Active line level crossover with subwoofer out - HELP


Hi.

Helping my friend with another challenge. 
Looking for a line level crossover. His preamp does not have a subwoofer out.

What he wants to do is have a high pass filter between the preamp and his power amp. This so his Spendor BC1’s are spared anything below 40 or 50hz. And, the crossover needs a low pass filter to spare the subwoofer the high frequencies. 
Thoughts? 
Thanks!
perkri
This will do it  the first one has dirac the second link is a cheaper version that doesn't  but will let you set crossovers.

https://www.minidsp.com/products/dirac-series/ddrc-24

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd
The simple way is a miniDSP.
The complicated way is to put a capacitor in series with the amp, and send the full range to the sub, if the sub has a low pass, and most do, you just have to match the cap to the frequency and preamp input impedance.
Otherwise, a number of people make analog crossovers for consumers, but they are rare. Bryston comes to mind.
Bryston
JL Audio
Marchand

Another possibility is a DAC-preamp with HP-LP crossover in it. They are made by Anthem, Legacy, DSPeaker, Trinnov, MiniDSP, Classe, and NAD, among others.

And as mentioned, a miniDSP unit is a path taken by many.
Thank you!!!

So, the MiniDSP looks very interesting!

Looks like it will do exactly what he wants. Read through the manual, and wondering if you might be able to help me understand the sub out portion. His subwoofer, an old Rogers unit, has both left and right channel RCA inputs. Can the unit be configured so a left and right channel can be sent to the subwoofer?

Thanks again!

P
Hey Perkri,

You can do all the filtering and mixing in the miniDSP, or you can do all the filtering and send L and R as separate signals to the sub. up to you.

I recommend you use the miniDSP, then you only have to deal with 1 delay.

Also, look at room EQ Wizard or OmniMic to measure and calibrate it.
Cool part is when you learn to EQ the bass and realize you can fix your room modes. :)
erik_squires"Cool part is when you learn to EQ the bass and realize you can fix your room modes."

EQ can not fix, correct, or eliminate room nodes the nodes will always be there all you will do is add distortion and an even more uneven net frequency response plot.
I have used this HSU high pass filter when I owned a subwoofer with no outputs to my amp!

http://www.hsuresearch.com/products/high-pass-filter.html
Dayton Audio has just introduced a new DSP bass management box, model DSP-LF. Parts Express is selling it REAL cheap: $59.99.
erik_squires"Cool part is when you learn to EQ the bass and realize you can fix your room modes."
clearthink:

EQ can not fix, correct, or eliminate room nodes the nodes will always be there all you will do is add distortion and an even more uneven net frequency response plot.
Right. Clearthink is absolutely correct OP and you would do well to listen.

The single most important factor in getting good deep articulate fast and smooth bass response is the number of drivers. The more subs the better. That includes the bass drivers in the full range pair.

The idea of improving the performance of the stereo pair by using a crossover to reduce the load on the amp and speakers, I get that. Its true. The problem is it comes at a cost. Not only the cost of the parts, being much more complex it has to cost more. But also cost in terms of sound quality. If your goal is sound quality that is not the way to go.

What you want to do instead is leave the pre alone and simply add a sub out. The simplest, easiest, and most cost-effective solution is what's called a Line Out Converter or LOC for short. Do a search, you will find them all over. 

The LOC is nothing more than 2 resistors per channel. It does nothing more than reduce speaker voltage down to line voltage, ie about 2V. You can see one here done on my Melody tube amp. https://systems.audiogon.com/systems/8367 Scroll down you will see a picture of the actual mod, two resistors per channel, you can even make out the values and copy this if you want. Or if you want a more complete description and circuit diagram go here https://www.epanorama.net/circuits/speaker_to_line.html

Unlike all the other options mentioned so far this one is true high end. It will make the system better- not different, not worse, but actually better. It is easy. And it will cost about $2. The only real questions are do you want it built in like I did, or outside? And how good do you want it to look? Mine is built in because it worked for me but that's the beauty of mods, you can do it your way. 
EQ can not fix, correct, or eliminate room nodes the nodes will always be there all you will do is add distortion and an even more uneven net frequency response plot.

clearthink (George hifi’s alt?? ) and Millercarbon lack education and personal experience in a home or professional environment with this, so their opinions are incorrect. Fortunately I have personal, home and professional experience in the motion picture industry as well as I am guided by acousticians who have written on the subject.

