Last year I built a pair of Jeff Bagby's auricle speakers, which use a RAAL 70-20XR and single Satori MW16P midwoofers, and now I'm planning to move the drivers to his tower design, called the Testarossa, which is probably known to some here. I'm making this post because I have a few questions and would like to hear the perspectives of other more experienced speaker builders. Being new to this, I'm being conservative and using a proven design, while at the same time reading all I can so I understand what is really going on with the speaker, ie what each crossover component is contributing, how the cabinet design is affecting the sound, etc. I'm a way off from designing my own speaker, and with the dizzying array of proven designs already out there, not sure if I'll ever make that leap to be honest. But the bug has definitely gotten me.
In any case, for those not familiar, the Testarossa is a small tower using the RAAL and two Satoris rather than one. Still a two way. Besides just getting my rocks off building another speaker (and learning), I have two primary reasons for wanting to do this. First is the increase in sensitivity, since I have a 25w amp, and the second is the benefits of two vs one MW, which I think will increase SPL in my smallish room, while liberating the tweeter a bit due to lower resistance values. I think it will sound better, and more full, and take some of the strain off my amp and improve dynamics a bit.
The first question I have centers around which version of the Testarossa I build, the options being a 10" passive radiator (which would be located on the side of the cab), or a ported version, which in my case would be located in the front to lessen boundary issues in my room. It seems the passive version would result in a different response from the MWs, since there is no air exchange, maybe tightening up the response a bit? I'm actually leaning towards the ported version, mostly to save a little $$ but also because I have a decent sub and always will so unless the PR has an obvious advantage I am wondering why I would use it. Jeff did in his own pair, and that counts for a lot in my book, but I don't have the experience to choose like some here.
There are also some details about the cabinets I pan to build that aren't according to the plans, and this is where the experimantation comes in, but maybe that's for another day, but I'll just say it involves mass, which I'm convinced can make a big difference. I come from a world of woodworking and carpentry machines and I've always noticed how much mass just "quiets" things down, and I think a cabinet that's vibrating is causing noise. When you push a piece of stock through a tablesaw, shaper, or planer that weighs a lot there's a smoothness that just can't be had with lighter machines!
Anyway, if anyone has any thoughts it would be helpful, thank you.
In any case, for those not familiar, the Testarossa is a small tower using the RAAL and two Satoris rather than one. Still a two way. Besides just getting my rocks off building another speaker (and learning), I have two primary reasons for wanting to do this. First is the increase in sensitivity, since I have a 25w amp, and the second is the benefits of two vs one MW, which I think will increase SPL in my smallish room, while liberating the tweeter a bit due to lower resistance values. I think it will sound better, and more full, and take some of the strain off my amp and improve dynamics a bit.
The first question I have centers around which version of the Testarossa I build, the options being a 10" passive radiator (which would be located on the side of the cab), or a ported version, which in my case would be located in the front to lessen boundary issues in my room. It seems the passive version would result in a different response from the MWs, since there is no air exchange, maybe tightening up the response a bit? I'm actually leaning towards the ported version, mostly to save a little $$ but also because I have a decent sub and always will so unless the PR has an obvious advantage I am wondering why I would use it. Jeff did in his own pair, and that counts for a lot in my book, but I don't have the experience to choose like some here.
There are also some details about the cabinets I pan to build that aren't according to the plans, and this is where the experimantation comes in, but maybe that's for another day, but I'll just say it involves mass, which I'm convinced can make a big difference. I come from a world of woodworking and carpentry machines and I've always noticed how much mass just "quiets" things down, and I think a cabinet that's vibrating is causing noise. When you push a piece of stock through a tablesaw, shaper, or planer that weighs a lot there's a smoothness that just can't be had with lighter machines!
Anyway, if anyone has any thoughts it would be helpful, thank you.
I'm not familiar with these designs but being Jeff Bagby's I'm sure they were well done. From a theoretical point of view, a passive radiator design is preferable to a conventional bass reflex with a vent. Except for vent location, the passive radiator can be tuned to provide the same response as the vent absent issues of pipe resonance in the vent tube. If using the PR, you can tune the box to a lower response without having those kinds of issues. I suspect that is why Jeff developed the more expensive option using passive radiators. If you use a long enough vent instead to get the same response you might find it causing a dip in the midrange and perhaps even whistling when stimulated at its resonant frequency. That is why vents often face to the rear - to reduce any such audible effects. You shouldn't need more than 9" or so of rear clearance for a vent but you are always better off with a PR
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The Auricles reside in my listening room and are very satisfying. The woofer module developed by Bagby for the Continuum and Kairos works very well in providing greater dynamic reserves and lower frequency response. I have the components for a pair of Testarossas for another room and look forward to comparing them in the near future.
The passive radiator in the Testarossa appears to offer response similar to “large low tune” tuning. The system with the passive radiator is tuned to about 19 Hz and essentially acts like a sealed box above 30 Hz or so with some augmentation to just below 20 Hz. The result is very clean bass for the size of the cabinet and woofers and complements the room response in most domestic listening spaces.
