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Looking for a linear subwoofer that can still take some power?

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Woldemort
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Hi

Now these are going in my car, but I don't really think that matters that much.

I want 2x15s that play low, e.g. tuned to 25Hz in a ported enclosure, with good sound quality.

And they have to be "able" to play loud e.g. handle the power.

I have 8kW for them, that doesn't mean they have to be 4kW rms.

I was almost already set on the SI SQL15s, but they don't ship to Finland and the shipping costs and taxes would be something else.

Now these are 1000W rms, but I have heard of people running them on 8-10kW daily and Sundown unofficial put 24kW into two subs if I remember correctly. This is what I mean by be "able" to handle the power.

The thing with the SQLs is the amount of Xmax, linearity and still some good efficiency. I haven't been able to find this in any other subs so far, in this price range.

The CSS SDX12 seems to be a similar sub, but they don't make 15s and they are more expensive.

The new Dayton MX15-22 seems to play almost exactly the same as the SQL 15s. Only that they have less Xmax and a lot smaller voice coil, which I don't think could handle the power. And they are also American, they are available here, but for about 340$ instead.

Has anyone tried or is willing to try the Ground Zero GZRW 38-D2?

I can't find much information about it or any reviews. Someone local said he built a wall for them in a car and put like 5kWrms per sub and they handled it well.

They are rather cheap here, have an Xmax between the SQL and MX, have the biggest voice coil and most importantly they are available locally with free shipping. Ground Zero make some really good quality subwoofers, I just don't know if this is one of them. It is optimized using the Klippel program, but they don't show any graphs like the SQL does. In WinISD it plays similarly to the other subs, but lacks the mid-bass sensitivity. But for the price it would be okay, and the bigger voice coil could make up for that in power compression.


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123Toid
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@woldemort There is quite a few that you could use.  But I would contact Punktkilde and see if they could sell you some of their new 15's.  I've modeled these a few times, and they can dig low, get loud and handle a lot of power. The only issue I see, is that they are 8ohm. But the thing has a 6" voice coil.  Just crazy.  Meaning you would need to wire them in parallel just for a 4ohm load. They were going to send me one, but in the end, it ended up not happening. So I haven't personally heard them, but it could be an option. 

 

Another new option on the market could be Power Hogg audio Hogg 3.  They have three different 15's. Their highest end should easily get you the power handling.  However, they don't specify xmax and I am not sure on the low end.  I haven't modeled it.  It has an FS of 30hz, so it is possible you could tune it to 25, but you would want to check it in WinISD or whatever you use to model your boxes. 

 

On a side note, CSS used to sell a 15" - the SDX15.  Maybe you could contact Kerry or Dan and see if they have some old stock. 

 

 

https://www.youtube.com/123toid


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Woldemort
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@123toid The power Hogg 3 15 looks good, but it very inefficient and rather pricey.

I am very interested in the new Punktkilde products. The 15 looks good on paper also, but I didn't find if they have single or dual coils. I have a 2 ohm amplifier, so if they have dual 4 Ohm coils, 2 of them would get me to 1 Ohm. With box rise this could be usable. With dual 8 Ohm coils I would get 2 Ohms. Single 8 Ohm coils gets me 4 Ohms, which is halving my power. 

The 15 also looks very inefficient compared to the SQL15 everywhere else, but the peak. Probably because of the big heavy voice coil.

The SDX15 looks promising. I modeled 2 of them in 250l and it looks like they would need just a little more to comfortably tune to 25Hz, but it is close enough. The sensitivity is best in class from all the subwoofers I have modeled in WinISD. Only thing is I can't find the power handling or the size of the coil, but 🙃 

But I doubt I could get my hands on 2 of them for a reasonable price. I saw on some forum though that they are working on a newer model of the SDX15 with new basket, revised moving parts and the SDX12 motor. They got 30mm of xmax from the preliminary Klippel tests. They sai these could be pre-ordered in 2021, so maybe soon...


