A smaller Lancelot speaker: underlying concepts, its sound, current production driver option
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- Опубліковано 8 лют 2025
- In this video I show you my latest creation, share what concepts went into this active enclosure, what it sound like compared to a larger cabinet, how it reduces audible forms of distortion and increases speaker efficiency. I also present some modern driver options..
Enclosure Specs:
ML-TQWT rear-loaded horn, tuned to 27-28 Hz (aperiodic was tried too)
168L net volume
2x Altec 414C woofers
1x Electrovoice DH1A compression driver
1st order crossover with zobel network and EQ for DH1A drop over 3kHz
buymeacoffee.c...
You clearly remind me myself in my teen years and all my ideas before I started to study physics and electronics on university.
Thank you for your magnificent comments that are a real help to the audio community.
Since you seem a bit blinded by your academic schooling, what I did here is check out the sonics of a Q=0.57 alignment, coming down from the old pioneers alignment of Vas/1.44 and Fs=Fb. This is also an experiment to get to grips with the subjective magnitude of cone interference - checking the old pragmatically derived patterns Altec derived from 1000s of installations - and study its effect while changing the crossover frequency.
Interesting about harmonic distortion and "masking profiles." Also makes sense that delayed distortion would stand out.
Minimal crossovers make sense to me also because of phase coherence
I didn't realize a bottom port added that much boost but seems well worthwhile because of the amount of power low notes take. My Zu speakers have bottom ports probably for the same reason. Did you use software to design the enclosure?
Really good video
Janos has an excellent instructive video which is called 'VOTT vs VOL' which shows how the 'VOL' reaches its efficiency though horns, port placement, active cabinet and room modes.
Yes, I did use a program, 'AJHorn', which is quite a bit more user-friendly than 'Hornresp' and is good enough to find good port and driver locations for a range of enclosure styles. Both programs unfortunately use Webster's horn theory which from my research doesn't survive empirical scrutiny but it's a lot better than trial and error :)
If you google 'Auditory Perception of Nonlinear Distortion' by Dr. Geddes and Lee, you'll find some good information on what is audible and what is not. This relates extremely well to the characteristic of our hearing (non-linear, high harmonic distortion, phase and time delay sensitive over 500Hz).
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I didn't realize a bottom port added that much boost" well, this is probaly not true, because low frequency means long wavelength and compared with this length (50Hz about 7m/21feet, lower frequencies even longer [34Hz/10m/34feet]) the position of the port nearly does not matter. Many misconceptions out there about physics ... unfortunately.
@@ahnenpost5237 You are arguing that a speaker (woofer) positioned exactly between floor and ceiling creates the same level of bass as one positioned on the floor? Because frequencies are so long?
Just lift a speaker and see what happens!
But lets dive into two physics aspect that give a floor port more boost than sims predict: first, we must consider the efficiency with which the air in the bass port can couple to the air in the room - by coupling that energy to the floor, a huge surface compared to the port exit, will help that efficiency. Second, the presence of a floor will limit the rate of expansion of the compressed airwaves radiating out, resulting in less attenuation.
It's not all that much different from a guitar... the strings make the noise, but have poor coupling to the air. A 15" driver only has 850cm2 surface a freakin minute part that isn't even properly capable of generating a 50Hz wavelength (0.1% efficient, maybe??? with lots of help of an enclosure).... the port size is even less. If you want to improve those size of soundwaves significantly we want large surfaces... simple physics mate.
@@EduardBroekman I argued what I argued. You turned it into something different and then you miss the point.
@@ahnenpost5237 I could have been more clear. I didn't realize a bottom port added that much boost when it's close to the floor. My understanding is the port location on the enclosure has a much smaller effect than the ports distance to room boundaries
the efficiency of a compression driver is measured always with a horn applied - so you cannot say, that the effiency is 110 - it will be much less, about 100, may be 103, but minimum 6dB depending on the horn used for measurement (directivity matters! without a horn applied, no directivity translates into much less efficiency).
Good point in general, yes it's nearly always horn mounted for 'sensitivity' measurements but what will I use your new lower number of (110-10=100db/W sensitivity for?? It seems useless to me unless we're want to calculate the efficiency percentage? Is that the goal? If so correct, but pragmatically we don't need this -7db to -10dB correction, it has no purpose.
Efficiency, properly, is a percentage on which a horn has no influence. The best CDs have reached 30% electrical efficiency = 107db/W/1m sensitivity, so in half space without losses that would be 113db/W/m. I'm guessing your 7-10dB/W correction is based on the directivity of CDs w horn vs full space? Seems reasonable.
