[Todd Willhoit]

Hi to all. 

I received parts last week to build an X-LS Encore pair and servo sub.  This is my first DIY speaker build and I have a few questions if someone is able to offer advice.

General questions:
1. What is the best glue to use?  I have read about the glue lines telegraphing through the veneer and would like to avoid that problem.
2. What is a good source for veneer?
3. Any other cabinet building tips?

XL-S:
4. What are the pros/cons of ported or non ported?  If I understand correctly, the bass response when non-ported is not quite so low, but it has the advantage of closer placement to the wall.  Should I worry about this considering that I will be using a sub?
5. Regarding baffle step loss, how much roundover can I use?  I think I have read that most people use 1/2" or so.  Is bigger better, or will it compromise the design?

Sub:
6. For the time being, I will be using an old Yamaha RX-V670 5 channel (not 5.1) receiver.  It has pre-outs, so I can at least get low-level signal to the plate amp.  Depending on placement, the RCA cable may be 10' long each direction.  What are the limitations for RCA cable length?  Should I be looking for a new receiver or pre-amp?  (Cheep and cheerful recommendations welcome.)
7. If I had a receiver/pre with sub out, should I use the receiver/pre crossover or the one in the plate amp?
8. I read elsewhere on the AC that some like to keep the plate amp in a separate enclosure, and some attribute amp failures due to vibration when mounted in the same enclosure as the driver.  What is your experience/recommendation?
9. Is it recommended to use side-firing like the plans, or is down firing acceptable?  Pros/cons?
10. If down firing, what have you used for feet?


Todd

[jeffh]

1. What is the best glue to use?  I have read about the glue lines telegraphing through the veneer and would like to avoid that problem.

I think this depends on the type of veneer used.  Paper backed can be applied with contact cement. For glue up of the speaker box, you cant beat Titebond.

2. What is a good source for veneer?

http://www.certainlywood.com/
http://www.oakwoodveneer.com/
http://www.ebay.com/sch/Lumber-Veneer-/67236/i.html
http://www.veneersupplies.com/

3. Any other cabinet building tips?

There are a lot of great build threads right here on the GR Research forum that can show you how it is done.

[mlundy57]

I use Titebond III to glue up cabinets.

I have used both 10mil paperbacked veneer with a PSA coating (peel & stick) and 22.2mil bubble free veneer (BFV - laminated backing).  I used Heat Lock glue and an iron to apply the 22.2 mil veneer.

I have not had any issues with MDF seams showing through either 10mil or 22.2mil veneer.  I have had problems with seams showing through on painted boxes. The 22.2mil BFV from Oakwood Veneer Company is specially designed to prevent things like seams showing.

For sources I have used OakwoodVeneer.com, Veneer Supplies.com, and my local Woodcraft store.

The X-LS Encore was my first DIY speaker build also.  I agree with jeffh, check out the build threads in this circle. There are a number of different build threads for X-LS Encores which I found really helpful.

I have used 1/2" roundovers on a pair of X-le Encores and N1X's and a 3/4" roundover on a pair of N3's. Don't know if a 3/4" roundover would be too much for bookshelf speakers but I sure like it on the floor standers.

Mike

[Todd Willhoit]

I checked my roundover bit.  It is 1 1/4".  I would definitely need to stop the profile near the woofer.

Todd

[mlundy57]

I checked my roundover bit.  It is 1 1/4".  I would definitely need to stop the profile near the woofer.

Todd

Todd,

Is that the size of the radius that's cut or of the outside diameter of the bit?

My 3/8" radius bit has an outside diameter of 1 1/4". A 1 1/4" radius bit would have a 3" outside diameter.

Mike

[Todd Willhoit]

Mike,
That is the radius.  It is big.

If what I have read about baffle step "loss" is correct, it is actually "gain" in the higher frequencies due to reflections off of the front baffle - particularly one with sharp edges.  Is there a point of diminishing returns with the radius, or can a larger radius interfere with the baffle step circuit compensation?

Todd

[mlundy57]

You must have one honkin router motor for a bit that size. I think Ruben has made some cabinets with a 1" radius round over.

You have me curious about the technical aspects of the round over.

