Nothing "wrong" with the TL505 in step down mode, but the port is way too small for the speaker you are considering.
If you extend the shelf (part #7) for a lower tuning and use all three sections of the port it would work OK.
I had a Disco Sucks T-shirt and sported it quite proudly back then. Then I found out sucking was a good thing.
Al.
Al.
If the port is too small, why would you sugest I decrease the size of the port? Is this a test?Or
result of wanting to put that SI HT in there? I can alter the size of the cab. As discused, We both know about the step down option. Please allow me, Art, to step off track here a wee bit. You of all folks know what I desire. Good old 18 kick me in the chest or you remember where the door is. You load me up with all your very cool info, then send me into the dark expecting me to find my way. If you allow me-
Lets sit together on the porch swing.
You want me to suceed so you kick my ankles out from beneath me.
It hurts, so I raise a fist.
Do not think I read through your posts. I am blessed with an incrediible mind that picks up on the tinyest mistakes.
So much for that, right? You make me and I blame it all on you (not a bad thing)
Thanks, Al.
result of wanting to put that SI HT in there? I can alter the size of the cab. As discused, We both know about the step down option. Please allow me, Art, to step off track here a wee bit. You of all folks know what I desire. Good old 18 kick me in the chest or you remember where the door is. You load me up with all your very cool info, then send me into the dark expecting me to find my way. If you allow me-
Lets sit together on the porch swing.
You want me to suceed so you kick my ankles out from beneath me.
It hurts, so I raise a fist.
Do not think I read through your posts. I am blessed with an incrediible mind that picks up on the tinyest mistakes.
So much for that, right? You make me and I blame it all on you (not a bad thing)
Thanks, Al.
Forget smelly socks. As it is Women's Day today, I think we should all work to make our 18" heavy metal sound systems as small as possible.
Al,
I did not suggest you decrease the port size, I suggested using the full port width and lowering tuning (from the standard 45Hz Fb to around 33 Hz) by increasing the port depth. The same tuning can be achieved with a small short port or a large deep port. Large ports do reduce cabinet volume, but in the case of a loose suspension driver liker the SI HT, that is a good thing.
A small short port contains a tiny slug of air that will be blown out like a candle by a high excursion speaker, a big, deep port has a big slug of air that will move back and forth and make satisfying low frequency SPL instead of wind noise.
If that does not make sense to you, think of comparing an 80 cubic inch VW bug (EV15B displacement) exhaust pipe to the ones used on a supercharged 426 hemi (SI HT displacement) dragster. The size difference reflects the displacement, what works fine for small displacement is not adequate for large displacement.
Art
Art,
That does make sense to me now. I knew I would need to do some box tuning for that driver to work right for me. Now I know why! Thank you Sir!
How far should I extend the port shelf (before I hit the back panel)? Would I need to add another shelf above the first (Attached to the back panel)?
Thanks again for the patience and help! Al.
That does make sense to me now. I knew I would need to do some box tuning for that driver to work right for me. Now I know why! Thank you Sir!
How far should I extend the port shelf (before I hit the back panel)? Would I need to add another shelf above the first (Attached to the back panel)?
Thanks again for the patience and help! Al.
I have the TL505 plans here in front of me. The shelf (Part #7 is only 4" long). It is 3 1/2" off the cab floor and extends the 23" width of the cab. Back side of front baffle to rear panel is 18 1/2". This is where the port is devided in three for the step down. All these measurements are internal dimensions.
Outside, the box is 30 1/2" H x 24 1/2" W x 21 1/2" D. I consider this "Womans Day Small" for an 18" heavy metal sub.
Basically same size as a 2' x 2' x2' sealed box, but with more SPL.
If someone can run a program to show me the mods I need to make to this box to work with the SI HT 18 D4, I will go ahead and build one. If the internal volume needs to come down, I can put a 45 degree and some wheels on it. (should anyway). LOL
Got my Phase Linear 700 Series II Service manual plus updates in the mail. Looks like it may be illegal to have in my possession. LOL
Speaker Impedance: Will accept 4 ohm or greater speaker load.
