Dustin B

It's not hard to make a sub play extremely loudly at 31.5hz. It's the last octave that is the tough one. And do you have any idea what the THD numbers on the Sunfire are at high output levels at 31.5hz and 20hz? And no responses to my other questions above? This message has been edited by Dustin B on 08-15-2002 at 11:26 PM

Oh, hmm. Will hurt the pocket book a little but you should maybe be looking at the HS series of amps from Adire. You have to remember that these less expensive plate amps (and amps on commercial subs, except for the likes of Rel and Aeriel) don't have a great crossover on the amp. If you use speaker level connections the high pass is usually fixed around 120hz while the lowpass is variable from 40-160hz. You can't have a variable highpass filter that works at the speaker level (so they use a fixed one). The reason the lowpass can still be variable is the speaker level signal is converted back to line level, feed through the filter and then amplified again by the plate amp. Even the Rel/Aeriel/HS series amps from Adire don't have a variable HP filter for the speaker level connections. But unlike the AVA250 and other cheaper plate amps they do have a variable HP for the line level (the others are still fixed at ~120hz). If you can loop line level connections (left and right main speakers) back to your receiver (not sure if this is possible) then the HS series will give you a true 4th order linkwitz riley crossover that will be far superior to the AVA250 or PE300-794. If you can't loop line level connections back to your receiver this post can be ignored. The other option is to parallel the sub and main speaker connections. Then adjust the variable low pass so it matches up with the roll off of the mains. Tricky to do and doesn't always work that well. This message has been edited by Dustin B on 08-15-2002 at 02:43 PM

The PE 300-794 is essentially the same amp as the AVA250. With two exceptions. The AVA250 now has an extra input that completely bypasses the plate amps crossover. The AVA250 also comes with the rumble filter set to provide a 1dB boost at 25hz and a corner frequency at 18hz for the HP filter. The PE 300-794 I believe currently comes with the rumble filter disabled. But it only requires the swapping out of 2 resistors to change the rumble filter to whatever you want. I'd recommend 1dB boost at 25hz with a 17hz HP filter corner frequency (if you can't swap out the resistors then the AVA250 ends up looking more appealing). The remote amp is a waste to me. Once you calibrate the sub properly you will only be making minor adjustments to its' level which can be done through the receiver. Have you ordered the Tempest? Where are you ordering it from? If you are going through a place that gets both (Adire and PE dealer) it hurts them a bit to get stuff from PE and Adire. Just like if you order yourself from PE and Adire then you get dinged twice for shipping. That's the info I can give on the subject, you'll have to make the call from there.

I'd recommend some polyurethane glue (bulldog grip). to glue the end caps in. When it dries it expands a bit to fill in any gaps. I used several small finishing nails to hold the endcaps in place while the glue dried. Then silicon the inside edge where the endcaps meet the tube. This is kinda tricky and uncomfortable though. So another option that should work is measure how far into the tube the endcaps will go and draw a line there. Then run a thick bead of silicone on that line. When you put the endcap in (with glue on it) it will push into the silicon. Between the glue and the silicon you should have a good seal.

Well above 30hz two RSW15s would be capable of essentially the same output as a pair of SVS Ultras. It's just in the last octave they can't keep up. And if you don't like the big tube look (although I think the SVS tubes are small and like the tube look, my Tempest stands 6' tall and 19" in diameter ), well then the RSW has a decided advantage to you. My only other hang up on the RSW series is I highly doubt the passive radiator has twice the excursion of the active 15" driver (and therefore twice the displacement ability) which could lead so some problems at high output around tuning. The rule of thumb is you want the passive radiators to have at least twice the displacement ability of the active drivers.

So how did they get around port compression and noise at high output? You can only pump so much air through a 4" flared port. And with a 22hz tune things would get a little dicy down around 16hz at high output levels. If you have access to the Rel Studio could you tell me how long and wide the port is? From the pictures I'm guessing it is a 6" port, which means given the Studio's dimensions, it will be tuned somewhere just under 30hz. That will hurt 20hz output big time.

I see you mention the Aeriel SW12 as king of the hill no question. Is this in output as well as sound quality or just sound quality?