Mike

[Todd Willhoit]

Lacking any guidance on the roundover, I moved on with an experiment.  I had some old drivers laying around and decided to build a "mule" of sorts to test the roundover.  The cabinets are the same dimensions as the X-LS with the exception of a 1.5" front baffle.  The pictures below show the baffle with a 1 1/4" roundover.  It cut quite easily with the PC 7518 in my router table. 

The unknowns are:
1. What affect, if any, does this large roundover have on the baffle step response and crossover compensation?
2. How to veneer the front baffle?

This is the web page that got me thinking about baffle step "loss" and the roundover.

http://www.trueaudio.com/st_diff1.htm

[Danny Richie]

With the 3/4" material use on the X-LS I think the largest radius you can use is 3/4". If you increase baffle width then you can add a larger radius but that is going backward. The smaller the baffle size the better. And the radius has more effect on the ranges above the area of baffle step loss. So rounding it over really doesn't effect the step loss. It's still the same width.

If you add a radius on the sides only then you can roll a paper backed veneer all the way around the four sides and seam it in the back. If you radius the top and bottom edges too then that's out.

[Oscillate]

"What are the pros/cons of ported or non ported?"

If you are building the smaller, book-shelf size X-LS, then that volume is
optimal for the sealed version. If you wish to go ported, the X-SLS tower
has the optimal box volume.

Reference link 1
Reference link 2

[Todd Willhoit]

Thanks Danny.  Using the measuring tool in Acrobat, I find that the perimeter of the tweeter is 1.225" from the edge.  The woofer is less.  I doubt 0.025" overcut at the tweeter will be very noticeable.  I can keep the baffle the same size and use a stop cut to avoid interfering with the woofers.

And the radius has more effect on the ranges above the area of baffle step loss. So rounding it over really doesn't effect the step loss. It's still the same width.

This is exactly what I am interested to know.  If I understand correctly, baffle step "loss" is actually diffraction "gain" or baffle step "gain".  Edge diffraction at shorter wavelengths results in a gain at higher frequencies.  A larger roundover results in an apparently smaller baffle and less gain.  The downside would be that, if the crossover already accounts for the baffle step "loss" (ie. flat response), then the larger radius/smaller baffle would result loss at higher frequencies.

Is this correct?

[Todd Willhoit]

"What are the pros/cons of ported or non ported?"

If you are building the smaller, book-shelf size X-LS, then that volume is optimal for the sealed version. If you wish to go ported, the X-SLS tower has the optimal box volume.

Are the X-LS stand-mount cabinet plans "non optimal"?

[Danny Richie]

This is exactly what I am interested to know.  If I understand correctly, baffle step "loss" is actually diffraction "gain" or baffle step "gain".  Edge diffraction at shorter wavelengths results in a gain at higher frequencies.  A larger roundover results in an apparently smaller baffle and less gain.  The downside would be that, if the crossover already accounts for the baffle step "loss" (ie. flat response), then the larger radius/smaller baffle would result loss at higher frequencies.

Is this correct?

The round over will effect the surface reflections in the upper ranges only. It does not effect the step loss.

[Todd Willhoit]

Exactly, because step loss (low frequency) is only a loss relative to the upper high frequencies.  In other words, a subwoofer has no step loss.

If the round over reduces the surface reflections in the upper frequencies, won't the perceived step loss be reduced?  Less upper frequency diffraction = less gain in the upper frequencies = less "loss" in the lower frequencies.

My understanding is that, on the baffle, the woofer is operating at 4pi and the tweeter is operating at 2pi.  Increasing the radius at the tweeter, thereby reducing the perceived width of the baffle, moves the tweeter toward 4pi which, in turn, reduces the perceived low frequency step loss.

[Danny Richie]

If the round over reduces the surface reflections in the upper frequencies, won't the perceived step loss be reduced?

No, the step loss is not really effected by the rounded edge and the amount of loss is the same.

A standard mini-monitor like that will have a step loss that starts at about 800 to 900Hz. Those wavelengths are 14 to 15" long. So they are not effected by the round over.  And the range that the tweeter plays is well above that. And where the edge or lack of edge effects the response is much higher.

Increasing the radius at the tweeter, thereby reducing the perceived width of the baffle, moves the tweeter toward 4pi which, in turn, reduces the perceived low frequency step loss.

The tweeter doesn't play down low enough for it to really play into 4pi space.