I have been mulling over this speaker build for awhile now. The general idea is that, in an attempt to make the speaker somewhat directional between 500Hz and 1kHz, I would like to mate a large format pro woofer to my SEOS-18 horn. The crossover point will be right around 1kHz or slightly below, and this horn with the right CD will do it.
I was previously planning to use the Selenium 18WS600. I bought a pair and did some ground plane measurements (driver alone, no baffle) on and off axis to get an idea of what I was up against. These are attached, below. This is a dipole-type response and in a box the frequency response will be different. Specifically, the drooping response region below 1kHz may be completely different. Distortion (See plot below) remains relatively low at this power level (1W ish) so this driver could work. I did not make any waterfall type measurements, which might be something to check first.
I've always wondered if there was a better choice in an 18" format out there, that would give me a little smoother response through 1kHz. So I thought I would throw this out for comment to the forum to see if anything new is out there that would work better than the Selenium drivers I already own. Is there anything?
I was previously planning to use the Selenium 18WS600. I bought a pair and did some ground plane measurements (driver alone, no baffle) on and off axis to get an idea of what I was up against. These are attached, below. This is a dipole-type response and in a box the frequency response will be different. Specifically, the drooping response region below 1kHz may be completely different. Distortion (See plot below) remains relatively low at this power level (1W ish) so this driver could work. I did not make any waterfall type measurements, which might be something to check first.
I've always wondered if there was a better choice in an 18" format out there, that would give me a little smoother response through 1kHz. So I thought I would throw this out for comment to the forum to see if anything new is out there that would work better than the Selenium drivers I already own. Is there anything?
Attachments
Last edited:
It's a bit pricey, but the bms 18n862 has worked very well for me sealed, single vented, and double PPSL vented. Josh Ricci describes the driver as a cross between hi-fi and pro-audio...
Below is a raw response in sealed box, mic about 6" from dustcap. 1/12 smooting mag and phase
Below is a raw response in sealed box, mic about 6" from dustcap. 1/12 smooting mag and phase
Attachments
Good morning Charlie! How are things in MI? The measurements you posted are pretty typical for a low - mid cost 18" designed for PA sound reinforcement applications. So, it comes down to the usual trade offs driven by cost, box size, efficiency, low end cut off and all the rest. I have used a few of the PE 460-8. The frequency plot is pretty close to what they publish. T/S specs have been consistently per published data also... not bad for a driver that can be had for $90 - $100 each including shipping. J
Hi John,
Great to hear from you. Moving to MI has really put a damper on my DIY efforts but I am starting to get up and running again now. I have the Selenium drivers already, and am trying to do a cost-benefit analysis before using them or buying a different set of woofers.
The low end performance is not important for this 2-way home audio PA-monitor-style design. There would be a separate sub or subs below 100-150Hz with the woofer+horn in a sealed box. OR at least that is the plan.
The use of the 18 is primarily for pattern control below 1kHz.
The BMS 18n862 is more of a subwoofer and the response barely makes it above 1kHz. I'm looking for an 18" driver with extended mid-frequency performance and low distortion. This is often an underhung v.c. type design like the Selenium.
Acoustic Elegance has a few nice options, but price is $350-$450 each and so a pair represents (for me) a serious investment...
Another vote for multiple smaller drivers.
MMTMM with a set of 4x 10" woofers mounted in two horizontal pairs above/below the HF horn would give the right sort of directivity control, and the smaller cones will be fine out to ~2kHz. You've then also got the option to make it a 2.5-way if you wanted wider dispersion.
Chris
MMTMM with a set of 4x 10" woofers mounted in two horizontal pairs above/below the HF horn would give the right sort of directivity control, and the smaller cones will be fine out to ~2kHz. You've then also got the option to make it a 2.5-way if you wanted wider dispersion.
Chris
Hmmm, I hadn't thought about that. Not a bad idea. I will do some modeling and see what the directivity looks like.
OK, I did some basic modeling of the 4x 10" woofers using The Edge. It's probably not going to work well. The sims show a null at 45 degrees by 800kHz. That's way too much "directivity"...
Could four 8" work? I do have four truncated frame 8" woofers but after modeling that configuration the null only moved out to about 1.2kHz!
I seem to recall from past checking that multiple small drivers are always worse than one larger one of about the same diameter. I would probably have to drop down to four 6" drivers...
At this point it looks like the 18+horn is still the way to go... The null is out at almost 2kHz putting it well above the crossover point.
