EconoWaveguide Utility Large Advent Build Thread

This thread documents the conversion of a pair of Utility Large Advent speakers to accept a waveguide, a Selenium driver and associated crossover.
The EconoWaveguide project is extensively documented in this thread:

http://audiokarma.org/forums/showthread.php?t=150939

It is up to 180 pages as of this writing. I decided to document this particular conversion in another thread because it is intended to be a guide for others who wish to do this conversion, and in the time it would take to glean the info out of 180 pages of posts, you could just about build a pair of anything.

Note that I am not 'supporting' this project. I'm going to put everything useful that I know about this into this thread. If you PM me and ask for advice about this or similar projects I'll probably point you back to this thread.

I chose the Utility Large Advent speaker for conversion for the following reasons:

They're common and inexpensive. Just about anyone should be able to find and afford a pair.
It's a full range unit with plenty of deep bass, a very important consideration for me.
Relatively easy to drive.
Large enough to be easy to work on.
Decent, heavy cabinet that doesn't need bracing and has room for the waveguide
To my ear, the tweeter is the weak point of this unit so it's a natural for upgrading

The parts:

One pair of Utility Large Advent cabinets. Other Advent cabinets will work, but the New LA with the rounded 'bullnose' edge is too narrow as is.

One pair of Advent woofers in good condition. I used the metal basket woofers because they're not a flaming pain to re-foam like the Masonite ones. The Masonite woofer will apparently perform very similarly to these Jensen-made drivers.

One pair of waveguides, Pyle type PH612.

One pair of 8 Ohm compression drivers, Selenium type D210Ti. The model 220 is said to be equivalent for this purpose. I chose the 210 because they were under $25 each at the time, which is a screaming bargain for a quality compression driver.
Note that as of 12/08 our preferred parts source for these drivers, Parts Express is no longer showing the 210 driver in the catalog. They are showing the 220 driver as a 'replacement' for the 210. We think this means that the low cost driver option is being phased out.

EDIT
The D210Ti is now out of production. Builders should seek out the D220Ti instead. This project applies to both, but the 220 has certain technical advantages.

The PH612 waveguide used in this project is now available from Parts Express, which also stocks the D220Ti driver and all of the crossover components.
END EDIT

CROSSOVERS
One pair of ZILCHLAB EconoWave crossover boards. These were built out with the basic 'low sensitivity woofer' version of the parts complement.
Please see the main thread for extensive discussion of the crossover.
(Crossover)
http://audiokarma.org/forums/showpost.php?p=2281446&postcount=2529

If you use the JACKLAB EconoWave crossover boards, please consider the phasing of the woofer and horn carefully. The documentation for the boards provides guidance on this issue.

A note on the crossover parts. The most expensive part of the crossover is the 1.5mh woofer choke. I just pulled the woofer choke out of one of my ULA speakers & measured it. It measured approx. 1.58mh. That could easily be used in place of the 1.5mh if necessary. It has slightly smaller wire and would have higher DCR, but that's really not a major issue here.

An inductor of slightly higher inductance than required can frequently be 'unwound' a few turns to reduce it to the required value. An inductance bridge or LCR meter is required for this to work properly.

If like me you have tons of caps and resistors around, and you get lucky and find inductors in the range of 1.4mh - 1.6mh in your Advents, then you could get away with scratch building your crossovers with only the purchase of the LPads and the .6mh inductors.

I scrap out a lot of vintage speakers. I always preserve the Lpads and inductors and I have re-used them in the past for new projects. I'll keep the caps from an old crossover if they're film and of decent size. Old NP electrolytics always get tossed.


About 2 lbs of fiberglass to fill each cabinet.

2 pairs speaker binding posts, some Masonite for terminal panels, misc. wire, connectors, etc.
I built mine with fuses and 1/4" TRS input jacks to accomodate loaning them to musician friends.

The finished speaker is shown below:

Preparing the cabinet

Remove the drivers and all of the fill. Remove the crossover board. This will probably require a chisel to scrape the glue off of the inside of the cabinet where the crossover board is glued on. This surface has to be clean for the new terminal panel to be attached to.

