Hi, I have read through most the forums.  I would like to first thank you for putting out charts and graphs on your competitors subs and yours. I have personal heard and tested a friends bass boss ssp118 vs the ls801p, I have found the ssp118 is far superior to the ls801p when below 60hz (where it matters).

I had the rare chance to test a bass boss ssp118 next to an rcf8006.i know someone on the fourm was asking about that comparison and I want them to know that in my testing using sine waves and a spl meter pushing the cabs to their spl limits the single 18 ssp118 outperforms the double 18 rcf8006 cab by a few db below 45hz. I think the rcf woofer/box combo has more in it if the limiters could be opened up, but it seemed to me the rcf limiters are set to clamp very early, Or the amp has far less power than the bass boss amp. So that’s a win for the bass boss in my book. And the ssp118 would crush the rcf8004 based on this info.

I have really enjoyed playing with and testing your subs and I think your power amp and limiting is giving a real world edge on the other big dollar cabs. In my opinion you have without a doubt the best single 18 reflex box on the market.

now on to my personal question. I have seen the ssp118 outperform many big dollar cabs first hand. But I don’t run those cabs, I’m a little different. I run a pair of subs I built myself.  There similar to a ls1208 but with added bracing, thicker wood, and  b and c tbx100 woofers. The design can be found on b and c’s website (suggested designs)( s18hn). They produce 105db 1w1m at 44hz. I run them center stage off a pair of bridged 3102plx qsc amps.(2000rms @ 8 ohm each) But when I couple 2 cabs something strange happens.

When I couple center stage outdoors I get this phantom 11db boost at 40hz. Why am I getting more then the 6db everyone speaks off? I just wish I knew where that free 5+db comes from cause it is giving my rig an unfair advantage that I can’t explain. If I wanted to replace these 2 subs I would need some serious muscle because of this free 5db What in the world is going on here? Are there any bassboss subs that will gain more than 6db when coupled? also I only see this 11db gain outdoors, indoors In smaller clubs i see the normal 6 usually. I am so lost 

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David Lee
Thank you for your kind words and high praise! We do believe we build some of the best products on the market, regardless of price, and are constantly working to improve the performance and value we deliver. I also agree that our amplifiers, limiters and programming are the deciding factor in that performance and value. They deliver prodigious power in order to realize the full potential of the speakers, which, as you noted, is where others fall short. That power, in combination with nuanced control to keep the speakers safe and working no matter what you ask of them, is at the heart of my design philosophy.

Now, to your personal question. I looked up the horn you mentioned and drew a quick 3D model from the drawings. I took the data from the drawing and simulated the box with both the 18TBX100 and 18NW100 drivers. The horn appears to have a flare constant of about 25Hz and a length of about 2m, which is a quarter-wave length of ~42Hz. My simulation looks very similar to the response graph provided by B&C, however I see about 5dB less sensitivity than they indicate. Perhaps they were measuring with 2 boxes? Have you verified the sensitivity yourself or is the 105dB @ 1w1m data from B&C’s sheet?  

I then simulated doubling the boxes, at which point my simulations looked almost identical to the B&C measurements. I didn’t see any indication of the “free” 5dB in this data. It appears to exhibit the expected 6dB increase in output when a second cabinet is added, with a little extra benefit that fills in the trough in the response between 50 and 60Hz. This little extra appears to be on the order of 2dB, but not 5.

Simulations can’t take everything into account, so we can look for clues in the theory. The low frequency performance of a horn is limited by three factors, its length, its flare constant and the total radiating area of the mouth. When you bring two horns together, the only one of the three that changes is the total radiating area. The flare constant and the horn length remain the same.

If the flare constant and the length of the horn can support performance at frequencies lower than the limit of the radiating area, when you bring two of them together, the radiating area is doubled, and the combination can provide an improvement in performance at the lower end of their operating range that is greater than the simple summing of the outputs of two sources. The smaller the radiating area is relative to the flare constant and horn length, the bigger the improvement that adding more boxes will provide.

In the case of your horns, the radiating area appears to be a factor of .19 of the flare constant, or about 20% of the ideal radiating area. That would seem to indicate that you could get amazing improvements if you coupled 5 boxes and had 100% of the ideal radiating area. In reality, the flare constant of those horns is very low compared to their length, so it’s likely there would be little benefit realized in low frequency performance beyond 2 or 3 boxes.

What you may be experiencing is the result of the increased directivity of the two boxes because the two boxes side-by-side are very nearly the same width as the length of the horn, which means you will start to see increased directivity down into the 40Hz range. If your extra 5dB is realized on the floor directly in front of the two horizontally side-by-side cabinets, it may be due to the horn length, the radiating area and the large acoustical source dimension all falling at very nearly the same frequency.

You asked what boxes we make that might provide more than 6dB when they are coupled? Having designed and manufactured horns for years, I totally understand their appeal, especially for massive impact, but I was frustrated by the absence of the deep-bass performance that I wanted from my subwoofer designs. I started to compare the advantages and disadvantages of several styles of subs to better inform my design decisions.

