Cool
I spent Sunday AM rehearsing and then playing a vocal solo with piano accompaniment. Wood piano, a Baldwin 44" console. Only the 3rd time I've done this, as my voice is very soft. Started trying 3 weeks ago. You can learn new tricks in your seventies.
Thanks to a buddy who devised a lapel mike stand that points the cardioid lobe of the mike at my mouth from 4" away. Tried mike clipped to my lapel 3 weeks ago, PA system picked up mostly piano and not much vocal. TV personalities are not playing a 110 db instrument as they talk into a lapel mike. PIano is loud enough for 40 person hall without amp, but I am not. First week I sang+played I clipped the mike to the candlelighter wand and the lay leader held it in front of my mouth foam ball end towards me.
Can't get more real than a breathing musician + a wood and steel instrument.
On distinct source stereo & panning the locations on the master track. I can't really tell where the instruments are on stage from the back of the hall when I'm at a live Louisville orchestra concert outdoors. Yes, I can tell from aisle 1 hard right, which is the other cheap seat I can afford. The instruments I can't hear very well are on the left. Fortunately the violins are on the left in an orchestra, which is my least favorite instrument.
Well here's where I'm at. After reading everything I could find regarding damping factor and internal impedance, I learned a ton. I am ordering a vintage Simpson VOm and have an 8ohm resistor on the way from Mouser, nice metal chassis wirewound Vishay, will be able to use it many times. I'm curious to know what the impedance is in both of my tube amps, and thanks to indianajo who gave me the "for dummies" tutorial.
In the meantime, I'm going ahead ordering the drivers and building a test cab from some 3/4" Advantech suubfloor, picked it up on a lumber run the other day. I'm just going to take my chances and measure as I go and see how things line up, and how they sound.
As far as using a 15" in a small room, there's enough people who love this crazy setup I just have to go for it. The thing I haven't mentioned is within a year my setup will be in a much bigger space, so I'm looking ahead too.
I'm going to use the Beyma 15CXA400ND, a super nice looking driver that meets the criteria, with 98db sensitivity and an 87g Mms, pretty light.
I'm tuning just barely above Fs (40hz) to 44hz, in a 142L enclosure, with 2-4" vents at 96mm if I remember correctly. I can model this driver in an even bigger box (Vas is 196L) and still stay pretty darned flat to the rolloff but I'm being a bit conservative and not pushing it too far. I also like the size, beefy but just about as big as I can deal with in this room. Test enclosure will be 18" x 41.5" x 15.5" with a 36mm baffle. The baffle width is a primary concern.
I'll test it on both amps, and if I just can't make it work with the 45, I may just move on from fleawatts, although I'd probably build or buy a bigger SET. I know trying to make a speaker work with a <2wpc amp is a real challenge, and it usually involves large enclosures and bigger rooms. IF the 45 fails, these speakers will work great with other amps, even if I need to do some xover adjustments.
Group delay looks great, and so does excursion down to 22hz. I know this won't be perfect, but it migh be darned good, and I just have to make some choices and get moving. Here's a shot of the alignment, thanks to everyone for all the responses so far, I've been listening and if there's something off here it's not from obstinance but ignorance:
In the meantime, I'm going ahead ordering the drivers and building a test cab from some 3/4" Advantech suubfloor, picked it up on a lumber run the other day. I'm just going to take my chances and measure as I go and see how things line up, and how they sound.
As far as using a 15" in a small room, there's enough people who love this crazy setup I just have to go for it. The thing I haven't mentioned is within a year my setup will be in a much bigger space, so I'm looking ahead too.
I'm going to use the Beyma 15CXA400ND, a super nice looking driver that meets the criteria, with 98db sensitivity and an 87g Mms, pretty light.
I'm tuning just barely above Fs (40hz) to 44hz, in a 142L enclosure, with 2-4" vents at 96mm if I remember correctly. I can model this driver in an even bigger box (Vas is 196L) and still stay pretty darned flat to the rolloff but I'm being a bit conservative and not pushing it too far. I also like the size, beefy but just about as big as I can deal with in this room. Test enclosure will be 18" x 41.5" x 15.5" with a 36mm baffle. The baffle width is a primary concern.
I'll test it on both amps, and if I just can't make it work with the 45, I may just move on from fleawatts, although I'd probably build or buy a bigger SET. I know trying to make a speaker work with a <2wpc amp is a real challenge, and it usually involves large enclosures and bigger rooms. IF the 45 fails, these speakers will work great with other amps, even if I need to do some xover adjustments.