Re-foam the woofer if necessary. There's enough info on re-foaming Advent woofers on AK to spend a week reading it all.

The waveguide requires a cutout approximately 5" X 10". Don't make it too oversized, as the screw holes come close to the edge of the cutout and you could run out of material to hold screws if you get too generous with hole size.

Ideally, the waveguide would be placed as close to the edge of the woofer as possible in ortder to reduce the center to center distance of the drivers to the smallest practical amount. With the ULA cabinet this would leave half of the original tweeter cutout needing to be blocked or filled in to place the waveguide lower. We discussed this and compromised on the configuration below. If you don't mind filling in the original tweeter hole, there are some theoretical advantages to placing the waveguide as low as possible.

My pictures below show dimensions to measure for the cuts. Measure everything twice at least. Better to re-mark than fix a bad cut. We're using the top edge of the original tweeter hole as the top edge of the new cutout. This is 2 1/2" down from the inside of the rim. I measured the sides of the new cutout as 1 3/8" from the insides of the rim. 1 1/2" is OK.
I made the cuts with a small jigsaw with a 3" X 1/4" wood blade. I covered the surface with painters' tape before making the cut marks for contrast. I taped the edges of the cabinet to prevent gouging the surface. There isn't a lot of room to maneuver the saw so I had to use the smallest saw tha tI could find. I was prepared to make the side cuts which are very close to the rim of the cabinet by putting the saw up on the rim and using a long blade but this was not necessary.

After making the cutout and verifying that the waveguide would fit I put it in place and marked the positions for the mounting screw holes with a felt pen through the holes in the rim.

For the T-nut holes I used a 7/32 drill. I pressed the t-nuts into place with a pair of vice grips, placing a piece of scrap aluminum on top to prevent gouging the surface. Make sure to get the T-nut is flat so the screw will sit vertically or it will not align with the hole in the waveguide rim. Never mind how I know this.

<EDIT> When I built the second speaker I decided not to use T-Nuts for the horn. Instead I drilled 1/16" pilot holes and used #8 X 3/4" wood screws. This worked fine, even when I had to remove the horn later to fool with the wiring.
I now think tha tT-nuts are more hassle than necessary for teh horn mounting unless it's going to be removed multiple times. Just use wood screws.
<END EDIT>

Sure enough. I just finished one speaker and set it up to play. There's an annoying resonance in teh midrange. I had to tear the woofer out. Some of the surround glue separated, which is an easy fix but for now I'll drop in another woofer. I'm glad I used T-nuts but the putty isn't looking too wise at the moment.

Okay, that's the cabinet. Now you need a panel to hold terminals on the back. I used a scrap piece of Masonite paneling because it was thin, has a smooth surface and was already leaning against the band saw. I cut a generous piece with an extended section to hold the Lpad. My Lpad has a short 'reach' so it had to be mounted on a thin panel and protrude through a hole. I drilled a 1/2" hole through the back for teh shaft and used a spade bit to cut a shallow relief on the inside for the mounting nut. Guess I forgot to take pictures of that.

Anyway, align the panel inside the cabinet and from the outside trace the shape of the cutout in the cabinet. In this area drill all of your mounting holes. In most cases this will just be speaker terminals. I added a 1/4" TRS jack and a fuse holder because a musician friend asked to try these when they're done. The 1/4" inch jack is how a lot of pro gear is connected and the fuse holder is because I'm rebuilding this guy's blown up Phase Linear 700 350 WPC amp and I don't want that thing unleashed full force on my speakers. Maybe I should find a locking fuse holder.

Anyway, after drilling the holes for speaker terminals, tape the panel in place in teh back of the speaker and drill small pilot holes for the screws that will hold it in place. I think I used a 1/16" drill and #8 X 3/4 screws.

Attach the terminals and lpad to the panel. Solder wires to the crossover board from teh terminals and the Lpad. I left 12" of leads for crossover positioning. For the leads to teh drivers I put push-on terminals on the woofer leads and tinned plain ends for teh tweeter leads. Both got a red sleeve for teh positive terminal 'cuz I'm fussy that way.