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123Toid
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@woldemort

It does appear that the Stereo Integrity is more sensitive, but it isn't.  They are actually cheating or misleading you with advertising for their sensitivity. Notice that it states it is taken at 2.83v at 1 ohm. Typically sensitivity for an 8ohm woofer is taken at 2.83v (or 1 watt), when a 4ohm speaker gives it's sensitivity @2.83v, it will actually give it  closer to 2 watts, giving it an artificial 3 more db of sensitivity (only because it is receiving more wattage). So when they state sensitivity at 1 ohm, they are actually giving the speaker 8 watts of power.  This is why all speakers should be giving a sensitivity rating at 1 watt.  That is it's true sensitivity. So the SQL by Stereo Integrity's true sensitivity is about 10db less (85db).  Which is almost identical to the Punktkilde and lower than any of the Power Hogg products (however, they do not state how they derived their sensitivity - so that may not be true).  

https://www.youtube.com/123toid


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123Toid
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@woldemort

I would ask CSS about the 15's.  I know COVID has really messed up a lot of new drivers coming out, but it is worth checking with them.  Both Dan and Kerry are really nice and would be more than happy to let you know if it is still coming. And, the CSS SDX12 is probably the best sounding sub I have heard.  I really love it. 

https://www.youtube.com/123toid


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Woldemort
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@123toid

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 Yeah I noticed that with 1W and 2,83V some time ago when comparing products. Don't look at those anymore because frequency also changes it alot.

I modeled them in WinISD and that is how I got my "sensitivity measurements".

I linked some pics of 2x15s at 8kw in 250l tuned to 25Hz.

The old SDX15 was the only one to exceed the SQLs in sensitivity. The Punktkilde was there at the peak, but not for the rest...

CSS has put some info on Instagram stating a starting MSRP of 499$, which is a little steep compared to the 349$ of the SQLs, especially when buying two. If I could get my hands on some old SDX15s for a little cheaper, that would be nice. They seem to use the same baskets as Alpine Type R uses as well. I would have went for Type Rs, but they don't have the Xmax.


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123Toid
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@woldemort

Got it.  looks liek we were using different terminology.  You are looking for max output (SPL) not the sensitivity.  Most people when they refer to efficieny of a speaker, they mean sensitivity which is what I assumed.  I am sure you are probably already doing this, but for anyone esle that might be reading this.  When checking for max spl, you should check both the max spl and the max power graphs in winISD.  That will tell you if you will have any mechanical limits that might limit your output.  THe normal SPL graph won't do that without telling it to. 

https://www.youtube.com/123toid


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Woldemort
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@123toid Yeah there I have modeled a rough max SPL.

But I do separately look at cone excursion and Le changes to compare also.

But I think WinISD shows the sensitivity the best, as if I put the same power on two subs, WinISD will show which is more sensitive.

Because I won't do much with a number like 87dB for the sub, when my tweeters are 110dB sensitive. It seems much better to compare sensitivity with their corresponding power levels when building a system.

And it makes sense that the lighter cone subs are more sensitive, so those comparisons must have some truth to them. Also different subs will react differently to the same box, which will affect SPL.


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Mistersota
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Making enclosures for cars is a completely different ball game than in a home theater thanks to cabin gain. This is a 10-12db/octave rise starting at the frequency that is 2x the length of the cabin (most are around 60hz). So in order to design a proper enclosure for a car, you MUST add a linkwitz filter when looking at the response. If you don't, you will get a huge peak in response around your port tuning. Generally, due to this cabin gain, you will need to make the enclosure smaller and tuned higher, which are good things. You also need to simulate the voice coil inductance. This is because subwoofers tend to have a high inductance which can dramatically change the response. Some don't, but almost all with high excursion and power handling do. Here is an example with the MX15 you mentioned, and I own.