Sorry if I was unclear. By stacking 2 subs I meant stacking a second identical sub ontop of the original (or placing them as close as possible together) will gain you 6dB of output over the original. If you put them in different places in the room you likely won't get anywhere near a 6dB gain (plus you will likely get some nasty constructive and destructive interaction between the two). You get 3dB for doubling the cone area and 3dB for doubling the amp power. To get a 6dB gain again, you need to double the current cone area again and double the current amp power again. So you need to go from 2 to 4 subs for another 6dB gain. You won't get a 6dB gain for every sub you add. So going from 1 to 4 RWS15 subs gets you another 12dB at 20hz. To add another 6dB would take 8 of them, so going to 6 should get you the last 3dB needed to match a pair of Ultras at 20hz. And this all assumes you can get that many subs to couple perfectly. If they don't couple perfectly you won't get the full 6dB for each doubling of cone area and amp power. This message has been edited by Dustin B on 08-14-2002 at 11:10 AM

For placement you made the right call. Have you got an EQ yet? That should be your next priority to even out any room induced peaks. As for your last question I'd get the new drivers and enquire to SVS about getting a longer port for the 25-31 to retune it to 22hz.

Well I more or less throw those terms out to keep people happy (I don't use them when in DIY forums as they aren't needed there, we trust physics there, as opposed to audiophile hyperbole). I'm more in the camp of Jack Gilvey et al. If the sub uses a good quality woofer, plays low, clean (low THD) and flat (good frequency response), with enough enclosure volume and/or low enough tune to get the Q of the enclosure to a nice level (0.5 to the mid 0.6 range) then the room is many multiples more important to how the sub will sound then the sub. There are very few commercial subs that meet those requirements though. There are many DIY designs that do though. The so called musical subs usually meet the above criteria except they are either gutless or lack last octave performance. The so called HT subs don't have the above but go boom quite well. In my opinion though, if a sub doesn't do both well, it's not a good sub. This message has been edited by Dustin B on 08-14-2002 at 11:58 PM

That guess was based on a 6dB increase from stacking two subs. And the 14-15dB difference from the Secrets of HiFi review between the RSW15 and Dual Ultras at 20hz (95-96 vs 110). 2 would get you to 101-102, 4 would get you to 107-108. Actually now that I think of it, you'd have to add 2 more not 1 more to get 3 more dB which means it would take 6 RSW15s to get you to 110-111dB in that test room (3500ft^3 something like 18feet from the subs).

They list for $1900, but are selling for $1300-$1500.

theEARs, I think you'd be surprised just how good these oil barrel sonotubes slapped together in a garage sound. They do a lot more than just go loud (and how good they look depends entirely on how much time and effort you put into the finish, I've seen pics of some that look better than any commercial sub I've seen). With a small amount of research they are really quite hard to screw up too. Anyways there is a big difference between a push pull and an isobaric sub. Push pull has the drivers sharing the same internal box space in opposite orientation wired out of phase (so although they are in opposite orientation the both push out of the box and both pull into the box at the same time). It's supposed to cancel some distortion but in the real world that reduction in distrotion is pretty meanless as there are other sources of distortion that grossly out weigh what the push pull design fixes. A push pull won't go any lower or louder than the same drivers in a non push pull config. An isobaric traps some air between the drivers. Then one driver is open into the box and the other driver is open out of the box. The only thing this really gains you is a halving of Vas. It will essentially act as one driver (actually not even quite as good as one driver as you loose some efficiency too). So if a small box isn't a major concern, don't do an isobaric. You're just wasting money. If you are game on building the enclosure yourself and you want fast low tight and musical I would highly recommend the Adire Maelstrom in a low Q sealed allignment. It also won't require a lot of power, 250W will be oodles and will need to be in a farily large enclosure. The Adire Tumult will also be out in a month or two. That sub in a low Q sealed allignment with a linkwitz transform chip and over a killowatt of power will be incredible for both output and sound quality. This sub will be able to be a lot smaller than a Maelstrom needs for low Q, but require a lot more power. In larger passive radiator enclosures it will be down right scary. This message has been edited by Dustin B on 08-14-2002 at 11:53 PM

theEARS, I'm curious. How many subs have you owned and what were they?