On the back of the crossover board I put some 1/4" thick self-adhesive felt at the ends between the mounting holes to cushion it against the speaker back panel. Standoffs are another option. I used the actual board to mark positions and I drilled 1/16" pilot holes for #6 X 3/4 wood screws.

Put rope caulk or foam seal around the hole area on the terminal panel and the Lpad hole.

Screw everything down, being careful not to stress and crack the crossover board.

Almost done.

Pull the driver leads through the driver holes and tape them to the sides of the cabinet, otherwise you'll bury them when you add the fill. I used 2# of fiberglass because that's what was in there and the consensus of opinion favors the farbenglas solution. Lay it in, leaving room for the back of the compression driver, which goes back over 6" and room for teh depth of the woofer.

<EDIT> I later went back and added more damping material. With the 2# of fiberglass they were too boomy for me and others felt the same way. I added about 3/4# of dacron material and I think this is better. No boom and plenty of bass. I'd recommend when you 'tune' your cabinet stuffing you're better off starting with a lot and removing some if it's overdamped. I ended up with more material in there than I thought I would need.
<END EDIT>

Rim the driver holes with caulk or foam strip. Attach the leads to each driver, observing polarity and screw them down.

Reach carefully over your left shoulder with your right hand and pat yourself on the back. You just built an EconoWaveGuide Utility Large Advent speaker.

Place holder

Update from initial listening to the first speaker.
We have bass. We gots bass like McDonalds gots hamburgers. There's plenty strong output at 40 hz. These will have to be placed high if they're against a wall, or near the floor if away from the wall. The wall/floor junction (low, against wall) gives too much support and makes them boomy. This may change as the under-used refoamed woofers get some exercise and break in more. I'm running the horn attenuator at about the 70% position for good balance. This may change, but probably not by much.
It's a nice sound. With a new pair of speakers, what I notice first is what's right, then later the flaws become noticed. The midrange seems smooth. The presence region (1,500 - 3,000) may be a little depressed. They're definitely not forward in the presence. The shrillness and aggressiveness that so many of us hate in cheap horns is absent. The top end is very smooth, maybe on the sweet side. I'm convinced that this is a horn that would convert horn haters.

<EDIT>
A later change to the phasing of the drivers seems to have taken away the presence region depression. Maybe it was driver break in too, but they no longer sound 'distant' like they did originally.
Note tha ta later change to the damping in the cabinet removed the overactive bass bump. See above for that issue.
<END EDIT>

Place holder ii

Mrs. Bauhausler had some constructive criticism upon hearing Unit 1.

1) Put a grille on it.
Good idea. I was also thinking that the baffle should be painted black so it will look better when played with the grille off.
I need to get some grille foam from The Foam Store up the street for my Isobariks. I think I'll get extra so I can make foam grilles for these speakers as well.

2) Good bass. Maybe too good.
I agree. It sounds very full and might need more damping than it has. We'll see.

3) Doesn't sound bright like audiophile speakers (I'm paraphrasing).
I agree. Top end is refreshingly sweet. If I was running these with a tube amp with a soft top end I might even reach for the treble knob and add a little air back in. Gotta try that when the 300B amp gets back here.

FURTHER BUILD NOTES:

After auditioning these for a while and demo-ing them for the December SMAC audio meet I decided to make a changes.

1) I removed the drivers and added more stuffing. They were definitely boomy as originally built. Sounded underdamped and peaky in teh bass when placed near a room boundary. To each cabinet I added about 3/4# of Dacron batting. This was a guess as to the amount needed. It took the boom out of the bottom end but there's still plenty of bass. maybe a little less or a little more depending on the application but this seems about right.

I can't tell you how much to stuff your cabs but I recommend that you start heavy and remove some if it's over damped. Going by typical rules of thumb is likely to result in under-damping rather than too much.

