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Multi-Way Conventional loudspeakers with crossovers |
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#1 |
diyAudio Member
Join Date: Oct 2017
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As the title suggests: how much hornloading can we expect a synergy to have for the sub 500hz frequencies? I guess it depends on the horn used?
I will be using a large biradial horn, with a 108x75cm (42,5"x29,5") mouth. I will be converting it into a 2-way with a 500hz crossover point, so off axis ports at 17cm (6,7"). I was planning on using 2x 15" drivers. Question is: - is there a ballpark estimation / rule of thumb to knowing how much hornloading this wooferpair will be able to get. Lets say over a 80-500hz range. - Or should I model this? I'm not at home in all this software (like hornresp) so I dont really know how to do this. - also, would this be a good range to use 18" drivers for? Or is this counterproductive? |
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#2 |
diyAudio Member
Join Date: Nov 2007
Location: Arlington, TX
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To give you an idea of the raw response of a Danley SH-50, dual 12" woofers (blue trace) vs. the K-402-MEH dual 15" woofers (green trace):
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#3 |
diyAudio Member
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#4 | ||
diyAudio Member
Join Date: Nov 2007
Location: Arlington, TX
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You can use 18" drivers, but my experience with 15" drivers having about the same T/S parameters as the Klipsch K-33 woofer (I actually used two 15" Crites cast frame woofers) usually will give you a very good starting point to try out your initial ideas. I've found that the information that Hornresp gives you actually very limited, i.e., it does the off-axis port location simulations pretty well, but it really won't tell you the SPL on-axis--which is really non-flat response, as you can see from the raw response I posted above--or really what the effects of off-axis port area does. BTW: I recommend staying with two elongated 2.4-2.6 inch diameter off-axis ports for your 15" woofers, figuring a compression ratio of about 10 as a rule-of-thumb maximum in order to get good efficiency (woofer piston area to off-axis port area). Using undersized woofer ports is something that I don't recommend right off the bat. So 18" woofers would provide even more low end than two 15" woofers, but note that I already get sub-20 Hz performance out of the prototype K-402-MEH with very little EQ (~5 dB below 40 Hz when in elevated mid-wall loading). The response of the MEH will be subject to room placement much more strongly than even a "W"-shaped corner horn bass bin, so you need to place the MEHs against a wall, and corner placement will give you a great deal more low end response without EQ boosts...about 6-8 dB more SPL below 40 Hz. If midrange early reflections are an issue around the MEH/wall location in quarter space or eighth space loading, simply add one or two (stacked vertically) 2'x2'x1" absorption pad at the horn mouth exit on the adjacent walls. I wouldn't try to do the crossover with anything but a good DSP crossover unit. You might be able to use something as inexpensive as a miniDSP 2x4HD (but not the 2x4), but note that its unbalanced connections will be more difficult to shield from line noise (50/100 or 60/120 Hz) which will be somewhat audible using the miniDSP 2x4HD unless special precautions are made. Chris Last edited by Cask05; 3rd June 2019 at 02:58 PM. |
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#5 | ||
diyAudio Member
Join Date: Oct 2017
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As I will be using active crossovers, I do think it wont matter too much what the exact sensitivity is, but I do want to know this to match the woofers to the driver. I know you initially matched your compression driver with 2x15" Crites woofers, but I was wondering what the woofer matching would end up to be when using a more powerfull driver like the BMS 4594 (a driver you also ended up testing). The TAD 4002 or Radian 951 drivers would only achieve a 125-130db output @RMS, while the BMS would achieve almost 140db. I would love to be able to use my high-end sound prioritized synergy horn, as a kind of PA speaker like Danley Sounds use theirs. I dont think I would really be compromizing quality by using the BMS coaxials, ánd it would give me a much more potent PA speaker. It would however require more lower end power. Without hornloading an Eminence Kappa 15A driver pair would have 130db at RMS, so maybe x4 with hornloading could get close to this 140db of the BMS. When using in my home I would love to have a good lower end from the synergy itself, which is already confirmed by your measurements Chris. Down to 20hz is amazing! When using for PA like situations, I would never cross this low, and I would rather use horn loaded subs to supplement. Crossing at 100hz or higher could maybe help push the synergy its woofer output without distorting. Last edited by Droco; 3rd June 2019 at 07:59 PM. |
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#6 | |
diyAudio Member
Join Date: Nov 2007
Location: Arlington, TX
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I'm actually using the BMS 4592ND, not the 4594. Note that the measurements above were done in quarter space loading--as you would likely see in a home hi-fi environment. If you're talking about full space operation, like is common in PA environments, subtract about ~12 dB below ~100 Hz. Chris |
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#7 | ||
diyAudio Member
Join Date: Oct 2017
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In any case, way more than the TAD, Radian or JBL 2446 drivers. So it would make more sense to use more/more powerfull woofers right? |
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#8 |
diyAudio Member
Join Date: Dec 2010
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Hi Droco,
I'm a little confused as to whether you are working on a synergy with the 4594 and woofers in the same horn, or working on two separate horns. It sounds like a synergy, given you mentioned a 17cm port distance for crossing at 500Hz...but just want to make sure I understand you. I've also been considering the 4594(HE) for a synergy using the same 500Hz crossover point. I thought i was good-to-go with 17cm of room to the apex, ....until I measured the acoustic path length of the driver. It's a huge 11cm from the driver mounting face to the acoustic source!! Which seems to make it pretty much impossible to use larger drivers, without crossing substantially lower. I'm new to synergy calculations though..hope I'm making a mistake. And maybe the non-HE 4594 has less acoustic depth?? |
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#9 | |
diyAudio Member
Join Date: Nov 2007
Location: Arlington, TX
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If you're really serious about very high SPL operation, I'd recommend following suit in the woofer section. They also claim 101 dB sensitivity using passive crossovers, so you should be quite efficient using DSP crossover in quarter or eighth space loading. EDIT: Sorry, I forgot about the reflex ports in the SH-96, which limit its LF output to above 40 Hz (recommended HP frequency). However, in sealed box configuration, the LF performance that I mentioned above would still hold. Chris Last edited by Cask05; 3rd June 2019 at 10:30 PM. |
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#10 | |||
diyAudio Member
Join Date: Oct 2017
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Very interesting design though! Good inspiration for off axis port placement etc. I wouldnt try to boost the synergy down to as low as they do I think. It's nice if its capable to do so (for hifi use), but for PA use I'd rather couple the synergy with something like an Othorn and a 100hz crossover. The othorn can do 100hz perfectly, and it would give a 85cm 1/4th wavelength distance, which is close enough to place them together. If I really want to go over budget and floorspace, I can maybe do double othorn with a mega synergy on top for the "ultimate" PA setup. |
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