Group delay looks great, and so does excursion down to 22hz. I know this won't be perfect, but it migh be darned good, and I just have to make some choices and get moving. Here's a shot of the alignment, thanks to everyone for all the responses so far, I've been listening and if there's something off here it's not from obstinance but ignorance:
I think you are on the right path with large high efficiency speakers and a nice SET amp.
I am using a headphone amp with 332 milliwatts per channel to drive my speakers with 12" guitar drivers and a super tweeter. At 100 db/watt, they are plenty loud enough for me and sound very nice. It can be done!
I am using a headphone amp with 332 milliwatts per channel to drive my speakers with 12" guitar drivers and a super tweeter. At 100 db/watt, they are plenty loud enough for me and sound very nice. It can be done!
Hmm, the pioneer's 136.11 L/40 Hz Fb, T/S max flat's 134.61 L/44.8 Hz Fb makes yours about spot on if you didn't account for the driver, vents, bracing losses 😉; regardless, within the ~ +/- 10% rule of thumb (ROT) when factory specs are used for typical high DF amps.
Factoring in amp damping though may make them a bit too under-damped, yet many like them anyway as it provides a boosted (mid) bass that offsets baffle step loss in many apps, though again, it will be interesting to 'hear' how well ya'll like its low end response with other than actual Fs tuning.
Factoring in amp damping though may make them a bit too under-damped, yet many like them anyway as it provides a boosted (mid) bass that offsets baffle step loss in many apps, though again, it will be interesting to 'hear' how well ya'll like its low end response with other than actual Fs tuning.
Thanks GM, I was hoping you'd chime in here. Do you think it would be better to tune to FS (40hz)? Easy enough to do as I'm not too far off. I'm not completely clear on the principle of why tuning to Fs is advantageous, not doubting you at all, just don't quite understand except it seems like it would cause a bit less impedance issues?
Here's how that models in a slightly bigger box, I really can't go much larger then this, though the driver seems like it could very comfortably approach its Vas of 196L
Makes me think of this build (not mine). Vortex 15's as desktop monitors:
https://imgur.io/a/YrzUkIL
https://imgur.io/a/YrzUkIL
You're welcome!
Well, history shows that the lower the DF, the greater the need as it increasingly tracks the impedance, which of course can be quite a different response compared to a typical sim and even one with using a resistor in the sim; regardless, with all but low DF SETs, which I did traditional reflex vent/tuning of actual Fs, i.e. when the impedance peaks were at equal amplitude on a scope, so you can get a more accurate sim matching them up, otherwise used pipe vents I mostly tuned in room at the desired locations by using cardboard tubes of differing lengths to slide in most of the way with a thick rubber band to act as a temp seal and FWIW, virtually all 'stereo' pairs not hard in corners were tuned differently, sometimes pretty far off due to room acoustics.
Well, history shows that the lower the DF, the greater the need as it increasingly tracks the impedance, which of course can be quite a different response compared to a typical sim and even one with using a resistor in the sim; regardless, with all but low DF SETs, which I did traditional reflex vent/tuning of actual Fs, i.e. when the impedance peaks were at equal amplitude on a scope, so you can get a more accurate sim matching them up, otherwise used pipe vents I mostly tuned in room at the desired locations by using cardboard tubes of differing lengths to slide in most of the way with a thick rubber band to act as a temp seal and FWIW, virtually all 'stereo' pairs not hard in corners were tuned differently, sometimes pretty far off due to room acoustics.
Thanks GM once again. I'm confused by your wording in this sentence: "with all but low DF SETs, which I did traditional reflex vent/tuning of actual Fs"
I'm very literal so excuse me, but that reads as "all except low DF SETs", and I'm pretty confident I'm dealing with DF of <2 here, which is pretty low, so would you tune this to Fs, 40hz?
I'm starting to understand why the response tracks impedance, it's kinda like the amp has a weak immune system haha!
If I need to tune to Fs, it's going to be a big box! But I'm working on how to make it work, maybe by increasing the height a bit and the depth a bit.
By the time I compensate for the bracing and driver volumes this will not be easy to ignore, so I'm going to have to make them pretty.