Power output: 360 watts minimum RMS per channel into 8 ohms from 20 Hz to 20K Hz with no more than 0.09% Total Harmonic Distortion.
Continuous Power: 450 watts per channel into 8 ohms @ 1000 Hz; 550 watts per channel into 4 ohms @ 1000 Hz.
Damping Factor: 1000 : 1 @ 1000 Hz.
Quite an array of different output and driver transistors they used over it's short life span. Went from quasi-complimentary output stage to full complimentary out put stage.
Like I know what that means. Sounds very technical and inside cool, though.
Unfortunately, there is no mention of bridging. Where is that confounded bridge? Did they have bridges 35 years ago? LOL
I like these folks that come in here and suggest I buy an amp or a subwoofer that meets my needs. I ride an old kick start Pan Head with no battery. I didn't go to the store and buy it. I built it. From the ground up. And it's still go'n. The lights may dim at the stop signs but you guys that suggest I throw down my cane just really don't have a clue. I like to dig down deep and get that crap under my fingernails that your designer bar soap won't touch.
In your Honor, after listening to the Low Rider 505 for a spell, I will just Have to go ahead and build a baboon stub horn. 18" of course.
First person (male or female) that can help me build this box (505, that is) in lay man's term will be rewarded with the box being named after them> Any thing's better than 'low rider 505'. Sounds like a pair of jeans.
Thanks, Al.
Outside, the box is 30 1/2" H x 24 1/2" W x 21 1/2" D. I consider this "Womans Day Small" for an 18" heavy metal sub.
Basically same size as a 2' x 2' x2' sealed box, but with more SPL.
If someone can run a program to show me the mods I need to make to this box to work with the SI HT 18 D4, I will go ahead and build one. If the internal volume needs to come down, I can put a 45 degree and some wheels on it. (should anyway). LOL
Got my Phase Linear 700 Series II Service manual plus updates in the mail. Looks like it may be illegal to have in my possession. LOL
Speaker Impedance: Will accept 4 ohm or greater speaker load.
Power output: 360 watts minimum RMS per channel into 8 ohms from 20 Hz to 20K Hz with no more than 0.09% Total Harmonic Distortion.
Continuous Power: 450 watts per channel into 8 ohms @ 1000 Hz; 550 watts per channel into 4 ohms @ 1000 Hz.
Damping Factor: 1000 : 1 @ 1000 Hz.
Quite an array of different output and driver transistors they used over it's short life span. Went from quasi-complimentary output stage to full complimentary out put stage.
Like I know what that means. Sounds very technical and inside cool, though.
Unfortunately, there is no mention of bridging. Where is that confounded bridge? Did they have bridges 35 years ago? LOL
I like these folks that come in here and suggest I buy an amp or a subwoofer that meets my needs. I ride an old kick start Pan Head with no battery. I didn't go to the store and buy it. I built it. From the ground up. And it's still go'n. The lights may dim at the stop signs but you guys that suggest I throw down my cane just really don't have a clue. I like to dig down deep and get that crap under my fingernails that your designer bar soap won't touch.
In your Honor, after listening to the Low Rider 505 for a spell, I will just Have to go ahead and build a baboon stub horn. 18" of course.
First person (male or female) that can help me build this box (505, that is) in lay man's term will be rewarded with the box being named after them> Any thing's better than 'low rider 505'. Sounds like a pair of jeans.
Thanks, Al.
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1) The TL505 is about 6 cubes without the port volume. 23"x3.5"=80.5" port area would require about a 25" deep round port to tune around 33Hz. The port would need a right angle bend, and shelf ports don't require quite as much depth as round ports to tune as low, so the length may be more like 20". I could do a check in Hornresp later to see what this alignment looks like on paper, but ...
