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Discussion Starter #1
I am planning to build a pair of subs, I have been playing with Winisd and so far think the Tempest X2 looks alright in about 300L tuned at 18 hz. I am open hearing other drivers or box volumes/tuning which would be better though.

Size wise it would need to be under W20" x D26" and height preferably under 50" but negotiable on that one.

To be used primarily for movies and games as my Jamos handle bass for music quite well.

I already have a EP2500 and Art Cleanbox for power duties so something that will work well with them would be good.

Thanks Ash
 

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Hi Ash, the Tempests are by far the performance for the $ kings in Australia. 300L at 18Hz looks OK.

Sonotube is called Formatube in Oz and a bit hard to get and expensive. Substituting with multiple round ports, such as 4x100mm PVC or a slot port will also work the same.

I'd also not be so quick to write off these as HT only. With your Jamos crossed out correctly, the midbass drivers will be relieved of any LF duties, reducing excursion and making them much cleaner up through the mids too and the effect can be very audible even on generic R&R at quite modest levels.
 

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Discussion Starter #4
I have been modeling using 3 slot ports at 5"x3" 32"long and am getting 27m/s at 16hz and is starting to go over excurion there aswell will I need to put a high pass filter in to reduce that, and if so what is the best thing to use that can be bought in Australia should I just get a DEQ 2496 or is there something better suited

Thanks Ash
 

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As you'll need xover capabilities as well, which the DEQ does not provide, most cost effective solution seems to be the miniDSP with the 2 way advanced plug in.

This unit has been a big hit at the local GTG's held in Sydney and Bathurst over recent months. It may not do a HPF as low as you want, but a few $ worth of passives and 10 mins worth of work and you can have a 1st or 2nd order Butterworth HPF wherever you want (passive, line level either before DSP or before amp). I'll calc out the values if you like when you give me an F3 and slope for it.
 

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Discussion Starter #6
Would the miniDSP be used instead of the 80hz crossover in my reciever and setting speakers to small? and as I am Bi-amping my L&R could it be used as a passive crossover between high and Low frequencys of them?

With 1000w input power if I add a 2nd order butterworth at 17hz I am getting 28mm excursion at 12hz is that something to worry about or is it far enough below receiver and amp rolloff that it would not actually go that high.
 

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Would the miniDSP be used instead of the 80hz crossover in my reciever and setting speakers to small?
My idea was that you would set the LP filter in the MiniDSP to whatever setting you have chosen for xover in the AVR, for example 80hz, and it would still provide a fair amount of EQ and delay if needed and is the cheaper option than the ~$A400 for the DEQ. The internal (to the AVR) LPF on the LFE channel might suffice and you just use the MiniDSP for EQ etc, not xover.
and as I am Bi-amping my L&R could it be used as a passive crossover between high and Low frequencys of them?
Do you mean passive biamping by using an AVR setting? If so, no as there is no way to get it inserted into system and still use the AVR internal amps.

If you were to remove the passive xovers from your L/R, add 4 channels of appropriate amplification and another MiniDSP and took the time and effort to set up all up correctly, you could possibly improve your mains, but I wouldn't hazard to guess whether it would be worth the money.

With 1000w input power if I add a 2nd order butterworth at 17hz I am getting 28mm excursion at 12hz is that something to worry about or is it far enough below receiver and amp rolloff that it would not actually go that high.
The Xmech is quite a bit higher than the Xmax, and the peak excursion I'm seeing with the filter in place is 38MM at 11Hz or so, not 28. In practice I doubt it will be an issue, but I don't know how loud you like it. I'll root around in my notes and see if I can get a figure for Xmech for the Tempest.

Most AVRs will have a very low LF limit as the Dolby specs are for something like 3Hz-20kHz. Some pro amps will have a higher HPF (usually just a series cap) but the figures between brands and models vary. Not sure what the EP's are as I don't use them but some googling should clarify that.
 

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Discussion Starter #8
My idea was that you would set the LP filter in the MiniDSP to whatever setting you have chosen for xover in the AVR, for example 80hz, and it would still provide a fair amount of EQ and delay if needed and is the cheaper option than the ~$A400 for the DEQ. The internal (to the AVR) LPF on the LFE channel might suffice and you just use the MiniDSP for EQ etc, not xover.Do you mean passive biamping by using an AVR setting? If so, no as there is no way to get it inserted into system and still use the AVR internal amps.

If you were to remove the passive xovers from your L/R, add 4 channels of appropriate amplification and another MiniDSP and took the time and effort to set up all up correctly, you could possibly improve your mains, but I wouldn't hazard to guess whether it would be worth the money.
All good that makes sence you were more talking about the DSP for a cheaper EQ than for the crossover then.
I am using an Elektra Theatron 7 to Bi-amp the fronts and 1 channel for each of my other 3 but thats a bit of a non issue if its easier not to screw with that.

