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I'll just mention that these speakers are nothing like the vintageARs they're vented after all, could anything be more un-AR?This is an old friend from many years ago who I'd not spoken to in along time, he upgraded his system after hearing mine, he was due forit anyway I suppose.He's not an audiophile and not obsessed with Audio. I asked him if Icould offer his comments here about how weak they were in the bass,and he said 'what you should say is that there's no deep bass WHAT SOEVER'. He said I even tried an EQ and could not get low bass out ofthem. He said 'my AR-15s have better bass and they're much smaller,I never liked the AR310HOs from the day I brought them home.' We A/Bed them to my reference system and he said in normal languagethat the instruments sound all mixed together.
I'd call it veiled ora lack of transparency in audio speak. I found them to sound boxy,and to have a shouty cupped hands quality, and no deep bass. Theyalso seem to lack high end extension above 12 kHz. They do seem tohave good driver integration and a smooth but colored soundin my opinion. I was expecting the lack of bass since I had read thereview of the 312HO in Audio and seen the FR curve.
Also noticedthat there is damping in the port which is usually not recommended.He asked if we could fix them, I said probably but that I wanted tolook into it first. I suggested selling them as is, but he wants tomodify them.I decided to see what I could do while I had them in the system andhere's an external mod that we both found to be a significantimprovement:1. Remove the biwire input strap on the + terminals.2.
Put a 20 ohm 10W resistor across the HI range terminals.3. Put a 4 ohm 20W resistor from the woofer + to the HI range +.4.
Put a 10 uF poly or mylar cap from the woofer + to the HI range +.5. Wire the Amp to the Woofer input terminals.He came to listen today and was impressed with the improvement,listened carefully, saying this is not subtle, it is a significantimprovement.Now he's interested in substituting a better woofer. There's enoughbox volume to use the standard AR 11/12', however I've found a 12'woofer that should work well in a vented configuration. I willredo/modify the crossover as needed to work with the new woofer.I'm interested in listening impressions from people who might beinterested in trying this minor mod. AR claimed 97 dB/2.83V/1m for these speakers and given the relatively typical box volume used I thought they must not have deep bass, or they will not make the efficiency rating. You cannot beat the bandwidth/volume/efficiency tradeoff as predicted by Thiele and Small theory.
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Sure enough the frequency response curve shows that the system produces an average of about 94 dB from about 150 Hz to 9 kHz. It is possible to make relatively efficient midranges and tweeters.
The response steps down to an average of about 89 dB from about 120 Hz to 80 Hz, and it is down a significant 14 dB at 40 Hz and about 7 dB at 50 Hz. An interesting comparison is to the Large Advent which is down about 1 dB in thelow 40s, ignoring baffle step losses.It is clear that the woofer is fairly typical with a sensitivity of about 89 dB in the passband. The modification that I've suggested pads the mid/tweeter section down by about 6 dB and since the problem is differing efficiencies, it should provide a good correction from the start of the woofer passband at 80 Hz on up into the tweeter range.There is a 5 dB dip in the frequency response at about 12 kHz which probably explains the lack of air. Keele also notes that the left system was down 5.5 dB at 10.6 k compared to the right and -4dB at 18.1 kHz. I wonder if there is a consistency problem with these tweeters.The vent seems to be tuned to 30 Hz and there is a layer of fabric in the port to lower the Q. This is generally considered to be a bad idea, and indeed Keele noted that the fabric added significant distortion flapping, with high output in the deep bass.Keele notes that the woofer is robust and handles a lot of power without a problem. I also found them to handle significant power without strain.I expect that the 310HO will be even worse as far as deep bass goes having a 10' woofer.