 First, here is the difference in response by simply simulating the inductance. the box size and tuning is exactly the same, but the one with the hump is with inductance simulated. Don't worry, it's actually not a problem in the end.

mx15 inductance change

 Now let's look at the linkwitz transform. To add a 12db/octave rise at the frequency you want to put a filter with these values. f0 is the starting frequency that depends on your vehicle. I'll use 60hz because it's fairly standard.

linkwitz transform

 Here is what that filter looks like when applied to the mx15. As you can see there is a 20dB peak at the tuning frequency due to that cabin gain, which is not what we want to see.

linkwitz on mx15

 To combat this you have to tune higher and make the box smaller. This graph shows the difference between the recommended box that would work well for something like a home theater and what would work well in a car. The one with the peak is a 155 liter box and the flattened one is 64 liters.

in car vs ht

 I'm sure you noticed that most car audio subs seem to have a high fs compared to home theater subs, this is because the manufacturers know that the cabin gain will fill in the low end. Play around with the filter on other subs and you'll find that you'll find more subs that fit your application. You'll find that there are lots of subs that will play lower than you expect, and the higher tuning and smaller box will help with the excursion.

I've been into car audio for a while and would say you shouldn't worry about finding an "SQ" sub too much. The benefit of low distortion really isn't that important with subs because once you get playing loud enough that the distortion might be audible, things are shaking and rattling anyway. Flat frequency response is much more important which comes from a properly designed enclosure more than anything.

Some of this stuff can be complicated, so if you have any questions let me know.


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Woldemort
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@mistersota thanks for giving such an elaborate answer. I have played around with thw linkwitz filter, but I have heard to simulate it from 70hz to 15hz? And I have looked at the inductance changes also.

This setup is going to be like sq first, spl second, so I would want to get as much output as I can from my sub.

I thought I could just aim for the highest spl with the box, then tune it down with eq for my sq profile. Would there be a problem with this? And generally you'd wqnt a rising response of 3dB/oct from 200hz down. At least I've heard that on psaudios youtube.

My current setup was a soundqubed hdx315 in 100l box tuned to 29hz as vest as I can, i measured it and it does peak at around 30hz with a rising response to that, then it continues in a straight line down to 24hz and drops.

This is why I wanted to tune to 25hz, so the response would go all the way down to 20hz

Tuning lower will also help with cone control and push down the problems that the port introduces.

The subs are going in a "trunk wall", which I have hears is the best way to get good sq, while still being able to play louder than infinite baffle. I think the quality of the sub would be heard better when they aren't in the trunk like they are now.

I would take the mx15s, but they don't handle as much power as I'd like. As said I have 4kw pee sub and I have a um15-22 that I recently tried in the trunk and it couldn't handle 2kw at - 5db gain. Something with at least a 2,75" or better yet 3-4" coil would be better. The sql15s have 2,75" coils but they are superior in every other way to other subs I have compared at the price point. I'm so bummed they don't ship to finland.

Oh and I've never been explained how, but I have heard playing under Fs causes distortion, and low Fs drivers tune more easily low, that is why I would want something with an Fs of at least under 30hz,better yeat 25-20hz.

I may have forgot something but😅. 


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Mistersota
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@woldemort I have found that cabin gain does start to roll off around 15hz, but it's also true that cabin gain is difficult to model, so the general trend is what you should look for. you really should try to simulate your car for the starting frequency, 70hz is something a smaller hatchback like a mini cooper would have, if you are sealing off the trunk then yours might be even higher. A slight rise in low end is also preferred yes, especially in cars because road noise tends to be around the same frequencies so you have to compensate. 

What kind of music do you listen to? Organ is really the only music I know that has content below 20 hz and even electronically simulated music is rarely below 25hz. Generally a box tuned to 27hz is the lowest I would ever go in a car because it will control excursion down to 20hz and it should get you a rise to around 24hz. Lower than that and you'll need to sacrifice port area, which will lead to chuffing. The only exception would be if you want to do crazy low-frequency demos that flex the car into pieces. 

Tuning below fs isn't really a problem with dedicated subwoofers, because, at those frequencies below fs, our brain has trouble hearing the distortion. Where tuning below fs becomes a problem is when the bass driver is also playing midrange, the intermodular distortion is what is audible, meaning when the driver plays that low note, if it's also trying to play vocals or something, those will sound distorted. As long as a LP is applied, it's not an issue.

