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Multi-Way Conventional loudspeakers with crossovers

Seas Excel W18EX001 vs Scan-Speak 18M/4631T00
Seas Excel W18EX001 vs Scan-Speak 18M/4631T00
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Old 28th June 2018, 11:49 AM   #11
3wayaddict is offline 3wayaddict  Netherlands
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I've already considered those for a previous concept but moved away from them because I know they are good but Scan-Speak are the best. So now you're all of the sudden saying I can't use any midrange of that size? You just said about the 18W I can cross it as high as I want.
Do you think I should take a better (dome) tweeter? Domes with the same kind of frequency response are expensive and I already have the NeoX3.0's so it will be a pain in the *** but maybe I can do a little trading.
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Old 28th June 2018, 11:52 AM   #12
TMM is offline TMM  Australia
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18W measured here:
http://www.zaphaudio.com/6.5test/18W8531G-HD.gif
http://www.zaphaudio.com/6.5test/18W8531G-FR.gif

18M here:
ScanSpeak 18M/4631T00 | HiFiCompass

These measurements are from different sources so we have to compare them with a grain of salt, however I trust that the measurements are accurate from these guys. We also have to assume that 8ohm and 4ohm drivers measure similarly in frequency response smoothness and harmonic distortion (they usually do).

Comparing harmonic distortion:
Unfortunately we can't compare the 2nd order harmonic as the microphone used at Zaph audio has a 2nd harmonic noise floor of perhaps -50 or -60dB. This is a common problem with inexpensive measurement mics. The mic used at HifiCompass seems to be considerably better. Higher orders are unaffected.
The overall level of harmonic distortion seems to be very close between the 18M and 18M. The 18W peaks up in 3rd order distortion at 400Hz and the 18M peaks up with similar severity at around 1kHz. These are probably due to minor cone/suspension resonances. Take your pick - they are both very good performers.

Comparing Frequency Response:
The 18W rises about 4-5dB from 1-2kHz whereas the 18M only rises about 3dB. Perhaps the 18W might be a little bit smoother overall. This might just be indicative of the two different measurement setups though.

If I had to pick from these results, I'd go for the 18W. The T/S parameters also allow for a slightly smaller box without excessively high Q. If i recall correctly, HifiCompass prefers the 18M - maybe they can chime in with their opinion. Theoretically the 18M should be slightly lower distortion in the midrange because it has a shorter stroke motor (lower xmax) however I don't see any significant difference in these measurement results. Perhaps inter-modulation distortion testing is needed to reveal this advantage, however I would guess that if there is any advantage it is only slight since the harmonic distortion sweeps show such similar performance.

Both are very good drivers and I think you'll be happy with either.

Quote:
Originally Posted by Mario Pankov View Post
Any midrange with a size of the 18M will start beaming at 2Khz or so, for your crossover point a Satori MR16 driver may be better suited.
An MR16 is barely any smaller in diaphragm size than a Scanspeak 18cm. If a SS 18cm has unacceptable beaming above 2kHz then an MR16 is unacceptable above 2.3kHz. Not a big difference. To significantly improve on the SS radiation pattern you need to go to a much smaller driver - say 3-4" and this won't be able to cross at the 250Hz needed.

edit: The on-axis performance of the 18W/18M dictates no hard limit on the crossover frequency because it is exceptionally well behaved all the way up - the frequency response is smooth and the harmonic distortion doesn't rise out of control. You do however have to decide how high to cross to maintain good power response (smooth off-axis response) due to the size of the drivers and centre-to-centre distances. I wouldn't cross any higher than 3kHz because of the size of the mid and the achievable centre-to-centre distance with the tweeter. Crossing higher than that will result in a considerable dip appearing in the system frequency response at a relatively shallow off-axis angle. As always, lower crossover frequency is always better for power response. For near-perfect power response you want to cross a 6.5" woofer at about 1kHz. Obviously you'll have to compromise because almost no tweeter will play that low. It's up to the speaker designer to pick a frequency which achieves acceptable power response and doesn't push the tweeter too hard (making it distort).

