EA-208VL Bass Cab' as a Sub

Cybernalt

With my old Bose L1 rig, I used my EA-208VL cabinet as the sub'. The L1 crossover was affected by taking the "bass line-out" (or what ever they called it) back to the board where it was mixed with the signal from the bass-guitar preamp and sent via a separate buss to an amp and this cab. Worked really well - especially for bass 'cause it sucked through the L1.

Now with the PA+ I intend to do the same thing but am tuning the crossover by ear 'cause I'm not really sure where to set it. I have done so using an MP3 file 'cause it's difficult to play and simultaniously tweak the PA+. On the upper-side I have QSC K8's as side fill monitors and RCF 312a's as mains.

Any thoughts where/how the crossover should be set?

=

EDIT: VL-208.

Gadget

What are EA-208VL cabs?

Cybernalt

... hard to describe ...

1) no longer made, 2) A lot like full-range PA speakers (think Accugroove).
3) Configuration: 2x8 + 2x5 + 1 Tweeter in a sealed transmission-line cabinet, 48 lbs., 400 Watts
4) Sound Quality: "Very balanced highs, mids and lows. Sweet is the word that applies to the sound."

A good candidate for PA Subs ... in my 'umble opinion ... great bass speakers, in everyone's 'umble opinion.

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I guess the real question is short of listening - how should I arrive at the best settings?

Gadget

Well, unless you have a frequency response for the L1 without the subs I would only be able to guess at a setup...Do you have the response curve? Or a measurement mic you could take a snap of the L1 without the sub?

I have to tell you that one of the major conversations on the Pro Sound Web was how the Bose L1's lost frequency response rapidly...I'm NOT a fan of Bose as you are probably aware, but I'm not bashing here either (which IS unusual... ) just trying my best to help without judging...

Gadget

Oh, and was EA a company? any pictures? you do realize that covering the same space with disparate speakers causes high frequency (and others.., they just aren't as noticeable...) modes, cancellations and all manor of sonic chaos...

Laredobass

EA = Euphonic Audio, a manufacturer of bass guitar amplification:
http://www.eaamps.com/

The cabinet in question was one of their offerings:
http://www.bazaar-world.com/uploads/amp ... 9641-1.jpg

Cybernalt

Gadget wrote:

Oh, and was EA a company? any pictures? you do realize that covering the same space with disparate speakers causes high frequency (and others.., they just aren't as noticeable...) modes, cancellations and all manor of sonic chaos...

.. you can relax - the Bose L1 is gone

Replacing it are a pair of K8's &/or RCF-312a's ... and a PA+ ... which is why the best-crossover-setting question.

... so in attempt to be clearer:

Stereo Mixer Main Out (Voices and Keyboards with minor drum / guitar reinforcement) > PA+ ...
... PA+ "highs" > K8's &/or RCF312a's
... PA+ "lows" (mono) > Mixer Sub-Group "a"
... Bass Guitar Preamp > Mixer Sub-Group "a"
Mono Mixer Sub-Group "a" > QSC 1804 > EA-VL208

Gadget

Ok, but there is a heck of a lot of difference between a K8 and a 312...The 312's I might suggest 100-118hz LR24 but the K8's definitely 118hz or higher for a live setup rig...Sure the frequency response says it goes down to 66hz (-6dB) but that's not a good idea in live setups... I might even go higher...problem is typically that some subs start to sound honky, but that would be true of your situation, but then interaction in the crossover region would still be a possibility. At any rate it's easy to change setups, and crossover points for comparison sake.

Cybernalt

Gadget wrote:

....it's easy to change setups, and crossover points for comparison sake.

Amen.

I'll just keep experimenting - but it sounds like I need to move a bit higher in my x over experiments.

Thanks.

Gadget

I would... the thing I have found is, the lower you move the xover point the less clear the critical midrange sounds, and the less sound pressure you can get out of them before breakup, and the less power they take to get the SPL...

Cybernalt

... so what's a good "gap" between speakers ... that is: If I use 130 Hz as the upper cut-off, should I use the same as the start of the lower - and play with BF#'s to hear the best transition .. ?? ... and (theoretically) is the same butterworth # leaving the lows the "right" butterworth # entering the highs?

Gadget

Gap? Some manufacturers use gaps but it is my feeling that it really hides some flaw in the design, or implementation. Certainly they have more, and better tools at their disposal than we do to make such a determination...Of course some overlap is inevitable and if your talking about a gap in the crossover point with a lower filter type like say 6dB / octave, then it's possible but you generally end up with more frequencies in the overlap area and thus more interactions... more possibilities of cancellations and modes... etc.

Gaps would create.. (just as the name denotes) a gap in frequency coverage. so normally are to be avoided. Overlaps, which are inevitable without gaps, will produce the interactions noted above, and with higher numbers of interacting frequencies. Generally a steeper slope and a symmetric crossover point are safer, and sonically preferable...There are also overlaps used in some crossovers, they generally use Butterworth high slope filters and usually are accompanied by parametric EQ's on either side of the crossover point to smooth the response.

Generally, for us weekend warrior types without the proper tools (like an FFT measurement system) and a LOT of education in system tuning, find that LR filters are the most symmetric, and easiest to get right. We also generally choose the same or nearly the same crossover point (some gap might work here but generally needs more equalization the the crossover point than say a 100hz/100hz crossover point. Note here that crossover theory is complex and math heavy and we aren't getting into that here...

If by "and play with BF#'s to hear the best transition" you mean Butterworth filters, then ya, that's not a bad idea, try LR 24 while your at it also because that topology has a 360 degree phase shift instead of less, or more and leads to phase problems the DRPA+ is not equipped to deal with. Also try different crossover points, slopes and types. They all sound a little different. Generally for the uninitiated here we suggest LR 24 adjacent same xover point filters.

Note that there is a difference between the electrical and acoustic xover points (the point you choose electrically may not be the one you end up with acoustically.. and, when you change the crossover gain, or the amplifier gain, the crossover point will change as well...

Cybernalt

Thanks ... it is way cool to have the ability to play so easily with these settings.