Tower ar.com's again......

[kevyjo]

Hello, this is my first post in this forum. I've been an audio hobbyist for awhile and built my own subwoofer that I'm still very very pleased with. I've become intrigued with the ar.com's. I'm very happy with my main speakers, Signet 280 BL's, and after all of these years I'm still impressed with their balance between being both forgiving and revealing, easy impedence load and relative efficiency. Signet also had the 260's, and came out with the floorstanding 280ex after I bought mine. The only problem with the 280 BL's is that they are pretty ugly. I've always wanted some elegant slender 2-way floorstanders (something like the proac studio 125's) as a DIY project. I've read Ed's post about the ar's loosing some of their "midrange magic" when placed in a larger enclosure, and I was just wondering if someone could expand on this. One thing i've liked about my speakers is the fact that they are tuned to a frequency lower than "optimal", giving a deep but slighly rolled off bass, and sounding somewhat drier in the midrange than the 260's. Could such an effect be achieved with the ar.coms? I was looking at around a 35 liter enclosure and a port tuned at 34hz

[kexodusc]

There's a lot at play as you increase the volume. You're changing the baffle size, and that's going to affect baffle step and diffraction at least somewhat (though probably not much if width is preserved). But you will change the overall tonality of the design as you change the slope (and could affect power handling a bit as well which could impact the midrange if you start to run out of excursion).

A few people have made the Ar.com's into towers, but preserving the internal volumes by building a dummy chamber underneath the ar.com (and filling it with sand, polyfill or something to absorb resonances) with good success.

[kevyjo]

The peerless driver has a healthy xmax, I wonder what enclosure/port tuning would effect it's power handling. As I understand it, the driver is protected somewhat at the tuning frequency. I might just build the enclosures I'm envisioning as an expiriment and see how it works. I would not be so tempted if I had not already heard large enclosure 2-ways that I really liked the sound.

[kexodusc]

Yes, the driver excursion is at minimum at the tuning frequency, but there's a hump before and a large, fast spike after. At moderate spl levels I don't think it'd matter much, but you eat up excursion pretty fast as you turn the volume up...when I get time later I'll model the 850122 in 35 litre box.

[kexodusc]

Well the driver can certainly be used in a larger box without too much power handling worries...I checked excursion and you'll still have plenty unless you drive these things above 90 dB quite a bit.

One thing I would recommend is measuring the response of your drivers if you have them and have the means to measure your drivers...the Peerless specs on fs for the driver are wrong...it's closer to 50Hz than 38Hz...this changed a few years back when production shifted and the HDS line of woofers was introduced.

The slope of the bass response starts to drop down as high as 200 Hz when I modelled your box, only by a dB or so, but it continues to drop 2.5 dB down at 100Hz...over such a wide band it will change the tonality of these speakers a bit. I can't say for better or worse because I don't know. But it sounds like an interesting project, good luck.

[kevyjo]

Thank you for the information about the Fs, I had no idea. The 820122 was in my driver database in winisd, but was obviously the old specifications.....Hey I just modeled it with an Fs of 50hz, but what i dont understand is that if that is true, the ar.com kit should be -3db at 67hz, that does not seem consistent with the bass that is described from the kit. Now im really confused...

[kexodusc]

67 Hz? Not sure how you're getting that, could it be a setting in WinISD?

Hmmm, I modeled a -3dB at about 55Hz in open space in the 10.5L enclosure. With average room gain though it's really a lot lower, 42 Hz or so. I can measure around 44 Hz in my large room, 2 feet from walls. As you add polyfill, you have the effect of increasing the cabinet volume the woofer "sees" so bass increases a bit...these numbers are give and take a few Hz. But certainly 60 Hz and above is too high.

I've measured 4 of the 850122's, I get anywhere from 44-51 Hz. I chose to use 50 Hz after talking with some others, it's on the conservative side. I use them with a subwoofer anyway so it wasn't a big deal to me. Plus, Parts Express' measurements on that woofer were around 50 Hz too...I trust their methods a bit more than mine.

what are you using for T/S parameters?

[kevyjo]

I think the T/S parameters are the same in winisd, and at parts express and madisound, ill have to double check later. My original enclosure showed as ruler flat to like 33.5hz but that was at 38hz fs. I do have my phenomenal home built sub, but it's almost a "sub sub", covering 15-40hz, but that blends seemlessly with my Signets which roll off slightly below about 70hz I'd say but have strong output down into the mid 30's.

[kevyjo]

Oh ok, I found the "real" T/S parameters. I was confused because partsexpress has both the new and the old ones.

[jocko_nc]

Some of this sounds familiar, I went down a similar path recently. I looked at the AR kits, but wanted to do something more. I got advice from some good guys and learned a lot. Here is a brief description of my project...

Phase I: Seas 27TDFC. Good tweeter with a low crossover. No brainer choice. Peerless HDS in 6.5 inch. Accurate midbass with good highs. From what I have seen now, a wonderful driver. Fantastic mids and at 6.5 inches, it can really crank them out. I got the crossovers correct on the second attempt. Cabinet was old-school, but ideal dimensions for 6.5 two-way monitors. What I was left with was a tremendously detailed monitor. Highs, mids, and low mids were simply great. However, I needed some bass. Good, deep, clean bass.

Phase II. I thought to add a DIYsub. Rather, I wanted two DIY subs, in stereo, crossed over at 80 Hz or so where the Peerless HDS rolls off. I did not care about maximum SPL or the lowest possible note I could blast. I wanted kick*ss bass that matched the drivers in Phase I. I wanted bass that made the Vandersteen IICe's sound sloppy and hollow. In that regard, I was trying to make a three-way out of my monitors by adding another driver. PartsExpress did not recommend the Titanic driver at all. I figured as much. They recommended the Reference Series in HiFi confiugration and they were right on. Man, that is a great driver.

I have one sub finished in protytype stage. Playing my best low-end recordings Telarc "Carmen" and "Per Gynt" I cannot believe how lame the Vandersteen woofers sound. (They always had a good low end) Not talking the volume or the BOOM, rather the detailing and the timbre. I have a bunch of actual kettle and bass drums in my living room now. I swear it, between the HDS and the Reference sub, I hear the impact on the head and the metallic rumble of the kettle. I can pick out dissonance at the end (Hall of Mountain King) when the bass drum is really clobbered. A dual wave comes off the head, you can hear it.

I ramble on about this... Sorry. I was that impressed. If I were going to make a "tower" or something else from a monitor, I would look into using the Dayton Reference HiFi. Very, very musical yet powerful. I wish you guys could hear it.

jocko

[kexodusc]

Sounds like your having fun. The 27TDFC is arguably the best bang/buck tweeter out there right now...I bought a $90 Scan-Speak that only performs a bit better, wish I would have saved myself the money now in hindsight (though, I think diminishing returns apply in DIY audio too, gotta spend a lot to get a bit more).
My next project is going to be a Dayton Reference or Seas Aluminum project. Shipping costs will determine which way I go since they're so close.
Then I'm going to tackle a T-line....