They’ve also failed to read multiple postings I’ve made citing appropriate links. They are guided completely by feels.

I’ll summarize my position, guided by hands on measurement, listening and acoustics:

You can use an EQ to clip resonant modes. This allows the overall subwoofer level to be lifted.

With bass traps, you can even solve nulls.

Miller is, as always,  flat out, laughably wrong. He and george number 9 will never know it though. The rest of it is so riddled with half truths and falsehoods it’s not worth attempting to dissect.

erik_squires
"
clearthink (George hifi’s alt?? ) and Millercarbon lack education and personal experience in a home or professional environment with this, so their opinions are incorrect."

You are confused, disoriented, and profoundly illogical opinions can not be "mistaken" they are opinions although in this case what we are talking about are facts also you do not know anything about my professional, academic, and scientific achievements, accomplishments, patents, and interests. 

" Fortunately I have personal, home and professional experience in the motion picture industry as well as I am guided by acousticians who have written on the subject."

You continue to remain confused, disoriented, and simply wrong.

You can add 1,000 Db of correction, you can turn on the lights in you're room as bright as you want or turn them off to absolute darkness you can play your TV loud and/or wear plaid pants the room nodes will still be their, silly!
You are confused, disoriented, and profoundly illogical opinions can not be "mistaken" they are opinions although in this case what we are talking about are facts also you do not know anything about my professional, academic, and scientific achievements, accomplishments, patents, and interests.


I know you don’t believe in acoustics, and you have yet to ever post anything with measurements, and experiments to prove your point.

You just continue to repeat tropes which were dead in the 90s.

Best,

E
OP:

I encourage you to read in the Room EQ Wizard forums, as well as Audio Science Review similar topics.

If you get a measurement microphone, and a miniDSP, I encourage you to try it out.

Best,

E

erik_squires
"
I know you don’t believe in acoustics,"

I do not know what you mean by this if you mean by "believe in acoustics" have I accepted acoustics as my own personal savior no, I have not done so nor do I plan to but of course you are free to believe, worship, and pray as you choose provided the rules of you're nation so allow.

"You just continue to repeat tropes which were dead in the 90s. "

This is just another amusing, laughable, silly retort from the same person who insist the opinions of other's are "wrong."
Millercarbon lack education and personal experience in a home or professional environment with this, so their opinions are incorrect.

Can we all, possibly even Eric, agree this is a home environment?  https://systems.audiogon.com/systems/8367 Sure looks like a home to me. In fact, living in it, yeah, sure enough, its a home! Gone off the deep end he has. Again.

But what about professional experience? Well to be honest I never have done this as my sole source of support. But I have been hired and paid to design and install systems. Its no secret. I’ve posted about it before. I’ve had multiple people come to me with questions, all assuming I am some kind of industry insider. Well I was a presenter at CES one year.

But to even have to be going there seems to me entirely the wrong approach. Either your ideas are valid and compelling, or they are not. If the ideas are solid then you should have no qualms whatsoever defending them on their own merits. The problem is this has been tried and failed, and so all eric has left is to try and shoot the messenger.

Basically what this comes down to is the classic example of do you want the best sound or do you want the best equipment. We all know eric is into equipment. Its all he ever talks about. Even when he talks about sound, its never really the sound he’s talking about but the measurement of the sound. Which isn’t quite the same thing now, is it?

So do you want a system that sounds good? Or do you want a system that looks good? Its your system. DYODD. Choose wisely.




Unfortunately, the knowledge of what can be achieved by what is almost colloquially referred to as room equalization, is limited, as is evident in this thread. Here is a quote, and a link to an article (by someone who knows far more than many posting in this thread) that shows that Erik is indeed correct (but perhaps needed to communicate a bit more info for those less knowledgeable). Equalization in the digital domain does not just mean just amplitude correction, but phase correction can be applied as well, which in bass frequencies does not present an sound quality impairment because bass cannot be localized.

http://www.acousticfrontiers.com/201163hard-proof-that-equalization-kills-room-modes-html/

The correct application of equalization to address room modes is not a straightforward subject. Historically equalization filters were calculated based on a simple inversion of the frequency response, with no consideration as to the location / Q of modal resonances, the correctability of the issue or the location of speaker boundary interference related suckouts. It is probably these simple correction filters that have caused the debate around the efficacy of equalization.

