Subwoofer - Replacement Drivers

[JazzyG]

Just curious, are subwoofer drivers as picky as say tweeters and mid-ranges as far as replacing the drivers for upgrading purposes?

I just picked up a Mirage BPS-150 at a great price, everything works and they sound good with my RCA mini-monitor project I just completed.  However, I was just curious if there was a simple way to upgrade the drivers?  Since the plate amp on the back allows one to tweak levels, crossover points, phase, etc., wouldn't that make substituting a newer driver simpler than say a tweeter or midrange?

What are other popular tweaks you guys are doing to older subs like this?  Bracing, stuffing, damping, rewiring?

Regards,

JazzyG

 

[MartinC]

I'm not an expert but there are certainly minimum specs needed for the driver in that it needs to be able to handle the maximum current and voltage the amp will deliver without burning out or exceeding its intended range of motion respectively.

My gut reaction to your post is I'd use the sub as is or buy/make something better rather than sinking money into trying to upgrade what you have. 

 

[Fatmarley]

The usual way of building a subwoofer is to select a driver, and then model the correct enclosure size and tuning frequency (assuming ported) for that particular driver. This is very specific for each driver, so the chances of finding one that will work in that enclosure, with those ports is very slim.

Sealed speakers are far more forgiving of enclosure size than ported. If you could work out the internal volume, and also give baffle dimensions to work out the largest size driver that would fit the enclosure, I will have a look through all my modelled subwoofers for you to see if any would work.

Do you know how much power the plate amp delivers?

 

[JazzyG]

Thanks guys, I found the spec sheet online, see picture.  It has amplifier specs and dimensions. 

If I can't replace the drivers, I will probably have to replace the foam surrounds at the minimum.  For the price, I could even just rob the amp for a project, but ideally I would prefer to fix this one up with some mods.

 

[JazzyG]

I have another interesting idea I have been thinking about.   What if you built 2 small to medium bass boxes, fitted them with sub plate amps and then mounted your stand mount speakers on top of them.  Blend them in the same as you would a subwoofer. 

Seems like it would work well to turn some 2-way speakers into 3-ways.

 

[MartinC]

I have another interesting idea I have been thinking about.   What if you built 2 small to medium bass boxes, fitted them with sub plate amps and then mounted your stand mount speakers on top of them.  Blend them in the same as you would a subwoofer. 

Seems like it would work well to turn some 2-way speakers into 3-ways.

You could. Depending on the frequency range of the 'sub' though they may well be better situated somewhere else in the room than directly under the standmounts. My subwoofer is in the corner for a reason  . You need more ability to adjust time delays/phase this way though.

I've just checked your kit list though and see you have a JL Audio Fathom F113! So I guess you're more just looking from project here rather than to do anything for your main system  .

 

[JazzyG]

Martin,

Correct, the DIY stuff I am doing is just for tinkering and learning.  I spent the last 30 years progressively building my system until I finally got my dream system, fully aktiv Linn Klimax with a JL Audio sub!  I then went through and started tweaking the system with room setup, cords & cabling, vibration control, power conditioning, etc.  I am at the point I can't really do anything to my main system without spending a lot of money for steeply diminishing returns.  However, I like to tinker and enjoy building up systems, so I started seeing what I could do on a small budget with DIY.  I rebuilt a pair of RCA/Radio Shack LX-50 mini monitors, new crossover, replacement woofer driver, all kinds of vibration control.  They sound really good, but lacking in the bass with a 5" woofer, so I picked up the sub to see what I could to take it up a notch.  The sub is actually sounding pretty good as is, but open to ideas to improve.  The foam surrounds are looking fragile.

The JL Audio Fathom F113 is amazing, by the way!!!   :notworthy:

 

[Fatmarley]

An Eminence Lab12 is very flexible when it comes to enclosure volume. Your enclosure is about 64ltr gross which is outside the suggested, sealed, enclosure volume written in the spec sheet (22 to 28ltr). I don't know how much bracing, or if the amp has a separate enclosure, but if it does, that needs to be calculated (removed from the 64ltr gross volume). The Lab12 takes up 3ltr, so assuming your internal volume is 61ltr, you could put the whole 150watts from that plate amp into the lab12 and you'd achieve 108db at 1mtr (should be more than loud enough for most people). You'd just about reach xmax (maximum linear excursion) at 20hz in that enclosure volume, with 150w. If you reduced the internal volume to 28ltr, the sub would be able to take 400w before reaching xmax, and that would equate to 113db at 1mtr (2.83v).

