m on the right track?
Thanks in advance
I have read most other threads that have mentioned this driver and many concerning MLTL design along with MJK’s site. I just don’t have access to the worksheets or Hornsrep and would rather not use “rules of thumb” to determine driver and port placement.
I’m estimating the driver being placed somewhere between 20-23% down from the top of the line and port approximately 4-5 “ up from the bottom.
Could someone please let me know if I’m on the right track?
Thanks in advance