I'm very literal so excuse me, but that reads as "all except low DF SETs", and I'm pretty confident I'm dealing with DF of <2 here, which is pretty low, so would you tune this to Fs, 40hz?
I'm starting to understand why the response tracks impedance, it's kinda like the amp has a weak immune system haha!
If I need to tune to Fs, it's going to be a big box! But I'm working on how to make it work, maybe by increasing the height a bit and the depth a bit.
By the time I compensate for the bracing and driver volumes this will not be easy to ignore, so I'm going to have to make them pretty.
Right, for low DF tubes I used the pioneer's way to tune a reflex, pgs 228-231/book pgs 216 - 219 that includes a description of my beloved 'click' test. Note that nowadays it can be done to mind numbing accuracy using an impulse response test.
Wow GM thanks for taking the time to pot those links, I'm going to read the entire book, it's well written and things are very well explained. The click test is awesome! The only thing I wonder is how to create the resistance of the added cloth over the port in another way.
I see the old school alignment is Fs + Vas for enclosure volume, but I'm not going to be able to get very close to the 196L Vas of this driver, but it sims really well from 140-164L, so I'm keeping it smaller but as large as I can.
I see the old school alignment is Fs + Vas for enclosure volume, but I'm not going to be able to get very close to the 196L Vas of this driver, but it sims really well from 140-164L, so I'm keeping it smaller but as large as I can.
The British came up with the ARU, a piece together vent, so of course you can use screen door or pet screen to 'sandwich' whatever material you choose or just layers of the screen not quite lined up as I did. Stapled in place, then make a (cosmetic) ring/frame if you can't find something suitable pre made. Personally made a sub baffle for the vent, tuning it wrong side out and flipping it over once done.
If you look carefully you can just barely see the rectangular slot in the bottom baffle with the screen behind.
If you look carefully you can just barely see the rectangular slot in the bottom baffle with the screen behind.
Attachments
Forgot to note that you can do this with pipe vents also if OK with small fractions of a tuning error due to the normally slight box Vb being a little larger, though of course with large and/or long pipes, shelf vents it's a bit more time consuming if not temporarily adding some scrap/whatever to offset it, just don't forget to remove it! 
I'd be trying to lower that x-over frequency to below 800 hz if you don't want narrowing of the frequencies just below 1.5khz. you will have a beaming effect even at 1.5Khz - I think its around 3db rise at that point.
I have some Fostex RM685, built with a printed ribbon tweeter that they had patented back 30 yrs ago that were known to blow. there are some good Chinese's knock off that will fit into the center of the Fostex. The Fostex had a 2" voice coil and the time alignment is about .25" off between the voice coils. I'm planning to x-cross them over around 3khz. The moving piston size is around 5", small enough to keep the beaming effect under 2db's.
The unfortunate issue with the fostex tweeters are they can only handle about 15 watts, and with passive x-overs, any clipping of the amp will fry the tweeters. But the woofers are top rate, very low 2nd and 3rd harmonic distortion. These are pro rated nearfields especially designed to mix voice tracks in recording and broadcast duties. unfortunately they didn't sell as well as they should. Neither did their RP line of mics which are all excellent - having the sound of large diaphragm mics with the robustness of dynamics. So with these new knockoff tweeters I'm hoping to give them a new life.
As far as curvilinear speakers, not sure what you mean except most speakers I've worked with are not straight cones but "curvilinear' they have a 3D curved surface.
JBL x-crosses their 12" on their studio monitors at 800 hz with their excellent horn taking the rest of the spectrum. And they have a very nice polar response. The other problem at crossing that high in a 12" is chances are the cone will have breakup node around that region, if its a paper cone, while polys will have lower efficiencies, harder to match with passive x-overs. Anyway these are my thoughts. and yes you will need a digital x-over to time alignment. I use an old Yamaha DME 32, which was use for sound reinforcement. I bought mine at a surplus store for $100. it great to fine tune x-over points as well as time alignments, where you can do it on the fly. It will do 24db/octave Linkwitz-Riley filter topology as well.
That why I had to mention about lowering the x-over points with such a large driver. You can hear it.
Thanks stealthy, some good stuff there.
Beyma suggests 1.8k xover point for the 15cxa400nd! FR of the tweeter is 800-20k. I don't want to go all the way to 800 but I was going to see how it looks at 900. This compression driver is supposed to be excellent and at less than concert volume it should be fine if all the specs line up and it measures ok.
