Forums https://www.decware.com/cgi-bin/yabb22/YaBB.pl SPEAKER FORUMS >> Zen Master Series Loudspeakers >> Open Baffle rear firing tweeter https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1717349113 Message started by Geno on 06/02/24 at 18:25:13

Title: Open Baffle rear firing tweeter Post by Geno on 06/02/24 at 18:25:13 I wanted to to make the open baffle folks aware of an upgrade (ymmv) We found an article on the internet, discussing a certain open baffle design. I am attaching a link to the article. There is a lot involved to the guys design, but what we got out of it, was his use of a rear-firing tweeter. I think that most people decide to add a tweeter to an open baffle, to add a bit of top-end sparkle, and that can be a good thing. But this design incorporates the tweeter into a more seamless blend of extra treble. The addition of this tweeter has made a pretty significant improvement to my overall sound. When I first read the article, I really keyed in on the tweeter addition.  I went ahead and ordered the tweeters (PRV Audio WG175Ph) and got them attached to the back of my baffles) I was not sure how to regulate the tweeter, so with the initial intention of adding top end sparkle, I started with a 1.5uf capacitor. I was startled at the result. This added another dimension to the overall sound. Lacking real technical knowledge, I got in touch with Palomino, to let him know about this (we have similar baffle designs). He ended up getting the tweeters to try, and also liked the result. However he took things a big step further, by using a higher value cap, and more importantly, reversing polarity in the connections from tweeter to full-range drivers. Yep - that was the ticket. We pretty much decided on 4.7uf caps, but have also used 6.8uf. I like both, and still rotate back and forth. Here is the link to the original article. The fellows name is Perry Marshall. https://www.diyaudio.com/community/threads/live-edge-dipoles-1-at-parts-express-2023-speaker-design-competition-updated-design.405104/ He states that the tweeter sounds best at a 30 degree angle up. I just looked at pictures of the back of his baffles to make a guess at height from the floor, and distance from the back baffle face. I am about 19” from the floor, and about 4” from the rear of the baffle (4” to top edge of tweeter face) My baffles: The authors baffles:

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/08/24 at 15:27:15 Thanks for sharing this, Geno. I’m going to give it a try with some tweeters I have laying around the shop.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/08/24 at 17:32:39 Hey Gilf. With my setup, it was a pretty significant improvement. I hope you will have a similar result. Best, Geno ***Tom, you out there? Be cool to hear your evaluation of this.

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/11/24 at 15:21:08 Yes, I got a great lift from this inexpensive mod.   I have been trying for years to get more front to back layering of my soundstage.  Everyting seemed more pressed to the back wall.   These tweeters significantly helped with the laytering.   I have a second OB system and it helped that system as well.

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/13/24 at 22:53:01 I wired up a set of these and initially just set them on the w-15 basket. The angle was about 63*, and using an Audiophiler 4.7 uf cap, which needs to break in. I found it nice at first listen but fatigued my hearing quickly. I just made a quick wood block to screw them to in order to get the angle closer to the recommended 30*. The imaging is really nice. My ears are kind of shot at the moment so I’ll let the cap further open up and comment once my hearing has rested.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/14/24 at 00:34:19 Very cool, Gilf! Keep us posted on the progress.

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/14/24 at 01:34:27 You might need to add a resistor to lower the efficiency of the teeeter.  If it’s the one we have it’s over 100db efficient and the F15 is below that.  Sorry forgot what it’s rated at.  I think you can have a higher efficiency teeeter but it shouldn’t be too much higher.

Title: Re: Open Baffle rear firing tweeter Post by Donnie on 06/14/24 at 02:18:38 I'd just put some foam on the inside of the horn to see if that would tame it down. Even some fabric might do the trick.

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/14/24 at 03:07:41 Palomino and Donnie, those are all good recommendations I’ll have to try. Geno, I recall you have P-10’s; Palomino what drivers are you using? I did some chores for a few hours with ear plugs in and let the caps soak a little, but still too much for me. Maybe a resistor or dampening foam would help. I switched out a few different well broken in caps from the parts bin and settled on some 2uf Solens. I’m still hearing a phasing issue though. I did reverse the phase as recommended but I tend to be sensitive to phase and fatigue. Decades phase hunting in recording studios… My general impression with the 2uf caps and the F15s is that it puts the high hat in a really nice spot. Everything else is slightly off yet but I really like what they are doing for cymbals and especially the bell of the hat and ride cymbal. The sound stage is wider and the sweet spot is bigger, but the image is also slightly smeared and the sweet spot isn’t as tight. To be fair, I’ve been tweaking my room and speaker placement for years to get it dialed in just right, so one afternoon with these tweeters isn’t likely to get it right off the bat. I think the next step will be moving the location of the tweeter to align it better with the drivers. I’m curious how your guys’ experiments are coming?

