Zaph Waveguide Questions & Issues

[EDDIEMUNSTER]

Hello out there. I just completed a set of Zaph's Waveguides and have a couple of issues I could use some advice on. Since I had some fiberglass insulation kicking around and I used it rather than the carpet liner he uses in the design. I read in a speaker building book that pink insulation was one of the best speaker dampening materials. However, the bass is so loud that I have to turn down the base on my preamplifier. One speaker is in the corner about 20 inches from both walls and the other about 20 inches from the wall. Perhaps I stuffed too much insulation in the speaker? Would that cause a massive base overload? Perhaps these speakers need to be in the center of a room?

The other problem I have is that during some recordings I hear these high frequency pops/cracks in the tweeters. It is odd that it only happens on some recordings. I tried two different CD players and the same thing happened. Perhaps I have a bad set of tweeters? (Seas 27TDFC )

Any ideas? Any help would be greatly appreciated.

Cheers,


Doug

[Zaph]

Could you show me a measured system impedance curve?

I'd like to see that before I offer some help. Without test data like that, troubleshooting could likely go on forever - and endless string of "try this, try that" and I've had my share of those over the years. If you have a woofer tester, maybe one of these or one of these, grab a quick impedance curve. If you don't have one of those or some other method, perhaps grabbing some data using the old brute force method and creating an excel spreadsheet chart would do.

The number one way to check a speaker system against a reference design is with an impedance curve. Number two is with a response curve. I'll stop back here in a few days to see what you can come up with.

[Dave Bullet]

Regarding the pops an cracks, do they happen randomly in the recording (or always in the same place)? Do they happen after your system has warmed up or at any time?

Regarding your whole system - are the speakers the only part you've changed?

Regarding bass response - corner loading one speaker (you mentioned one was in a corner 20 inches from both walls) - will increase bass response. Can you try making both speakers equidistant from all walls?

What happens to the bass response when only one speaker is playing? Try and tune in a radio station with bass heavy music, switch to mono then right / left balance between your speakers. You might find the extra bass is coming from the corner loaded one pinpointing the problem.

Lastly, double check all crossover / driver wiring. IF you can't be bothered - switch the speakers and repeat the above test to see if the extra bass "follows" the speaker (indicating the speaker is at fault) or stays in the same location (indicating speaker placement is the problem).

room placement / speaker positioning can affect the sound drastically.

Cheers,
David.

[Tenson]

If you find there are no problems with the speakers you probably just need to tune the ports lower to account for the room gain of corner loading. I did this with some speakers I just built and it works very well.

Either make the ports longer, or if you don't have the room, make them a little narrower.

[EDDIEMUNSTER]

Thanks for the help and suggestions guys. After further playing today the pops seem to have gone away for the most part. The discs I have heard them on are older and may not be good pressings. This waveguide/tweeter combination plays more detail than other speakers I have owned. I needlessly panicked a bit yesterday.

As for the base, the corner speaker is the problem. I think that rear ports have to be in a location away from walls and corners. I may try dampening the walls beside and behind the speaker on that side. For now I have to turn the base down a bit to compensate for the extra umph in one channel. Unfortunately, I do not have the tools and equipment to measure speaker performance but may invest in some in the near future.

Overall I have very happy with these speakers. My previous speakers were single drivers using Audio Nirvana 8's. They sounded good find for certain music but nasty on some. The Waveguides have incredible bass punch and the high end is superb. This is a great project. I also made the ZAPH B3S single driver speakers and am working on a set of Greg Givler two ways. My most ambitions project to date is a set of Needle column speakers designed by Jim Griffin (sound just fine!).

Thank you very much John for an amazing site and great projects. I am not a speaker expert and these projects are relatively easy to build and sound great. I can't imagine how much I would have to pay for a set of speaker like to the Waveguides on the retail market!

Can't wait to try a few of your other projects (My wife isn't as enthusiastic. This place is starting to look like a speaker graveyard) Anything new and different on the horizon?

[Zaph]

Well, maybe it is just the corner loading, but I'm usually pretty skeptical. You'd be surprised how often crossover wiring problems occur, and a impedance curve shows that issue immediately. Even for people who just build kits or other people's designs, I still recommend a woofer tester as a nice troubleshooting and testing helper.

Dave and Tenson have good ideas. If anything you could stuff socks in the ports and see what that does.

The popping sound is something else. I've heard fried capacitors crackle... Overpowering caps is of course one way to fry them, but more common is overheating the leads during soldering.

[Tenson]

Thank you very much John for an amazing site and great projects.

[/B]

Just like to add my thanks Zaph, I've not built any of your designs but I have found your driver measurements very enlightening, not to mention useful!

Good luck Doug

[EDDIEMUNSTER]

Thanks John. I did test both crossovers before installing them and they sounded ok although I tested the drivers on the bench without enclosures. I will try the sock on the left side.

What do you recommend for reasonable cost speaker testing?

Thanks again.


Doug Woodliffe

[Dave Bullet]

Eddie,

Essentially, you need:
1. a PC with a full duplex soundcard
2. an electret microphone- look at digikey.com for a panasonic omni-directional electret mic (dirt cheap) with a reasonably flat 20Hz - 20KHz response
3. a mic-preamp (to bring the electret up to line level) - There's an active thread here: Easiest software to measure the Frequency Response
4. an impedance measuring jig / cables - google claudiio negro or eric wallin jig
5. speaker measurement and modeling software. eg, www.audua.com

The above would get you going "on the cheap".

Cheers,
David

[Tenson]

Is there anywhere to buy a pre-made speaker testing jig for use with Speaker Workshop etc..? (other than the ones Zapg posted which seem like more than just a jig)

I know it can be DIY'd but I just don't feel like it

Cheers,