Don't know what you mean about all the curvilinear stuff, I don't recall saying anything about that and understand most drivers are parabolic or curved in section. Maybe it was someone else who commented about that? Oh I see you're responding to mayhem there.
I'm going straight old school (these days) passive with the xover. I'm still waiting for the drivers, so have plenty of measuring and T/S checking to do before I even start the design of the xover, but once I know I've got the box right at least the first iteration shouldn't take long to figure out. I'll keep an eye on the beaming, it's not something I would usually think about due to inexperience. Hopefully crossing below 1k will help in a lot of ways, I really don't want the 15" paper cone trying to reach up that far (1.8k).
Beyma suggests 1.8k xover point for the 15cxa400nd! FR of the tweeter is 800-20k. I don't want to go all the way to 800 but I was going to see how it looks at 900. This compression driver is supposed to be excellent and at less than concert volume it should be fine if all the specs line up and it measures ok.
Don't know what you mean about all the curvilinear stuff, I don't recall saying anything about that and understand most drivers are parabolic or curved in section. Maybe it was someone else who commented about that? Oh I see you're responding to mayhem there.
I'm going straight old school (these days) passive with the xover. I'm still waiting for the drivers, so have plenty of measuring and T/S checking to do before I even start the design of the xover, but once I know I've got the box right at least the first iteration shouldn't take long to figure out. I'll keep an eye on the beaming, it's not something I would usually think about due to inexperience. Hopefully crossing below 1k will help in a lot of ways, I really don't want the 15" paper cone trying to reach up that far (1.8k).
Not parabolic (bowl shape), but either conical (slab sided, AKA deep cone) or curvilinear (expo flare, AKA shallow cone, pretty much all wide range drivers), though Altec proved there's precious little difference between the two WRT where they 'launch' the frequencies (Scroll down to the 15").
Another good read GM, but equally interesting was the article by Paul Klipsch about autoformers vs L-pads. I'm considering using autoformers in these speakers. I wonder if Klipsch still uses them in production, or ever did, cost being a factor.
Not that I'm aware of, but best to check with the Klipsch forum. Altec used them into at least the late '50s, then switched, but left the mounting holes to retrofit their 15067 if desired. Don't know about EV, RCA, etc. other than TTBOMK everybody that wanted to do prosound used them early on.
Well, while I wait for the drivers, I've built my test cab, I'll do the cutouts when the drivers arrive, and drill the port holes out at 4 1/8" so I can easily slide different test lengths in from the outside and do GMs trick of using some rubber bands or my favorite, electrician's duct seal to hold them in place. The box is 5.5 ft^3, the extra .5 being the equivalent volume of the ports, bracing, and drivers. I'm tuning to 44 hz, a nice flat alignment at least in WinISD. Power handling looks great, group delay is excellent, etc. Just got the Simpson meter (thanks indianajo) so will check the amp impedance as soon as I have the time, doing a kitchen remodel rt now with a designer on my back so I don't have a lot of bandwidth for tech work at night (ah to be 40 again, even 50 haha). Maybe someday I'll come into the clams to buy a pair of 604s but for now this is a worthy adventure I think
Thanks to everyone for your input and help so far, I hope these drivers test close to the published specs, but I have a bit of work ahead either way, back and forth getting the tuning/crossovers/damping all worked out.
Thanks to everyone for your input and help so far, I hope these drivers test close to the published specs, but I have a bit of work ahead either way, back and forth getting the tuning/crossovers/damping all worked out.
Interesting! The various duct seals I have/used leaves a bit of residue that ruins a finish applied over it other than enamels or denser, so curious what they use nowadays to claim non-staining.
Well you were tuning finished speakers in-field, this is just for a test box so it's not an issue.
What IS and issue though is that the Beyma 15CX400Nd are still on the bench in Spain, and won't be here until December sometime. So I'm faced with the choice of waiting, or trying the 15CXA400Fe, its ferrite sibling. It models like a beast, and according to WinISD can go all the way to Vas at 190L tuned to Fs, 40hz or even a bit below Fs, which I'm afraid of. I know this is the old school kind of alignment, but unfortunately I can't build a box that big for my space, so I'm limited to 142L net, about 155L finished. Has a mild hump but still looks OK to me. I just don't know how different the sound is going to be from the ferrite as opposed to the neo magnets, which are supposed to have a better grip and acceleration I guess. Anybody have a 2 cents on this?