Adding Subwoofer to 2CH setup (High pass XO) - AVS Forum
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post #1 of 12 Old 06-12-2012, 11:00 PM - Thread Starter
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I plan to use a pair of bookshelves coupled with a sealed sub for 2ch crossed at around 60-80hz. The sub is a passive one, so I plan on using an outboard amp, a bridged ATI 1502. The amp doesn't have any volume control or high pass XO as with a typical sub plate amp. Thus, I need some sort of high pass and low pass crossover to use the sub in conjunction with the bookshelves. I was looking into the NHT X2 and the Paradigm X30 as well as the Velodyne SMS-1. I am slightly hesitant to adding more things to the signal chain, but it seems like the only way. Each unit has there pros and cons, especially with the SMS-1's very spartan high-pass crossover (@80hz 6db/slope). I had also looked into the mini-dsp, looks slightly complicated but will this be fruitful for my setup? I have a tube pre with a 650ohm output impedance. Will this match well with the 6kohm impedance of the minidsp?

Thus my question: is there a better unit for my needs? or should I just scrap this and buy a sub amp and using the high and low pass XO's in those.
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post #2 of 12 Old 06-13-2012, 08:15 AM
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You have listed the obvious candidates/options and I would not worry about adding things to the system as a crossover is necessary.  Most dedicated sub-amps are of no higher quality and usually less than what you are proposing.  (BTW, I have a spare X30, if you decide to go in that direction.)


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post #3 of 12 Old 06-13-2012, 08:57 AM
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Originally Posted by aboroth00 View Post

I plan to use a pair of bookshelves coupled with a sealed sub for 2ch crossed at around 60-80hz. The sub is a passive one, so I plan on using an outboard amp, a bridged ATI 1502. The amp doesn't have any volume control or high pass XO as with a typical sub plate amp. Thus, I need some sort of high pass and low pass crossover to use the sub in conjunction with the bookshelves. I was looking into the NHT X2 and the Paradigm X30 as well as the Velodyne SMS-1. I am slightly hesitant to adding more things to the signal chain, but it seems like the only way. Each unit has there pros and cons, especially with the SMS-1's very spartan high-pass crossover (@80hz 6db/slope). I had also looked into the mini-dsp, looks slightly complicated but will this be fruitful for my setup? I have a tube pre with a 650ohm output impedance. Will this match well with the 6kohm impedance of the minidsp?
Thus my question: is there a better unit for my needs? or should I just scrap this and buy a sub amp and using the high and low pass XO's in those.

Your alternative list seems to lack insight and practicality. 2 of the 3 devices are not being sold as new products these days, and the remaining one isn't really a crossover but includes a room/speaker tuning system including calibrated microphone. Nothing wrong with that, but this is so conceptially and practically different from the others that mentioni of it in a comparison taxes my imagination.

Your fears about adding more electronics also show a lack of insight. If you knew how long the chain of audio gear was that produced the recordings you listen to, you'd probably curl up and die of hysteria if you are concerned about trivial things like this! ;-)

The SCS-1's choice of 80 Hz crossover is more or less of a concern depending on what exactly your bookshelf speakers actually are. And again showing a lack of insight to the nature of the problem you're trying to solve, you didn't mention that! The 80 Hz number is also more or less of a concern depending on where the subwoofer is going to be placed with respect to the main speakers and your listening position.
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post #4 of 12 Old 06-13-2012, 12:24 PM
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Definitely check out the Mini DSP 2 X 4. Many DIY subwoofer enthusiast use these with their builds. Sure, it has more features than you need with the EQ, but it does provide robust crossover capabilities and at a good price. And then later on, you'd have the option of getting a mic and doing some EQing of your sub.

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post #5 of 12 Old 06-13-2012, 04:03 PM - Thread Starter
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Quote:
Originally Posted by arnyk View Post

Your fears about adding more electronics also show a lack of insight. If you knew how long the chain of audio gear was that produced the recordings you listen to, you'd probably curl up and die of hysteria if you are concerned about trivial things like this! ;-).
I know right wink.gif. It's scary to think about so I won't think about it. I guess was battling over the use of an active vs. a passive XO. A passive XO from a reputable company such as Marchand is most appealing but the price point just isn't. I'm still wrestling over what to use to cross the main speakers with which is most important. Both the X30 and X2 allow active config of the HP XO and allow much steeper slopes. The SMS-1, I believe is using a 1st order passive XO which is thus locked into the 80hz 6db/slope(unless someone can correct me). I'm concerned with needless A/D, D/A conversions in active crossovers. Can anyone enlighten me of how the SMS-1 actually high crosses?
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Originally Posted by arnyk View Post

The SCS-1's choice of 80 Hz crossover is more or less of a concern depending on what exactly your bookshelf speakers actually are. And again showing a lack of insight to the nature of the problem you're trying to solve, you didn't mention that! The 80 Hz number is also more or less of a concern depending on where the subwoofer is going to be placed with respect to the main speakers and your listening position

My problem is adding a subwoofer and adding a high-pass. I'm sure many purists battle with the same thing. I chose the arbitrary 80hz number because of the SMS-1's inability to change its HP XO. My bookshelves are -3db @ 45hz so crossing anywhere from there up would be satisfactory of course avoiding localization. Placement and the actual XO point (if I can change it) will be of a concern when I actually place them in my room. But it's probably going to be where my previous sub was (which gave the flattest response) at the previous XO point I used (80hz) verified by in-room measurements. Of course some eq here and there doesn't hurt.