One solution is to put another driver of an intermediate size between a 6.5" driver and a tweeter - say a 2" dome mid then cross at say 700Hz and 3kHz. Another is to substitute the 6.5" driver with something smaller (~4.5") and have your bass driver play higher - perhaps 400Hz instead of 250Hz. This goes against the idea to get one driver playing as wide a frequency range as possible however. Everything is a compromise in one way or another - just gotta pick your battles

Last edited by TMM; 28th June 2018 at 12:16 PM.
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Old 28th June 2018, 11:58 AM   #13
krivium is offline krivium  France
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If qtc don t match with the target you have and you have sealed box for it you can use Linkwitz Transform to make Qtc and FS you want to achieve. As you don t target low end extension you may have benefits in term of Spl.

About the larger sd, distortion increase with movement of membrane of loudspeaker. Increased sd means louder yes, but it means lower movement so lower thd for a given spl.
That is one of the reason some prefer larger drivers for mid duties ( 12" or 15"). I m one of them.
There is an interesting paper about B&W engineers about that when they switched from one 15" to 2x10' in 803 models (iirc). Engineers thinked it sounded better with one 15, marketinf department it would sell better with 2x10".
Apparently they sell better.
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Old 28th June 2018, 12:03 PM   #14
Zvu is offline Zvu  Serbia
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2 x SB12MNRX25-4 in mtm with that ribbon can quite easily cross low enough and high enough.

Real world measurements are quite satisfactory.

Click the image to open in full size.

Quote:
Originally Posted by TMM View Post
.... To significantly improve on the SS radiation pattern you need to go to a much smaller driver - say 3-4" and this won't be able to cross at the 250Hz needed.
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Last edited by Zvu; 28th June 2018 at 12:06 PM.
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Old 28th June 2018, 12:06 PM   #15
3wayaddict is offline 3wayaddict  Netherlands
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I'm sorry but they are less than €50,- each. Not something I expect a lot of in terms off quality disregarding their low moving mass.
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Old 28th June 2018, 12:08 PM   #16
Zvu is offline Zvu  Serbia
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Well, i'm sure they can charge you more if you ask them nicely (:

Quote:
Originally Posted by 3wayaddict View Post
I'm sorry but they are less than €50,- each. Not something I expect a lot of in terms off quality disregarding their low moving mass.
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Old 28th June 2018, 12:10 PM   #17
krivium is offline krivium  France
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Price doesn t (always) equal quality.
Coherency and synergy between driver may outcome in better results that a very pricey item with one not on par with it.

Zvu: LOL.
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Old 28th June 2018, 12:21 PM   #18
TMM is offline TMM  Australia
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Two SB12s in MTM is going to have similar problems with off axis response as a single 18W because the entire assembly (M+T+M) is going to be similar in height to the larger M+T. edit: in the vertical axis at least, which is the main concern here since we are pushing the XO frequency higher than is optimal. Horizontal response will be improved, but that's not the axis that will experience a major problem in the first place.

Last edited by TMM; 28th June 2018 at 12:27 PM.
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Old 28th June 2018, 12:30 PM   #19
3wayaddict is offline 3wayaddict  Netherlands
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If I can return my NeoX3.0's for around €200,- and earn another €125,- by selling other left-over drivers (which I was already selling anyway) and maybe ask one driver or some crossover components for my birthday I might be able to take new dome tweeters and fit it in the maximum time I want to spend raising money. Maybe (and that's a real strong maybe) I might even ask some components or a driver for Sinterklaas (it's like dutch Christmas) as well.
The Scan-Speak Illuminator D3004/6620.00 looks really good. I often see people cross those lower, right?
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Old 28th June 2018, 12:36 PM   #20
krivium is offline krivium  France
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I can t answer you about reference or your choice and preference but if you want to use a dome tweeter there is possibility to load it by a waveguide. It will make lower xover possible and you ll gain controled directivity.

Here is an example:
The Boxers | Parts Express Project Gallery

Last edited by krivium; 28th June 2018 at 12:42 PM.
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