[BMU (Bryston Maggie User)]

Hi

I'm experimenting with adding a sub to my 2-channel system.  Let me explain... I have a

Squeezebox 3 digitally feeding a...
SP 1.7
9B-ST with 4 of 5 channels passively biamping...
Magnepan 1.6QR's (rated to 40Hz -3dB)

now added a Velodyne Digital Drive 12 subwoofer  (12 inch sealed driver with "room correction" capability)

After lots of reading and experimenting I'm using the SP 1.7's digital xover at 80Hz, running the 1.6's as "small", and sending the "LFE" to the Velodyne via the SP 1.7's sub output.

By rolling off the 1.6's they sound more open and dynamic.  (Typical explanation from what I've read is that they are no longer burdened with trying to reproduce the lowest frequencies.  So I guess this is a good thing.) 

I do find the transient nature of the bass in 1.6's to be very articulate and pleasing in my room.  However the Velodyne does provide that missing lower octave. I've noticed that with the SP 1.7 xover actice at 80Hz the 1.6's still have very usable in-room output down to around 50Hz as measured with the mic that comes with the Velodyne.

To avoid over loading the room I've used the parametric eq and used a lower gain in the Velodyne to adjust the sub's output to try to achieve a flat frequency response.  80Hz is a relatively high crossover - occassionally I can localize output from the sub (near corner placement).  With lower crossover frequencies there is less localization but perhaps the 1.6's sound less open running near full range.

QUESTION:  Would there be any dis/advantage (theoretical or otherwise) to rolling off my 1.6's using the SP1.7 at say 80Hz and sending a separate full range signal to the Velodyne using the SP 1.7's tape output and then using the fully adjustable low-pass crossover in the sub? (ie. not using the low passed LFE sub output on the SP 1.7)

I was thinking that this I might be able to use a low-pass of less than 80Hz and adjust to xover slope to better integrate the sub with the digitally rolled off 1.6QR mains.  I guess this is like using a different crossover point for the mains and the sub.


Thanks
Alex

[James Tanner]

Hi

I'm experimenting with adding a sub to my 2-channel system.  Let me explain... I have a

Squeezebox 3 digitally feeding a...
SP 1.7
9B-ST with 4 of 5 channels passively biamping...
Magnepan 1.6QR's (rated to 40Hz -3dB)

now added a Velodyne Digital Drive 12 subwoofer  (12 inch sealed driver with "room correction" capability)

After lots of reading and experimenting I'm using the SP 1.7's digital xover at 80Hz, running the 1.6's as "small", and sending the "LFE" to the Velodyne via the SP 1.7's sub output.

By rolling off the 1.6's they sound more open and dynamic.  (Typical explanation from what I've read is that they are no longer burdened with trying to reproduce the lowest frequencies.  So I guess this is a good thing.) 

I do find the transient nature of the bass in 1.6's to be very articulate and pleasing in my room.  However the Velodyne does provide that missing lower octave. I've noticed that with the SP 1.7 xover actice at 80Hz the 1.6's still have very usable in-room output down to around 50Hz as measured with the mic that comes with the Velodyne.

To avoid over loading the room I've used the parametric eq and used a lower gain in the Velodyne to adjust the sub's output to try to achieve a flat frequency response.  80Hz is a relatively high crossover - occassionally I can localize output from the sub (near corner placement).  With lower crossover frequencies there is less localization but perhaps the 1.6's sound less open running near full range.

QUESTION:  Would there be any dis/advantage (theoretical or otherwise) to rolling off my 1.6's using the SP1.7 at say 80Hz and sending a separate full range signal to the Velodyne using the SP 1.7's tape output and then using the fully adjustable low-pass crossover in the sub? (ie. not using the low passed LFE sub output on the SP 1.7)

I was thinking that this I might be able to use a low-pass of less than 80Hz and adjust to xover slope to better integrate the sub with the digitally rolled off 1.6QR mains.  I guess this is like using a different crossover point for the mains and the sub.