Another option entirely is to not put the XO in the chain and allow the bookshelves to play to their lowest point (they're sealed), and they will gradually roll off. Adding the subwoofer at this point is easier accomplished due to the lack of the need of a HP. However, will this be advantageous? I guess one issue comes to mind is the fact that a sub can play lower frequencies at the cutoff of the bookshelf with lower distortion as the bookshelves' woofers are experiencing higher excursion.
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post #6 of 12 Old 06-13-2012, 04:08 PM - Thread Starter
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Originally Posted by cel4145 View Post

Definitely check out the Mini DSP 2 X 4. Many DIY subwoofer enthusiast use these with their builds. Sure, it has more features than you need with the EQ, but it does provide robust crossover capabilities and at a good price. And then later on, you'd have the option of getting a mic and doing some EQing of your sub.

The myriad of options is definitely appealing. I was initially concerned with the need of the minidsp(6kohm) for low input impedance and the relatively high? output imedance of 650ohm. Will the signal be attenuated? Will this be okay? I'm actually not too sure on this issue.
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post #7 of 12 Old 06-14-2012, 09:10 AM
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Quote:
Originally Posted by aboroth00 View Post

The myriad of options is definitely appealing. I was initially concerned with the need of the minidsp(6kohm) for low input impedance and the relatively high? output imedance of 650ohm. Will the signal be attenuated? Will this be okay? I'm actually not too sure on this issue.

Neither of those specifications are particularly unusual neither should they cause you any serious concern.
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post #8 of 12 Old 06-14-2012, 06:55 PM
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First, I would offer up the suggestion that you run your bookshelf speakers full range and use the low-pass filter built in to the plate amp to determine the proper crossover for the sub. It's not an uncommon approach for two channel setups. Rel recommends it. I've used it successfully with my previous PSB bookshelf speakers and current Focal towers. Provided that you don't intend to listen to a lot of movies or pipe organ music (both with significant low frequency output) or listen an extremely high levels you might find that you really enjoy the setup and don't have to insert anything into the signal chain.

But I don't blame you for wanting to get a high pass crossover into the circuit. My current setup won't allow for it but if I could I probably would. My suggestion, which might not end up being the most economical solution, is to first purchase the mini-dsp. You can use it to determine the exact crossover frequency and slope which works best with your setup. If you don't feel the mini-dsp does much harm to your signal chain...you're done.

If you like what the mini-dsp does regarding bass management but don't like what it does to the rest of the signal you can pass on the specs from the mini-dsp to someone like Marchand and have a really nice passive filter made to your specifications. Think of the mini-dsp as the price of ensuring you order the right crossover from Marchand and again...if you are happy with the mini-dsp alone, you're done!

As I said previously, I don't have the option of an outboard crossover (my integrated lacks pre-out/main-in jacks) but if I did this is what I would do.
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post #9 of 12 Old 06-14-2012, 07:06 PM
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One more suggestion...M&K made passive crossovers for use with their subwoofers. My specs may be off but I think the LF-1 was fixed at 100Hz with a slope of 12/db per octave, the HP-80 was 80Hz with a slope of 12/db per octave and the VF-80 was 80Hz with a slope of 9/db per octave. You can find these on eBay periodically for about 50-75 bucks (HP-80 anyways).
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post #10 of 12 Old 06-15-2012, 08:21 AM
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Quote:
Originally Posted by aboroth00 View Post

The myriad of options is definitely appealing. I was initially concerned with the need of the minidsp(6kohm) for low input impedance and the relatively high? output imedance of 650ohm. Will the signal be attenuated? Will this be okay? I'm actually not too sure on this issue.

Sorry. I don't know the answer to that. But if you don't get the answers you need here, you can try the AVS DIY forum. They have a lot of experience with hooking up EQs with passive subwoofers.

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post #11 of 12 Old 06-15-2012, 09:13 AM
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Quote:
Originally Posted by aboroth00 View Post

My problem is adding a subwoofer and adding a high-pass. I'm sure many purists battle with the same thing.

Depends whether you are an rational purist or an irrational purist.
Quote:
I chose the arbitrary 80hz number because of the SMS-1's inability to change its HP XO. My bookshelves are -3db @ 45hz so crossing anywhere from there up would be satisfactory of course avoiding localization. Placement and the actual XO point (if I can change it) will be of a concern when I actually place them in my room. But it's probably going to be where my previous sub was (which gave the flattest response) at the previous XO point I used (80hz) verified by in-room measurements. Of course some eq here and there doesn't hurt.

It is easy enough to eq either the input or the outputs of the crossover.
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Another option entirely is to not put the XO in the chain and allow the bookshelves to play to their lowest point (they're sealed), and they will gradually roll off.

This scarifies one of the big advantages of a sub, which is keeping the LP out of the mains so that they are cleaner.
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Adding the subwoofer at this point is easier accomplished due to the lack of the need of a HP.

I would say it is harder because the crossover gives you more control when it controls the signal that is sent to both speakers.

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However, will this be advantageous?

Utterly disadvantageous!
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I guess one issue comes to mind is the fact that a sub can play lower frequencies at the cutoff of the bookshelf with lower distortion as the bookshelves' woofers are experiencing higher excursion.

Exactly!
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post #12 of 12 Old 06-18-2012, 08:54 AM
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What's your pre-amp?

I wanted 2.1 so I chose the Parasound 2100 as my pre. It has 80Hz HP and variable LP for the sub-out.

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