The theory behind correction of room mode resonances is described clearly by Floyd Toole:

“Room resonances at low frequencies behave as “minimum phase” phenomena, and so, if the amplitude vs. frequency characteristic is corrected, so also will the phase vs. frequency characteristic. If both amplitude and phase responses are fixed, then it must be true that the transient response must be fixed – i.e. the ringing, or overhang, must be eliminated” (Toole, The Acoustical Design Of Home Theaters, 1999)


My (limited) understanding of room nodes is that they are affected by the placement of the subwoofer (or subwoofers, as in a swarm).  If that is true, can a single mini-DSP fix the room nodes regardless of subwoofer location?  Or do you need one mini-DSP for each sub?
Not an expert on Minidsp, but I see 2 in, 4 out units readily available, so that would cover up to 4 subs.
@heaudio123   Thanks for the [email protected]_squires -- If I remember right, you are a proponent of standalone DACs (specifically Brooklyn), DIY swarms, and dedicated multichannel subwoofer amps, in addition to miniDSPs. Assuming that's so, do you put the miniDSP between your sources' digital output and the dedicated sub amp? If so, I assume you use a second digital out from your source to feed the Brooklyn DAC; do you also use a filter after the DAC to dampen the bass below a given cutoff frequency for your main speakers? Finally, do you use a different output from the miniDSP to each of the subs, and tune each one differently? Sorry for so many questions...
@heaudio123

Not usually how a four output miniDSP works. Usually the outputs are for high and low frequency, so with that configuration it is for 2 satellites and 2 subs, with configuration for high pass, low pass, timing, global EQ as well as EQ per driver. It’s’ important to double check with miniDSP as the mixing is controlled by the app, so ask them if you want to do anything fancy with the bigger units.

OP:

If I remember right, you are a proponent of standalone DACs (specifically Brooklyn),

I like mine, my biggest fear with integrated streamers is support for new handheld OSes and new online services. For instance, if you buy a streamer/receiver, in five years, how many of the online services it supports will still work?

DIY swarms,

Yes to DIY speakers, not swarms. Yes, they work, but they are also complicated in that they require 4 subs, and appropriate cabling. My own personal solution is usually 1 to 2 subs, with bass traps AND EQ.


My (limited) understanding of room nodes is that they are affected by the placement of the subwoofer (or subwoofers, as in a swarm). If that is true, can a single mini-DSP fix the room nodes regardless of subwoofer location? Or do you need one mini-DSP for each sub?

I never said a miniDSP would fix everything all by itself. I was quite narrow in my claim. If all you have is 1 sub, adding EQ can get you far. Of course, optimal placement helps, but after this you may still be left with enormous (20 dB) narrow peaks at the listening location. That is what the EQ alone can fix. Clip them, and you can raise the overall sub volume. This alone is an enormous improvement. How much of course depends on how bad the room is to start with.

Room treatment, AND speaker placement AND EQ however can go even further. It can even out the response across the room, not just one location, and you can even treat nulls.

I see this as a continuum:

  • Poor bass due to overall bass level dominated by peaks.
  • Enjoyable bass 
  • Great bass.

One subwoofer, good placement and an EQ can often get the hobbyist with limited space and money far into the "enjoyable bass" region. Appropriate room treatment (GIK Acoustics Soffit Traps for instance), additional subs are what moves the needle into great bass.

So, I don’t think the swarm fanatics are wrong about swarms working. I think they are wrong that it is the only possible answer for the hobbyist.

Best,

E
Fixing bass issues in the analog domain with 11 bands of active subwoofer EQ in stand-alone and floorstander speakers for twenty years.... drumroll Vandersteen Audio.... 

re: nodes

can you fix = yes
can you eliminate = no

every room has nodes

the 11 bands are not octave based they were chosen based on typical nodes in American rooms...

Enjoy the music

I have to say last show I was at, the Vandersteen room was the best sounding. The compensation for the room worked really well.
PS - I do like the Mytek products, but for the most part I’m not fanatical about them.  They have class-leading specs AND sound really good but over the last 10-15 years a lot of great sounding DACs have hit the market.

The only DAC I’m really against are the standalone Oppo lines. I made one or two bad comments about them on Audiogon about them, and the company went under. ;-)

Now I am become Death, the destroyer of worlds.

