Help with fomo - JBL 4645C Subwoofer

[sahil fardeen]

not just that, i am planning to use rca to xlr cable, as my preouts are rca(xti offers only xlr inputs) I was told that the input sensitivity halves when using inputs this way(rca to xlr)…that means 2.8V sensitivity instead of 1.4V when using xti. So i may only be able to extract like 20% of xti’s output.
On the contrary, my denon preouts are really solid(i know as i have owned various good marantz and yamahas). The 7200w denon does put out a strong signal comparitively and my present home audio subs require lesser gain in amp…
The issue is i cant find the exact voltage numbers anywhere…some source quote1.2V for all denons some say it exceeded even 2 or 4V in preouts

 

[Rahan]

Honestly I think you'd better save a bit more and buy or a XLS or xli + mini DSP combo to be sure you'll have enough headroom. But if you listen at low volume you might be ok with the xti at low sensitivity. If you can sand it back, Give it a try .

 

[sahil fardeen]

Honestly I think you'd better save a bit more and buy or a XLS or xli + mini DSP combo to be sure you'll have enough headroom. But if you listen at low volume you might be ok with the xti at low sensitivity. If you can sand it back, Give it a try .

thanks buddy

 

[sahil fardeen]

Honestly I think you'd better save a bit more and buy or a XLS or xli + mini DSP combo to be sure you'll have enough headroom. But if you listen at low volume you might be ok with the xti at low sensitivity. If you can sand it back, Give it a try .

and by the way, i hope you are happy with 4645C, i come from typical home audio subs like the svs ultras i hope it will be a huge upgrade

 

[g_t_r]

and by the way, i hope you are happy with 4645C, i come from typical home audio subs like the svs ultras i hope it will be a huge upgrade

I don't writing anything as I don't have yet full blown opinion (haha). I connected both subwoofers to crown xls 2502. Couple of observations for further study:

1. Crown has HPF / LPF filter, so I've set LPF to 80Hz, but lowest value for HPF is 30Hz, that's too high for me for subwoofer use. So I've set only LPF to 80Hz w/o HPF. Which is basically not good for the woofer (np HPF), but we are going here to 2nd issue:
2. When I see different videos on YT, I see subwoofers moves like crazy, even here:

but nothing like this is happening on my end, I'm almost unable to see any move. When I will touch the woofer It is vibrating.
3. I'm stealing the signal via RCA input, so I've set this lower sensitivity settings (0.75 vs. 1.4V). Maybe that's somehow wrong.
4. Nevertheless the sound of the bass is very clean and nice to the ear / well matching with other JBL speakers I have, so not typical boomy car audio or home audio sloooow sub sound.
5. But still biggest "mystery" is that with such parameters like >130dB something of SPL I basically thought I will be blown away by sound pressure in my room in normal home listening env., whereas I have troubles to hear if those subs are playing / moving. I mean - I hear that they are playing, but... you understand my concern. Volume on the crown is set to the max on both channels, but signal is still proportionally taken from music which is playing. So when I'm listening in normal home volume (not concert level). I cannot hear any kind of "hit"/impact, despite the fact that sub is adding some lower notes.

Strange, any thoughts?

 

[Rahan]

Obviously, you're limited in terms of high SPL (even with the two subs and the +3dB they give) . The 2502 provides 2x 440W under 8 ohms, meaning 440W per channel. These speakers can handle at least twice that power.

The input may also slightly attenuate the signal, even with high sensitivity selected. What preamp are you using?

What is the sensitivity of your main speakers? how do you power them? The 4645C is quite high sensitivity (97dB), though.

Finally, remember that human hearing is not linear at all. At low sound levels, we are much less sensitive to bass frequencies. That’s why the LOUDNESS feature was created to compensate for this effect. For example, if you adjust everything to sound good at 85dB, the bass will feel much weaker at lower volumes.

That being said, it’s still strange to me that you barely hear your subs. I can assure you that there’s no doubt when mine is turned on.

 

[g_t_r]

PRE is RME ADI2 DAC (variable output), so RCA goes to Crown and XLRs to power power amp to main speakers. As I wrote, I need to try couple of additional options/ placement etc. However interesting, I doubt it is typical under-power condition, more some gain issue. I doubt I can utilize such amount of power even single crown xls2520 can offer. My point is that I was expecting that I will be struggling more that those subwoofers will be too loud / brutal or bringing too much attention to themselves, whereas what I've got is super elegant /cultural sound So form that angle I'm not disappointed, perfect integration with main speakers. But... still no idea how I can add this famous +6dB GAIN to go flat down to 20Hz. What device to use between typical stereo pre and crown.

