Grafyx SP-10 loudspeakers…out of mothballs

OK, I admit it–I got tired of the Boston A-150 “Frankenstein” speakers I had bought for just over $30 on eBay several years ago.  They are quite capable, but I felt like I was missing something.  I hauled the A-150s downstairs and brought up my more recent pair of Grafyx SP-10 speakers.  Here’s what I posted over at the Speakeasy regarding these speakers…

Back in the mid 70s, a small company in Chicago built loudspeakers, with the noble idea to supply audiophile-grade speakers at an affordable price. Had conditions worked out better, Grafyx probably still would have been around today, but they only lasted until about 1984 or so. Back when I shopped for speakers later in the 70s (my first “real” pair), I had parked myself at Absolute Sound (Royal Oak) for a few weekends until I finally made up my mind. At my junior high school price level, the most I could have saved up was under $300/pair. The Grafyx SP-10 was $280/pair, and I was comparing it to the Polk Audio Monitor 7. The Grafyx won, mainly due to its lower bass response. (If I’d had more of a budget, I would have moved up to the Polk Monitor 10 for a fairer comparison.)

Grafyx made three models IIRC: the SP-6, the SP-8 and the SP-10, the model number giving the woofer size. The SP-8 and SP-10 were two-way vented designs, and both used a Philips AD-0162-T8 tweeter. The SP-6 may or may not have been vented, but I recall seeing one in recent years on eBay and it used a cone tweeter. As far as sizes go, the SP-10 was in the same range as the Large Advent. If you notice, the tweeter is mounted on an extension of the front baffle–this makes it flush with the grill surface, and prevents diffraction from the cabinet edges.

I have two pairs of these speakers. The original design from the late 70s (I’m thinking 1978 or 1979), and another pair from 1982 that uses a real walnut veneer finish. The drivers are identical in both–the tweeters were the aforementioned AD-0162-T8, but the woofer is anyone’s guess, as it is unmarked.

One difference I have noticed between the two pairs is that the midrange of the original set is slightly fuller. I also remember that it did not take much to burn out the tweeters in my original pair. I’m thinking the crossover frequency may have been slightly low for the tweeters, and they may have bumped it up slightly in the later models. So, my earlier pair sounds slightly nicer, where the later pair look much nicer. One upgrade I made was to replace the tweeters with the nearly identical AD-1624-T8, which was the same unit except it had ferro-fluid cooling. It has made a difference, as I’m still using those same tweeters. I have also wanted to try the AD-0163-T8, which uses a cloth dome as opposed to a mylar dome. It may tame down a slight edginess I hear from the tweeters.

At the house, I’ve been running a pair of Boston Acoustics A-150 speakers. I bought them for a mere $30 or so on eBay, with rotted foam surrounds. (The shipping cost more than the speakers!) As I had some 10″ foams on hand, they were quickly back up and running. The A-150 was a slightly enhanced version of the A-100, adding a midrange unit.

I admit they’ve sounded fairly good, but the bass response was lacking. I think it’s primarily because it is a sealed-box speaker, as opposed to being vented. The bass always had a congested sound to it. A small factor may be the new foam surrounds, which are not as large as the originals, and may be restricting the woofer’s movement. But, it still did not respond down to the lower octaves. I feel this also restricted the dynamics. I’ve considered making one of those “Vario-vents” for each of these speakers and trying it out. The upper midrange at times could be a bit harsh, which I feel was caused by the hard dome they used on the midrange driver; this I may try taming with some felt to tame it down.

I swapped in the more recent pair of Grafyx speakers today, after not hearing them for a few years. The tweeter has a slight edge to it (as mentioned above), but to me the vented setup just sounds more dynamic, and the bass is much better. I can get usable response down to 32Hz with these, if not a bit lower. I noticed while playing the Genesis Trick Of The Tail album that the soundstage seemed like it was a bit fuller and spread more beyond the sides of the speakers. My “go to” record for soundstage is Joe Jackson”s Body and Soul which will be getting a spin tomorrow evening.

So, these old behemoths are still quite capable after all of these years.  The only tweaks I’d like to make would be to upgrade the internal wiring, replace the rear spring-loaded connectors with proper binding posts, and find some new old stock AD-0163-T8 tweeters to see how they would affect the sound. (Sad thing is, back when they were still available, you could buy these tweeters for $12 each.)

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