Source
r/diysound•
MainStreaming

I bit the bullet for y'all.

Subwoofers

I've been browsing various 15" subs on the internet since the ones I want are out of stock and I came across the https://www.rockvilleaudio.com/w15k6d2-v2/ . w15k6d2 v2 (placing this here for google keywords in case someone searches for a post like this)

ON PAPER it had decent motor force, xmax, sensitivity, mms. Everything I look for in a decent subwoofer. Unfortunately I ordered one and the specs are way off. instead of the qts being 0.6, it's a whopping 0.93 lol. mms is 322 instead of 271, LE is damn near DOUBLE what they specify (4.0 instead of 2.7).

Essentially this all adds up to meaning that above 50hz you lose a LOT of output compared to what you modeled.

https://i.imgur.com/LB82FjZ.png

The bold line is the specs I got after testing, and the thin line is the on paper specs from their website.

The one spec that does seem to be accurate is the xmax spec, it might not be linear, but it definitely seems like it hits at least 20mm one way xmax.

Also here are the specs I got after testing. https://i.imgur.com/EZvVCk3.png

Posted Dec 6, 2021, 6:55 PM UTC

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MainStreamingOPMOD/r/diysound•

The smoking gun for me that it's not just a fluke is that literally all of the specs are just flat out worse.

There are some positives I have to say about it, the build quality is good, the cone seems VERY durable, and aesthetically it's not a bad looking speaker and it has a big 3" voice coil with lots of venting (that I can verify do work).

I would imagine it could definitely withstand some abuse from noobie car audio people but unfortunately it is not going to work for me.

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GeckoDeLimonEminent Sage & Junkie•

Damn, son.

EDIT: IGNORE THE BELOW. I WAS CONFUSED, but I don't like deleting posts and leaving holes in a conversation.

I'm starting to sense a pattern to GRS, which is that they're not diamonds in the rough. It's worth just about what it's priced.

When I was messing around with their planars, I had heard some additional comments that occasionally GRS drivers ARE to spec, and they ARE amazing value for money. But if GRS is saving money with lax QA...well, we can't really recommend someone build a system around their products if the outcome depends on luck of the draw.

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mtg90Designs neat stuff for DIYSG•

OP bought a Rockville driver not GRS, I'm not saying GRS are that much better but I've used the 6" and 10" pro drivers and found they are quite decent for the price. Some of their other woofer offerings aren't great.

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MainStreamingOP/r/diysound•

Tested GRS 12SW-4HE specs

https://i.imgur.com/wiYaDFU.png

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MainStreamingOP/r/diysound•

Check out one of my other comments. I've tested the GRS 12SW-4HE and it actually had some better specs than they advertised. More efficiency and little less inductance and the only spec that was lower was the motor strength, however it was a negligible difference (10%, which in reality is basically nothing).

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MainStreamingOP/r/diysound•

Hey u/mtg90 , are there any horns/compression driver combinations on parts-express that you would recommend for high output with similar dispersion characteristics to the SEOS 15. I'd love to use a SEOS 15 but it's not available for purchase.

And by high output I mean like something that's 125db+

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mtg90Designs neat stuff for DIYSG•

Well I have dozens of horns and waveguides and a similar number of compression drivers I'll be starting to get into testing soon.
Most of the compression drivers I have are on the more inexpensive side though there are a few larger and more expensive units.
Right I know now the Eminence WG-10 has decent properties, not quite as uniform as the SEOS-15 but from the measurements I took put coverage closer to 90 degrees then the rated 70. PE doesn't sell it anymore but it can be bought direct from Eminence.

I used in in this design and you can see the off axis graphs and polars here.

As for compression drivers the B&C DE250 is still a solid choice, the Celestion CDX1-1745 is another that offers similar performance and costs a little less. the CDX1-1730 is decent also but more expensive. Haven't yet tested any others available from parts express in the similar range of high performance 1" drivers that can cross low.

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MainStreamingOP/r/diysound•

You're talking about the wrong brand G, this is a post about rockville not GRS. I've actually had a good experience with GRS so far.

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GeckoDeLimonEminent Sage & Junkie•

Agh. My bad.

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[deleted]•

[deleted]

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nolongermakingtime•

I had a grs 10 sub for 4 years. Held up like a champ in the Texan sun.

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evdiddy•

You wouldn't want to be having your subwoofer crossed much higher than 50hz correct? If i'm not mistaken.

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MainStreamingOP/r/diysound•

This subreddit isn't just about home theaters. I've been looking for drivers to use for a budget high output deep extension PA system that can cross at 120hz

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evdiddy•

Fair enough - thank you

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Withdrawnauto4•

you can get 18" pa speakers for quite cheap. not sure how they sound but Harmony Ha-p18ws8 was the first i found for 80£ its probably not too good tough. also car subs and PA subs work slightly differently. PA subs are able to handle alot more power but they are not as efficient if i remember correctly. some of the passive subs also have a transformer to change the 100v from some PA amplifiers to something more resonable. not sure how common it is i cant find information on output voltage on amps for some reason

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Audbol•

Yeah that's pretty wrong. PA subs are MORE efficient as they have higher sensitivity and I'm not aware of a single PA speaker that uses 70v or 100v aside from the overheard speakers you see in restaurants or office buildings but that's not really what I would call PA.

