Sub build! Beyma 15" driver, help needed :)

[cixelsid]

Another issue with this driver is it's huge Vas 400L. So it's not going to be happy in a small box.

It would be better used as a bass bin to take workload off your 8" drivers. Tune it to an Fb ~30Hz and run it up to 100Hz-150Hz or so.

Since it's 97dB efficient so a flea powered amp will drive it.

[fidomuh]

#sid

Yeah, I could use it for bass-kick instead of rumble.. At least it would sate my need for bass for the moment..
Then I could focus more on finding the right drivers to make a "real" HT sub..

By flea power, do you mean my 2x220 watts? :P
I'll have you know that the amp is quite powerfull actually

[cixelsid]

fidomuh wrote:

#sid

Yeah, I could use it for bass-kick instead of rumble.. At least it would sate my need for bass for the moment..
Then I could focus more on finding the right drivers to make a "real" HT sub..

By flea power, do you mean my 2x220 watts? :P
I'll have you know that the amp is quite powerfull actually

The amp reference was a function of the published efficiency of the drivers. At 97dB it will take a very small amp to power the driver to it's limits. Your amp has the ability to kill it if not properly throttled back.

[Blaser]

No need for a subsonic filter above 21 Hz as suggested by Mike if you build as he recommended. Hey, there will be some LF 106 db @ 20 Hz will be felt

[fidomuh]

#28

I know, just pulling your leg :P

#29

But with an Xmax of ~3-6mm wouldn't it be a little risky to tune so low?
Of course I have two units, so I could always "try" - but they are a bit expensive here in Denmark so would prefer not to break it :P

[Blaser]

Fid,

If you want to DIY, you must accept the idea of "being risky", and to reply to your question, I am not sure it is "risky".

Mike,

Can you pls ask the owner you know the configuration of his sub and power input?

Thank you

[Mike P.]

I sent an email this morning. Just waiting for the reply.

[fidomuh]

#31

Yeah, I know there's always a risk involved, but if I get told it will "surely break", then it would be stupid to try it.

But as always, I'm going for the 23hz build.. 226liters, 23hz tune with 2 ports..
I'll see what I can find at the hardware store regarding the ports.. PVC should be fine right?

#32

Thanks, also, thanks for your help
I will, of course, create a detailed workflow so you can all laugh at my non-existing woodworking skills :P

[Blaser]

fidomuh wrote:

#31

Yeah, I know there's always a risk involved, but if I get told it will "surely break", then it would be stupid to try it.

Sure, but that's not the case

But as always, I'm going for the 23hz build.. 226liters, 23hz tune with 2 ports..
I'll see what I can find at the hardware store regarding the ports.. PVC should be fine right?

Right

I will, of course, create a detailed workflow so you can all laugh at my non-existing woodworking skills :P

No such thing as that in the shack

[cixelsid]

fidomuh wrote:

But with an Xmax of ~3-6mm wouldn't it be a little risky to tune so low?

First the Xmax IS 3mm not 6mm. Second tuning these in the low 20Hz region all but guarantees you'll destroy them. Look at a Unibox or WinISD sim to see where you'd run out of excursion...

As a matter of routine it's no big deal to tune a 'real' sub below Fs since they have so much Xmax. With your woofers doing that is a very bad idea...

[Mike P.]

I think we should wait and see what the owner of the sub pic I posted says. He says it's fine. Let's see what his box size and tuning is. I can't see him saying "it's fine" if the Xmax is only 3mm. That wouldn't make sense.

On another note, here is a pic of the first sub I built a long time ago. The sub is a Pioneer TS-W383 with 6mm xmax. The box is 8.2 cubic feet and it's tuned to 22 hz, powered by a 200 watt plate amp. It was originally used for music and HT and still works fine today. Low Xmax subs can be used as long as you're aware of the limitaions in the low end.

[Blaser]

CIX,

You're pushing me to sound harsh... Pls do not claim something you're not sure about otherwise you risk to misguide people. Even if Xmax is 3 mm, your not "running out of excursion". X mech is 14.5 mm, and the OP is advised to power this thing with 150 to 300 W only.
How many subs have you destroyed this way? Even Steve Callas has reconsidered his LLT over excursion and power limited amp theory after some of Ilkka's tests and discussions that were between all three of us in my build thread.
If you use peak values in your model in WinISD ... don't, unless you plan to listen to SIN waves. Use RMS instead.

It would be a good idea to wait for the advice of Mike P. after he receives that e-mail.

[Blaser]

Good...

[Blaser]

Mike,

Do you use a high pass?

[Mike P.]

Yes, the plate amp has a high pass, I don't remember the exact frequency. It's been a few years since I inquired about it.