Do a search on HTF in the Advanced DIY section. Many people have built it, and many people have been very impressed with it. If WAF is a bit of problem take a look at what this guy did (by the way it's a 214L vented Tempest). I've built a Dayton DVC12" equivalent for a friend and my parents. An EBS Shiva won't disappoint. This message has been edited by Dustin B on 08-13-2002 at 11:40 PM

You're forgetting about a little thing called Hoffman's Iron law. Out of enclosure size, efficiency and extension you can pick any two and the third will be dicated to you. It will take more than two RSW15 subs to match a pair of SVS Ultras in the last octave. The TV12 has a long enough throw to get its' Vd up in to the realm of most 15" drivers. And the larger enclosure means it doesn't sacrifice as much extension. My guess is it would take about 5 RSW15 subs to match a pair of Ultras at 20hz.

Well, it will be a few years before I can start playing like that (if ever) as I have no intention of making a career out of building subs. HT is just a hobby for me. Would you at least mention what these different tweaks I'd have to experiment with would be? I'm gonna make a career out of programming, I was hopeful you'd share some of your knowledge with a hobbiest though. As I have time for the keyboard, but not the time or money to do my own testing at this time.

You've made these car comparisons many times Tom. But cars and subs are different. I understand why a smaller engine in a vette could take a larger engine in a caddy. Weight, tires, suspension, turbos (gotta love the 1987 Honda F1 engine, over 1000hp from a 1.5L V6; twin 58psi turbos!!) etc. Another good example would be the SCCA T1 class. Mustang vs NSX. The Mustang is heavier, has a lot more power, can accelerate faster and can go faster in a straight line than the NSX. But the NSX is lighter, can wait longer to brake into corners and can take those corners at a higher speed (plus Cunnigham is a kick *** driver). End result the NSX wins a lot of races. I'd like to learn what these sublties in a sub are. Changing specs as you approach max excursion as described in the XBL^2 paper? Port compression (but the large enclosures a Tempest requires are easier to port addequitly)? Does the small distance between driver and base plate on the SVS subs do something neat? Something else my intermediate knowledge level hasn't even seen yet? This message has been edited by Dustin B on 08-03-2002 at 11:25 AM

Damn Manuel for pointing me to this thread. The Tempest has an Sd of 779cm^2. It has a linear p-p Xmax of 32.8mm. Which gives a linear Vd of 2.55L. The Brahma 12" has an Sd 436cm^2 and a linear p-p Xmax of 54.6mm. Which gives a linear Vd of 2.38L. Now even if the TV12 driver has an Sd of 475cm^2 it will take 53.8mm of p-p Xmax to match a Tempest. And with the surround required for that excursion I highly doubt the Sd of the TV12 is that high. So it will more than likely take in excess of 60mm p-p Xmax to start passing a Tempest Vd wise. Are you saying a TV12 being a smaller motor has enough Xmax to have more than 2.55L of Vd Tom (any 12" driver that can move that much air is freakn impressive though)? Is linear Vd not the biggest factor of SPL at a particular THD level down in the last octave (assuming a appropriately sized, properly tuned and sufficiently ported enclosure)? The biggest problem Dan is having now with his new XBL^2 topology is finding a surround that will stay linear with the extreme linear excursion an XBL^2 motor is capable of. Dan has stated he could go out to >60mm one way Xmax with XBL^2 if he could find a surround that could do it. There have been serveral reports from shows where XBL^2 was demonstrated. Two drivers, one with, one without. The difference in the sound between the two was reported as very obvious. In a month or two Adire will be releasing a new 15" driver with XBL^2 that will have over 5L of Vd and other specs much more appropriate for home use (unlike the Brahma series). Price on this driver will hopefully be in the $300USD range. Problem is it is impossible to port it properly in a suitable enclosure size, so you'll have to add another $200 for a pair of 18" PRs (barely enought) and another small chunk for a kilowatt of power to get it to it's limits. I suggest you give this link a read theEARs, especially the pdf files linked to at the bottom of the page this link leads too. http://www.adireaudio.com/tech_papers/xbl2_motors.htm This message has been edited by Dustin B on 08-03-2002 at 02:10 AM