 

[Rahan]

Yes indeed the 4645c is a very subtle and very detailed sub. It also can knock you out when needed! There is something I don't understand: why don't you use the XLR output of the RME? You ask ass well how to do the correction before the amp, but this is one of the great thing about the RME adi dac : the DSP. Is there something I missed?

 

[sahil fardeen]

PRE is RME ADI2 DAC (variable output), so RCA goes to Crown and XLRs to power power amp to main speakers. As I wrote, I need to try couple of additional options/ placement etc. However interesting, I doubt it is typical under-power condition, more some gain issue. I doubt I can utilize such amount of power even single crown xls2520 can offer. My point is that I was expecting that I will be struggling more that those subwoofers will be too loud / brutal or bringing too much attention to themselves, whereas what I've got is super elegant /cultural sound So form that angle I'm not disappointed, perfect integration with main speakers. But... still no idea how I can add this famous +6dB GAIN to go flat down to 20Hz. What device to use between typical stereo pre and crown.

you definitely need more power….i was even doubting a single 2502 bridged(1500w) would do the job for me…. these require a hell lot of power to truly hit you.
And you are running it in stereo which severely limits the power, and your input voltage may not be enough to hit the rated 450w…you maybe actually getting barely 200w to the subs due to low input voltage…and using an hpf of 30hz severely drops off the output of 20-30hz region all this adds up to your issue
For instance try setting the input sensitivity to .775V with hpf off and try bridging your 2502 to a single 4645C…try it first and i am sure it will be way better.
And turning off hpf you only have to worry about extreme scenes like edge of tomorrow. Rest of scenes upto 20hz the 2242hpl woofer in the sub it will handle easily. Not to mention to power required to destroy them at that frequency is very high and you dont have it anyway.

 

[sahil fardeen]

PRE is RME ADI2 DAC (variable output), so RCA goes to Crown and XLRs to power power amp to main speakers. As I wrote, I need to try couple of additional options/ placement etc. However interesting, I doubt it is typical under-power condition, more some gain issue. I doubt I can utilize such amount of power even single crown xls2520 can offer. My point is that I was expecting that I will be struggling more that those subwoofers will be too loud / brutal or bringing too much attention to themselves, whereas what I've got is super elegant /cultural sound So form that angle I'm not disappointed, perfect integration with main speakers. But... still no idea how I can add this famous +6dB GAIN to go flat down to 20Hz. What device to use between typical stereo pre and crown.

Best would be to use a minidsp 2x4hd btw crown and pre…or incase your pre has dsp/PEQ you can apply a +6Db boost at 25hz, Q=2 and steep cut 20hz and below..as recommended by jbl

 

[g_t_r]

I will provide more updates soon (temporary busy by some regular non-audio topics ) ... but indeed- couple of great ideas brought, like for example bridge XLS2520 into one SUB etc. I was worried about HPF by looking how strong the sub transducer was moving on YT videos, in my home case it is unlikely I will break anything . Why I used RCA for sub from RME? well, because main XLR output goes to main power amp to front speakers. Ofc I can still try opposite way - connect subwoofer via XLR and use RCA to power amp, but it would be some degradation to overall sound (I have better XLR cables if it matters on this forum )

 

[smygolf]

Is a bridged Xti2002 to expensive ?
I think it has all you need in Dsp/crossover.

CDi 1000 that i use and Xti should have the same features.

 

[Rahan]

I will provide more updates soon (temporary busy by some regular non-audio topics ) ... but indeed- couple of great ideas brought, like for example bridge XLS2520 into one SUB etc. I was worried about HPF by looking how strong the sub transducer was moving on YT videos, in my home case it is unlikely I will break anything . Why I used RCA for sub from RME? well, because main XLR output goes to main power amp to front speakers. Ofc I can still try opposite way - connect subwoofer via XLR and use RCA to power amp, but it would be some degradation to overall sound (I have better XLR cables if it matters on this forum )

Yes try the XLR out for the subs won't cost anything.

For the cable part: This forum is about sciences. It should answer the question

you definitely need more power….i was even doubting a single 2502 bridged(1500w) would do the job for me…. these require a hell lot of power to truly hit you.
And you are running it in stereo which severely limits the power, and your input voltage may not be enough to hit the rated 450w…you maybe actually getting barely 200w to the subs due to low input voltage…and using an hpf of 30hz severely drops off the output of 20-30hz region all this adds up to your issue
For instance try setting the input sensitivity to .775V with hpf off and try bridging your 2502 to a single 4645C…try it first and i am sure it will be way better.
And turning off hpf you only have to worry about extreme scenes like edge of tomorrow. Rest of scenes upto 20hz the 2242hpl woofer in the sub it will handle easily. Not to mention to power required to destroy them at that frequency is very high and you dont have it anyway.

