??? can you show more of the box, i'm not seeing how there's two drivers...and given that the crossover appears to have both Left and Right in one location it hints that it should be a mono sub,no?
if the replacement surrounds changed the resonant point significantly re-tuning the box/ports may be in order.
if the replacement surrounds changed the resonant point significantly re-tuning the box/ports may be in order.
just put the sub into a corner, drivers / reflex ports facing to the wall or corner.
Gives extra bass for free!
Gives extra bass for free!
I can't show more of the box as it's out on lease. It's isobaric. If you look at the 2nd pic, the other driver is facing up, underneath the driver on display.
so what sort of ring or seal (if any ? ) was there between the two drivers?
and NIXIE62 asks the exact question that needs answering what is the phase relationship of the two drivers? i'd go as far as doing a closer examination of the crossover wiring for any errors....
and NIXIE62 asks the exact question that needs answering what is the phase relationship of the two drivers? i'd go as far as doing a closer examination of the crossover wiring for any errors....
Replacing the soft, light and compliant foam surrounds with rubber, which is heavier and most likely has different compliance than the foam, has changed the t/s parameters of the drivers.
The f response of this particular type of band pass enclosure is quite sensitive to changes in t/s.
The f response of this particular type of band pass enclosure is quite sensitive to changes in t/s.
I've been told by people in the business that the spider has more of an effect on T/S parameters than the surround. It has been my experience that the same is not true when replacing the surround. The box will likely need to be retuned to the new driver parameters.
rubber surrounds last longer than foam surrounds.
For the sound in the bsss the surround plays a smaller role than in the mids where different damping properties can play a role.
For the sound in the bsss the surround plays a smaller role than in the mids where different damping properties can play a role.
Is that frequency graph the predicted response or the actual response?
That's a pretty strange arrangement with one long vent and two short vents.
I suggest measuring the actual FR and then adjusting the lengths of the vents accordingly.
BTW, IMO isobaric 4th order BP designs can produce some of the cleanest bass you can get. The isobaric arrangement reduces even order distortion, and the acoustic bandpass reduces odd order distortion. End result is a build that can sound clean right up until the drivers stop working, LOL.
You're right, both suspensions have a big impact. I replaced the worn out rubber surrounds on the Vifa P13WH with foam surrounds and the change was dramatic. In general, it is not recommended to change the type of material, but a friend advised me to try foam surrounds instead of rubber for these drivers, and it turned out great. If not, I would look for rubber surrounds. I think that the other way around is not really recommended (to put rubber instead of foam).
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the surrounds if not extremely different (like being much more stiff) make only a small difference:
influence of cone mass, enclosure volume and yellow spider dominate the result
influence of cone mass, enclosure volume and yellow spider dominate the result
If the drivers are phased correctly, that SUB probably wasn't good before repair, so the owner is now disappointed when he hears it. But no one knows what it sounded like before. I would try turning the phase on the satellites, maybe that's the problem? In any case, the measurement would tell everything. We can talk like this for days without a real solution. 🙄
This may well be true. To my ear the box sounds nothing like the model. I'd guess the bass response starts dropping off around 100hz. The system sounds like a micro hifi system. But it's MY issue. The system plays background music in a restaurant and they're not complaining.
I still suspect the wrong phase of those bass drivers. When you try it with a 1.5V battery, that driver in the bass reflex should be in counter phase (coil enters the magnet), and the one in compression in phase (coil exits the magnet).
The box is bandpass + isobaric. That way they got it to run low and to reduce the volume to 50%. Each bass is fed from one channel of the amplifier via a passive crossover, and sums acoustically. An alternative is a two-coil driver, but then a larger box is required.
According to this sketch, when the positive of the battery is on the positive input connectors (connect both connectors plus and minus in parallel for the test), both diaphragms should move to the right. And vice versa.
Or simply reverse the phase on one driver and see what happens. Just don't overdo it so the membranes don't collide.
The box is bandpass + isobaric. That way they got it to run low and to reduce the volume to 50%. Each bass is fed from one channel of the amplifier via a passive crossover, and sums acoustically. An alternative is a two-coil driver, but then a larger box is required.
According to this sketch, when the positive of the battery is on the positive input connectors (connect both connectors plus and minus in parallel for the test), both diaphragms should move to the right. And vice versa.
Or simply reverse the phase on one driver and see what happens. Just don't overdo it so the membranes don't collide.
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Phase is fine.
If I disconnect one channel: less volume, less bass.
If I reverse the polarity of one: no bass whatsoever.