IB with sheet metal + sound deadener

[rizznits]

I have been looking into doing an IB install in my '03 Accord, as shown in this post: http://www.diymobileaudio.com/forum/showthread.php?t=7030.

I bought an Infinity Perfect 12d VQ with the hopes of using it for IB in the top of my rear deck (pictures in other thread). I know some people say I will need more cone area, but my rationale was that A) 1 would be 1/2 the price of 2 and take up 1/2 the space, and B) that if I wanted a total of 2 ohms, the DVC version was 3db more sensitive than the SVC, so maybe it would suffice.

Unfortunately, as can be seen from the pictures, doing an IB will be a big pain in the butt unless I want to really chop up that rear deck or put a very low MDF ceiling in, which would lay lower than my trunk arms and all that other junk. Which leads me to my main question. Is it necessary to use MDF as a baffle, or could I pull the 6x9s, plug one of the holes with MDF, use the other hole for the 12, and seal the top of the metal deck really good with Raammaat or something. Would that not be enough to isolate the front wave from the rear?

I really don't want to lose my fold down rear seat capabilities, so please don't tell me to put it through the pass through or something (been told before). If this is unrealistic, I might just use a 12" box I have sitting around, match the VQ insert to the size, and be done with it. I have heard that IB sounds very musical, delivers great low end (which I want) and is a space saver, but given my constraints, I am not sure if I can pull it off with the amount of time I have (full time job + serious girlfriend), the amount of money I want to throw at it, and my unwillingness to mangle my trunk or lose its functionality.

Thoughts?
Ryan

[rizznits]

Hmm... no responses, anyone know of another thread that has discussed this? I've done a lot of research, and don't recall seeing this discussed specifically...

[MarkZ]

I have been looking into doing an IB install in my '03 Accord, as shown in this post: http://www.diymobileaudio.com/forum/showthread.php?t=7030.

I bought an Infinity Perfect 12d VQ with the hopes of using it for IB in the top of my rear deck (pictures in other thread). I know some people say I will need more cone area, but my rationale was that A) 1 would be 1/2 the price of 2 and take up 1/2 the space, and B) that if I wanted a total of 2 ohms, the DVC version was 3db more sensitive than the SVC, so maybe it would suffice.

Is that really true? Are you sure they're being measured at the same wattage?

I know this doesn't answer your question, but running IB with only 12" of cone area is a little dicey.

[chuyler1]

Sell the subwoofer and get two of these...
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-864

[chad]

Check you 3dB figure again and make sure it's not 3dB more efficient with a set voltage input (like 2.83V) as opposed to a true 1W/1M measurement. You may be suprised.


Chad

[rizznits]

From 'the real deal with 8 ohm drivers' thread by npdang: A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. So, can I assume a 2 ohm speaker rated for 90db at 2.83V is rated at 4 watts?

My guess is that if you use 2 ohms, at 2.83V, you are doubling the wattage that you would use for a 4 ohm speaker, and thus adding 3db? Is that correct?

If you look at the IDMAXes, they have a different spl rating depending on coil configuration, but that is using the traditional 1W/1M measurement.
http://www.imagedynamicsusa.com/pdf/IDMAX12-V3-D4-Spec.pdf
Why isn't there a 6 db difference then? Different winding losses?

Here is a link to the Infinity sub manual (Page 8 shows the T/S parameters):
http://manuals.harman.com/INF/CAR/Owner%27s%20Manual/Perfect%20VQ%20OM%20FINAL%20(Revised%2012-2-02).pdf

Thanks for the replies. Looks like I might be going to a small sealed box :/

[MarkZ]

From 'the real deal with 8 ohm drivers' thread by npdang: A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. So, can I assume a 2 ohm speaker rated for 90db at 2.83V is rated at 4 watts?

Yes.

My guess is that if you use 2 ohms, at 2.83V, you are doubling the wattage that you would use for a 4 ohm speaker, and thus adding 3db? Is that correct?

Yes.

If you look at the IDMAXes, they have a different spl rating depending on coil configuration, but that is using the traditional 1W/1M measurement.
http://www.imagedynamicsusa.com/pdf/IDMAX12-V3-D4-Spec.pdf
Why isn't there a 6 db difference then? Different winding losses?

I don't know what "G.P." stands for. Are they comparing the two coil configurations or something else? If they maintain the 1w/1m standard with two different coil configurations, the result should be about the same in both cases. That's not to say that the result will be the same for two DIFFERENT speakers, one with 4 ohm and one with 2 ohm coils. Oftentimes you'll find a difference, but it's usually not a huge one.

Here is a link to the Infinity sub manual (Page 8 shows the T/S parameters):
http://manuals.harman.com/INF/CAR/Owner%27s%20Manual/Perfect%20VQ%20OM%20FINAL%20(Revised%2012-2-02).pdf (http://manuals.harman.com/INF/CAR/Owner%27s%20Manual/Perfect%20VQ%20OM%20FINAL%20%28Revised%2012-2-02%29.pdf)

Thanks for the replies. Looks like I might be going to a small sealed box :/


I think you should rethink the two sub thing. It looks like they test the DVC version with the coils in parallel, hence the 3dB increase. But two SVC subs in parallel will give you 3dB higher sensitivity than a single DVC sub with coils in parallel. Actually, probably more than 3dB when you take power compression into account. If you want to go IB, I strongly suggest buying a second sub.

[npdang]

I don't worry about isolating the front and rear wave. You may lose a bit of low end spl, but that's about it. The biggest problem I find is the rear deck rattling, especially the grilles.

In my experience I found that an mdf baffle and some raammat were not sufficient to prevent noise, and Ime it was bad noise. I had a 94 accord and it didn't have the arms in the way, so I was able to just stick an mdf baffle to the underside and mount the sub directly to that.

Personally, I'd only bother with IB if I wanted to save space. Sound wise, I haven't noticed any difference with a sealed box vs. IB.

[bobditts]

I don't worry about isolating the front and rear wave.

The whole trick to IB is keeping the waves seperate. NP, maybe thats the reason you didnt hear a big difference in a sealed vs. IB setup? the sub you use makes a big difference too.