Silverflute Peerless Two Way Bookshelf Design

[johnny5jz]

I wanted to document my first 100% from scratch speaker build. I have been playing around with building speakers for over 20 years, but have not really done it properly other than building a bunch of kits. I have an electrical engineering background, so I get how a crossover works, but the measuring piece is what worries me. I have also read the Loudspeaker Design Cookbook (multiple times) and Designing, Building, and Testing Your Own Speaker System. I know that your design is only as good as the data you collect, and that is where I will need the most practice. Also, I will need to get a bunch of these under my belt to determine what sounds good and what doesn't based on different design philosophies.

Here is what I started with. I wanted to do something a little different. I know that is not always the best approach for a first design, but I have put together a bunch of kits, and didn't want to redo a common design. This may have been done before (and more than likely has) but it is new to me. I chose the Silverflute W17RC38-08 based on the fact that it modeled well and was reasonably priced. I used my DATS to measure the 2 drivers and designed a box in WINISD based on that. I came up with a .67 cubic foot box which will end up at .64 cubit foot after crossover, port tube and bracing. I tuned it to 39 hz to get a modeled f3 of 42 hz. The interesting part was WINISD calculated a port length of 7.2 inches, but per DATS, I ended up at 6 inches to achieve the 39 hz tuning. I have one window brace in the box, and a 1.5" baffle in order to get the shape I wanted. It is lined with mattress topper at this point and may change.

[johnny5jz]

This is what I have come up with for the crossover so far. I am a little unsure whether or not I have added enough BSC, but I ordered parts for one speaker. I will put together the crossover and see how it measures, and how it sounds. I will adjust from there and then build the second. I am a little nervous how it will measure vs. how it modeled.

[johnny5jz]

I had some trouble with some parts being out of stock, so I did a few mods for the first round of ordered parts. L2 I ended up ordering an Erse Super Q Iron Core inductor. It has a low DCR, so we will see how it sounds. I would have preferred an air core, but the one I wanted was out of stock. I may upgrade later.

[DeZZar]

Nice build. Looks great.

I assume the crossover simulation is based on your actual measurements of the drivers? You should be able to specifically see the amount of baffle step you are dealing with in these measurements.

[johnny5jz]

Yes, it is actually measurements, but in my shop. Lower frequencies may not be accurate. I need to play around with combining near and far field measurements to get more accurate. Sent from my SM-G973U using Tapatalk

[a4eaudio]

...I know that your design is only as good as the data you collect, and that is where I will need the most practice. Also, I will need to get a bunch of these under my belt to determine what sounds good and what doesn't based on different design philosophies.

^Yes.

Also to add to DeZZar's comment...you should describe in detail your measurement setup...microphone, speaker placement and distance of mic from speaker, measurement software, gating, etc. There are some tricky things, like determining z-offset, extracting minimum phase, etc. I know you have already received some feedback in your other threads, but if you lay out exactly what you are doing people will be able to give more detailed feedback...especially if you are making any mistakes.

Looks great so far, I love the faceted cabinet.

[Steve Lee]

This thread is subscribed - keep going and posting, please . . .

[Whitneyville1]

From experience, I don't think the ERSE Super Q is a trade-off anywhere. I've never used a Silver Flute driver, but your sims and measurements look nice to me. If it's possible, a backyard on the top of a 6-8 foot step ladder has always given me very good frequency response measurements (at 3 or 4 in the morning!). BTW, I'm a big ERSE capacitor fan too. I think you have the makings of a very nice design here.

[fpitas]

Nice work! Depending on your budget, you *might* do better with a flared port if you plan to crank some bass. Especially with such a small port that can eliminate "chuffing" and increase the bass output slightly.

[billfitzmaurice]

Going just by the look of it I'd say the port should be larger.

[fpitas]

It could certainly be longer to accommodate a larger ID port.

[fpitas]

A typical flared port: https://www.parts-express.com/Precis...be-Kit-268-350

[johnny5jz]

A 3" port if I remember correctly, would need a 90 in this box. I threw this together with scraps in my shop, and I had 2" pvc laying around. I did run some test tones through the woofer, and I agree, it may need a flared port. I am waiting to get it finished to see how it sounds. I can easily router out the ports and add a flared port. As for my measurements, they were taking with an Omnimic at around 27", halfway between my floor and ceiling at 2 volts. I wasn't sure how high I could go without protecting the tweeter. I just got an old laptop set up in the last couple of days which will allow me to take my measurements outside. I now just need to get my amp out far enough away from the house. I should have my crossover components for one speaker this Friday. I will get it assembled and take a few measurements. I ordered a bunch of resisters on both sides of the sim, so I can tweak as needed. I will post the results this weekend.

[fpitas]

https://www.parts-express.com/Precision-Port-2-Flared-Port-Tube-Kit-268-348

[fpitas]

Bill is right that bigger is better, but good sized flares at both ends still make a big difference.

[Wolf]

I used a 2" port in the "2i" build with the W17RC38-4 in 20 ltrs. I didn't notice the ports chuffing, but they might have at higher levels.

Later,
Wolf

[billfitzmaurice]

A larger port works better than a flared port. The flare eases the turbulence that can occur at the end of the port, but a larger port reduces the port velocity that causes the turbulence. With a 2" port maximum port velocity at xmax with the maximum displacement limited 35w power is only 6m/s, so I wouldn't bother with a larger port or flare. It's just that by looking at the picture to me the port appears smaller than 2" ID.

[johnny5jz]

I got one crossover put together and measured. I need to do final voicing, but am having troubles with only one speaker. I think the measurements are close enough to order the other speaker components. I was not sure how close I would get, so didn't want to order components for both. Below is a pic of my measurement setup and measured waveform compared to calculated.

[billfitzmaurice]

Other than when doing room setup I never measure indoors. I go outdoors and take two measurements. The first is ground plane, to get a half space result below the baffle step. The second is with the speaker on the ground facing up, the mic suspended above it by at least two meters for a half-space result above the baffle step. I then splice the two to get a half-space anechoic result without having to build an anechoic chamber.