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/14/24 at 11:30:30 I have P10s as well.  When I measure, the tweeters don’t add so much to the highs.  For me it’s all about soundstage.   Just this week I watched a YouTube video which featured an acoustics expert.   His recommendation was 15% of total surface area absorbers and 15% diffusion.  He also interleaves absorbers and diffusers. So I removed some diffusers and alternated absorbers and diffusers along the side walls. Interestingly enough I did get a more room filling, wrap around sound.  I’m trying to figure out if I really lost anything in the process.  I think it’s some of that front to back layering definition which was so magical so I may go back to what I had before. I experimented with super tweeters a few years back.  I had three different resistor sets which I swapped in and out.  Despite padding them down a bit,  I never got rid of the fatigue factor so I pulled them out. But I still had the little platforms I built which slid over the top of my baffles so I used them to mount upfiring tweeters.   At first a soft dome and then later an AMT (which Steve is experimenting with now). The upfiring tweeters provided more air, but I was still missing that front to back layering.  Then Gene recommended the rear firing horn tweeter which gave me that in spades so that is what I am experimenting with now. In my second system I have C10s over 15" Hawthorne Augies in an larger, but untreated room.  I took the soft dome tweeters and installed them rear facing at the same angle and got better front to back layering again.  They are not quite efficient enough so I am going to try to find a horn tweeter that's a little higher efficiency and better matched to the C10s.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/14/24 at 15:12:19 Tom, "Front to back layering" is a good description. For me, the overall frequency spectrum is pretty evenly spread. Hard to imagine it being much better. Your point of using a resistor, along with the cap, raises a question. I am in the process of building new top baffles for my Betsy alnicos, so that i can listen to them periodically. They are rated at 92.4db. What value resistor could I try with the capacitor, to match the tweeter to the Betsy? And also, how would I wire that-- resistor between the cap and the Betsy?

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/14/24 at 15:51:07 Thos are two questions I don't have good answers for.   I remember that I found a calculator online that I put some information in and got a value.  I can see if I can find it again. Also, given we are wiring out of phase, I believe you would have it before the capacitor on the negative side.

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/14/24 at 15:58:07 Ideally, you'd build or buy a L Pad which I think helps keep the speaker impedence from changing.

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/14/24 at 17:35:06 I would start with an 8 ohm resistor before the capacitor on the negative side which should give you about 3db of cut.  I think…  ;D

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/14/24 at 19:02:01 Thanks Tom and Gilf. This type of thing is way past my knowledge base, and why I default to Tom for help. But I have learned a lot, along the way. So, basically, am I trying to get the efficiency of the tweeter, to better match the efficiency of the Betsy? And if that is the case, I would want to attenuate the tweeter, roughly 11db - the difference between the Betsy at 92.4 db and the tweeter at 104db?

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/14/24 at 20:05:40 It is my hunch that you can get away with the tweeter being a little hotter than the main driver because it is pointing backwards and you eventually hear reflected sound so It won't be as loud as if its pointed directly at you.   I'd have to go back and compare specs but I think the tweeter on the P10 setup is more efficient that the P10. Edit: I just checked and its 108 vs 103 for the P10.  I just picked up some 104db efficient tweeters to go with the 99db efficient C10s.  The soft domes I had were only 96db and I don't think they are loud enough when pointing backwards.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/18/24 at 22:24:46 Tom and Gilf, I'm gonna try a "fixed" L-pad, first. I used a calculator to figure, 'R series' and 'R parallel' resistors, in tandem with the capacitor we have. The combo should cut about 10 db or so. We will see how that sounds, to start with. Thoughts?