If you're using parametric eq then going with a max spl approach can be a good idea, but if you have to make drastic changes, then you might notice it because the sub will be working much harder on certain frequencies than others.

Yeah the MX15 was more of an example, if you're looking at something to take that power you really need to look at car audio-focused drivers because it's not possible to get that kind of power out of most house outlets so Dayton doesn't really make their subs to take it. In Finland I'm really not sure what you can get, most of the stuff that is really good here in the U.S. is from small distributors like SI, PSI, FI, etc. They aren't likely to have international distribution at a good price. The big companies like Rockford, Alpine, Kicker usually don't have the same value. B2 audio maybe? Their nice stuff is really spendy here but maybe not where you are because they are from Denmark, right?


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Woldemort
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@mistersota I have a semi-parametric equalizer in my dsp and I have a umik-1 that to measure the response. So making an spl box should be fine? Or should I make a series tuned 6th order? Wouldn't that bring up the upper end? I calculated at some point that I should have room with 200-250l with a port tuned to 25hz and 30ms/m of air velocity at 8kw. I don't really have the room for a 6th order if I don't make the lower tuned side smaller than 200l.

I listen to a lot of electronic music, which can often go right down to or close to 20hz, but about everything goes and should go in this car also. Maybe I should tune to 27hz.

Right now I'm looking at b2 and ground zero. I've heard good about b2, but they don't really talk about how they achieve their boasts of good sound quality. No talk about xbl2, shorting rings, interesting motor design or progressive spiders. If I see a pair used I might buy them. They are probably cheaper here, but I'd have to buy a rather high end version to satisfy my needs. And I don't really have the money for them.

Ground zero boasts about using klippel to optimize their subs and some of their subs have won sq prizes in car audio magazines and shows. I am looking at the gzrw38-d2 and the gzhw38spl. They both have 3" coils so I think they should take the power better than any 2,75" coil. The spl has a ring for 3500w peak, so at least that should take 4000w. The gzrw38 has lower fs and more xmax. It's 50mm of total xmax vs 45mm on the spl model.

The gzrw38 is so cheap I could buy them new right now. The spl I have seen used for the same price often. I could almost buy any ground zero subs here as they are so popular.

Do you have anything to say about any b2 aub or gz sub? 


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Mistersota
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@woldemort 6th orders are overrated in my opinion. They will bring up the upper end, but I never cross above 70hz anyway, I can't stand when I can hear where the sub is placed. I don't use pro midbass drivers though, so my mids can play down to that crossover. 

I don't really have much experience with either brand, but I can tell you that just because the ground zero is a xbl2 design having klippel tuning, doesn't mean it's sq based. With xbl2 drivers they often take xmax at 70%bl loss, when in reality, xmax of xbl2 subs is limited by distortion due to their high inductance. These problems can be mitigated with shorting rings, but I don't know if ground zero uses them in those subs. If the difference between the spl and standard might be significant, but you should really look at the winisd model to see what actually performs better for you. If the difference is something like power handling, then you'll have to ask ground zero whether the upgrade is worth it. 

As for b2 I really don't know what technologies they use. All I know is that I haven't heard anything bad about them. I am skeptical of any brand who claims to be äudiophile". This branding usually caters to those who are not familiar with the science behind speaker making and thinks there is some sort of magic to make things sound good. My guess is that they might put more money into marketing than into research.

If I were you I wouldn't worry too much about using that full 8000 watts. It is cool to see subs on that much power, but you're only getting a few dB extras with exponential risk of blowing subs. I'd stick with the subs rating rms power, then 6dB of headroom for peak transients. 

With 250 liters of room, you have plenty of room to go with a high vas driver that is optimised for sensitivity, or even 18s if they'll fit in your vehicle.