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Withdrawnauto4•

i have seen some been sold used in my area maybe its vintage or some odd setup. when i have been helping with audio at my school they never mentioned what ohm the speakers end up as. say you have 3 or 4 tops per side they never mention anything other than plugging the first one into the next one with speakon. why doesnt more system use the 100v or 70v in that case it seems like a good way to be able to have more speakers per amp. guess there are some other drawbacks

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thulle•

80Hz is the THX standard, and if the placement and crossover-filter allows it you can go to 100Hz with good results.
I have speakers on my desk about 1,2 meter or ~4 feet in front of me, and one subwoofer on each side about 2,4 meters or ~8feet away. With a 24dB/octave crossover any setting above 80Hz makes sounds start to drift to the sides, so that for example a sound panned fully to the right speaker starts to be perceived slightly to the right of the speaker. I.e. the sound from the subwoofer starts to affect the perceived sounds negatively.
If I had the speakers on stands across the room and the subwoofers nearby them I think 100Hz would work fine.

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evdiddy•

Thank you for that. I'd be the first to admit that i am a novice at this, but am trying to get the knowledge base down pat.

Thanks again.

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O3JSycdfEVY36lvWuzjb•

How about MTX RT15-04?

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MainStreamingOP/r/diysound•

just from looking at it, I know that I would never personally buy this speaker, no shot that magnet is big enough

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asdaf4256•

Bought the 12 of the same k6 line (W12K6D4-v2), mostly because I was impressed they included an Le measure in the published specs. Turned out measured specs were similarly off, in the 'worse' direction, though I think not by nearly as much as yours was.

Here is what I measured with a DATS, coils in series, after break in:

  • qts .893
  • qms 6.95
  • qes 1.012
  • fs 36.69 hz
  • vas 1.218 ft3
  • Le 8.05 mh
  • Re 8.34 ohms
  • mms 194 g
  • sd 500cm2

I see you are looking for budget PA; have you checked out the new GRS pro audio lineup?

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MainStreamingOP/r/diysound•

If you want to see something interesting, compare the sensitivity of each GRS pro audio drivers and you'll see that they stop increasing after a certain driver size, pretty weird.

And I think that answers your question, but yes I have checked them out (not purchased) and I'm not interested purely on an XMAX basis.

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asdaf4256•

Cool, I figured as much; you seem up on the GRS models :D

And yeah, when I compared them (on paper) to the dayton equivalents, the 12 and under compared pretty well, but the 15 and especially 18 seem to use such badly undersized magnets (maybe the same magnet and voice coil as the 12?) that I can't see any use for them at all.

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MainStreamingOP/r/diysound•

I'm up to date on an insane amount of subwoofer drivers lol

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mightycicadalord•

My favorite budget pa drivers are the dayton pa series. Kind of a bummer the prices have gone up, I got six of the pa380 for $70/each a long time ago. It looks like the GRS pro stuff may come from the same factory even.

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asdaf4256•

Kind of a bummer the prices have gone up

Big time. There's an open box pn470 right now that I wouldn't mind picking up, but it's marked down to more than they used to be new! I wonder if they will come back down at all, eventually?

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MainStreamingOP/r/diysound•

I actually had a private conversation about these right when I bought one and I also remarked about how low the published Le was

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fomoco94•

This brand is known to be junk and mocked by anyone in car audio. Your results are not surprising at all.

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MainStreamingOP/r/diysound•

The thing that really surprised me was that it seems like it actually can hit 20mm of xmax without a fuss from the suspension.

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fomoco94•

But can the motor assembly drive it there linearly? That's much more a design challenge than a loose suspension.

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MainStreamingOP/r/diysound•

Lol that's the thing, it has tight suspension, not loose. Also lets be real, linearity is the least of my concerns when running a 130 dollar chinese subwoofer driver near the limits of its xmax. 30hz Fs for a high mms driver = not loose suspension. I can't comment on the linearity, but it still sounded like bass to me.

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Velocipede_Acoustics•

That doesn't look like the response of nearly a 1 QTS. It looks a lot closer to .6 QTS. You should see nearly linear response until the FS. Something is up.

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MainStreamingOP/r/diysound•

you didn't even ask the box size or whether or not it's vented or sealed. post an example of what you're talking about.

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Velocipede_Acoustics•

Understanding driver response and how it correlates with QT parameters is described in literature. I don't have a link right now.

Generally speaking, if the woofer was near a 1 qts, and in free air or infinite baffle, you would see the responses would be linear to it's FS and a slight hump near FS.

In a sealed box, you would be changing and increasing the total Q past 1 and you should see it peaking near fs more sharply. Your example looks a lot more like a low QTS woofer with an overdamped response as it plays near Fs.

In a ported box, well it gets more wacky with a high Q woofer.

I'm just generalizing and giving a talking point too see if there is other possibility here. Obviously I don't know how you modeled it.

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MainStreamingOP/r/diysound•

I mean all that is fine and dandy, but could you post an example? The things I look at on a driver are the product of (BL^2 )/Re/Sd) , sensitivity, inductance, and its xmax.

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Velocipede_Acoustics•

Here is what I'm talking about described related to visualizing QTS.

Scroll down a bit and you'll see the graph.

https://www.caraudio.com/threads/why-does-qts-matter.591101/

This isn't meant to address the inductance issue you're seeing. When I model drivers in ab In or a large sealed box, this is how they always turn out. So, based on this, I'm suggesting that maybe your TS parameters DATS gave you may have been in error. If you have a box, maybe you can try the box method instead of the mass method? I don't know if that would help.

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