Fear me, mortals!!!
Also, no matter the route you go ruler flat rarely sounds best - especially in the analog domain.

my favorite analog EQ is the one Roger Modjeski designed for Beveridge .... sweet sounding.. I think Music Reference might still have one or three...
And finally cut is your friend, boost can really ripple... on a well thought out analog EQ cut is 2x boost....
Also, no matter the route you go ruler flat rarely sounds best - especially in the analog domain.

Indeed, you, Fred Toole and I agree on this. Fixing gross abnormalities in the bass region is often all you should do.
Whatever route you go with EQ : DSP or analog - get you best signal to background noise possible - run EQ in the hyper low noise wee hours of the morning.
very few audiophiles understand the baseline s/n of the room they listen in. Use the slow weighting on your SPL meter...

for many this may also lead to the realization that noise management may be a much much bigger sonic improvement than an expensive power conditioning gadget... of course, some of us do both....
Doing this when it's quiet is important, or you'll try to EQ your air conditioner.  :-)

Using OmniMic or Room EQ Wizard can be a lot easier and faster than attempting to us an SPL meter though.
DSP equalization of amplitude and phase for bass can do things no practical analog EQ can do when you have 2 or more subs. Optimum placement of multiple subs will reduce room nodes, but it is always a trade-off. Make one frequency better, another gets worse. Effectively, with DSP, you can have a different "virtual" distance between the subs based on frequency, allowing optimum smoothing of the response on the widest number of listening positions. There are practical limits to what can be done, so room acoustics still needs to be addressed.
Love the lava lamp in the .../systems/8367. ;)   Must be a system tweak not considered before...🤔

DSP makes the miserable space I've been relegated to employ as a 'listening area' (I'd be hard pressed to call it a 'room') tolerable....so my  bias is obvious, and enough said.


DSP makes the miserable space I've been relegated to employ as a 'listening area' (I'd be hard pressed to call it a 'room') tolerable....so my bias is obvious, and enough said.


Exactly.  Sure, we all want to be purists, but the reality is that EQ works.

A light hand, focusing on the most terrible problems in the bass, along with fully thought out speaker integration is a good thing.
perkri, you started another uplifting debate with your simple question :-)

Your friend can also e.g try the blusound node2 streamer/dac which has a sub out before the pre amp. Or the Martin Logan/Paradigm P AMP which I recommend because then you also get the ARC room correction system. The P AMP is fine for driving smaller speakers at normal SPLs. Actually I use it for both Tannoy DC10A and ATC 19 for near-field listening (not exactly small).

To the P AMP you may then connect 28 subs for a really decent bass...




Mostly valuable opinions here.  I, too, am investigating an actual active X-over to take everything below out of the signal to my amp and LRS's and send it to at least @ powered subs.  Those subs can be positioned to reduce nodes.  The miniDSP HD has a x-over, HPF & LPF and by plugging in a PC, Mac or phone app, I believe, 25 bands of parametric EQ.  My concern is if the sample rate of this device will nullify the resolution value of my DAC.  The miniDSP HD apparently is 32bit & 192k.  The new $60 dsp from Parts Express doesn't say. 
Good morning all!

Thank you for all the input, thoughts, ideas and popcorn worthy (at times) lively discussion!

Some more info...

My friends place is not set up as a critical listening system/room.

(One speaker is in a bookshelf, the other on a stand further away, the sub is placed in a seemingly good spot, vaulted ceilings, listening area is off to one corner where "desk is and, to make things interesting, there is a large pre war Steinway grand piano in the room...)

This is very much a lifestyle system. That doesn’t mean, however, that the goal isn’t the same as all systems which is do what you can with what you got and try to optimize as best as possible. My goal is to work with what is there, with some hopefully minor changes, in order to have the sound that is flooding the room sound good!

So, because of the shape of the main area and the rather unorthodox set up, bass nodes are not really a big problem. (Walked around the space many times, and there are no "blank" spots or "areas of pain in the bass")

Another bit of info, forgive the pun, there are currently four sources. Turntable, CD to a Dac, Tuner and a Bluetooth device for You Tube/Guest phone stuff...

Many products to research, thank you!
My concern is if the sample rate of this device will nullify the resolution value of my DAC. The miniDSP HD apparently is 32bit & 192k. The new $60 dsp from Parts Express doesn’t say.


Yeah, this is an issue. This is why I run purely digital EQ (roon right now) or only in the subwoofer.