The Xmech is quite a bit higher than the Xmax, and the peak excursion I'm seeing with the filter in place is 38MM at 11Hz or so, not 28. In practice I doubt it will be an issue, but I don't know how loud you like it. I'll root around in my notes and see if I can get a figure for Xmech for the Tempest.

Most AVRs will have a very low LF limit as the Dolby specs are for something like 3Hz-20kHz. Some pro amps will have a higher HPF (usually just a series cap) but the figures between brands and models vary. Not sure what the EP's are as I don't use them but some googling should clarify that.
I think I can see how you got 38mm, aswell as raising the input power I should have input the series resistance aswell :doh: Looking more into it the ep2500 will only output 750W into 4Ω anyway which brings it down under 30mm which hopefully wont be a problem.
 

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All good that makes sence you were more talking about the DSP for a cheaper EQ than for the crossover then.
Sure.
I am using an Elektra Theatron 7 to Bi-amp the fronts and 1 channel for each of my other 3 but thats a bit of a non issue if its easier not to screw with that.
Passive biamping eh? In your case it's costing you nothing, but you gain nothing from it either.

You could add another MiniDSP from you Pre line out as I said and you'd have more advanced EQ and potentially better implementation of xover sloes and a range of other benefits, but it will take some work. You'll learn a lot about speakers and rooms though. Too much hassle for most, but the benefits are so large that I don't bother building passive designs at all any more.

I think I can see how you got 38mm, aswell as raising the input power I should have input the series resistance aswell :doh: Looking more into it the ep2500 will only output 750W into 4Ω anyway which brings it down under 30mm which hopefully wont be a problem.
Sorry, I don't use WinISD as I prefer Unibox and it inputs the driver's rated power (1kW in this case) as default. I forgot to change it back to the EP max output.

Series resistance for the cabling won't make much difference at all, 0.25Ω or so, worst case. Keep the runs as short as practical or make them as large a gauge as you can to compensate for a long run.

I hope you'll do a build thread when you start. I'm hoping to get a pair of Tempest 2 early in the NY and run them sealed and EQ'd in about 200L.
 

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Discussion Starter #10
I hope you'll do a build thread when you start. I'm hoping to get a pair of Tempest 2 early in the NY and run them sealed and EQ'd in about 200L.
I will make a build thread planning on ordering the drivers tonight.

Is there any guides floating around about how to build a highpass butterworth filter? I can find circut diagrams and explainations of how they work but cannot find anything about how you would set them out on a breadboard or parts you need, the caps and resistors are fine but are all op-amps the same or is there a particular type I would need to use.
 

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I will make a build thread planning on ordering the drivers tonight.

Is there any guides floating around about how to build a highpass butterworth filter? I can find circut diagrams and explainations of how they work but cannot find anything about how you would set them out on a breadboard or parts you need, the caps and resistors are fine but are all op-amps the same or is there a particular type I would need to use.
You can do it passively so you need no opamps and associated PSU.

Here you go: PLLXO.

I googled but couldn't find a Zin for your poweramp, so I hope it's in your manual.
 

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Discussion Starter #12
You can do it passively so you need no opamps and associated PSU.

Here you go: PLLXO.

I googled but couldn't find a Zin for your poweramp, so I hope it's in your manual.
Thanks that will make it a little easier, the input impedance of my amp is 20kΩ on the balanced input, I am trying to work the values but am getting a -ve value for R½ am I doing something wrong here

Thanks Ash
 

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Discussion Starter #13
My Subs arrived today I will start a build thread when I get time to actually do something with them.
 

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Thanks that will make it a little easier, the input impedance of my amp is 20kΩ on the balanced input, I am trying to work the values but am getting a -ve value for R½ am I doing something wrong here

Thanks Ash
Probably got the math wrong, but I'll do it for you tonight (about to go to work). Is your pre balanced out?
 

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Discussion Starter #17
I will not be sure I need it with with the new subs untill they are built, but with my current 12's I did need to get it to bring the level up.
There is no reference to Zin in the manual but from searching around I have found it is 100K which has helped in the calculating of the filter if you could check my numbers would be appreciated.
Ramp 100k
R1 5k
C1 1.9uf
c2 190nf
R1/2 100k
R2 50k

My next issue is I can only find 1.5uf and 2.2uf caps 180nf ones I can get but can they be stacked? if they can it would be 17.6hz with 1.8uf.

Thanks Ash
 
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