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Double Bass EA VL 208 VS LDS 208

Ric Vice

Ric Vice

Supporting Member
Jul 2, 2005
14,290
12,447
Olivette, Missouri
#1
Here's an interesting thought that I had as I was reading some ones post about the LDS 108 Three way. Feel free to chime in on this one, I'm definitely not an expert.
I think the reason that the old VL series of EA's work so well for upright
is that that the porting is different from most other cabinets. the VL 108's and 110's didn't have any ports at all, at least I can't find one and I own both cabs myself. So the aren't as prone to feedback. It this true?
The EA VL 208's and 210's were ported to the "side" if the cabinet is sitting the way the EA had it set up. Most TL boxes put the port on the bottom closer to the floor. LDS cabs, from what I can tell by looking at the pictures are all front ported.
Does this create a possible feedback problem and resonance problem
with the upright since the port is firing toward the instrument?

Ric
 
#2
Ric Vice said:
the VL 108's and 110's didn't have any ports at all, at least I can't find one and I own both cabs myself. So the aren't as prone to feedback. It this true?
Click to expand...

I own two VL108's, and they are transmission line designed and ported on the front. I don't own a VL110, but I think that there are three round cutouts on the front - a Woofer, a mid/tweeter, and a port, IIRC. (entirely possible that I have this wrong).

Does this create a possible feedback problem and resonance problem
with the upright since the port is firing toward the instrument?
Click to expand...

I'm not sure if the resonance is caused by the speakers or the ports, but it's never a good idea to point your speakers right at your DB, since it will act as a big vibration-catching body and muddy the hell of the sound. I always try to get mine off the floor and over the body of the bass when I can (I use a stand these days). When this isn't possible, I've found it's best to let the sound from the speaker(s) go around the side of the bass. If neither of these things is possible, I get the best results by setting the speaker on a chair at a 45 degree angle upward. HTH!
 
#3
Most cabinets are ported. A sealed enclosure is very inefficient (would need a really powerful amp).

From my limited knowledge of acoustics, I don't think you can generalize a certain cabinet's feedback likelyhood without taking in to consideration other factors, especially the room it is played in, but also including the bass, the pickup, the amp, etc..

However (and perhaps someone with more knowledge can prove or disprove my observations), I have noticed that a well-tuned front ported cabinet sounds (sound quality: clear lows, tight, etc., not talking about feedback) way better than something where the port is on the side or back. It seems to me that a side or rear-ported cabinet can introduce phase problems. When the sound leaves the rear port, hits a wall and comes forward, it allows the phase (of that wave relative to the wave leaving the speaker) to be changed by the distance of the cabinet to the wall, no?

I had a SWR Baby Blue cab that was rear-ported. Sometimes it sounded killer, sometimes it was muddy as heck. My front-ported Bergantinos are way more consistent.
 
#4
Ric Vice said:
Here's an interesting thought that I had as I was reading some ones post about the LDS 108 Three way. Feel free to chime in on this one, I'm definitely not an expert.
I think the reason that the old VL series of EA's work so well for upright
is that that the porting is different from most other cabinets. the VL 108's and 110's didn't have any ports at all, at least I can't find one and I own both cabs myself. So the aren't as prone to feedback. It this true?
The EA VL 208's and 210's were ported to the "side" if the cabinet is sitting the way the EA had it set up. Most TL boxes put the port on the bottom closer to the floor. LDS cabs, from what I can tell by looking at the pictures are all front ported.
Does this create a possible feedback problem and resonance problem
with the upright since the port is firing toward the instrument?

Ric
Click to expand...

I'm not an expert either. It is my understanding however that transmission lines and ported (aka bass reflex) speaker enclosure designs work very differently. With a true transmission line design, the vent opening is not really a port in the same sense as it is in a bass reflex speaker cabinet design. A transmission line (aka acoustic labyrinth) actually absorbs all or at least most of the energy radiated from the rear of the speaker cone, whereas a bass reflex enclosure uses one or more ports to put that energy in phase at lower frequencies with the sound energy radiated from the front of the speaker cone. A true transmission line typically has a very flat impedance curve at lower frequencies, whereas a bass reflex design usually has 2 significant peaks in its impedance curve. It is also my understanding that some transmission line designs are actually sort of a hybrid and there is some radiation from the vent as there is in a bass reflex design.

Although there doesn't seem to be any universal agreement on this, at least some designers believe that location is not particullarly critical for the vent that terminates a transmission line or for the port(s) in a bass reflex cabinet design, while others seem to think that location is important. I've had speakers cabinets with ports on the front, back and sides, and I think there are other factors that effect the sound more.

As long as a speaker enclosure is properly designed and built, there is no one best solution IMO. Both transmission lines and bass reflex designs are valid (as are other designs).
 
#5
Robgrow sums it all up pefectly. As a port is handling the lowest half-octave of the frequency spectrum, it's location should have essentially no effect on the sound. More important is to engineer the port so you don't get whistling, port resonances and problems of that sort.

The design of the cabinet- sealed box, ported reflex, horn- is secondary to how well engineered the box is. There are very good and very bad examples of all designs.
 
#9
Hey,
Thanks to all for the info. I had to look really closely at the VL 108 to actually find the port. It's a "upside down" TL with the port on top.
This is definitely one of those "I could have had a V8" moments.
There's one other thing about these cabinets that always
puzzled me. Most 3 way cabinets put the tweeter above the midrange
drivers.The VL series reversed that. Did EA do that because the port is at the top of the cabinet or is their some other reason?
The EA VL series all had a very flat response and sound great with
upright. Dose this driver placement effect the sound?
I have never had much luck playing upright through cabinets that use the more traditional round ports in the front or back. I use a Realist and
a one of two different Models of the Walter Woods amps.
The Realist just died? Drag

Ric Vice :confused:
 

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