For what it's worth, I NEVER buy used subwoofers. I'd say that 50% or more of the used audio gear I have bought or went to buy is burnt up. One time I spent $240 on a sub used, it was perfect looking and sounded good in the guy's box, but when I got it home I tried to play a free air tone, and immediately I heard crackling. I ended up having to buy new drivers anyway and could have got something much better for the money I wasted used. Let my mistake be your lesson.


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Woldemort
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@mistersota e.g. hexibase uses 6th or even 8th orders to flatten out the response, but a ported enclosure is so much easier I will probably go with that. I am thinking of going with Lavoce WAF123.03 mids to get low midbass and more sensitivity. It has very good xmax which I want, because I can barely cross my 10s at 70Hz without hearing the intermodulation or what it was you were talking about in the midrange.

I have a sedan so 2x15" even is a stretch to fit vertically pointed forward. But I'm going with as much cone area to get maximum efficiency.

I have personally bought almost everything used. Might be that Finns are more honest or might be good/bad luck, but everything has worked almost perfectly till now. I even bought a Focus fx3000d as my last amp, that is ancient by now, and it still gave me 3300Watts. The soundqubed that I own was also bought used at less then half the new price, and it was barely used, coils clear and surround was still stiff. I usually try to test everything as best as I can, but I have saved maybe thousands of euros by now so...

What should I really look for in a driver that has good sound quality and will produce both lows and midbass clearly? Some say tight spiders, some say loose spiders etc.?


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Mistersota
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@woldemort tight spider vs loose spider isn't really a good way to look at things because other things like motor force and vas come into play. The best sub is one that will work well in the ported alignment you want. QTS is really the best spec to look at if you want to know that. low qts .2-.4ish will work best in a small enclosure with a low tuning. It will provide an extended roll off that can be eqed up or take advantage of cabin gain. Thats the boombox alignment in winisd basically. ,4-.6 will work best in a medium enclosure with a medium tuning and will have a steeper rolloff, but more output up to that rolloff. .6-.8 aren't recommended in ported boxes normally, because they tend to need larger boxes and have steep rolloff, however, with cabin gain and a small enclosure, they can work well. They are suited best for sealed boxes because they tend to have a 12db/octave rolloff in reasonable enclosures which matches the cabin gain filter well. .8+ are generally used for large sealed or IB configs.

Overall, since you are looking for something low fs and want it to take advantage of cabin gain .3ish would be a good starting point to look at. A side effect of a low fs driver is low sensitivity as well. To make up for that you'll want to find a high vas driver, unfortunately with that, Xmax generally suffers, so you really have to make a trade somewhere. As far as finding something that is low distortion, things to look for are "relatively low inductance". I'd say under 3 is good for 15s, shorting rings are also good. Unfortunately again these things aren't really on budget high power subs, so again you might have to compromise. I really wish their was one perfect sub, but its just not possible.

Anything past those options is really just sound quality "magic" in my opinion. The "sealed subs are faster" and such is just false. The only reason that myth came around is that ported boxes can be harder to get right, and people were used to hearing peaky responses. In reality, almost any sub playing within its linearity will sound the same if the frequency response is good. That said, I usually have sealed subs in my cars, but actually, the sub is the thing I worry about least in my car audio systems because bass is so easy to get. It's the mids and tweeter that usually can't keep up. Maybe with those Lavoce mids that might not be true though.

Speaking of mids, are you making ported boxes for those mids, most of the problem with using pa drivers for mids is that they have a low qts which is made for midrange in sealed boxes or midbass in ported boxes. If you are planning on going sealed or better yet IB then something with a higher qts will probably be better. I'm not sure if you guys have SB acoustics or SB audience in Europe, but they have a budget IB model the Bianco 120B150 that is made just for that. I have actually heard of people using PA drivers for their subs because the are so high sensitivity, but I doubt you'd find one with low enough fs and enough xmax for your amp. At least at a reasonable price.

It's good to hear that you have good luck with used. Like I said I wish I had a better answer as to what you should get, but sq subs aren't really made for high power, to play low, be sensitive, work well in ported enclosures, and be cheap. You will have to make some trade-offs. 


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