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Lab15 4-ohm sub idea check

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  • isaeagle4031
    replied
    It was tsken at the terminals, but the connection probably wasnt the greatest. Based on the "feel" test, these cabinets are not resonating any significant amount. My calibration could have been off a bit. At any rate, it shows that the tuning is as my model said it would be and the FR confirms it.
    They play low, loud, and clean. Ive talked with Eminence about these and hope they make them into a production model.

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  • Brian Steele
    replied
    Originally posted by isaeagle4031 View Post
    That is in place and i would contribute the ripples more to wire and connection at the time. The walls ""appear" thick but its actually more of a trim piece. The baffle is inset 1" with bracing behind it.
    ​Ah, the impedance test wasn't done at the box's terminals then? That could explain the ripples, though I might be tempted to confirm that by having someone heavy sit on the box and repeat the measurement . If the ripples reduce significantly or disappear entirely, then they're caused by panel flex.

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  • isaeagle4031
    replied
    That is in place and i would contribute the ripples more to wire and connection at the time. The walls ""appear" thick but its actually more of a trim piece. The baffle is inset 1" with bracing behind it.

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  • Brian Steele
    replied
    Originally posted by isaeagle4031 View Post
    Here is my version of using the lab15-4s. 4cu net, port is 2.25x15.75, 24 long. Enclosures are 3/4" acx ply.

    Measurements are taken in place. Not spl accurate. Taken at anout 1.5m. Hp 24db at 28, lp 48db at 90. Power is supplied by a Crown drive series amp at 750w ea and fed from a dbx driverack. No eq is used.

    These are in a church , 40ft wide, and 70ft deep. Located about 4ft from the side wall and 10ft from the back wall. Ive used them for a few movies and youth group events. To say the slam is an understatement.
    ​Nice to see someone actually pose an impedance plot for a built system. .

    ​Was the impedance test done with the subwoofers in their intended location? The ripples that start from the top of the second impedance peak suggest some sort of strange loading, or it could be that the box panels may require a little more bracing to be "perfect", though that would be interesting considering that it looks like you've doubled-up on the side walls. Those are some pretty nice-looking boxes! Looks like a big-*** version of my Blastoramas

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  • isaeagle4031
    replied
    Here is my version of using the lab15-4s. 4cu net, port is 2.25x15.75, 24 long. Enclosures are 3/4" acx ply.

    Measurements are taken in place. Not spl accurate. Taken at anout 1.5m. Hp 24db at 28, lp 48db at 90. Power is supplied by a Crown drive series amp at 750w ea and fed from a dbx driverack. No eq is used.

    These are in a church , 40ft wide, and 70ft deep. Located about 4ft from the side wall and 10ft from the back wall. Ive used them for a few movies and youth group events. To say the slam is an understatement.

    Leave a comment:


  • make_some_noise
    replied
    With the specs you listed, it simmed ok for me @ 500 watts before any boost. Adding a bunch of boost down low magnifies the amount of excursion needed by quite a bit.... IIRC when I was playing with that yesterday, in 3.5 cu ft sealed....The alignment was -16db down at 20hz. At 500 watts RMS the driver starts to exceed xmax at approximately 26hz. Adding 12db of boost in the mid 20's is going to push the xmax into 50 mm territory, which is self destruction... Did you factor the boost into your sim?

    I'll be honest, and this is coming from someone who loves big EBS alignments and a strong low end... Going close to flat on paper to 20hz can be way too strong depending on the room. Most commercial home audio subs are built to use room gain to achieve the lower octaves in order to have better power handling and free SPL higher up the band.

    There is another thread going on right now about room gain and I have to agree with some of the posters that room gain happens in a leaky room. I have a 13x17" room, with an open door way into the rest of the house and I still get a lot of room gain down low since the room is shorter than 20hz is long. Sometimes you just have to make some sawdust and build a prototype since you can only estimate room gain. On the flip side if the build is too strong down low, you can always pull out some EQ and gain some headroom back. I would bet dollars to donuts that if you put those drivers in cabinets tuned to be strong down to 40 on paper with a very usable F3 in the 30's... Once you put them in most average rooms they will pound you pretty good at 20hz. Not many people can hear 20hz.... but they feel it.

    I think 3.5 cu ft with a tuning of 34 hz would be a good compromise, 500 watts still gives 101 db @ 20hz. It would be awesome and clean for music while still strong for HT. My "small" 15" sub is a very similar tuning and it is strong in movies. Enough to crack a window and plaster walls at a few hundred watts. I only turn on my supplemental EBS sub when I want some super deep shake at low volume, or when I feel the need to make my neighbors angry at high volume :p.

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  • matt996
    replied
    Thanks for the replies. I've seen that "Constricted Transflex" design and it sounds like it does well for its intended use. Doesn't really go low enough for HT though.

    Originally posted by make_some_noise
    They look really good in 7.5 cu ft tuned @ 25hz... Too bad that is probably twice the size you are looking for. Sealed in 3.5 cubes and a ton of boost looks good curve wise, but the driver just doesn't have the xmax to handle anywhere close to 500 watts in this configuration.. I take it that you cannot build the cabinets in a taller, more tower shaped config in order to gain the additional volume?
    Yeah 7.5 cu ft would be a bit much. Curious about your comment on not handling 500 W as my sim showed it stayed within xmax in that box and power level, unless I'm doing something wrong.

