Hello there 
A few weeks ago i built the zaph zd5. I am very pleased they sound great. Very clear and neutral. After comparing them with my canton digital 1 with 2 10 inch woofers each and capability of reaching down to the 20 hertz region i began to miss the feeling of power of the big canton towers in the sub range. The zd5 make a fool out of the cantons in every other aspect though.
Now i have begun to do some research and stumbled upon troels ellam flex 3w with the addition of his bass cabs.
Ellam-FLEX-3W
He uses the same mid woofer the 15w/8530 k00 so my first thought was to use the same woofer drivers as he does. They are however a bit pricey.
Ive also looked at some gr research servo controlled subwoofer kits.
As i see it i have a two options.
Build two bass extension cabs that i can cross between 100-200 hertz und play down depending on the woofers and their price to the 30 hertz region.
An 8 or maybe even 10 inch driver.
Or build one good subwoofer maybe a gr research servo controlled one or buy a rhytmik l12 even though both of these would cost me around 700 bucks.
The sub would go lower but troels mentioned that with his bass extension he gets a better („more powerful“ maybe he means max spl?) response from 200 hertz downwards.
What kind of solution do you prefer and or think is better? My listening room is rather small around 45-50 qubic metres i think.
Also what do you think would be a good sub driver for this experiment that are around 200 usd or less. Ive seen a local ad for two 21w/8555-01 for 90 usd each.
Thanks in advance for all your help
A few weeks ago i built the zaph zd5. I am very pleased they sound great. Very clear and neutral. After comparing them with my canton digital 1 with 2 10 inch woofers each and capability of reaching down to the 20 hertz region i began to miss the feeling of power of the big canton towers in the sub range. The zd5 make a fool out of the cantons in every other aspect though.
Now i have begun to do some research and stumbled upon troels ellam flex 3w with the addition of his bass cabs.
Ellam-FLEX-3W
He uses the same mid woofer the 15w/8530 k00 so my first thought was to use the same woofer drivers as he does. They are however a bit pricey.
Ive also looked at some gr research servo controlled subwoofer kits.
As i see it i have a two options.
Build two bass extension cabs that i can cross between 100-200 hertz und play down depending on the woofers and their price to the 30 hertz region.
An 8 or maybe even 10 inch driver.
Or build one good subwoofer maybe a gr research servo controlled one or buy a rhytmik l12 even though both of these would cost me around 700 bucks.
The sub would go lower but troels mentioned that with his bass extension he gets a better („more powerful“ maybe he means max spl?) response from 200 hertz downwards.
What kind of solution do you prefer and or think is better? My listening room is rather small around 45-50 qubic metres i think.
Also what do you think would be a good sub driver for this experiment that are around 200 usd or less. Ive seen a local ad for two 21w/8555-01 for 90 usd each.
Thanks in advance for all your help
Thanks for your feedback!
I didnt buy them yet. I modled the zd5’s on vituixcad and it seems that i need a sensitivity of around 80 db in the end. With baffle step loss in mind this would equate to a woofer with 86 db sensitivity. Makes sense since the 15w in the zaphs are also 86db USPL.
Due to driver spacing i will cross at no more than 300 hz.
With the 21w i think i would go sealed and start with one driver per box and maybe add another in series.
Since i am using a dsp anyways could i use the 21w and simply reduce sensitivity from crossover point downwards or is there a way to resuce sensitivity passively? The 21w have 1.5db too much uspl. I have heard a shunt resistor is considered bad for woofers as it alters qts.
I didnt buy them yet. I modled the zd5’s on vituixcad and it seems that i need a sensitivity of around 80 db in the end. With baffle step loss in mind this would equate to a woofer with 86 db sensitivity. Makes sense since the 15w in the zaphs are also 86db USPL.
Due to driver spacing i will cross at no more than 300 hz.
With the 21w i think i would go sealed and start with one driver per box and maybe add another in series.
Since i am using a dsp anyways could i use the 21w and simply reduce sensitivity from crossover point downwards or is there a way to resuce sensitivity passively? The 21w have 1.5db too much uspl. I have heard a shunt resistor is considered bad for woofers as it alters qts.
Thanks for your reply. I think to be able to experiment a bit i will go the active route.
So now i have decided to make the crossover activ and program a dsp to do the job.
Now im left with driver choice. Dont look too much at the specific driver choice and more at the general 4 design ideas.
1): 2x8 per speaker sealed with sb23nbac both play all the way up to somewhere at 300/400 hz. Sealed with lw transform.
2): 1x8 21w8555-01 up to 300/400 sealed and 1x 10 inch per speaker for example the sb29nrx or sb29swnrx crossed at around 100hz here i would not need to side mount the sub.
Here i would probably go vented.
3): 2x10 like the sb29nrx up to somewhere between 200/280. Here sealed with lw transform
4): 1x8 21w8555-01 up to 300/400 and a 12 inch side mounted woofer crossed at around 80-100hz like ne315w or the sb34swnrx-s75. Here i might also go sealed with lw transform
Really sorry for all the questions, im not expecting to get a perfect answer as there is probably none and it aleays dependa on the use case.
The main questions in my head is:
How low can the 15w revelator play? And where is it optimaly crossed. 200,300,400?
How high can a 10 inch like the sb29nrx play?
And is it better to have a dedicated 8” upper bass + 10-12” lower bass or two 8-10” bass drivers covering all the bass spectrum?
