Using only 1 driver of a 2 x 10" push/pull (enclosed) subwoofer, technical explanation?

[Geertidow]

Dear forum members,

Using the 'sub crawl method' I have recently placed my closed (non-ported) 2 x 10" push pull subwoofer in the left corner of my room (approximately 3,5 x 5,5 meters).
This subwoofer is supporting my pair of KEF R3's and is powered by a nCore NC500MP (the KEF's by NC252MP).

The measurement was best with the subwoofer vertically placed and the lower driver disconnected (I think the position close to the floor just measured worse).
The sound is incredible (and the frequency response as wall as compred to all other positions).

But my question is: I now have a subwoofer with one connected driver and one disconnected (and reversed) driver. What kind of subwoofer would you consider this and did I do something stupid from a technical point of view. I assume the passive driver just moves a bit with the active driver.

Thanks for your considerations/answers

 

[tomtoo]

You have now double the impedance, halfed the max. Power. You have more than doubled the mass of the membrane. What should lower the resonance frequence of the chassis.

 

[ZolaIII]

Second driver disconnected act's as pasive diffuser and shaves a bit first one as it's responding in opposite direction (180° phase). Did you ever try to decouple it from the floor and absorb most of vibrations it produces so that it's not passed trough the floor in the rest of room? I use egg seaters for that.
I reed most of:

Why does DIRAC completely remove bass response (KEF R3 + sub + minidsp flex)

I was able to do this with REW and a MiniDSP. Basically align the timing of the subs and mains to flatten that response Unless you are making nearfield measurements you really do not know if you are anechoically aligned as the room will have a large contribution to the measurement...

www.audiosciencereview.com

To accommodate @abdo123 try crossover like this and with R3 port's closed of course:

Wharfedale EVO 4.4 vs KEF R3

A happy owner of R3 here, enjoying every second with them. If I could buy them with 1150euro back then,,, it would even take me shorter time to decide lol Stay away from those kind of expensive speakers. It will make you broke.

www.audiosciencereview.com

Instead switching phase 180° on sub switch it on R3 (switch R-L wires on speakers terminals as it will work better than switching the phase where is the most energy in sub 100 Hz region). Sub needs to be in the middle, you would actually need two sub's one doing left and one doing right chenel and right to the left and right speaker (because 100 Hz crossover so that you get separation in 100 to 80 Hz region) for it to work totally as it should but I don't believe it will be a much of a problem even with one if put in the middle of the room doing both chenels. Other than that I can help you afterwards to PEQ it by hand.

 

[Geertidow]

Second driver disconnected act's as pasive diffuser and shaves a bit first one as it's responding in opposite direction (180° phase). Did you ever try to decouple it from the floor and absorb most of vibrations it produces so that it's not passed trough the floor in the rest of room? I use egg seaters for that.
I reed most of:

Why does DIRAC completely remove bass response (KEF R3 + sub + minidsp flex)

I was able to do this with REW and a MiniDSP. Basically align the timing of the subs and mains to flatten that response Unless you are making nearfield measurements you really do not know if you are anechoically aligned as the room will have a large contribution to the measurement...

www.audiosciencereview.com

To accommodate @abdo123 try crossover like this and with R3 port's closed of course:

Wharfedale EVO 4.4 vs KEF R3

A happy owner of R3 here, enjoying every second with them. If I could buy them with 1150euro back then,,, it would even take me shorter time to decide lol Stay away from those kind of expensive speakers. It will make you broke.

www.audiosciencereview.com

Instead switching phase 180° on sub switch it on R3 (switch R-L wires on speakers terminals as it will work better than switching the phase where is the most energy in sub 100 Hz region). Sub needs to be in the middle, you would actually need two sub's one doing left and one doing right chenel and right to the left and right speaker (because 100 Hz crossover so that you get separation in 100 to 80 Hz region) for it to work totally as it should but I don't believe it will be a much of a problem even with one if put in the middle of the room doing both chenels. Other than that I can help you afterwards to PEQ it by hand.

Decoupling is already in place using a Auralex Gamma (Gramma?)
For crossover I have a 12 db/Oct @ 80 Hz which works really well in my room in terms of measurment.