Wow! You were doubting a single 2502 bridged would do the job? Man, how big is your room? In my basement witch is 40 m square. A have a single 1502. the mini DSP input is set to -11db for the sub to match The other speakers. The overall output on is -20 dB for movies. it is pretty damn loud! I've never tried more than -12 dB ! I worried about walls! It can handle a ton of power, sure, but it's 97dB sensitive ! Keep in mind with max power it can deliver 128 dB! Nobody wants that in a domestic environment!

 

[Rahan]

Best would be to use a minidsp 2x4hd btw crown and pre…or incase your pre has dsp/PEQ you can apply a +6Db boost at 25hz, Q=2 and steep cut 20hz and below..as recommended by jbl

Pretty sure it will solve your problem. It sounds super "shy" without the correction.

 

[sahil fardeen]

I will provide more updates soon (temporary busy by some regular non-audio topics ) ... but indeed- couple of great ideas brought, like for example bridge XLS2520 into one SUB etc. I was worried about HPF by looking how strong the sub transducer was moving on YT videos, in my home case it is unlikely I will break anything . Why I used RCA for sub from RME? well, because main XLR output goes to main power amp to front speakers. Ofc I can still try opposite way - connect subwoofer via XLR and use RCA to power amp, but it would be some degradation to overall sound (I have better XLR cables if it matters on this forum )

well, the video you saw where the cone was moving that much was something like a bassatronic music(for eg the song:bass i love you). It has super deep notes like under 10hz just to record videos of cone moving very rapidly(very common in car sub demos) so thats expected the cone to move that much. With normal material i highly doubt it would move even half of that unless it’s something infamous like intro to Edge to tomorrow or world war Z grenade scene…This thing is hard to damage, having quite high Xmech. Although its precautious and still recommended to use a 20hz hpf.

 

[sahil fardeen]

Is a bridged Xti2002 to expensive ?
I think it has all you need in Dsp/crossover.

CDi 1000 that i use and Xti should have the same features.

Only issue is 1.4V input sensitivity that i fear wont be enough to drive the amp to required output. Budget is fine

Whereas xls and xli are excellent in that regard, .775V selectable input sensitivity.

 

[sahil fardeen]

Yes try the XLR out for the subs won't cost anything.

For the cable part: This forum is about sciences. It should answer the question

Wow! You were doubting a single 2502 bridged would do the job? Man, how big is your room? In my basement witch is 40 m square. A have a single 1502. the mini DSP input is set to -11db for the sub to match The other speakers. The overall output on is -20 dB for movies. it is pretty damn loud! I've never tried more than -12 dB ! I worried about walls! It can handle a ton of power, sure, but it's 97dB sensitive ! Keep in mind with max power it can deliver 128 dB! Nobody wants that in a domestic environment!

Well, my room is a bit small than yours, just under 30 m square, its a dedicated room with concrete walls and no windows. And No, the reason i was suspicious whether the xls2502 bridged will do the job is only because of the low voltage from my denon. AFAIK, the max voltage output from denon can only drive any crown amp to 30% power.

I know definitely if the amp is driven to full power it will blow my home away but thats not going to happen in my case(due to low voltage)if my speculations are right.

And a good news to mention, Amazon here in India accepts returns so i have an xti 1002 on order, already have the 4645C on order too.
So it will definitely end my dilemma if the voltage issue is definitely as serious it is. Else i will return it and go for xls or xli bridged+minidsp 2x4HD. Minidsp is capable of outputing 2V clean and on top of that i can apply 25hz Boost and 20hz hpf as well. With the option to tune it more to my liking like house curves.
Will provide the update once i get both the subs and amps. Mostly by this saturday

 

[sahil fardeen]

Pretty sure it will solve your problem. It sounds super "shy" without the correction.

Yep, specially if we are accustomed to subs like ported svs which has good output below 30hz

 

[smygolf]

Only issue is 1.4V input sensitivity that i fear wont be enough to drive the amp to required output. Budget is fine

Whereas xls and xli are excellent in that regard, .775V selectable input sensitivity.

I did not even think of it, i have a BSS active filter before my amp, only used to boost the signal.
But i dont think i need it with the CDi

 

[sahil fardeen]

I did not even think of it, i have a BSS active filter before my amp, only used to boost the signal.
But i dont think i need it with the CDi

i have an xti 1002 on order…. let’s see if it will work out. Fingers crossed