2) Phasing of the midrange. This was due to a labeling issue with the crossover boards. I had to open up my cabinets and reverse the leads to the compression drivers. U sing the polarity labeling on the boards with these drivers resulted in out of phase signals in the crossover region and probably a dip in response there. It didn't make a huge audible difference but the presence seems to have come forward a bit.

3) foam plugs in the horn mouths. These are made of open cell foam of the sort used for water filters and speaker grilles. I was given a pair and I installed them. Again, there was no huge immediate audible difference except maybe it took a little sibilance out. Here's a link to that discussion:

http://audiokarma.org/forums/showthread.php?t=150939&page=194

Great thread! Love the photos! This is looking to be majorly helpful. Thank you. I will start on my Utilities, likely with this thread printed out for ready reference, just as soon as I finish the ZLH-17 project.

I note your use of T-nuts for securing the waveguide. Did you also attach the woofer with T's or just standard speaker screws?

Nice thread. I still have yet to finish my Barzilay waves but I do have a beat up pair of OLA's I got from Westend that would make a nice practice project.

How do they sound compared to the originals?

Paratima said:

Great thread! Love the photos! This is looking to be majorly helpful. Thank you. I will start on my Utilities, likely with this thread printed out for ready reference, just as soon as I finish the ZLH-17 project.

I note your use of T-nuts for securing the waveguide. Did you also attach the woofer with T's or just standard speaker screws?

Click to expand...

I used T-nuts for the woofers as well, and a good thing because the first woofer had an odd noise from incomplete surround glue so I had to change it. Wood screws wear out particle board in a hurry.

The T-nuts are 8-32 and the screws are 1 1/2" long. 1 1/4" would probably be fine. These T-nuts are smallish but were a good compromise for both drivers as the woofers don't weigh much.

and how do they sound? nice job, bauhau

shrinkboy said:

and how do they sound? nice job, bauhau

Click to expand...

I think the one finished speaker sounds pretty good. It's difficult to know for sure until there's a pair and the woofers break in. Certainly nothing obviously wrong or bad yet. There's definitely plenty of bass. Really solid down to 40 hz. This is a true full range speaker.

DENNYDOG said:

Nice thread. I still have yet to finish my Barzilay waves but I do have a beat up pair of OLA's I got from Westend that would make a nice practice project.

How do they sound compared to the originals?

Click to expand...

I think it was worth the work but then I'm the guy who guts and rebuilds Ampzillas for fun. The total investment was probably $200 for everything that went into them plus maybe 6 hours for teh actual work.
I like the Large Advent a lot but I've always thought the tweeter was teh weak point and no I'm not saying that to invite arguments here. This waveguide and driver are way superior to the original tweet to my ear. Into the bargain, the WG plays lower so the woofer puts out less midrange than stock.
I'm going to go build the other one as soon as I figure out why smoke just poured out of this tube amp.

Is the XO something that can be purchased? This is the biggest stumbling block for me to start playing with the E-wave thing.

kfa888 said:

Is the XO something that can be purchased? This is the biggest stumbling block for me to start playing with the E-wave thing.

Click to expand...

See the E-wave thread lke three pages back. An AK'er had circuit boards made and has some available. Also, Zilch has posted the parts list for the crossover as well..Easy, Easy!

marantzfan said:

See the E-wave thread lke three pages back. An AK'er had circuit boards made and has some available. Also, Zilch has posted the parts list for the crossover as well..Easy, Easy!

Click to expand...

In one of my first posts in this thread there's a link directly to the posting by JackGiff about the crossover circuit board purchase.

Thanks, Bauhausler! Great Work! :thmbsp:

Heck,if I had the dough,I'd like a pair.

Bauhausler said:

I think the one finished speaker sounds pretty good. It's difficult to know for sure until there's a pair and the woofers break in. Certainly nothing obviously wrong or bad yet. There's definitely plenty of bass. Really solid down to 40 hz. This is a true full range speaker.

Click to expand...

Seems to be a great upgrade to me.Maybe what you've done is merge East and West coast sound? Deep bass from the East,mids and highs like the West?
Hope no one thinks the above statement is funny or worse,heretical.

I'm intrigued,

Bob

...fussion speakers...I like it!