Introducing: The Pit Vipers (Ooh Yeah!!!)

[9sheng]

The internal support of the box painted some time ago is always unsatisfactory. Therefore, we have put the internal support in the current situation and revised it in recent days. I upload a picture. I have a question about this. Such a large number of supporting frames will have some impact on the internal volume. Will this have an impact on the overall design? If there is any impact, do you want to increase the depth to make up for the occupation of internal support? You are welcome to make comments and suggestions on this. My idea is that such support will improve the overall strength of the box. I will directly paste the internal support frames with woodworking glue and choose MDF as the box material.

Paul Carmody Carmody hopes to get your opinion, thank you all!





​

[Serenitynow]

Got the grill frames made and powder coated today.

[981CS]

Some companies do indeed play fast and loose with nominal impedance figures (like Wharfedale). However, others tend to be a lot more forthcoming (like Elac with the AJ designs) and list impedance as the lowest value.

I think this design could likely be listed as "4 ohm" nominal. I agree that you'll want to bring some quality watts to the table to drive these, probably even at lower volumes so that you don't miss out on the dynamics that they appear to be capable of.

Appreciate the design though as this genre of speaker isn't represented a lot anymore. These still have appeal to a lot of folks.

[Paul Carmody]

Perhaps I missed it, but what is the actual impedance of the Pit Viper? I've been waiting for a good DIY design like this that I could build and it'd look properly paired with a vintage 70's receiver if executed correctly. However, a lot of us stay away from "modern" speakers (of this design) because we really don't want to push ~3.4ohms with a 40+ year old receiver (looking at you Wharfedale Lintons).


We have those memories of a friend's dad who had a Cerwin-Vega or JBL setup like this that'd slam your chest with bass. We still want that...only with a bit of actual sound-staging and accuracy now.

This is the system impedance of the Pit Vipers. I've written about this before on my site, but to simply boil down a speaker to a single number for its impedance is very misleading, because it varies across the frequency spectrum. I suppose what matters most is the impedance MINIMA (also sometimes the phase angle, but that's a story for another day), which in the case of the Pit Vipers does get down to 4 Ohms at a few places. But in my defense, so do a lot of commercial speakers labeled "8 Ohms nominal."

https://sites.google.com/site/undefinition/diy-speaker-faqs/diy-faqs-driverimpedances

Some sites like Stereophile at least measure the Impedance of their speakers when they do a review of them. And this makes for a good comparison. With that said, I did look up their measurements of the Wharfdale LInton (https://www.stereophile.com/content/...r-measurements), and the Impedance measurement has some similarities to the Pit Vipers. I think theirs might dip a TINY bit lower. But bottom line, a powerful amp with big watts is going to be more fun with these than something with flea wattage. But I did test them with a Lepai 2020, FWIW.

To quote from my page:
It should go without saying, however, that you ought to drive these with an amp with a healthy amount of power, regardless. With 100 Watts, you should be able to get around 108 dB. Technically, the woofer can probably take more; according to the simulations, it should be able to get to 111 dB (@200 Watts) before xmax becomes a problem. You may want to use beefier resistors in the crossover than the standard 10 Watt-rated ones we'd normally use if you plan on driving them this hard for extended periods of time.

[Serenitynow]

Yeah. I remember my mom used it when I was a kid

[djg]

A man my age loves that smell.

[Serenitynow]

That might just work. Of course, the smell is strong until it dries. But, probably worth a try as I do have alot of insulation left over from the bathroom and basement remodel

[djg]

I built the late Jeff Bagby's Continuum design. Certainly a well known DIY speaker. Included in the kit documentation was an interior picture of the original Bagby built solid maple item. The chosen acoustic treatment was eggcrate mattress topper foam, really stuffed in there. I used the much thinner gray pyramid acoustic foam included in the kit. It's a matter of faith in my mind that the late designer greenlighted this material.

[djg]

[djg]

I have a theory that old school hairspray would work on loose fiberglass batts to immobilize the deadly fibers. Just a theory.

[djg]

There's a fire and bug proof recycled denim insulation material a lot of people use. Rock wool also. It's an entire subject of "discussion". The problem with most insulation is just getting the small amount needed. You might have some leftovers from the bath remodel.

I have used suspended ceiling panels of bonded fiberglass. Peel off the surface, cut with an X-Acto knife, no loose insulation. Most people who worry about loose fiberglass in the enclosure worry about fibers being ejected from ports.

"Egg carton" mattress topper foam also another favorite.

I got a box of sawtooth profile one foot square acoustic wall tiles on closeout from PE, used that up.

I most often use WalMart polyester pillow stuffing. I tend to go cheap. You can spend quite a bit on specialized acoustic treatments. As a Psych major in college, I tend to relate personality type to a person's approach to speaker building in general. That's just me.

If you want your speakers to sound like Paul's, build them like Paul's. Unless of course if you're going to worry about his insulation specs.

[marvin]

Nice layout drawing. I like to take one more step to keep me from getting confused. I number all the wires/junction points on the schematic, and then also the junction points where the components meet on the circuit board. Then I can verify that the number of wires soldered at each junction matches the number on the drawing. Just helps me double check my work and prevent confusion.

[Serenitynow]

I would love to see some in depth stuff on the mid range stuffing. IME the stuffing in the midrange box can have a huge impact on it's response.

This is a good question. I really hadn't thought about this before, but I can understand how the amount of stuffing is important to the midrange response.

And speaking of stuffing, if using fiberglass mat on the rear panel of the cabinet ( as Paul mentions ) should the raw fibers be covered with material of some kind to keep them from getting into the woofer ?

[Serenitynow]

Sorry. Double post

[Serenitynow]

I'm pretty new at speaker building so hopefully someone will double-check this.
This is the Tweeter and Woofer on a 3.5 x 5 board and the midrange on a 3.5 x 5 board.
Probably could all be squeezed together on a 5 x 7 board easy enough but keeping track of the wires was a pain for me to figure out.
(Note PE has nice "perforated crossover boards" in 3.5 x 5 and 5 x 7 that look nice, but some 1/8" or 1/4" hardboard or mdf works fine.)

That's exactly the kind of thing I'm looking for !!!
Thank you for posting this picture.
Can someone please confirm its accuracy ?