Just to be clear, the sound and DIRAC (correction up to 300 Hz) measurment is working well at this moment and I greatly enjoy the sound. For the first time in years I haven't changed any setting for a few months now.

But I just want to know what kind of subwoofer I have.

So my conclusion is: 8 Ohms with half the max power?

 

[ZolaIII]

Those Auralex Gamma (V2 presumably) seam as acoustic foam, told you silicone is the best (as it's fundamental is at 9.5 Hz). All do people say that they work it obviously isn't enough in case of your sub. You didn't show us your sub nor told what's the internal volume of it. But if it works like that for you it's fine with me and much better for both then doing a lot of stuff just to improve it a little bit with lot of hustle. Two drivers firing will produce twice the air compression and twice the cabinet refractions/vibrations. Already told you that other driver when not working, works as pasive diffuser and in opposite direction shaving a bit response with that little it produces (from cone excursion from air pressure alone) of first one that does work which lowers the refractions/vibrations and transfer to the room. R3's have a little more energy in bass that they produce well (100 to 250 Hz range) and sealed port's help with that. Main problem is when sub overlaps with that range adding it additional boost (it becomes boomy). I assume you have port's closed on R3 as it is (because it's 12 dB per octave slope) and it's second order crossover (sub - 3 dB to mains) with both filters or should we say Linkwitz-Riley.

 

[Geertidow]

Okey here goes:
Internal volume: not sure, outside is 42x50x64 (cm) (134 L). Since the cabinet does not vibrate at all (I can put a glass of wine on it/tiny ball on it and it won't move) I assume the internal volume is quite a bi tless)
Drivers: 4 Ohm Scan speak (2x). In push/pull setting 2 Ohm, single then 4 Ohm.
Serial number 26W/4534G00 (4 Ohm).

 

[ZolaIII]

Ufff uf... those are more like regular woffer's.

Scan-Speak

Neither go very low nor have big excursion limits (6 mm linear and 12 mm max). So they are in 0 to 180° phase alignment to each other (push, poll). How about that you for starters set them both to push (0°) phase if cabinet is sturdy as you say instead concealing each other? On the long run think about getting some better active sealed back subwoofer's with implemented Linkwitz transform function.

 

[Geertidow]

The 'pull' sub is connected in opposite phase. I don't think they are conceiling each other (except when disconnected).

 

[ZolaIII]

The 'pull' sub is connected in opposite phase. I don't think they are conceiling each other (except when disconnected).

It's just input ± wiring like with any other speaker so set + to cable + and - to cable - for the other one which has it reversed (to be poll) you will get less THD on lower volume and ability that it goes about +3 dB max SPL more.
Do you get it?

 

[Zapper]

But my question is: I now have a subwoofer with one connected driver and one disconnected (and reversed) driver. What kind of subwoofer would you consider this and did I do something stupid from a technical point of view. I assume the passive driver just moves a bit with the active driver.

The disconnected speaker acts as a passive radiator. You now have a ported subwoofer, with the passive radiator as the port.

To find out what that does theoretically to the frequency response would require knowing the internal volume and the speaker coefficients and putting them in a modeling program or doing the math. If the port tuning works out right it could extend the low frequency response. Since the speaker was not intended to work in this fashion the port tuning is probably not optimal, but by happy coincidence it matches well with your room response.

 

[Chrise36]

Okey here goes:
Internal volume: not sure, outside is 42x50x64 (cm) (134 L). Since the cabinet does not vibrate at all (I can put a glass of wine on it/tiny ball on it and it won't move) I assume the internal volume is quite a bi tless)
Drivers: 4 Ohm Scan speak (2x). In push/pull setting 2 Ohm, single then 4 Ohm.
Serial number 26W/4534G00 (4 Ohm).

134l for closed 10" push pull is a bit large how did you calculate this have you measured the driver parameters?

 

[Geertidow]

134L is the outside, it's lined with sand and God knows what. I did not build the sub I bought it from a professional (as in I don't know all the details). Inner volume is a lot less I would guess.