Could four 8" work? I do have four truncated frame 8" woofers but after modeling that configuration the null only moved out to about 1.2kHz!
I seem to recall from past checking that multiple small drivers are always worse than one larger one of about the same diameter. I would probably have to drop down to four 6" drivers...
At this point it looks like the 18+horn is still the way to go... The null is out at almost 2kHz putting it well above the crossover point.
Side by side two 15s would have too much interference in the lateral plane, so that arrangement would be out. An MTM with two 15s would have LESS directivity (laterally) compared to a single 18 and would be quite bad in the vertical plane due to the large driver spacing (the typical problem with MTMs).
I wonder why you think a 15" woofer is not directional enough.
What kind of dispersion did your simulation show for a single 15" (say around 800Hz)? Also, what is the dispersion of the SEOS-18 WG? ~120Hx80V?
For comparison, JBL M2 uses a single 15" woofer crossed over at 800Hz, and the Image Control Wave Guide used in M2 has a dispersion of 120Hx100V. 800Hz is the stated minimum frequency for SEOS-18 with a 1.4" throat, by the way.
As to two side-by-side 15s, could slot-loading the woofers be used to achieve the lower directivity you need? If the dispersion of one 15" woofer is too wide and the dispersion of two side-by-side 15" woofers is too narrow, maybe slot-loading or blocking will get you the Goldilocks spot of "just right."
Kurt
Last edited:
Yes, but that depends on the cone geometry and VC diameter to some extent.
The SEOS horn, from the measurements I have seen, loses pattern control (becomes more omni) below about 1kHz or so. So I if put the crossover point around there and combine that with a large driver that is starting to beam, my thought process is that the two will combine to create a smooth transition from the 18 below, to the horn above, 1kHz.
Also, the horn only accepts a 1" throat CD. Crossing over lower e.g. at 800 would be great, but that's not really a great idea for this combination IMHO.
I am attaching the MFG datasheet for the Selenium 19WS600. I has some FR plots and polars taken in the recommended cab that show that it can comfortable reach 1kHz. The question is whether this is about as good as can be expected, or is there a better 18 that can work up in this FR region?
Last edited:
So what would be your target key T/S parameters for your 18” woofer?
If you were to use the SEOS-18 with a single 15" woofer instead crossed around 1000hz, the nulls would be around 60deg apart (~12" CTC distance and 13.5" wavelength). With a 15”, you would also have a much bigger selection of “midrange” biased drivers.
The SEOS-18 has always been considered the odd one out in the SEOS line-up because it is only marginally better than the SEOS-15 (which can also be had much cheaper) and it is difficult to find a 1” CD that can take advantage of the extra bottom (e.g. BA750). Never use a waveguide larger than you need.
A more meaningful step-up from the SEOS-15 is the SEOS-24 but then it is 1.4” or 1.5” CDs and beaming above 12kHz...
If you were to use the SEOS-18 with a single 15" woofer instead crossed around 1000hz, the nulls would be around 60deg apart (~12" CTC distance and 13.5" wavelength). With a 15”, you would also have a much bigger selection of “midrange” biased drivers.
The SEOS-18 has always been considered the odd one out in the SEOS line-up because it is only marginally better than the SEOS-15 (which can also be had much cheaper) and it is difficult to find a 1” CD that can take advantage of the extra bottom (e.g. BA750). Never use a waveguide larger than you need.
A more meaningful step-up from the SEOS-15 is the SEOS-24 but then it is 1.4” or 1.5” CDs and beaming above 12kHz...
Last edited:
The Selenium 18SWS1100 maybe?
18SWS1100
Specified as a subwoofer but with an Aluminium ribbon VC rather than the more usual (for subs) Copper.
Perhaps a little better top end?
Best wishes
David
Last edited:
If I may, this is the info of the cheep driver.
Zomax PF-1875190K
same model rebranded is
Martin Wisman Kappa 18
Very good LF extension, reasonably extended highs regarding of the moving mass.
And ofcourse is not for the huge stated power but for home use is good.
I listened these drivers even in the OB cabinet 2xMartin Wisman Kappa 18 per chanel, and they performed very well.
.
cheers
Zomax PF-1875190K
same model rebranded is
Martin Wisman Kappa 18
Very good LF extension, reasonably extended highs regarding of the moving mass.
And ofcourse is not for the huge stated power but for home use is good.
I listened these drivers even in the OB cabinet 2xMartin Wisman Kappa 18 per chanel, and they performed very well.
.
cheers
Attachments
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.