Fusion-15 v2 Info and Assembly Tips Thread

Post will be updated to include more info soon.

If you have questions about your Fusion-15 build feel free ask them here.





Design goals and history:
There were a few reasons for this redesign of the Fusion-15. The original used the SEOS-12 over the B&C 15PS76 while this proved to be a good combo there was a slight mismatch mostly visual between the waveguide and woofer. Without a flatpack for that kit it was never super popular this and Erich had priced it out wrong so he was actually loosing money with every kit sold. Then the B&C woofer was listed as discontinued on the B&C website and we worried about the availability of those woofers.

The SEOS-15 was going to get made up in plastic so we decided to start fresh with that waveguide and look for a good woofer to pair with it. It was about this time that we wanted to try and keep the Fusion designs all using Eminence woofers, this was partially so that the fusion line matches but also due to the ease of availability. Eminence is not terribly far from Erich or PE and they are usually pretty good at keeping up with demand.

The first choice was actually a bass guitar driver the CA154, it was a good driver with a nice frequency response that worked in the smallish enclosure (~3 cuft) that we were trying to shoot for. Downsides were that it was 4 ohm, we wanted to try and keep this design 8 ohm so that it could be easily powered by even low end AVR's without putting them into thermal shut down if they tried cranking the volume for too long. Another issue was that the woofer was too cheap, the total design cost came in right around the Fusion-12, it may have even been less. Erich sent me the 2515 to try and when I got the box I almost thought it was empty, the woofer weighs almost nothing compared to most other 15's. After running some tests I knew this was the woofer to use, frequency response was good, it worked ok in the small ported enclosure but the best part was the surprisingly low distortion. It was lower then the previous B&C and clearly better then the CA154. So the Fusion-15 v2 was born.

The crossover on the v2 is much improved over the original design, the main focus was improving midrange detail and taming the somewhat aggressive top end. Overall I would say it has a much more balanced and detailed sound throughout most of the frequency range. With the larger SEOS-15 the crossover point was lowered to about 1000 Hz, with steeper slopes used on both drivers since it is pushing their safe frequency limits.


My thoughts on enclosure design:
The flat pack for this design which should be available soon is about 2.9cuft and with the included ports tuned to about 40hz. This is about the smallest size I would recommend for a ported enclosure with this woofer. It works well when crossing to subs at 60-80hz and with most using it like that there was no need to make a larger more expensive flat pack. However the 2515 itself can be used full range in a larger enclosure. I feel the most popular size if going with a custom enclosure would be a 4-6 cuft tower design, this would sort of look similar to the JBL M2 or their Synthesis S9900. That should be tuned around 40hz and I would recommend larger flared ports, either two or three 3" ports or a pair of 4" ports in order to keep port velocity and compression under control. A slot port could also be used. Feel free to ask enclosure size/port size&length details if you want to attempt something like that.


Enclosure dampening:
This is an important aspect for most designs, I recommend linings the walls with 2-3" of dampening. I used recycled denim in my enclosure when I designing this one. Be sure to leave the area around the ports open so that air can flow freely in and out of them, constricting air flow through the ports will reduce output around tuning frequency. Here is a photo of how the dampening in my enclosure looked:



Here is an example crossover layout that you can use as a template, on mine I ran all the wiring on the bottom side of the board but there us no need to do that if you do not want to. The wiring and connections can simple be done on the top side where I have the connections traced out.

 

Re: Fusion-15 Assembely Info and Tips Thread

reserved

 

Hi Bryan,

The woofer will work sealed between 2-4cuft (F3 right about 80hz), it could be as simple as cutting the bottom portion with the port holes off the baffle and building a sealed box 15" deep at that height. With an 80hz crossover in the sealed box it should be able to handle 400w without exceeding xmax.

 

Sorry file is quite large >150MB, won't go over email so well. If I get a chance I'll upload it to a file sharing site.

 

You might find the flat pack to be optimal in you situation. The measurement I took was outdoors up on a high stand (4pi), this provides useful resolution above 100-200hz but is not representative of what the rolloff looks like when placed in a room. The slight 50hz dip you see in the measurement is likely some cancelation from a ground reflection.

Indoors (or 2pi) the rolloff is shallower then what the measurement looks like and F3 is about 60hz. I suspect usable frequency response with the flatpack will be down to about 40hz in most rooms though this might not be true of larger spaces.

If true full range performance is required then I recommend building a cabinet from 6-8 cuft using a pair of 4" round ports 5" long to tune the cabinet. This will give solid response into the 30's and at 8cuft perhaps down into the mid-low 20's. This would be about 17.5" wide x 46" high x 18-22" deep, 3/4" construction with double thick front baffle.

