REL Strata III review. (1 Viewer)

[Scott_N]

Saturday I picked up the Strata III I had ordered and got it setup using the track 4 from the soundtrack of Sneakers which has a repetitive bass drum. I ended up placing it in a corner to the left of my system and with a crossover setting of 27hz and the gain at the 12 o'clock position. Now to the sound. I hate subwoofers in music. I mean I really despise them and I thought I would never use one in my 2-channel system. All the subwoofers i've heard have the same boomy and muddy hyped up mid-bass with overhang that really bothers me. But this sub is nothing like the other subs i've heard. I like two-way speakers because of the way they image and my Tetra Space's are a two-way speaker. They have a open and spacious sound but they don't do low bass very well. My amp is a Conrad Johnson CAV-50 which has a great midrange and mid-bass but also doesn't have much slam.
Well this sub was just what I needed. Unless you knew I had a sub you would not be able to tell because of the way it blends with my mains. With the sub everything I played from rock to classical and jazz sounded fuller and with more weight. Taking out the sub made everything sound leaner and thinner. The sub made the stage a little deeper and wider and the midrange smoother. If you like musical bass then this sub is for you. Now I have the imaging of a two-way and the full balanced sound of a good full range speaker.

 

[BruceD]

I hate subwoofers in music. I mean I really despise them and I thought I would never use one in my 2-channel system. All the subwoofers i've heard have the same boomy and muddy hyped up mid-bass with overhang that really bothers me.

This is mostly due to poorly implemented crossover methodology and room modal peaks, not due to the sub itself.

The process of blending a sub with main speakers is not a simple task, as your listening experience shows. Also, room acoustics (expecially bass room modal peaks) play a critical role in how this blending sounds in the final analysis.

When blending mains with a sub, you must either take into account the acoustic rolloff characteristics of the main speakers plus the crossover, or eliminate the effect of the main's acoustic rolloff by crossing over about 1 full octave above the mains low frequency f3 (-3dB low frequency spec).

Typically the best way to do this is with a 24dB/octave slope (faily steep) Linkwitz-Riley (has a zero degree phase offset) active XO filter for both high-pass and low-pass. None of the HT receivers offer this and only a couple high-end prepros do.

I have been using an active electronic crossover (Marchand XM9-L) between my mains and sub for 5 years very sucessfully with this method and use it all the time with 2-channel music. It also works great in HT 5.1 mode.

 

[Edward J M]

Typically the best way to do this is with a 24dB/octave slope (fairly steep) Linkwitz-Riley (has a zero degree phase offset)

How does the Linkwitz-Riley 4th order filter manage to maintain a phase correct response? The issue of phase delay as it relates to both the crossover network and the subwoofer alignment itself is something I've been studying, and any light you could shed would be appreciated - the topic is challenging.

 

[dave alan]

Edward,

This is one of the best articles I've read for a basic foundation.

I've pasted an excerpt below because few seem to see the significance of time alignment in subwoofer integration.

Most processors don't include time alignment for the sub and most subs are placed nowhere near equidistance to the LP with the mains they are supposed to 'blend seamlessly' with.

Also, [some] multiple driver subs are designed such that they are impossible to time align with the sats.

Excerpt from link:

A Linkwitz-Riley crossover applied to drivers that are not time-corrected loses most of its magic. The lobing error is no longer zero; it exhibits a frequency dependent tilt with magnitude errors as shown in Figure 7b.

 

[Edward J M]

Thanks, Dave - I'll print that hotlinked report out and study it in detail.

Do you know if the typical digital bass management circuit compensates for phase shift? Unless user variable, the typical BM circuit employs 2nd order high pass and 4th order low pass filter slopes. Wouldn't a 2nd order high pass filter normally introduce a phase shift into the subwoofer signal?

Thanks,

Ed

 

[dave alan]

Edward,

Try This

You can search FIR and IIR (finite impulse response and infinite impulse response) filters for tons of info on digital BM.

The short answer is 'yes', IMO. A high pass filter cannot possibly be universal to every loudspeaker model out there.

Some day the filters will be in the speakers as part of an all digital setup, and, therefore be optimal in every way.

I don't look for that to be something we'll see very soon though, so I've been working on an active, analog version of this as a 7.1+1 system for about a year.

With all the room mode/EQ buzz, people seem to have completely overlooked the simpler causes of peaks/dips in response such as what effect a HP filter of a given design has on a particular speaker.

The Qx of a HP filter may cause a rather huge hump at crossover and have differing end result slopes, causing a 'hole' and/or shifting the crossover up from the LF point.

Time alignment, filter 'Q' and slopes and phase alignment are the place to start in trying to properly optimize subwoofer/satellite integration.

IOW, you're barking up the right tree.

 

[BruceD]

Part of the key to understanding what is going on in your particular room/speaker setup is using an acoustic measurement system to actually measure current parameters (frequency response, impulse response, energy time curves, 3D waterfall charts) and then chart changes to optimize these variables; speaker and listener positions, crossover changes, EQ changes, acoustic treatments, etc.

A very good (and inexpensive) solution with lots of instructional and demo material is the ETF5 software program. I use it with a battery powered notebook and battery powered mic/preamp.

An excellant reference book is the "Master Handbook of Acoustics" by F. Alton Everest, 4th edition (available in paperback).

 

[Mike Sloan]

....and the Rel Strata III...slowly fades into oblivion...

 

[Edward J M]

Actually, it was a bit of a thread hi-jack, but not totally off-tangent. Doesn't the REL high level connection have some unique properties/features along the lines of what we are discussing?

While it may not lend itself to HT application (being too shallow of a slope) wouldn't a first order filter (aside from the L-R discussed above) be a phase transparent means of high passing the mains to the sub? I'm wondering what the high level filter network on the REL looks like......

 

[Troy R]

I may be wrong but REL's don't bother with high pass XO's. They go on the principle of bringing the bass up underneath the mains. You run your mains full range and bring the sub up underneath to fill in the bottom octave. That is why they offer such low XO points, and also why they seem to ALWAYS seemlessly integrate with any speaker.

Am I thinking correctly here?

 

[Scott_N]

Yes you run the mains full range and when setting up the sub you slowly turn the crossover up until the bass just starts to muddy up a little then turn the setting down one click. It suprised me that the crossover settting I ended up with was so low but there doesn't seem to be any holes in the bass response. Last night I played some music with a pipe organ in it and the REL played the very lowest notes cleanly and without sounding compressed.

 

[Phil A]

Rels use of high level connection is explained in more detail on their website indicated below. With separate volume controls for the high and low level connection, it has the ability to be optimized for each. Some processors may allow different level setting for music and movies but what makes the Rel flexible vs. other products is the crossover. Even with an outboard crossover with another sub, one won't necessarily have the ability to adjust volume for both movies and music at the same time.

http://www.rel.net/resource/bassdelivery.shtml

http://www.rel.net/resource/faq.shtml

"The REL Active Bass Controller.

Essentially, by using the simple to adjust filter controls on the ABC, the sub-bass system is brought up beneath your main speakers to the point where their acoustic output is falling away. This will vary from speaker to speaker and room to room. Even the same speakers when used in different rooms will have differences in their bass extension. The only condition that must be observed for the system to function correctly, is that your existing speakers do not themselves cause "room boom", i.e. they are not too big for your listening room. Neither must they be too "thin" sounding, or you may end up with a "hole" in the response.

The ABC has a gain control which adjusts to compensate for the lack of boost given to these very low frequencies by your room. This ensures a smooth blending of sound from the two sources. With this system you will be able to hear (and feel) very deep bass."