FAQ — Frequently Asked Questions

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  Getting Started: product selection, hookup, and placement

What size subwoofer do I need?

You cannot have too much subwoofer. A bigger subwoofer (from the same manufacturer) will always play lower, has lower distortion, more headroom, and better long term reliability if played at the same listening level. Hence, if budget is not an issue, going for the larger sub will always be beneficial, if there is no WAF or physical limitations.

We have suggested room sizes that each subwoofer is recommended for. This of course is a very rough guide. Very much depends on individual tastes. We have customers who find four VTF-15H in a 1,000 cu.ft. room is not enough. We also have customers who are happy with a STF-1 in a 5,000 cu.ft. room. Hence we suggest going with the biggest subwoofer that your budget, spouse and space allows.

We frequently get questions 'is this subwoofer too powerful or too loud for my room?' The answer is no. The subwoofer need only play as loudly as you set it. You can even turn it down till it has not contribution. You can set it anywhere between that and 'too loud'. The larger subwoofer would sound more effortless and 'airy' due to lower distortion and higher headroom. All else equal, the bigger sub will also be more reliable as it has to work less hard for the same listening level.

How do your products compare with others?

What distinguishes HSU from the rest is that we are an engineering driven company. This is reflected in the quality of our products.

It is common for other companies to focus on cosmetics and marketing gimmicks. They follow the marketing adage to "sell the sizzle, not the steak". HSU is different. We focus on pure audio engineering and on building a better mousetrap. We obsessively concentrate on product performance and reliability. Each HSU product is carefully engineered by Dr. Hsu to provide "high-end" sound in its specified room type. High-end means the best of the best. We hope you will agree.

Attention to customers is another differentiator. Dr. Hsu, founder of HSU, consults privately with customers on a daily basis. This demonstrates his commitment to product quality and home integration. There are few companies who can make that claim.

Of course, cosmetics are also important. Afterall, the subwoofer also have to meet the spouse's approval. Hsu Research recognizes this and does not skimp on this either.

What is the best place to put a subwoofer?

A good place to start is a front corner furthest from openings. This is generally great for deep bass. If you like a lot of 'hit in the chest' mid bass punch, placing the subwoofer close to you is best (preferably directly behind).

If you have a means of measuring, and is willing to experiment, the subwoofer crawl is the best to find the optimal location for the subwoofer. You place the subwoofer in your listening chair and measure the frequency response at the various locations where you can place the subwoofer. The position that gives the best response is where you put the subwoofer.

Note that where you sit is equally important. If possible avoid sitting in the middle of the room as this is where bass is usually weakest.

What is a subwoofer?
A subwoofer is a specialized speaker responsible for the most difficult duty in home theater. It produces the very deep, room shaking notes that add a magical effect and balance the sound. This requires providing lots of power to fill a room with sound, and large mechanical motions of the subwoofer. When you hear about Dolby 5.1, the ".1" refers to the subwoofer's special role in a surround sound system consisting of five speakers and (at least) one subwoofer.

What are the differences between the STF and the VTF subwoofers?
Variable tuning allows you to choose how deep your subwoofer plays, on-demand. Choose between a music mode (lower bass extension) or a home theater mode (higher headroom and more impact) in just a few seconds. Subwoofer designs involve tradeoffs – one cannot optimally design a subwoofer to play low deep notes, and at the same time play loud. Usually the designer chooses a tradeoff for you. With the VTF series, we build in flexibility so that the listener has uncompromising control.
  • STF – Single Tuning Frequency. The bass characteristics are fixed.
  • VTF – Variable Tuning Frequency. The bass characteristics can be varied between lower extension (one port open), higher headroom (2 ports open), or sealed mode. We also give you a Q control to adjust the bass tightness. This series gives you more flexibility than any other subwoofer we know. This is equivalent of buying multiple subwoofers for the price of one. Irrespective of your preference or room, you can get the VTF subwoofer to sound right.

Should I use the Auto EQ in my receiver?
Generally the auto EQ in receivers are getting better and better, and it's usually beneficial to use them. One general guideline for using the auto EQ for the subwoofer - set the subwoofer for the lowest extension and flattest response so the EQ compensates for the room acoustics alone. e.g. with our VTF series subwoofer, set the subwoofer to one port open, EQ1, and Q=0.7. This is the flattest response mode. The EQ will then correct for the room effects. After EQ, you can select other operating modes for the subwoofer - two ports open, EQ2, Q=0.3, etc.

How close can I put the subwoofer to my television?
Unless you are still using a CRT television, you don't have to worry about placing the subwoofer close to your TV. None of the newer technology TVs are sensitive to magnetic fields.