It would be possible to use the included baffle for this so that you don't need to cut the driver cutouts yourself, just cut off the bottom of the included baffle that has the openings for the ports and join the remaining baffle to another piece of 3/4" MDF to make up your final baffle height. It may be easier to glue these two pieces together while attaching them to the second inner baffle. Just remember to trace the driver through holes from the included baffle onto the lower baffle and cut with a jig saw before gluing everything together.

From the top of the baffle to the center of the waveguide is roughly 5".

 

This design works well at the current crossover point, both drivers are not pushed beyond what I consider safe or undesirable. Yes the BA750 with it's larger diaphragm would allow for a lower crossover and possibly shallower slopes but there is not a huge advantage to using that compression driver. Also I have not played around with the BA-750 so I can't say how it compares to the DNA-360 in a design like this.

2.83 volt sensitivity is roughly 99dB in the bass range 2pi and around 97-96dB in the midrange/HF after some slight baffle step and to give a some downward tilt to the response.

-3dB points are 60hz and 18k, -6dB roughly 48hz and 19k. The low end response is 2pi outdoors with the stock flat pack, those numbers can be lower in room or if a larger cabinet volume is used.

 

I am not sure if it comes cut or not. Besides the waveguide and CD do not take up very much internal volume, you would be looking at a change of maybe 0.5dB near tuning.

For the most output in that range I would suggest an enclosure volume around 4 to 4.5 cuft with two 4" diameter ports at 3-4" long which puts tuning around 45-50hz. These ports would work: http://www.parts-express.com/speaker-cabinet-port-tube-4-id-x-4-l-flared--260-403 If you really wanted to go all out build it at 4.5 cuft and use 3 of those 4" ports which will put tuning at ~57hz and give a bit of a peak in the response at that range which should give you the midbass chest slam you might be looking for. A pair of those cabinets should approach 130dB in that range.

In the larger lower tuned 8 cuft cabinet you loose between 2-3dB of max output in that range and about 5dB around 55hz, however you are looking at roughly 6-10dB more output from 30-42hz

 

It should be alright but I would recommend some thick damping material be placed across the box somewhere in the midsection to help reduce standing waves in the vertical dimension.

Should not change things too much moving the waveguide from the top of the baffle however I recommend against increasing the distance between the waveguide and woofer. That spacing should always be a close as reasonable to minimize off axis cancelation from different path lengths, the further that are apart the smaller the vertical listening window in which they sum correctly.

I would put a brace every 8-12" in that box.

Here is what the LF response looks like in the 4.5, 6 and 8 cuft boxes with three 4" diameter, 4" long ports for max output between 60-100hz (difference between 4.5 and 4.8 cuft is very small):

Maximum output in those enclosures:


Here are the same enclosure volumes with only two 4" ports (greater extension, smoother rolloff):

Max output:


You could build the enclosure with three ports and plug one with some thick foam at any time to change to the lower tuning, this would allow you to choose the tuning that suits your tastes. I don't think any of those will sound flabby unless you have a huge room mode/peak at 40hz and a large dip in the range of 60-120hz. Note that a pair of speakers will give you roughly 6db more max LF output then the single driver simulations show above.

 

That the maximum excursion limited output of a single driver at the low frequencies, shows how as tuning goes lower you loose some output above tuning.

Here is the stock flat pack enclosure:


All of the directional queues come from the HF driver, so it's best to have that one at ear height, or at least ear height somewhere between the waveguide and woofer. Placing the woofer above the waveguide is not a big deal if following the previous statement.

For standing waves I mean that damping material should be placed across the bracing. You could place it on a brace so that it covers one half of the internal cross-section then on another above/below place damping covering the other half. You don't want any very long areas of the cabinet open/clear. Do this along with normal lining of the the walls with about 1.5-2.5".

Braces should not take up more then roughly 40% of the cross sectional area, you don't want to restrict air flow inside the cabinet.

If two 6" ports were to be used they would need to be 50% longer then the three 4" ports to maintain tuning, so 6" long.

 

You want the cross sectional area of the port to be roughly 32 sq in (inch or two either way does not matter much) and 5" long. So for a 16" internal cabinet width with the slot port the full width it should be 2" high and roughly 5" long. This will tune the cabinet around 36-40hz which will give you maximum extension and smoothness of the rolloff.

 

Actually that picture is of the CA154, the original woofer that was going to be used for this design. If you looks close you can see the surround is slightly different, but they share the same cone and dust cap. It also has a stamped steel frame that was thinner then the cast frame on the 2515. Anyways when Erich redesigned the baffle for the 2515 he made the cast frame flush with the baffle face, not the gasket. The other DIYSG designs that use Eminence woofers are like that as well. If I had a say I would have preferred the gasket flush, I don't care for it sitting proud.

No issues with the offset, that is how the 2515 fit in my test enclosure when I opened up the hole to fit the larger frame. So it was designed with roughly that offset between the drivers. Anyways the 1/8" or so makes little difference at the 1000hz crossover.