    Thanks for the other ideas - I don't think I could justify buying more drivers for isobaric at this point, as my output requirements are modest and I did want separate subs to help with the room modes. Plus I haven't seen the cheap Lab15's for a while...

    One thing I liked about the LT is that I can just dial up different f3 and Q to find something that works best for the room. It has two large open doorways to the rest of the house, so I'm not sure how the room gain is going to look until I try it. Sent from my SM-N900W8 using Tapatalk

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  • make_some_noise
    replied
    They look really good in 7.5 cu ft tuned @ 25hz... Too bad that is probably twice the size you are looking for. Sealed in 3.5 cubes and a ton of boost looks good curve wise, but the driver just doesn't have the xmax to handle anywhere close to 500 watts in this configuration.. I take it that you cannot build the cabinets in a taller, more tower shaped config in order to gain the additional volume?

    At the same time if you put both of those drivers in an isobaric pair in 4 cu ft tuned to 22hz and hit them with 1000 watts they will stay within xmax down to 20 hz and put out 113db 20hz before any room gain. Unless you have a mansion sized family room, it should make stuff move across the tops of tables etc....

    If you want two physical subwoofers in order to try and neutralize some of the room modes... I wouldn't mess with PR's because a box that small may still need a lot boost for the result you want and you'll still run out of excursion.. Not to mention you'd need two very long throw 15" pr's in each box and that is a good chunk of change.... Enough money that you might as well try to find two more lab 15/4's on ebay and build a 2nd isobaric cabinet. Or you could sell the lab15/4's you have and invest in an 18" ultimax or a pair of 12-15" ultimax's and call it a day (these drivers are meant for small sealed cabinets with a lot of boost).

    Keep in mind if it's flat to near 20hz on paper, depending on the room it may be much stronger down low, and a smaller ported cabinet may perform well and measure well in room, ala the posts above.

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  • Beau
    replied
    Thank you.

    There is also a 3.5 ft^3 slot port design for this driver on the AVS Forum (thread called "Lab15 4ohm (ebay) build 3.5cube 33hz") in the DIY Speakers and Subs subforum.

    Leave a comment:


  • isaeagle4031
    replied
    Originally posted by Beau View Post

    Should I assume the 4 ft^3 enclosure is ported and tuned to 27 hz, or is it sealed (and I am thinking too much)?

    Also, there is a very lengthy discussion about this driver on the DIYAudio forum. It is a ported design that is effective between 35 hz and (IIRC) 150 hz.
    Yes ported. I used a slot port that is IIRC 24"L with a surface area of about 27in. The details are on my Facebook page in my sig. The measured in room response has them flat from 26hz to 80 where they hand off to a pair of powered mains. Power is from a Crown amp, 750w ea. No other processing via a dbx driverack+.

    Leave a comment:


  • Beau
    replied
    Originally posted by isaeagle4031 View Post
    I used these in a 4 cu ft enclosure with an fb of 27hz. Fantastic!
    Should I assume the 4 ft^3 enclosure is ported and tuned to 27 hz, or is it sealed (and I am thinking too much)?

    Also, there is a very lengthy discussion about this driver on the DIYAudio forum (thread is called "New sub design? Constricted Transflex, simple build (series tuned 6th order"). It is a ported design that is effective between 35 hz and (IIRC) 150 hz. There have been several variations, but the fist design was solidified in post 552.

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  • isaeagle4031
    replied
    I used these in a 4 cu ft enclosure with an fb of 27hz. Fantastic!

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  • matt996
    replied
    Also - probably helps to include the driver specs: fs 34.4 Hz; Re 3.75 ohms; Le 1.60 mH; Vas 93.3 L; Qes 0.59; Qms 3.76; Sd 823.7 cm^2; xmax 13.02 mm Sent from my SM-N900W8 using Tapatalk

    Leave a comment:


  • matt996
    started a topic Lab15 4-ohm sub idea check

    Lab15 4-ohm sub idea check

    I have a pair of the 4-ohm Lab15 destined for my family room HT. As some may recall, the specs on these are quite a bit different from the normal Lab15. Fs and qts are quite a bit higher. The 21 Hz ported box that works quite nicely with the normal Lab15 does not simulate well at all for the 4-ohm version.

    My tentative design is to do undersized, sealed boxes (~3.6 cu. ft., net) and apply the Linkwitz Transform with target f3 = 20 Hz and Q = 0.5 (yes, a ton of boost). WBCD simulates the driver at or below xmax at all freqs with 500W for this box volume. Output is about 100 dB at 20 Hz for each sub.

    This driver didn't really lend itself toward a ported box for an HT tune (let's say 20 Hz) in practical dimensions.

    I'm willing to consider using PRs, and boost/processing if necessary ... but I wasn't confident enough in playing with the additional variables for a PR design. I'm intrigued by something along the lines of the "Baby Boomer" sub except using the Lab15-4s and suitably larger PRs.

    Available processing is a miniDSP 2x4 balanced, and power is a Crown XLS1500. Usage is mixed HT and music, and useful response to 20Hz is desired. I can go up to about 4.5 cu. ft. net on the boxes if necessary, but of course smaller is preferred for SAF.

    If anyone has other ideas, I would love to hear them!
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