Can I connect your subwoofers to my computer or computer speakers?
It is relatively easy to connect a HSU subwoofer to certain computer sound cards. These sound cards have a dedicated subwoofer output. Without a subwoofer output on the card, it is still possible to hook up a VTF or ULS subwoofer, since these subwoofers have stereo inputs. Use a splitter/adapter (one 1/8-inch stereo male to two 1/8-inch stereo female). Take the stereo 1/8-inch output from the computer sound card. Then feed one set to the computer speakers and another to the subwoofer using an adapter (1/8-inch stereo male to two RCA male). Please be aware that connecting a HSU Research subwoofer to computer speakers (as opposed to computer sound cards) may be impossible.

How do you hook up the subwoofer to a pre-amp?
To hook up a HSU Research subwoofer (any VTF or ULS) to a pre-amp, a stereo pair of RCA cables are to be connected from the pre-amp line-level outputs to the subwoofer line-level inputs. This stereo pair output can be sourced from secondary line-level output jacks or by splitting the line-level output jacks by an (1 RCA male to 2 RCA female) adapter.

What recommendations do you have for receivers?
Most receivers these days should work well. Onkyo and Pioneer receivers are inexpensive and work very well.

How do you change voltage settings?
With the current VTF and ULS series subwoofers, there is a voltage selector switch on the back of the amplifier. Remember to change the fuse when you change the voltage. Use half the current rating when switching to 230V. For STF series and older VTF subwoofers, you need to change jumper positions or perform some soldering in the amplifier. Go to forum.hsuresearch.com/showthread.php?t=773 to see the instructions.

Do I need to use a subwoofer interconnect?
No. A regular mono RCA cable is all you need.

What crossover frequency should I use? I have large main speakers

We generally recommend using 80 Hz crossover even if you have large main speakers. Due to the limited amplifier power of most receivers, using the main speakers to handle some of the bass will reduce the amplifier power available for the mids and highs. Crossing over at 80 Hz gives you the highest possible headroom for your system.

We do not recommend crossing over higher because the subwoofer will be localizable with a higher crossover.

What should I use to clean the cabinet?
You should use a damp soft cloth (micro fiber is great), followed by a dry one. Never use any chemicals.

If I have two or more subwoofers, how should I set them up?

For the highest headroom, you want to make sure they are level matched. Proceed as follows:

Mark a spot on your floor. For each subwoofer you want to level match, you need to position it precisely in the same spot. Make sure all controls are set similarly - crossover out, EQ1 (if it has a EQ control), Q=0.7 (if it has Q control), etc. Place a SPL meter 1 m in front of the subwoofer. Set it to the 80 dB range. C weighting. With just one subwoofer, and receiver's sub out at 0 dB, adjust the level on the subwoofer to get a nice balance. Set all subwoofers to about this level.

Put the first subwoofer in the spot. Set volume to where it sounded good in your system. Play a 50 Hz tone and adjust the volume on your receiver to get a 80 dB reading. If you have two subwoofers to match, lower the volume on the subwoofer to get 75 dB. If you have four subwoofers you want to match, adjust the volume on the sub to get 70 dB.

Move the sub out and place the second sub in the same location. Play the same test tone and adjust the sub's volume control to get the same dB reading. Repeat this for the rest of the subwoofers. Now they are all level matched. Do not touch their volume control again after this or they will not be level matched.

What is the best way to setup the HB-1 MK2s?
The HB-1 MK2s are best toed in so the tweeter axis cross a ft or two in front of you. You get the deepest soundstage and the widest sweet spot. If you use the recommended stands (26- 28" high stands), the speakers are best 19" off the side walls (measured to the center of the woofer dust cap). If this is not practical, don't worry - they will still sound great.

What type of speaker wall mount would you recommend to use with the HB-1 MK2 and HC-1 MK2?

Our customers have used B-Tech BT15 or PPT_AM15B (from btech-usa.com, JR.com) Center Channel Speaker Bracket Mount and B-Tech BT77 UltraGrip Pro Speaker Wall Mounts.

This AM40 side clamping wall mount from bracketsandstands works without requiring any threaded inserts on the HB-1 MK2s
(Note: These products are not endorsed or affiliated with Hsu Research)

Test Tones for Subwoofer Measurements
You can download the test tones on the CDR we provide (if you lost your CD, or if you are outside of the US) here.

  About Us

What is the story behind HSU Research?

HSU Research began as a specialized deep bass research company in 1991.  Dr. Hsu started the business shortly after receiving a PhD in engineering from MIT. He moved to Orange County, California with the dream of making the world’s best subwoofers.