Horns are very efficient at converting electrical energy into acoustical energy, but for a horn to deliver that efficiency at the very low frequencies I demanded, it would have to be enormous! At the very least, several would be required, and not every gig can accommodate 4 large horns in order to get the desired frequency response, nor do any mobile operators want to have to lug that amount of gear around to do a gig. In other words, sometimes you just don’t benefit from the kind of efficiency that horns provide.

There are other types of efficiency. What some might see as the low-bass “benefit” of bringing two horns together could also be looked at as a large and expensive compensation for the low-frequency shortcomings of small horns.  To me it’s about what works “where it counts”, as you said, and horns have to be extremely large, and in plentiful quantity, to perform in the lower frequencies around 30Hz.

To take advantage of the efficiencies and "punch" of horns while still providing the deep bass that underpins our designs, I created the VS21 Powered Sub, a single 21" horn-vented hybrid. It is vented for high sensitivity at the very low notes and incorporates a short horn for the massive impact that horns deliver. With the VS21, two boxes are not required to get to the low notes. It's also essentially the same size as the ones you’re using now.

We don’t promise you’ll get 5dB more "extra" output when you add a second one, over and above the normal 6dB, but you do get all 11dB more “where it counts” at 30Hz all the time. 

Thanks again for your compliments, and if there's anything else you'd like to discuss, please reach out again.

David Lee
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Thank you so much for the response ! Very detailed ! So I have varified the 105db by supplying a sine wave at 44hz of 2.83v at the speaker terminals and used an c weighted meter . Outdoors I got 103.6dbc@1m 2.83v 8 ohm driver. but this was c weighted which means I am in the 105 range advertised dbz. With 2 cabs at 2.83v 1 m I am reading 113.9dbc . It very well could be added directivity. Someone told me the design was made for b and c and it was considered a bass pipe resonator, which I have no clue what that means but it seems to make it very efficient at 42hz and 85hz . they have a pretty sever dip in the 50-60 range that you can see on the chart, but on my personal cabs the dip is even bigger then the b and c chart shows. The dip is frustrating at the very least but I live with it cause 40hz-50hz is so strong.under 40hz they fall like a rock tho. the vs21 would kill my subs down there and I haven't gotten a chance to try or even hear on yet [frown]
but 11db is serious gain in output!   .... anyways I really appreciate the time to model this, and I seriously wonder why it measures better then it models? Have you ever heard of a (basspipe)? is that even a real thing? I've heard of a transmission line... and mabe it explains the efficiency difference in the model and the real world measurement ? maybe these are more of a transmission line then a horn sub?
(I updated this response today as I had some typos in the data. I will update the pics with a measured 28.3v@10meter dbz response graph with one and then two subs as soon as I can get them set up in the backyard)
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Here is the chart. This was dead center 10m out , using sine waves at 1hz intervals at 28.3v the db is unweighted . What is strange is a few ft off center the 60hz dip is not so bad... they seem to have a sweet spot 5ft of center one each side which I found very strange. Mabe it's the v shape of the horns placed toghter? Anyways here is the data sorry it to so long to get it but we got a big snow storm and to wait for some melting to test in the field :/
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David Lee

Well it seems we're all being pretty slow to get to this one... but here we go!

It's very hard to say what may account for the gain you're seeing. It does seem to be concentrated at the peak, and not as much in the trough, so it could well be related to resonances. It could be a reflection, aka constructive interference, but you say the additional 5dB isn't observed indoors, but it is outdoors, so one would expect a lack of reflections outdoors.   

Those boxes are not particularly flat. One might say they are noticeably nonlinear. There is a resonance causing them to peak at 42Hz, and its double, aka second harmonic, 84Hz. 

It very well could be related to a physical dimension of the enclosure, perhaps in the range of 40". Which leads to another possibility related to dimensions... 

If the response is more linear off-axis then it may well be that the measured increase in SPL at one location, in the middle, is offset by a loss of energy elsewhere, with the average net gain being the expected 6dB. The 6dB increase in SPL is expected to occur equally throughout the radiating area of the loudspeaker, so if the coverage area is reduced, the energy is concentrated and may measure greater than 6dB over that smaller area. Inside of a venue, the reflections from walls and ceiling may mask the directivity effects and result in the SPL reading showing a broader average of the pair’s energy output. You would need to average a number of readings with the mic in various locations outdoors to test this theory. 

I also see that rather than gain the same amount of energy at 60Hz, relative to the average, your boxes lost energy at about 62Hz. This may be due to a reflection in the measurement environment or an inconsistency between boxes and/or drivers and/or amps. It would be very helpful to see phase and coherence information along with the SPL graph in order to analyze the data for possible causes. You’re welcome to ship them here for a complete battery of tests! 

Another possible cause of the inconsistency of the change is in the amplifiers. Have you verified that both amps are delivering the same output voltage at the same frequencies at the same time? If one channel of a bridged amp is a little weak, or if the high-pass filter switches are set differently, or if the gain knobs are corroded, the output of amp B could be very different in voltage and phase from amp A. 

