|16th September 2019, 12:41 AM||#611|
Ha- right now they sit atop my digital piano in the other room. I have a nice pair of Lovan Ballet III 24" tall stands that they'll probably get mated to. I need to install a threaded insert on the bottom to attach them.
|18th September 2019, 07:21 PM||#612|
Join Date: Nov 2010
Location: Glasgow, UK
If you're intending to produce bass with it why not go for the more suitable W8-1808 which has 5mm Xmax instead of the 3mm Xmas of the W8-1772, a slightly larger diameter voice coil, and a higher Qts that lends itself well to bass reflex designs ?
Having looked at the specs of both drivers I would choose the 1772 if you were cutting it off below about 200Hz and passing over to a woofer of some kind, but if you want to produce bass as well the 1808 seems the obvious choice.
I have my Coral Flat 8 Mk 2's in a 43 litre bass reflex enclosure tuned to 41Hz using two 75mm diameter, 200mm long rear mounted ports.
This works remarkably well and I'm consistently impressed by how good the bass response is for a full range driver with such a light cone. (At least in a typical UK sized living room)
The Flat 8 Mk2 has the same cone area as the 1772/1808, about the same moving cone mass, (about 9 grams) the same 3mm Xmax as the 1772, and the other Thiele small parameters like sensitivity and Qts are very close to that of the 1808.
In other words the 1808 should work well in the same bass reflex cabinets as my Coral drivers, and probably better due to increased Xmax and underhung voice coil design with Neodynium magnet.
I'd also like to suggest that a single 3" / 75mm port mentioned above is too small in area for an 8" driver, even for a driver with only a 3mm Xmax, and that doubling the port area (and making it/them longer to tune back to the same box resonance) will improve the bottom end performance at higher SPL and reduce dynamic compression effects considerably, giving more low end punch at higher SPL where the smaller port would cause loss of loading on the driver and increased driver excursion and reduced output. (Not to mention chuffing)
I originally had a single 75mm diameter port on these cabinets, approximately 60mm long to get the correct box tuning (such a short port should be a clue in hindsight that the port area was too small) and there was noticable chuffing.
I later changed to two 75mm ports on the back - one 1/3rd of the way from the top of the cabinet and one 1/3rd of the way from the bottom with the driver in the middle of the front panel.
Not only did the chuffing go away the dynamic performance in the low frequency range where the ports are mainly active - from about 35 Hz to 50Hz improved dramatically, and they have plenty of punch in that region while the cone hardly moves.
So anyone not happy with their bass response who is using one 75mm port, if you have room for the additional port length consider increasing the port area by using two, longer ports, or switch to a bigger diameter, longer single port to achieve the same doubling of area. (Two ports was easier for me)
The next thing I would suggest for those that insist on using a 1772 (instead of an 1808) in a bass reflex enclosure or have already bought it and have second thoughts about its performance in a bass reflex enclosure is..... connect a resistor in series with it to raise the Qes...
I'll probably get a few groans from the audience for this but the correct value of resistance will increase the Qes of the driver to about the same as the 1808, and simultaneously drop the sensitivity from 95dB to 93dB'ish of the 1808.
In other words by simply connecting a resistor in series (a decent 10/20 watt one) you will get most of the properties of the 1808 that make it suitable for bass reflex designs, minus the increased Xmax. So it won't have quite the bass performance of an 1808 but it should be reasonably close.
I don't know without running some box sims with both drivers what the value should be, but it's probably in the range of 1-3 ohms, and can probably be tuned empically to optimise the balance of the bass response.
This resistor will of course affect the response at higher frequencies due to the impedance curve of the speaker, especially if you have any sort of passive EQ, so you will most likely have to re-adjust any active or passive EQ or add EQ afterwards to rebalance the midrange and treble.
The next thing I would suggest is don't forget baffle step correction... for some reason full range driver fans see baffle step correction (or any equalisation) as anathema, and expect their drivers to somehow bend the laws of physics - they won't.
If you put a full range driver in a free standing bass reflex box and don't apply any baffle step correction the bass will be weak. It's physics. End of debate. With enough listening you can adapt to this and start to delude yourself that the bass response is OK, but it isn't.
So there needs to be some baffle step correction, but getting the amount of correction and the rollover point correct isn't always easy. The correct rollover frequency for the high frequency cut is hard to predict and in my experience room effects mean that the theoretically predicted rollover frequency based on the width of the baffle is seldom right.
I use that as a starting point but I inevitably find I have to lower the rollover frequency significantly below what predictions suggest to get the balance right, and it takes some tuning by ear to nail it exactly.
I have a full 6dB baffle step correction on my Coral drivers, and while theory says the rollover frequency should be about 300Hz based on baffle width I've actually ended up with much larger coils bringing it down to about 200Hz. At 300Hz it just sounded "wooly" due to an excess of low midrange and trying to reduce the total amount of baffle step correction instead just made it sound weak in the bass and wooly at the same time...
With the right box, ports, baffle step correction and a tweak to the Qes using a series resistor the 1772 should still be able to produce surprisingly decent bass down to about 40Hz in a small to medium room, and the 1808 should be able to do even better, without the extra resistor.
I'm looking forward to sampling the W8-1772 when I get the time and money to play around with a pair, however I will be cutting them off below 250Hz. If I was trying to use them for bass as well I would get the W8-1808.
Last edited by DBMandrake; 18th September 2019 at 07:46 PM.
|18th September 2019, 08:13 PM||#613|
I use the 1772 above 250Hz, and front-horn load it, to boot. The horn *lifts* the otherwise anemic lower mid-range level. In this manner, the sound quality is SUPERB,and will only be bested by spending multiples of times more money. I also should mention that after ears and years of enjoying the sound, albeit with a slight "recessed" upper mid-range, I now use a single-ended, class A,
5 watt amp. This has transformed an excellent sound quality into one I would have to rate as sublime p.s. I do use a ribbon tweeter above 8kHz.
Last edited by planet10; 18th September 2019 at 08:29 PM. Reason: Remove excess quote
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