Speaker Question

I've used this before, but not recently:

https://www.physical-lab.com/index.php/de/products/linearx/cae-software/leap

Or, maybe one of these speaker box design software free

It's fun to play around and tweak the response.

Maybe you should read up a little first eh?

If you're going to want stereo in this configuration you'll need 4 speakers...

http://en.wikipedia.org/wiki/Isobaric_loudspeaker

Well from what I can gather, the enclosure size should be half what one speaker would use....so in the clamshell design, one side being open, the other end being sealed and half the size that would normally be used with just the one speaker....

Not always.

In 1991, I drove a Ford Taurus for 6 months with a straight through exhaust system, with loudspeakers at the pipe outlet for sound cancellation. And crankshaft sensor, mics and a DSP control system. This was one of the designs we tried. We tried almost every design there was and some of our own.

Once put a giant version of this system on an M-60 Tank and played around with it at Edwards AFB desert test track. That was fun.

Looking at the speaker you chose none of the question viable(Optimal HiFi audio reproduction). As the speaker needs to be matched. These replacement speaker you chose are not. Not sure of the seal on the paper cone to create the isobaric chamber. You need to do more research.

Since the speakers both have the same Thiele-Small parameters, they are matched, to each other.

All cones are sealed as any leakage would cripple the speaker.

If I understand your first sentence, that's the purpose of the speaker enclosure. To tune the response curve of the speakers to the desired levels.

There's a lot to building a proper enclosure. They can make a cheap speaker sound good or a $1,000.00 Klipsh sound like a piece of crap.

OP is on the right track.

So I think we would have to know the characteristics of the amplification system, and the enclosure design is likely to be subjective in nature....this is probably for a car or mobile system...

NO! Forget I ever mentioned active noise cancellation.

Speaker tuning is independent (mostly) of the amplifier, unless your trying to make up for response deficiencies in the amp.

My advice would be to tune the enclosure to the response you want. Then work on the amp.

Well then I would make the design clamshell with 10" of space behind the magnet face of each speaker, sealed on both ends with 4" holes all around the tube on both ends, then have a sliding damper that I could block as much of the holes as I wanted...

It's just not that simple. No way. You cannot tune an enclosure by eyeball.

If you've never done it, you have no idea of the incredible interactions between different Thiele-Small parameters, enclosure dimensions and materials and REAL frequency response of an enclosure. As I said earlier, the enclosure makes, or breaks, the loudspeaker.

A tiny difference in one parameter can make an incredible difference in performance.

That's why, to do it right, you have to characterize the speakers in hand, not use the published numbers.

AH can elaborate.

Hence the sliding sleeves....this design allows for tuning by ear, not eye...anyway AH is on the job, so I will defer to his expertise....

Tuning by "ear" is really the worst way do do it. As Lyn mentioned, there are too many factors to simply be "turning" dials.

Lyn did not mention that testing is another issue altogether. The lower in frequency you go the more you have issues with room interactions.

Ideally, you need to test the loudspeaker in a very quiet open air environment suspended above ground and all other neighboring obstructions at least one wavelength below the lowest desired testing point.

That is pretty much impossible, so you end up making all kinds of compromises to get an approximation of the true frequency response.

This 21" driver is designed for base, so it is going to be really hard to evaluate the performance scientifically, which makes accurate modeling all the more valuable.

Is that supposed to be the "wife" in the back seat?

Have you tried the trunk?

Why do you ask? Is she missing? ...........................

Please turn off the caps lock.

First, I am game, if I can get LEAP 5 to work on my new OS. Working with LinearX to resolve that now.

However, I need more information for your design:

1. Is the tube closed or open? I am assuming that the drivers are mounted face-to-face at one end, but what about the other end? Is it sealed, ported, or open (i.e., transmission line)?

2. Do you have the actual T/S parameters for these drivers? You will need to measure them yourself as the published specs are often not right.

If not, I will use the published parameters, but bear in mind that the theoretical results may not actually match the real performance.

3. What is the desired frequency range of operation?

Whaddaya mean the T-S parameters won't match?

They match the speaker/s that were tested to arrive at the published numbers. ;>).

I think OP is just starting out and my not have much equipment to work with.

OP, you are in good hands with Anonymous Hero. He is an expert acoustician and scientist. You can rely on whatever he tells you as expert advice.

Good luck.

Thanks, Lyn (evil grin... greedily rubbing hands together...). :-)

Welcome.

I think you'll enjoy tutoring the OP/AP.

I wish I had time to play around with enclosure design again. It was a lot of fun if you had the right tools, which we did.

Yeah. I spent more money on software tools than the actual cost of the drivers and materials to build my last set of speakers.

Those were two pairs of Acoustic Elegance 15" woofers mated to a pair of Beyma TPL-150 ribbon tweeters. The enclosures are ported and made from two layers of 3/4" baltic birch plywood with a constrained elastic layer between the two layers of plywood. Tricky build.

Estimated materials cost was about $2,000 - $2,500.

Wow! That sounds nice, I'll bet.

That's a lot of work, never mind the money.

And the tools you'll always have.

I met some very interesting people working on noise cancellation in the early '90s.

Speaking of noise cancellation, I remember flying out on a commercial jet with a colleague who was bragging about just buying noise canceling headphone for the upcoming trip.

We boarded the plane and his seat was behind me. In flight he put on the headphones and a short time later he began to start singing - presumably with whatever he was listening to on his noise canceling headphones.

Needless to say, he could not hear himself at all and he was totally out of tune, it was awful! Dying cats were more musically interesting than what was coming out of his mouth.

People all around him were making faces, but he was totally oblivious.

Finally, I turned around and yelled, "Ted! Ted!! Are those your noise canceling headphones?"

He slid them off and said, "Yes!"

I shouted back, "They are not working!"

People all around him started laughing as Ted had this totally puzzled look on his face - priceless.

I'll put on my marketing hat now.

First, I'll bet most of the pilots who fly powered aircraft wear David Clark's with active noise cancellation. Or Bose. Or, Sennheiser. Check out Sporty's.

I used David Clark's with my scanner when I used to go to the races. (as a spectator) The mic. made me look goofy, but I didn't care.

And, I'll attest to the fact that active headsets do indeed enhance the sound quality of music. They remove much of the external, repetitive noise that can add interference to the basic sound of the music. It's like listening to music in a quiet room.

Hat off, they do help. Even a cheap set is useful.

I just noticed another parameter that leads me to believe that the isobaric configuration may not be a good match for these drivers...

Xmax is only .275", which is too small for ported and open baffle configurations.

The QTS is also on the high side for a ported enclosure and the low side for a sealed enclosure.

However, my gut says that the small Xmax pushes this design towards a sealed enclosure and it really depends on the intended use. Are you stuffing these into a car or is this a home audio project. I would definitely not use these for a stage, you will tear them up in minutes despite the alleged Wattage rating, which is only the rating for the voice coil thermal capabilities, not the actual performance.

I will try some models when I get more time and working software.

You will need to carefully calculate it based on the speakers you plan to use. If you get it wrong you will make the speakers sound worse.

I left my speaker design book at home, but there is a far amount of free info online. Try an internet search of "ISOBARIC SPEAKER CYLINDER design"

OK here's a rough concept of my design....a funnel cone sits centered, flush with end of tube on the exterior and is inserted into an internally mounted ring, (both ends the same)....the tube 24" in diameter, the funnel 16" in diameter by 8" deep to a point, the ring 12" by 24" with a 12" hole...the ring is mounted 6" from the end of tube internally... the ring is mounted 6" from the speaker back...the overall length of the tube 24" plus speaker profile x2....should be under 4 ft....