Dr. Hsu started with a subwoofer made of recycled cardboard tube called a sono-tube. It was seven feet tall. The experiment was powerful, and played pristine bass notes deeper than humans can hear, down to 16 Hz. Dr. Hsu called the design a "true subwoofer."

Although air shook all around the room, no harm was done. The volume could be turned down, and the deep notes were strangely captivating. Bass notes were known to exist throughout the ages in church organs and large drums, and they possessed a strong emotional impact on whoever heard them, regardless of personal background, culture, and age. Dr. Hsu's neighbors began visiting to hear the sound.

It was a good review in Stereophile magazine that sparked the first wave of customers. High-end audio enthusiasts read the reviews and were thrilled to save on full spectrum sound. Soon after, the early products sparked a tube subwoofer hobby amongst budget-conscious enthusiasts on the Internet.

Unknown to many, the secret to Dr. Hsu's exotic subwoofers had little to do with their external form, and more to do with what was inside: carefully engineered and matched components. Most engineers did not understand how to properly integrate all the parts in a subwoofer, such as the cabinet, driver, and amplifier. The idea came along in the late 90s of taking Dr. Hsu’s unique synthesis of components, and putting them into a smaller box—with an additional twist. The VTF series was born. Dr. Hsu's variable tuning technology (VTF) allowed for a subwoofer to play either low or loud by building into the cabinet two large, closable openings called ports. The "maximum output" mode became popular among home theater enthusiasts, who could fill large rooms with very loud bass by opening both ports. The "‘maximum extension" mode was preferred by music aficionados who appreciated pure deep bass by opening one port. Once again, imitation was inevitable. Today, the VTF series incorporates even more flexibility, allowing for sealed operating modes and a Q control for adjusting the bass tightness to one's taste.

How do you pronounce 'Hsu'?
Most people pronounce it “sue”. A more correct, more Singaporean pronunciation is “shoe”.

Do you have any dealers?
We experimented with dealers (e.g. CompUSA), but realized that it reduces product value. Middlemen add to costs. Therefore, we now have no dealers and offer products at lower prices.


Do you do demonstrations or auditions?

Yes we do, if you live around Orange County, California. You must call ahead for an appointment during our normal business hours, Monday to Friday, 9:00 AM to 5:00 PM PST.

  Customer Service: ordering, shipping, and returns

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Terms and Conditions for All Sales

The following contains the terms and conditions for all sales through Hsu Research, Inc. These terms are subject to change by Hsu Research, Inc. without notice. It is advised to review the terms before purchasing any product through Hsu Research.


Orders may usually be placed using the Hsu Research website or over the phone with an official Hsu Research representative. We accept credit cards issued by Visa, MasterCard, American Express, and Discover. Gift cards are generally not accepted unless the customer is able to add in their billing address to the card and the card can be properly authenticated. All cards must be issued by a US bank. It is preferred that the order billing address and shipping address be the same, especially for first time customers. However, if the shipping address is different from the billing address, the customer may be subject to further authentication. Hsu Research does accept PayPal for payment. However, when PayPal is used, the order must ship to a PayPal confirmed address. PayPal is not accepted for local pickup. Money orders and checks, issued within the US, are accepted. However, money orders, and checks, will be subjected to longer processing times. Please contact Hsu Research to place your order if using a money order or check.

Orders placed outside of the contiguous United States must be placed over the phone or via email. Due to our inability to authenticate, we cannot accept credit cards for orders placed outside of US and Canada. We may be able to accept PayPal, provided the shipping address is confirmed by PayPal. For orders placed outside the US and Canada, direct wire transfer is typically used for payment. All orders shipped outside the contiguous US will need a quote for shipping. Please contact us at sales@hsuresearch.com so that we may provide you with an official shipping quote. When shipping outside the United States, the customer will be responsible for any customs fees such as taxes and duties.

If in stock, orders normally ship within one business day after the order is placed. It is usual, that the order may ship the same business day if placed before 12:00 PM (PST/PDT). It’s still possible that the order may ship if placed after 12 PM, so if any changes need to be made to your order, Hsu Research will need to be notified by 01:30 PM (PST/PDT) the same day the order ships. If you need to make a change to your order, you will need to contact us via email at sales@hsuresearch.com and/or via phone (714-666-9260).

We do accept local pickups at our Anaheim, CA location and that may be specified under the shipping method when placing the order online. We ask that the customer provide us with the date and time, within normal business hours, for pickup in the comment section. We will send an email to the customer to confirm the pickup time. Generally, we do not allow for anyone other than the billing cardholder to pick up the order.