In other words, the Lab12 should make an excellent upgrade - https://www.parts-express.com/eminence-lab-12-professional-12-subwoofer-speaker--290-570

 

[Fatmarley]

This would also fit and give excellent performance - https://www.parts-express.com/peerless-by-tymphany-xxls-p830845-12-nomex-cone-subwoofer-8-ohm--264-1646

 

[Fatmarley]

I don't know if your plate amp would handle a 4ohm load. The 8ohm Dayton RSS315HFA would be a safer bet, but slightly quieter with 150w (106db 1mtr). But will take up to 400w in a smaller enclosure. It's very unfussy about sealed enclosure size, and cheaper than the others too. 

https://www.parts-express.com/dayton-audio-rss315hfa-8-12-reference-hf-subwoofer-8-ohm--295-445

 

[JazzyG]

FatMarley,

I think you are looking at the wrong column on the spec sheet, my sub is the BPS150, far right column, and it uses (2) 8" drivers.  The other driver is on the opposite side as the one you see in the picture.  This sub is ported, one port on the one side and 2 on the other.

I was looking at some of the same brands you recommended,  such as Dayton, as I really like the woofer in the DIY Classix II speakers I built.

 https://www.daytonaudio.com/product/37/dcs205-4-8-classic-subwoofer-4-ohm

https://www.daytonaudio.com/product/117/rss210hf-4-8-reference-hf-subwoofer-4-ohm

With 2 drivers,  maybe I should open the cabinet up this evening and see if they are wired in series, perhaps 4 ohms would make sense then?  If I  measure resistance across the terminals that is roughly correct impedance, right?

Thank you! 

 

[Fatmarley]

Hi JazzyG, I was looking at the right column. When you said DIY, I just assumed you wouldn't mind cutting out the baffle and fitting a new one, with a bigger driver (bigger is always better). The one on the opposite side could also be removed and a new baffle fitted.

I'd remove the plate amp and find where the woofers are connected. I'd then measure the resistance at that point. For all you know, the woofers are 16ohm, wired in parallel to give 8ohm. They are most likely 8ohm wired in parallel, but it's worth checking.

 

[Bram49]

Hi guys! Just wondering if you had noticed my ad for 4 10 inch Peerless Tympany drivers in the Classifieds?

 

[MF 1000]

Hi guys! Just wondering if you had noticed my ad for 4 10 inch Peerless Tympany drivers in the Classifieds?

I think postage to the USA might be excessive .....

 

[Fatmarley]

Hi guys! Just wondering if you had noticed my ad for 4 10 inch Peerless Tympany drivers in the Classifieds?

A great subwoofer for a very small, sealed enclosure. If my simulations are correct, it looks like the Peerless 830452 would well work in a tiny 15ltr, sealed box. With my room gain added, it would give a flat response down to 20hz, and would reach xmax with 250w at 105db (that's with room gain though).

With 4 x 830452 in series/parallel in a 61ltr sealed enclosure, xmax would be reached with 1000w at 117db 2.83v 1mtr (with room gain again).

 

[JazzyG]

 I opened up the cabinet this evening, looks like the amp is partitioned off from the rest of the cabinet.  The drivers appear to be wired in parallel, I got an impedance reading of ~4.4 Ohms which would indicate the drivers are of the 8 Ohm variety.  It is always amazing how little there actually is in some of these cabinets as far as components.

Based on the new info, which 8" drivers would you recommend if I leave it ported?

I went to Parts Express and searched on subwoofer drivers, 8", 8 Ohm, and only 4 choices popped up.  Maybe the Peerless by Tymphany 830667 8" Paper Cone SLS Subwoofer?  The Dayton one is really inefficient, the Tang Band appears to be specialized for specific applications, the Peerless by Tymphany NE225W-08 8" looks nice, more money though and is it that much better than the 830667?

 

[Fatmarley]

I could model the drivers for you but as I said previously, I'd need to know the exact internal volume and the port dimensions. 

When I wanted to find out the internal volume of an odd shaped cabinet, I filled it with cat litter (wood chip stuff) and emptied into a builders bucket that had litre measurements on the inside.

 

[JazzyG]

I measured the inside of the cabinet this evening.  I calculated the volume in cubic feet, I took the volume of the 3 ports out of the total.

A total of (3) ports that are 2" i.d. and 11" long.  2 ports on one baffle and 1 port on the other.

1.61 ft^3

I did not take anything off of the total volume for the drivers, was having a difficult time coming up with a figure for that.  I inspected the drivers when I removed one of them, they are nothing to write home about.  The old drivers weight 3lbs, 2 oz and the foam is close to coming apart on the surrounds.  I also found the skeleton of a rodent of some sort in the cabinet, I did not take the volume of that into account as I removed it!  

Do you think the Tymphany SLS-P830667 would work?

Thank you!

 

[Fatmarley]

With 2 x 830667 in parallel the impedance drops to 3.15ohm in places. Don't know if that would cause problems with your amp? Could you measure the resistance of a single driver?

This is the model, but with no room gain or filters. Grey line is the sealed response, ported is the black line (150w input). Excursion at 20hz is 22mm with the ported, Sealed is at the 8.4 limit. I'll upload a graph later if you're interested.

The dark grey line is with room gain (modelled from my room though) and a 60hz 2nd order low pass filter.

Here's just the sealed with room gain and a low pass filter (150w)