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A Collaborator is Needed for My Curse of the Yellow Cones
First off, I realize the timing for this request isn't great. With that in mind, here we go. I have a confession to make. I do not have measurement gear. Never have. Any time I've gone "off the reservation" I've used carefully chosen drivers and measurements and the "Speaker Designing with Software" pointers from Wolf, Paul Carmody, et al from the PETT board as my starting point. Sometimes it works, sometimes you tear down and start over. The keepers have been a blast.
I was content with this approach until a few months ago, when I not only got laid off, I also lost the laptop with all my history of work on it. I am not a Windows guy at home. So now I have just a couple of projects left to complete before I hang up the soldering iron, but I can't do that without some assistance. Here is what I have left to finish:
At last year's DIYIA someone had a build with the Dynavox LW6004HR-N honeybomb woofers that I really liked. So when they were deeply discounted last fall, I buckled. I currently have boxes built that will be vented and should net about 21-22L.
The second project I'd like to finish uses the HiVi F6. The vented boxes should net at about 18L.
I can use any of 3 tweeters to finish this pair of 2-ways. I have avoided cutting the holes since they are not the same diameter. The tweeters:
- Dayton RST28F-4 (These were '19 DIYIA door prizes and need to be measured and used first, just to see if they even match each other, let alone any other RST28's.)
- Peerless DX25BG60-04 (Because JR made me do it.
) - Seas 22TAF/G Metal Dome (These are lightly used and require a higher XO but are very nice tweeters.)
So, there is a little work left to do on the cabinets, but not much to get to mounting drivers. If there is anyone out there, preferably in IOWA (I'm in the Des Moines area) who could help out a poor speaker cobbler with the measuring voodoo that makes these sing, please inquire or reply on or offline so we can work out possible next steps, recommendations etc., etc. If I could even get one pair playing for the Ankeny show I would be very happy. If not, maybe an Ankeny how-to demo if it's not too time consuming??? [thinking out loud there...]
Thanks for looking. You guys are great.
Best Answer
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Yes- the 0.1uF aids the rolloff only, as the rolloff of the F6 just needs to be attenuated and rolled off. It really is not the offending part. I had a 1.5mH on the LP in my Nephila, so it should not change much. If you want the same BSC, just attenuate the tweeter more.
You can try the notch in either before-driver or at-input positions. It would in my opinion go better first, as that is how I had it. This way the nodal position has not changed.
Answers
Hate to hear about the job situation. Our place employed roughly 1500 in 2010 when they made the announcement we would be downsizing. We are now at 203 with no bottom in sight. Keep your spirits up cause something will come along and it might even be better.
Although others have had good luck, I never could get a bad pair of rst28f .zma to match.
Kornbread really likes the looks of that Dynavox woofer and the solid wood/double thick baffle construction. Those are going to look sweet.
Didn't you have a LEAP/MAD design for the F6/22TAFG? I would go that route, and let the F6 midrange shine bright.
The Dynavox will likely be easy with the DX25BG60.
InDIYana Event Website
Wolf, your elephant memory is correct, and that design can still be reassembled as the XO and cabs are still intact. However, once I heard the breakup of the F6, I just couldn't unhear it. The fix COULD be as simple as a cap across the inductor. Dunno.
If you are referring to the resonance at 1.1k, then a simple notch is all you need. They can be a bit honky without it. The rolloff is actually fine, and I used a 0.1mH across the main lowpass coil to steepen the rolloff.
47uF||0.47mH||8 ohm in parallel, placed in series with F6.
InDIYana Event Website
For the record, the woofer XO has a 1.0mH coil, followed by 15uF and 4.7z to ground. I assumed that what I was hearing was at or above the XO point as shown in area "B" below. You are saying that wiggle "A" may be the issue and can be smoothed with the 3-component filter? Would placement be between the pseudo-zobel and the woofer?
Any nastiness coming from the "B" area could be damped down with the 0.1uF across the 1.0mH coil, correct? Would it be advisable to deploy both mods, or evaluate one versus the other?
If these fairly painless additions solve the concerns I had with the original design I'd be very happy moving it to these roomier F6 cabinets. The previous boxes were ~15L, and not especially attractive.
Awesome, that would just leave me looking for a solution for the Dynavox LW6004HR-N honeycomb woofers, paired either with the Peerless DX25...'s or the Dayton RST28F-4's. Hopefully things will normalize by fall-> winter building season.
I coulda sworn I responded to you saying place the LCR before the lowpass preferably, but you can try both at input and before driver if you wish. After the xover changes the nodal relationship as I used it in the Nephila design. The LP coil in my Nephila was a 1.5mH if you want the same BSC relationship. You may have to increase the tweeter pad if you follow that scheme.
InDIYana Event Website
You did. An odd feature of the "QUESTION" threads is that I'm given an option to indicate whether responses answered my question or not. Yours did, so I marked "yes" and it was immediately moved to the top of the thread. (see above) Given the choice, I would not start the thread this way again, since it tends to DEAD END the thread. It's basically meant for very simple questions, not a general inquiry.
Thanks, Wolf. I'm good on the F6 unless I run into deeper issues.
Not that this answers your question in any way, but wanted to add that I have a semi-started project that pairs that HiVi F6 with the RST28F mounted in a Visaton R148 waveguide. My initial thought was to be able to cross the tweeter/wg low enough that super steep xo slopes or notches would not be necessary to tame the "B area" nastiness. I had still planned on deploying whatever xo components needed to fix any "A area" wonkiness. My project is at this point going to use the manufacturer's recommended 15 liters tuned to 45 Hz with all walls lined with foam. How did you decide to go with 18 liters and what is your targeted tuning freq?
You really don't need to tame area B very much. Everybody wants to squash it because it looks bad. Thing is- it sounds good just attenuated to nominal level.
InDIYana Event Website
Well if you consider their IB baffle response then add another 2 dB peak at ~1k from a 9" wide baffle...
Yeah- that would be bad. That 900-1.1k region really gets honked off. I honestly thought I was being overzealous with an 8 ohm resistor in that notch, but it proved to be just right.
InDIYana Event Website
There are a couple of reasons. The size of the F6 flange plus a 3/4" chamfer on each side of the baffle puts you at a 9" width. Because of the stock I used (bargain composite oak from Menards) leaving cabinet depth at 11-1/4" meant no addition cuts in that dimension. (That's a significant issue when you're as mistake prone as I am.) Then just general aesthetics end up giving you a pretty large cabinet. In my initial draw-up I was shooting for 16L. Once everything was assembled I realized both projects wound up a bit roomier than I'd targeted.
Also, a couple of the successful F6 projects that I'm aware of used a bigger box or tower. My target tuning was going to be for ~46, but the ports aren't cut yet.
An F6 and a waveguide is going to give you a pretty good sized baffle no matter how you slice it. Not meaning in any way that it's not a worthwhile pursuit. I'm sure it will be.
Yeah, pretty large baffle.