Las or Belle corner reflectors....

[sfogg]

Reading the K'Horn bass horn thread I was wondering if anyone ever tried any back corner reflectors in a LaScala or Belle bass horn?

Since I run my Las bass horn up to 600hz I was considering trying the reflectors to see if it makes any difference.

Has anyone done this? If so how wide did you make the reflectors?

Thanks,

Shawn

[yaffstone]

The bass on Belle and LS is already forward facing so there's no need for a reflector like with the k-horn where the last fold is the wall. There is a thread on adding a port to the LS though. Increased performance has been noted with the addition of the port.

[greg928gts]

I was talking on the phone with Gary Gilliam one time, and he described experiments that they did at K&A where they faced La Scala bass bins into corners. Apparently you can get some enhancement of bass frequencies this way. Sort of like adding another fold to the bass bin.

The La Scalas I'm refurbishing have the top horn section split off the bass bin for "looks" plus the added benefit of experimenting with the bass bins in corners.

Custom La Scalas

Greg

[sfogg]

"The bass on Belle and LS is already forward facing so there's no need for a reflector like with the k-horn where the last fold is the wall. "

The sound from the triangle reflector in front of the motorboard slot basically aims the sound right into the sides of the LaScala such that some is probably reflected back toward the throat. There was discussion as it relates to the Jubilee that reflectors in those corners will help prevent that. This might help the top end response of the bass horn, not the bottom end.

"There is a thread on adding a port to the LS though.  Increased performance has been noted with the addition of the port"

No need, I have subwoofers that fill in for the LaScala's lack of bass far better then porting the Las would do.

Shawn

[Marvel]

Shawn,

I believe Tony Reed has reflectors in the corners of his. I know some people on here have done it. Perhaps he will chime in. (although I have given him credit before and he has said it wasn't him ) Maybe I should take more notes, before I forget everything.

Marvel

found the pic. He doesn't have the dimensions, but the red is the reflectors and the blue is a shelf brace to cut down on side wall resonances. I think if you make the reflectors too big, you will constrict the channel width.

[Tony Reed]

Yes, I did put "reflectors" in the back corners of a pair of home built LaScalas. I made them the same size as the "splitter wedge" at the throat. I don't have any way of measuring the difference, but the low end seems smoother.

Tony

[Marvel]

Yes! I finally remembered something right.

[Tony Reed]

Marvel:

I can't believe you still have that old crude drawing that I did!

Tony

[3dzapper]

"I think if you make the reflectors too big, you will constrict the channel width."

I was reading a piece by Bruce Edgar about this subject. In it he explains the proper way to make bends in horns to properly transmit the bass waves likening the transition to an inductor. He said that for proper propagation, a slight constriction is desirable. Before I read that, you could have beat me with a 2X4 and I'd never have thought....

Seeing it graphically, it made sense.

You can see it HERE.

Rick

[Marvel]

Tony,

I keep far too much stuff. I found that it is a fine balance between keeping it and deleting it.

One of my co-workers had it worked out great. He threw out things we needed and I kept things we didn't.

Rick,

Thanks for the pdf. It makes sense that you don't want the wave bouncing straight back. That is what D-Man was talking about with the splitter too.

Marvel

[sfogg]

Thanks guys, I'll have to give that a try and see if it makes an audible or measurable difference. I was considering the shelf braces too but I high pass my LaScala's so they don't really shake like they did when run full range.

Thanks,

Shawn

[D-MAN]

It always seemed to me to be a purposeful omission on PWK's part that the LS/BELLE don't have the same attention to detail that the Khorn/Jubilee have.

I assume it to be that since the relatively high 70Hz Fc of the horns in question made it somewhat non-critical, it is well known that a 90 degree perpendicular wall will cause reflections back to the throat. Physics.

The use of corner wedges will alleviate this. Simple and effective, what could PWK be thinking except that:

1) saves time in manufacturing

2) reduces weight (shipping)

3) at 70 Hz who cares?

But it really is a matter of physics that it will CERTAINLY sound better with the reflectors than without them. Frankly, there is no real excuse for them not being there in the first place. However, they SOLD without reflectors anyway, so who is more right?