I plan to measure and simulate, when I have the time. I’ve come across topic and I’m keen to try these mods on my AR 310 HO speakers as I was looking to improve the bass response.As outlined in the tread I’ve noticed that there is a definite lack of bass especially at low volume level. As the volume levels increase the bass response lifts but I’ve always felt that it lagged the level required to match the tweeters and mids.I was wondering if I can have some guidance before I implement the mods as I’m keen to avoid damaging my gear from getting the instructions or components wrong.Would the following parts be suitable:- 20 ohm 10W resistorWould a wire-wound or metal-oxide film resistor be suitable and what is the recommended VDC capacity.I’ve noticed that 18 ohm or 22 ohm audio grade resistors are more readily available. Would these be ok to substitute with these on should one use two resistors in series or parallel to achieve the required resistance or as close a possible.Would this resister be suitableDayton Audio DNR-20 20 Ohm 10W Precision Audio Grade Resistor- 4 ohm 20W resistorWould a wire-wound cement resistor be suitable and what is the recommended VDC capacity.- 10 uF poly or mylar capWould the following cap be suitable or any other recommendationDayton Audio dmpc -10 10uF 250VDC Polypropylene Capacitor High Current capacity.Finally I’m just a little unsure on a couple of connection details. I’ve indicated below where I’m seeking some clarification.Procedure:1.
Remove the biwire input strap on the + terminals.2. Put a 20 ohm 10W resistor across the HI range terminals.
Across the + ve & -ve terminal of the Hi range terminals.3. Put a 4 ohm 20W resistor from the woofer + to the HI range +.4. Put a 10 uF poly or mylar cap from the woofer + to the HI range +. Is the Cap in parallel with the 4 ohm 20W resistor or in series.5. Wire the Amp to the Woofer input terminals.Assistance would be greatly appreciated.ThanksAdrian T. We discuss the EV Interface line of speakers here that all employ a line level boost high pass filter; I'm Pete Basel there:Pioneering work by EV as published in the AES:'A loudspeaker system of only 0.025 m/3 internal volume capable of radiating an acoustic power in excess of 1/16 W at 32.7 Hz in pairs is described.
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Each complete system consists of the loudspeaker in its enclosure together with a complementary filter of the type described by Thiele as his alignment 15. Unusual features include a vent substitute appreciably larger than the main radiator.' Author: Newman, Raymond J.Affiliation: Electro-Voice, Inc., Buchanan, MIJAES Volume 21 Issue 6 pp. 450-456; August 1973. Finally implemented the suggested improvements (thank Pete) and wow what an impact. I’ve made the mod easily removable so that I’ve been able to compare between std & modded speakers.As previously stated, I had noticed that there is a definite lack of bass especially at low volume level and as the volume levels increase the bass response lifts but it lagged the level required to match the tweeters and mids. With mod the bass response has come alive.Where previously the 10” woofer was a lazy freeloader making little contribution and now it's earning its keep.
The bass is now evident where once it was missing, drums and bass guitar feature prominently vocals & lead guitar are somewhat dampened. I’m pleased with the improvement and heartened with the fact that there is some real scope to get the most out of the 310HO however I feel that the pendulum has overshot the mark by say 20% over the ideal balanced point which suits my ear.What scope is there to “tune” the mod.
Is there some scope to say adjust the resistor or capacitor to soften the bass response a touch and or raise the tweeter and to a lesser extent the mids. I would love to get an explanation of how the mod was designed and what would be the effect of changing the rating of the components.AdrianT. Just wanted to mention that we simply twisted the component leads and then slippedthem under the binding posts.I selected the component values based on the input impedance curve published in Audiomagazine when Don Keele reviewed the HO312. The 4 ohm is the only important value,reduce it to 3.5 or 3 for less of an effect. The cap boosts the high end since Keele foundit to be 5 dB down, you can try it without the cap for another variable, and/or reduce it asneeded say between 8 and 4.7 uF.I don't remember if I measured the input impedance but I'll look for the file on my measurementcomputer since it would be very easy to simulate the mod to produce a frequency response plot.
Hi Pete.Thanks for the reply, I greatly appreciate your assistance. So that I understand the components effect.1. The 4ohm resistor controls the bass loudness / response.
Reduction in resistance will reduce the bass loudness / response and increase the resistance will increase the bass loudness / response.I’m looking to try 3.5, 3.75 & 4.6 ohm resistors. So I can soften the bass response2. The 10uF cap boosts the high end.I’m looking to try 8.2uF and 12uF cap. A higher cap figure higher then 10uF wouldn’t be detrimental to the speakers? Perhaps 15uF3.
What is the function to the 20 ohm resistor across the HIGH range terminals and what effect would varying this resistor make?Once again thanks for your assistance in advance.AdrianT.
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