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Subwoofers.... one 10" or two 8"?

I'm looking to fill out the bottom of my simple 2 channel system  (Musical Fidelity X-Ray CDP through Peachtree Audio Grand Integrated amp to a pair of Mirage OMD-15 full range speakers).  I occasionally will play the TV audio through the system for movies, but not interested in an HT setup. Music is the prime focus. The room is "medium" size.  I know that will not give the deep bass feel of a 12", but the difference should not be too great, and a 12" may be overkill for that room.  I've also considered getting two 8" subs to keep the sound balanced between the left and right channels. I think the  8" may be enough bottom for my room and tastes. I'm on a budget so getting a pair of anything bigger than 8" may not be in the cards.

Any opinions or suggestions as to whether I'd be better off with one 10" or two 8" subs?

















larstusor
danvignau's avatar
danvignau
935 posts
 

I have tried both, with varying, but excellent results with each.

For 25 years, I had some six foot tall electrostatics which originally had very sloppy cone subs. I also had a pair of NHT subs I hated.

I found some Peerless 8' and 10" sandwich cone subs, 8" for the

stats, an 10' for my B&Ws.

I really preferred the 8's, but they did not have the output I need for the  B&W's, so they went away with the electrostatics.

I have since upgraded these subs and use matching amps and preamps

for the mains and subs. After years of tweaking, the subs now reside between the B&W towers, time aligned with rulers. of course. This definitely sounds better on music than any subs my audiophile friends have brought by, 'though not as loud due to my (only) 125/250/400 (@8/4/2 ohms) stereo amp that drives them. 

leotis
183 posts
 
Due to "group delay" sound impulse leaves the sub usually 8-10 msec later than it leaves the main, even though the electrical impulse hits the sub and the main at the same time. So must be aligned by ear. Using just distance measurement doesn't work. Used to think there was something wrong with my autocalibration when it consistently made sub setting farther away than the actual measurement. Check:
http://www.theabsolutesound.com/articles/subwoofer-basics/?page=3
larstusor OP
59 posts
 
Someone please explain "time aligned"
erik_squires
16,901 posts
 
@leotis

That's a huge amount of "group delay." I think you are confusing that sub's are often located several feet behind the mains.

As for aligning by ear, great googly moogly no! :) It's far easier, faster and more accurate to fully align with a tool like OmniMic or AudioTools or Room EQ Wizard than by ear! :)

Assuming the room modes are dealt with, the second stage in integrating a sub are to integrate it with the main speaker. This runs into the same issues a speaker designer would have in blending one driver with the next. Meaning, crossover slopes and phase alignment to provide a seamless transition from the subwoofer to the main's output. You should not be able to tell by looking at the frequency response where the sub ends and mains start, it should appear like 1 single speaker.

Best,


Erik
erik_squires
16,901 posts
 
@larstusor

It means a lot of things, but in general it means making sure that each driver you are listening to blends seamlessly with others despite being located at different distances from the listener.  It matters in multi-way speakers as well as in integrating a subwoofer with a main speaker. This really is "phase alignment" but in use it's often called "time aligned." 

In flat baffle designs, each driver has a different acoustic distance from the listener. Phase alignment means you've taken that and the phase of the crossovers into account so that the frequency response has no dips/valleys where they meet.  Here is an example from a speaker I designed, the LM-1.  Look at the second and last chart for more information. 

At it's most stringent, time alignment may mean having a perfect impulse or step response.  Van DerSteen is famous for this type of design.  Look at the step response in Stereophile's review of the Seven and compare it to the LM-1.  Thiel is also a manufacturer that specialized in time-alignment.

Best,


Erik

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