Help with fomo - JBL 4645C Subwoofer

[Rahan]

Good choice. With the hight sensitivity you'll have enough headroom. I wish you to have fun, and I'm sure you'll have!

 

[g_t_r]

That was my idea. Especially as I have 2 such subwoofers. Probably amp will come to me after weekend it will be interesting.

 

[g_t_r]

P.S. does anybody know if crown xls 2502 has so called B6 alignment? Or do I need still some separate processor?

 

[Audio Science Pal]

P.S. does anybody know if crown xls 2502 has so called B6 alignment?

I was wondering that myself when I read your post yesterday. I browsed through the (online download) owners manual but did not find a specific reference. The XLS does have adjustable crossovers and maybe more choices as you scroll down its menus. Some of their other DSP amps have pre-loaded settings for certain PA speakers. Will be interesting to learn more about the XLS series.

 

[smygolf]

Do you have any form of dsp in your setup ? (not counting the amp)
Honestly, i a normal romm and 2 subs i doubt you will need it.

 

[Rahan]

Yes he will need a correction if he wants to go down to 20 hz. Without it you'll barely approach 30Hz. 2 sub won't change it.
sadly the XLS serie don't have speaker preset. Here what you have : PureBand™ Crossover Filter System:
The PureBand Crossover System provides a variable state Linkwitz-Riley 24dB/octave filter allowing you to choose a point between 30Hz and 3kHz on standard 1/12th
octave centers. Three filter types are available: Low Pass, High Pass and Band Pass

The PeakX
Limiters provide your amplifier and system with higher performance and better protection. They are specifically tuned to work with this amplifier design and
power-supply to achieve higher SPL with less audible artifacts while protecting your loudspeaker investment.

 

[Andysu]

I did some testing way back and i found it better to let dirac sort it out.
Highpass on subs, red graph, black front speakers

I can let them go to 19hz but i often watch movies at reference lvl and i want them to survive.

Intro edge of tomorrow, mick 1 meter from the baffle wall between the subs.
I let the sweep run for 1/10 of sec then i immediately turned down the volume
Looks fancy but there is like 4000% distortion due to hitting x-mech and it sounded Awful - but they survived
Done with an Umik in high dB setting but i dont really think i was hitting 130dB@20hz - 30hz Yes but not 20

Old Emilar horns on top are not in use, i am to lazy to take them out and fill the holes
The wall has a slight curve hence the strange bend in the pic

edge no snags unless playing it at silly db levels

all JBL pro cinema THX here

edge big deal just like using series of sine wave tones on REW multi tones the signals are carried in centre channel and LFE.1 if got a proper set up that doesn't use bass diverted away from LCRS towards the sub that is not how its done if using proper cinema grade speakers
spectrum lab in-room JBL 4645/4645c

 

[smygolf]

Yes he will need a correction if he wants to go down to 20 hz. Without it you'll barely approach 30Hz. 2 sub won't change it.
sadly the XLS serie don't have speaker preset. Here what you have : PureBand™ Crossover Filter System:
The PureBand Crossover System provides a variable state Linkwitz-Riley 24dB/octave filter allowing you to choose a point between 30Hz and 3kHz on standard 1/12th
octave centers. Three filter types are available: Low Pass, High Pass and Band Pass

The PeakX
Limiters provide your amplifier and system with higher performance and better protection. They are specifically tuned to work with this amplifier design and
power-supply to achieve higher SPL with less audible artifacts while protecting your loudspeaker investment.

I was on the way to say i beg to differ.
But then again i have my subs in a baffle wall.
Without B6 i still reach down to 20h

I dont have any measurements left without the wall, but as you say 30hz is about as low as it gets

 

[Rahan]

Sure in wall set up is way superior for many reason. I assumed g_t_r used his subs in a more usual way, like I do. Thank you for graphs . This is quite impressive. It makes me think about a possible evolution!

 

[Andysu]

I was on the way to say i beg to differ.
But then again i have my subs in a baffle wall.
Without B6 i still reach down to 20h

I dont have any measurements left without the wall, but as you say 30hz is about as low as it gets

use pink noise , move the mic sideways sideways up and down small length of the width you'll see the frequency go , up and down ,, you must keep the mic 100% level while moving it up and down small width over the seating , otherwise those graphs should be totally 100% overlaid transparent , but the speakers are a mess even speakers costing millions are rubbish

you got to start all over again , it can take days or weeks so keep at it your getting close
those are matching LCR at same height level behind projection screen ?

b6 25hz

 

[smygolf]

use pink noise , move the mic sideways sideways up and down small length of the width you'll see the frequency go , up and down ,, you must keep the mic 100% level while moving it up and down small width over the seating , otherwise those graphs should be totally 100% overlaid transparent , but the speakers are a mess even speakers costing millions are rubbish

you got to start all over again , it can take days or weeks so keep at it your getting close
those are matching LCR at same height level behind projection screen ?

b6 25hz

You totaly lost me here, what are you trying to say ?

