Using non-IB subs in an IB?

[exipnos]

Got a mail back from seller who spoke to Hifonics. They say the following.


"have talked with the hifonics service.... they have the tech. specs. in two different ways.... xmax -35mm + xmax +35 mm = 70 mm xmax complete"

Please help me understand what is the correct xmax for these drivers and what do I use in my calculation for displacement? Shall I try to get my money back? I will probably not get my shipping cost refunded and I will have to pay 80E to send them back as well thus 160E out of pocket.

[chrisbee]

With luck 70mm is the realistic 2-way peak excursion. So the real Xmax which is one way and used by all reputable manufacturers should be about 32.8mm.

However, since the manufacturer is also claiming only +/-16.4mm you had better see how far the cone will move without effort. Do it carefully!

Spread all your fingers well over the dust cap to distribute the forces evenly on the cone. Then see if the cone will move inwards easily to about 15mm. Or if it will go easily to 30mm.

It's a big difference between these two measurements. I wouldn't take the manufacturer's word on this without testing it for yourself.

I just went out and checked my AEIB15 drivers. Both types have similar Xmax but the old type is much stiffer to move than the newer ones. However, both types will move inwards by about 15mm from the rest position before increasing resistance is felt from the suspension and spider.

There's no need to be dead accurate. Either the cone will move inwards by 15mm. Or it will move inwards by 30mm. It should be easy to tell the difference. Just don't force anything or put your finger through the cone or dent the dust cap. Otherwise you can't return them.

[exipnos]

hmm. I just tried your suggestion. Difficult to measure but I think in the end I found a method to give me an idea.

I put a ruler on the edge of the dustcap. I had a stiff book on the top of the surround. I measured the distance to the edge of the book at resting. Then I pressed on the dust cap, kept the ruler and the book in the same spots and I measured the same distance.

I think its the 16.4 measurement and not the 35mm.

So what are this telling me?

I don't understand how they can give me different figures for the xmax. To me their clarification that the 70mm that is in their web site, make sense. Its -35mm and then the +35mm. So thats the two way travel of 70mm. Correct?

But then how does the linear xmax come into play with the xmax of 35mm that they confirmed. Are they maybe using the 35mm xmax to be xmech?

When I press down on the dust cap am I reaching xmax linear or xmech? I don't think I was close to 35mm.

[chrisbee]

The correct physical way to measure Xmax is: VC length - Gap Height/2

You can't easily do this without dismantling the driver. Which will invalidate your guarantee and/or consumer protection.

I just used your method and find 15mm just possible but can really feel the tension building up rapidly as I push on the dust cap. My drivers are 15mm (old type) and 18mm (new type) Xmax. Both show similar resistance to greater than 15mm of movement.

If the cone won't easily move inwards by more than 15mm you should use their figure of 16.4mm as your true Xmax. For displacement calculations use 32.8mm. (2 x Xmax x Sd)

So your new drivers are very similar to my old AEIB15s. You have about 10 litres of displacement. Just safe enough if you are careful. If you try to boost the VLF to compensate for the rather high Fs you will rapidly run out of excursion.

Your EU or national consumer protection laws should allow you to return the drivers free of charge for a full refund. But only if they are not remotely 35mm Xmax as claimed. I would talk to your local consumer protection officer to see if they can discover more on your behalf.

[ThomasW]

Then I saw that there was a small sheet with some thiele/small parameters. Well they where mostly inline with what was published on the site but the xmax was different.

They say xmax +- 35mm (peak to peak) and xmax +- 16.4mm (linear). If I understand correctly I'm to use the 16.4mm in the displacement calculations right?

Separate measurement sheets are usually correct. So my guess is yes +/-16.4mm is the real world Xmax. Since they go to great lengths to mention the +/-35mm Xmech it's likely these drivers (like many car drivers) can be over driven without damage.

What you're experiencing typical of car audio woofer specs, and it's why we recommend specific drivers with proven/known parameters.

That said, your room isn't all that large. You have corner loading, that will increase output. So the drivers may workout fine, they just won't give you massive amounts of output without distorting. That's better than being damaged.

[chrisbee]

I hope my rough and ready advice on quickly judging Xmax (as one way from rest) is ball park valid? For future reference for other unknown drivers.

I know it's far more complicated than that but exipnos needs a quick answer to help him decide if he wants to keep his drivers.

John at Acoustic Elegance has shared his infinitely more expert insights on Xmax here:

www.aespeakers.com/phpbb2/viewtopic.php?f=4&t=1603#p4581

Unfortunately none of it will help exipnos answer his need for a realistic Xmax for his new drivers.

[ThomasW]

Jan 2, 2012 13:43:01 GMT -7 @chrisbee said:

I hope my rough and ready advice on quickly judging Xmax (as one way from rest) is ball park valid?

It's probably as good as any. IIRC Linkwitz has a technique/ diagram for guestimating Xmax on his website.

We've never seen exipnos' room. It maybe that he has all the Vd he needs, but lacking specifics about the room and his want's/needs all we can do is guess.

Does anyone know if Blade-ice still supplying Fi drivers?

[exipnos]

Jan 2, 2012 13:54:14 GMT -7 @ThomasW said:

We've never seen exipnos' room. It maybe that he has all the Vd he needs, but lacking specifics about the room and his want's/needs all we can do is guess.

First let me apologize for polluting this thread. In the beginning it was on topic with my less expensive drivers but now its not. Sorry. Shall I continue here or create a new thread?

The room shell is roughly 6.3m long, 4.2m wide and 3m ceiling. So about 79m3. But inside the room I also built a stage, riser, and soffit so maybe take away 7m3. So I would say roughly 72m3. Its completely enclosed with separate very solid door.

Room will be treated.

The bassbox simulation I posted previously still shows the same curve. But for cone excursion, I reach the 16.4mm xmax at 14hz.