2)The Phase Linear 700 Series II seems to use lots of current limiting, the older models could put out double the power at 4 ohms as 8. The SI HT 18 will have an impedance minima near 3.5 ohms, so forget about bridging the amp, it would see that load as under 2 ohms. There is probably no mention of bridging because it was not designed with bridging in mind. Though it could be bridged at 8 ohms and do around 1100 watts (I explained how to do that to you in a PM), back when it was made there were no speakers that could safely handle that power. Still, 550WPC continuous at 4ohms 1kHz is a lot, I would bet the peak output to be more, even at low frequencies.
Damping factor (the ability to start and stop the driver without overshoot "slop") is good, but speaker wire always reduces the huge DF to much lower figures. Use 12 or 10 AWG and DF is fine for 35-25 foot runs.
Art
Hi Art,
The SI HT 18" D4 is a 4ohm dvc version that I can wire in series for 8 ohm.
So the TL505 shelf port needs to be 20" long for 32 Hz box tuning? SI recommends a 5~6 cu. ft. ported box tuned to 20 Hz, if that helps.
I found this gizmo that may address my summing and bridging concerns. Looks like I patch it in with +output to channel A input.
-output to channel B input.
Speaker + goes to amp channel A +output, - to channel B +output, negs not used.
This assumes a 180* phase shift on the gizmo's output. I have no specs or "user manual" for this.
Thanks, Al.
The SI HT 18" D4 is a 4ohm dvc version that I can wire in series for 8 ohm.
So the TL505 shelf port needs to be 20" long for 32 Hz box tuning? SI recommends a 5~6 cu. ft. ported box tuned to 20 Hz, if that helps.
I found this gizmo that may address my summing and bridging concerns. Looks like I patch it in with +output to channel A input.
-output to channel B input.
Speaker + goes to amp channel A +output, - to channel B +output, negs not used.
This assumes a 180* phase shift on the gizmo's output. I have no specs or "user manual" for this.
Thanks, Al.
Attachments
Also, I read amp bridging requires common ground? The PL has a coupling switch, normal or direct. What's this all about and are they related?
Thank's Al.
Thank's Al.
Al,
The gizmo does a polarity reverse (not a "phase shift"), same as swapping + and -, but probably isolates/floats the chassis ground, which is why it needs power to do it's thing.
The " - " speaker outputs are often the same as chassis grounds and directly connected to each other, you can verify that with an ohm meter, if they are common they will all read near 0 ohms resistance between points. The PL schematic would also confirm this. The normal or direct switch, IIRC, "normally" inserts a HP filter, "direct" allows the amp to amplify down to DC, good for tearing up loose cones or operating shaker tables 😉.
Some amplifiers are already "bridged", the speaker " - " are also hot, isolated from the chassis, and hooking them together will result in amplifier shut down or smoke 😱.
Some discussion about port types:
Round port to shelf port conversion? - TalkBass Forums
And a port calculator:
Port Length Calculator
The port calculator does not tell you what vent velocity will be. Too high of vent velocity, and the port gets "blown out", it will make chuffing noise and loose LF output. Keeping vent velocity below 15 meters per second (or so) will result in a port that works well but is not overly huge.
You probably can get by with around 50 square inches of port area. Some examples below. I always like to make ports a bit long, and verify tuning with a sine wave sweep. The cone movement will be at minima at Fb, if Fb turns out too low, chop off some port.
Remember Hoffman's Iron Law: Low, Loud or Small, pick two, lower tunings won't be as loud.
Art
Attachments
A good teacher knows the student learns best by applying the insight given.
The 20Hz tuning of a box that small is absured.
The long port with it's larger volume will reduce velocity. Bernouli's Law.
The gizmo outputs a polarity swap, you say. I thought I needed a mirror image phase shift to walk the bridge.
I can not figure out if the gizmo will work.
I will now go look over your links, thank you very much.
Thanks, Al.
The 20Hz tuning of a box that small is absured.
The long port with it's larger volume will reduce velocity. Bernouli's Law.
