Gone to 1994 low watt high output build plan

[94caddy]

I'm in the planning stages of this budget build. I don't want to dishonor the car or the year 1994 with this build. The box is the most important part of this build, but I have some questions about equipment. 

I am novice about subwoofers but I have installed subwoofers and amplifiers with prefab box before and been researching a lot in the past few months. In this car all remains stock exception I replaced the 4 interior speakers with cheap new Pioneer after suffering intermittent malfunctioning. There is already 4 gauge electric in the trunk thanks to the inverter I installed there. I want to continue with the stock head unit in the current configuration and add line-out converter from rear speakers.

I have at hand a 1994 Cadillac DeVille sedan, and a 43dxa250.1 Kicker amp. I picked up this amp new on clearance for pennies on the dollar so I wouldn't be hurt to have to sell it and select a different one. The car stays. 

My plan is to buy the Rockford Fosgate 15" p1 2 ohm SVC subwoofer, and build my own ported enclosure. RF recommend for the speaker 2.66 cubic foot and 4" diameter port measuring 10 13/16". 

Both the amp and the speaker are rated for 250 watt rms @ 2 ohm. These selections are both new equipment but I am hoping they'll qualify as a nod to 1994 when built in a custom enclosure.

I'm wanting advice to confirm or correct the following statements, from what I've read the numbers of amp power and speaker power handling matching exactly could result in an underpowered speaker. In the bigger box, less wattage is needed to reach full potential of the same speaker. It's the manufacturer's goal to advertise the speaker performing in less space leading to fits in more cars therefore sells more units. When the speaker could possibly perform better in a larger space.

The next question I have about this setup is EBP. Does it really matter? Specification provided by manufacturer Fs 23 hz and Qes .80 leads to 28.75 EBP. This makes speaker suggested for sealed enclosure. Is it inappropriate of me to want to override that suggestion?

thanks for reading. (stock photo used)

[ShadeTreeMechanic]

Welcome to SMD, maybe @Triticum Agricolam can help answer your questions. Tuned in for pictures.

[94caddy]

pictures hopefully in original orientation. they keep twisting 90 degrees. this is the third upload.

[ckeeler11]

I would have sub and port on same plane. As for it being used ported, I'm not the expert but I would say with the low QTS and limited Xmax it would be better in sealed. EBP is not the be all end all if it is close but it is pretty low. Will it work most likely but you could end up reaching mechanical limits before tuning and or have a very peaky response.

 

If another expert chimes in hopefully they will correct any missed points on my part.

[94caddy]

I might then have to give up on my dreams of ported and go to sealed. I really wanted to hear how the ported sounds like, and a lot of the great builds I saw here have ports in them. After much research I am not finding a 15" speaker that would work well ported without blowing up the budget for this project. The better brands charge more; require an amplifier swap, and the cheaper options champion poor customer reviews.

I have been looking in the p1 sub for a while and RF changed/updated their website on me. They took away some details from the product description/specification page which allowed me to find this link http://www.rockfordfosgate.com/support/knowledge/?knowledge_frame_url=http://rftech.custhelp.com/cgi-bin/rftech.cfg/php/enduser/std_adp.php?p_faqid=1125&p_li=&p_topview=1 

This suggest that sealed box size up to 3.5 cu ft is appropriate for the speaker. I had previously only seen their 1.58 recommendation.

An excessively large sealed box could give me the look that I'm wanting. and though not as impressive as ported I would still be significantly increasing the bass when changing zero subwoofers for one subwoofer. 

3.5 cubes is good, but from here, could bigger be better?

[Joe X]

On 11/2/2017 at 8:43 PM, 94caddy said:

I'm wanting advice to confirm or correct the following statements, from what I've read the numbers of amp power and speaker power handling matching exactly could result in an underpowered speaker. In the bigger box, less wattage is needed to reach full potential of the same speaker. It's the manufacturer's goal to advertise the speaker performing in less space leading to fits in more cars therefore sells more units. When the speaker could possibly perform better in a larger space.

The next question I have about this setup is EBP. Does it really matter? Specification provided by manufacturer Fs 23 hz and Qes .80 leads to 28.75 EBP. This makes speaker suggested for sealed enclosure. Is it inappropriate of me to want to override that suggestion?

thanks for reading. (stock photo used)

 

 

First, low power and low Xmax means you are not getting very loud no matter what you do, the only thing in your side is cone area, I wouldn't recommend using EBP as sometimes hits and sometimes not, better is using modeling software.

Let me show you some plots for this driver, for my suggestions for box parameters:

Yellow: Ported box 3 cubic feet net @25Hz 4" round port.

Orange: Sealed box 3 cubic feet net

 

As you can see pòrted dominates output in the frequency range that matters, just one problem, if you play very low frequencies you could damage the driver:

Here's cone displacement:

 

As you can see if you played something below 20 Hz you could damage the driver, if you have a subsonic filter in your amp that shouldn't be a problem.

 

Your other option would be a different driver which can get louder on the same power can that costs about the same, I would pick the Sundown E15v3, Here's a comparison:

 

 

As you can see this driver overtakes the p1 in the 28-40Hz range (box 3.25@32Hz) the P1, it has greater Xmax and a power handling of 500W if you were to upgrade amp over time, this is just an example, there will be other drivers that could be considered.

 

 

 

 

 

 

[94caddy]

I've taken your advice to use modeling software and downloaded WinISD 0.7.0.950. I have only played with it since the last post in this thread and used the help file that comes with the program to teach myself to effectively enter in information about a speaker. That ended my self-training and I dove right in to making charts.  

Rockford Fosgate p1 and p2 speakers went out of the picture when I played with charts including American Bass TNT1544, Apline SWS15D4, and Sundown E-15 v.3. The P3 speaker come close but failed against each of the other brand speakers. The difference in the chart is tiny. All the speaker seem to do nearly the same.

I started notice at 250w on "port velocity" that with a single 4" port it was too much. Based on research I wanted to limit that to less than 20 m/s. I changed the port to 6" and that resolve the problem. Though when I upgrade the amplifier to 500w the port velocity increases too much. though the change in SPL output is tiny. to keep the options open, a triple 4" round port would further limit port velocity. Anything bigger (in total port diameter) gets too long in length. 

Dunno if this is actually true, but chart says can do with 250w, quite nearly, what it would do on 500w. 

Its looking like Alpine SWS 15D4 vs American Bass TNT1544 from here.

I was experimenting changing box size and tuning around to get the highest and flattest SPL line. Is that correct? 

[Joe X]

So that's great that you are working extra to get a better outcome, it will pay off, anyhow, I'd like to point out that WinISD is not designed for car audio use and frequency response curves will be off, there is a workaround to sort off fix that but for now you should not rely on those plots to draw any conclusions on how the subs will play inside your car, the other plots will be accurate, vent airspeed, cone displacement, etc.

You have already reached a couple of important conclusions on port area and power, the 4" will not be enough port area for those other options and power is not your first option to get louder, usually box alignment and cone area are better options as long as your box size is feasible, also you should consider slot ports you can set your port area to whatever you want, a limitation with areos.