I don't know what "large low tuning " is, but would like to understand this concept. But I understand that not having the vent (air exchange) might add some damping to the drivers? The word I really want to use is "restraint". Maybe this is why it cleans up the bass response? Or is there something about the tuning of the PR that relieves the MWs in the lower frequencies, almost behaving like a low pass? These might sound like silly ideas but I'm trying to understand the technical reasons behind this. In any case from both of the responses to my question it sure sounds like the PR is the recommended way to go.
Maybe this might interest you.
https://www.diyaudio.com/community/threads/raal-70-20xr-and-ptt6-5-compact-tl.356906/
Here is floorstander TL:
Predicted Frequency Response:
https://www.diyaudio.com/community/threads/raal-70-20xr-and-ptt6-5-compact-tl.356906/
Here is floorstander TL:
Predicted Frequency Response:
Wow, if there was a TL design for this driver combo I would be very interested. I think I read somewhere that Jeff was working with someone on a TL, I'll ask Chad at Meniscus if he has the plans, but I'm pretty sure it never saw the light of day. That's a nice looking box though, even as a CAD drawing.
Thanks X, I'm definitely interested, but since that design is for the Purifi drivers, won't the box tuning be off for the Satori MW's I'm using? And also, even if the box would work with the Satori drivers, it seems the existing crossover design for the Testarossas would have to be adjusted, is this right?
The Satori’s and Purifi’s are actually similar in behavior from a TL standpoint. I would have to run a simulation to be sure but I have seen similar behavior.
Thank you. Man, I'm pretty much a newbie so was curious and checked out some of your work. You designed the LSA Warp 1, I guess I should trust what you have to say, impressive stuff.
XRK - I'm really intrigued by the TL design for these drivers, and have spent time the last couple of days reading up on TL theory, trying to understand how it works. Quite a topic, but part of the reason I've gotten involved in the DIY world is that I want to understand as much as possible what I'm doing and why I'm doing it. Being new to a lot of this, of course I have to rely mostly on proven designs (just do it, figure out why later). I'm sure I don't even know all of the questions I should ask, but I do have a couple anyway, if you or anyone would care to chime in.
First, since your TL design was formulated for the Purifi drivers and I'm using Satori, I wonder how the different parameters of each driver (being different) would affect cabinet volume, damping materials application, port size, or any other measurements in the box? Second, would the crossover designed for the Testarossa/Imperial (MTM version) need to be adjusted to rebalance the tweeter/midwoofers? I would think maybe so since it seems from what I've read that efficiency of the woofers in a TL is increased especially lower frequencies.
I'd love to plug and play this whole thing, but I don't know if I'm flirting with chaos here or making more of it than I should. I'd just drop the whole thing but a lot of people seem to think TL is often sonically superior to PR. Again, I don't know if this is always true!
I'm sorry Jeff Bagby is no longer with us, before I knew he had passed I was becoming a big fan of his work, and also that of Rick Craig. It would have been great to throw this idea at Jeff and hear his response.......
First, since your TL design was formulated for the Purifi drivers and I'm using Satori, I wonder how the different parameters of each driver (being different) would affect cabinet volume, damping materials application, port size, or any other measurements in the box? Second, would the crossover designed for the Testarossa/Imperial (MTM version) need to be adjusted to rebalance the tweeter/midwoofers? I would think maybe so since it seems from what I've read that efficiency of the woofers in a TL is increased especially lower frequencies.
I'd love to plug and play this whole thing, but I don't know if I'm flirting with chaos here or making more of it than I should. I'd just drop the whole thing but a lot of people seem to think TL is often sonically superior to PR. Again, I don't know if this is always true!
I'm sorry Jeff Bagby is no longer with us, before I knew he had passed I was becoming a big fan of his work, and also that of Rick Craig. It would have been great to throw this idea at Jeff and hear his response.......
Looking at the critical TS parameters that matter for the 8ohm Satori 6in and PTT6.5 everything is close with regards to Fs (about 30Hz), Qts (about 0.3), but Vas is 28L for PTT vs 48L for Satori. Satori will require a larger cabinet to reach the same bass extension. Without simulating it (and I would but my computer’s virtual machine needs to be re-installed to use Akabak), I would say that it will require tweaks to make a new custom TL design. Probably a floorstander is needed if you want dual drivers. If you have a Bagby Testatossa crossover already you must keep it as a TMM with same driver spacing. For drivers this expensive, it makes sense to do comprehensive simulation from scratch. We want to get it right.
Thanks for that - that looks like a pretty big difference in the Vas from what I can understand of the concept, though I have no idea how that would translate to cab volume, but bigger than your TL design seems like a lot of box, substantially larger than the 8.5"x13"x39" Testarossa cab. Maybe it's best to play it safe with this one and build the PR version and keep myself out of the weeds, but now I'm pretty intrigued by the TL concept and interested in pursuing it down the road. Thank you very much for taking the time to look into this, and for your explanations.