Thanks
Alex

Hi BMU,

No the Tape Out is a constant signal and will not track the volume control on the SP1.7

Use the SP1.7 stereo left/right signal (the one your not using RCA or XLR) that way you will track the volume control and let you experiment with the Crossover and Gain controls on the Sub.

james

[Phil A]

Bass frequencies also sum in a room so I would recommend doing something in conjunctions with measurements from an RTA or an SPL meter and a test disc.  They also do sell inline attenuators for placement between your preamp out and amp that are not tons of money to reduce the bass output going to the main speakers.  I use Rel subs which besides the normal HT input have a separate crossover and volume control to take a signal from the amp and fill in the bass below where your mains drop off.

[BMU (Bryston Maggie User)]

No the Tape Out is a constant signal and will not track the volume control on the SP1.7

Use the SP1.7 stereo left/right signal (the one your not using RCA or XLR) that way you will track the volume control and let you experiment with the Crossover and Gain controls on the Sub.

james

Oops!  Yes using the Tape Out would not be a good idea for the sub... (embarassed that I had to ask about it)

So you're suggesting that I run the 1.6's full range and send the same signal to the sub then use the sub's low pass crossover etc.

When used with such a "line-level" connection, my Velodyne has a set of output RCA jacks that incorporates "a 80Hz / 6db high pass crossover"  (I don't know if this high pass is an active or passive design).  One option would be to attach the high-passed outputs from the sub to my 9B-ST and "actively" bi-amp the system (instead of running my 1.6's full range directly from the SP1.7 to the 9B-ST). 

QUESTION:  Is this a good idea or is "inserting" this non-adjustable filter /crossover between the SP 1.7 and the 1.6's going to introduce noise etc.

Thanks
Alex

[James Tanner]

Hi Alex,

Unless the electronics in the crossover are exceptional (like our 10B crossover) you generally do not want to insert further circuitry than necessary.

But the problem is:
1. can the Mains handle a full frequency signal.
2. does the Sub and the Mains integrate properly when you allow the mains to go down all the way to their natural cutoff point.

Getting the integration correct is not easy so to some degree it is a trial and error exercise. Where the Mains overlap with the Sub you have all kinds of Phase issues so positioning, rolloff slope and frequency chosen are all critical.

So after all this I guess it comes down to which setup sounds best in a given room. The problem I see is that there are no hard and fast rules for getting this integration correct. In my 16x23 room at home the Thiel 3.7's and the Thiel Subs (SS1 x 2) intgrate perfectly using a Bryston 10B Crossover with the Mains fullrange (no crossover) and the Subs at 50Hz at 18dB per octave. With my MG1.6's in the same room with the same Thiel subs the 10B has to be set both highpass and lowpass at 60Hz -18dB to sound the best.

james

[BMU (Bryston Maggie User)]

Thanks for the info James.  I guess there's no easy answer so I'll need to experiment.

After some more reading I would like to share some of the articles I came across.  One is from Thiel and the other 6Moons (but discusses Bryston gear...)  The sidebar article from 6Moons is particularly interesting as it seems to champion to use of "high level" connections from power amp to the speaker inputs of the sub.  REL seems to use something similar.


I found them both helpful in terms of breaking down various subwoofer connection / integration methods.

http://www.thielaudio.com/THIEL_Site05/Pages/models/Current_Models/SmartSubs/subwo_needxover.html

http://www.6moons.com/audioreviews/genesis4/subwoofer.html

http://www.6moons.com/audioreviews/genesis4/sidebar1.html

Hope somebody else finds this helpful.  It would be interesting to hear what others think of the various subwoofer connection methods.

[hakalugi]

Hi,

i now push maggie mc1's (the wall hanging speakers) letting the SP's crossover do the work, as i've put my martin logan CLS'es in storage while my boys are learning what "no" means (16 months and 3 yrs old).

at first i ran the CLSs full range b/c i too liked to let my main L/R panels go lower than 80hz, and then used a separate (parametric) eq+XOver to limit the bass that went to my subwoofer's amp.

with the MC1s, being smaller than the CLS, (even with the boundry reinforcement) they don't play as loud as low, but if you give them only > 80hz, they get along just fine.  so now, i do run my L/R in 'small' and let the sub do the rest.