All prices listed on the Hsu Research website are in United States Dollar. Prices posted on the Hsu website are subject to change without notice.

Sales tax is currently only collected when receiving within California. Note that the product pages do not reflect the sales tax. Any applicable sales tax is displayed during the ordering process after you enter in your shipping and billing information.


Products are normally shipped with low cost, insured, FedEx Ground with signature required to any destination in the lower 48 states. Due to the cost of the item, we do prefer to send with signature required. However, if the customer would rather send the item with no signature required, the customer can request that in the comment section.  

Note that for no signature required:
1) Once the package is delivered, Hsu Research no longer assumes responsibility for the package.
2)  Due to the value of the package, it is ultimately up to the FedEx driver's discretion whether to require a signature or not.

We cannot modify the signature requirement after shipping. If you want to have the signature requirement removed, you would need to inform us, in the comment section, when you place the order.

Depending on the location, many items shipped can be held at a nearby FedEx Print & Ship Center. Please contact sales@hsuresearch.com or check the FedEx website to find the nearest location to you.

Shipping times within the 48 states are typically 1-5 business days depending on the location. Note that shipping and delivery times are estimates only and are not guaranteed. Hsu Research is not responsible if the shipment is delayed. The day your order is shipped, your FedEx tracking number will be emailed. For online orders, we also update your tracking page with the tracking information. If you do not receive it, be sure to check your spam folder, as some emails tend to end up there. If you are unable to locate the tracking number, give us a call or send us an email at sales@hsuresearch.com and we will be happy to provide you with the tracking info.

For orders shipped outside of the contiguous United States, there will be an additional shipping and handling charge. Email sales@hsuresearch.com for a shipping quote.

It is strongly recommended that you inspect the item as soon as it is delivered. If the item has arrived damaged, Hsu Research must be notified within 21 days of receiving the item.


The standard warranty on all subwoofers is 7 years on the driver(s) and 2 years on the electronics. Speakers come with a warranty of 7 years on the drivers. For RMA repairs, whether or not under warranty, the customer is responsible for organizing shipment of the part to Hsu Research. If under warranty, Hsu Research will be responsible for the repair and return shipping cost back to the customer within the 48 states. For international orders, the customer will be responsible for shipping costs both ways as well as any additional customs fees. For more details on warranty coverage, please reference the individual product manual, located on the individual product page.

We only offer an extended electronics warranty for our powered subwoofers.  To add the extended electronics warranty, add the product to the cart. When you view the cart, an option will display on the bottom allowing you to add the electronics warranty to your order. The extended electronics warranty extends the warranty from two years to five years.

30-day Satisfaction Guarantee

If you are not completely satisfied with your purchase, you have 30 days from receiving the item to begin the return process. The customer is responsible for organizing return shipping and ensuring the safe transit of the product(s). We will refund the complete purchase price, minus any shipping charges, after our technicians review the return. The refund happens under four conditions: (1) all items must be in "like new" condition, (2) there must not be any missing items, (3) the product needs to be in transit back to Hsu Research within 30 of delivery (4) you must call us to receive an RMA number. Failure to comply with these conditions may result in the item being refused, or you may be charged a 15% restocking fee. In the event that the item(s) returned arrives damaged, the customer is responsible for filing any claims with their courier. Package Orders: In the event that you receive the unit(s) damaged, a replacement unit(s) will be shipped out at no cost to you. However, if you decide to return the entire package, you will be responsible for all shipping and handling charges both ways for all returned items and the same terms as stated above will apply.

If the shipment is rejected, or if the item is sent back to Hsu Research due to failed delivery, by no fault of Hsu Research, the customer will be responsible for shipping both ways.

Hsu Research reserves the right to modify the 30-day tryout policy without notice.

Contacting us.
Call us, email us, fax us, or use our Feedback Form. Click here for our contact information.

Do you have any b-stock or scratch-n-dent items?
We occasionally do. Please see our Clearance Center for availability.

  Technical questions

Why is there is a humming or buzzing noise coming from my subwoofer?
his is a common question and can usually be solved at home. There are several possible causes:

1) You have a ground loop problem. Try using a cheater plug that removes the third prong, also called the 'ground'. Do NOT ground the grounding tab on the cheater plug! That would defeat the purpose of the cheater plug for this application.

2) You have an amplifier problem. If the ground cheater plug does not help, disconnect all interconnects from the subwoofer amplifier. If still hums, call or email technical support.

3) You have a problem with other equipment. If hum goes away when interconnects are disconnected, hum is coming from the rest of your equipment. Add them back one piece at a time. The one that causes the system to hum is the source of the hum.

How do I contact tech support?
Click here for the ways to contact tech support.