So now i have decided to make the crossover activ and program a dsp to do the job.
Now im left with driver choice. Dont look too much at the specific driver choice and more at the general 4 design ideas.
1): 2x8 per speaker sealed with sb23nbac both play all the way up to somewhere at 300/400 hz. Sealed with lw transform.
2): 1x8 21w8555-01 up to 300/400 sealed and 1x 10 inch per speaker for example the sb29nrx or sb29swnrx crossed at around 100hz here i would not need to side mount the sub.
Here i would probably go vented.
3): 2x10 like the sb29nrx up to somewhere between 200/280. Here sealed with lw transform
4): 1x8 21w8555-01 up to 300/400 and a 12 inch side mounted woofer crossed at around 80-100hz like ne315w or the sb34swnrx-s75. Here i might also go sealed with lw transform
Really sorry for all the questions, im not expecting to get a perfect answer as there is probably none and it aleays dependa on the use case.
The main questions in my head is:
How low can the 15w revelator play? And where is it optimaly crossed. 200,300,400?
How high can a 10 inch like the sb29nrx play?
And is it better to have a dedicated 8” upper bass + 10-12” lower bass or two 8-10” bass drivers covering all the bass spectrum?
My recommendation is to go active with Hypex FA122 or bigger two-way module. To integrate woofer(s) higher than 80Hz you must control also midrange's low-end (high-pass) and propably delay to get good phase match and integration. The real challenge is that one must stop worrying about dsp, classD amps and interconnects! Active stereo pair can be intergrated to HT system too, but dsp delay must be compensated.
With active, driver selection is much easier! I just made a 3-way with two 8" ScanSpeak 21W sealed. The problem with actives is that taking measurements is necessary, but difficult indoors. I think that I must drag a speaker outdoors in the summer...
https://www.diyaudio.com/forums/multi-way/321711-avalanche-as1-modernization-3.html#post6553339
With active, driver selection is much easier! I just made a 3-way with two 8" ScanSpeak 21W sealed. The problem with actives is that taking measurements is necessary, but difficult indoors. I think that I must drag a speaker outdoors in the summer...
https://www.diyaudio.com/forums/multi-way/321711-avalanche-as1-modernization-3.html#post6553339
Thanks for your replies. Cool project with the two 21w. Measurements shouldnt be too big of an issue. Reason why i want to go the dsp route is simple. I can have dsp kits from aliexpress really cheap for 40 usd so buying a dsp plus building a class d poweramp would cost me around 200 bucks. Since i have a preamp plus power amp combo anyway this would be all i need. Dsp between pre and two poweramps. This way the dsp delay would be present on all channels if programmed correctly. This is however my first time doing this so i might be wrong. Using four 21w like you did would be my dream however i can only get 2 at a decent price :/ currently the plan is to take two sb23sbnac or two sb29nrx per channel.
SB29NRX is excellent, works sealed and dsp very well, I used those in another project with FA123.
SEAS MR18 3-way
SEAS MR18 3-way
You might want to investigate the Dayton rs225 woofers. There is a reason they still show up in projects. If I remember correctly, when they came out they had some of the best distortion characteristics available in the upper bass range. Unfortunately the site with the measurements is gone now. Looks at the statements for an example
Thanks for the recommendation. Yes i have heard only the best of this driver. Only reason im not using it are its looks.
Ive just fond something interesting. In the kairos 3-way jeff bagby used the cs sdx10 for 200 usd per driver. Now, i have found the peerless sdf250 with nearly same mms and an even stronger magnet. What do you reckon how these drivers compare? Can it play up to 200 hz?
It is fairly new (2017) but seems to have very good reviews.
Peerless by Tymphany SDF-250F75PR01-06 10" Paper Cone Subwoofer
Ive just fond something interesting. In the kairos 3-way jeff bagby used the cs sdx10 for 200 usd per driver. Now, i have found the peerless sdf250 with nearly same mms and an even stronger magnet. What do you reckon how these drivers compare? Can it play up to 200 hz?
It is fairly new (2017) but seems to have very good reviews.
Peerless by Tymphany SDF-250F75PR01-06 10" Paper Cone Subwoofer
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My mistake. You are looking at a woofer that you don’t know much about and that is similar in cost to the css. You are going to run in into the low midrange but you don’t have any distortion measurements so you won’t have any idea how it will perform.
There are two woofers used by Jeff bagby in the bass bin design. There is the css and an an acoustics woofer which costs a bit less.
Without information about a woofers performance, you are kind of rolling the dice. You would likely do better if you use something that has been demonstrated to work well in the application you want it for. I can’t imagine you could go too wrong with the sb acoustics 29nrx or one of the Dayton rs225 drivers.
There are two woofers used by Jeff bagby in the bass bin design. There is the css and an an acoustics woofer which costs a bit less.
Without information about a woofers performance, you are kind of rolling the dice. You would likely do better if you use something that has been demonstrated to work well in the application you want it for. I can’t imagine you could go too wrong with the sb acoustics 29nrx or one of the Dayton rs225 drivers.
There is also the peerless sls 830668. They are cheaper but they show up in many projects. The tarkus speaker uses them up to a similar frequency but the mid woofer in that project is not of the same caliber as yours. You can use them sealed or vented but the vented cabinet is somewhat large. Solen has them on sale but perhaps you can get them locally for less.
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