On your other subject, of what you can live with, allow me to throw in my $0.02c. I know it's hard to give up on a lot of output at certain frequencies. Maximum SPL is very often seen as the highest ideal, taking precedence over accuracy. My philosophy is to reproduce the highest possible SPL without sacrificing accuracy. 

What I want is a speaker that plays the notes of the music at the same level that they were recorded, or that they are played live by the artist and their instrument. With regard to your speakers, consider there is an octave between the two peaks in their response, the E at 42Hz and the E at 84Hz. All the possible notes between the two peaks will be reproduced at a lower level, making the music slave to the speaker's preference, rather than the speaker doing the music's bidding.

It’s much easier to make something that will be very loud over a narrow operating band than it is to make something that operates accurately over a wide operating band with the ability to maintain that characteristic at high output levels. There are countless boxes that are able to produce impressive SPLs at certain frequencies. The term “one-note-wonders” was coined for them. When you hit that one note, they bring the house down, but all other notes are relegated to the background. Worse still, the speaker’s resonance acts as an EQ boost at its peak frequencies, making all notes on either side of the peak come out sounding like that one note. To me, that becomes very frustrating to listen to. 

Just a thought on that subject, you might try EQ-ing your boxes to be a bit less peaky. You may not be able to boost the trough enough to deliver flat response at max SPL but it might make the output more consistent when you’re not pushing the limits… And I know it would be sacrilege to suggest pulling the peaks down a little bit! [crazy]


David Lee


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Dave ! let me first say you hit the nail on the head. And with what you said I got it!!
it took me buying better measurement tools. I have phase traces know and I can see I had a flaw in my measurement technique .I recently got smaart v8. With that tool I can see what it was.

all my errors in measurements, I gave you bad info. 

#1 error. when I measured for sensitivity@2.83v I had one cab all by itself, it was about 105db at 1m 44hz.  however when measuring the coupling effects I did not isolate the cabs or recheck the voltage for single cab measurements. I simply unplugged one cab. brought the spl up to 105 (figuring that was still 2.83 volts like it was before), and plugged the next one in. what I didn't know was there was a large 4db dip in the response of the single cab at certain frequency's when the unplugged cab was next to it. I was driving them w closer to 4 volts. when plugging in the other cab you gain 6db, and remove the 4db dip that was caused from cab 2 previously being unplugged. adding up to what appeared to be about 11db at certain frequency's. however it was really only 6-8db. I just was driving it harder then I know because I never rechecked the voltage, not realizing the unplugged cab was robbing spl , cause me to crank up the voltage.

#2 there was a house in the vicinity of the testing that I assumed was far enough away to not effect it, however it was effecting 60hz as you said. I tested further away and the 60hz issues are no longer

#3 with the better measurement gear I can see the real gain at all frequencys and will post update response of a isolated cab, and a pair of them. on the same amp at same drive levels
the graph will tell the story.

however here is what I learned by isolating the cabs totally for testing.

there IS more then a 6db gain as you drop in frequency. this gain seems it peaks at around 35hz where it is near 8db. not 11db like I previously thought.

attached is a single cab isolated response , I will attach the comparison later.
in pink is w no processing at all. blue is just with my processing and filters. it didn't take a tremendous about of eq to get rid of the dip once I was away from the house more. 
no smoothening was used, this is the raw data. for a point off reference. 0db is approx. 102db 1w1m but smaart doesn't read sine wave sweeps. so this is based on the fast that I know the peak near 44hz is 105dbz

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David Lee
Congratulations on getting Smaart V8! It's an awesome tool and knowing how to use it will put you ahead of 99.8% of "sound guys" out there. 

One of the characteristics of horns is that they do benefit from coupling more than direct radiating boxes. This is mostly due to the fact that most portable horns have insufficient radiating area relative to their flare constant and length. Putting two or more together helps them achieve more of their potential. This is what accounts for the greater than 6dB improvement in performance when two or more are coupled. To put that another way, they need to be coupled in order to get closer to their optimal performance. What you're seeing there is how, with just one, the lack of radiating area causes a greater than 6dB loss in sensitivity compared to two. 

Your net result with the processing looks like a very effective system from 40-100Hz!  It looks better than many big-name brands I have measured... Congratulations again! 

David Lee
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Thank you so much for all the info and help and kind words! Your support is far better then any other brand I have dealt with. At the end of the day what I described as gaining more then 6db is more makeing up for an lack of effecnincey In portable horns, then it was a gain in coupling. When you use more the one a side your just fix one of the many issues horns have... I want to add One thing. I was playing with the bass boss and yorkville again, I noticed with sine waves the 801p falls on its face. The limiter clamps way down after less then one second. Or the amp is out of gas. Idk which it is. But it’s not gonna work for edm that’s for sure.. But the bass boss. The baby keeps the bass coming till I let of the sine wave!. Which got me wondering ,When you test w a sine sweep, how long does the sweep last? Cause I gota say, those amps in that thing can keep the power flowing ! And I feel like a long sweep would best demonstrate that .
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