These DSP based EQ systems have to deconstruct the incoming analog signal, do math on it, and then have a DAC to turn those numbers back into voltages. Not really some one who spent a lot of money on a DAC wants to do.

Using a digital only EQ solution, which does the math BEFORE your fancy DAC gets around this, but doesn’t have a solution for your subwoofer. I use

For the OP, who has 2 speakers in two different locations, plus a sub, though, he’s really going to need EQ to match the L and R plus integrate the sub. Having a fancy DAC is the least of his worries.

Of course, other solutions include a digital preamp with built in EQ. :) Anthem makes them as well as integrateds, and built in sub out, with automatic configuration.
Which war ?

fun room, sounds like a music lover

Bluesound DAC or NAD more than adequate 

have fun !!!!
No idea whether either of these will solve the problem but Parasound Halo preamps have sub out with adjustments
and

Emerald Physics has the BOM
No idea whether either of these will solve the problem but Parasound Halo preamps have sub out with adjustments


Purely analog crossover, you can add an EQ to the sub after.
perkri

He’s got Spendor BC1’s for a reason, for their organic sound when used just simply with source and amp.

Don’t go sterilizing the sound by putting mini dsp and or digital xovers in the signal path, as they have lousy d/a converters in them and if your friend has a good dac that sound will be lost along with the Spendors sound.

Get a pair of these passive HP filters (pick your frequency) on the input of the Spendors amps and use an active subs xovers/plate amp to blend it in to whatever you pick to roll off the Spendors at. Or if the sub doesn’t have an active xover then the use the LP filters on the sub/s amps as well from the same place.

http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=272942669723&t=1540585209000&category=14970&seller=speakeraddict&excSoj=1&excTrk=1&lsite=0&ittenable=false&domain=ebay.com.au&descgauge=1&cspheader=1&oneClk=2&secureDesc=0


100hz HP ones
https://www.ebay.com.au/itm/2-Harrison-Labs-FMOD-100Hz-HP-High-Pass-Satellite-Electronic-Crossover-USA-Made-/272942669723

Cheers George
Our ability to discern detail in bass frequencies, is much less than at higher frequencies. You do not need as good a DAC for a subwoofer as for the rest of the frequency range.

I agree wholeheartedly w.r.t. not using a low end DAC for the mains, but for the sub, I will take the flexibility of a DSP\digital crossover.


I have to question how accurate the passive crossovers will be with indeterminate input and output impedance. Have you measured them with variety of equipment?
Don't know it'll be on their site somewhere, just ask.
http://www.hlabs.com/products/crossovers/

Cheers George
And as far as  "His preamp does not have a subwoofer out." just use one or two of these better to have two subs. 

https://www.ebay.com/itm/AudioQuest-RCA-Male-to-Two-RCA-Female-Adapter/133357704249?hash=item1f0cbd1439:g:3CoAAOSwAbxeaHtT

Cheers George
Thanks again all! I suspect, that the RCA Y-Splitter will cause an impedance imbalance, yes? 

And I would need a DIN plug to 2 RCA's - Pre is a Quad 33 :)

I just feel this will cause some more issues.


About $100 to find out - you can order a decent quality custom quad DIN to rca cable from amazon.

does he have a Quad power amp also ???
You do need to use caution inserting active devices with gain into a Quad system. Rated power can happen at .5 v input.
Hi

No, amp is not a Quad. Spector Acoustics P202
So for an analog solution get din to RCA w splitter and put the analog hipass before the main speaker amp. No EQ but you stay 100% analog.

relatively inexpensive and not complex after initial setup.

must know input impedence of main power amp to calculate/set xover frequency.

best

jim
Which Quad preamp ? Can rummage thru my box of toys, I know I have the AQ splitters in Seattle, would loan ya but I am not dying to do so... ha
perkri OP
I suspect, that the RCA Y-Splitter will cause an impedance imbalance
At 300ohms output impedance the Quad 33 should be good to go

perkri OP
And I would need a DIN plug to 2 RCA’s - Pre is a Quad 33 :)
Plenty of these around on ebay.
https://www.ebay.com/itm/AUDIOPHILE-4-PIN-DIN-PLUG-TO-2x-RCA-PHONO-PLUGS-CABLE-QUAD-33-44-303-405-1M/120570590087?epid=2229645602&hash=item1c12913387:g:gE4AAOxyyF5RQNWY

Cheers George