The gizmo outputs a polarity swap, you say. I thought I needed a mirror image phase shift to walk the bridge.
I can not figure out if the gizmo will work.
I will now go look over your links, thank you very much.
Thanks, Al.
I summed the three port areas and devided by three and entered this as three ports on your port calculator. That did not turn out too well. LOL
Al.
Al.
Al,
Not my port calculator, though I did give the link.
Using the 33Fb "step down mode", the calculator pukes out a 7.72 length port compared to the 505's stated 4 inch depth.
Probably a depth somewhere between the two is the real Fb. As I mentioned, I always like to make ports a bit long, and verify tuning with a sine wave sweep. The cone movement will be at minima at Fb, if Fb turns out too low, chop off some port. Easier than adding length.
A 180 degree "mirror image phase shift" over all frequencies results from a polarity swap. However, loudspeakers have a different phase response that varies with frequency.The phase inversion in bass reflex cabinets occurs over a limited bandwidth. Since you seem to be inquiring about both, thought making a semantic distinction useful
.As far as your statement "The 20Hz tuning of a box that small is absured", I find it funny that you would presume the manufacturer of the speaker you decided to use would not know what works well for their driver.
Art
Semantic distinction perhaps is the monkey that reaches through the the cage and grasps the banana. The retrieval can not be realized without dropping of the banana.
So gizmo caught the banana before it hit the floor and offered it to me?
Now that you mention it, my presumption and assumption may define me.
The box alignment defines the phase response/inversion? Who knew sub woofers could be so technical? Jeeze!
Sometimes a young man may like to design and have built to his specs in China some speakers. His advisor's may not be on line with his desires. It takes a lot of man to cover all aspects. Perhaps man spread thin. Cozy part is this guy is approachable on a first name basis. I don't find this funny. But I will bring this up for his benifit next time we chat.
So gizmo caught the banana before it hit the floor and offered it to me?
Now that you mention it, my presumption and assumption may define me.
The box alignment defines the phase response/inversion? Who knew sub woofers could be so technical? Jeeze!
Sometimes a young man may like to design and have built to his specs in China some speakers. His advisor's may not be on line with his desires. It takes a lot of man to cover all aspects. Perhaps man spread thin. Cozy part is this guy is approachable on a first name basis. I don't find this funny. But I will bring this up for his benifit next time we chat.
If you don't want to end up with an expensive pile of steaming
it does take a bit of technical work.
If you don't mind stepping in it and tracking it all around the house, the barriers to entry in "sub" land are few 🙂.
Sub land comes with all the trimmings. Follows you in the house, scares the fish away at your favorite hole, not to mention your favorite hole, the rap guy next door, the rap guy two blocks down (that's when I will be arrested). The import guy with his panels flapping and supporting Exide for all the new 12v batteries. The pretty birds that fly away. The stupid birds that stay behind and eat the fruits of your garden.
I could go on and bore you the rest of your life.
I have the groceries, just need the recipe.
Help me please, Al.
I could go on and bore you the rest of your life.
I have the groceries, just need the recipe.
Help me please, Al.
No one ends up with an expensive pile of clams (we purge them) wrap the big scallops in bacon, no over cooked lobster and no well done steak. Chicken and ribs for the servants (that's where I hang out). Diced potatoe 50/50 with onion. Summer squash, Gramma Brown's and KFC cole slaw.
Al.
Al.
I gotta say, whats left of my brain is becoming numb over this sub woofer.
I want to drive one 18" sub woofer mono with a bridged Phase Linear 700 Series II.
Do not try and talk me out of this.
I will do this with or without your help.
I admire feed back when it is on my track.
The help me vs. talk me out of it ratio.
Sign up for contributions.
Thanks, Al.
I want to drive one 18" sub woofer mono with a bridged Phase Linear 700 Series II.
Do not try and talk me out of this.
I will do this with or without your help.
I admire feed back when it is on my track.
The help me vs. talk me out of it ratio.
Sign up for contributions.
Thanks, Al.
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