So, my problem with your statement is that you want to compensate for directivity because a horn is mounted, but woofers also have directivity, are generally operated on a baffle - and you're not reducing sensitivity for those. So why this uneven treatment? If we're interested in building speaker, which IS the topic of this video!!!!, I argue we can use the sensitivity numbers - within reason and if the manufacturer don't cheat too much ... as I will try to show below, these uncorrected numbers work out well.
So, my point is that when we're comparing to other driver types, such as woofers, we have the same half space + directivity of that woofer as well. All drivers have higher measured sensitivity due to their directivity!!! With that in mind and I have found this pragmatically, we actually CAN quite decently compare the given 'sensitivity' as db/W @ 1m between woofers and compression drivers.
As a more specific example of actual sensitivity, I just bought the SB Audience Rosso 65CDNT (112dB/W/m, 1.9T field strength - a better indicator of efficiency). This upfiring CD I had to attenuate 18 dB to match them to a 99dB/W/m woofer. So based on that and the very indicative 1.9T field strength, I guess that the actual efficiency of this unit sits at around 20% = 105db/W but then it would measure higher in free air / half space +6db? due its own directivity (no horn needed) minus some losses. That brings us very near to the listed 112db/W/1m when mounted on their 50 by 70 degrees exit H280 horn that they use for measuring sensitivity.
Now, if I had followed your compensation, this CD would be 112-10=102db/W/1m without horn (as I run it), and this unit's wouldn't that much louder than my 99dB woofers, the efficiency would be 10% (low for 1.9T) What I see in reality, is that without horn, this unit is far louder than the woofers and it had to be attenuated a lot despite the CD being point at the ceiling... so for the intent of mating to the woofer, considering this a 110db/W sensitivity driver worked out very well....
@@EduardBroekman same here, you missed the point. If the goal is to match the Wooofers sound pressure withe the compression driver, the output of the tweeter matters, that is lower without horn, and this fact has to be adressed in the crossover-design. It's thus simple. The end.
@@ahnenpost5237 I get your matching, which is obvious - is that your only point?
Now, technically what you say there is wrong: the total energy output doesn't change with a horn, the only thing a horn does is control directivity, add some diaphragm control plus add distortion. A horn never increases efficiency or output of the driver itself.
For an omni directional speaker where on-axis response has no meaning, we match the overall energy output of the compression driver with the overall output of the woofer. This is likely very different from speakers where the listener is expected in a specific 'sweet' spot.
Any points we're still missing here??
@@EduardBroekmanSome people just want to argue it seems. Pointless.
You are doing a hell of a job with your system and I really want to build a active cabinet. I just bought two Beyma 12 lx60v2, 16 ohm drivers.
Couldn't resist since I got them for half the price, new. They should be quite similar sounding to JBL 2206.
Or perhaps I build a bass guitar cabinet with them. I have always wondering how a active bass cab should work out. I have to build one and find out I guess.
Since I already planned to build cabinets for the JBL 2226, 15" and 16 ohm. I have positive thoughts on driving them with a tube amp. They are quite an easy load and don't need so much power to sound loud enough.
I am an beginner at tube amp building, but have some experience with cabinets. But I have to start building to learn and I don't cut corners in what I do. All or nothing approach.
An darling amp maybe would be good to start with? The 1,4 watt version with Hashimoto transformers looks like an affordable and easy build.
Have you some ideas on a 10-20 w Class A tube amp that sounds good? A diy design. I am sold on tubes and have heard the early Ocellia Kedros silver with a 12". Soo good, it really filled out the whole house and after that experience I can't look back on dead cabinets.
/Gabriel
@@gabrielnilsson5398 Hey Gabriel. Nice to hear from you again.
For an active speaker, even with the 12" Beyma, I'd build one in the style like Janos' 'La Grande' - look on his Real World Audio channels for that. The actual box size / port tuning does depend on the size of your room, what walls you have, how much the speakers will be out from the wall, and even the kind of amp you plan to use with it... basically we'll try to equalise the room (bass) response into the design, so it ends up near flat or a with a little bass lift when in your room and you'll get more bass extension.
The Beyma's high-ish Fs and low Vas means that the box will be small and you can keep the enclosure back wall close enough so standing waves don't form (1/4 wave length of box depth < crossover frequency). On the negative due to its Fs and performance orientation, it won't reach that low. In my room I'd probably start with Fb=35Hz and Vb=Vas=48L bass reflex box as here in my room that would be flat and the port can be narrowed to lift the bass/higher tuning if needed.