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/18/24 at 22:29:57 Looking at Ebay, last night, I came upon these, for sale. These are the very baffles, that we got the idea for the rear-firing baffle, from. The guy is pretty sharp, and really seems to know his stuff, but looking at his asking price, I think he is a bit full of himself ::) https://www.ebay.com/itm/166636348544?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D267518%26meid%3D2c6dfbd4c1fc4affb063104cb0e2f228%26pid%3D101959%26rk%3D1%26rkt%3D1%26itm%3D166636348544%26pmt%3D1%26noa%3D1%26pg%3D4375194%26algv%3DRecentlyViewedItemsV2WebWithPbooster%26brand%3DSpeakers&_trksid=p4375194.c101959.m146925&_trkparms=parentrq%3A2d368bb71900ac6a418e78f6ffffbb34%7Cpageci%3A36415c45-2db8-11ef-b5ed-8ef75f1b8c1e%7Ciid%3A1%7Cvlpname%3Avlp_homepage

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/18/24 at 22:41:08 Holy smokes that’s a bit overpriced. That’s not far from my house so maybe I’ll reach out and see if I can hear them. I’ll sell my whole system for $27k. Lol. Two thoughts on the L-pad. I’d rather just use one resistor to keep the parts in the signal path to a minimum. But I’m kind of anal like that. Second, 10db is a lot of cut. Generally speaking 3db is the minimum change we can hear. If you are really close to liking your sound I shoot for changing by 3db. Or to put another way, when mixing in a studio the engineer usually only boosts or attenuates by 3 db. I have to admit I have been snoozing on adding a resistor to mine. I’ve been listening closely and secretly conspiring to implement Steve’s new speaker design.

Title: Re: Open Baffle rear firing tweeter Post by Donnie on 06/18/24 at 23:14:13 I still say just put some felt on the horn. That will knock off the loudness. Even some cut up sponge will work well. No need to make any kind of crossover.

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/18/24 at 23:46:21 C’mon Donnie. That’s too easy. When I get to DIY hi-fi’ing I need to f**k around way more than that. Haha. But seriously, you’re probably right. Enjoying the dialog though.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/19/24 at 00:52:15 I kind of changed horses in mid-stream in this thread. My present setup with the rear-fire tweeter is great. With the talk of resistors and L-pads, I am anticipating my swapping the tops of my baffles (not permanently, but just for variety) and using my too-long ignored, 8” Betsy Alnico’s. They are 92.4db efficient, so a big difference from the 108db tweeters. I’m still a few weeks from having the other baffles ready, so just trying to plan ahead.

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/19/24 at 11:54:21 So far I am liking these more efficient tweeters.  Helped the soundstage and the highs I think.   Made by the same company as the horns.  Harder to mount though.  Not pointing directly backwards.

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/19/24 at 12:15:29 Good morning Tom. What tweeters are you using?

Title: Re: Open Baffle rear firing tweeter Post by Palomino on 06/19/24 at 12:41:16 https://a.co/d/ekFGKba[url]

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/19/24 at 15:14:31 Sorry, I see I missed a few posts over the weekend and my comments about L-pad and attenuation amounts were out of context. I’m really liking the rear firing tweeters in their current configuration with the F-15s. Thanks again for pointing this out.

Title: Re: Open Baffle rear firing tweeter Post by Gilf on 06/19/24 at 23:48:03 I spent not an insignificant amount of time today putzing and listening. Several hours tweaking the tweeters placement, adding and removing resistors, dampening, listening and moving things, and adjusting the W-15 crossover and volume. Then I took the tweeters off. I unscrewed the upper portion of my baffles and put the lower w-15 section in the corners. The upper plate with the F-15s I arranged in Steve’s new impossible speaker design. That led me to the garage and made an adjustable bracket device to dial in the angles, provide upper reflection, and the tried also adding tweeter front facing, and rear facing. Lots of adjusting, listening, switching polarity of the tweeters and subs, more listening, moving, adjusting, listening. When I finished I put my original baffles back together and hefted them back to their place on the blue masking tape on the carpet. No rear firing tweeters. They sound sublime. The best. The best I’ve ever experienced. The imaging. The punch of the bass. The click on the top end of the kick drum or click of the drum stick on the drum skin that is perfectly aligned with the resonance of the drum, the creamy midrange that is like swimming in saltwater, the layers of cymbals like umbrellas all around me, and the sound stage that is so deep it is 15’ beyond the wall.  The best. Sometimes you have to mess around and waste a day to realize how good it has been all along. Oh well, parts back in the parts bin and a smile on my face. Life is good.  [smiley=peanuts21.gif]

Title: Re: Open Baffle rear firing tweeter Post by Geno on 06/20/24 at 03:06:24 What normal folks would call, a waste of a day, audio nuts like us, call, necessary experimentation(or something like that)   With Steve talking about how great the upside down baffles sound, and Hifi Cave, showing videos of same, I’m sure that many open bafflers, have considered trying to do something a like. I know I have. Kudos to you for giving it the old college try - nothing ventured, nothing gained. Glad you ended up a happy camper in the end.

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