 

[Geertidow]

It's just input ± wiring like with any other speaker so set + to cable + and - to cable - for the other one which has it reversed (to be poll) you will get less THD on lower volume and ability that it goes about +3 dB max SPL more.
Do you get it?

Ah there is a misunderstanding I think. The drivers are just inserted oppositely on the same plane. So one driver is screwed in normally, the other with the magnet towards the outside (and connected reversely so they move the same way).

 

[Geertidow]

Ufff uf... those are more like regular woffer's.

Scan-Speak

Neither go very low nor have big excursion limits (6 mm linear and 12 mm max). So they are in 0 to 180° phase alignment to each other (push, poll). How about that you for starters set them both to push (0°) phase if cabinet is sturdy as you say instead concealing each other? On the long run think about getting some better active sealed back subwoofer's with implemented Linkwitz transform function.

Why would you want built in transforms with a MiniDSP flex (which I have). I chose the 80 hz 12 db oct crossover deliberately because the sound and measurements were to my liking.

Based on the KEF R3, would you recommend other woofer drivers (as long as they are 10 inch)?

The manufacturer says inner volume is approximately 65L.

 

[ZolaIII]

Why would you want built in transforms with a MiniDSP flex (which I have). I chose the 80 hz 12 db oct crossover deliberately because the sound and measurements were to my liking.

Based on the KEF R3, would you recommend other woofer drivers (as long as they are 10 inch)?

The manufacturer says inner volume is approximately 65L.

I wouldn't (want to make Linkwitz transform especially with those driver's).
It's self explanatory why it's usually incorporated in sealed sub's.

ESP - The Linkwitz Transform Circuit

ESP - The Audio Pages. A complete description of the Linkwitz Transform Circuit - find out how it works.

sound-au.com

I am not in a DIY business really, hopefully some of folks who are will be so nice to recommend you some.

 

[ZolaIII]

Did some searching and came to this one's:

Acoustic Elegance IB10AU-4 - 10″ Subwoofer 4Ω

Technical parameters and comparison of the Acoustic Elegance IB10AU-4 10″ Subwoofer 4Ω · Resonance frequency 25Hz · Power handling 1000W · Sensitivity 84dB · Xmax 18mm

www.loudspeakerdatabase.com

They go very low for their size, relative easy to drive (especially 8 Ohms one but of course it eats more amplifier power then 4 Ohms one), very linear and pretty good excursion rates and max SPL levels while not costing to much. So I really liked those.
You are of course free and encouraged to search more.
And if you want to keep going with pasive diffuser inside of other one take a look at this one:

Dayton Audio

Best regards and have a nice time!

Edit: ufff now you made me think about upgrading my own subwoofer's driver's. Luckily all do great those aren't available where I live.

 

[Geertidow]

And if I go back to 2 driver subwoofer in one cabinet. Does that change the calculations (except the resistance)?

 

[voodooless]

And if you want to keep going with pasive diffuser inside of other one take a look at this one:

Dayton Audio

Best regards and have a nice time!

Note that you need at least two PRs of equal size to the powered woofer to handle the excursion of the PRs. Or use a PR one size larger, 12” PR for 10” woofer.

Also note that Dayton itself has some nice 10” woofers, notably the reference HO and HE and Ultimax series.

 

[ZolaIII]

And if I go back to 2 driver subwoofer in one cabinet. Does that change the calculations (except the resistance)?

Well two drivers will give you future 7~10 Hz extension to 0,-3,-6 dB and overall boost of about 3 dB. The cabinet volume is big enough for two. I would rather try with one and pasive diffuser and build another equal cabinet for second one if that goes great. Would probably stay with 8 Ohms subwoofer drivers and use another Hypex module for second one but that's me.

 

[ZolaIII]

Note that you need at least two PRs of equal size to the powered woofer to handle the excursion of the PRs. Or use a PR one size larger, 12” PR for 10” woofer.

Also note that Dayton itself has some nice 10” woofers, notably the reference HO and HE and Ultimax series.

Don't really know, find those Acoustic Elegance IB10AU almost incredible for their size (including distortion and Faradey ring's).
Feal free to search and propose better/cheaper/or a combo of the two. Availability is a bit low on those I proposed.