DM

[WMcD]

When I've made bass horns similar to the LS and Belle, I did use the so called corner reflectors. You see them in EV plans for the Eliminator II. OTOH, I recall they are not used in the MCM patent drawings.

I'm not sure they're needed and can't fault PWK for not using them. D-Man implies that perhaps the extra pieces were not used because the speakers are some sort of step children to the bigger brothers. That doesn't seem in keeping with PWK's way of doing business.

Generally, the more complex folded horns seem to have issues of losses at high frequencies, as shown in Dr. Edgar's publications. Generally, a better turn at the corner is thought to help that.

However, I think that the simple bass horn like the LS and MCM with only one turn don't have the same loss of HF issues overall. Plus I believe the forward facing mouth gives a lot of advantage at HF.

If you look at the Jubilee paper, much of the HF issue is solved by forward facing, and close spaced mouths. The LS already has that. Granted the Jubilee has corner reflectors at the first bend and a similar structure at the back turn. (I think the "reflection" description is a bit inaccurate anyway. It is not quite like light and a mirror.)

My conclusion is that PWK may have found the LS and Belle didn't have issues of significant rolloff at HF, as compared to bass rolloff in veiw of a higher Fc. If there is some HF loss, maybe that knocks things down to a level more in line with the bass.

Gil

Gil

[DrWho]

Also, who's to say that not adding the reflector didn't actually improve the end result? Maybe he left it out because it compensated for some other natural flaw in the speaker. So perhaps adding it will bring out that flaw. The problem here is that anyone that does the mod and hears a difference is going to claim that it's an improvement because they will justify it with some limited thinking of the entire system. I believe the best way to approach such matters is listen to the original design and determine what flaws you are hearing and what causes them. Then determine which of them are fixable and the options available that address the problems; taking into account the compromises involved.

Defining the problem is the hardest part because it implies the solution. If you don't hear any problems, then there are no solutions.

[scriven]

All solutions have problems.

[D-MAN]

Guys, check out Huygen's (sp?) work on waveform propogation and reflection, it is touched on in the Edgar "Monolith" paper, and see if you keep the opinion that it won't change the sound. I would expect that some REAL mid-and-upper bass output (even more) would be the result of putting in corner reflectors, after all, it WILL reduce turbulance and that HAS to effect efficiency in that virtually ALL of the output will be coming out the horn mouth instead of being partially reflected back into the throat. If it is done correctly it will also preserve the waveform intact. That is almost like having NO fold at all.

The Khorn and Jubilee have corner reflectors, and YES, I DO consider the LS and BELLE to be the cheaper "step-children".

As far as me implying that PWK cut some corners for economic purposes, I submit the consistant use of the EV T-35 tweeter as possible evidence. Or using the K33E in the Cornwall. This implication is not without foundation.

But the important thing to consider is that the LS was originally intended to be used in PA work, and NOT hi-fi. So I tend to side with PWK, for PA work, it doesn't really matter. But for hi-fi, I think it does.

DM

[D-MAN]

Here's an extract from the Edgar article.

DM

[JohnA]

Here is the published response curve of the FH1 that has corner reflectors. Anything above 500 or 600 Hz is bettered by the reflectors. I'll try to measure their size tonight.

[mark1101]

I assume you guys are crossing over somewhere higher than the standard 400Hz. I see 600 Hz. mentioned.

Disregarding the corner pieces, does that change alone make a big difference in performance. Does it sound a lot better that way?

Sorry, don't mean to get OT.

[sfogg]

John,

I was thinking the reflectors would help on the top end more then on the bottom too which is why I am going to give them a try. I'll take traditional FR measurements but I'll also do some time domain waterfall plots as well. If the reflectors do prevent reflections back into the mouth that change might be noticeable on a waterfall plot when looking at decay.

Mark,

" Disregarding the corner pieces, does that change alone make a big difference in performance. Does it sound a lot better that way?"

I didn't change just the crossover point alone I also converted them to a two way using Al's Extreme Slope crossovers with Altec 511B horns and Altec 902-8B upper drivers.

Shawn