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Discussion Starter #1
What is the best option regarding the sound: Two subs in parallel (mono 4ohms) and 1x500W, or 2subs 8ohms stereo 2x200W?

I have built two BR subs with BMS 12S330, 8ohms, 60 litres/ 33Hz -3dB. I will use DSP and cross at 60 - 80Hz.

Subs are intended for music only! I consider Hypex Ncore FusionAmp FA501 1x500W 4ohms or FA252 2x200W/8ohms.

P.S. I asked Hypex the same question, sadly no answer.

Cheers Predrag
 

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Discussion Starter #3
Absolutely right and spot on. And better damping factor 8ohms vs 4ohms. But question remains regarding less power per channel. Calculations and measurements show sound pressure of 103dB at 30Hz with both subs and 2x200W without EQ. I have to tame the peaks and dips almost + / -20dB the EQ of which will probably suck 200W quite easily.

173903

Predrag
 

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Perhaps but some of this is probably due to cancellations between the two. Experiment with relative placement and phase before reaching a conclusion. Also, going to the 1channel 500w setup will not be significantly better at this point.
 

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Discussion Starter #5
Thanks Kal. The measurements are made with old RadioShack-33-2050 and cal. file from REW forum. Honestly, I am very disappointed with the results, but also not sure if the measurements are correct. I ordered miniDSP Umik 1 microphone, which is individually calibrated, and will repeat all measurements.

The (best) placement of 2 subs in my room is diagonally, next to the placement 10in away from the front and side walls (optimal), 20in behind main speakers.

What about adding two more subs of the same type in the corners near listening position. The gain will be 6dB, like replacing 200W with 800W amp. And all the good stuff except two more boxes in the room?

Any experience of having 4 same subs?
 

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Thanks Kal. The measurements are made with old RadioShack-33-2050 and cal. file from REW forum. Honestly, I am very disappointed with the results, but also not sure if the measurements are correct. I ordered miniDSP Umik 1 microphone, which is individually calibrated, and will repeat all measurements.
OK but I doubt the mic will make a big difference.
The (best) placement of 2 subs in my room is diagonally, next to the placement 10in away from the front and side walls (optimal), 20in behind main speakers.
Best how? Have you tried other positions or are there, ummm, environmental constraints? Can you measure them individually?
Any experience of having 4 same subs?
Nope. I am up only to 3 in each system.
 

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Discussion Starter #7
Best how? Have you tried other positions or are there, ummm, environmental constraints? Can you measure them individually?
Yes, sure I have limitations. I cannot place them neither in the center of the room nor in the middle of side walls. No big difference between best (diagonal) and optimum (corners 10in of the wall) position.

Big difference in plots when I changed calibration files in REW for RadioShack-33-2050!

If the measurements with Umik 1, shows the same rollercoaster graph, then I am probably doomed. I don´t get it: I have 32 acoustic elements in my room, each addressing bass region, 10 of which are big 2x4ft bass traps. The room is 16x13x8 ft. Maybe room modes are not tamed in a way they should be.

With only one sub the situation is worse - I don´t need to measure.

Big question: How deep (in dB) should I go with EQ? Should I address only peaks and not dips? I read a lot of stuff on this site regarding this issue, I think it is consent not to tame dips only peaks?
 

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Should I address only peaks and not dips?
Peaks and dips but not nulls. Low Q dips can be corrected with low Q and low amplitude EQ.

I do not know how high in frequency you plan to use your subs but, if you are using them under 100Hz, you are not in bad shape. The only concerns are the peak at ~34Hz and the sharp dip at ~47Hz. Cutting the peak is possible. A broad lift in the 42-52Hz range (one or two) may be enough to either fix the whole range including the sharp dip or, if it is a true null, leave that as such a very narrow dip that it is musically acceptable. The rest is of the <100Hz range seems amenable to standard corrections.
 

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Discussion Starter #9
Peaks and dips but not nulls. Low Q dips can be corrected with low Q and low amplitude EQ.
So, dips should be corrected too. Now the basic question remains: How much power do I need.

Please correct me if I am wrong... Each 3dB lift doubled the power. So to play 40Hz at 98dB (in my room) I would need instead of 13W (without EQ in a perfect room) more then 100W, just for this one correction.

Well, what I don´t know is, how much power in total do I need for each subsequent lifting of dip, or cutting the peak.
 

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So, dips should be corrected too.
Yes but you can usually distinguish them from nulls by being able to correct them with relatively low Q and low amplitude changes. Do the peaks first, then see how the spectrum looks. Then do the dips.

Now the basic question remains: How much power do I need.
Please correct me if I am wrong... Each 3dB lift doubled the power. So to play 40Hz at 98dB (in my room) I would need instead of 13W (without EQ in a perfect room) more then 100W, just for this one correction.
Well, what I don´t know is, how much power in total do I need for each subsequent lifting of dip, or cutting the peak.
Dunno but note that you are talking only about specific frequencies, not the entire spectrum. So, you gain amp power potential when you correct the peaks! Perhaps that will balance out the overall demand when you do the dips.
 

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Discussion Starter #11
Can´t wait to receive Umik 1 and start all over again. I will probably buy Hypex FA502 2x350W/ 8ohms just to make sure I have enough power. Anyway my average listening levels are hardly over 90dB.

Kal, you really help me a lot to clear a lot of stuff here. Will continue to post after a while, maybe that would help others too.

I wish you a Happy New Year and all the best in 2020!
Predrag
 

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Kal, you really help me a lot to clear a lot of stuff here. Will continue to post after a while, maybe that would help others too.
Happy to be able to help.
I wish you a Happy New Year and all the best in 2020!
And to you, too.
 
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