Now, for a tube amp in the 10-20W range, I'd go with a 2-stage 300B.. A plethora of designs out there.. look for the ones that operate around 65mA 350V, they've generally been created with sound quality in mind; the ones that are maximising power and can reach up 16W will run the 300B much hotter.
A darling amp is nice but it's low power may annoy you. Something like a 2-stage 2A3, which is much easier to drive than a 300B, opens up a lot more driver tubes, and can be build quite cheaply for the same goals as a Darling, plus getting quality output transformer is much more likely to work out (the low plate resistance doesn't need a massive transformer core, or much windings). A good 10K OPT for the darling is much hard to find than a quality 3.5K or 5K OPT for the 2A3. I just bought the Hashimoto H20-10, which I can use as 5K, 7K, 10K or 14K and it's an impressive OPT, but it's not cheap. I'd buy a different model for the 300B or 2A3.
I apologize if I missed it, but is it your intention to go to a stereo set-up with two speakers at some point ?
Regardless I enjoy your videos and the content
Hi there, thank you and who knows; that might happen some day but it's not a goal right now. I'll answer you a bit more extensively in a video.
Hi just curious why don't you run the top 12in fullrange with the crossover set at 1200hz and the bottom at 200hz low pass on down so both 12in play 200hz down for more slam but 200hz on up with one 12in with the crossover for less comb filtering and beaming and build something like the Wharfedale SFB/3
@@MyTgangsta Yes good thinking and such a 2.5way option did cross my mind and I will trial that once I receive the new compression driver next week. That CD will hopefully allow a nice low crossover point (under 800Hz at minimum) which will reduce combing effects and make the speaker more omni. There's also the baffle step which needs to get solved by the crossover point choice for the 3 drivers.
Hey I'm curious on one thing you compared the new compression driver that you're getting as a alternative to the altec how did you get to that conclusion because I like the old altec and jbl speakers and compression drivers and since they're expensive and we do need alternatives just wondering how you came to your decision on your new compression driver based on the altec
@@MyTgangsta I mostly looked for an option that (1) would be easy to integrate / flat response (2) similar extension at both ends as Altec 288 (3) gets positive subjective reviews (4) is more affordable and available than the Altec 288, also for those in Europe. The new productions options I've come across this far are the Radian 950 and SB Acoustics 65 CDN-T, with the latter being very affordable and hence worth a try - and it's sounding good (it arrived yesterday). Hope that answers your question and yes there's other Altec and JBLs compression drivers that would do very fine, I hope the snag one in the future...
What do you think about the B&C DCM50 16ohm? It has a paper diaphragm with the downside, that it only goes to 10k.
Since you are using it off axis, that should not really matter.
Are you planning to print the large rear covers for the sb for more low range extension?
Hi Nils. That B&C driver impedance graph indicates a lot of break up modes in the 5-9kHz region and it seems to show up in the freq.response graph, and together with the limited range that driver doesn't appeal to me. Are there positive reports from people who've build with it and which freq. range did they use of it?
I''m not sure what you mean by printing rear covers for the SB? I did install the SB driver on Friday and it needs a little bit more work than just a crossover network, but it has been promising so far.
@@EduardBroekman All the graphs look really smooth on the b&c.
Crowe talked about it in the video:
ES-450 Biradial No.2143
@@EduardBroekman 3D CAD File --- Rear Cover No.2376 for SB Audience 65CDN-T
@@EduardBroekman If i recall correcly crowe liked the sb more with a little zobel at the peak arount 8k. Maybe you could ask what values he used.
@@Nils31199 Thank you for mentioning it, that 65CDNT driver sometimes has an edge to it so it's interesting he states this cleans up the 500-1000Hz and lowers Fs (Note Crowe mentioned preferring a tube amp for the 65CDN-T..hint?!). Worth a try that backcover!
I missed his review on the DCM50 which is even more unequivocally positive than the 65 CDN-T.! One notable thing in that DCM50 review is that Crowe here reduced the waterfall graphs for the DCM50 to -25dB while others are on -30dB... regardless, thank you so much for sharing as it's interesting to have a large non-titanium diaphragm reviewed. It's quite a bit more expensive, but would be very interesting to hear. One of my listening notes is that the EV DH1A never sounds metallic or like titanium, but the 65CDNT does at times.
Btw my comment was on what the impedance curves show that are on the B&C datasheet for the 8 ohm model... it usually indicates break up modes, and having them down in the 5-9kHz is not a nice prospect; but it seems the reality of listening (for the 16ohm model?) is different.