 

[g_t_r]

@Rahan, you are right, but do you feel any bass extension issue in normal listening environment? (=I mean in practice?). Is there such a feeling at all?

 

[Rahan]

Do you mean with and without B6 alignment? I don't feel any bass extension issue without. But once you tried with you can't go back. 10 extra Hz in the low end might seems not a big deal but it is, especially for movies. Or do you mean in wall vs outside of the wall? If so, I lack of comparaison. But I have no issue whatsoever. I only have one sub, so my sweet spot is quite narrow but it's fine for my use.

 

[g_t_r]

Do you mean with and without B6 alignment? I don't feel any bass extension issue without. But once you tried with you can't go back. 10 extra Hz in the low end might seems not a big deal but it is, especially for movies. Or do you mean in wall vs outside of the wall? If so, I lack of comparaison. But I have no issue whatsoever. I only have one sub, so my sweet spot is quite narrow but it's fine for my use.

I meant eventually without B6 if I will face a challenge to find such settings in crown amp / until I will use some external DSP (actually I haven't plan to be honest, as this setup goes to music more than cinema ). So in case of music this (+/-) 10Hz should not be that critical. I will connect the subs over next weekend.

 

[sahil fardeen]

Thank you all for help! Finally I bought today single CROWN XLS 2502 to power my 2xJBL 4645c subwoofers. Hopefully this will work fine

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any updates? i just ordered the 4646C and is curious to know how its sounds…yet to buy amp and its making me confused which model to go for…

 

[Rahan]

Have you already a couple of options you think about? The crown XLS 1502 bridged works just fine for me. I have plenty of head room. I guess the 1002 could be sufficient most time depending of your room size.

 

[sahil fardeen]

Xls 1502 would be fine but with a real DSP before. If you don't you won't have much below 30Hz. If I understand you want to use like a high level input you can find on sub power plate. ?

I am very confused which amp to go for…..i am also restricted in budget….
i have the order placed for 4645C and the amp model i have to decide
From what i know its better for me to go for amps which have .775V sensitivity as i am using a denon 7200w. So i dont think crown xti 1000(which was ideal as it has the filters inbuilt for 4645C) would work for me due to 1.4V….Now the option is limited to either amps like Xli 1500,2500 or xls 1502 or 2502 which has .775V. Problem with xli is no dsp, not even basic hpf and lfp. Problem with xls is the hpf doesnt go below 30hz and no B6(not having B6 wouldn’t been an issue if xls had hpf of 20hz). If for instance i do not engage any hpf i will definitely good bass till 20hz but risk damaging the woofer.. if i use the 30hz hpf i loose a lot of information below 30hz….not having b6 is one thing and using a 30hz hpf on top of that…i can expect some serious drop off below 30hz i guess….
Would you think the xti 1002 would work for me in my case? only concern is my avr wont have enough voltage to drive it to required output(i did a calculation of the output i would get with my preouts emitting the max voltage turned out it cannot drive the amp more than 300-500w though with bridged xti1002 is rated for 1000w) Else it was perfect for this sub.

 

[sahil fardeen]

I am very confused which amp to go for…..i am also restricted in budget….
i have the order placed for 4645C and the amp model i have to decide
From what i know its better for me to go for amps which have .775V sensitivity as i am using a denon 7200w. So i dont think crown xti 1000(which was ideal as it has the filters inbuilt for 4645C) would work for me due to 1.4V….Now the option is limited to either amps like Xli 1500,2500 or xls 1502 or 2502 which has .775V. Problem with xli is no dsp, not even basic hpf and lfp. Problem with xls is the hpf doesnt go below 30hz and no B6(not having B6 wouldn’t been an issue if xls had hpf of 20hz). If for instance i do not engage any hpf i will definitely good bass till 20hz but risk damaging the woofer.. if i use the 30hz hpf i loose a lot of information below 30hz….not having b6 is one thing and using a 30hz hpf on top of that…i can expect some serious drop off below 30hz i guess….
Would you think the xti 1002 would work for me in my case? only concern is my avr wont have enough voltage to drive it to required output(i did a calculation of the output i would get with my preouts emitting the max voltage turned out it cannot drive the amp more than 300-500w though with bridged xti1002 is rated for 1000w) Else it was perfect for this sub.

xls 1502/2502+ minidsp 2x4hd would cost me a bit(around the same as getting an xti 4002). Or even xli 2500+2x4Hd. I dont think apart from this or xti 1002 there is any real option for me, with xti 1002 being the cheapest

 

[Rahan]

The xti sounds a good idea do you buy brand new or used? The sensitivity issue is a real one. How big is your room?

 

[sahil fardeen]

The xti sounds a good idea do you buy brand new or used? The sensitivity issue is a real one. How big is your room?

yea am from india buying everything brand new here with warranty.
My room is 21*15*10 ft
Planning to use a single 4645C dead center of front wall width, placed in the floor…
Speakers are 3153 Jbls which are awesome