[cixelsid]

Blaser wrote:

CIX,

You're pushing me to sound harsh... Pls do not claim something you're not sure about otherwise you risk to misguide people. Even if Xmax is 3 mm, your not "running out of excursion". X mech is 14.5 mm, and the OP is advised to power this thing with 150 to 300 W only.
How many subs have you destroyed this way? Even Steve Callas has reconsidered his LLT over excursion and power limited amp theory after some of Ilkka's tests and discussions that were between all three of us in my build thread.

I started building subwoofers in 1978, and have designed raw loudspeakers for a living, so I just might know a thing to two about this subject. But if my knowledge is unwelcome here I'll leave.

Ciao'
Sid

[Ricci]

Cixelsid,
While I agree with you that these are woofers and not proper subwoofers, I think you are overstating the 3mm xmax thing. There shouldn't be any damage to the units until somewhere past 12mm of one way excursion. As long as the OP uses good judgment, moderate wattage and a rumble filter(this is a must) he should be fine. I also agree that 23hz is a bit too low for these. I think a nice 27hz-30hz tune would give you solid output down to 25hz which is fine for all but the most bass intensive music. It would also give a bit more power handling and "kick" in the upper bass.

That's my 2cents.

[Mike P.]

Sid, your knowledge is more than welcome here! I myself am baffled at the 3mm spec on the 15B100/R when someone has built a sub with this driver and says it's fine. Let's wait and see what he replies to my email and we'll take it from there.

[Mike P.]

I think a nice 27hz-30hz tune would give you solid output down to 25hz which is fine for all but the most bass intensive music

.

For music only I would agree. But we're trying to get the most out of this sub for HT and music, thus the lower tuning. 23 hz tuning still gives him 103 db at 20 hz with 150 watts input.

[fidomuh]

#41

At the least I'd like to point out that I appreciate your advice
If "the other guy" reports back that he is in fact tuning higher, then I will do the same.. 27hz seems appropriate, no?

That way I would still get a bit of the lower end, and a much harder kick in the 30-40hz region

#44

The sub would most likely be used more for music than HT, but it would be nice to have a sub that didn't kill itself on the opening scenes to LOTR or Cloverfield :P

But I like the idea of making the most of what I already have.. Besides, a build like this is not that expensive since I already have the Woofer.. So if it goes south, at least I will have experience with building this stuff

[Blaser]

cixelsid wrote:

I started building subwoofers in 1978, and have designed raw loudspeakers for a living, so I just might know a thing to two about this subject. But if my knowledge is unwelcome here I'll leave.

Ciao'
Sid

Sid,

Your knowledge is indeed welcome and much appreciated. I am not putting your knowledge into question . As a matter of fact some people are already skeptical and confused a lot. Unless a claim is supported it may even confuse them more, and make our job much more difficult.

Below is the suggestion of Mike (8 cu ft tuned 23Hz) with even more power (300 W instead of 150 W). Look at the excursion plot (FYI, I am using PEAK excursion which is not really representative of program material and that's to be really on the CONSERVATIVE side). Excurtion barely reaches 12 mm at 35 Hz which is still far from 14.5 mm).

I herby quote the modification made by the knowledgeable Steve Callas in the LLT Explained thread:

In terms of power, recent measurements performed by Ilkka and the realization that real world playback does not consist of continuous tones have caused me to reconsider my previous amp limiting guidelines. I used to think that one should aim for an amount of power that straddles the rated xmax of a driver in the given enclosure as seen in simulations without exceeding it. This guideline was faulty for three reasons. 1) The xmech, or mechanical limit of a driver's suspension, is much higher than the xmax, usually 1.5x or more. This means there is freedom for more excursion at the cost of nonlinearities, but that extra cushion of excursion is better put to use than having to clip your amp, as the resulting signal sent to the voice coil can be damaging. 2) Simulations show excursion used with a given amount of power based on a continuous playback of each frequency, like a sine wave. This is not an accurate representation of how the driver will behave with real music or movies, as few if any have extended continous tones. Excursion use will be less than the simulations predict with real material at a given power level. 3) A driver's suspension, even if very loose, will tend to resist movement more as it approaches its limits. This acts as another layer of protection.

Because of this, I now recommend using as much power as is economically feasible, with the only caution being fear of frying your voice coil. If you are constantly pushing your driver to extreme playback levels, you will need to be weary of this happening. It's better to put your money towards a second sub than it is to put it towards an immensely powerful amplifier, as the better amp will only get you so far without risk of damage.

I hope this explains why I tried to keep this discussion on the right track.

Apologies for having been tough.

For those who might think a 30 Hz is better, look at the SPL curve below, and tell me if you'd like less roll of than that, not to mention port anomalies would be more involved in the very heart of music...
Mike is a very experienced fellow.... Do not take his suggestions lightly